is the discipline that deals with the nature of the Universe as a whole.
of the Universe at large, as well as the natural laws that keep it in order. Modern cosmology is dominated by the
. Related studies include
, which maps the features of the Universe. Cosmology is also connected to
. However, they are contrasted in that while the former is concerned with the Universe in its entirety, the latter deals with individual celestial objects.
have played a central role in shaping the understanding of the universe through scientific observation and experiment. What is known as
shaped through both mathematics and observation the analysis of the whole universe. It is generally understood to begin with the
Physical cosmologists propose that the history of the universe has been governed entirely by physical laws. Such theories of an impersonal universe governed by physical laws were first proposed by
. Between the domains of religion and science, stands the
. This ancient field of study seeks to draw
conclusions about the nature of the universe, man, a supernatural creator and/or their relationships based on the extension of some set of presumed facts borrowed from spiritual experience and/or observation.
Metaphysical cosmology has also been described as the placing of man in the universe in relationship to all other entities. This is exampled by the observation made by
of a man's place in that relationship: "He who does not know what the world is does not know where he is, and he who does not know for what purpose the world exists, does not know who he is, nor what the world is."
. In some cases, views about the creation (
is distinguished from religion in its less tradition-bound construction and reliance on modern "intellectual understanding" rather than
| Name |
Author and date |
Classification |
Remarks |
| Babylonian cosmology |
Babylonian literature (1900-1200 BC) |
Plurality of heavens and earths |
The EarthEarth 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 HeavenHeaven, the Heavens or Seven Heavens, is a common religious cosmological or metaphysical term for the physical or transcendent place from which heavenly beings originate, are enthroned or inhabit...
s are a "spatial whole, even one of round shapeThe 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 deityA 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 there is a plurality of heavens and earths. |
| Brahmanda (Hindu Cosmology) The Brahmanda Purana is one of the eighteen Mahapuranas, a genre of eighteen Hindu religious texts and has been assigned the eighteenth place in almost all the lists of the Puranas.Brahma in Sanskrit means "the biggest", anda/andam means globe...
|
Hindu RigvedaThe Rigveda is an ancient Indian sacred collection of Vedic Sanskrit hymns...
(1700–1100 BC) |
Cyclical or oscillating, Infinite in time |
The universe sustains for around 311,040,000,000,000 years, or 100 Years of Brahma. There is a smaller period of unmanifestation in around 4 billion years, that is, one Day of Brahma. The universe cycles between expansion and total collapse. After one cycle of the life of Brahma another universe follows for infinity, each of which exists for a time period of 311 trillion 40 billion years. It also speaks of an infinite number of universes at one given point of time. The Universe expanded from a concentrated form, a point called a BinduBindu is a Sanskrit term meaning "point" or "dot". The feminine case ending is bindi which denotes a small ornamental, devotional and/or mystical dot that is cosmetically applied or affixed to the forehead in Hinduism....
. The universe, as a living entity, is bound to the perpetual cycle of birth, death, and rebirththumb|right|200px|Traditional Tibetan painting or [[Thanka]] showing the [[wheel of life]] and realms of saṃsāraSaṅsāra or Saṃsāra , , literally meaning "continuous flow", is the cycle of birth, life, death, rebirth or reincarnation within Hinduism, Buddhism, Bön, Jainism, Sikhism, and other...
. |
Atomist universeAtomism is a natural philosophy that developed in several ancient traditions. The atomists theorized that the natural world consists of two fundamental parts: indivisible atoms and empty void.According to Aristotle, atoms are indestructible and immutable and there are an infinite variety of shapes...
|
AnaxagorasAnaxagoras was a Pre-Socratic Greek philosopher. Born in Clazomenae in Asia Minor, Anaxagoras was the first philosopher to bring philosophy from Ionia to Athens. He attempted to give a scientific account of eclipses, meteors, rainbows, and the sun, which he described as a fiery mass larger than...
