As forms of
scienceScience is in its broadest sense to any systematic knowledge-base or prescriptive practice that is capable of resulting in a prediction or predictable type of outcome...
historically developed out of
philosophyPhilosophy is the study of general and fundamental problems concerning matters such as existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing these questions by its critical, generally systematic approach and its reliance on reasoned...
,
physicsPhysics is a natural science; it is the study of matter and its motion through spacetime and all that derives from these, such as energy and force...
(
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
: φύσις
physisPhysis is a Greek theological, philosophical, and scientific term usually translated into English as "nature". In the Odyssey, Homer uses the word once , referring to the intrinsic way of growth of a particular species of plant...
"
natureNature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general...
") was originally referred to as
natural philosophyNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
, a term describing a field of study concerned with "the workings of nature".
Early history
Drawing elements from various areas of exploration including Babylonian Astronomy, early attempts at
opticsOptics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
and
mechanicsMechanics is the branch of physics concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effect of the bodies on their environment....
, and
geometryGeometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers....
, the move towards a rational understanding of nature began at least since the Archaic Period in Greece (650 BC – 480 BC) with the Presocratics. Accordingly,
LeucippusLeucippus or Leukippos was the first Greek to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms — which was elaborated in far greater detail by his pupil and successor, Democritus...
(
Greek:Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
, first half of 5th century BC), refusing to accept various supernatural, religious or mythological explanations for natural
phenomenaA phenomenon is any observable occurrence. In popular usage, a phenomenon often refers to an extraordinary event. In scientific usage, a phenomenon is any event that is observable, however commonplace it might be, even if it requires the use of instrumentation to observe it...
, proclaimed that every event had a natural cause. He went on to develop the theory of
atomismAtomism is a natural philosophy developed by Leucippus and his student Democritus in the fifth century BC. These atomists theorized that the natural world consists of two fundamental and opposite, indivisible bodies - atoms and void...
— the idea that everything is composed entirely of various imperishable, indivisible elements called
atomThe atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s. This was elaborated in great detail by
DemocritusDemocritus was an Ancient Greek philosopher born in Abdera in the north of Greece. He was the most prolific, and ultimately the most influential, of the pre-Socratic philosophers; his atomic theory may be regarded as the culmination of early Greek thought.His exact contributions are difficult to...
.
AristotleAristotle was a Greek philosopher, a student of Plato and teacher of Alexander the Great. He wrote on many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, politics, government, ethics, biology, and zoology.Together with Plato and Socrates , Aristotle is one of...
(384 BC – 322 BC), a student of
PlatoPlato , was a Classical Greek philosopher, mathematician, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world...
, promoted the concept that observation of physical phenomena could ultimately lead to the discovery of the natural laws governing them. He wrote the first work which refers to that line of study as "Physics" (
Aristotle's PhysicsPhysics is an important work by Aristotle. It is a collection of treatises or lessons that deal with the most general principles of moving things, both living and non-living, rather than physical theories or investigations of the particular contents of the universe...
). During the
classical periodClassical Greece was a culture that was highly advanced and which heavily influenced the cultures of Ancient Rome and still has an enduring effect on Western Civilization. Much of modern politics, artistic thought, scientific thought, literature, and philosophy derives from this ancient society...
in Greece (6th, 5th and 4th centuries BC) and in
Hellenistic timesHellenistic civilization represents the zenith of Greek influence in the ancient world from 323 BC to about 146 BC ; note, however that Koine Greek language and Hellenistic philosophy and religion are also indisputably elements of the Roman era till Late Antiquity...
,
natural philosophyNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
slowly developed into an exciting and contentious field of study.
Early in Classical Greece, that the earth is a
sphereA sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...
("round"), was generally known by all, and around 240 BCE,
EratosthenesEratosthenes of Cyrene was a Greek mathematician, elegiac poet, athlete, geographer, and astronomer. He made several discoveries and inventions including a system of latitude and longitude...
(276 BCE - 194 BCE) accurately estimated its circumference. In contrast to Aristotle's geocentric views,
Aristarchus of SamosAristarchus was a Greek astronomer and mathematician, born on the island of Samos, in Greece. He was the first person to present an explicit argument for a heliocentric model of the solar system, placing the Sun, not the Earth, at the center of the known universe...
' onMouseout='HidePop("74205")' href="http://www.absoluteastronomy.com/topics/310_BC">310 BC
-Seleucid Empire:* Antigonus orders Nicanor, one of his generals, to invade Babylonia from the east and his son Demetrius Poliorcetes to attack it from the west. Nicanor assembles a large force but it is surprised and defeated by Seleucus at the river Tigris, and his troops are either cut to pieces...
– ca.
230 BC-Anatolia:* The city of Pergamum is attacked by the Galatians because the leader of Pergamum, Attalus I Soter, has refused to pay them the customary tribute. Attalus crushes his enemy in a battle outside the walls of his city and to mark the success he takes the title of king and the name...
) presented an explicit argument for a
heliocentric modelIn astronomy, heliocentrism is the theory that the Sun is stationary and at the center of the universe. The word came from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center. Discussions on the possibility of heliocentrism date to classical...
of the
solar systemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
, placing the
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
, not the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
, at the centre.
Seleucus of SeleuciaSeleucus of Seleucia was a Hellenistic astronomer and philosopher from the Seleucia region of Mesopotamia who supported the heliocentric theory of planetary motion. Seleucus is known from the writings of Plutarch, Strabo and Aetius...
, a follower of the heliocentric theory of Aristarchus, stated that the Earth rotated around its own axis, which in turn revolved around the Sun. Though the arguments he used were lost,
PlutarchPlutarch, born Plutarchos then, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. AD 46 – 120, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...
stated that Seleucus was the first to prove the heliocentric system through reasoning.
Many contributions were made by many thinkers, including
ArchimedesArchimedes of Syracuse was a Greek mathematician, physicist, engineer, inventor, and astronomer. Although few details of his life are known, he is regarded as one of the leading scientists in classical antiquity...
(c. 287 BC – c. 212 BC) of
"Eureka!"Eureka may refer to* Eureka , a famous exclamation attributed to Archimedes- Canada :* Eureka, Nova Scotia in Canada* Eureka, Nunavut in Canada* Eureka Sound, Nunavut, Canada...
fame, who also defined the concept of the centre of gravity and created the field of statics and
PtolemyClaudius Ptolemaeus , known in English as Ptolemy , was a Roman citizen of Greek ancestry. He was a mathematician, astronomer, geographer, astrologer and a poet of a single epigram in the Greek Anthology. He lived in Egypt under the Roman Empire, and is believed to have been born in the town of...
(Claudius Ptolemaeus (
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
: ) who wrote scientific treatises that were later used as the basis of much later science.
Much of the accumulated knowledge of the ancient world was lost. Even of the works of the better known thinkers, few fragments survived. Although he wrote at least fourteen books, almost nothing of
HipparchusHipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...
' direct work survived. Of the 150 reputed
AristotelianAristotelianism is a tradition of philosophy that takes its defining inspiration from the work of Aristotle. Aristotelianism is understood by its proponents as critically developing Plato’s theories. Most particularly, Aristotelianism brings Plato’s ideals down to Earth as goals and goods internal...
works, only 30 exist, and some of those are "little more than lecture notes". Though reinterpreted to fit theological concerns, both
Jewish Jewish philosophy refers to the conjunction between serious study of philosophy, Jewish scholasticism and Jewish theology. In one sense, it refers to all philosophical activity carried out by Jews or in relation to the religion of Judaism...
and
IslamicIslamic philosophy is a branch of Islamic studies, and is a longstanding attempt to create harmony between philosophy and the religious teachings of Islam .-Definition:...
scholarship preserved and developed some of the ancient knowledge that would otherwise have been lost (Judeo-Islamic philosophies (800 - 1400)).
The
IslamIslam Islam Islam ( al-’islām,
[There are ten pronunciations of Islam in English, differing in whether the first or second syllable has the stress, whether the s is or , and whether the a is pronounced as in father, as in cat, or (when the stress is on the i) as in the a of sofa...]
ic
AbbasidThe Abbasid Caliphate was the third of the Islamic Caliphates of the Islamic Empire. It was ruled by the Abbasid dynasty of caliphs, who built their capital in Baghdad after overthrowing the Umayyad caliphs from all but Al Andalus....
caliphThe Caliph is the head of state in a Caliphate, and the title for the leader of the Islamic Ummah, an Islamic community ruled by the Shari'ah. It is a transliterated version of the Arabic word which means "successor" or "representative"...
s gathered many classic works of antiquity and had them translated into Arabic.
Islamic philosophersIslamic philosophy is a branch of Islamic studies, and is a longstanding attempt to create harmony between philosophy and the religious teachings of Islam .-Definition:...
such as
Al-Kindi' , also known to the West by the Latinized version of his name Alkindus, was an Arab Iraqi polymath: an Islamic philosopher, scientist, astrologer, astronomer, cosmologist, chemist, logician, mathematician, musician, physician, physicist, psychologist, and meteorologist...
(Alkindus),
Al-FarabiAbū Naṣr al-Fārābi , known in the West as Alpharabius Abū Naṣr al-Fārābi (أبو نصر محمد الفارابي - Abū Naṣr Muḥammad al-Fārābi; in some sources also mentioned as محمد بن محمد بن أوزلغ الفارابي - Muḥammad ibn Muḥammad (ibn Tarḫān) ibn Awzlaġ al-Fārābi), known in the West as...
(Alpharabius),
Avicenna, known as Abū Alī Sīnā or Ibn Sīnā , and commonly known in English by his Latinized name Avicenna , was a Persian polymath and the foremost physician and philosopher of his time...
(Ibn Sina) and
AverroesAbū 'l-Walīd Muḥammad ibn Aḥmad ibn Rushd , better known just as Ibn Rushd , and in European literature as Averroes , was an Andalusian Muslim polymath of Moroccan origins; a master of Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music...
(Ibn Rushd) reinterpreted Greek though in the context of their religion. Important contributions were made by Ibn al-Haytham and Abū Rayhān Bīrūnī before eventually passing on to
Western EuropeWestern Europe is the collection of countries in the westernmost region of Europe, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a cultural entity—the region lying west of Central Europe...
where they were studied by scholars such as
Roger BaconRoger Bacon, O.F.M. , also known as Doctor Mirabilis , was an English philosopher and Franciscan friar who placed considerable emphasis on empiricism...
and
WiteloWitelo - also known as Erazmus Ciolek Witelo, Witelon, Vitellio, Vitello, Vitello Thuringopolonis, Vitulon, Erazm Ciołek, , was a Silesian and Polish friar, theologian and scientist: physicist, natural philosopher, mathematician...
.
Awareness of ancient works re-entered the West through translations from Arabic to Latin. Their re-introduction, combined with
Judeo-IslamicThe historical interaction of Judaism and Islam started in the 7th century AD with the origin and spread of Islam in the Arabian peninsula. Because Judaism and Islam share a common origin in the Middle East through Abraham, both are considered Abrahamic religions...
theological commentaries, had a great influence on
Medieval philosophersMedieval philosophy is the philosophy of Europe and the Middle East in the era now known as medieval or the Middle Ages, the period roughly extending from the fall of the Roman Empire in the fifth century A.D. to the Renaissance in the sixteenth century...
such as
Thomas AquinasSaint Thomas Aquinas, O.P. was a priest of the Roman Catholic Church in the Dominican Order from Italy, and an immensely influential philosopher and theologian in the tradition of scholasticism, known as Doctor Angelicus and Doctor Communis...
.
Scholastic European scholarsScholasticism is derived from the Latin word scholasticus , which means "that [which] belongs to the school," and was a method of learning taught by the academics of medieval universities circa 1100–1500...
, who sought to reconcile the philosophy of the ancient classical philosophers with
Judeo-ChristianJudeo–Christian is a term used in the United States, broadly to describe a body of concepts and values thought to be held in common by Judaism and Christianity...
theology, proclaimed Aristotle the greatest thinker of the ancient world. In cases where they didn't directly contradict the Bible,
Aristotelian physicsThe Greek philosopher Aristotle developed many theories on the nature of physics. These involved what Aristotle described as the four elements...
became the foundation for the physical explanations of the European Churches.
Based on Aristotelian physics, Scholastic physics described things as moving according to their essential nature. Celestial objects were described as moving in circles, because perfect circular motion was considered an innate property of objects that existed in the uncorrupted realm of the
celestial spheresThe celestial spheres, or celestial orbs, were the fundamental celestial entities of the cosmological celestial mechanics first invented by Eudoxus, and developed by Aristotle, Ptolemy, Copernicus and others...
. The
theory of impetusThe theory of impetus was an auxiliary or secondary theory of Aristotelian dynamics, put forth initially to explain projectile motion against gravity. It was first introduced by Hipparchus in antiquity, and subsequently further developed by John Philoponus in the 6th century AD...
, the ancestor to the concepts of
inertiaInertia is the resistance of any physical object, to a change in its state of motion. It is represented numerically by an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by...
and
momentumIn classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section "modern definitions of momentum" on this page...
, was developed along similar lines by
medieval philosophersMedieval philosophy is the philosophy of Europe and the Middle East in the era now known as medieval or the Middle Ages, the period roughly extending from the fall of the Roman Empire in the fifth century A.D. to the Renaissance in the sixteenth century...
such as
John PhiloponusJohn Philoponus , also known as John the Grammarian or John of Alexandria, was a Christian and Aristotelian commentator and the author of a considerable number of philosophical treatises and theological works...
,
Avicenna, known as Abū Alī Sīnā or Ibn Sīnā , and commonly known in English by his Latinized name Avicenna , was a Persian polymath and the foremost physician and philosopher of his time...
and
Jean BuridanJean Buridan was a French priest who sowed the seeds of the Copernican revolution in Europe. Although he was one of the most famous and influential philosophers of the late Middle Ages, he is today among the least well known...
. Motions below the lunar sphere were seen as imperfect, and thus could not be expected to exhibit consistent motion. More idealized motion in the “sublunary” realm could only be achieved through artifice, and prior to the 17th century, many did not view artificial experiments as a valid means of learning about the natural world. Physical explanations in the sublunary realm revolved around tendencies. Stones contained the element earth, and earthy objects tended to move in a straight line toward the centre of the earth (and the universe in the Aristotelian geocentric view) unless otherwise prevented from doing so.
Important physical and mathematical traditions also existed in
ancient ChineseThe history of science and technology in China is both long and rich with many contributions to science and technology. In antiquity, independently of Greek philosophers and other civilizations, ancient Chinese philosophers made significant advances in science, technology, mathematics, and...
and Indian sciences. In
Indian philosophyThe term Indian philosophy , may refer to any of several traditions of philosophical thought that originated in the Indian subcontinent, including Hindu philosophy, Buddhist philosophy, and Jain philosophy...
, Kannada of the
VaisheshikaVaisheshika, or ', is one of the six Hindu schools of philosophy of India. Historically, it has been closely associated with the Hindu school of logic, Nyaya....
school proposed the theory of atomism during the 1st millenium BC, and it was further elaborated on by the
Buddhist atomistsBuddhist atomism is a school of atomistic Buddhist philosophy that flourished on the Indian subcontinent during two major periods. During the first phase, which began to develop prior to the 4th century BCE, Buddhist atomism had a very qualitative, Aristotelian-style atomic theory. This form of...
DharmakirtiDharmakirti , was an Indian scholar and one of the Buddhist founders of Indian philosophical logic. He was one of the primary theorists of Buddhist atomism, according to which the only items considered to exist are momentary Buddhist atoms and states of consciousness.-History:Born around the turn...
and
DignāgaDignāga was an Indian scholar and one of the Buddhist founders of Indian logic....
during the 1st millenium AD. In Indian astronomy,
AryabhataAryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...
's
AryabhatiyaĀryabhatīya, an astronomical treatise, is the magnum opus and only extant work of the 5th century Indian mathematician, Aryabhata.- Structure and style:...
(499 AD) proposed the Earth's rotation, while
Nilakantha SomayajiNilakantha Somayaji , from Kerala, was a major Indian mathematician and astronomer of the Kerala school of astronomy and mathematics and was a student of Damodara. Later, he lived in Tryambakeshwar. Among his many influential books, he wrote the comprehensive astronomical treatise Tantrasamgraha...
(1444-1544) of the Kerala school of astronomy and mathematics proposed a semi-heliocentric model resembling the
Tychonic systemThe Tychonic system was a model of the solar system published by Tycho Brahe in the late 16th century which combined what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system. The model may have been inspired by Paul...
. In
Chinese philosophyChinese philosophy is philosophy written in the Chinese tradition of thought. Chinese philosophy has a history of several thousand years; its origins are often traced back to the Yi Jing , an ancient compendium of divination, which uses a system of 64 hexagrams to guide action...
,
MoziMozi , original name Mo Di , was a philosopher who lived in China during the Hundred Schools of Thought period ，born in Tengzhou, Shandong Province. He founded the school of Mohism and argued strongly against Confucianism and Daoism...
(c. 470-390 BC) proposed a concept similar to
inertiaInertia is the resistance of any physical object, to a change in its state of motion. It is represented numerically by an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by...
, while in optics,
Shen KuoShen Kuo or Shen Gua , style name Cunzhong and pseudonym Mengqi Weng , was a polymathic Chinese scientist and statesman of the Song Dynasty...
(1031–1095 AD) independently developed a
camera obscuraThe camera obscura is an optical device that projects an image of its surroundings on a screen. It is used in drawing and for entertainment, and was one of the inventions that led to photography. The device consists of a box or room with a hole in one side...
.
Emergence of experimental method and physical optics
The use of
empiricalThe word empirical denotes information gained by means of observation, experience, or experiment. A central concept in science and the scientific method is that all evidence must be empirical, or empirically based, that is, dependent on evidence or consequences that are observable by the senses...
experiments in
geometrical opticsGeometrical optics, or ray optics, describes light propagation in terms of "rays". The "ray" in geometric optics is an abstraction, or "instrument", which can be used to approximately model how light will propagate. Light rays bend at the interface between two dissimilar media, and may curve in a...
dates back to second century Roman Egypt, where
PtolemyClaudius Ptolemaeus , known in English as Ptolemy , was a Roman citizen of Greek ancestry. He was a mathematician, astronomer, geographer, astrologer and a poet of a single epigram in the Greek Anthology. He lived in Egypt under the Roman Empire, and is believed to have been born in the town of...
carried out several
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
s on
reflectionIn mathematics, a reflection is a map that transforms an object into its mirror image. For example, a reflection of the small English letter p in respect to a vertical line would look like q...
,
refractionRefraction is the change in direction of a wave due to a change in its velocity. This is most commonly observed when a wave passes from one medium to another...
and
binocular visionBinocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...
. However, he either discarded or
rationalizedIn psychology and logic, rationalization is the process of constructing a logical justification for a belief, decision, action or lack thereof that was originally arrived at through a different mental process...
any empirical data that did not support his
PlatonicPlatonism is the philosophy of Plato or the name of other philosophical systems considered closely derived from it. In a narrower sense the term might indicate the doctrine of Platonic realism. The central concept of Platonism is the Theory of Forms: the transcendent, perfect archetypes, of which...
paradigm. Experiments did not hold any importance at the time, and empirical evidence was thus seen as secondary to general theory. The incorrect
emission theory of visionEmission theory or extramission theory is the proposal that visual perception is accomplished by rays of light emitted by the eyes. This theory has been replaced by intromission theory, which states that visual perception comes from something representative of the object entering the eyes...
thus continued to dominate optics through to the 10th century.
The turn of the
second millenniumBeethoven|Te Kooti|- align="left"!20th Century|Nelson Mandela
Paul Rusesabagina|Martin Luther King, Jr.
Franklin D...
saw the development of an
experimental methodScientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and measurable evidence subject to specific...
emphasizing the role of
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
ation as a form of proof for scientific inquiry together with the development of
physical opticsIn physics, physical optics, or wave optics, is the branch of optics which studies interference, diffraction, polarization, and other phenomena for which the ray approximation of geometric optics is not valid...
where mathematics and geometry were combined with the philosophical field of physics. The Iraqi physicist, Ibn al-Haytham (Alhazen), is considered a central figure in this shift in physics from a philosophical activity to an experimental and mathematical one, and the shift in optics from a mathematical discipline to a physical and experimental one. Due to his
positivistPositivism is a philosophy that holds that the only authentic knowledge is that which is based on actual sense experience. Metaphysical speculation is avoided...
approach, his
Doubts Concerning Ptolemy insisted on
scientific demonstrationA scientific demonstration is a scientific experiment carried out for the purposes of demonstrating scientific principles, rather than for hypothesis testing or knowledge gathering ....
and criticized Ptolemy's
confirmation biasConfirmation bias is an irrational tendency to search for, interpret or remember information in a way that confirms preconceptions or working hypotheses. It is a type of cognitive bias and a systematic error of inductive reasoning...
and
conjecturalA conjecture is a proposition which is presumed to be real, true, or genuine, mostly based on inconclusive grounds. Karl Popper pioneered the use of the term "conjecture" in scientific philosophy. Conjecture is contrasted by hypothesis , which is a testable statement based on accepted grounds...
undemonstrated theories. His
Book of OpticsThe Book of Optics was a seven-volume treatise on optics, physics, mathematics, anatomy and psychology written by the Iraqi Muslim scientist, Ibn al-Haytham , from 1011 to 1021, when he was under house arrest in Cairo, Egypt.The book...
(1021) was the earliest successful attempt at unifying a mathematical discipline (geometrical optics) with the philosophical field of physics, to create the modern science of physical optics. An important part of this was the intromission theory of
visionVisual perception is the ability to interpret information and surroundings from visible light reaching the eye. The resulting perception is also known as eyesight, sight or vision...
, which in order to prove, he developed an experimental method to test his hypothesis. He conducted various experiments to prove his intromission theory and other hypotheses on light and vision. The
Book of Optics established experimentation as the norm of proof in optics, and gave optics a physico-mathematical conception at a much earlier date than the other mathematical disciplines. His
On the Light of the Moon also attempted to combine mathematical astronomy with physics, a field now known as
astrophysicsAstrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects such as galaxies, stars, planets, exoplanets, and the interstellar medium, as well as their...
, to formulate several astronomical hypotheses which he proved through experimentation.
