Timeline of cosmology

Timeline of cosmology

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This timeline of cosmological theories and discoveries is a chronological
Chronology
Chronology is the science of arranging events in their order of occurrence in time, such as the use of a timeline or sequence of events. It is also "the determination of the actual temporal sequence of past events".Chronology is part of periodization...

 record of the development of humanity's understanding of the cosmos
Cosmos
In the general sense, a cosmos is an orderly or harmonious system. It originates from the Greek term κόσμος , meaning "order" or "ornament" and is antithetical to the concept of chaos. Today, the word is generally used as a synonym of the word Universe . The word cosmos originates from the same root...

 over the last two-plus millennia. Modern cosmological
Cosmology
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

 ideas follow the development of the scientific discipline
Science
Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...

 of physical cosmology
Physical cosmology
Physical cosmology, as a branch of astronomy, is the study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution. For most of human history, it was a branch of metaphysics and religion...

.

Pre-1900

  • ca. 16th century BC — In Babylonian cosmology, particularly that depicted in the Enûma Eliš, the Earth
    Earth
    Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

     and heavens were seen as a "spatial whole, even one of round shape
    Spherical Earth
    The concept of a spherical Earth dates back to ancient Greek philosophy from around the 6th century BC, but remained a matter of philosophical speculation until the 3rd century BC when Hellenistic astronomy established the spherical shape of the earth as a physical given...

    ," revolving around the "cult-place of the deity
    Deity
    A deity is a recognized preternatural or supernatural immortal being, who may be thought of as holy, divine, or sacred, held in high regard, and respected by believers....

    " rather than the Earth, and it was believed that there is a plurality of heavens and earths
    Cosmic pluralism
    Cosmic pluralism, the plurality of worlds, or simply pluralism, describes the belief in numerous other worlds which harbour extraterrestrial life. The debate over pluralism began as early as the time of Thales Cosmic pluralism, the plurality of worlds, or simply pluralism, describes the belief in...

    .
  • ca. 12th century BC — The Rigveda
    Rigveda
    The Rigveda is an ancient Indian sacred collection of Vedic Sanskrit hymns...

    has some cosmological hymns, particularly in the late book 10, notably the Nasadiya Sukta
    Nasadiya Sukta
    The Nasadiya Sukta is the 129th hymn of the 10th Mandala of the Rigveda. It is concerned with cosmology and the origin of the universe. It is known for its skepticism...

     which describes the origin of the universe
    Universe
    The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

    , originating from the monistic Hiranyagarbha
    Hiranyagarbha
    Image:Hinducosm Map1.svg|thumb|Click an area to go there. This is one of many material universes, Brahmāṇḍa, which expand from Mahā Viṣṇu when He breathes.|400px|alt=One Brahmāṇḍa, with Garbhodakaśāyī-Viṣṇurect 216 61 277 80 Brahma...

    or "Golden Egg".
  • 6th century BC — The Babylonian world map shows Babylon on the Euphrates, surrounded by a circular landmass showing Assyria, Armenia and several cities, in turn surrounded by a "bitter river" (Oceanus
    Oceanus
    Oceanus ; , Ōkeanós) was a pseudo-geographical feature in classical antiquity, believed by the ancient Greeks and Romans to be the world-ocean, an enormous river encircling the world....

    ), with seven islands arranged around it so as to form a seven-pointed star. Contemporary Biblical cosmology
    Biblical cosmology
    The various authors of the Hebrew Bible and New Testament provide glimpses of their views regarding cosmology.According to the Genesis creation narrative, the cosmos created by Elohim has three levels, with the habitable world in the centre, an underworld below and the heavens above...

     of the Tanakh
    Tanakh
    The Tanakh is a name used in Judaism for the canon of the Hebrew Bible. The Tanakh is also known as the Masoretic Text or the Miqra. The name is an acronym formed from the initial Hebrew letters of the Masoretic Text's three traditional subdivisions: The Torah , Nevi'im and Ketuvim —hence...

     reflects the same view of the Earth as a plain or a hill figured like a hemisphere, swimming on water and overarched by the solid vault of the firmament
    Firmament
    The firmament is the vault or expanse of the sky. According to Genesis, God created the firmament to separate the oceans from other waters above.-Etymology:...

    . To this vault are fastened the stars.
  • 4th century BC — Aristotle
    Aristotle
    Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

     proposes an Earth-centered universe
    Geocentric model
    In astronomy, the geocentric model , is the superseded theory that the Earth is the center of the universe, and that all other objects orbit around it. This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece...

     in which the Earth is stationary and the universe is finite in extent but infinite in time
  • 3rd century BC — Aristarchus of Samos
    Aristarchus of Samos
    Aristarchus, or more correctly Aristarchos , was a Greek astronomer and mathematician, born on the island of Samos, in Greece. He presented the first known heliocentric model of the solar system, placing the Sun, not the Earth, at the center of the known universe...

     proposes a Sun
    Sun
    The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

    -centered universe
  • 2nd century BC — Seleucus of Seleucia
    Seleucus of Seleucia
    Seleucus of Seleucia was a Hellenistic astronomer and philosopher. Coming from Seleucia on the Tigris, the capital of the Seleucid empire, or, alternatively, Seleukia on the Red Sea, he is best known as a proponent of heliocentrism and for his theory of the origin of tides.- Heliocentric theory...

     elaborates on Aristarchus' heliocentric
    Heliocentrism
    Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around a stationary Sun at the center of the universe. The word comes from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center...

     universe, using the phenomenon of tide
    Tide
    Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

    s to explain heliocentrism
  • 2nd century AD — Ptolemy
    Ptolemy
    Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

     proposes an Earth-centered universe, with the Sun and planets revolving around the Earth
  • 5th-11th centuries — Several astronomers propose a Sun-centered universe, including Aryabhata
    Aryabhata
    Aryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...