(500-428 BC) & later EpicurusEpicurus was an ancient Greek philosopher and the founder of the school of philosophy called Epicureanism.Only a few fragments and letters remain of Epicurus's 300 written works...
|
Infinite in extent |
The universe contains only two things: an infinite number of tiny seeds, or atomThe atom is a basic unit of matter that consists 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, and the void of infinite extent. All atoms are made of the same substance, but differ in size and shape. Objects are formed from atom aggregations and decay back into atoms. Incorporates LeucippusLeucippus or Leukippos was one of the earliest Greeks to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms — which was elaborated in greater detail by his pupil and successor, Democritus...
' principle of causalityCausality is the relationship between an event and a second event , where the second event is understood as a consequence of the first....
: "nothing happens at random; everything happens out of reason and necessity." The universe was not ruled by gods. |
| Pythagorean universe |
Philolaus Philolaus was a Greek Pythagorean and Presocratic philosopher. He argued that all matter is composed of limiting and limitless things, and that the universe is determined by numbers. He is credited with originating the theory that the earth was not the center of the universe.-Life:Philolaus is...
(d. 390 BC) |
Existence of a "Central Fire" at the center of the Universe. |
At the center of the Universe is a central fire, around which the EarthEarth 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...
, SunThe 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...
, MoonThe Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
and planetA planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s revolve uniformly. The Sun revolves around the central fire once a year, the stars are immobile. The earth in its motion maintains the same hidden face towards the central fire, hence it is never seen. This is the first known non-geocentric model of the Universe. |
| Stoic universe |
Stoics (300 BC - 200 AD) |
Island universe |
The cosmosIn 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...
is finite and surrounded by an infinite void. It is in a state of flux, as it pulsates in size and periodically passes through upheavals and conflagrations. |
| Aristotelian universe On the Heavens is Aristotle's chief cosmological treatise: it contains his astronomical theory and his ideas on the concrete workings of the terrestrial world...
|
AristotleAristotle 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...
(384-322 BC) |
Geocentric, static, steady state, finite extent, infinite time |
Spherical earth is surrounded by concentric celestial spheresThe celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus and others...
. Universe exists unchanged throughout eternity. Contains a fifth element, called aetherAccording to ancient and medieval science aether , also spelled æther or ether, is the material that fills the region of the universe above the terrestrial sphere.-Mythological origins:...
(later known as quintessence), added to the four Classical elementMany philosophies and worldviews have a set of classical elements believed to reflect the simplest essential parts and principles of which anything consists or upon which the constitution and fundamental powers of anything are based. Most frequently, classical elements refer to ancient beliefs...
s. |
| Aristarchean universe |
Aristarchus 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...
(circa 280 BC) |
Heliocentric |
Earth rotates daily on its axis and revolves annually about the sun in a circular orbit. Sphere of fixed stars is centered about the sun. |
Ptolemaic modelIn 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...
(based on Aristotelian universe) |
PtolemyClaudius 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...
(2nd century AD) |
Geocentric |
Universe orbits about a stationary Earth. Planets move in circular epicycles, each having a center that moved in a larger circular orbit (called an eccentric or a deferent) around a center-point near the Earth. The use of equantEquant is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of heavenly bodies....
s added another level of complexity and allowed astronomers to predict the positions of the planets. The most successful universe model of all time, using the criterion of longevity. AlmagestThe Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt,...
(the Great System). |
| Aryabhatan model |
AryabhataAryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...
(499) |
Geocentric or Heliocentric |
The Earth rotates and the planets move in elliptical orbits, possibly around either the Earth or the Sun. It is uncertain whether the model is geocentric or heliocentric due to planetary orbits given with respect to both the Earth and the Sun. |
| Abrahamic universe |
Medieval philosophersMedieval philosophy is the philosophy in the era now known as medieval or the Middle Ages, the period roughly extending from the fall of the Western Roman Empire in the fifth century AD to the Renaissance in the sixteenth century...
(500-1200) |
Finite in time |
A universeThe 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...
that is finite in timeTime 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 has a beginning is proposed by the Christian philosopherChristian philosophy may refer to any development in philosophy that is characterised by coming from a Christian tradition.- Origins of Christian philosophy :...
, 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...