Galileo Galilei and the rise of physico-mathematics
In the 17th century,
natural philosophersNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
began to mount a sustained attack on the
ScholasticScholasticism is derived from the Latin word scholasticus , which means "that [which] belongs to the school," and was a method of learning taught by the academics of medieval universities circa 1100–1500...
philosophical program, and supposed that mathematical descriptive schemes adopted from such fields as mechanics and astronomy could actually yield universally valid characterizations of motion. The
TuscanThe Grand Duchy of Tuscany was a central Italian monarchy that existed, with Interruptions, from 1569 to 1859, replacing the Duchy of Florence...
mathematician
Galileo GalileiGalileo Galilei was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations, and support for Copernicanism...
was the central figure in the shift to this perspective. As a mathematician, Galileo’s role in the
universityEuropean research universities have a long history that arguably dates back to the founding of the University of Bologna in 1088, although the University of Paris and the University of Magnaura are other contenders for this position...
culture of his era was subordinated to the three major topics of study:
lawLaw is a system of rules, usually enforced through a set of institutions. It shapes politics, economics and society in numerous ways and serves as a primary social mediator of relations between people. Contract law regulates everything from buying a bus ticket to trading on derivatives markets...
,
medicineMedicine is the art and science of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, and
theologyThe term "theology" literally means the study of God, deriving from the Greek word theos, meaning 'God', and the suffix -ology from the Greek word logos meaning "discourse", "theory", or "reasoning"...
(which was closely allied to philosophy). Galileo, however, felt that the descriptive content of the technical disciplines warranted philosophical interest, particularly because mathematical analysis of astronomical observations—notably the radical analysis offered by astronomer
Nicolaus CopernicusNicolaus Copernicus was the first astronomer to formulate a comprehensive heliocentric cosmology, which displaced the Earth from the center of the universe...
concerning the relative motions of the sun, earth, moon, and planets—indicated that philosophers’ statements about the nature of the universe could be shown to be in error. Galileo also performed mechanical experiments, and insisted that motion itself—regardless of whether that motion was natural or artificial—had universally consistent characteristics that could be described mathematically.
Galileo used his 1609 telescopic discovery of the
moons of JupiterThe Galilean moons are the four moons of Jupiter discovered by Galileo Galilei on January 7, 1610. They are the largest of the many moons of Jupiter and derive their names from the lovers of Zeus: Io, Europa, Ganymede and Callisto. Ganymede, Europa and Io participate in a 1:2:4 orbital resonance...
, as published in his
Sidereus NunciusSidereus Nuncius is a short treatise published in New Latin by Galileo Galilei in March 1610. It was the first scientific treatise based on observations made through a telescope...
in 1610, to procure a position in the
MediciThe House of Medici was a political dynasty, banking family and later royal house who first began to gather prominence under Cosimo de' Medici in the Republic of Florence during the late 14th century. The family originated in the Mugello region of the Tuscan countryside, gradually rising until...
court with the dual title of mathematician and philosopher. As a court philosopher, he was expected to engage in debates with philosophers in the Aristotelian tradition, and received a large audience for his own publications, such as
The AssayerThe Assayer was a book published in Rome by Galileo Galilei in October 1623.The book was a polemic against the treatise on the comets of 1618 by Orazio Grassi, a Jesuit mathematician at the Collegio Romano. In this matter Grassi, for all his Aristotelianism, was right and Galileo was wrong...
and
Discourses and Mathematical Demonstrations Concerning Two New SciencesThe Discourses and Mathematical Demonstrations Relating to Two New Sciences was Galileo's final book and a sort of scientific testament covering much of his work in physics over the preceding thirty years.Unlike the Dialogue Concerning the Two Chief World Systems, it was not published with a license...
, which was published abroad after he was placed under house arrest for his publication of
Dialogue Concerning the Two Chief World SystemsThe Dialogue Concerning the Two Chief World Systems was a 1632 Italian language book by Galileo Galilei comparing the Copernican system with the traditional Ptolemaic system...
in 1632.
Galileo’s interest in the mechanical experimentation and mathematical description in motion established a new natural philosophical tradition focused on experimentation. This tradition, combining with the non-mathematical emphasis on the collection of "experimental histories" by philosophical reformists such as
William GilbertWilliam Gilbert, also known as Gilbard, was an English physician and natural philosopher. He was an early Copernican, and passionately rejected both the prevailing Aristotelian philosophy and the Scholastic method of university teaching...
and
Francis BaconFrancis Bacon,1st Viscount St Alban KC , son of Nicholas Bacon by his second wife Anne Bacon, was an English philosopher, statesman, scientist, lawyer, jurist, and author. He served both as Attorney General and Lord Chancellor of England...
, drew a significant following in the years leading up to and following Galileo’s death, including
Evangelista TorricelliEvangelista Torricelli was an Italian physicist and mathematician, best known for his invention of the barometer.-Biography:Torricelli was born in Faenza, then part of the Papal States...
and the participants in the
Accademia del CimentoThe Accademia del Cimento , an early scientific society, was founded in Florence 1657 by students of Galileo, Evangelista Torricelli and Vincenzo Viviani. The foundation of Academy was funded by Prince Leopoldo and Grand Duke Ferdinando II de' Medici. Giovanni Borelli and Nicolaus Steno were also...
in Italy;
Marin MersenneMarin Mersenne, Marin Mersennus or le Père Mersenne was a French theologian, philosopher, mathematician and music theorist, often referred to as the "father of acoustics" .-Life:...
and
Blaise Pascal Blaise Pascal , was a French mathematician, physicist, and religious philosopher. He was a child prodigy who was educated by his father, a civil servant...
in France;
Christiaan HuygensChristiaan Huygens, FRS was a prominent Dutch mathematician, astronomer, physicist, horologist, and writer of early science fiction...
in the Netherlands; and
Robert HookeRobert Hooke, FRS was an English natural philosopher, architect and polymath who played an important role in the scientific revolution, through both experimental and theoretical work....
and
Robert BoyleRobert Boyle was a natural philosopher, chemist, physicist, inventor, and gentleman scientist, also noted for his writings in theology. He is best known for the formulation of Boyle's law...
in England.
The Cartesian philosophy of motion
The French philosopher
René DescartesRené Descartes , , also known as Renatus Cartesius , was a French philosopher, mathematician, physicist, and writer who spent most of his adult life in the Dutch Republic...
was well-connected to, and influential within, the experimental philosophy networks. Descartes had a more ambitious agenda, however, which was geared toward replacing the Scholastic philosophical tradition altogether. Questioning the reality interpreted through the senses, Descartes sought to re-establish philosophical explanatory schemes by reducing all perceived phenomena to being attributable to the motion of an invisible sea of “corpuscles”. (Notably, he reserved human thought and
GodGod is a deity in theistic and deistic religions and other belief systems, representing either the sole deity in monotheism, or a principal deity in polytheism....
from his scheme, holding these to be separate from the physical universe). In proposing this philosophical framework, Descartes supposed that different kinds of motion, such as that of planets versus that of terrestrial objects, were not fundamentally different, but were merely different manifestations of an endless chain of corpuscular motions obeying universal principles. Particularly influential were his explanation for circular astronomical motions in terms of the vortex motion of corpuscles in space (Descartes argued, in accord with the beliefs, if not the methods, of the Scholastics, that a
vacuumIn everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty...
could not exist), and his explanation of gravity in terms of corpuscles pushing objects downward.
Descartes, like Galileo, was convinced of the importance of mathematical explanation, and he and his followers were key figures in the development of mathematics and geometry in the 17th century. Cartesian mathematical descriptions of motion held that all mathematical formulations had to be justifiable in terms of direct physical action, a position held by
HuygensChristiaan Huygens, FRS was a prominent Dutch mathematician, astronomer, physicist, horologist, and writer of early science fiction...
and the German philosopher
Gottfried LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
, who, while following in the Cartesian tradition, developed his own philosophical alternative to Scholasticism, which he outlined in his 1714 work,
The Monadology.
Newtonian motion versus Cartesian motion
In the late 17th and early 18th centuries, the Cartesian mechanical tradition was challenged by another philosophical tradition established by the Cambridge University mathematician
Isaac NewtonSir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is perceived and considered by a substantial number of scholars and the general public as one of the most influential men in history...
. Where
DescartesRené Descartes , , also known as Renatus Cartesius , was a French philosopher, mathematician, physicist, and writer who spent most of his adult life in the Dutch Republic...
held that all motions should be explained with respect to the immediate force exerted by corpuscles, Newton chose to describe universal motion with reference to a set of fundamental mathematical principles: his
three laws of motionNewton's laws of motion are three physical laws that form the basis for classical mechanics. They are:# In the absence of force, a body either is at rest or moves in a straight line with constant speed....
and the
law of gravitationNewton's law of universal gravitation states that every object in this universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of distance between their centres. This is a general physical law derived...
, which he introduced in his 1687 work
Mathematical Principles of Natural Philosophy. Using these principles, Newton removed the idea that objects followed paths determined by natural shapes (such as
Kepler’sJohannes Kepler was a German mathematician, astronomer and astrologer, and key figure in the 17th century scientific revolution. He is best known for his eponymous laws of planetary motion, codified by later astronomers based on his works Astronomia nova, Harmonices Mundi, and Epitome of...
idea that planets moved naturally in
ellipseIn mathematics, an ellipse is the bounded case of a conic section, the geometric shape that results from cutting a circular conical or cylindrical surface with an oblique plane...
s), and instead demonstrated that not only regularly observed paths, but all the future motions of any body could be deduced mathematically based on knowledge of their existing motion, their
massIn physics, mass commonly refers to any of three properties of matter, which have been shown experimentally to be equivalent: inertial mass, active gravitational mass and passive gravitational mass...
, and the
forceIn physics, a force is any agent that causes a change in the motion of a free body, or that causes stress in a fixed body. It can also be described by intuitive concepts such as a push or pull that can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a...
s acting upon them. However, observed celestial motions did not precisely conform to a Newtonian treatment, and Newton, who was also deeply interested in
theologyThe term "theology" literally means the study of God, deriving from the Greek word theos, meaning 'God', and the suffix -ology from the Greek word logos meaning "discourse", "theory", or "reasoning"...
, imagined that God intervened to ensure the continued stability of the solar system.
Newton’s principles (but not his mathematical treatments) proved controversial with Continental philosophers, who found his lack of
metaphysicalMetaphysics investigates principles of reality transcending those of any particular science. Cosmology and ontology are traditional branches of metaphysics. It is concerned with explaining the fundamental nature of being and the world...
explanation for movement and gravitation philosophically unacceptable. Beginning around 1700, a bitter rift opened between the Continental and British philosophical traditions, which were stoked by heated, ongoing, and viciously personal disputes between the followers of Newton and
LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
concerning priority over the analytical techniques of
calculusCalculus is a discipline in mathematics focused on limits, functions, derivatives, integrals, and infinite series. This subject constitutes a major part of modern mathematics education. It has two major branches, differential calculus and integral calculus, which are related by the fundamental...
, which each had developed independently. Initially, the Cartesian and Leibnizian traditions prevailed on the Continent (leading to the dominance of the Leibnizian calculus notation everywhere except Britain). Newton himself remained privately disturbed at the lack of a philosophical understanding of gravitation, while insisting in his writings that none was necessary to infer its reality. As the 18th century progressed, Continental natural philosophers increasingly accepted the Newtonians’ willingness to forgo
ontologicalOntology is the philosophical study of the nature of being, existence or reality in general, as well as of the basic categories of being and their relations...
metaphysical explanations for mathematically described motions.
Rational mechanics in the 18th century
The mathematical analytical traditions established by Newton and Leibniz flourished during the 18th century as more mathematicians learned calculus and elaborated upon its initial formulation. The application of mathematical analysis to problems of motion was known as rational mechanics, or mixed mathematics (and was later termed
classical mechanicsIn the fields of physics, classical mechanics is one of the two major sub-fields of study in the science of mechanics, which is concerned with the set of physical laws governing and mathematically describing the motions of bodies and aggregates of bodies geometrically distributed within a certain...
). This work primarily revolved around
celestial mechanicsCelestial mechanics is the branch of astronomy that deals with the motions of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data. Orbital mechanics is a subfield which focuses on...
, although other applications were also developed, such as the Swiss mathematician
Daniel Bernoulli’sDaniel Bernoulli was a Dutch-Swiss mathematician and was one of the many prominent mathematicians in the Bernoulli family. He is particularly remembered for his applications of mathematics to mechanics, especially fluid mechanics, and for his pioneering work in probability and statistics...
treatment of
fluid dynamicsIn physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...
, which he introduced in his 1738 work
Hydrodynamica.
Rational mechanics dealt primarily with the development of elaborate mathematical treatments of observed motions, using Newtonian principles as a basis, and emphasized improving the tractability of complex calculations and developing of legitimate means of analytical approximation. A representative contemporary textbook was published by
Johann Baptiste HorvathJohann Baptiste Horvath was a Hungarian-born Jesuit Professor of Physics and Philosophy at the University of Trnava in modern-day Slovakia, which was then part of the Kingdom of Hungary...
. By the end of the century analytical treatments were rigorous enough to verify the stability of the
solar systemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
solely on the basis of Newton’s laws without reference to divine intervention—even as deterministic treatments of systems as simple as the
three body problemTo understand the motion of celestial bodies, the sun, planets and the visible stars has been the main motivation for the -body problem. The first complete mathematical formulation of this problem appeared in Newton's Principia...
in gravitation remained intractable.
British work, carried on by mathematicians such as
Brook TaylorBrook Taylor FRS was an English mathematician who is best known for Taylor's theorem and the Taylor series.- Life and work :...
and
Colin MaclaurinColin Maclaurin was a British mathematician. Due to changes in orthography since that time , his surname is alternatively written MacLaurin. In Gaelic the name is "Cailean MacLabhruinn", which is literally 'Colin, the son of Laurence.'-Life and work:Maclaurin was born in...
, fell behind Continental developments as the century progressed. Meanwhile, work flourished at scientific academies on the Continent, led by such mathematicians as
Daniel BernoulliDaniel Bernoulli was a Dutch-Swiss mathematician and was one of the many prominent mathematicians in the Bernoulli family. He is particularly remembered for his applications of mathematics to mechanics, especially fluid mechanics, and for his pioneering work in probability and statistics...
,
Leonhard EulerLeonhard Paul Euler was a pioneering Swiss mathematician and physicist who spent most of his life in Russia and Germany. His surname is in English ; the common English pronunciation is incorrect....
, Joseph-Louis Lagrange,
Pierre-Simon LaplacePierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...
, and
Adrien-Marie LegendreAdrien-Marie Legendre was a French mathematician. He made important contributions to statistics, number theory, abstract algebra and mathematical analysis....
. At the end of the century, the members of the
French Academy of SciencesThe French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
had attained clear dominance in the field.
Physical experimentation in the 18th and early 19th centuries
At the same time, the experimental tradition established by
GalileoGalileo Galilei was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations, and support for Copernicanism...
and his followers persisted. The
Royal SocietyThe Royal Society of London for the Improvement of Natural Knowledge, known simply as the Royal Society, or even the Royal, is a learned society for science that was founded in 1660 and is considered by most to be the oldest such society still in existence...
and the
French Academy of SciencesThe French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
were major centers for the performance and reporting of experimental work, and
NewtonSir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is perceived and considered by a substantial number of scholars and the general public as one of the most influential men in history...
was himself an influential experimenter, particularly in the field of
opticsOptics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
, where he was recognized for his
prismIn optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use...
experiments dividing white light into its constituent spectrum of colors, as published in his 1704 book
OpticksOpticks is a book written by English physicist Isaac Newton that was released to the public in 1704. It is about optics and the refraction of light, and is considered one of the great works of science in history...
(which also advocated a particulate interpretation of light). Experiments in mechanics, optics,
magnetismIn physics, the term magnetism is used to describe how materials respond on the microscopic level to an applied magnetic field; to categorize the magnetic phase of a material. For example, the most well known form of magnetism is ferromagnetism such that some ferromagnetic materials produce their...
,
static electricityStatic electricity refers to the buildup of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge...
,
chemistryBy 1000 BC, the ancient civilizations were using technologies that would form the basis of the various branches of chemistry. Extracting metal from their ores, making pottery and glazes, fermenting beer and wine, making pigments for cosmetics and painting, extracting chemicals from plants for...
, and
physiologyPhysiology is the science of the functioning of living systems. It is a subcategory of biology...
were not clearly distinguished from each other during the 18th century, but significant differences in explanatory schemes and, thus, experiment design were emerging. Chemical experimenters, for instance, defied attempts to enforce a scheme of abstract Newtonian forces onto chemical affiliations, and instead focused on the isolation and classification of chemical substances and reactions.
Nevertheless, the separate fields remained tied together, most clearly through the theories of weightless
“imponderable fluids"Imponderable fluids are features of several superseded scientific theories. The term has been used in natural philosophy and physics to explain certain mysterious phenomena as the result of fluids with properties which defy the imagination...
, such as heat (“
caloricThe caloric theory is an obsolete scientific theory that heat consists of a fluid called caloric that flows from hotter to colder bodies. Caloric was also thought of as a weightless gas that could pass in and out of pores in solids and liquids...
”),
electricityThe history of electromagnetism, that is the human understanding and recorded use of electromagnetic forces, dates back over two thousand years; see timeline of electromagnetism. The ancients would have been acquainted with the effects of atmospheric electricity, in particular lightning as...
, and
phlogistonThe phlogiston theory , first stated in 1667 by Johann Joachim Becher, is a defunct scientific theory that posited the existence of a fire-like element called "phlogiston" that was contained within combustible bodies, and released during combustion...
(which was rapidly overthrown as a concept following Lavoisier’s identification of
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
gas late in the century). Assuming that these concepts were real fluids, their flow could be traced through a mechanical apparatus or chemical reactions. This tradition of experimentation led to the development of new kinds of experimental apparatus, such as the
Leyden JarThe Leyden jar, or Leiden jar, is a device that "stores" static electricity between two electrodes on the inside and outside of a jar. It was invented independently by Ewald Georg von Kleist in 11 October 1744 and by Pieter van Musschenbroek in 1745—1746. The latter place of invention, Leiden,...
and the
Voltaic PileA voltaic pile is a set of individual Galvanic cells placed in series. The voltaic pile, invented by Alessandro Volta in 1800, was the first electric battery...
; and new kinds of measuring instruments, such as the
calorimeterA calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity. The word calorimeter is derived from the Latin word calor, meaning heat. Differential scanning calorimeters, isothermal microcalorimeters, titration...
, and improved versions of old ones, such as the
thermometerA thermometer is a device that measures temperature or temperature gradient using a variety of different principles. A thermometer has two important elements: the temperature sensor A thermometer (from the Greek θερμός (thermo) meaning "warm" and meter, "to measure") is a device that measures...
. Experiments also produced new concepts, such as the
University of GlasgowThe University of Glasgow is the fourth-oldest surviving university in the English-speaking world and one of Scotland's four ancient universities...
experimenter
Joseph Black’sJoseph Black was a Scottish physician, physicist, and chemist, known for his discoveries of latent heat, specific heat, and carbon dioxide. He was a founder of thermochemistry who developed many pre-thermodynamics concepts, such as heat capacity, and was the mentor for James Watt...
notion of
latent heatThe expression latent heat refers to the amount of energy released or absorbed by a chemical substance during a change of state that occurs without changing its temperature, meaning a phase transition such as the melting of ice or the boiling of water...
and Philadelphia intellectual
Benjamin Franklin’sBenjamin Franklin was one of the Founding Fathers of the United States of America. A noted polymath, Franklin was a leading author and printer, satirist, political theorist, politician, scientist, inventor, civic activist, statesman, soldier, and diplomat...
characterization of electrical fluid as flowing between places of excess and deficit (a concept later reinterpreted in terms of positive and negative
chargesElectric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields...
).
While it was recognized early in the 18th century that finding absolute theories of electrostatic and magnetic force akin to Newton’s principles of motion would be an important achievement, none were forthcoming. This impossibility only slowly disappeared as experimental practice became more widespread and more refined in the early years of the 19th century in places such as the newly-established
Royal InstitutionThe Royal Institution of Great Britain is an organization devoted to scientific education and research, based in London...
in London, where
John DaltonJohn Dalton FRS was an English chemist, meteorologist and physicist. He is best known for his pioneering work in the development of modern atomic theory, and his research into colour blindness .-Early life:John Dalton was born into a Quaker family at Eaglesfield, near Cockermouth in Cumberland,...
argued for an atomistic interpretation of chemistry,
Thomas YoungThomas Young may refer to:*Thomas Young , Scottish Presbyterian and author*Thomas Young , member of the Sons of Liberty*Thomas Young , British polymath, scientist and Egyptologist...
argued for the interpretation of light as a wave, and
Michael FaradayMichael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....
established the phenomenon of
electromagnetic inductionFaraday's law of induction is a basic law of electromagnetism, which is involved in the working of transformers, inductors, and many forms of electrical generators. The law states:...
. Meanwhile, the analytical methods of rational mechanics began to be applied to experimental phenomena, most influentially with the French mathematician
Joseph Fourier’sJean Baptiste Joseph Fourier was a French mathematician and physicist best known for initiating the investigation of Fourier series and their application to problems of heat transfer. The Fourier transform and Fourier's Law are also named in his honour...
analytical treatment of the flow of heat, as published in 1822.
Thermodynamics, statistical mechanics, and electromagnetic theory
The establishment of a mathematical physics of
energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
between the 1850s and the 1870s expanded substantially on the physics of prior eras and challenged traditional ideas about how the physical world worked. While
Pierre-Simon Laplace’sPierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...
work on celestial mechanics solidified a deterministically mechanistic view of objects obeying fundamental and totally reversible laws, the study of energy and particularly the flow of heat, threw this view of the universe into question. Drawing upon the engineering theory of
LazareLazare Nicolas Marguerite, Comte Carnot , the Organizer of Victory in the French Revolutionary Wars, was a French politician, engineer, and mathematician.-Education and early life:...
and
Sadi CarnotNicolas Léonard Sadi Carnot was a French physicist and military engineer who, in his 1824 Reflections on the Motive Power of Fire, gave the first successful theoretical account of heat engines, now known as the Carnot cycle, thereby laying the foundations of the second law of thermodynamics...
, and Émile Clapeyron; the experimentation of
James Prescott JouleJames Prescott Joule FRS was an English physicist and brewer, born in Salford, Lancashire. Joule studied the nature of heat, and discovered its relationship to mechanical work . This led to the theory of conservation of energy, which led to the development of the first law of thermodynamics...
on the interchangeability of mechanical, chemical, thermal, and electrical forms of work; and his own
Cambridge mathematical triposThe Mathematical Tripos is the taught mathematics course at the University of Cambridge. It is the oldest Tripos that is examined in Cambridge.-Origin of the Mathematical Tripos:...
training in mathematical analysis; the Glasgow physicist
William ThomsonWilliam Thomson, 1st Baron Kelvin , OM, GCVO, PC, PRS, FRSE, was a British mathematical physicist and engineer...
and his circle of associates established a new mathematical physics relating to the exchange of different forms of energy and energy’s overall conservation (what is still accepted as the “
first law of thermodynamicsThe first law of thermodynamics, an expression of the principle of conservation of energy, states that energy can be transformed , but cannot be created or destroyed. Alternatively:-Description:...