    , Albumasar
    Ja'far ibn Muhammad Abu Ma'shar al-Balkhi
    Abū Maʿshar, Jaʿfar ibn Muḥammad al-Balkhī , was a Persian astrologer, astronomer, and Islamic philosopher, thought to be the greatest astrologer of the Abbasid court in Baghdad...

     and Al-Sijzi
    Al-Sijzi
    Abu Sa'id Ahmed ibn Mohammed ibn Abd Jalil Sijzi was a Persian astronomer and mathematician from Sistan, a region lying in the south-west of Afghanistan and south-east of Iran....

  • 6th century — John Philoponus
    John Philoponus
    John 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...

     proposes a universe that is finite in time
    Time
    Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

     and argues against the ancient Greek notion of an infinite universe
  • ca. 8th century — Puranic Hindu cosmology
    Hindu cosmology
    In Hindu cosmology the universe is, according to Hindu mythology and Vedic cosmology, cyclically created and destroyed.-Description:The Hindu cosmology and timeline is the closest to modern scientific timelines and even more which might indicate that the Big Bang is not the beginning of everything...

    , in which the Universe
    Universe
    The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

     goes through repeated cycles of creation, destruction and rebirth, with each cycle lasting 4.32 billion years.
  • 9th-12th centuries — Al-Kindi
    Al-Kindi
    ' , known as "the Philosopher of the Arabs", was a Muslim Arab philosopher, mathematician, physician, and musician. Al-Kindi was the first of the Muslim peripatetic philosophers, and is unanimously hailed as the "father of Islamic or Arabic philosophy" for his synthesis, adaptation and promotion...

     (Alkindus), Saadia Gaon
    Saadia Gaon
    Saʻadiah ben Yosef Gaon was a prominent rabbi, Jewish philosopher, and exegete of the Geonic period.The first important rabbinic figure to write extensively in Arabic, he is considered the founder of Judeo-Arabic literature...

     (Saadia ben Joseph) and the Al-Ghazali
    Al-Ghazali
    Abu Hāmed Mohammad ibn Mohammad al-Ghazzālī , known as Algazel to the western medieval world, born and died in Tus, in the Khorasan province of Persia was a Persian Muslim theologian, jurist, philosopher, and mystic....

     (Algazel) support a universe that has a finite past and develop two logical arguments against the notion of an infinite past, one of which is later adopted by Immanuel Kant
    Immanuel Kant
    Immanuel Kant was a German philosopher from Königsberg , researching, lecturing and writing on philosophy and anthropology at the end of the 18th Century Enlightenment....

  • 964 — Abd al-Rahman al-Sufi (Azophi), a Persian astronomer
    Islamic astronomy
    Islamic astronomy or Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and...

    , makes the first recorded observations of the Andromeda Galaxy
    Andromeda Galaxy
    The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...

     and the Large Magellanic Cloud
    Large Magellanic Cloud
    The Large Magellanic Cloud is a nearby irregular galaxy, and is a satellite of the Milky Way. At a distance of slightly less than 50 kiloparsecs , the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and Canis Major Dwarf Galaxy lying closer to the center...

    , the first galaxies other than the Milky Way to be observed from Earth, in his Book of Fixed Stars
    Book of Fixed Stars
    The Book of Fixed Stars is an astronomical text written by Abd al-Rahman al-Sufi around 964. The book was written in Arabic, although the author himself was Persian...

  • 12th century — Fakhr al-Din al-Razi
    Fakhr al-Din al-Razi
    Abu Abdullah Muhammad ibn Umar ibn al-Husayn al-Taymi al-Bakri al-Tabaristani Fakhr al-Din al-Razi , most commonly known as Fakhruddin Razi was a well-known Persian Sunni Muslim theologian and philosopher....

     discusses Islamic cosmology
    Islamic cosmology
    Islamic cosmology refers to cosmology in Islamic societies. It is mainly derived from the Qur'an, Hadith, Sunnah, and current Islamic as well as other pre-Islamic sources...