, who argues against the ancient Greek notion of an infinite past. Logical arguments supporting a finite universe are developed by the early Muslim philosopherEarly Islamic philosophy or classical Islamic philosophy is a period of intense philosophical development beginning in the 2nd century AH of the Islamic calendar and lasting until the 6th century AH...
Alkindus' , 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...
, the Jewish philosopherJewish philosophy , includes all philosophy carried out by Jews, or, in relation to the religion of Judaism. Jewish philosophy, until modern Enlightenment and Emancipation, was pre-occupied with attempts to reconcile coherent new ideas into the tradition of Rabbinic Judaism; thus organizing...
Saadia GaonSaʻadiah 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...
and the Muslim theologianʿIlm al-Kalām is the Islamic philosophical discipline of seeking theological principles through dialectic. Kalām in Islamic practice relates to the discipline of seeking theological knowledge through debate and argument. A scholar of kalām is referred to as a mutakallim...
AlgazelAbu 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....
. |
| Multiversal cosmology |
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....
(1149–1209) |
Multiverse The multiverse is the hypothetical set of multiple possible universes that together comprise all of reality.Multiverse may also refer to:-In fiction:* Multiverse , the fictional multiverse used by DC Comics...
, multiple worlds & universes |
There exists an infinite outer space beyond the known world, and God has the power to fill the vacuum with an infinite number of universes. |
| Maragha models |
Maragha schoolMaragheh observatory is an astronomical observatory which was established in 1259 CE by Nasir al-Din al-Tusi, an Iranian scientist and astronomer...
(1259–1528) |
Geocentric |
Various modifications to Ptolemaic model and Aristotelian universe, including rejection of equantEquant is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of heavenly bodies....
and eccentricsIn the Ptolemaic system of astronomy, the epicycle was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets...
at Maragheh observatoryMaragheh observatory is an astronomical observatory which was established in 1259 CE by Nasir al-Din al-Tusi, an Iranian scientist and astronomer...
, and introduction of Tusi-coupleThe Tusi-couple is a mathematical device in which a small circle rotates inside a larger circle twice the diameter of the smaller circle. Rotations of the circles cause a point on the circumference of the smaller circle to oscillate back and forth in linear motion along a diameter of the larger...
by Al-TusiKhawaja 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...
. Alternative models later proposed, including the first accurate lunarThe Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
model by Ibn al-ShatirAla Al-Din Abu'l-Hasan Ali Ibn Ibrahim Ibn al-Shatir was an Arab Muslim astronomer, mathematician, engineer and inventor who worked as muwaqqit at the Umayyad Mosque in Damascus, Syria.-Astronomy:...
, a model rejecting stationary Earth in favour of Earth's rotation by Ali KuşçuAla al-Dīn Ali ibn Muhammed , known as Ali Qushji , was a Turkic or Persian astronomer, mathematician and physicist originally from Samarkand, who settled in the Ottoman Empire some time before 1472...
, and planetary model incorporating "circular inertiaInertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...
" by Al-BirjandiAbd Ali ibn Muhammad ibn Husayn Birjandi was a prominent 16th century Persian astronomer, mathematician and physicist who lived in Birjand, Iran.- His works :...
. |
| Nilakanthan model |
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...
(1444–1544) |
Geocentric and Heliocentric |
A universe in which the planets orbit the Sun and the Sun orbits the Earth, similar to the later 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...
. |
| Copernican universe 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...
|
Nicolaus CopernicusNicolaus 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....
(1543) |
Heliocentric with circular planetary orbits |
First clearly described heliocentric model, in De revolutionibus orbium coelestium De revolutionibus orbium coelestium is the seminal work on the heliocentric theory of the Renaissance astronomer Nicolaus Copernicus...
. |
| 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...
|
Tycho BraheTycho Brahe , born Tyge Ottesen Brahe, was a Danish nobleman known for his accurate and comprehensive astronomical and planetary observations...
(1546–1601) |
Geocentric and Heliocentric |
A universe in which the planets orbit the Sun and the Sun orbits the Earth, similar to the earlier Nilakanthan model 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...