”). Their work was soon allied with the theories of similar but less-known work by the German physician
Julius Robert von MayerJulius Robert von Mayer was a German physician and physicist and one of the founders of thermodynamics...
and physicist and physiologist
Hermann von HelmholtzHermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...
on the conservation of forces.
Taking his mathematical cues from the heat flow work of
Joseph FourierJean Baptiste Joseph Fourier was a French mathematician and physicist best known for initiating the investigation of Fourier series and their application to problems of heat transfer. The Fourier transform and Fourier's Law are also named in his honour...
(and his own religious and
geologicalThe history of geology is concerned with the development of the natural science of geology. Geology is the scientific study of the origin, history, and structure of the Earth. Throughout the ages geology provides essential theories and data that shape how society conceptualizes the...
convictions), Thomson believed that the dissipation of energy with time (what is accepted as the “
second law of thermodynamicsThe second law of thermodynamics is an expression of the universal principle of entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium, and that the entropy change dS of a system undergoing any...
”) represented a fundamental principle of physics, which was expounded in Thomson and
Peter Guthrie Tait’sPeter Guthrie Tait was a Scottish mathematical physicist, best known for the seminal energy physics textbook Treatise on Natural Philosophy, which he co-wrote with Kelvin, and his early investigations into knot theory, which contributed to the eventual formation of topology as a mathematical...
influential work
Treatise on Natural Philosophy. However, other interpretations of what Thomson called
thermodynamicsIn physics, thermodynamics is the study of the conversion of energy into work and heat and its relation to macroscopic variables such as temperature, volume and pressure...
were established through the work of the German physicist
Rudolf ClausiusRudolf Julius Emanuel Clausius , was a German physicist and mathematician and is considered one of the central founders of the science of thermodynamics. By his restatement of Sadi Carnot's principle known as the Carnot cycle, he put the theory of heat on a truer and sounder basis...
. His
statistical mechanicsStatistical mechanics is the application of probability theory, which includes mathematical tools for dealing with large populations, to the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force...
, which was elaborated upon by
Ludwig BoltzmannLudwig Eduard Boltzmann was an Austrian physicist famous for his founding contributions in the fields of statistical mechanics and statistical thermodynamics...
and the British physicist
James Clerk MaxwellJames Clerk Maxwell was a Scottish theoretical physicist and mathematician. His most significant achievement was the development of the classical electromagnetic theory, synthesizing all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a...
, held that energy (including heat) was a measure of the speed of particles. Interrelating the statistical likelihood of certain states of organization of these particles with the energy of those states, Clausius reinterpreted the dissipation of energy to be the statistical tendency of molecular configurations to pass toward increasingly likely, increasingly disorganized states (coining the term “
entropyEntropy is a concept of information maintaining great importance in physics, chemistry, and information theory...
” to describe the disorganization of a state). The statistical versus absolute interpretations of the second law of thermodynamics set up a dispute that would last for several decades (producing arguments such as “
Maxwell's demonMaxwell's demon is a thought experiment, first formulated in 1867 by the Scottish physicist James Clerk Maxwell, intended by Maxwell primarily to "show that the 2nd Law of Thermodynamics has only a statistical certainty," and commonly used for imagining the possibility of violating it...
”), and that would not be held to be definitively resolved until the behavior of atoms was firmly established in the early 20th century.
Meanwhile, the new physics of energy transformed the analysis of electromagnetic phenomena, particularly through the introduction of the concept of the
fieldIn physics, a field is a physical quantity associated to each point of spacetime. A field can be classified as a scalar field, a vector field, or a tensor field, according to whether the value of the field at each point is a scalar, a vector, or, more generally, a tensor, respectively...
and the publication of Maxwell’s 1873
Treatise on Electricity and Magnetism, which also drew upon theoretical work by German theoreticians such as
Carl Friedrich GaussJohann Carl Friedrich Gauss was a German mathematician and scientist who contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, geophysics, electrostatics, astronomy and optics...
and
Wilhelm WeberWilhelm Eduard Weber was a German physicist and, together with Carl Friedrich Gauss, inventor of the first electromagnetic telegraph.-Early years:...
. The encapsulation of heat in particulate motion, and the addition of electromagnetic forces to Newtonian dynamics established an enormously robust theoretical underpinning to physical observations. The prediction that light represented a transmission of energy in wave form through a “
luminiferous etherIn the late 19th century, "luminiferous aether" , meaning light-bearing aether, was the term used to describe a medium for the propagation of light. The word aether stems via Latin from the Greek αιθήρ, from a root meaning to kindle, burn, or shine...
”, and the seeming confirmation of that prediction with Helmholtz student Heinrich Hertz’s 1888 detection of
electromagnetic radiationElectromagnetic radiation is a ubiquitous phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It consists of electric and magnetic field components which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation...
, was a major triumph for physical theory and raised the possibility that even more fundamental theories based on the field could soon be developed. Research on the transmission of electromagnetic waves began soon after, with the experiments conducted by physicists such as
Nikola TeslaNikola Tesla was an inventor and a mechanical and electrical engineer. He is frequently cited as one of the most important contributors to the birth of commercial electricity and is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th...
, Jagadish Chandra Bose and
Guglielmo MarconiMarchese Guglielmo Marconi was an Italian inventor, best known for his development of a radiotelegraph system, which served as the foundation for the establishment of numerous affiliated companies worldwide...
during the 1890s leading to the
invention of radioWithin the history of radio, several people were involved in the invention of radio and there were many key inventions in what became the modern systems of wireless. Radio development began as "wireless telegraphy". Closely related, radio was developed along with two other key inventions, the...
.
The emergence of a new physics circa 1900
The triumph of Maxwell’s theories was undermined by inadequacies that had already begun to appear. The
Michelson-Morley experimentThe Michelson–Morley experiment was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University. It is generally considered to be the first strong evidence against the theory of a luminiferous aether...
failed to detect a shift in the
speed of lightIn physics, the speed of light is a physical constant, the speed at which electromagnetic radiation, such as light, travels in free space . Its value is 299,792,458 metres per second...
, which would have been expected as the earth moved at different angles with respect to the ether. The possibility explored by
Hendrik LorentzHendrik Antoon Lorentz was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect...
, that the ether could compress matter, thereby rendering it undetectable, presented problems of its own as a compressed
electronAn electron is a subatomic particle that carries a negative electric charge. It has no known substructure and is believed to be a point particle. An electron has a mass that is approximately 1836 times less than that of the proton. The intrinsic angular momentum of the electron is a half integer...
(detected in 1897 by British experimentalist
J. J. ThomsonSir Joseph John “J. J.” Thomson, OM, FRS was a British physicist and Nobel laureate, credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer...
) would prove unstable. Meanwhile, other experimenters began to detect unexpected forms of radiation: Wilhelm Röntgen caused a sensation with his discovery of
x-rayX-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays...
s in 1895; in 1896
Henri BecquerelAntoine Henri Becquerel was a French physicist, Nobel laureate, and the discoverer of radioactivity, for which he won the 1903 Nobel Prize in Physics .-Early life:Becquerel was born in Paris into a family which produced four generations of scientists,...
discovered that certain kinds of matter emit radiation on their own accord.
MarieMarie Skłodowska Curie was a physicist and chemist of Polish upbringing and, subsequently, French citizenship...
and
Pierre CuriePierre Curie was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity, and Nobel laureate...
coined the term “
radioactivityRadioactive decay is the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, named the daughter...
” to describe this property of matter, and isolated the radioactive elements
radiumRadium is a radioactive chemical element which has the symbol Ra and atomic number 88. Its appearance is almost pure white, but it readily oxidizes on exposure to air, turning black. Radium is an alkaline earth metal that is found in trace amounts in uranium ores. It is extremely radioactive...
and
poloniumPolonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie and Pierre Curie. A rare and highly radioactive metalloid, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Polonium has been studied for possible use in...
.
Ernest RutherfordErnest Rutherford, 1st Baron Rutherford of Nelson, OM, FRS was a New Zealand chemist and physicist who became known as the father of nuclear physics....
and
Frederick SoddyFrederick Soddy was an English radiochemist who explained, with Ernest Rutherford, that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions. He also proved the existence of isotopes of certain radioactive elements...
identified two of Becquerel’s forms of radiation with electrons and the element
heliumHelium is the chemical element with atomic number 2, and is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert monatomic gas that heads the noble gas group in the periodic table...
. In 1911 Rutherford established that the bulk of mass in atoms are concentrated in positively-charged nuclei with orbiting electrons, which was a theoretically unstable configuration. Studies of radiation and radioactive decay continued to be a preeminent focus for physical and chemical research through the 1930s, when the discovery of
nuclear fissionIn nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts, often producing free neutrons and lighter nuclei, which may eventually produce photons...
opened the way to the practical exploitation of what came to be called
“atomic” energyNuclear energy is released by the splitting or merging together of the nuclei of atom. The conversion of nuclear mass to energy is consistent with the mass-energy equivalence formula ΔE = Δm.c², in which ΔE = energy release, Δm = mass defect, and c = the speed of light in a vacuum...
.
Radical new physical theories also began to emerge in this same period. In 1905
Albert EinsteinAlbert Einstein was a theoretical physicist. His many contributions to physics include the special and general theories of relativity, the founding of relativistic cosmology, the first post-Newtonian expansion, explaining the perihelion advance of Mercury, prediction of the deflection of...
, then a Bern patent clerk, argued that the speed of light was a constant in all
inertial reference framesIn physics, an inertial frame of reference is a member of the subset of reference frames with the property that every physical law takes the same form in each such frame. In contrast, in the set of non-inertial frames the laws of physics are frame-dependent, and the usual physical forces must be...
and that electromagnetic laws should remain valid independent of reference frame—assertions which rendered the ether “superfluous” to physical theory, and that held that observations of time and length varied relative to how the observer was moving with respect to the object being measured (what came to be called the “
special theory of relativitySpecial relativity is the physical theory of measurement in inertial frames of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies"...
”). It also followed that mass and energy were interchangeable quantities according to the equation
E=mc2In physics, mass–energy equivalence is the concept that the mass of a body is a measure of its energy content. The mass of a body as measured on a scale is always equal to the total energy inside, multiplied by a constant c
2 that changes the units appropriately:where E is energy, m is...
. In another paper published the same year, Einstein asserted that electromagnetic radiation was transmitted in discrete quantities (“
quantaIn physics, a quantum is the minimum unit of any physical entity involved in an interaction. An example of an entity that is quantized is the energy transfer of elementary particles of matter and of photons and other bosons...
”), according to a constant that the theoretical physicist
Max PlanckMax Planck was a German physicist. He is considered to be the founder of the quantum theory, and thus one of the most important physicists of the twentieth century. Planck was awarded the Nobel Prize in Physics in 1918.-Biography:Planck came from a traditional, intellectual family...
had posited in 1900 to arrive at an accurate theory for the distribution of blackbody radiation—an assumption that explained the strange properties of the
photoelectric effectThe photoelectric effect is a phenomenon in which electrons are emitted from matter as a consequence of their absorption of energy from electromagnetic radiation of very short wavelength, such as visible or ultraviolet light. Electrons emitted in this manner may be referred to as "photoelectrons"...
. The Danish physicist
Niels BohrNiels Henrik David Bohr was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...
used this same constant in 1913 to explain the stability of
Rutherford’s atomThe Rutherford model or planetary model is a model of the atom devised by Ernest Rutherford. Rutherford directed the famous Geiger-Marsden experiment in 1909, which suggested to Rutherford's analysis that the Plum pudding model of J. J. Thomson of the atom was incorrect...
as well as the frequencies of light emitted by hydrogen gas.
The radical years: general relativity and quantum mechanics
The gradual acceptance of Einstein’s theories of relativity and the quantized nature of light transmission, and of Niels Bohr’s model of the atom created as many problems as they solved, leading to a full-scale effort to reestablish physics on new fundamental principles. Expanding relativity to cases of accelerating reference frames (the “
general theory of relativityGeneral relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics. It unifies special relativity and Newton's law of universal gravitation, and describes gravity as a...
”) in the 1910s, Einstein posited an equivalence between the inertial force of acceleration and the force of gravity, leading to the conclusion that space is curved and finite in size, and the prediction of such phenomena as
gravitational lensA gravitational lens is formed when the light from a very distant, bright source is "bent" around a massive object between the source object and the observer...
ing and the distortion of time in gravitational fields.
The quantized theory of the atom gave way to a full-scale
quantum mechanicsThe history of quantum mechanics as this interlaces with history of quantum chemistry began essentially with the 1838 discovery of cathode rays by Michael Faraday, during the 1859-1860 winter statement of the black body radiation problem by Gustav Kirchhoff, the 1877 suggestion by Ludwig Boltzmann...
in the 1920s. The quantum theory (which previously relied in the “correspondence” at large scales between the quantized world of the atom and the continuities of the “classical” world) was accepted when the Compton Effect established that light carries momentum and can scatter off particles, and when Louis de Broglie asserted that matter can be seen as behaving as a wave in much the same way as electromagnetic waves behave like particles (wave-particle duality). New principles of a “quantum” rather than a “classical” mechanics, formulated in
matrix-formMatrix mechanics is a formulation of quantum mechanics created by Werner Heisenberg, Max Born, and Pascual Jordan in 1925.Matrix mechanics was the first complete and correct definition of quantum mechanics. It extended the Bohr Model by describing how the quantum jumps occur. It did so by...
by
Werner HeisenbergWerner Heisenberg was a German theoretical physicist who made foundational contributions to quantum mechanics and is best known for asserting the uncertainty principle of quantum theory...
,
Max BornMax Born was a German born physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics and supervised the work of a number of notable physicists in the 1920s and 30s...
, and
Pascual JordanPascual Jordan was a theoretical and mathematical physicist who made significant contributions to quantum mechanics and quantum field theory. He contributed much to the mathematical form of matrix mechanics, and developed canonical anticommutation relations for fermions...
in 1925, were based on the probabilistic relationship between discrete “states” and denied the possibility of
causalityCausality is the relationship between an event and a second event , where the second event is a direct consequence of the first....
.
Erwin SchrödingerErwin Rudolf Josef Alexander Schrödinger was an Austrian theoretical physicist who achieved fame for his contributions to quantum mechanics, especially the Schrödinger equation, for which he received the Nobel Prize in 1933...
established an equivalent theory based on waves in 1926; but Heisenberg’s 1927 “
uncertainty principleIn quantum mechanics, the Heisenberg uncertainty principle states that certain pairs of physical properties, like position and momentum, cannot both be known to arbitrary precision. That is, the more precisely one property is known, the less precisely the other can be known...
” (indicating the impossibility of precisely and simultaneously measuring position and
momentumIn classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section "modern definitions of momentum" on this page...
) and the “
Copenhagen interpretationThe Copenhagen interpretation is an interpretation of quantum mechanics. A key feature of quantum mechanics is that the state of every particle is described by a wavefunction, which is a mathematical representation used to calculate the probability for it to be found in a location or a state of...
” of quantum mechanics (named after Bohr’s home city) continued to deny the possibility of fundamental causality, though opponents such as Einstein would assert that “God does not play dice with the universe”. Also in the 1920s,
Satyendra Nath BoseSatyendra Nath Bose , FRS, was an Indian physicist, specializing in mathematical physics. He is best known for his work on quantum mechanics in the early 1920s, providing the foundation for Bose-Einstein statistics and the theory of the Bose-Einstein condensate...
's work on
photonIn physics, a photon is an elementary particle, the quantum of the electromagnetic field and the basic "unit" of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s and quantum mechanics provided the foundation for Bose-Einstein statistics, the theory of the Bose-Einstein condensate, and the discovery of the
bosonIn particle physics, bosons are particles which obey Bose–Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein. In contrast to fermions, which obey Fermi-Dirac statistics, several bosons can occupy the same quantum state. Thus, bosons with the same energy can occupy the...
.
Constructing a new fundamental physics
As the philosophically inclined continued to debate the fundamental nature of the universe, quantum theories continued to be produced, beginning with
Paul Dirac’sPaul Adrien Maurice Dirac, OM, FRS was a British theoretical physicist. Dirac made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics...
formulation of a relativistic quantum theory in 1928. However, attempts to quantize electromagnetic theory entirely were stymied throughout the 1930s by theoretical formulations yielding infinite energies. This situation was not considered adequately resolved until after
World War IIWorld War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...
ended, when
Julian SchwingerJulian Seymour Schwinger was an American theoretical physicist. He is best known for his work on the theory of quantum electrodynamics, in particular for developing a relativistically invariant perturbation theory, and for renormalizing QED to one loop order.Schwinger is recognized as one of the...
,
Richard FeynmanRichard Phillips Feynman was an American physicist known for the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as work in particle physics...
, and
Sin-Itiro TomonagaSin-Itiro Tomonaga or Shin'ichirō Tomonaga was a Japanese physicist, influential in the development of quantum electrodynamics, work for which he was jointly awarded the Nobel Prize in Physics in 1965 along with Richard Feynman and Julian Schwinger.-Biography:Tomonaga was born in Tokyo in 1906...
independently posited the technique of “
renormalizationIn quantum field theory, the statistical mechanics of fields, and the theory of self-similar geometric structures, renormalization refers to a collection of techniques used to take a continuum limit....
”, which allowed for an establishment of a robust
quantum electrodynamicsQuantum electrodynamics is a relativistic quantum field theory of electrodynamics. QED was developed by a number of physicists, beginning in the late 1920s. It basically describes how light and matter interact. More specifically it deals with the interactions between electrons, positrons and photons...
(Q.E.D.).
Meanwhile, new theories of
fundamental particlesIn particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...
proliferated with the rise of the idea of the
quantization of fieldsQuantum field theory provides a theoretical framework for constructing quantum mechanical models of systems classically described by fields or of many-body systems. It is widely used in particle physics and condensed matter physics...
through “
exchange forcesIn physics, the exchange interaction is a quantum mechanical effect which increases or decreases the expectation value of the energy or distance between two or more identical particles when their wave functions overlap...
” regulated by an exchange of short-lived
“virtual” particlesIn physics, a virtual particle is a particle that exists for a limited time and space, introducing uncertainty in their energy and momentum due to the Heisenberg Uncertainty Principle...
, which were allowed to exist according to the laws governing the uncertainties inherent in the quantum world. Notably,
Hideki Yukawané , was a Japanese theoretical physicist and the first Japanese Nobel laureate.-Biography:Yukawa was born in Tokyo, Japan. In 1929, after receiving his degree from Kyoto Imperial University, he stayed on as a lecturer for four years. After graduation, he was interested in theoretical physics,...
proposed that the positive charges of the
nucleusThe nucleus is the very dense region consisting of nucleons at the center of an atom. Almost all of the mass in an atom is made up from the protons and neutrons in the nucleus, with a very small contribution from the orbiting electrons....
were kept together courtesy of a powerful but short-range force mediated by a particle intermediate in mass between the size of an
electronAn electron is a subatomic particle that carries a negative electric charge. It has no known substructure and is believed to be a point particle. An electron has a mass that is approximately 1836 times less than that of the proton. The intrinsic angular momentum of the electron is a half integer...
and a
protonThe proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom but is also stable by itself and has a second identity as the hydrogen ion, H
+...
. This particle, called the “
pionIn particle physics, a pion is any of three subatomic particles: , and . Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force.-Basic properties:...
”, was identified in 1947, but it was part of a slew of particle discoveries beginning with the
neutronThe neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutron are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a...
, the “
positronThe positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin of , and the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production...
” (a positively-charged “
antimatterIn particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles...
” version of the electron), and the “
muonThe muon is an elementary particle similar to the electron, with negative electric charge and a spin of . Together with the electron, the tauon, and the three neutrinos, it is classified as a lepton. It is the unstable subatomic particle with the second longest mean lifetime , behind the neutron...
” (a heavier relative to the electron) in the 1930s, and continuing after the war with a wide variety of other particles detected in various kinds of apparatus:
cloud chamberThe cloud chamber, also known as the Wilson chamber, is used for detecting particles of ionizing radiation. In its most basic form, a cloud chamber is a sealed environment containing a supercooled, supersaturated water or alcohol vapour. When an alpha particle or beta particle interacts with the...
s,
nuclear emulsionA nuclear emulsion plate is a photographic plate with a particularly thick emulsion layer and with a very uniform grain size. Nuclear emulsions can be used to record and investigate fast charged particles like nucleons or mesons...
s,
bubble chamberA bubble chamber is a vessel filled with a superheated transparent liquid used to detect electrically charged particles moving through it. It was invented in 1952 by Donald A. Glaser, for which he was awarded the 1960 Nobel Prize in Physics...
s, and
coincidence countersIn physics, a coincidence circuit is an electronic device with one output and two inputs. The output is activated only when signals are received at the same time at both inputs...
. At first these particles were found primarily by the
ionizedIonization is the physical process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation ....
trails left by
cosmic rayCosmic rays are energetic particles originating from outer space that impinge on Earth's atmosphere. Almost 90% of all the incoming cosmic ray particles are protons, almost 10% are helium nuclei , and slightly under 1% are heavier elements and electrons...
s, but were increasingly produced in newer and more powerful
particle acceleratorA particle accelerator is a device that uses electric fields to propel ions or charged subatomic particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator...
s.
The interaction of these particles by “
scatteringScattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of...
” and “
decayParticle decay is the spontaneous process of one elementary particle transforming into other elementary particles. During this process, an elementary particle becomes a different particle with less mass and an intermediate particle such as W boson in muon decay. The intermediate particle then...
” provided a key to new fundamental quantum theories.
Murray Gell-MannMurray Gell-Mann is an American physicist who received the 1969 Nobel Prize in physics for his work on the theory of elementary particles....
and
Yuval Ne'emanYuval Ne'eman , was an Israeli soldier, physicist and politician, serving as a Minister during the 1980s and early 1990s. He was a self-declared atheist.-Background:...
brought some order to these new particles by classifying them according to certain qualities, beginning with what Gell-Mann referred to as the “
Eightfold WayIn physics, the Eightfold Way is a term coined by American physicist Murray Gell-Mann for a theory organizing subatomic baryons and mesons into octets...
”, but proceeding into several different “octets” and “decuplets” which could predict new particles, most famously the , which was detected at
Brookhaven National LaboratoryBrookhaven National Laboratory , is a United States national laboratory located in Upton, New York on Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base...
in 1964, and which gave rise to the “
quarkA quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never found in...