    , rejects Aristotle's idea of an Earth-centered universe, and, in the context of his commentary on the Qur'an
    Qur'an
    The Quran , also transliterated Qur'an, Koran, Alcoran, Qur’ān, Coran, Kuran, and al-Qur’ān, is the central religious text of Islam, which Muslims consider the verbatim word of God . It is regarded widely as the finest piece of literature in the Arabic language...

    ic verse, "All praise belongs to God, Lord of the Worlds," proposes that the universe has more than "a thousand thousand worlds beyond this world such that each one of those worlds be bigger and more massive than this world as well as having the like of what this world has." He argued that there exists an infinite outer space
    Outer space
    Outer space is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, and neutrinos....

     beyond the known world, and that there could be an infinite number of universes.
  • 13th century — Nasīr al-Dīn al-Tūsī
    Nasir al-Din al-Tusi
    Khawaja Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī , better known as Naṣīr al-Dīn al-Ṭūsī , was a Persian polymath and prolific writer: an astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed...

     provides the first empirical evidence
    Empirical research
    Empirical research is a way of gaining knowledge by means of direct and indirect observation or experience. Empirical evidence can be analyzed quantitatively or qualitatively...

     for the Earth's rotation on its axis
  • 15th century — Ali Qushji provides empirical evidence for the Earth's rotation on its axis and rejects the stationary Earth theories of Aristotle and Ptolemy
  • 15th-16th centuries — Nilakantha Somayaji
    Nilakantha Somayaji
    Kelallur Nilakantha Somayaji was a major mathematician and astronomer of the Kerala school of astronomy and mathematics. One of his most influential works was the comprehensive astronomical treatise Tantrasamgraha completed in 1501...

     and Tycho Brahe
    Tycho Brahe
    Tycho Brahe , born Tyge Ottesen Brahe, was a Danish nobleman known for his accurate and comprehensive astronomical and planetary observations...

     propose a universe in which the planets orbit the Sun and the Sun orbits the Earth, known as the Tychonic system
    Tychonic system
    The 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...

  • 1543 — Nicolaus Copernicus
    Nicolaus Copernicus
    Nicolaus Copernicus was a Renaissance astronomer and the first person to formulate a comprehensive heliocentric cosmology which displaced the Earth from the center of the universe....

     publishes his heliocentric universe
    Copernican heliocentrism
    Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets rotating around it in circular paths modified by epicycles and at uniform...

     in his De revolutionibus orbium coelestium
    De revolutionibus orbium coelestium
    De revolutionibus orbium coelestium is the seminal work on the heliocentric theory of the Renaissance astronomer Nicolaus Copernicus...

  • 1576 — Thomas Digges
    Thomas Digges
    Sir Thomas Digges was an English mathematician and astronomer. He was the first to expound the Copernican system in English but discarded the notion of a fixed shell of immoveable stars to postulate infinitely many stars at varying distances; he was also first to postulate the "dark night sky...

     modifies the Copernican system
    Copernican heliocentrism
    Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets rotating around it in circular paths modified by epicycles and at uniform...

     by removing its outer edge and replacing the edge with a star
    Star
    A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

    -filled unbounded space
  • 1584 — Giordano Bruno
    Giordano Bruno
    Giordano Bruno , born Filippo Bruno, was an Italian Dominican friar, philosopher, mathematician and astronomer. His cosmological theories went beyond the Copernican model in proposing that the Sun was essentially a star, and moreover, that the universe contained an infinite number of inhabited...

     proposes a non-hierarchical cosmology, wherein the Copernican solar system
    Solar System
    The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

     is not the center of the universe, but rather, a relatively insignificant star system
    Star system
    A star system or stellar system is a small number of stars which orbit each other, bound by gravitational attraction. A large number of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems.-Binary star systems:A stellar...

    , amongst an infinite multitude of others
  • 1610 — Johannes Kepler
    Johannes Kepler
    Johannes Kepler was a German mathematician, astronomer and astrologer. A 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 Copernican...

     uses the dark night sky to argue for a finite universe
  • 1687 — Sir Isaac Newton's laws
    Physical law
    A physical law or scientific law is "a theoretical principle deduced from particular facts, applicable to a defined group or class of phenomena, and expressible by the statement that a particular phenomenon always occurs if certain conditions be present." Physical laws are typically conclusions...

     describe large-scale motion throughout the universe
  • 1720 — Edmund Halley puts forth an early form of Olbers' paradox
    Olbers' paradox
    In astrophysics and physical cosmology, Olbers' paradox is the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. It is one of the pieces of evidence for a non-static universe such as the current Big Bang model. The argument is also...

  • 1744 — Jean-Philippe de Cheseaux
    Jean-Philippe de Cheseaux
    Jean-Philippe Loys de Chéseaux was an astronomer from Lausanne in Switzerland. In 1746 he presented a list of nebulae, eight of which were his own new discoveries, to the Académie Française des Sciences. The list was noted privately by Le Gentil in 1759, but only made public in 1892 by Guillaume...

     puts forth an early form of Olbers' paradox
  • 1791 — Erasmus Darwin
    Erasmus Darwin
    Erasmus Darwin was an English physician who turned down George III's invitation to be a physician to the King. One of the key thinkers of the Midlands Enlightenment, he was also a natural philosopher, physiologist, slave trade abolitionist,inventor and poet...

     pens the first description of a cyclical expanding and contracting universe in his poem The Economy of Vegetation
    The Botanic Garden
    The Botanic Garden is a set of two poems, The Economy of Vegetation and The Loves of the Plants, by the British poet and naturalist Erasmus Darwin. The Economy of Vegetation celebrates technological innovation, scientific discovery and offers theories concerning contemporary scientific questions,...