. |
| Keplerian |
Johann Kepler (1571–1630) |
Heliocentric with elliptical planetary orbits |
Kepler's discoveries, marrying mathematics and physics, provided the foundation for our present conception of the Solar system, but distant stars were still seen as objects in a thin, fixed celestial sphere. |
| Static Newtonian |
Sir Isaac NewtonSir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...
(1642–1727) |
Static A static universe, also referred to as a "stationary" or "Einstein" universe, is a model in which space is neither expanding nor contracting. Albert Einstein proposed such a model as his preferred cosmology in 1917...
(evolving), steady state, infinite |
Every particle in the universe attracts every other particle. Matter on the large scale is uniformly distributed. Gravitationally balanced but unstable. |
| Cartesian Vortex universe |
René DescartesRené Descartes ; was a French philosopher and writer who spent most of his adult life in the Dutch Republic. He has been dubbed the 'Father of Modern Philosophy', and much subsequent Western philosophy is a response to his writings, which are studied closely to this day...
17th century |
Static (evolving), steady state, infinite |
A system of huge swirling whirlpools of aethereal or fine matter produces what we would call gravitational effects. His vacuum was not empty. All space was filled with matter that swirled around in large and small vortices. |
| Hierarchical universe |
Immanuel KantImmanuel Kant was a German philosopher from Königsberg , researching, lecturing and writing on philosophy and anthropology at the end of the 18th Century Enlightenment....
, Johann Lambert 18th century |
Static (evolving), steady state, infinite |
Matter is clustered on ever larger scales of hierarchy. Matter is endlessly being recycled. |
| Einstein Universe with a cosmological constant A static universe, also referred to as a "stationary" or "Einstein" universe, is a model in which space is neither expanding nor contracting. Albert Einstein proposed such a model as his preferred cosmology in 1917...
|
Albert EinsteinAlbert 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...
1917 |
Static (nominally). Bounded (finite) |
"Matter without motion." Contains uniformly distributed matter. Uniformly curved spherical space; based on Riemann's hypersphere. Curvature is set equal to Λ. In effect Λ is equivalent to a repulsive force which counteracts gravity. Unstable. |
| 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...
|
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...
1917 |
ExpandingThe 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...
flat spaceThe 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...
.
Steady state.
Λ > 0 |
"Motion without matter." Only apparently static. Based on Einstein's General 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...
. Space expands with constant accelerationThe accelerating universe is the observation that the universe appears to be expanding at an increasing rate, which in formal terms means that the cosmic scale factor a has a positive second derivative, implying that the velocity at which a given galaxy is receding from us should be continually...
. Scale factorThe scale factor or cosmic scale factor parameter of the Friedmann equations is a function of time which represents the relative expansion of the universe. It is sometimes called the Robertson-Walker scale factor...
(radius of universe) increases exponentially, i.e. constant inflationIn 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...
. |
| MacMillan universe |
William Duncan MacMillan William Duncan MacMillan was an American mathematician and astronomer.He was born in La Crosse, Wisconsin to D. D. MacMillan, who was in the lumber business, and Mary Jane MacCrea. He had a sister and two brothers; the last would later becoming managers of Cargill Elevator company of...
1920s |
Static &
steady state |
New matter is created from radiation In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
. Starlight is perpetually recycled into new matter particles. |
Friedmann universeThe Friedmann equations are a set of equations in physical cosmology that govern the expansion of space in homogeneous and isotropic models of the universe within the context of general relativity...
of spherical space |
Alexander Friedmann 1922 |
Spherical expanding space.
k= +1 ; no Λ |
Positive curvature. Curvature constant k = +1
ExpandsThe 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...
then recollapsesIn physical cosmology, the Big Crunch is one possible scenario for the ultimate fate of the universe, in which the metric expansion of space eventually reverses and the universe recollapses, ultimately ending as a black hole singularity.- Overview :...
. Spatially closedThe 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...