” model of
hadronIn particle physics, a hadron is a particle made of quarks held together by the strong force . Hadrons are either mesons or baryons...
composition. While the
quark modelIn physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks which give rise to the quantum numbers of the hadrons. These quantum numbers are labels identifying the hadrons, and are of two kinds...
at first seemed inadequate to describe
strong nuclear forcesIn particle physics, the strong interaction holds quarks and gluons together to form protons, neutrons and other particles. The strong interaction is one of the four fundamental interactions, along with gravitation, the electromagnetic force and the weak interaction...
, allowing the temporary rise of competing theories such as the S-Matrix, the establishment of
quantum chromodynamicsIn theoretical physics, Quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons . It is the study of the SU Yang–Mills theory of color-charged fermions...
in the 1970s finalized a set of fundamental and exchange particles, which allowed for the establishment of a “
standard modelThe Standard Model of particle physics is a theory of three of the four known fundamental interactions and the elementary particles that take part in these interactions. These particles make up all visible matter in the universe...
” based on the mathematics of
gauge invarianceGauge invariance is the property of a field theory in which different configurations of the underlying fundamental but unobservable fields result in identical observable quantities. A theory with such a property is called a gauge theory...
, which successfully described all forces except for gravity, and which remains generally accepted within the domain to which it is designed to be applied.
The “standard model” groups the
electroweak interactionIn particle physics, the electroweak interaction is the unified description of two of the four fundamental interactions of nature: electromagnetism and the weak interaction. Although these two forces appear very different at everyday low energies, the theory models them as two different aspects of...
theory and
quantum chromodynamicsIn theoretical physics, Quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons . It is the study of the SU Yang–Mills theory of color-charged fermions...
into a structure denoted by the gauge group
SU(3)×SU(2)×U(1). The formulation of the unification of the electromagnetic and
weak interactionThe weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons...
s in the standard model is due to
Abdus SalamAbdus Salam was a Pakistani theoretical physicist, astrophysicist and Nobel laureate in Physics for his work in Electro-Weak Theory. Salam, Sheldon Glashow and Steven Weinberg shared the prize for this discovery...
,
Steven WeinbergSteven Weinberg is an American physicist and Nobel laureate in Physics for his contributions with Abdus Salam and Sheldon Glashow to the unification of the weak force and electromagnetic interaction between elementary particles.
...
and, subsequently, Sheldon Glashow. After the discovery, made at
CERNThe European Organization for Nuclear Research , known as CERN , , is the world's largest particle physics laboratory, situated in the northwest suburbs of Geneva on the Franco–Swiss border, established in 1954...
, of the existence of
neutral weak currentsWeak neutral current interactions are one of the ways in which subatomic particles can interact by means of the weak force. These interactions are mediated by the boson, and the interaction is called 'neutral' because the has no electric charge...
, mediated by the
{{histOfScience}}
As forms of scienceScience is in its broadest sense to any systematic knowledge-base or prescriptive practice that is capable of resulting in a prediction or predictable type of outcome...
historically developed out of
philosophyPhilosophy is the study of general and fundamental problems concerning matters such as existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing these questions by its critical, generally systematic approach and its reliance on reasoned...
,
physicsPhysics is a natural science; it is the study of matter and its motion through spacetime and all that derives from these, such as energy and force...
(
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
: φύσις
physisPhysis is a Greek theological, philosophical, and scientific term usually translated into English as "nature". In the Odyssey, Homer uses the word once , referring to the intrinsic way of growth of a particular species of plant...
"
natureNature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general...
") was originally referred to as
natural philosophyNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
, a term describing a field of study concerned with "the workings of nature".
Early history
{{see|History of astronomy|Aristotelian physics}}
Drawing elements from various areas of exploration including Babylonian Astronomy, early attempts at
opticsOptics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
and
mechanicsMechanics is the branch of physics concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effect of the bodies on their environment....
, and
geometryGeometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers....
, the move towards a rational understanding of nature began at least since the Archaic Period in Greece (650 BC – 480 BC) with the Presocratics. Accordingly,
LeucippusLeucippus or Leukippos was the first Greek to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms — which was elaborated in far greater detail by his pupil and successor, Democritus...
(
Greek:Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
{{Polytonic|Λεύκιππος}}, first half of 5th century BC), refusing to accept various supernatural, religious or mythological explanations for natural
phenomenaA phenomenon is any observable occurrence. In popular usage, a phenomenon often refers to an extraordinary event. In scientific usage, a phenomenon is any event that is observable, however commonplace it might be, even if it requires the use of instrumentation to observe it...
, proclaimed that every event had a natural cause. He went on to develop the theory of
atomismAtomism is a natural philosophy developed by Leucippus and his student Democritus in the fifth century BC. These atomists theorized that the natural world consists of two fundamental and opposite, indivisible bodies - atoms and void...
— the idea that everything is composed entirely of various imperishable, indivisible elements called
atomThe atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s. This was elaborated in great detail by
DemocritusDemocritus was an Ancient Greek philosopher born in Abdera in the north of Greece. He was the most prolific, and ultimately the most influential, of the pre-Socratic philosophers; his atomic theory may be regarded as the culmination of early Greek thought.His exact contributions are difficult to...
.
AristotleAristotle was a Greek philosopher, a student of Plato and teacher of Alexander the Great. He wrote on many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, politics, government, ethics, biology, and zoology.Together with Plato and Socrates , Aristotle is one of...
({{lang-el|Ἀριστοτέλης}},
Aristotélēs) (384 BC – 322 BC), a student of
PlatoPlato , was a Classical Greek philosopher, mathematician, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world...
, promoted the concept that observation of physical phenomena could ultimately lead to the discovery of the natural laws governing them. He wrote the first work which refers to that line of study as "Physics" (
Aristotle's PhysicsPhysics is an important work by Aristotle. It is a collection of treatises or lessons that deal with the most general principles of moving things, both living and non-living, rather than physical theories or investigations of the particular contents of the universe...
). During the
classical periodClassical Greece was a culture that was highly advanced and which heavily influenced the cultures of Ancient Rome and still has an enduring effect on Western Civilization. Much of modern politics, artistic thought, scientific thought, literature, and philosophy derives from this ancient society...
in Greece (6th, 5th and 4th centuries BC) and in
Hellenistic timesHellenistic civilization represents the zenith of Greek influence in the ancient world from 323 BC to about 146 BC ; note, however that Koine Greek language and Hellenistic philosophy and religion are also indisputably elements of the Roman era till Late Antiquity...
,
natural philosophyNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
slowly developed into an exciting and contentious field of study.
Early in Classical Greece, that the earth is a
sphereA sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...
("round"), was generally known by all, and around 240 BCE,
EratosthenesEratosthenes of Cyrene was a Greek mathematician, elegiac poet, athlete, geographer, and astronomer. He made several discoveries and inventions including a system of latitude and longitude...
(276 BCE - 194 BCE) accurately estimated its circumference. In contrast to Aristotle's geocentric views,
Aristarchus of SamosAristarchus was a Greek astronomer and mathematician, born on the island of Samos, in Greece. He was the first person to present an explicit argument for a heliocentric model of the solar system, placing the Sun, not the Earth, at the center of the known universe...
({{lang-el|Ἀρίσταρχος}};
310 BC-Seleucid Empire:* Antigonus orders Nicanor, one of his generals, to invade Babylonia from the east and his son Demetrius Poliorcetes to attack it from the west. Nicanor assembles a large force but it is surprised and defeated by Seleucus at the river Tigris, and his troops are either cut to pieces...
– ca.
230 BC-Anatolia:* The city of Pergamum is attacked by the Galatians because the leader of Pergamum, Attalus I Soter, has refused to pay them the customary tribute. Attalus crushes his enemy in a battle outside the walls of his city and to mark the success he takes the title of king and the name...
) presented an explicit argument for a
heliocentric modelIn astronomy, heliocentrism is the theory that the Sun is stationary and at the center of the universe. The word came from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center. Discussions on the possibility of heliocentrism date to classical...
of the
solar systemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
, placing the
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
, not the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
, at the centre.
Seleucus of SeleuciaSeleucus of Seleucia was a Hellenistic astronomer and philosopher from the Seleucia region of Mesopotamia who supported the heliocentric theory of planetary motion. Seleucus is known from the writings of Plutarch, Strabo and Aetius...
, a follower of the heliocentric theory of Aristarchus, stated that the Earth rotated around its own axis, which in turn revolved around the Sun. Though the arguments he used were lost,
PlutarchPlutarch, born Plutarchos then, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. AD 46 – 120, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...
stated that Seleucus was the first to prove the heliocentric system through reasoning.
Many contributions were made by many thinkers, including
ArchimedesArchimedes of Syracuse was a Greek mathematician, physicist, engineer, inventor, and astronomer. Although few details of his life are known, he is regarded as one of the leading scientists in classical antiquity...
({{lang-el|Ἀρχιμήδης}}) (c. 287 BC – c. 212 BC) of
"Eureka!"Eureka may refer to* Eureka , a famous exclamation attributed to Archimedes- Canada :* Eureka, Nova Scotia in Canada* Eureka, Nunavut in Canada* Eureka Sound, Nunavut, Canada...
fame, who also defined the concept of the centre of gravity and created the field of statics and
PtolemyClaudius Ptolemaeus , known in English as Ptolemy , was a Roman citizen of Greek ancestry. He was a mathematician, astronomer, geographer, astrologer and a poet of a single epigram in the Greek Anthology. He lived in Egypt under the Roman Empire, and is believed to have been born in the town of...
(Claudius Ptolemaeus (
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
: {{polytonic|Κλαύδιος Πτολεμαίος}}) who wrote scientific treatises that were later used as the basis of much later science.
Much of the accumulated knowledge of the ancient world was lost. Even of the works of the better known thinkers, few fragments survived. Although he wrote at least fourteen books, almost nothing of
HipparchusHipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...
' direct work survived. Of the 150 reputed
AristotelianAristotelianism is a tradition of philosophy that takes its defining inspiration from the work of Aristotle. Aristotelianism is understood by its proponents as critically developing Plato’s theories. Most particularly, Aristotelianism brings Plato’s ideals down to Earth as goals and goods internal...
works, only 30 exist, and some of those are "little more than lecture notes". Though reinterpreted to fit theological concerns, both
Jewish Jewish philosophy refers to the conjunction between serious study of philosophy, Jewish scholasticism and Jewish theology. In one sense, it refers to all philosophical activity carried out by Jews or in relation to the religion of Judaism...
and
IslamicIslamic philosophy is a branch of Islamic studies, and is a longstanding attempt to create harmony between philosophy and the religious teachings of Islam .-Definition:...
scholarship preserved and developed some of the ancient knowledge that would otherwise have been lost (Judeo-Islamic philosophies (800 - 1400)).
The
IslamIslam Islam Islam ( al-’islām,
[There are ten pronunciations of Islam in English, differing in whether the first or second syllable has the stress, whether the s is or , and whether the a is pronounced as in father, as in cat, or (when the stress is on the i) as in the a of sofa...]
ic
AbbasidThe Abbasid Caliphate was the third of the Islamic Caliphates of the Islamic Empire. It was ruled by the Abbasid dynasty of caliphs, who built their capital in Baghdad after overthrowing the Umayyad caliphs from all but Al Andalus....
caliphThe Caliph is the head of state in a Caliphate, and the title for the leader of the Islamic Ummah, an Islamic community ruled by the Shari'ah. It is a transliterated version of the Arabic word which means "successor" or "representative"...
s gathered many classic works of antiquity and had them translated into Arabic.
Islamic philosophersIslamic philosophy is a branch of Islamic studies, and is a longstanding attempt to create harmony between philosophy and the religious teachings of Islam .-Definition:...
such as
Al-Kindi' , also known to the West by the Latinized version of his name Alkindus, was an Arab Iraqi polymath: an Islamic philosopher, scientist, astrologer, astronomer, cosmologist, chemist, logician, mathematician, musician, physician, physicist, psychologist, and meteorologist...
(Alkindus),
Al-FarabiAbū Naṣr al-Fārābi , known in the West as Alpharabius Abū Naṣr al-Fārābi (أبو نصر محمد الفارابي - Abū Naṣr Muḥammad al-Fārābi; in some sources also mentioned as محمد بن محمد بن أوزلغ الفارابي - Muḥammad ibn Muḥammad (ibn Tarḫān) ibn Awzlaġ al-Fārābi), known in the West as...
(Alpharabius),
Avicenna, known as Abū Alī Sīnā or Ibn Sīnā , and commonly known in English by his Latinized name Avicenna , was a Persian polymath and the foremost physician and philosopher of his time...
(Ibn Sina) and
AverroesAbū 'l-Walīd Muḥammad ibn Aḥmad ibn Rushd , better known just as Ibn Rushd , and in European literature as Averroes , was an Andalusian Muslim polymath of Moroccan origins; a master of Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music...
(Ibn Rushd) reinterpreted Greek though in the context of their religion. Important contributions were made by Ibn al-Haytham and Abū Rayhān Bīrūnī before eventually passing on to
Western EuropeWestern Europe is the collection of countries in the westernmost region of Europe, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a cultural entity—the region lying west of Central Europe...
where they were studied by scholars such as
Roger BaconRoger Bacon, O.F.M. , also known as Doctor Mirabilis , was an English philosopher and Franciscan friar who placed considerable emphasis on empiricism...
and
WiteloWitelo - also known as Erazmus Ciolek Witelo, Witelon, Vitellio, Vitello, Vitello Thuringopolonis, Vitulon, Erazm Ciołek, , was a Silesian and Polish friar, theologian and scientist: physicist, natural philosopher, mathematician...
.
Awareness of ancient works re-entered the West through translations from Arabic to Latin. Their re-introduction, combined with
Judeo-IslamicThe historical interaction of Judaism and Islam started in the 7th century AD with the origin and spread of Islam in the Arabian peninsula. Because Judaism and Islam share a common origin in the Middle East through Abraham, both are considered Abrahamic religions...
theological commentaries, had a great influence on
Medieval philosophersMedieval philosophy is the philosophy of Europe and the Middle East in the era now known as medieval or the Middle Ages, the period roughly extending from the fall of the Roman Empire in the fifth century A.D. to the Renaissance in the sixteenth century...
such as
Thomas AquinasSaint Thomas Aquinas, O.P. was a priest of the Roman Catholic Church in the Dominican Order from Italy, and an immensely influential philosopher and theologian in the tradition of scholasticism, known as Doctor Angelicus and Doctor Communis...
.
Scholastic European scholarsScholasticism is derived from the Latin word scholasticus , which means "that [which] belongs to the school," and was a method of learning taught by the academics of medieval universities circa 1100–1500...
, who sought to reconcile the philosophy of the ancient classical philosophers with
Judeo-ChristianJudeo–Christian is a term used in the United States, broadly to describe a body of concepts and values thought to be held in common by Judaism and Christianity...
theology, proclaimed Aristotle the greatest thinker of the ancient world. In cases where they didn't directly contradict the Bible,
Aristotelian physicsThe Greek philosopher Aristotle developed many theories on the nature of physics. These involved what Aristotle described as the four elements...
became the foundation for the physical explanations of the European Churches.
Based on Aristotelian physics, Scholastic physics described things as moving according to their essential nature. Celestial objects were described as moving in circles, because perfect circular motion was considered an innate property of objects that existed in the uncorrupted realm of the
celestial spheresThe celestial spheres, or celestial orbs, were the fundamental celestial entities of the cosmological celestial mechanics first invented by Eudoxus, and developed by Aristotle, Ptolemy, Copernicus and others...
. The
theory of impetusThe theory of impetus was an auxiliary or secondary theory of Aristotelian dynamics, put forth initially to explain projectile motion against gravity. It was first introduced by Hipparchus in antiquity, and subsequently further developed by John Philoponus in the 6th century AD...
, the ancestor to the concepts of
inertiaInertia is the resistance of any physical object, to a change in its state of motion. It is represented numerically by an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by...
and
momentumIn classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section "modern definitions of momentum" on this page...
, was developed along similar lines by
medieval philosophersMedieval philosophy is the philosophy of Europe and the Middle East in the era now known as medieval or the Middle Ages, the period roughly extending from the fall of the Roman Empire in the fifth century A.D. to the Renaissance in the sixteenth century...
such as
John PhiloponusJohn Philoponus , also known as John the Grammarian or John of Alexandria, was a Christian and Aristotelian commentator and the author of a considerable number of philosophical treatises and theological works...
,
Avicenna, known as Abū Alī Sīnā or Ibn Sīnā , and commonly known in English by his Latinized name Avicenna , was a Persian polymath and the foremost physician and philosopher of his time...
and
Jean BuridanJean Buridan was a French priest who sowed the seeds of the Copernican revolution in Europe. Although he was one of the most famous and influential philosophers of the late Middle Ages, he is today among the least well known...
. Motions below the lunar sphere were seen as imperfect, and thus could not be expected to exhibit consistent motion. More idealized motion in the “sublunary” realm could only be achieved through artifice, and prior to the 17th century, many did not view artificial experiments as a valid means of learning about the natural world. Physical explanations in the sublunary realm revolved around tendencies. Stones contained the element earth, and earthy objects tended to move in a straight line toward the centre of the earth (and the universe in the Aristotelian geocentric view) unless otherwise prevented from doing so.
{{see|History of science and technology in China|History of Indian science and technology}}
Important physical and mathematical traditions also existed in
ancient ChineseThe history of science and technology in China is both long and rich with many contributions to science and technology. In antiquity, independently of Greek philosophers and other civilizations, ancient Chinese philosophers made significant advances in science, technology, mathematics, and...
and Indian sciences. In
Indian philosophyThe term Indian philosophy , may refer to any of several traditions of philosophical thought that originated in the Indian subcontinent, including Hindu philosophy, Buddhist philosophy, and Jain philosophy...
, Kannada of the
VaisheshikaVaisheshika, or ', is one of the six Hindu schools of philosophy of India. Historically, it has been closely associated with the Hindu school of logic, Nyaya....
school proposed the theory of atomism during the 1st millenium BC, and it was further elaborated on by the
Buddhist atomistsBuddhist atomism is a school of atomistic Buddhist philosophy that flourished on the Indian subcontinent during two major periods. During the first phase, which began to develop prior to the 4th century BCE, Buddhist atomism had a very qualitative, Aristotelian-style atomic theory. This form of...
DharmakirtiDharmakirti , was an Indian scholar and one of the Buddhist founders of Indian philosophical logic. He was one of the primary theorists of Buddhist atomism, according to which the only items considered to exist are momentary Buddhist atoms and states of consciousness.-History:Born around the turn...
and
DignāgaDignāga was an Indian scholar and one of the Buddhist founders of Indian logic....
during the 1st millenium AD. In Indian astronomy,
AryabhataAryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...
's
AryabhatiyaĀryabhatīya, an astronomical treatise, is the magnum opus and only extant work of the 5th century Indian mathematician, Aryabhata.- Structure and style:...
(499 AD) proposed the Earth's rotation, while
Nilakantha SomayajiNilakantha Somayaji , from Kerala, was a major Indian mathematician and astronomer of the Kerala school of astronomy and mathematics and was a student of Damodara. Later, he lived in Tryambakeshwar. Among his many influential books, he wrote the comprehensive astronomical treatise Tantrasamgraha...
(1444-1544) of the Kerala school of astronomy and mathematics proposed a semi-heliocentric model resembling the
Tychonic systemThe Tychonic system was a model of the solar system published by Tycho Brahe in the late 16th century which combined what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system. The model may have been inspired by Paul...
. In
Chinese philosophyChinese philosophy is philosophy written in the Chinese tradition of thought. Chinese philosophy has a history of several thousand years; its origins are often traced back to the Yi Jing , an ancient compendium of divination, which uses a system of 64 hexagrams to guide action...
,
MoziMozi , original name Mo Di , was a philosopher who lived in China during the Hundred Schools of Thought period ，born in Tengzhou, Shandong Province. He founded the school of Mohism and argued strongly against Confucianism and Daoism...
(c. 470-390 BC) proposed a concept similar to
inertiaInertia is the resistance of any physical object, to a change in its state of motion. It is represented numerically by an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by...
, while in optics,
Shen KuoShen Kuo or Shen Gua , style name Cunzhong and pseudonym Mengqi Weng , was a polymathic Chinese scientist and statesman of the Song Dynasty...
(1031–1095 AD) independently developed a
camera obscuraThe camera obscura is an optical device that projects an image of its surroundings on a screen. It is used in drawing and for entertainment, and was one of the inventions that led to photography. The device consists of a box or room with a hole in one side...
.
Emergence of experimental method and physical optics
{{see|History of optics}}
The use of
empiricalThe word empirical denotes information gained by means of observation, experience, or experiment. A central concept in science and the scientific method is that all evidence must be empirical, or empirically based, that is, dependent on evidence or consequences that are observable by the senses...
experiments in
geometrical opticsGeometrical optics, or ray optics, describes light propagation in terms of "rays". The "ray" in geometric optics is an abstraction, or "instrument", which can be used to approximately model how light will propagate. Light rays bend at the interface between two dissimilar media, and may curve in a...
dates back to second century Roman Egypt, where
PtolemyClaudius Ptolemaeus , known in English as Ptolemy , was a Roman citizen of Greek ancestry. He was a mathematician, astronomer, geographer, astrologer and a poet of a single epigram in the Greek Anthology. He lived in Egypt under the Roman Empire, and is believed to have been born in the town of...
carried out several
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
s on
reflectionIn mathematics, a reflection is a map that transforms an object into its mirror image. For example, a reflection of the small English letter p in respect to a vertical line would look like q...
,
refractionRefraction is the change in direction of a wave due to a change in its velocity. This is most commonly observed when a wave passes from one medium to another...
and
binocular visionBinocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...
. However, he either discarded or
rationalizedIn psychology and logic, rationalization is the process of constructing a logical justification for a belief, decision, action or lack thereof that was originally arrived at through a different mental process...
any empirical data that did not support his
PlatonicPlatonism is the philosophy of Plato or the name of other philosophical systems considered closely derived from it. In a narrower sense the term might indicate the doctrine of Platonic realism. The central concept of Platonism is the Theory of Forms: the transcendent, perfect archetypes, of which...
paradigm. Experiments did not hold any importance at the time, and empirical evidence was thus seen as secondary to general theory. The incorrect
emission theory of visionEmission theory or extramission theory is the proposal that visual perception is accomplished by rays of light emitted by the eyes. This theory has been replaced by intromission theory, which states that visual perception comes from something representative of the object entering the eyes...
thus continued to dominate optics through to the 10th century.