  • 1826 — Heinrich Wilhelm Olbers puts forth Olbers' paradox
    Olbers' paradox
    In astrophysics and physical cosmology, Olbers' paradox is the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. It is one of the pieces of evidence for a non-static universe such as the current Big Bang model. The argument is also...

  • 1848 — Edgar Allan Poe
    Edgar Allan Poe
    Edgar Allan Poe was an American author, poet, editor and literary critic, considered part of the American Romantic Movement. Best known for his tales of mystery and the macabre, Poe was one of the earliest American practitioners of the short story and is considered the inventor of the detective...

     offers first correct solution to Olbers' paradox in Eureka: A Prose Poem, an essay that also suggests the expansion and collapse of the universe

1900–1949

  • 1905 — Albert Einstein
    Albert Einstein
    Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...

     publishes the Special Theory of Relativity
    Special relativity
    Special relativity is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies".It generalizes Galileo's...

    , positing that space and time are not separate continua
  • 1915 — Albert Einstein publishes the General Theory of Relativity, showing that an energy density warps spacetime
    Spacetime
    In physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions...

  • 1917 — Willem de Sitter
    Willem de Sitter
    Willem de Sitter was a Dutch mathematician, physicist and astronomer.-Life and work:Born in Sneek, De Sitter studied mathematics at the University of Groningen and then joined the Groningen astronomical laboratory. He worked at the Cape Observatory in South Africa...

     derives an isotropic static cosmology with a cosmological constant
    Cosmological constant
    In physical cosmology, the cosmological constant was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe...

    , as well as an empty expanding cosmology
    Metric expansion of space
    The metric expansion of space is the increase of distance between distant parts of the universe with time. It is an intrinsic expansion—that is, it is defined by the relative separation of parts of the universe and not by motion "outward" into preexisting space...

     with a cosmological constant, termed a de Sitter universe
    De Sitter universe
    A de Sitter universe is a cosmological solution to Einstein's field equations of General Relativity which is named after Willem de Sitter. It models the universe as spatially flat and neglects ordinary matter, so the dynamics of the universe are dominated by the cosmological constant, thought to...

  • 1920 — The Shapley-Curtis Debate takes place at the Smithsonian
  • 1921 — The National Research Council
    National Research Council
    National Research Council may refer to:* National Research Council , Canada's leading organization for scientific research and development...

     (NRC) published the official transcript of the Shapley-Curtis Debate
  • 1922 — Vesto Slipher
    Vesto Slipher
    Vesto Melvin Slipher was an American astronomer. His brother Earl C. Slipher was also an astronomer and a director at the Lowell Observatory....

     summarizes his findings on the spiral nebulae
    Galaxy
    A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...

    's systematic redshift
    Redshift
    In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...

    s
  • 1922 — Alexander Friedmann finds a solution to the Einstein field equations which suggests a general expansion of space
  • 1924 — Edwin Hubble
    Edwin Hubble
    Edwin Powell Hubble was an American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way - our own galaxy...

     discovers that the universe is composed of thousands of galaxies.
  • 1927 — Georges Lemaître
    Georges Lemaître
    Monsignor Georges Henri Joseph Édouard Lemaître was a Belgian priest, astronomer and professor of physics at the Catholic University of Louvain. He was the first person to propose the theory of the expansion of the Universe, widely misattributed to Edwin Hubble...

     discusses the creation event of an expanding universe governed by the Einstein field equations. From its solutions to the Einstein equations, he predicts the distance-redshift relation.
  • 1928 — Howard Percy Robertson
    Howard Percy Robertson
    Howard Percy Robertson was an American mathematician and physicist known for contributions related to physical cosmology and the uncertainty principle...

     briefly mentions that Vesto Slipher's redshift measurements combined with brightness measurements of the same galaxies indicate a redshift-distance relation
  • 1929 — Edwin Hubble
    Edwin Hubble
    Edwin Powell Hubble was an American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way - our own galaxy...

     demonstrates the linear redshift-distance relation and thus shows the expansion of the universe
  • 1933 — Edward Milne names and formalizes the cosmological principle
    Cosmological Principle
    In modern physical cosmology, the cosmological principle is the working assumption that observers on Earth do not occupy an unusual or privileged location within the universe as a whole, judged as observers of the physical phenomena produced by uniform and universal laws of physics...

  • 1934 — Georges Lemaître
    Georges Lemaître
    Monsignor Georges Henri Joseph Édouard Lemaître was a Belgian priest, astronomer and professor of physics at the Catholic University of Louvain. He was the first person to propose the theory of the expansion of the Universe, widely misattributed to Edwin Hubble...

     interprets the cosmological constant as due to a vacuum energy
    Vacuum energy
    Vacuum energy is an underlying background energy that exists in space even when the space is devoid of matter . The concept of vacuum energy has been deduced from the concept of virtual particles, which is itself derived from the energy-time uncertainty principle...

     with an unusual perfect fluid equation of state
    Equation of state
    In physics and thermodynamics, an equation of state is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions...

  • 1938 — Paul Dirac
    Paul Dirac
    Paul Adrien Maurice Dirac, OM, FRS was an English theoretical physicist who made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics...

     suggests the large numbers hypothesis
    Dirac large numbers hypothesis
    The Dirac large numbers hypothesis is an observation made by Paul Dirac in 1937 relating ratios of size scales in the Universe to that of force scales. The ratios constitute very large, dimensionless numbers: some 40 orders of magnitude in the present cosmological epoch...

    , that the gravitational constant may be small because it is decreasing slowly with time
  • 1948 — Ralph Alpher, Hans Bethe
    Hans Bethe
    Hans Albrecht Bethe was a German-American nuclear physicist, and Nobel laureate in physics for his work on the theory of stellar nucleosynthesis. A versatile theoretical physicist, Bethe also made important contributions to quantum electrodynamics, nuclear physics, solid-state physics and...

     ("in absentia"), and George Gamow
    George Gamow
    George Gamow , born Georgiy Antonovich Gamov , was a Russian-born theoretical physicist and cosmologist. He discovered alpha decay via quantum tunneling and worked on radioactive decay of the atomic nucleus, star formation, stellar nucleosynthesis, Big Bang nucleosynthesis, cosmic microwave...

     examine element synthesis in a rapidly expanding and cooling universe, and suggest that the elements were produced by rapid neutron
    Neutron
    The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...

     capture
  • 1948 — Hermann Bondi
    Hermann Bondi
    Sir Hermann Bondi, KCB, FRS was an Anglo-Austrian mathematician and cosmologist. He is best known for developing the steady-state theory of the universe with Fred Hoyle and Thomas Gold as an alternative to the Big Bang theory, but his most lasting legacy will probably be his important...

    , Thomas Gold
    Thomas Gold
    Thomas Gold was an Austrian-born astrophysicist, a professor of astronomy at Cornell University, a member of the U.S. National Academy of Sciences, and a Fellow of the Royal Society . Gold was one of three young Cambridge scientists who in the 1950s proposed the now mostly abandoned 'steady...

    , and Fred Hoyle
    Fred Hoyle
    Sir Fred Hoyle FRS was an English astronomer and mathematician noted primarily for his contribution to the theory of stellar nucleosynthesis and his often controversial stance on other cosmological and scientific matters—in particular his rejection of the "Big Bang" theory, a term originally...

     propose steady state
    Steady State theory
    In cosmology, the Steady State theory is a model developed in 1948 by Fred Hoyle, Thomas Gold, Hermann Bondi and others as an alternative to the Big Bang theory...

     cosmologies based on the perfect cosmological principle
  • 1948 — George Gamow
    George Gamow
    George Gamow , born Georgiy Antonovich Gamov , was a Russian-born theoretical physicist and cosmologist. He discovered alpha decay via quantum tunneling and worked on radioactive decay of the atomic nucleus, star formation, stellar nucleosynthesis, Big Bang nucleosynthesis, cosmic microwave...

     predicts the existence of the cosmic microwave background radiation
    Cosmic microwave background radiation
    In cosmology, cosmic microwave background radiation is thermal radiation filling the observable universe almost uniformly....

     by considering the behavior of primordial radiation in an expanding universe

1950–1999

  • 1950 — Fred Hoyle
    Fred Hoyle
    Sir Fred Hoyle FRS was an English astronomer and mathematician noted primarily for his contribution to the theory of stellar nucleosynthesis and his often controversial stance on other cosmological and scientific matters—in particular his rejection of the "Big Bang" theory, a term originally...

     coins the term "Big Bang", saying that it was not derisive; it was just a striking image meant to highlight the difference between that and the Steady-State model.
  • 1961 — Robert Dicke argues that carbon
    Carbon
    Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

    -based life
    Life
    Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...

     can only arise when the gravitational force is small, because this is when burning stars exist; first use of the weak anthropic principle
    Anthropic principle
    In astrophysics and cosmology, the anthropic principle is the philosophical argument that observations of the physical Universe must be compatible with the conscious life that observes it. Some proponents of the argument reason that it explains why the Universe has the age and the fundamental...

  • 1965 — Hannes Alfvén
    Hannes Alfvén
    Hannes Olof Gösta Alfvén was a Swedish electrical engineer, plasma physicist and winner of the 1970 Nobel Prize in Physics for his work on magnetohydrodynamics . He described the class of MHD waves now known as Alfvén waves...

     proposes the now-discounted concept of ambiplasma to explain baryon asymmetry
    Baryon asymmetry
    The baryon asymmetry problem in physics refers to the apparent fact that there is an imbalance in baryonic matter and antibaryonic matter in the universe. Neither the standard model of particle physics, nor the theory of general relativity provide an obvious explanation for why this should be so;...

     and supports the idea of an infinite universe.
  • 1965 — Martin Rees and Dennis Sciama analyze quasar
    Quasar
    A quasi-stellar radio source is a very energetic and distant active galactic nucleus. Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that were point-like, similar to stars, rather than...

     source count data and discover that the quasar density increases with redshift.
  • 1965 — Arno Penzias and Robert Wilson
    Robert Woodrow Wilson
    For the American President, see Woodrow Wilson.Robert Woodrow Wilson is an American astronomer, 1978 Nobel laureate in physics, who with Arno Allan Penzias discovered in 1964 the cosmic microwave background radiation...

    , astronomers at Bell Labs
    Bell Labs
    Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...

     discover the 2.7 K microwave background radiation, which earns them the 1978 Nobel Prize
    Nobel Prize
    The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...

     in Physics. Robert Dicke, James Peebles
    Jim Peebles
    Phillip James Edwin Peebles is a Canadian-American physicist and theoretical cosmologist who is currently the Albert Einstein Professor Emeritus of Science at Princeton University. Peebles was born in Winnipeg and completed his bachelor's degree at the University of Manitoba...

    , Peter Roll and David Todd Wilkinson
    David Todd Wilkinson
    David Todd Wilkinson was a world-renowned pioneer in the field of cosmology, specializing in the study of the cosmic microwave background radiation left over from the Big Bang. He was born in Hillsdale, Michigan, and earned his Ph.D. in physics at the University of Michigan under the supervision...

     interpret it as relic from the big bang.
  • 1966 — Stephen Hawking
    Stephen Hawking
    Stephen William Hawking, CH, CBE, FRS, FRSA is an English theoretical physicist and cosmologist, whose scientific books and public appearances have made him an academic celebrity...

     and George Ellis show that any plausible general relativistic cosmology is singular
    Gravitational singularity
    A gravitational singularity or spacetime singularity is a location where the quantities that are used to measure the gravitational field become infinite in a way that does not depend on the coordinate system...

  • 1966 — James Peebles
    Jim Peebles
    Phillip James Edwin Peebles is a Canadian-American physicist and theoretical cosmologist who is currently the Albert Einstein Professor Emeritus of Science at Princeton University. Peebles was born in Winnipeg and completed his bachelor's degree at the University of Manitoba...

     shows that the hot Big Bang
    Big Bang
    The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

     predicts the correct helium abundance
  • 1967 — Andrei Sakharov
    Andrei Sakharov
    Andrei Dmitrievich Sakharov was a Soviet nuclear physicist, dissident and human rights activist. He earned renown as the designer of the Soviet Union's Third Idea, a codename for Soviet development of thermonuclear weapons. Sakharov was an advocate of civil liberties and civil reforms in the...

     presents the requirements for baryogenesis
    Baryogenesis
    In physical cosmology, baryogenesis is the generic term for hypothetical physical processes that produced an asymmetry between baryons and antibaryons in the very early universe, resulting in the substantial amounts of residual matter that make up the universe today.Baryogenesis theories employ...

    , a baryon
    Baryon
    A baryon is a composite particle made up of three quarks . Baryons and mesons belong to the hadron family, which are the quark-based particles...

    -antibaryon
    Antimatter
    In 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...

     asymmetry
    Asymmetry
    Asymmetry is the absence of, or a violation of, symmetry.-In organisms:Due to how cells divide in organisms, asymmetry in organisms is fairly usual in at least one dimension, with biological symmetry also being common in at least one dimension....

     in the universe
  • 1967 — John Bahcall, Wal Sargent, and Maarten Schmidt
    Maarten Schmidt
    Maarten Schmidt is a Dutch astronomer who measured the distances of quasars.Born in Groningen, The Netherlands, Schmidt studied with Jan Hendrik Oort. He earned his Ph.D. degree from Leiden Observatory in 1956....

     measure the fine-structure splitting of spectral line
    Spectral line
    A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from a deficiency or excess of photons in a narrow frequency range, compared with the nearby frequencies.- Types of line spectra :...

    s in 3C191 and thereby show that the fine-structure constant
    Fine-structure constant
    In physics, the fine-structure constant is a fundamental physical constant, namely the coupling constant characterizing the strength of the electromagnetic interaction. Being a dimensionless quantity, it has constant numerical value in all systems of units...

     does not vary significantly with time
  • 1968 — Brandon Carter
    Brandon Carter
    Brandon Carter, FRS is an Australian theoretical physicist, best known for his work on the properties of black holes and for being the first to name and employ the anthropic principle in its contemporary form. He is a researcher at the Meudon campus of the Laboratoire Univers et Théories, part of...

     speculates that perhaps the fundamental constants of nature must lie within a restricted range to allow the emergence of life; first use of the strong anthropic principle
  • 1969 — Charles Misner formally presents the Big Bang horizon problem
    Horizon problem
    The horizon problem is a problem with the standard cosmological model of the Big Bang which was identified in the 1970s. It points out that different regions of the universe have not "contacted" each other because of the great distances between them, but nevertheless they have the same temperature...

  • 1969 — Robert Dicke formally presents the Big Bang flatness problem
  • 1973 — Edward Tryon
    Edward Tryon
    Edward P. Tryon is an American scientist from Terre Haute, Indiana and a professor of physics at Hunter College in Manhattan. His specialization is in theoretical quark models, theoretical general relativity, and cosmology. In 1973 he proposed that the universe is a large-scale vacuum energy...

     proposes that the universe may be a large scale quantum mechanical
    Quantum mechanics
    Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

     vacuum fluctuation where positive mass-energy is balanced by negative gravitational potential energy
    Potential energy
    In physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...

  • 1974 — Robert Wagoner, William Fowler
    William Alfred Fowler
    William Alfred "Willy" Fowler was an American astrophysicist and winner of the Nobel Prize for Physics in 1983. He should not be confused with the British astronomer Alfred Fowler....

    , and Fred Hoyle show that the hot Big Bang predicts the correct deuterium
    Deuterium
    Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...

     and lithium
    Lithium
    Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...

     abundances
  • 1976 — Alex Shlyakhter uses samarium
    Samarium
    Samarium is a chemical element with the symbol Sm, atomic number 62 and atomic weight 150.36. It is a moderately hard silvery metal which readily oxidizes in air. Being a typical member of the lanthanide series, samarium usually assumes the oxidation state +3...

     ratios from the Oklo
    Oklo
    Oklo is a region near the town of Franceville, in the Haut-Ogooué province of the Central African state of Gabon. Several natural nuclear fission reactors were discovered in the uranium mines in the region in 1972.-History:...

     prehistoric natural nuclear fission reactor
    Natural nuclear fission reactor
    A natural nuclear fission reactor is a uranium deposit where analysis of isotope ratios has shown that self-sustaining nuclear chain reactions have occurred. The existence of this phenomenon was discovered in 1972 at Oklo in Gabon, Africa, by French physicist Francis Perrin. The conditions under...

     in Gabon
    Gabon
    Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...

     to show that some laws of physics have remained unchanged for over two billion years
  • 1977 — Gary Steigman, David Schramm, and James Gunn examine the relation between the primordial helium abundance and number of neutrinos and claim that at most five lepton
    Lepton
    A lepton is an elementary particle and a fundamental constituent of matter. The best known of all leptons is the electron which governs nearly all of chemistry as it is found in atoms and is directly tied to all chemical properties. Two main classes of leptons exist: charged leptons , and neutral...

     families can exist.
  • 1981 — Viacheslav Mukhanov and G. Chibisov propose that quantum fluctuations could lead to large scale structure in an inflationary
    Cosmic inflation
    In physical cosmology, cosmic inflation, cosmological inflation or just inflation is the theorized extremely rapid exponential expansion of the early universe by a factor of at least 1078 in volume, driven by a negative-pressure vacuum energy density. The inflationary epoch comprises the first part...

     universe
  • 1981 — Alan Guth
    Alan Guth
    Alan Harvey Guth is an American theoretical physicist and cosmologist. Guth has researched elementary particle theory...

     proposes the inflation
    Cosmic inflation
    In physical cosmology, cosmic inflation, cosmological inflation or just inflation is the theorized extremely rapid exponential expansion of the early universe by a factor of at least 1078 in volume, driven by a negative-pressure vacuum energy density. The inflationary epoch comprises the first part...

    ary Big Bang universe as a possible solution to the horizon and flatness problems
  • 1990 — Preliminary results from NASA
    NASA
    The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

    's COBE
    COBE
    The COsmic Background Explorer , also referred to as Explorer 66, was a satellite dedicated to cosmology. Its goals were to investigate the cosmic microwave background radiation of the universe and provide measurements that would help shape our understanding of the cosmos.This work provided...

     mission confirm the cosmic microwave background radiation
    Cosmic microwave background radiation
    In cosmology, cosmic microwave background radiation is thermal radiation filling the observable universe almost uniformly....

     is an isotropic blackbody to an astonishing one part in 105 precision, thus eliminating the possibility of an integrated starlight model proposed for the background by steady state enthusiasts.
  • 1990s — Ground based cosmic microwave background experiments measure the first peak, determine that the universe is geometrically flat
    Shape of the Universe
    The shape of the universe is a matter of debate in physical cosmology over the local and global geometry of the universe which considers both curvature and topology, though, strictly speaking, it goes beyond both...

    .
  • 1998 — Controversial evidence for the fine structure constant varying over the lifetime of the universe is first published.
  • 1998 — Adam Riess
    Adam Riess
    Adam Guy Riess is an American astrophysicist at Johns Hopkins University and the Space Telescope Science Institute and is widely known for his research in using supernovae as Cosmological Probes. Riess shared both the 2006 Shaw Prize in Astronomy and the 2011 Nobel Prize in Physics with Saul...

    , Saul Perlmutter
    Saul Perlmutter
    Saul Perlmutter is an American astrophysicist at the Lawrence Berkeley National Laboratory and a professor of physics at the University of California, Berkeley. He is a member of the American Academy of Arts & Sciences, and was elected a Fellow of the American Association for the Advancement of...

     and others discover the cosmic acceleration
    Dark energy
    In physical cosmology, astronomy and celestial mechanics, dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe. Dark energy is the most accepted theory to explain recent observations that the universe appears to be expanding...

     in observations of Type Ia supernova
    Type Ia supernova
    A Type Ia supernova is a sub-category of supernovae, which in turn are a sub-category of cataclysmic variable stars, that results from the violent explosion of a white dwarf star. A white dwarf is the remnant of a star that has completed its normal life cycle and has ceased nuclear fusion...

    e providing the first evidence for a non-zero cosmological constant
    Cosmological constant
    In physical cosmology, the cosmological constant was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe...

    .
  • 1999 — Measurements of the cosmic microwave background radiation
    Cosmic microwave background radiation
    In cosmology, cosmic microwave background radiation is thermal radiation filling the observable universe almost uniformly....

     (most notably by the BOOMERanG experiment
    BOOMERanG experiment
    The BOOMERanG experiment measured the cosmic microwave background radiation of a part of the sky during three sub-orbital balloon flights. It was the first experiment to make large, high fidelity images of the CMB temperature anisotropies...

     see Mauskopf et al., 1999, Melchiorri et al., 1999, de Bernardis et al. 2000) provide evidence for oscillations (peaks) in the anisotropy
    Anisotropy
    Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies identical properties in all directions. It can be defined as a difference, when measured along different axes, in a material's physical or mechanical properties An example of anisotropy is the light...

     angular spectrum as expected in the standard model of cosmological structure formation. These results indicates that the geometry of the universe is flat. Together with large scale structure data, this provides complementary evidence for a non-zero cosmological constant.

Since 2000

  • 2002 — The Cosmic Background Imager
    Cosmic Background Imager
    The Cosmic Background Imager was a 13-element interferometer perched at an elevation of 5,080 metres at Llano de Chajnantor Observatory in the Chilean Andes...

     (CBI) in Chile
    Chile
    Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

     obtained images of the cosmic microwave background radiation with the highest angular resolution of 4 arc minutes. It also obtained the anisotropy spectrum at high-resolution not covered before up to l ~ 3000. It found a slight excess in power at high-resolution (l > 2500) not yet completely explained, the so-called "CBI-excess".
  • 2003 — NASA's WMAP obtained full-sky detailed pictures of the cosmic microwave background radiation. The image can be interpreted to indicate that the universe is 13.7 billion years old (within one percent error) and confirm that the Lambda-CDM model
    Lambda-CDM model
    ΛCDM or Lambda-CDM is an abbreviation for Lambda-Cold Dark Matter, which is also known as the cold dark matter model with dark energy...

     and the inflation
    Cosmic inflation
    In physical cosmology, cosmic inflation, cosmological inflation or just inflation is the theorized extremely rapid exponential expansion of the early universe by a factor of at least 1078 in volume, driven by a negative-pressure vacuum energy density. The inflationary epoch comprises the first part...

    ary theory are correct.
  • 2003 — The Sloan Great Wall
    Sloan Great Wall
    The Sloan Great Wall is a cosmic structure formed by a giant wall of galaxies , and to the present day it is the largest known structure in the universe. Its discovery was announced on October 20, 2003 by J. Richard Gott III of Princeton University and Mario Jurić and their colleagues, based on...

     is discovered.
  • 2004 — The Degree Angular Scale Interferometer (DASI) first obtained the E-mode polarization spectrum of the cosmic microwave background radiation.
  • 2006 — The long-awaited three-year WMAP results are released, confirming previous analysis, correcting several points, and including polarization data.


See also

  • Timeline of the Big Bang
    Timeline of the Big Bang
    This timeline of the Big Bang describes the history of the universe according to the prevailing scientific theory of how the universe came into being, using the cosmological time parameter of comoving coordinates...

  • List of cosmologists
  • Cosmology@Home
    Cosmology@Home
    Cosmology@Home is a BOINC distributed computing project, run at the Departments of Astronomy and Physics at the University of Illinois at Urbana-Champaign.- Goals :...

  • Non-standard cosmology
    Non-standard cosmology
    A non-standard cosmology is any physical cosmological model of the universe that has been, or still is, proposed as an alternative to the big bang model of standard physical cosmology...

  • Buddhist cosmology
    Buddhist cosmology
    Buddhist cosmology is the description of the shape and evolution of the Universe according to the canonical Buddhist scriptures and commentaries.-Introduction:...

  • Jain cosmology
    Jain cosmology
    Jain cosmology is the description of the shape and functioning of the physical and metaphysical Universe and its constituents according to Jainism, which includes the canonical Jain texts, commentaries and the writings of the Jain philosopher-monks...

  • Jainism and non-creationism
    Jainism and non-creationism
    Jainism does not support belief in a creator deity. According to Jain doctrine, the universe and its constituents - soul, matter, space, time, and principles of motion have always existed . All the constituents and actions are governed by universal natural laws...

  • Hindu cosmology
    Hindu cosmology
    In Hindu cosmology the universe is, according to Hindu mythology and Vedic cosmology, cyclically created and destroyed.-Description:The Hindu cosmology and timeline is the closest to modern scientific timelines and even more which might indicate that the Big Bang is not the beginning of everything...

  • Maya mythology
    Maya mythology
    Mayan mythology is part of Mesoamerican mythology and comprises all of the Mayan tales in which personified forces of nature, deities, and the heroes interacting with these play the main roles...