(finite). |
Friedmann universeThe Friedmann equations are a set of equations in physical cosmology that govern the expansion of space in homogeneous and isotropic models of the universe within the context of general relativity...
of hyperbolic space |
Alexander Friedmann 1924 |
Hyperbolic In mathematics, hyperbolic space is a type of non-Euclidean geometry. Whereas spherical geometry has a constant positive curvature, hyperbolic geometry has a negative curvature: every point in hyperbolic space is a saddle point...
expanding space.
k= -1 ; no Λ |
Negative curvatureThe 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...
. Said to be infinite (but ambiguous). Unbounded. Expands forever. |
Dirac large numbers hypothesisThe 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...
|
Paul DiracPaul 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...
1930s |
Expanding |
Demands a large variation in G, which decreases with time. Gravity weakens as universe evolves. |
| Friedmann zero-curvature, a.k.a. the Einstein-DeSitter universe |
Einstein & DeSitter 1932 |
Expanding flat space.
k= 0 ; Λ = 0
Critical density |
Curvature constant k = 0. Said to be infinite (but ambiguous). 'Unbounded cosmos of limited extent.' Expands forever. 'Simplest' of all known universes. Named after but not considered by Friedmann. Has a deceleration term q =½ which means that its expansion rate slows down. |
The original Big BangThe 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...
. a.k.a. Friedmann-Lemaître Model |
Georges LemaîtreMonsignor 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...
1927-29 |
|
Λ > 0
Λ > >Gravity|
Λ is positive and has a magnitude greater than Gravity. Universe has initial high density state ('primeval atom'). Followed by a two stage expansion. Λ is used to destabilize the universe. (Lemaître is considered to be the father of the big bang model.) |
Oscillating universe
(a.k.a. Friedmann-Einstein; was latter's 1st choice after rejecting his own 1917 model) |
Favored by Friedmann
1920s |
Expanding and contracting in cycles |
Time is endless and beginningless; thus avoids the beginning-of-time paradox. Perpetual cycles of big bang followed by big crunch. |
| Eddington |
Arthur Eddington 1930 |
First Static
then Expands |
Static Einstein 1917 universe with its instability disturbed into expansion mode; with relentless matter dilution becomes a DeSitter universe. Λ dominates gravity. |
| Milne universe of kinematic relativity |
Edward Milne, 1933, 1935;
William H. McCrea,
1930s |
Kinematic expansion with NO space expansion |
Rejects general relativity and the expanding space paradigm. Gravity not included as initial assumption. Obeys cosmological principle & rules of special relativitySpecial 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...
. The Milne expanding universe consists of a finite spherical cloud of particles (or galaxies) that expands WITHIN flat space which is infinite and otherwise empty. It has a center and a cosmic edge (the surface of the particle cloud) which expands at light speed. His explanation of gravity was elaborate and unconvincing. For instance, his universe has an infinite number of particles, hence infinite mass, within a finite cosmic volume. |
| Friedmann-Lemaître-Robertson-Walker class of models |
Howard Robertson Howard Percy Robertson was an American mathematician and physicist known for contributions related to physical cosmology and the uncertainty principle...
, Arthur WalkerArthur Geoffrey Walker was a leading mathematician who made important contributions to physics and physical cosmology. He was born in Watford, Hertfordshire, England....
, 1935 |
Uniformly expanding |
Class of universes that are homogenous and isotropic. Spacetime separates into uniformly curved space and cosmic time common to all comoving observers. The formulation system is now known as the FLRW or Robertson-Walker metrics of cosmic time and curved space. |
| Steady-state 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...
expanding (Bondi & Gold) |
Herman Bondi, Thomas GoldThomas 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...
1948 |
Expanding, steady state, infinite |
Matter creation rate maintains constant density. Continuous creation out of nothing from nowhere. Exponential expansion. Deceleration term q = -1. |
| Steady-state expanding (Hoyle) |
Fred HoyleSir 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...
1948 |
Expanding, steady state; but unstable |
Matter creation rate maintains constant density. But since matter creation rate must be exactly balanced with the space expansion rate the system is unstable. |
| Ambiplasma |
Hannes AlfvénHannes 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...