{{see|History of scientific method|Science in the Middle Ages|Physics in medieval Islam}}
The turn of the
second millenniumBeethoven|Te Kooti|- align="left"!20th Century|Nelson Mandela
Paul Rusesabagina|Martin Luther King, Jr.
Franklin D...
saw the development of an
experimental methodScientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and measurable evidence subject to specific...
emphasizing the role of
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
ation as a form of proof for scientific inquiry together with the development of
physical opticsIn physics, physical optics, or wave optics, is the branch of optics which studies interference, diffraction, polarization, and other phenomena for which the ray approximation of geometric optics is not valid...
where mathematics and geometry were combined with the philosophical field of physics. The Iraqi physicist, Ibn al-Haytham (Alhazen), is considered a central figure in this shift in physics from a philosophical activity to an experimental and mathematical one, and the shift in optics from a mathematical discipline to a physical and experimental one. Due to his
positivistPositivism is a philosophy that holds that the only authentic knowledge is that which is based on actual sense experience. Metaphysical speculation is avoided...
approach, his
Doubts Concerning Ptolemy insisted on
scientific demonstrationA scientific demonstration is a scientific experiment carried out for the purposes of demonstrating scientific principles, rather than for hypothesis testing or knowledge gathering ....
and criticized Ptolemy's
confirmation biasConfirmation bias is an irrational tendency to search for, interpret or remember information in a way that confirms preconceptions or working hypotheses. It is a type of cognitive bias and a systematic error of inductive reasoning...
and
conjecturalA conjecture is a proposition which is presumed to be real, true, or genuine, mostly based on inconclusive grounds. Karl Popper pioneered the use of the term "conjecture" in scientific philosophy. Conjecture is contrasted by hypothesis , which is a testable statement based on accepted grounds...
undemonstrated theories. His
Book of OpticsThe Book of Optics was a seven-volume treatise on optics, physics, mathematics, anatomy and psychology written by the Iraqi Muslim scientist, Ibn al-Haytham , from 1011 to 1021, when he was under house arrest in Cairo, Egypt.The book...
(1021) was the earliest successful attempt at unifying a mathematical discipline (geometrical optics) with the philosophical field of physics, to create the modern science of physical optics. An important part of this was the intromission theory of
visionVisual perception is the ability to interpret information and surroundings from visible light reaching the eye. The resulting perception is also known as eyesight, sight or vision...
, which in order to prove, he developed an experimental method to test his hypothesis. He conducted various experiments to prove his intromission theory and other hypotheses on light and vision. The
Book of Optics established experimentation as the norm of proof in optics, and gave optics a physico-mathematical conception at a much earlier date than the other mathematical disciplines. His
On the Light of the Moon also attempted to combine mathematical astronomy with physics, a field now known as
astrophysicsAstrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects such as galaxies, stars, planets, exoplanets, and the interstellar medium, as well as their...
, to formulate several astronomical hypotheses which he proved through experimentation.
Galileo Galilei and the rise of physico-mathematics
{{main|Galileo Galilei}}
In the 17th century,
natural philosophersNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
began to mount a sustained attack on the
ScholasticScholasticism is derived from the Latin word scholasticus , which means "that [which] belongs to the school," and was a method of learning taught by the academics of medieval universities circa 1100–1500...
philosophical program, and supposed that mathematical descriptive schemes adopted from such fields as mechanics and astronomy could actually yield universally valid characterizations of motion. The
TuscanThe Grand Duchy of Tuscany was a central Italian monarchy that existed, with Interruptions, from 1569 to 1859, replacing the Duchy of Florence...
mathematician
Galileo GalileiGalileo Galilei was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations, and support for Copernicanism...
was the central figure in the shift to this perspective. As a mathematician, Galileo’s role in the
universityEuropean research universities have a long history that arguably dates back to the founding of the University of Bologna in 1088, although the University of Paris and the University of Magnaura are other contenders for this position...
culture of his era was subordinated to the three major topics of study:
lawLaw is a system of rules, usually enforced through a set of institutions. It shapes politics, economics and society in numerous ways and serves as a primary social mediator of relations between people. Contract law regulates everything from buying a bus ticket to trading on derivatives markets...
,
medicineMedicine is the art and science of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, and
theologyThe term "theology" literally means the study of God, deriving from the Greek word theos, meaning 'God', and the suffix -ology from the Greek word logos meaning "discourse", "theory", or "reasoning"...
(which was closely allied to philosophy). Galileo, however, felt that the descriptive content of the technical disciplines warranted philosophical interest, particularly because mathematical analysis of astronomical observations—notably the radical analysis offered by astronomer
Nicolaus CopernicusNicolaus Copernicus was the first astronomer to formulate a comprehensive heliocentric cosmology, which displaced the Earth from the center of the universe...
concerning the relative motions of the sun, earth, moon, and planets—indicated that philosophers’ statements about the nature of the universe could be shown to be in error. Galileo also performed mechanical experiments, and insisted that motion itself—regardless of whether that motion was natural or artificial—had universally consistent characteristics that could be described mathematically.
Galileo used his 1609 telescopic discovery of the
moons of JupiterThe Galilean moons are the four moons of Jupiter discovered by Galileo Galilei on January 7, 1610. They are the largest of the many moons of Jupiter and derive their names from the lovers of Zeus: Io, Europa, Ganymede and Callisto. Ganymede, Europa and Io participate in a 1:2:4 orbital resonance...
, as published in his
Sidereus NunciusSidereus Nuncius is a short treatise published in New Latin by Galileo Galilei in March 1610. It was the first scientific treatise based on observations made through a telescope...
in 1610, to procure a position in the
MediciThe House of Medici was a political dynasty, banking family and later royal house who first began to gather prominence under Cosimo de' Medici in the Republic of Florence during the late 14th century. The family originated in the Mugello region of the Tuscan countryside, gradually rising until...
court with the dual title of mathematician and philosopher. As a court philosopher, he was expected to engage in debates with philosophers in the Aristotelian tradition, and received a large audience for his own publications, such as
The AssayerThe Assayer was a book published in Rome by Galileo Galilei in October 1623.The book was a polemic against the treatise on the comets of 1618 by Orazio Grassi, a Jesuit mathematician at the Collegio Romano. In this matter Grassi, for all his Aristotelianism, was right and Galileo was wrong...
and
Discourses and Mathematical Demonstrations Concerning Two New SciencesThe Discourses and Mathematical Demonstrations Relating to Two New Sciences was Galileo's final book and a sort of scientific testament covering much of his work in physics over the preceding thirty years.Unlike the Dialogue Concerning the Two Chief World Systems, it was not published with a license...
, which was published abroad after he was placed under house arrest for his publication of
Dialogue Concerning the Two Chief World SystemsThe Dialogue Concerning the Two Chief World Systems was a 1632 Italian language book by Galileo Galilei comparing the Copernican system with the traditional Ptolemaic system...
in 1632.
Galileo’s interest in the mechanical experimentation and mathematical description in motion established a new natural philosophical tradition focused on experimentation. This tradition, combining with the non-mathematical emphasis on the collection of "experimental histories" by philosophical reformists such as
William GilbertWilliam Gilbert, also known as Gilbard, was an English physician and natural philosopher. He was an early Copernican, and passionately rejected both the prevailing Aristotelian philosophy and the Scholastic method of university teaching...
and
Francis BaconFrancis Bacon,1st Viscount St Alban KC , son of Nicholas Bacon by his second wife Anne Bacon, was an English philosopher, statesman, scientist, lawyer, jurist, and author. He served both as Attorney General and Lord Chancellor of England...
, drew a significant following in the years leading up to and following Galileo’s death, including
Evangelista TorricelliEvangelista Torricelli was an Italian physicist and mathematician, best known for his invention of the barometer.-Biography:Torricelli was born in Faenza, then part of the Papal States...
and the participants in the
Accademia del CimentoThe Accademia del Cimento , an early scientific society, was founded in Florence 1657 by students of Galileo, Evangelista Torricelli and Vincenzo Viviani. The foundation of Academy was funded by Prince Leopoldo and Grand Duke Ferdinando II de' Medici. Giovanni Borelli and Nicolaus Steno were also...
in Italy;
Marin MersenneMarin Mersenne, Marin Mersennus or le Père Mersenne was a French theologian, philosopher, mathematician and music theorist, often referred to as the "father of acoustics" .-Life:...
and
Blaise Pascal Blaise Pascal , was a French mathematician, physicist, and religious philosopher. He was a child prodigy who was educated by his father, a civil servant...
in France;
Christiaan HuygensChristiaan Huygens, FRS was a prominent Dutch mathematician, astronomer, physicist, horologist, and writer of early science fiction...
in the Netherlands; and
Robert HookeRobert Hooke, FRS was an English natural philosopher, architect and polymath who played an important role in the scientific revolution, through both experimental and theoretical work....
and
Robert BoyleRobert Boyle was a natural philosopher, chemist, physicist, inventor, and gentleman scientist, also noted for his writings in theology. He is best known for the formulation of Boyle's law...
in England.
The Cartesian philosophy of motion
{{main| René Descartes}}
The French philosopher
René DescartesRené Descartes , , also known as Renatus Cartesius , was a French philosopher, mathematician, physicist, and writer who spent most of his adult life in the Dutch Republic...
was well-connected to, and influential within, the experimental philosophy networks. Descartes had a more ambitious agenda, however, which was geared toward replacing the Scholastic philosophical tradition altogether. Questioning the reality interpreted through the senses, Descartes sought to re-establish philosophical explanatory schemes by reducing all perceived phenomena to being attributable to the motion of an invisible sea of “corpuscles”. (Notably, he reserved human thought and
GodGod is a deity in theistic and deistic religions and other belief systems, representing either the sole deity in monotheism, or a principal deity in polytheism....
from his scheme, holding these to be separate from the physical universe). In proposing this philosophical framework, Descartes supposed that different kinds of motion, such as that of planets versus that of terrestrial objects, were not fundamentally different, but were merely different manifestations of an endless chain of corpuscular motions obeying universal principles. Particularly influential were his explanation for circular astronomical motions in terms of the vortex motion of corpuscles in space (Descartes argued, in accord with the beliefs, if not the methods, of the Scholastics, that a
vacuumIn everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty...
could not exist), and his explanation of gravity in terms of corpuscles pushing objects downward.
{{see|Mechanical explanations of gravitation}}
Descartes, like Galileo, was convinced of the importance of mathematical explanation, and he and his followers were key figures in the development of mathematics and geometry in the 17th century. Cartesian mathematical descriptions of motion held that all mathematical formulations had to be justifiable in terms of direct physical action, a position held by
HuygensChristiaan Huygens, FRS was a prominent Dutch mathematician, astronomer, physicist, horologist, and writer of early science fiction...
and the German philosopher
Gottfried LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
, who, while following in the Cartesian tradition, developed his own philosophical alternative to Scholasticism, which he outlined in his 1714 work,
The Monadology.
Newtonian motion versus Cartesian motion
In the late 17th and early 18th centuries, the Cartesian mechanical tradition was challenged by another philosophical tradition established by the Cambridge University mathematician
Isaac NewtonSir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is perceived and considered by a substantial number of scholars and the general public as one of the most influential men in history...
. Where
DescartesRené Descartes , , also known as Renatus Cartesius , was a French philosopher, mathematician, physicist, and writer who spent most of his adult life in the Dutch Republic...
held that all motions should be explained with respect to the immediate force exerted by corpuscles, Newton chose to describe universal motion with reference to a set of fundamental mathematical principles: his
three laws of motionNewton's laws of motion are three physical laws that form the basis for classical mechanics. They are:# In the absence of force, a body either is at rest or moves in a straight line with constant speed....
and the
law of gravitationNewton's law of universal gravitation states that every object in this universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of distance between their centres. This is a general physical law derived...
, which he introduced in his 1687 work
Mathematical Principles of Natural Philosophy. Using these principles, Newton removed the idea that objects followed paths determined by natural shapes (such as
Kepler’sJohannes Kepler was a German mathematician, astronomer and astrologer, and key figure in the 17th century scientific revolution. He is best known for his eponymous laws of planetary motion, codified by later astronomers based on his works Astronomia nova, Harmonices Mundi, and Epitome of...
idea that planets moved naturally in
ellipseIn mathematics, an ellipse is the bounded case of a conic section, the geometric shape that results from cutting a circular conical or cylindrical surface with an oblique plane...
s), and instead demonstrated that not only regularly observed paths, but all the future motions of any body could be deduced mathematically based on knowledge of their existing motion, their
massIn physics, mass commonly refers to any of three properties of matter, which have been shown experimentally to be equivalent: inertial mass, active gravitational mass and passive gravitational mass...
, and the
forceIn physics, a force is any agent that causes a change in the motion of a free body, or that causes stress in a fixed body. It can also be described by intuitive concepts such as a push or pull that can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a...
s acting upon them. However, observed celestial motions did not precisely conform to a Newtonian treatment, and Newton, who was also deeply interested in
theologyThe term "theology" literally means the study of God, deriving from the Greek word theos, meaning 'God', and the suffix -ology from the Greek word logos meaning "discourse", "theory", or "reasoning"...
, imagined that God intervened to ensure the continued stability of the solar system.
Newton’s principles (but not his mathematical treatments) proved controversial with Continental philosophers, who found his lack of
metaphysicalMetaphysics investigates principles of reality transcending those of any particular science. Cosmology and ontology are traditional branches of metaphysics. It is concerned with explaining the fundamental nature of being and the world...
explanation for movement and gravitation philosophically unacceptable. Beginning around 1700, a bitter rift opened between the Continental and British philosophical traditions, which were stoked by heated, ongoing, and viciously personal disputes between the followers of Newton and
LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
concerning priority over the analytical techniques of
calculusCalculus is a discipline in mathematics focused on limits, functions, derivatives, integrals, and infinite series. This subject constitutes a major part of modern mathematics education. It has two major branches, differential calculus and integral calculus, which are related by the fundamental...
, which each had developed independently. Initially, the Cartesian and Leibnizian traditions prevailed on the Continent (leading to the dominance of the Leibnizian calculus notation everywhere except Britain). Newton himself remained privately disturbed at the lack of a philosophical understanding of gravitation, while insisting in his writings that none was necessary to infer its reality. As the 18th century progressed, Continental natural philosophers increasingly accepted the Newtonians’ willingness to forgo
ontologicalOntology is the philosophical study of the nature of being, existence or reality in general, as well as of the basic categories of being and their relations...
metaphysical explanations for mathematically described motions.
Rational mechanics in the 18th century
The mathematical analytical traditions established by Newton and Leibniz flourished during the 18th century as more mathematicians learned calculus and elaborated upon its initial formulation. The application of mathematical analysis to problems of motion was known as rational mechanics, or mixed mathematics (and was later termed
classical mechanicsIn the fields of physics, classical mechanics is one of the two major sub-fields of study in the science of mechanics, which is concerned with the set of physical laws governing and mathematically describing the motions of bodies and aggregates of bodies geometrically distributed within a certain...
). This work primarily revolved around
celestial mechanicsCelestial mechanics is the branch of astronomy that deals with the motions of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data. Orbital mechanics is a subfield which focuses on...
, although other applications were also developed, such as the Swiss mathematician
Daniel Bernoulli’sDaniel Bernoulli was a Dutch-Swiss mathematician and was one of the many prominent mathematicians in the Bernoulli family. He is particularly remembered for his applications of mathematics to mechanics, especially fluid mechanics, and for his pioneering work in probability and statistics...
treatment of
fluid dynamicsIn physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...
, which he introduced in his 1738 work
Hydrodynamica.
Rational mechanics dealt primarily with the development of elaborate mathematical treatments of observed motions, using Newtonian principles as a basis, and emphasized improving the tractability of complex calculations and developing of legitimate means of analytical approximation. A representative contemporary textbook was published by
Johann Baptiste HorvathJohann Baptiste Horvath was a Hungarian-born Jesuit Professor of Physics and Philosophy at the University of Trnava in modern-day Slovakia, which was then part of the Kingdom of Hungary...
. By the end of the century analytical treatments were rigorous enough to verify the stability of the
solar systemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
solely on the basis of Newton’s laws without reference to divine intervention—even as deterministic treatments of systems as simple as the
three body problemTo understand the motion of celestial bodies, the sun, planets and the visible stars has been the main motivation for the -body problem. The first complete mathematical formulation of this problem appeared in Newton's Principia...
in gravitation remained intractable.
British work, carried on by mathematicians such as
Brook TaylorBrook Taylor FRS was an English mathematician who is best known for Taylor's theorem and the Taylor series.- Life and work :...
and
Colin MaclaurinColin Maclaurin was a British mathematician. Due to changes in orthography since that time , his surname is alternatively written MacLaurin. In Gaelic the name is "Cailean MacLabhruinn", which is literally 'Colin, the son of Laurence.'-Life and work:Maclaurin was born in...
, fell behind Continental developments as the century progressed. Meanwhile, work flourished at scientific academies on the Continent, led by such mathematicians as
Daniel BernoulliDaniel Bernoulli was a Dutch-Swiss mathematician and was one of the many prominent mathematicians in the Bernoulli family. He is particularly remembered for his applications of mathematics to mechanics, especially fluid mechanics, and for his pioneering work in probability and statistics...
,
Leonhard EulerLeonhard Paul Euler was a pioneering Swiss mathematician and physicist who spent most of his life in Russia and Germany. His surname is in English ; the common English pronunciation is incorrect....
, Joseph-Louis Lagrange,
Pierre-Simon LaplacePierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...
, and
Adrien-Marie LegendreAdrien-Marie Legendre was a French mathematician. He made important contributions to statistics, number theory, abstract algebra and mathematical analysis....
. At the end of the century, the members of the
French Academy of SciencesThe French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
had attained clear dominance in the field.
Physical experimentation in the 18th and early 19th centuries
At the same time, the experimental tradition established by
GalileoGalileo Galilei was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations, and support for Copernicanism...
and his followers persisted. The
Royal SocietyThe Royal Society of London for the Improvement of Natural Knowledge, known simply as the Royal Society, or even the Royal, is a learned society for science that was founded in 1660 and is considered by most to be the oldest such society still in existence...
and the
French Academy of SciencesThe French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
were major centers for the performance and reporting of experimental work, and
NewtonSir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is perceived and considered by a substantial number of scholars and the general public as one of the most influential men in history...
was himself an influential experimenter, particularly in the field of
opticsOptics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
, where he was recognized for his
prismIn optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use...
experiments dividing white light into its constituent spectrum of colors, as published in his 1704 book
OpticksOpticks is a book written by English physicist Isaac Newton that was released to the public in 1704. It is about optics and the refraction of light, and is considered one of the great works of science in history...
(which also advocated a particulate interpretation of light). Experiments in mechanics, optics,
magnetismIn physics, the term magnetism is used to describe how materials respond on the microscopic level to an applied magnetic field; to categorize the magnetic phase of a material. For example, the most well known form of magnetism is ferromagnetism such that some ferromagnetic materials produce their...
,
static electricityStatic electricity refers to the buildup of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge...
,
chemistryBy 1000 BC, the ancient civilizations were using technologies that would form the basis of the various branches of chemistry. Extracting metal from their ores, making pottery and glazes, fermenting beer and wine, making pigments for cosmetics and painting, extracting chemicals from plants for...
, and
physiologyPhysiology is the science of the functioning of living systems. It is a subcategory of biology...
were not clearly distinguished from each other during the 18th century, but significant differences in explanatory schemes and, thus, experiment design were emerging. Chemical experimenters, for instance, defied attempts to enforce a scheme of abstract Newtonian forces onto chemical affiliations, and instead focused on the isolation and classification of chemical substances and reactions.
Nevertheless, the separate fields remained tied together, most clearly through the theories of weightless
“imponderable fluids"Imponderable fluids are features of several superseded scientific theories. The term has been used in natural philosophy and physics to explain certain mysterious phenomena as the result of fluids with properties which defy the imagination...
, such as heat (“
caloricThe caloric theory is an obsolete scientific theory that heat consists of a fluid called caloric that flows from hotter to colder bodies. Caloric was also thought of as a weightless gas that could pass in and out of pores in solids and liquids...
”),
electricityThe history of electromagnetism, that is the human understanding and recorded use of electromagnetic forces, dates back over two thousand years; see timeline of electromagnetism. The ancients would have been acquainted with the effects of atmospheric electricity, in particular lightning as...
, and
phlogistonThe phlogiston theory , first stated in 1667 by Johann Joachim Becher, is a defunct scientific theory that posited the existence of a fire-like element called "phlogiston" that was contained within combustible bodies, and released during combustion...
(which was rapidly overthrown as a concept following Lavoisier’s identification of
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
gas late in the century). Assuming that these concepts were real fluids, their flow could be traced through a mechanical apparatus or chemical reactions. This tradition of experimentation led to the development of new kinds of experimental apparatus, such as the
Leyden JarThe Leyden jar, or Leiden jar, is a device that "stores" static electricity between two electrodes on the inside and outside of a jar. It was invented independently by Ewald Georg von Kleist in 11 October 1744 and by Pieter van Musschenbroek in 1745—1746. The latter place of invention, Leiden,...
and the
Voltaic PileA voltaic pile is a set of individual Galvanic cells placed in series. The voltaic pile, invented by Alessandro Volta in 1800, was the first electric battery...
; and new kinds of measuring instruments, such as the
calorimeterA calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity. The word calorimeter is derived from the Latin word calor, meaning heat. Differential scanning calorimeters, isothermal microcalorimeters, titration...
, and improved versions of old ones, such as the
thermometerA thermometer is a device that measures temperature or temperature gradient using a variety of different principles. A thermometer has two important elements: the temperature sensor A thermometer (from the Greek θερμός (thermo) meaning "warm" and meter, "to measure") is a device that measures...
. Experiments also produced new concepts, such as the
University of GlasgowThe University of Glasgow is the fourth-oldest surviving university in the English-speaking world and one of Scotland's four ancient universities...
experimenter
Joseph Black’sJoseph Black was a Scottish physician, physicist, and chemist, known for his discoveries of latent heat, specific heat, and carbon dioxide. He was a founder of thermochemistry who developed many pre-thermodynamics concepts, such as heat capacity, and was the mentor for James Watt...
notion of
latent heatThe expression latent heat refers to the amount of energy released or absorbed by a chemical substance during a change of state that occurs without changing its temperature, meaning a phase transition such as the melting of ice or the boiling of water...
and Philadelphia intellectual
Benjamin Franklin’sBenjamin Franklin was one of the Founding Fathers of the United States of America. A noted polymath, Franklin was a leading author and printer, satirist, political theorist, politician, scientist, inventor, civic activist, statesman, soldier, and diplomat...
characterization of electrical fluid as flowing between places of excess and deficit (a concept later reinterpreted in terms of positive and negative
chargesElectric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields...
).
While it was recognized early in the 18th century that finding absolute theories of electrostatic and magnetic force akin to Newton’s principles of motion would be an important achievement, none were forthcoming. This impossibility only slowly disappeared as experimental practice became more widespread and more refined in the early years of the 19th century in places such as the newly-established
Royal InstitutionThe Royal Institution of Great Britain is an organization devoted to scientific education and research, based in London...
in London, where
John DaltonJohn Dalton FRS was an English chemist, meteorologist and physicist. He is best known for his pioneering work in the development of modern atomic theory, and his research into colour blindness .-Early life:John Dalton was born into a Quaker family at Eaglesfield, near Cockermouth in Cumberland,...
argued for an atomistic interpretation of chemistry,
Thomas YoungThomas Young may refer to:*Thomas Young , Scottish Presbyterian and author*Thomas Young , member of the Sons of Liberty*Thomas Young , British polymath, scientist and Egyptologist...
argued for the interpretation of light as a wave, and
Michael FaradayMichael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....
established the phenomenon of
electromagnetic inductionFaraday's law of induction is a basic law of electromagnetism, which is involved in the working of transformers, inductors, and many forms of electrical generators. The law states:...
. Meanwhile, the analytical methods of rational mechanics began to be applied to experimental phenomena, most influentially with the French mathematician
Joseph Fourier’sJean Baptiste Joseph Fourier was a French mathematician and physicist best known for initiating the investigation of Fourier series and their application to problems of heat transfer. The Fourier transform and Fourier's Law are also named in his honour...
analytical treatment of the flow of heat, as published in 1822.
Thermodynamics, statistical mechanics, and electromagnetic theory
The establishment of a mathematical physics of
energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
between the 1850s and the 1870s expanded substantially on the physics of prior eras and challenged traditional ideas about how the physical world worked. While
Pierre-Simon Laplace’sPierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...
work on celestial mechanics solidified a deterministically mechanistic view of objects obeying fundamental and totally reversible laws, the study of energy and particularly the flow of heat, threw this view of the universe into question. Drawing upon the engineering theory of
LazareLazare Nicolas Marguerite, Comte Carnot , the Organizer of Victory in the French Revolutionary Wars, was a French politician, engineer, and mathematician.-Education and early life:...
and
Sadi CarnotNicolas Léonard Sadi Carnot was a French physicist and military engineer who, in his 1824 Reflections on the Motive Power of Fire, gave the first successful theoretical account of heat engines, now known as the Carnot cycle, thereby laying the foundations of the second law of thermodynamics...
, and Émile Clapeyron; the experimentation of
James Prescott JouleJames Prescott Joule FRS was an English physicist and brewer, born in Salford, Lancashire. Joule studied the nature of heat, and discovered its relationship to mechanical work . This led to the theory of conservation of energy, which led to the development of the first law of thermodynamics...
on the interchangeability of mechanical, chemical, thermal, and electrical forms of work; and his own
Cambridge mathematical triposThe Mathematical Tripos is the taught mathematics course at the University of Cambridge. It is the oldest Tripos that is examined in Cambridge.-Origin of the Mathematical Tripos:...
training in mathematical analysis; the Glasgow physicist
William ThomsonWilliam Thomson, 1st Baron Kelvin , OM, GCVO, PC, PRS, FRSE, was a British mathematical physicist and engineer...
and his circle of associates established a new mathematical physics relating to the exchange of different forms of energy and energy’s overall conservation (what is still accepted as the “
first law of thermodynamicsThe first law of thermodynamics, an expression of the principle of conservation of energy, states that energy can be transformed , but cannot be created or destroyed. Alternatively:-Description:...
”). Their work was soon allied with the theories of similar but less-known work by the German physician
Julius Robert von MayerJulius Robert von Mayer was a German physician and physicist and one of the founders of thermodynamics...
and physicist and physiologist
Hermann von HelmholtzHermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...
on the conservation of forces.
Taking his mathematical cues from the heat flow work of
Joseph FourierJean Baptiste Joseph Fourier was a French mathematician and physicist best known for initiating the investigation of Fourier series and their application to problems of heat transfer. The Fourier transform and Fourier's Law are also named in his honour...
(and his own religious and
geologicalThe history of geology is concerned with the development of the natural science of geology. Geology is the scientific study of the origin, history, and structure of the Earth. Throughout the ages geology provides essential theories and data that shape how society conceptualizes the...
convictions), Thomson believed that the dissipation of energy with time (what is accepted as the “
second law of thermodynamicsThe second law of thermodynamics is an expression of the universal principle of entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium, and that the entropy change dS of a system undergoing any...
”) represented a fundamental principle of physics, which was expounded in Thomson and
Peter Guthrie Tait’sPeter Guthrie Tait was a Scottish mathematical physicist, best known for the seminal energy physics textbook Treatise on Natural Philosophy, which he co-wrote with Kelvin, and his early investigations into knot theory, which contributed to the eventual formation of topology as a mathematical...
influential work
Treatise on Natural Philosophy. However, other interpretations of what Thomson called
thermodynamicsIn physics, thermodynamics is the study of the conversion of energy into work and heat and its relation to macroscopic variables such as temperature, volume and pressure...
were established through the work of the German physicist
Rudolf ClausiusRudolf Julius Emanuel Clausius , was a German physicist and mathematician and is considered one of the central founders of the science of thermodynamics. By his restatement of Sadi Carnot's principle known as the Carnot cycle, he put the theory of heat on a truer and sounder basis...
. His
statistical mechanicsStatistical mechanics is the application of probability theory, which includes mathematical tools for dealing with large populations, to the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force...
, which was elaborated upon by
Ludwig BoltzmannLudwig Eduard Boltzmann was an Austrian physicist famous for his founding contributions in the fields of statistical mechanics and statistical thermodynamics...
and the British physicist
James Clerk MaxwellJames Clerk Maxwell was a Scottish theoretical physicist and mathematician. His most significant achievement was the development of the classical electromagnetic theory, synthesizing all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a...
, held that energy (including heat) was a measure of the speed of particles. Interrelating the statistical likelihood of certain states of organization of these particles with the energy of those states, Clausius reinterpreted the dissipation of energy to be the statistical tendency of molecular configurations to pass toward increasingly likely, increasingly disorganized states (coining the term “
entropyEntropy is a concept of information maintaining great importance in physics, chemistry, and information theory...
” to describe the disorganization of a state). The statistical versus absolute interpretations of the second law of thermodynamics set up a dispute that would last for several decades (producing arguments such as “
Maxwell's demonMaxwell's demon is a thought experiment, first formulated in 1867 by the Scottish physicist James Clerk Maxwell, intended by Maxwell primarily to "show that the 2nd Law of Thermodynamics has only a statistical certainty," and commonly used for imagining the possibility of violating it...
”), and that would not be held to be definitively resolved until the behavior of atoms was firmly established in the early 20th century.
{{see|history of thermodynamics}}
Meanwhile, the new physics of energy transformed the analysis of electromagnetic phenomena, particularly through the introduction of the concept of the
fieldIn physics, a field is a physical quantity associated to each point of spacetime. A field can be classified as a scalar field, a vector field, or a tensor field, according to whether the value of the field at each point is a scalar, a vector, or, more generally, a tensor, respectively...
and the publication of Maxwell’s 1873
Treatise on Electricity and Magnetism, which also drew upon theoretical work by German theoreticians such as
Carl Friedrich GaussJohann Carl Friedrich Gauss was a German mathematician and scientist who contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, geophysics, electrostatics, astronomy and optics...
and
Wilhelm WeberWilhelm Eduard Weber was a German physicist and, together with Carl Friedrich Gauss, inventor of the first electromagnetic telegraph.-Early years:...
. The encapsulation of heat in particulate motion, and the addition of electromagnetic forces to Newtonian dynamics established an enormously robust theoretical underpinning to physical observations. The prediction that light represented a transmission of energy in wave form through a “
luminiferous etherIn the late 19th century, "luminiferous aether" , meaning light-bearing aether, was the term used to describe a medium for the propagation of light. The word aether stems via Latin from the Greek αιθήρ, from a root meaning to kindle, burn, or shine...
”, and the seeming confirmation of that prediction with Helmholtz student Heinrich Hertz’s 1888 detection of
electromagnetic radiationElectromagnetic radiation is a ubiquitous phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It consists of electric and magnetic field components which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation...
, was a major triumph for physical theory and raised the possibility that even more fundamental theories based on the field could soon be developed. Research on the transmission of electromagnetic waves began soon after, with the experiments conducted by physicists such as
Nikola TeslaNikola Tesla was an inventor and a mechanical and electrical engineer. He is frequently cited as one of the most important contributors to the birth of commercial electricity and is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th...
, Jagadish Chandra Bose and
Guglielmo MarconiMarchese Guglielmo Marconi was an Italian inventor, best known for his development of a radiotelegraph system, which served as the foundation for the establishment of numerous affiliated companies worldwide...
during the 1890s leading to the
invention of radioWithin the history of radio, several people were involved in the invention of radio and there were many key inventions in what became the modern systems of wireless. Radio development began as "wireless telegraphy". Closely related, radio was developed along with two other key inventions, the...
.
The emergence of a new physics circa 1900
The triumph of Maxwell’s theories was undermined by inadequacies that had already begun to appear. The
Michelson-Morley experimentThe Michelson–Morley experiment was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University. It is generally considered to be the first strong evidence against the theory of a luminiferous aether...
failed to detect a shift in the
speed of lightIn physics, the speed of light is a physical constant, the speed at which electromagnetic radiation, such as light, travels in free space . Its value is 299,792,458 metres per second...
, which would have been expected as the earth moved at different angles with respect to the ether. The possibility explored by
Hendrik LorentzHendrik Antoon Lorentz was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect...
, that the ether could compress matter, thereby rendering it undetectable, presented problems of its own as a compressed
electronAn electron is a subatomic particle that carries a negative electric charge. It has no known substructure and is believed to be a point particle. An electron has a mass that is approximately 1836 times less than that of the proton. The intrinsic angular momentum of the electron is a half integer...
(detected in 1897 by British experimentalist
J. J. ThomsonSir Joseph John “J. J.” Thomson, OM, FRS was a British physicist and Nobel laureate, credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer...
) would prove unstable. Meanwhile, other experimenters began to detect unexpected forms of radiation: Wilhelm Röntgen caused a sensation with his discovery of
x-rayX-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays...
s in 1895; in 1896
Henri BecquerelAntoine Henri Becquerel was a French physicist, Nobel laureate, and the discoverer of radioactivity, for which he won the 1903 Nobel Prize in Physics .-Early life:Becquerel was born in Paris into a family which produced four generations of scientists,...
discovered that certain kinds of matter emit radiation on their own accord.
MarieMarie Skłodowska Curie was a physicist and chemist of Polish upbringing and, subsequently, French citizenship...
and
Pierre CuriePierre Curie was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity, and Nobel laureate...
coined the term “
radioactivityRadioactive decay is the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, named the daughter...
” to describe this property of matter, and isolated the radioactive elements
radiumRadium is a radioactive chemical element which has the symbol Ra and atomic number 88. Its appearance is almost pure white, but it readily oxidizes on exposure to air, turning black. Radium is an alkaline earth metal that is found in trace amounts in uranium ores. It is extremely radioactive...
and
poloniumPolonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie and Pierre Curie. A rare and highly radioactive metalloid, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Polonium has been studied for possible use in...
.
Ernest RutherfordErnest Rutherford, 1st Baron Rutherford of Nelson, OM, FRS was a New Zealand chemist and physicist who became known as the father of nuclear physics....
and
Frederick SoddyFrederick Soddy was an English radiochemist who explained, with Ernest Rutherford, that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions. He also proved the existence of isotopes of certain radioactive elements...
identified two of Becquerel’s forms of radiation with electrons and the element
heliumHelium is the chemical element with atomic number 2, and is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert monatomic gas that heads the noble gas group in the periodic table...
. In 1911 Rutherford established that the bulk of mass in atoms are concentrated in positively-charged nuclei with orbiting electrons, which was a theoretically unstable configuration. Studies of radiation and radioactive decay continued to be a preeminent focus for physical and chemical research through the 1930s, when the discovery of
nuclear fissionIn nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts, often producing free neutrons and lighter nuclei, which may eventually produce photons...
opened the way to the practical exploitation of what came to be called
“atomic” energyNuclear energy is released by the splitting or merging together of the nuclei of atom. The conversion of nuclear mass to energy is consistent with the mass-energy equivalence formula ΔE = Δm.c², in which ΔE = energy release, Δm = mass defect, and c = the speed of light in a vacuum...
.
Radical new physical theories also began to emerge in this same period. In 1905
Albert EinsteinAlbert Einstein was a theoretical physicist. His many contributions to physics include the special and general theories of relativity, the founding of relativistic cosmology, the first post-Newtonian expansion, explaining the perihelion advance of Mercury, prediction of the deflection of...
, then a Bern patent clerk, argued that the speed of light was a constant in all
inertial reference framesIn physics, an inertial frame of reference is a member of the subset of reference frames with the property that every physical law takes the same form in each such frame. In contrast, in the set of non-inertial frames the laws of physics are frame-dependent, and the usual physical forces must be...
and that electromagnetic laws should remain valid independent of reference frame—assertions which rendered the ether “superfluous” to physical theory, and that held that observations of time and length varied relative to how the observer was moving with respect to the object being measured (what came to be called the “
special theory of relativitySpecial relativity is the physical theory of measurement in inertial frames of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies"...
”). It also followed that mass and energy were interchangeable quantities according to the equation
E=mc2In physics, mass–energy equivalence is the concept that the mass of a body is a measure of its energy content. The mass of a body as measured on a scale is always equal to the total energy inside, multiplied by a constant c
2 that changes the units appropriately:where E is energy, m is...
. In another paper published the same year, Einstein asserted that electromagnetic radiation was transmitted in discrete quantities (“
quantaIn physics, a quantum is the minimum unit of any physical entity involved in an interaction. An example of an entity that is quantized is the energy transfer of elementary particles of matter and of photons and other bosons...
”), according to a constant that the theoretical physicist
Max PlanckMax Planck was a German physicist. He is considered to be the founder of the quantum theory, and thus one of the most important physicists of the twentieth century. Planck was awarded the Nobel Prize in Physics in 1918.-Biography:Planck came from a traditional, intellectual family...
had posited in 1900 to arrive at an accurate theory for the distribution of blackbody radiation—an assumption that explained the strange properties of the
photoelectric effectThe photoelectric effect is a phenomenon in which electrons are emitted from matter as a consequence of their absorption of energy from electromagnetic radiation of very short wavelength, such as visible or ultraviolet light. Electrons emitted in this manner may be referred to as "photoelectrons"...
. The Danish physicist
Niels BohrNiels Henrik David Bohr was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...
used this same constant in 1913 to explain the stability of
Rutherford’s atomThe Rutherford model or planetary model is a model of the atom devised by Ernest Rutherford. Rutherford directed the famous Geiger-Marsden experiment in 1909, which suggested to Rutherford's analysis that the Plum pudding model of J. J. Thomson of the atom was incorrect...
as well as the frequencies of light emitted by hydrogen gas.
{{see|History of special relativity }}
The radical years: general relativity and quantum mechanics
The gradual acceptance of Einstein’s theories of relativity and the quantized nature of light transmission, and of Niels Bohr’s model of the atom created as many problems as they solved, leading to a full-scale effort to reestablish physics on new fundamental principles. Expanding relativity to cases of accelerating reference frames (the “
general theory of relativityGeneral relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics. It unifies special relativity and Newton's law of universal gravitation, and describes gravity as a...
”) in the 1910s, Einstein posited an equivalence between the inertial force of acceleration and the force of gravity, leading to the conclusion that space is curved and finite in size, and the prediction of such phenomena as
gravitational lensA gravitational lens is formed when the light from a very distant, bright source is "bent" around a massive object between the source object and the observer...
ing and the distortion of time in gravitational fields.
{{see|History of general relativity}}
The quantized theory of the atom gave way to a full-scale
quantum mechanicsThe history of quantum mechanics as this interlaces with history of quantum chemistry began essentially with the 1838 discovery of cathode rays by Michael Faraday, during the 1859-1860 winter statement of the black body radiation problem by Gustav Kirchhoff, the 1877 suggestion by Ludwig Boltzmann...
in the 1920s. The quantum theory (which previously relied in the “correspondence” at large scales between the quantized world of the atom and the continuities of the “classical” world) was accepted when the Compton Effect established that light carries momentum and can scatter off particles, and when Louis de Broglie asserted that matter can be seen as behaving as a wave in much the same way as electromagnetic waves behave like particles (wave-particle duality). New principles of a “quantum” rather than a “classical” mechanics, formulated in
matrix-formMatrix mechanics is a formulation of quantum mechanics created by Werner Heisenberg, Max Born, and Pascual Jordan in 1925.Matrix mechanics was the first complete and correct definition of quantum mechanics. It extended the Bohr Model by describing how the quantum jumps occur. It did so by...
by
Werner HeisenbergWerner Heisenberg was a German theoretical physicist who made foundational contributions to quantum mechanics and is best known for asserting the uncertainty principle of quantum theory...
,
Max BornMax Born was a German born physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics and supervised the work of a number of notable physicists in the 1920s and 30s...
, and
Pascual JordanPascual Jordan was a theoretical and mathematical physicist who made significant contributions to quantum mechanics and quantum field theory. He contributed much to the mathematical form of matrix mechanics, and developed canonical anticommutation relations for fermions...
in 1925, were based on the probabilistic relationship between discrete “states” and denied the possibility of
causalityCausality is the relationship between an event and a second event , where the second event is a direct consequence of the first....
.
Erwin SchrödingerErwin Rudolf Josef Alexander Schrödinger was an Austrian theoretical physicist who achieved fame for his contributions to quantum mechanics, especially the Schrödinger equation, for which he received the Nobel Prize in 1933...
established an equivalent theory based on waves in 1926; but Heisenberg’s 1927 “
uncertainty principleIn quantum mechanics, the Heisenberg uncertainty principle states that certain pairs of physical properties, like position and momentum, cannot both be known to arbitrary precision. That is, the more precisely one property is known, the less precisely the other can be known...
” (indicating the impossibility of precisely and simultaneously measuring position and
momentumIn classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section "modern definitions of momentum" on this page...
) and the “
Copenhagen interpretationThe Copenhagen interpretation is an interpretation of quantum mechanics. A key feature of quantum mechanics is that the state of every particle is described by a wavefunction, which is a mathematical representation used to calculate the probability for it to be found in a location or a state of...
” of quantum mechanics (named after Bohr’s home city) continued to deny the possibility of fundamental causality, though opponents such as Einstein would assert that “God does not play dice with the universe”. Also in the 1920s,
Satyendra Nath BoseSatyendra Nath Bose , FRS, was an Indian physicist, specializing in mathematical physics. He is best known for his work on quantum mechanics in the early 1920s, providing the foundation for Bose-Einstein statistics and the theory of the Bose-Einstein condensate...
's work on
photonIn physics, a photon is an elementary particle, the quantum of the electromagnetic field and the basic "unit" of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s and quantum mechanics provided the foundation for Bose-Einstein statistics, the theory of the Bose-Einstein condensate, and the discovery of the
bosonIn particle physics, bosons are particles which obey Bose–Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein. In contrast to fermions, which obey Fermi-Dirac statistics, several bosons can occupy the same quantum state. Thus, bosons with the same energy can occupy the...
.
{{see|history of quantum mechanics}}
Constructing a new fundamental physics
As the philosophically inclined continued to debate the fundamental nature of the universe, quantum theories continued to be produced, beginning with
Paul Dirac’sPaul Adrien Maurice Dirac, OM, FRS was a British theoretical physicist. Dirac made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics...
formulation of a relativistic quantum theory in 1928. However, attempts to quantize electromagnetic theory entirely were stymied throughout the 1930s by theoretical formulations yielding infinite energies. This situation was not considered adequately resolved until after
World War IIWorld War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...
ended, when
Julian SchwingerJulian Seymour Schwinger was an American theoretical physicist. He is best known for his work on the theory of quantum electrodynamics, in particular for developing a relativistically invariant perturbation theory, and for renormalizing QED to one loop order.Schwinger is recognized as one of the...
,
Richard FeynmanRichard Phillips Feynman was an American physicist known for the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as work in particle physics...
, and
Sin-Itiro TomonagaSin-Itiro Tomonaga or Shin'ichirō Tomonaga was a Japanese physicist, influential in the development of quantum electrodynamics, work for which he was jointly awarded the Nobel Prize in Physics in 1965 along with Richard Feynman and Julian Schwinger.-Biography:Tomonaga was born in Tokyo in 1906...
independently posited the technique of “
renormalizationIn quantum field theory, the statistical mechanics of fields, and the theory of self-similar geometric structures, renormalization refers to a collection of techniques used to take a continuum limit....
”, which allowed for an establishment of a robust
quantum electrodynamicsQuantum electrodynamics is a relativistic quantum field theory of electrodynamics. QED was developed by a number of physicists, beginning in the late 1920s. It basically describes how light and matter interact. More specifically it deals with the interactions between electrons, positrons and photons...
(Q.E.D.).
Meanwhile, new theories of
fundamental particlesIn particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...
proliferated with the rise of the idea of the
quantization of fieldsQuantum field theory provides a theoretical framework for constructing quantum mechanical models of systems classically described by fields or of many-body systems. It is widely used in particle physics and condensed matter physics...
through “
exchange forcesIn physics, the exchange interaction is a quantum mechanical effect which increases or decreases the expectation value of the energy or distance between two or more identical particles when their wave functions overlap...
” regulated by an exchange of short-lived
“virtual” particlesIn physics, a virtual particle is a particle that exists for a limited time and space, introducing uncertainty in their energy and momentum due to the Heisenberg Uncertainty Principle...
, which were allowed to exist according to the laws governing the uncertainties inherent in the quantum world. Notably,
Hideki Yukawané , was a Japanese theoretical physicist and the first Japanese Nobel laureate.-Biography:Yukawa was born in Tokyo, Japan. In 1929, after receiving his degree from Kyoto Imperial University, he stayed on as a lecturer for four years. After graduation, he was interested in theoretical physics,...
proposed that the positive charges of the
nucleusThe nucleus is the very dense region consisting of nucleons at the center of an atom. Almost all of the mass in an atom is made up from the protons and neutrons in the nucleus, with a very small contribution from the orbiting electrons....
were kept together courtesy of a powerful but short-range force mediated by a particle intermediate in mass between the size of an
electronAn electron is a subatomic particle that carries a negative electric charge. It has no known substructure and is believed to be a point particle. An electron has a mass that is approximately 1836 times less than that of the proton. The intrinsic angular momentum of the electron is a half integer...
and a
protonThe proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom but is also stable by itself and has a second identity as the hydrogen ion, H
+...
. This particle, called the “
pionIn particle physics, a pion is any of three subatomic particles: , and . Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force.-Basic properties:...
”, was identified in 1947, but it was part of a slew of particle discoveries beginning with the
neutronThe neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutron are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a...
, the “
positronThe positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin of , and the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production...
” (a positively-charged “
antimatterIn particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles...
” version of the electron), and the “
muonThe muon is an elementary particle similar to the electron, with negative electric charge and a spin of . Together with the electron, the tauon, and the three neutrinos, it is classified as a lepton. It is the unstable subatomic particle with the second longest mean lifetime , behind the neutron...
” (a heavier relative to the electron) in the 1930s, and continuing after the war with a wide variety of other particles detected in various kinds of apparatus:
cloud chamberThe cloud chamber, also known as the Wilson chamber, is used for detecting particles of ionizing radiation. In its most basic form, a cloud chamber is a sealed environment containing a supercooled, supersaturated water or alcohol vapour. When an alpha particle or beta particle interacts with the...
s,
nuclear emulsionA nuclear emulsion plate is a photographic plate with a particularly thick emulsion layer and with a very uniform grain size. Nuclear emulsions can be used to record and investigate fast charged particles like nucleons or mesons...
s,
bubble chamberA bubble chamber is a vessel filled with a superheated transparent liquid used to detect electrically charged particles moving through it. It was invented in 1952 by Donald A. Glaser, for which he was awarded the 1960 Nobel Prize in Physics...
s, and
coincidence countersIn physics, a coincidence circuit is an electronic device with one output and two inputs. The output is activated only when signals are received at the same time at both inputs...
. At first these particles were found primarily by the
ionizedIonization is the physical process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation ....
trails left by
cosmic rayCosmic rays are energetic particles originating from outer space that impinge on Earth's atmosphere. Almost 90% of all the incoming cosmic ray particles are protons, almost 10% are helium nuclei , and slightly under 1% are heavier elements and electrons...
s, but were increasingly produced in newer and more powerful
particle acceleratorA particle accelerator is a device that uses electric fields to propel ions or charged subatomic particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator...
s.
The interaction of these particles by “
scatteringScattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of...
” and “
decayParticle decay is the spontaneous process of one elementary particle transforming into other elementary particles. During this process, an elementary particle becomes a different particle with less mass and an intermediate particle such as W boson in muon decay. The intermediate particle then...
” provided a key to new fundamental quantum theories.
Murray Gell-MannMurray Gell-Mann is an American physicist who received the 1969 Nobel Prize in physics for his work on the theory of elementary particles....
and
Yuval Ne'emanYuval Ne'eman , was an Israeli soldier, physicist and politician, serving as a Minister during the 1980s and early 1990s. He was a self-declared atheist.-Background:...
brought some order to these new particles by classifying them according to certain qualities, beginning with what Gell-Mann referred to as the “
Eightfold WayIn physics, the Eightfold Way is a term coined by American physicist Murray Gell-Mann for a theory organizing subatomic baryons and mesons into octets...
”, but proceeding into several different “octets” and “decuplets” which could predict new particles, most famously the {{SubatomicParticle|link=yes|Omega-}}, which was detected at
Brookhaven National LaboratoryBrookhaven National Laboratory , is a United States national laboratory located in Upton, New York on Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base...
in 1964, and which gave rise to the “
quarkA quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never found in...
” model of
hadronIn particle physics, a hadron is a particle made of quarks held together by the strong force . Hadrons are either mesons or baryons...
composition. While the
quark modelIn physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks which give rise to the quantum numbers of the hadrons. These quantum numbers are labels identifying the hadrons, and are of two kinds...
at first seemed inadequate to describe
strong nuclear forcesIn particle physics, the strong interaction holds quarks and gluons together to form protons, neutrons and other particles. The strong interaction is one of the four fundamental interactions, along with gravitation, the electromagnetic force and the weak interaction...
, allowing the temporary rise of competing theories such as the S-Matrix, the establishment of
quantum chromodynamicsIn theoretical physics, Quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons . It is the study of the SU Yang–Mills theory of color-charged fermions...
in the 1970s finalized a set of fundamental and exchange particles, which allowed for the establishment of a “
standard modelThe Standard Model of particle physics is a theory of three of the four known fundamental interactions and the elementary particles that take part in these interactions. These particles make up all visible matter in the universe...
” based on the mathematics of
gauge invarianceGauge invariance is the property of a field theory in which different configurations of the underlying fundamental but unobservable fields result in identical observable quantities. A theory with such a property is called a gauge theory...
, which successfully described all forces except for gravity, and which remains generally accepted within the domain to which it is designed to be applied.
The “standard model” groups the
electroweak interactionIn particle physics, the electroweak interaction is the unified description of two of the four fundamental interactions of nature: electromagnetism and the weak interaction. Although these two forces appear very different at everyday low energies, the theory models them as two different aspects of...
theory and
quantum chromodynamicsIn theoretical physics, Quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons . It is the study of the SU Yang–Mills theory of color-charged fermions...
into a structure denoted by the gauge group
SU(3)×SU(2)×U(1). The formulation of the unification of the electromagnetic and
weak interactionThe weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons...
s in the standard model is due to
Abdus SalamAbdus Salam was a Pakistani theoretical physicist, astrophysicist and Nobel laureate in Physics for his work in Electro-Weak Theory. Salam, Sheldon Glashow and Steven Weinberg shared the prize for this discovery...
,
Steven WeinbergSteven Weinberg is an American physicist and Nobel laureate in Physics for his contributions with Abdus Salam and Sheldon Glashow to the unification of the weak force and electromagnetic interaction between elementary particles.
...
and, subsequently, Sheldon Glashow. After the discovery, made at
CERNThe European Organization for Nuclear Research , known as CERN , , is the world's largest particle physics laboratory, situated in the northwest suburbs of Geneva on the Franco–Swiss border, established in 1954...
, of the existence of
neutral weak currentsWeak neutral current interactions are one of the ways in which subatomic particles can interact by means of the weak force. These interactions are mediated by the boson, and the interaction is called 'neutral' because the has no electric charge...
, mediated by the
{{histOfScience}}
As forms of scienceScience is in its broadest sense to any systematic knowledge-base or prescriptive practice that is capable of resulting in a prediction or predictable type of outcome...
historically developed out of
philosophyPhilosophy is the study of general and fundamental problems concerning matters such as existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing these questions by its critical, generally systematic approach and its reliance on reasoned...
,
physicsPhysics is a natural science; it is the study of matter and its motion through spacetime and all that derives from these, such as energy and force...
(
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
: φύσις
physisPhysis is a Greek theological, philosophical, and scientific term usually translated into English as "nature". In the Odyssey, Homer uses the word once , referring to the intrinsic way of growth of a particular species of plant...
"
natureNature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general...
") was originally referred to as
natural philosophyNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
, a term describing a field of study concerned with "the workings of nature".
Early history
{{see|History of astronomy|Aristotelian physics}}
Drawing elements from various areas of exploration including Babylonian Astronomy, early attempts at
opticsOptics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
and
mechanicsMechanics is the branch of physics concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effect of the bodies on their environment....
, and
geometryGeometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers....
, the move towards a rational understanding of nature began at least since the Archaic Period in Greece (650 BC – 480 BC) with the Presocratics. Accordingly,
LeucippusLeucippus or Leukippos was the first Greek to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms — which was elaborated in far greater detail by his pupil and successor, Democritus...
(
Greek:Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
{{Polytonic|Λεύκιππος}}, first half of 5th century BC), refusing to accept various supernatural, religious or mythological explanations for natural
phenomenaA phenomenon is any observable occurrence. In popular usage, a phenomenon often refers to an extraordinary event. In scientific usage, a phenomenon is any event that is observable, however commonplace it might be, even if it requires the use of instrumentation to observe it...
, proclaimed that every event had a natural cause. He went on to develop the theory of
atomismAtomism is a natural philosophy developed by Leucippus and his student Democritus in the fifth century BC. These atomists theorized that the natural world consists of two fundamental and opposite, indivisible bodies - atoms and void...
— the idea that everything is composed entirely of various imperishable, indivisible elements called
atomThe atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s. This was elaborated in great detail by
DemocritusDemocritus was an Ancient Greek philosopher born in Abdera in the north of Greece. He was the most prolific, and ultimately the most influential, of the pre-Socratic philosophers; his atomic theory may be regarded as the culmination of early Greek thought.His exact contributions are difficult to...
.
AristotleAristotle was a Greek philosopher, a student of Plato and teacher of Alexander the Great. He wrote on many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, politics, government, ethics, biology, and zoology.Together with Plato and Socrates , Aristotle is one of...
({{lang-el|Ἀριστοτέλης}},
Aristotélēs) (384 BC – 322 BC), a student of
PlatoPlato , was a Classical Greek philosopher, mathematician, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world...
, promoted the concept that observation of physical phenomena could ultimately lead to the discovery of the natural laws governing them. He wrote the first work which refers to that line of study as "Physics" (
Aristotle's PhysicsPhysics is an important work by Aristotle. It is a collection of treatises or lessons that deal with the most general principles of moving things, both living and non-living, rather than physical theories or investigations of the particular contents of the universe...
). During the
classical periodClassical Greece was a culture that was highly advanced and which heavily influenced the cultures of Ancient Rome and still has an enduring effect on Western Civilization. Much of modern politics, artistic thought, scientific thought, literature, and philosophy derives from this ancient society...
in Greece (6th, 5th and 4th centuries BC) and in
Hellenistic timesHellenistic civilization represents the zenith of Greek influence in the ancient world from 323 BC to about 146 BC ; note, however that Koine Greek language and Hellenistic philosophy and religion are also indisputably elements of the Roman era till Late Antiquity...
,
natural philosophyNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
slowly developed into an exciting and contentious field of study.
Early in Classical Greece, that the earth is a
sphereA sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...
("round"), was generally known by all, and around 240 BCE,
EratosthenesEratosthenes of Cyrene was a Greek mathematician, elegiac poet, athlete, geographer, and astronomer. He made several discoveries and inventions including a system of latitude and longitude...
(276 BCE - 194 BCE) accurately estimated its circumference. In contrast to Aristotle's geocentric views,
Aristarchus of SamosAristarchus was a Greek astronomer and mathematician, born on the island of Samos, in Greece. He was the first person to present an explicit argument for a heliocentric model of the solar system, placing the Sun, not the Earth, at the center of the known universe...
({{lang-el|Ἀρίσταρχος}};
310 BC-Seleucid Empire:* Antigonus orders Nicanor, one of his generals, to invade Babylonia from the east and his son Demetrius Poliorcetes to attack it from the west. Nicanor assembles a large force but it is surprised and defeated by Seleucus at the river Tigris, and his troops are either cut to pieces...
– ca.
230 BC-Anatolia:* The city of Pergamum is attacked by the Galatians because the leader of Pergamum, Attalus I Soter, has refused to pay them the customary tribute. Attalus crushes his enemy in a battle outside the walls of his city and to mark the success he takes the title of king and the name...
) presented an explicit argument for a
heliocentric modelIn astronomy, heliocentrism is the theory that the Sun is stationary and at the center of the universe. The word came from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center. Discussions on the possibility of heliocentrism date to classical...
of the
solar systemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
, placing the
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
, not the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
, at the centre.
Seleucus of SeleuciaSeleucus of Seleucia was a Hellenistic astronomer and philosopher from the Seleucia region of Mesopotamia who supported the heliocentric theory of planetary motion. Seleucus is known from the writings of Plutarch, Strabo and Aetius...
, a follower of the heliocentric theory of Aristarchus, stated that the Earth rotated around its own axis, which in turn revolved around the Sun. Though the arguments he used were lost,
PlutarchPlutarch, born Plutarchos then, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. AD 46 – 120, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...
stated that Seleucus was the first to prove the heliocentric system through reasoning.
Many contributions were made by many thinkers, including
ArchimedesArchimedes of Syracuse was a Greek mathematician, physicist, engineer, inventor, and astronomer. Although few details of his life are known, he is regarded as one of the leading scientists in classical antiquity...
({{lang-el|Ἀρχιμήδης}}) (c. 287 BC – c. 212 BC) of
"Eureka!"Eureka may refer to* Eureka , a famous exclamation attributed to Archimedes- Canada :* Eureka, Nova Scotia in Canada* Eureka, Nunavut in Canada* Eureka Sound, Nunavut, Canada...
fame, who also defined the concept of the centre of gravity and created the field of statics and
PtolemyClaudius Ptolemaeus , known in English as Ptolemy , was a Roman citizen of Greek ancestry. He was a mathematician, astronomer, geographer, astrologer and a poet of a single epigram in the Greek Anthology. He lived in Egypt under the Roman Empire, and is believed to have been born in the town of...
(Claudius Ptolemaeus (
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
: {{polytonic|Κλαύδιος Πτολεμαίος}}) who wrote scientific treatises that were later used as the basis of much later science.
Much of the accumulated knowledge of the ancient world was lost. Even of the works of the better known thinkers, few fragments survived. Although he wrote at least fourteen books, almost nothing of
HipparchusHipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...
' direct work survived. Of the 150 reputed
AristotelianAristotelianism is a tradition of philosophy that takes its defining inspiration from the work of Aristotle. Aristotelianism is understood by its proponents as critically developing Plato’s theories. Most particularly, Aristotelianism brings Plato’s ideals down to Earth as goals and goods internal...
works, only 30 exist, and some of those are "little more than lecture notes". Though reinterpreted to fit theological concerns, both
Jewish Jewish philosophy refers to the conjunction between serious study of philosophy, Jewish scholasticism and Jewish theology. In one sense, it refers to all philosophical activity carried out by Jews or in relation to the religion of Judaism...
and
IslamicIslamic philosophy is a branch of Islamic studies, and is a longstanding attempt to create harmony between philosophy and the religious teachings of Islam .-Definition:...
scholarship preserved and developed some of the ancient knowledge that would otherwise have been lost (Judeo-Islamic philosophies (800 - 1400)).
The
IslamIslam Islam Islam ( al-’islām,
[There are ten pronunciations of Islam in English, differing in whether the first or second syllable has the stress, whether the s is or , and whether the a is pronounced as in father, as in cat, or (when the stress is on the i) as in the a of sofa...]
ic
AbbasidThe Abbasid Caliphate was the third of the Islamic Caliphates of the Islamic Empire. It was ruled by the Abbasid dynasty of caliphs, who built their capital in Baghdad after overthrowing the Umayyad caliphs from all but Al Andalus....
caliphThe Caliph is the head of state in a Caliphate, and the title for the leader of the Islamic Ummah, an Islamic community ruled by the Shari'ah. It is a transliterated version of the Arabic word which means "successor" or "representative"...
s gathered many classic works of antiquity and had them translated into Arabic.
Islamic philosophersIslamic philosophy is a branch of Islamic studies, and is a longstanding attempt to create harmony between philosophy and the religious teachings of Islam .-Definition:...
such as
Al-Kindi' , also known to the West by the Latinized version of his name Alkindus, was an Arab Iraqi polymath: an Islamic philosopher, scientist, astrologer, astronomer, cosmologist, chemist, logician, mathematician, musician, physician, physicist, psychologist, and meteorologist...
(Alkindus),
Al-FarabiAbū Naṣr al-Fārābi , known in the West as Alpharabius Abū Naṣr al-Fārābi (أبو نصر محمد الفارابي - Abū Naṣr Muḥammad al-Fārābi; in some sources also mentioned as محمد بن محمد بن أوزلغ الفارابي - Muḥammad ibn Muḥammad (ibn Tarḫān) ibn Awzlaġ al-Fārābi), known in the West as...
(Alpharabius),
Avicenna, known as Abū Alī Sīnā or Ibn Sīnā , and commonly known in English by his Latinized name Avicenna , was a Persian polymath and the foremost physician and philosopher of his time...
(Ibn Sina) and
AverroesAbū 'l-Walīd Muḥammad ibn Aḥmad ibn Rushd , better known just as Ibn Rushd , and in European literature as Averroes , was an Andalusian Muslim polymath of Moroccan origins; a master of Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music...
(Ibn Rushd) reinterpreted Greek though in the context of their religion. Important contributions were made by Ibn al-Haytham and Abū Rayhān Bīrūnī before eventually passing on to
Western EuropeWestern Europe is the collection of countries in the westernmost region of Europe, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a cultural entity—the region lying west of Central Europe...
where they were studied by scholars such as
Roger BaconRoger Bacon, O.F.M. , also known as Doctor Mirabilis , was an English philosopher and Franciscan friar who placed considerable emphasis on empiricism...
and
WiteloWitelo - also known as Erazmus Ciolek Witelo, Witelon, Vitellio, Vitello, Vitello Thuringopolonis, Vitulon, Erazm Ciołek, , was a Silesian and Polish friar, theologian and scientist: physicist, natural philosopher, mathematician...
.
Awareness of ancient works re-entered the West through translations from Arabic to Latin. Their re-introduction, combined with
Judeo-IslamicThe historical interaction of Judaism and Islam started in the 7th century AD with the origin and spread of Islam in the Arabian peninsula. Because Judaism and Islam share a common origin in the Middle East through Abraham, both are considered Abrahamic religions...
theological commentaries, had a great influence on
Medieval philosophersMedieval philosophy is the philosophy of Europe and the Middle East in the era now known as medieval or the Middle Ages, the period roughly extending from the fall of the Roman Empire in the fifth century A.D. to the Renaissance in the sixteenth century...
such as
Thomas AquinasSaint Thomas Aquinas, O.P. was a priest of the Roman Catholic Church in the Dominican Order from Italy, and an immensely influential philosopher and theologian in the tradition of scholasticism, known as Doctor Angelicus and Doctor Communis...
.
Scholastic European scholarsScholasticism is derived from the Latin word scholasticus , which means "that [which] belongs to the school," and was a method of learning taught by the academics of medieval universities circa 1100–1500...
, who sought to reconcile the philosophy of the ancient classical philosophers with
Judeo-ChristianJudeo–Christian is a term used in the United States, broadly to describe a body of concepts and values thought to be held in common by Judaism and Christianity...
theology, proclaimed Aristotle the greatest thinker of the ancient world. In cases where they didn't directly contradict the Bible,
Aristotelian physicsThe Greek philosopher Aristotle developed many theories on the nature of physics. These involved what Aristotle described as the four elements...
became the foundation for the physical explanations of the European Churches.
Based on Aristotelian physics, Scholastic physics described things as moving according to their essential nature. Celestial objects were described as moving in circles, because perfect circular motion was considered an innate property of objects that existed in the uncorrupted realm of the
celestial spheresThe celestial spheres, or celestial orbs, were the fundamental celestial entities of the cosmological celestial mechanics first invented by Eudoxus, and developed by Aristotle, Ptolemy, Copernicus and others...
. The
theory of impetusThe theory of impetus was an auxiliary or secondary theory of Aristotelian dynamics, put forth initially to explain projectile motion against gravity. It was first introduced by Hipparchus in antiquity, and subsequently further developed by John Philoponus in the 6th century AD...
, the ancestor to the concepts of
inertiaInertia is the resistance of any physical object, to a change in its state of motion. It is represented numerically by an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by...
and
momentumIn classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section "modern definitions of momentum" on this page...
, was developed along similar lines by
medieval philosophersMedieval philosophy is the philosophy of Europe and the Middle East in the era now known as medieval or the Middle Ages, the period roughly extending from the fall of the Roman Empire in the fifth century A.D. to the Renaissance in the sixteenth century...
such as
John PhiloponusJohn Philoponus , also known as John the Grammarian or John of Alexandria, was a Christian and Aristotelian commentator and the author of a considerable number of philosophical treatises and theological works...
,
Avicenna, known as Abū Alī Sīnā or Ibn Sīnā , and commonly known in English by his Latinized name Avicenna , was a Persian polymath and the foremost physician and philosopher of his time...
and
Jean BuridanJean Buridan was a French priest who sowed the seeds of the Copernican revolution in Europe. Although he was one of the most famous and influential philosophers of the late Middle Ages, he is today among the least well known...
. Motions below the lunar sphere were seen as imperfect, and thus could not be expected to exhibit consistent motion. More idealized motion in the “sublunary” realm could only be achieved through artifice, and prior to the 17th century, many did not view artificial experiments as a valid means of learning about the natural world. Physical explanations in the sublunary realm revolved around tendencies. Stones contained the element earth, and earthy objects tended to move in a straight line toward the centre of the earth (and the universe in the Aristotelian geocentric view) unless otherwise prevented from doing so.
{{see|History of science and technology in China|History of Indian science and technology}}
Important physical and mathematical traditions also existed in
ancient ChineseThe history of science and technology in China is both long and rich with many contributions to science and technology. In antiquity, independently of Greek philosophers and other civilizations, ancient Chinese philosophers made significant advances in science, technology, mathematics, and...
and Indian sciences. In
Indian philosophyThe term Indian philosophy , may refer to any of several traditions of philosophical thought that originated in the Indian subcontinent, including Hindu philosophy, Buddhist philosophy, and Jain philosophy...
, Kannada of the
VaisheshikaVaisheshika, or ', is one of the six Hindu schools of philosophy of India. Historically, it has been closely associated with the Hindu school of logic, Nyaya....
school proposed the theory of atomism during the 1st millenium BC, and it was further elaborated on by the
Buddhist atomistsBuddhist atomism is a school of atomistic Buddhist philosophy that flourished on the Indian subcontinent during two major periods. During the first phase, which began to develop prior to the 4th century BCE, Buddhist atomism had a very qualitative, Aristotelian-style atomic theory. This form of...
DharmakirtiDharmakirti , was an Indian scholar and one of the Buddhist founders of Indian philosophical logic. He was one of the primary theorists of Buddhist atomism, according to which the only items considered to exist are momentary Buddhist atoms and states of consciousness.-History:Born around the turn...
and
DignāgaDignāga was an Indian scholar and one of the Buddhist founders of Indian logic....
during the 1st millenium AD. In Indian astronomy,
AryabhataAryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...
's
AryabhatiyaĀryabhatīya, an astronomical treatise, is the magnum opus and only extant work of the 5th century Indian mathematician, Aryabhata.- Structure and style:...
(499 AD) proposed the Earth's rotation, while
Nilakantha SomayajiNilakantha Somayaji , from Kerala, was a major Indian mathematician and astronomer of the Kerala school of astronomy and mathematics and was a student of Damodara. Later, he lived in Tryambakeshwar. Among his many influential books, he wrote the comprehensive astronomical treatise Tantrasamgraha...
(1444-1544) of the Kerala school of astronomy and mathematics proposed a semi-heliocentric model resembling the
Tychonic systemThe Tychonic system was a model of the solar system published by Tycho Brahe in the late 16th century which combined what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system. The model may have been inspired by Paul...
. In
Chinese philosophyChinese philosophy is philosophy written in the Chinese tradition of thought. Chinese philosophy has a history of several thousand years; its origins are often traced back to the Yi Jing , an ancient compendium of divination, which uses a system of 64 hexagrams to guide action...
,
MoziMozi , original name Mo Di , was a philosopher who lived in China during the Hundred Schools of Thought period ，born in Tengzhou, Shandong Province. He founded the school of Mohism and argued strongly against Confucianism and Daoism...
(c. 470-390 BC) proposed a concept similar to
inertiaInertia is the resistance of any physical object, to a change in its state of motion. It is represented numerically by an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by...
, while in optics,
Shen KuoShen Kuo or Shen Gua , style name Cunzhong and pseudonym Mengqi Weng , was a polymathic Chinese scientist and statesman of the Song Dynasty...
(1031–1095 AD) independently developed a
camera obscuraThe camera obscura is an optical device that projects an image of its surroundings on a screen. It is used in drawing and for entertainment, and was one of the inventions that led to photography. The device consists of a box or room with a hole in one side...
.
Emergence of experimental method and physical optics
{{see|History of optics}}
The use of
empiricalThe word empirical denotes information gained by means of observation, experience, or experiment. A central concept in science and the scientific method is that all evidence must be empirical, or empirically based, that is, dependent on evidence or consequences that are observable by the senses...
experiments in
geometrical opticsGeometrical optics, or ray optics, describes light propagation in terms of "rays". The "ray" in geometric optics is an abstraction, or "instrument", which can be used to approximately model how light will propagate. Light rays bend at the interface between two dissimilar media, and may curve in a...
dates back to second century Roman Egypt, where
PtolemyClaudius Ptolemaeus , known in English as Ptolemy , was a Roman citizen of Greek ancestry. He was a mathematician, astronomer, geographer, astrologer and a poet of a single epigram in the Greek Anthology. He lived in Egypt under the Roman Empire, and is believed to have been born in the town of...
carried out several
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
s on
reflectionIn mathematics, a reflection is a map that transforms an object into its mirror image. For example, a reflection of the small English letter p in respect to a vertical line would look like q...
,
refractionRefraction is the change in direction of a wave due to a change in its velocity. This is most commonly observed when a wave passes from one medium to another...
and
binocular visionBinocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...
. However, he either discarded or
rationalizedIn psychology and logic, rationalization is the process of constructing a logical justification for a belief, decision, action or lack thereof that was originally arrived at through a different mental process...
any empirical data that did not support his
PlatonicPlatonism is the philosophy of Plato or the name of other philosophical systems considered closely derived from it. In a narrower sense the term might indicate the doctrine of Platonic realism. The central concept of Platonism is the Theory of Forms: the transcendent, perfect archetypes, of which...
paradigm. Experiments did not hold any importance at the time, and empirical evidence was thus seen as secondary to general theory. The incorrect
emission theory of visionEmission theory or extramission theory is the proposal that visual perception is accomplished by rays of light emitted by the eyes. This theory has been replaced by intromission theory, which states that visual perception comes from something representative of the object entering the eyes...
thus continued to dominate optics through to the 10th century.
{{see|History of scientific method|Science in the Middle Ages|Physics in medieval Islam}}
The turn of the
second millenniumBeethoven|Te Kooti|- align="left"!20th Century|Nelson Mandela
Paul Rusesabagina|Martin Luther King, Jr.
Franklin D...
saw the development of an
experimental methodScientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and measurable evidence subject to specific...
emphasizing the role of
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
ation as a form of proof for scientific inquiry together with the development of
physical opticsIn physics, physical optics, or wave optics, is the branch of optics which studies interference, diffraction, polarization, and other phenomena for which the ray approximation of geometric optics is not valid...
where mathematics and geometry were combined with the philosophical field of physics. The Iraqi physicist, Ibn al-Haytham (Alhazen), is considered a central figure in this shift in physics from a philosophical activity to an experimental and mathematical one, and the shift in optics from a mathematical discipline to a physical and experimental one. Due to his
positivistPositivism is a philosophy that holds that the only authentic knowledge is that which is based on actual sense experience. Metaphysical speculation is avoided...
approach, his
Doubts Concerning Ptolemy insisted on
scientific demonstrationA scientific demonstration is a scientific experiment carried out for the purposes of demonstrating scientific principles, rather than for hypothesis testing or knowledge gathering ....
and criticized Ptolemy's
confirmation biasConfirmation bias is an irrational tendency to search for, interpret or remember information in a way that confirms preconceptions or working hypotheses. It is a type of cognitive bias and a systematic error of inductive reasoning...
and
conjecturalA conjecture is a proposition which is presumed to be real, true, or genuine, mostly based on inconclusive grounds. Karl Popper pioneered the use of the term "conjecture" in scientific philosophy. Conjecture is contrasted by hypothesis , which is a testable statement based on accepted grounds...
undemonstrated theories. His
Book of OpticsThe Book of Optics was a seven-volume treatise on optics, physics, mathematics, anatomy and psychology written by the Iraqi Muslim scientist, Ibn al-Haytham , from 1011 to 1021, when he was under house arrest in Cairo, Egypt.The book...
(1021) was the earliest successful attempt at unifying a mathematical discipline (geometrical optics) with the philosophical field of physics, to create the modern science of physical optics. An important part of this was the intromission theory of
visionVisual perception is the ability to interpret information and surroundings from visible light reaching the eye. The resulting perception is also known as eyesight, sight or vision...
, which in order to prove, he developed an experimental method to test his hypothesis. He conducted various experiments to prove his intromission theory and other hypotheses on light and vision. The
Book of Optics established experimentation as the norm of proof in optics, and gave optics a physico-mathematical conception at a much earlier date than the other mathematical disciplines. His
On the Light of the Moon also attempted to combine mathematical astronomy with physics, a field now known as
astrophysicsAstrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects such as galaxies, stars, planets, exoplanets, and the interstellar medium, as well as their...
, to formulate several astronomical hypotheses which he proved through experimentation.
Galileo Galilei and the rise of physico-mathematics
{{main|Galileo Galilei}}
In the 17th century,
natural philosophersNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
began to mount a sustained attack on the
ScholasticScholasticism is derived from the Latin word scholasticus , which means "that [which] belongs to the school," and was a method of learning taught by the academics of medieval universities circa 1100–1500...
philosophical program, and supposed that mathematical descriptive schemes adopted from such fields as mechanics and astronomy could actually yield universally valid characterizations of motion. The
TuscanThe Grand Duchy of Tuscany was a central Italian monarchy that existed, with Interruptions, from 1569 to 1859, replacing the Duchy of Florence...
mathematician
Galileo GalileiGalileo Galilei was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations, and support for Copernicanism...
was the central figure in the shift to this perspective. As a mathematician, Galileo’s role in the
universityEuropean research universities have a long history that arguably dates back to the founding of the University of Bologna in 1088, although the University of Paris and the University of Magnaura are other contenders for this position...
culture of his era was subordinated to the three major topics of study:
lawLaw is a system of rules, usually enforced through a set of institutions. It shapes politics, economics and society in numerous ways and serves as a primary social mediator of relations between people. Contract law regulates everything from buying a bus ticket to trading on derivatives markets...
,
medicineMedicine is the art and science of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, and
theologyThe term "theology" literally means the study of God, deriving from the Greek word theos, meaning 'God', and the suffix -ology from the Greek word logos meaning "discourse", "theory", or "reasoning"...
(which was closely allied to philosophy). Galileo, however, felt that the descriptive content of the technical disciplines warranted philosophical interest, particularly because mathematical analysis of astronomical observations—notably the radical analysis offered by astronomer
Nicolaus CopernicusNicolaus Copernicus was the first astronomer to formulate a comprehensive heliocentric cosmology, which displaced the Earth from the center of the universe...
concerning the relative motions of the sun, earth, moon, and planets—indicated that philosophers’ statements about the nature of the universe could be shown to be in error. Galileo also performed mechanical experiments, and insisted that motion itself—regardless of whether that motion was natural or artificial—had universally consistent characteristics that could be described mathematically.
Galileo used his 1609 telescopic discovery of the
moons of JupiterThe Galilean moons are the four moons of Jupiter discovered by Galileo Galilei on January 7, 1610. They are the largest of the many moons of Jupiter and derive their names from the lovers of Zeus: Io, Europa, Ganymede and Callisto. Ganymede, Europa and Io participate in a 1:2:4 orbital resonance...
, as published in his
Sidereus NunciusSidereus Nuncius is a short treatise published in New Latin by Galileo Galilei in March 1610. It was the first scientific treatise based on observations made through a telescope...
in 1610, to procure a position in the
MediciThe House of Medici was a political dynasty, banking family and later royal house who first began to gather prominence under Cosimo de' Medici in the Republic of Florence during the late 14th century. The family originated in the Mugello region of the Tuscan countryside, gradually rising until...
court with the dual title of mathematician and philosopher. As a court philosopher, he was expected to engage in debates with philosophers in the Aristotelian tradition, and received a large audience for his own publications, such as
The AssayerThe Assayer was a book published in Rome by Galileo Galilei in October 1623.The book was a polemic against the treatise on the comets of 1618 by Orazio Grassi, a Jesuit mathematician at the Collegio Romano. In this matter Grassi, for all his Aristotelianism, was right and Galileo was wrong...
and
Discourses and Mathematical Demonstrations Concerning Two New SciencesThe Discourses and Mathematical Demonstrations Relating to Two New Sciences was Galileo's final book and a sort of scientific testament covering much of his work in physics over the preceding thirty years.Unlike the Dialogue Concerning the Two Chief World Systems, it was not published with a license...
, which was published abroad after he was placed under house arrest for his publication of
Dialogue Concerning the Two Chief World SystemsThe Dialogue Concerning the Two Chief World Systems was a 1632 Italian language book by Galileo Galilei comparing the Copernican system with the traditional Ptolemaic system...
in 1632.
Galileo’s interest in the mechanical experimentation and mathematical description in motion established a new natural philosophical tradition focused on experimentation. This tradition, combining with the non-mathematical emphasis on the collection of "experimental histories" by philosophical reformists such as
William GilbertWilliam Gilbert, also known as Gilbard, was an English physician and natural philosopher. He was an early Copernican, and passionately rejected both the prevailing Aristotelian philosophy and the Scholastic method of university teaching...
and
Francis BaconFrancis Bacon,1st Viscount St Alban KC , son of Nicholas Bacon by his second wife Anne Bacon, was an English philosopher, statesman, scientist, lawyer, jurist, and author. He served both as Attorney General and Lord Chancellor of England...
, drew a significant following in the years leading up to and following Galileo’s death, including
Evangelista TorricelliEvangelista Torricelli was an Italian physicist and mathematician, best known for his invention of the barometer.-Biography:Torricelli was born in Faenza, then part of the Papal States...
and the participants in the
Accademia del CimentoThe Accademia del Cimento , an early scientific society, was founded in Florence 1657 by students of Galileo, Evangelista Torricelli and Vincenzo Viviani. The foundation of Academy was funded by Prince Leopoldo and Grand Duke Ferdinando II de' Medici. Giovanni Borelli and Nicolaus Steno were also...
in Italy;
Marin MersenneMarin Mersenne, Marin Mersennus or le Père Mersenne was a French theologian, philosopher, mathematician and music theorist, often referred to as the "father of acoustics" .-Life:...
and
Blaise Pascal Blaise Pascal , was a French mathematician, physicist, and religious philosopher. He was a child prodigy who was educated by his father, a civil servant...
in France;
Christiaan HuygensChristiaan Huygens, FRS was a prominent Dutch mathematician, astronomer, physicist, horologist, and writer of early science fiction...
in the Netherlands; and
Robert HookeRobert Hooke, FRS was an English natural philosopher, architect and polymath who played an important role in the scientific revolution, through both experimental and theoretical work....
and
Robert BoyleRobert Boyle was a natural philosopher, chemist, physicist, inventor, and gentleman scientist, also noted for his writings in theology. He is best known for the formulation of Boyle's law...
in England.
The Cartesian philosophy of motion
{{main| René Descartes}}
The French philosopher
René DescartesRené Descartes , , also known as Renatus Cartesius , was a French philosopher, mathematician, physicist, and writer who spent most of his adult life in the Dutch Republic...
was well-connected to, and influential within, the experimental philosophy networks. Descartes had a more ambitious agenda, however, which was geared toward replacing the Scholastic philosophical tradition altogether. Questioning the reality interpreted through the senses, Descartes sought to re-establish philosophical explanatory schemes by reducing all perceived phenomena to being attributable to the motion of an invisible sea of “corpuscles”. (Notably, he reserved human thought and
GodGod is a deity in theistic and deistic religions and other belief systems, representing either the sole deity in monotheism, or a principal deity in polytheism....
from his scheme, holding these to be separate from the physical universe). In proposing this philosophical framework, Descartes supposed that different kinds of motion, such as that of planets versus that of terrestrial objects, were not fundamentally different, but were merely different manifestations of an endless chain of corpuscular motions obeying universal principles. Particularly influential were his explanation for circular astronomical motions in terms of the vortex motion of corpuscles in space (Descartes argued, in accord with the beliefs, if not the methods, of the Scholastics, that a
vacuumIn everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty...
could not exist), and his explanation of gravity in terms of corpuscles pushing objects downward.
{{see|Mechanical explanations of gravitation}}
Descartes, like Galileo, was convinced of the importance of mathematical explanation, and he and his followers were key figures in the development of mathematics and geometry in the 17th century. Cartesian mathematical descriptions of motion held that all mathematical formulations had to be justifiable in terms of direct physical action, a position held by
HuygensChristiaan Huygens, FRS was a prominent Dutch mathematician, astronomer, physicist, horologist, and writer of early science fiction...
and the German philosopher
Gottfried LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
, who, while following in the Cartesian tradition, developed his own philosophical alternative to Scholasticism, which he outlined in his 1714 work,
The Monadology.
Newtonian motion versus Cartesian motion
In the late 17th and early 18th centuries, the Cartesian mechanical tradition was challenged by another philosophical tradition established by the Cambridge University mathematician
Isaac NewtonSir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is perceived and considered by a substantial number of scholars and the general public as one of the most influential men in history...
. Where
DescartesRené Descartes , , also known as Renatus Cartesius , was a French philosopher, mathematician, physicist, and writer who spent most of his adult life in the Dutch Republic...
held that all motions should be explained with respect to the immediate force exerted by corpuscles, Newton chose to describe universal motion with reference to a set of fundamental mathematical principles: his
three laws of motionNewton's laws of motion are three physical laws that form the basis for classical mechanics. They are:# In the absence of force, a body either is at rest or moves in a straight line with constant speed....
and the
law of gravitationNewton's law of universal gravitation states that every object in this universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of distance between their centres. This is a general physical law derived...
, which he introduced in his 1687 work
Mathematical Principles of Natural Philosophy. Using these principles, Newton removed the idea that objects followed paths determined by natural shapes (such as
Kepler’sJohannes Kepler was a German mathematician, astronomer and astrologer, and key figure in the 17th century scientific revolution. He is best known for his eponymous laws of planetary motion, codified by later astronomers based on his works Astronomia nova, Harmonices Mundi, and Epitome of...
idea that planets moved naturally in
ellipseIn mathematics, an ellipse is the bounded case of a conic section, the geometric shape that results from cutting a circular conical or cylindrical surface with an oblique plane...
s), and instead demonstrated that not only regularly observed paths, but all the future motions of any body could be deduced mathematically based on knowledge of their existing motion, their
massIn physics, mass commonly refers to any of three properties of matter, which have been shown experimentally to be equivalent: inertial mass, active gravitational mass and passive gravitational mass...
, and the
forceIn physics, a force is any agent that causes a change in the motion of a free body, or that causes stress in a fixed body. It can also be described by intuitive concepts such as a push or pull that can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a...
s acting upon them. However, observed celestial motions did not precisely conform to a Newtonian treatment, and Newton, who was also deeply interested in
theologyThe term "theology" literally means the study of God, deriving from the Greek word theos, meaning 'God', and the suffix -ology from the Greek word logos meaning "discourse", "theory", or "reasoning"...
, imagined that God intervened to ensure the continued stability of the solar system.
Newton’s principles (but not his mathematical treatments) proved controversial with Continental philosophers, who found his lack of
metaphysicalMetaphysics investigates principles of reality transcending those of any particular science. Cosmology and ontology are traditional branches of metaphysics. It is concerned with explaining the fundamental nature of being and the world...
explanation for movement and gravitation philosophically unacceptable. Beginning around 1700, a bitter rift opened between the Continental and British philosophical traditions, which were stoked by heated, ongoing, and viciously personal disputes between the followers of Newton and
LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
concerning priority over the analytical techniques of
calculusCalculus is a discipline in mathematics focused on limits, functions, derivatives, integrals, and infinite series. This subject constitutes a major part of modern mathematics education. It has two major branches, differential calculus and integral calculus, which are related by the fundamental...
, which each had developed independently. Initially, the Cartesian and Leibnizian traditions prevailed on the Continent (leading to the dominance of the Leibnizian calculus notation everywhere except Britain). Newton himself remained privately disturbed at the lack of a philosophical understanding of gravitation, while insisting in his writings that none was necessary to infer its reality. As the 18th century progressed, Continental natural philosophers increasingly accepted the Newtonians’ willingness to forgo
ontologicalOntology is the philosophical study of the nature of being, existence or reality in general, as well as of the basic categories of being and their relations...
metaphysical explanations for mathematically described motions.
Rational mechanics in the 18th century
The mathematical analytical traditions established by Newton and Leibniz flourished during the 18th century as more mathematicians learned calculus and elaborated upon its initial formulation. The application of mathematical analysis to problems of motion was known as rational mechanics, or mixed mathematics (and was later termed
classical mechanicsIn the fields of physics, classical mechanics is one of the two major sub-fields of study in the science of mechanics, which is concerned with the set of physical laws governing and mathematically describing the motions of bodies and aggregates of bodies geometrically distributed within a certain...
). This work primarily revolved around
celestial mechanicsCelestial mechanics is the branch of astronomy that deals with the motions of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data. Orbital mechanics is a subfield which focuses on...
, although other applications were also developed, such as the Swiss mathematician
Daniel Bernoulli’sDaniel Bernoulli was a Dutch-Swiss mathematician and was one of the many prominent mathematicians in the Bernoulli family. He is particularly remembered for his applications of mathematics to mechanics, especially fluid mechanics, and for his pioneering work in probability and statistics...
treatment of
fluid dynamicsIn physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...
, which he introduced in his 1738 work
Hydrodynamica.
Rational mechanics dealt primarily with the development of elaborate mathematical treatments of observed motions, using Newtonian principles as a basis, and emphasized improving the tractability of complex calculations and developing of legitimate means of analytical approximation. A representative contemporary textbook was published by
Johann Baptiste HorvathJohann Baptiste Horvath was a Hungarian-born Jesuit Professor of Physics and Philosophy at the University of Trnava in modern-day Slovakia, which was then part of the Kingdom of Hungary...
. By the end of the century analytical treatments were rigorous enough to verify the stability of the
solar systemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
solely on the basis of Newton’s laws without reference to divine intervention—even as deterministic treatments of systems as simple as the
three body problemTo understand the motion of celestial bodies, the sun, planets and the visible stars has been the main motivation for the -body problem. The first complete mathematical formulation of this problem appeared in Newton's Principia...
in gravitation remained intractable.
British work, carried on by mathematicians such as
Brook TaylorBrook Taylor FRS was an English mathematician who is best known for Taylor's theorem and the Taylor series.- Life and work :...
and
Colin MaclaurinColin Maclaurin was a British mathematician. Due to changes in orthography since that time , his surname is alternatively written MacLaurin. In Gaelic the name is "Cailean MacLabhruinn", which is literally 'Colin, the son of Laurence.'-Life and work:Maclaurin was born in...
, fell behind Continental developments as the century progressed. Meanwhile, work flourished at scientific academies on the Continent, led by such mathematicians as
Daniel BernoulliDaniel Bernoulli was a Dutch-Swiss mathematician and was one of the many prominent mathematicians in the Bernoulli family. He is particularly remembered for his applications of mathematics to mechanics, especially fluid mechanics, and for his pioneering work in probability and statistics...
,
Leonhard EulerLeonhard Paul Euler was a pioneering Swiss mathematician and physicist who spent most of his life in Russia and Germany. His surname is in English ; the common English pronunciation is incorrect....
, Joseph-Louis Lagrange,
Pierre-Simon LaplacePierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...
, and
Adrien-Marie LegendreAdrien-Marie Legendre was a French mathematician. He made important contributions to statistics, number theory, abstract algebra and mathematical analysis....
. At the end of the century, the members of the
French Academy of SciencesThe French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
had attained clear dominance in the field.
Physical experimentation in the 18th and early 19th centuries
At the same time, the experimental tradition established by
GalileoGalileo Galilei was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations, and support for Copernicanism...
and his followers persisted. The
Royal SocietyThe Royal Society of London for the Improvement of Natural Knowledge, known simply as the Royal Society, or even the Royal, is a learned society for science that was founded in 1660 and is considered by most to be the oldest such society still in existence...
and the
French Academy of SciencesThe French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
were major centers for the performance and reporting of experimental work, and
NewtonSir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is perceived and considered by a substantial number of scholars and the general public as one of the most influential men in history...
was himself an influential experimenter, particularly in the field of
opticsOptics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
, where he was recognized for his
prismIn optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use...
experiments dividing white light into its constituent spectrum of colors, as published in his 1704 book
OpticksOpticks is a book written by English physicist Isaac Newton that was released to the public in 1704. It is about optics and the refraction of light, and is considered one of the great works of science in history...
(which also advocated a particulate interpretation of light). Experiments in mechanics, optics,
magnetismIn physics, the term magnetism is used to describe how materials respond on the microscopic level to an applied magnetic field; to categorize the magnetic phase of a material. For example, the most well known form of magnetism is ferromagnetism such that some ferromagnetic materials produce their...
,
static electricityStatic electricity refers to the buildup of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge...
,