1965 Oskar KleinOskar Benjamin Klein was a Swedish theoretical physicist.Klein was born in Danderyd outside Stockholm, son of the chief rabbi of Stockholm, Dr. Gottlieb Klein from Homonna in Hungary and Antonie Levy...
|
Cellular universe, expanding by means of matter-antimatter annihilation |
Based on the concept of plasma cosmology Plasma cosmology is a non-standard cosmology generally attributed to a 1970 Nobel laureate named Hannes Alfvén. Ionized gases, or plasmas, play the central part in plasma cosmology's explanation for the development of the universe, thus dominated largely by electrodynamic forces rather than...
. The universe is viewed as meta-galaxies divided by double layersA double layer is a structure in a plasma and consists of two parallel layers with opposite electrical charge. The sheets of charge cause a strong electric field and a correspondingly sharp change in voltage across the double layer. Ions and electrons which enter the double layer are accelerated,...
—hence its bubble-like nature. Other universes are formed from other bubbles. Ongoing cosmic matter-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...
annihilationAnnihilation is defined as "total destruction" or "complete obliteration" of an object; having its root in the Latin nihil . A literal translation is "to make into nothing"....
s keep the bubbles separated and moving apart preventing them from interacting. |
| Brans-Dicke |
Carl H. Brans Carl Henry Brans is an American mathematical physicist best known for his research into the theoretical underpinnings of gravitation elucidated in his most widely publicized work, the Brans–Dicke theory....
; Robert H. DickeRobert Henry Dicke was an American physicist who made important contributions to the fields of astrophysics, atomic physics, cosmology and gravity.-Biography:...
|
Expanding |
Based on Mach's principle In theoretical physics, particularly in discussions of gravitation theories, Mach's principle is the name given by Einstein to an imprecise hypothesis often credited to the physicist and philosopher Ernst Mach....
. G varies with time as universe expands. "But nobody is quite sure what Mach's principle actually means." |
Cosmic inflationIn 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...
|
Alan GuthAlan Harvey Guth is an American theoretical physicist and cosmologist. Guth has researched elementary particle theory...
1980 |
Big BangThe 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...
with modification to solve horizon problemThe 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...
and flatness problem. |
Based on the concept of hot inflation. The universe is viewed as a multiple quantum flux —hence its bubble-like nature. Other universes are formed from other bubbles. Ongoing cosmic expansion kept the bubbles separated and moving apart preventing them from interacting. |
| Eternal Inflation The Chaotic Inflation theory is a variety of the inflationary universe model, which is itself an outgrowth of the Big Bang theory. Chaotic Inflation, proposed by physicist Andrei Linde, models our universe as one of many that grew as part of a multiverse owing to a vacuum that had not decayed to...
(a multiple universe model) |
Andreï LindeAndrei Dmitriyevich Linde is a Russian-American theoretical physicist and professor of Physics at Stanford University. Dr. Linde is best known for his work on the concept of the inflationary universe. He received his Bachelor of Science degree from Moscow State University. In 1975, Linde was...
1983 |
Big Bang with cosmic inflationIn 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...
|
A multiverse The multiverse is the hypothetical set of multiple possible universes that together comprise all of reality.Multiverse may also refer to:-In fiction:* Multiverse , the fictional multiverse used by DC Comics...
, based on the concept of cold inflation, in which inflationary events occur at random each with independent initial conditions; some expand into bubble universes supposedly like our entire cosmos. Bubbles nucleate in a spacetime foamQuantum foam, also referred to as spacetime foam, is a concept in quantum mechanics, devised by John Wheeler in 1955. The foam is supposed to be the foundations of the fabric of the universe. Additionally, it can be used as a qualitative description of subatomic spacetime turbulence at extremely...
. |
| Cyclic model A cyclic model is any of several cosmological models in which the universe follows infinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 theorized a universe following an eternal series of oscillations, each beginning with a...
|
Paul Steinhardt Paul J. Steinhardt is the Albert Einstein Professor of Science at Princeton University and a professor of theoretical physics. He received his B.S. at the California Institute of Technology and his Ph.D. in Physics at Harvard University...
; Neil TurokNeil Geoffrey Turok is the Director of Perimeter Institute for Theoretical Physics. He is the son of Mary and Ben Turok, activists in the anti-apartheid movement and the African National Congress.-Career:...
2002 |
Expanding and contracting in cycles; M theory. |
Two parallel orbifoldIn the mathematical disciplines of topology, geometry, and geometric group theory, an orbifold is a generalization of a manifold...
planes or M-branesIn theoretical physics, a membrane, brane, or p-brane is a spatially extended mathematical concept that appears in string theory and related theories...
collide periodically in a higher dimensional space. With quintessenceIn physics, quintessence is a hypothetical form of dark energy postulated as an explanation of observations of an accelerating universe. It has been proposed by some physicists to be a fifth fundamental force...
or dark energyIn 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...
|
| Cyclic model A cyclic model is any of several cosmological models in which the universe follows infinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 theorized a universe following an eternal series of oscillations, each beginning with a...
|
Lauris Baum;Paul FramptonPaul Frampton is a particle phenomenologist.Since 1996, he is the Louis D. Rubin, Jr. Distinguished Professor of physics and astronomy, at the University of North Carolina...
2007 |
Solution of Tolman's entropy problem |
Phantom dark energy Phantom energy is a hypothetical form of dark energy with equation of state \! w Phantom energy is a hypothetical form of dark energy with equation of state...
fragments universe into large number of disconnected patches. Our patch contracts containing only dark energy with zero entropyEntropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...
. |
Table notes: the term "static" simply means not expanding and not contracting. Symbol G represents Newton's
Physical cosmology is the branch of physics and astrophysics that deals with the study of the physical origins and evolution of the Universe. It also includes the study of the nature of the Universe on its very largest scales. In its earliest form it was what is now known as
. The Greek philosophers
proposed different cosmological theories. In particular, the geocentric Ptolemaic system was the accepted theory to explain the motion of the heavens until
proposed a heliocentric system in the 16th century. This is known as one of the most famous examples of
, the problem of the motion of the heavens was finally solved. Newton provided a physical mechanism for Kepler's laws and his law of universal gravitation allowed the anomalies in previous systems, caused by gravitational interaction between the planets, to be resolved. A fundamental difference between Newton's cosmology and those preceding it was the
s as all the celestial bodies. This was a crucial philosophical advance in physical cosmology.
in the paper "Cosmological Considerations of the General Theory of Relativity," (although this paper was not widely available outside of Germany until the end of
). General relativity prompted
and Arthur Eddington to explore the astronomical consequences of the theory, which enhanced the growing ability of
to study very distant objects. Prior to this (and for some time afterwards), physicists assumed that the Universe was static and unchanging.
In parallel to this dynamic approach to cosmology, one long-standing debate about the structure of the cosmos was coming to a climax. Mount Wilson astronomer
star system only ; while Heber D. Curtis argued for the idea that spiral nebulae were star systems in their own right - island universes. This difference of ideas came to a climax with the organization of
at the meeting of the (US) National Academy of Sciences in Washington on 26 April 1920. The resolution of this debate came with the detection of novae in the
in 1923 and 1924. Their distance established spiral nebulae well beyond the edge of the Milky Way and has galaxies of their own.
introduced by Einstein in his 1917 paper may result in an expanding universe, depending on its value. Thus the
in 1964. These findings were a first step to rule out some of many
and WMAP satellites observing this background radiation have effectively, in many scientists' eyes, transformed cosmology from a highly speculative science into a predictive science, as these observations matched predictions made by a theory called
model. This has led many to refer to modern times as the "Golden age of cosmology."
, cosmology deals with the world as the totality of space, time and all phenomena. Historically, it has had quite a broad scope, and in many cases was founded in religion. The ancient Greeks did not draw a distinction between this use and their model for the cosmos. However, in modern use it addresses questions about the Universe which are beyond the scope of science. It is distinguished from religious cosmology in that it approaches these questions using philosophical methods (e.g.
s). Modern metaphysical cosmology tries to address questions such as: