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'{{Short description|Timeline of theories about physical cosmology}} {{For|a timeline of the cosmos (or universe)|Chronology of the universe}} {{Cosmology|history}} This '''timeline of cosmological theories''' and discoveries is a [[Chronology|chronological]] record of the development of humanity's understanding of the [[cosmos]] over the last two-plus millennia. Modern [[Cosmology|cosmological]] ideas follow the development of the [[science|scientific discipline]] of [[physical cosmology]]. ==Pre-1900== * {{circa}} '''16th century BCE'''&nbsp;– Mesopotamian cosmology has a [[Flat Earth|flat, circular Earth]] enclosed in a [[cosmic ocean]].<ref>Horowitz (1998), p. xii</ref> * {{circa}} '''15th–11th century BCE'''&nbsp;– The ''[[Rigveda]]'' of [[Hinduism]] has some cosmological hymns, particularly in the late [[Mandala 10|book 10]], notably the [[Nasadiya Sukta]] which describes the origin of the [[universe]], originating from the [[monistic]] ''[[Hiranyagarbha]]'' or "Golden Egg". [[Prakṛti|Primal matter]] remains manifest for 311.04 trillion years and [[Mahapralaya|unmanifest]] for an equal length. The universe remains manifest for [[Kalpa (time)|4.32 billion years]] and [[Pralaya|unmanifest]] for an equal length. Innumerable universes exist simultaneously. These cycles have and will last forever, driven by desires. * '''6th century BCE'''&nbsp;– The [[Babylonian Map of the World]] shows the Earth surrounded by the cosmic ocean, with seven islands arranged around it so as to form a seven-pointed star. Contemporary [[Biblical cosmology]] reflects the same view of a flat, circular Earth swimming on water and overarched by the solid vault of the [[firmament]] to which are fastened the stars. * '''6th–4th century BCE'''&nbsp;– Greek philosophers, as early as [[Anaximander]],<ref>This is a matter of debate: * {{cite journal |last1=Cornford |first1=F. M. |title=Innumerable Worlds in Presocratic Philosophy |journal=The Classical Quarterly |date=1934 |volume=28 |issue=1 |pages=1–16 |doi=10.1017/S0009838800009897 |s2cid=170168443 |language=en |issn=1471-6844}} * {{cite book |last1=Curd |first1=Patricia |last2=Graham |first2=Daniel W. |title=The Oxford Handbook of Presocratic Philosophy |date=2008 |publisher=Oxford University Press |isbn=978-0-19-972244-0 |pages=239–41 |url=https://books.google.com/books?id=lDvRCwAAQBAJ&pg=PA239 |language=en}} * {{cite book |last1=Gregory |first1=Andrew |title=Anaximander: A Re-assessment |date=2016 |publisher=Bloomsbury Publishing |isbn=978-1472506252 |pages=121–142 |chapter-url=https://books.google.com/books?id=7TE0CwAAQBAJ&pg=PA121 |language=en |chapter=7 Anaximander: One Cosmos or Many?}}</ref> introduce the idea of multiple or even infinite universes.<ref> * {{cite web |last1=Siegfried |first1=Tom |title=Long Live the Multiverse! |url=https://blogs.scientificamerican.com/observations/long-live-the-multiverse/ |website=Scientific American |language=en}} * {{cite book |last1=Siegfried |first1=Tom |title=The number of the heavens : a history of the multiverse and the quest to understand the cosmos |date=2019 |publisher=Harvard |isbn=978-0674975880 |url=https://www.hup.harvard.edu/catalog.php?isbn=978-0674975880 |chapter=Aristotle versus the Atomists |language=en}}</ref> [[Democritus]] further detailed that these worlds varied in distance, size; the presence, number and size of their suns and moons; and that they are subject to destructive collisions.<ref>"there are innumerable worlds of different sizes. In some there is neither sun nor moon, in others they are larger than in ours and others have more than one. These worlds are at irregular distances, more in one direction and less in another, and some are flourishing, others declining. Here they come into being, there they die, and they are destroyed by collision with one another. Some of the worlds have no animal or vegetable life nor any water." * {{cite book |last1=Guthrie |first1=W. K. C. |last2=Guthrie |first2=William Keith Chambers |title=A History of Greek Philosophy: Volume 2, The Presocratic Tradition from Parmenides to Democritus |date=1962 |publisher=Cambridge University Press |isbn=978-0-521-29421-8 |pages=404–06 |url=https://books.google.com/books?id=__sIfvwqVWwC&q=%22innumerable+worlds%22&pg=PA405 |language=en}} * {{cite book |last1=Vamvacas |first1=Constantine J. |title=The Founders of Western Thought – The Presocratics: A diachronic parallelism between Presocratic Thought and Philosophy and the Natural Sciences |date=2009 |publisher=Springer Science & Business Media |isbn=978-1-4020-9791-1 |pages=219–20 |url=https://books.google.com/books?id=eS-CjaJspBMC&q=%22innumerable+worlds%22&pg=PA219 |language=en}}</ref> Also during this time period, the Greeks established that the earth is spherical rather than flat.<ref>{{cite web |title=Ancient Greek Astronomy and Cosmology {{!}} Modeling the Cosmos {{!}} Articles and Essays {{!}} Finding Our Place in the Cosmos: From Galileo to Sagan and Beyond {{!}} Digital Collections {{!}} Library of Congress |url=https://www.loc.gov/collections/finding-our-place-in-the-cosmos-with-carl-sagan/articles-and-essays/modeling-the-cosmos/ancient-greek-astronomy-and-cosmology |website=Library of Congress|location=Washington, DC}}</ref><ref>{{cite web |last1=Blakemore |first1=Erin |title=Christopher Columbus Never Set Out to Prove the Earth was Round |url=https://www.history.com/news/christopher-columbus-never-set-out-to-prove-the-earth-was-round |website=History.com |language=en}}</ref> * '''4th century BCE'''&nbsp;– [[Aristotle]] proposes an [[Geocentric model|Earth-centered universe]] in which the Earth is stationary and the [[cosmos]] (or universe) is finite in extent but infinite in time. However, others like [[Philolaus]] and Hicetas rejected geocentrism.<ref>{{cite web |last1=Encyclopædia Britannica |title=heliocentrism {{!}} Definition, History, & Facts |url=https://www.britannica.com/science/heliocentrism |website=Encyclopedia Britannica |publisher=Encyclopædia Britannica |language=en |date=2019}}</ref> Plato seems to have argued that the universe did have a beginning, but Aristotle and others interpreted his words differently.<ref>{{cite book |last1=Sorabji |first1=Richard |title=The Philosophy of the Commentators, 200–600 AD: Physics |date=2005 |publisher=Cornell University Press |isbn=978-0-8014-8988-4 |page=175 |url=https://books.google.com/books?id=0QpQw8JDgQcC&pg=PA175 |language=en}}</ref> * '''4th century BCE'''&nbsp;– [[De Mundo]] – Five elements, situated in spheres in five regions, the less being in each case surrounded by the greater – namely, earth surrounded by water, water by air, air by fire, and fire by ether – make up the whole Universe.<ref name=1908DeMundo>{{cite book|url=https://archive.org/details/demundoarisrich|title=De Mundo|year=1914|author=Aristotle; Forster, E. S. (Edward Seymour); Dobson, J. F. (John Frederic)|page=[https://archive.org/details/demundoarisrich/page/2 2]|location=Oxford |publisher=The Clarendon Press}}</ref> * '''3rd century BCE'''&nbsp;– [[Aristarchus of Samos]] proposes a [[Heliocentrism|Sun-centered universe]] and Earth's rotation in its own axis. He also provides evidences for his theory from his own observations.<ref>{{Cite journal |last=D. |first=J. L. E. |date=July 1913 |title=Aristarchus of Samos: The Ancient Copernicus |url=https://www.nature.com/articles/091499a0 |journal=Nature |language=en |volume=91 |issue=2281 |pages=499–500 |doi=10.1038/091499a0 |issn=1476-4687}}</ref> * '''3rd century BCE'''&nbsp;– [[Archimedes]] in his essay ''[[The Sand Reckoner]]'', estimates the diameter of the cosmos to be the equivalent in [[Stadion (unit of length)|stadia]] of what would in modern times be called two [[light year]]s * '''2nd century BCE'''&nbsp;– [[Seleucus of Seleucia]] elaborates on Aristarchus' heliocentric universe, using the phenomenon of [[tide]]s to explain heliocentrism. Seleucus was the first to prove the heliocentric system through reasoning. Seleucus' arguments for a heliocentric cosmology were probably related to the phenomenon of tides. According to Strabo (1.1.9), Seleucus was the first to state that the tides are due to the attraction of the Moon, and that the height of the tides depends on the Moon's position relative to the Sun. Alternatively, he may have proved heliocentricity by determining the constants of a geometric model for it.<ref>{{Cite web |title=Aristarchus of Samos (310-230 BC) {{!}} High Altitude Observatory |url=https://www2.hao.ucar.edu/Education/FamousSolarPhysicists/aristarchus-samos&ved=2ahUKEwjm_LjLutX4AhWD4TgGHZO1Ae4QFnoECDgQAQ&usg=AOvVaw1vXstqc1q1ZR7yMV6oBBAB |access-date=2022-06-30 |website=www2.hao.ucar.edu}}</ref> *'''2nd century CE-5th century CE'''&nbsp;– Jain cosmology considers the loka, or [[universe]], as an uncreated entity, existing since infinity, the shape of the universe as similar to a man standing with legs apart and arm resting on his waist. This Universe, according to [[Jainism]], is broad at the top, narrow at the middle and once again becomes broad at the bottom. * {{circa}} '''2nd century BCE–3rd century CE'''&nbsp;– In [[Hindu cosmology]], the ''[[Manusmriti]]'' (1.67–80) and [[Puranas]] describe time as cyclical, with a new [[universe]] (planets and life) created by [[Brahma]] every 8.64 billion years. The universe is created, maintained, and destroyed within a ''[[Kalpa (aeon)|kalpa]]'' (day of [[Brahma]]) period lasting for 4.32 billion years, and is followed by a ''[[pralaya]]'' (night) period of partial dissolution equal in duration. In some Puranas (e.g. ''[[Bhagavata Purana]]''), a larger cycle of time is described where matter (''[[Tattva|mahat-tattva]]'' or [[Hiranyagarbha|universal womb]]) is created from primal matter (''[[Prakṛti|prakriti]]'') and root matter (''[[pradhana]]'') every 622.08 trillion years, from which [[Brahma]] is born.<ref>{{cite web |url=https://www.wisdomlib.org/definition/mahattattva |website=Wisdom Library |title=Mahattattva, Mahat-tattva: 5 definitions |date=February 10, 2021 |quote=Mahattattva (महत्तत्त्व) or simply Mahat refers to a primordial principle of the nature of both pradhāna and puruṣa, according to the 10th century Saurapurāṇa: one of the various Upapurāṇas depicting Śaivism.—[...] From the disturbed prakṛti and the puruṣa sprang up the seed of mahat, which is of the nature of both pradhāna and puruṣa. The mahattattva is then covered by the pradhāna and being so covered it differentiates itself as the sāttvika, rājasa and tāmasa-mahat. The pradhāna covers the mahat just as a seed is covered by the skin. Being so covered there spring from the three fold mahat the threefold ahaṃkāra called vaikārika, taijasa and bhūtādi or tāmasa.}}</ref> The elements of the universe are created, used by Brahma, and fully dissolved within a ''maha-kalpa'' (life of [[Brahma]]; 100 of his 360-day years) period lasting for 311.04 trillion years containing 36,000 ''kalpas'' (days) and ''pralayas'' (nights), and is followed by a ''maha-pralaya'' period of full dissolution equal in duration.<ref>{{cite book |author-last=Gupta |author-first=S. V. |year=2010 |chapter=Ch. 1.2.4 Time Measurements |editor-last1=Hull |editor-first1=Robert |editor-last2=Osgood |editor-first2=Richard M. Jr. |editor-link2=Richard M. Osgood Jr. |editor-last3=Parisi |editor-first3=Jurgen |editor-last4=Warlimont |editor-first4=Hans |title=Units of Measurement: Past, Present and Future. International System of Units |chapter-url=https://books.google.com/books?id=pHiKycrLmEQC&pg=PA7 |series=Springer Series in Materials Science: 122 |publisher=[[Springer Publishing|Springer]] |pages=7–8 |isbn=9783642007378}}</ref><ref>{{cite book |author-last=Penprase |author-first=Bryan E. |year=2017 |url=https://books.google.com/books?id=pQHNDgAAQBAJ |title=The Power of Stars |edition=2nd |publisher=[[Springer Science+Business Media|Springer]] |page=182 |isbn=9783319525976}}</ref><ref>{{cite book |last=Johnson |first=W.J. |title=A Dictionary of Hinduism |publisher=Oxford University Press |year=2009 |isbn=978-0-19-861025-0 |page=165}}</ref><ref>{{cite web |last1=Fernandez |first1=Elizabeth |title=The Multiverse And Eastern Philosophy |url=https://www.forbes.com/sites/fernandezelizabeth/2020/01/12/the-multiverse-and-eastern-philosophy/ |website=Forbes |language=en}}</ref> The texts also speak of innumerable worlds or universes.<ref> * {{cite book |last1=Zimmer |first1=Heinrich Robert |title=Myths and Symbols in Indian Art and Civilization |date=2018 |publisher=Princeton University Press |isbn=978-0-691-21201-2 |url=https://books.google.com/books?id=cZDTDwAAQBAJ&q=%22innumerable%20worlds%22&pg=PT18 |language=en}} * {{cite book |last1=Penprase |first1=Bryan E. |title=The Power of Stars |date=2017 |publisher=Springer |isbn=978-3-319-52597-6 |page=137 |url=https://books.google.com/books?id=pQHNDgAAQBAJ&q=%22innumerable%20universes%22&pg=PA137 |language=en}} * {{cite book |last1=Campbell |first1=Joseph |title=Papers from the Eranos Yearbooks, Eranos 3: Man and Time |date=2015 |publisher=Princeton University Press |isbn=978-1-4008-7485-9 |page=176 |url=https://books.google.com/books?id=bwnWCgAAQBAJ&pg=PA176 |language=en}} * {{cite book |last1=Henderson |first1=Joseph Lewis |last2=Oakes |first2=Maud |title=The Wisdom of the Serpent: The Myths of Death, Rebirth, and Resurrection |date=1990 |publisher=Princeton University Press |isbn=978-0-691-02064-8 |page=86 |url=https://books.google.com/books?id=hXD0gIN2a5IC |language=en}}</ref> * '''2nd century CE'''&nbsp;– [[Ptolemy]] proposes an Earth-centered universe, with the [[Classical planet|Sun, Moon, and visible planets]] revolving around the Earth. He also calculates the positions, [[orbit]]s and positional equations of the [[Astronomical object|Heavenly bodies]] along with instruments to measure these quantities in his book ''The Almagest.'' His book also cataloged 1022 [[star]]s and other [[Astronomy|astronomical]] objects which remained the largest astronomical catalogue until the 17th century AD.<ref>{{Citation |last=jones |first=prudence|title=Ptolemy |date=2011-01-01 |url=https://www.oxfordreference.com/view/10.1093/acref/9780195382075.001.0001/acref-9780195382075-e-1700 |work=Dictionary of African Biography |publisher=Oxford University Press |language=en |doi=10.1093/acref/9780195382075.001.0001/acref-9780195382075-e-1700 |isbn=978-0-19-538207-5 |access-date=2022-11-09}}</ref><ref>{{Cite journal |last=Swerdlow |first=N. M. |date=February 2021 |title=The Almagest in the Manner of Euclid |url=http://journals.sagepub.com/doi/10.1177/0021828620977214 |journal=Journal for the History of Astronomy |language=en |volume=52 |issue=1 |pages=104–107 |doi=10.1177/0021828620977214 |issn=0021-8286}}</ref> * '''5th century'''&nbsp;(or earlier) – Buddhist texts speak of "hundreds of thousands of billions, countlessly, innumerably, boundlessly, incomparably, incalculably, unspeakably, inconceivably, immeasurably, inexplicably many worlds" to the east, and "infinite worlds in the ten directions".<ref>{{cite book |last1=Jackson |first1=Roger |last2=Makransky |first2=John |title=Buddhist Theology: Critical Reflections by Contemporary Buddhist Scholars |date=2013 |publisher=Routledge |isbn=978-1-136-83012-9 |page=118 |url=https://books.google.com/books?id=YdhcAgAAQBAJ&pg=PA118 |language=en}}</ref><ref>{{cite book |last1=Reat |first1=N. Ross |last2=Perry |first2=Edmund F. |title=A World Theology: The Central Spiritual Reality of Humankind |date=1991 |publisher=Cambridge University Press |isbn=978-0-521-33159-3 |page=112 |url=https://books.google.com/books?id=vD2TJNc7NE4C&pg=PA112 |language=en}}</ref> * '''5th century'''&nbsp;– Several Indian astronomers propose a rudimentary Sun-centered universe, including [[Aryabhata]]. He also writes a treatise on motion of planets, [[sun]] and [[moon]] and stars.Aryabhatta puts forward the theory of rotation of the earth in its own axis and explained [[day]] and night was caused by the diurnal rotation of the [[earth]]. He also provided empirical evidence for his notion from his astronomical experiments and observation.<ref>{{Cite journal |last=India |first=Digital Branding Learners |date=2019-01-01 |title=Aryabhatta and the great Indian Mathematicians |url=https://www.academia.edu/38561360/Aryabhatta_the_the_great_Indian_Mathematicians |journal=Learners India}}</ref> * '''5th century''' – The Jewish talmud gives an argument for [[Finite model theory|finite universe]] theory along with explanation. * '''6th century'''&nbsp;– [[John Philoponus]] proposes a universe that is finite in [[time]] and argues against the ancient Greek notion of an infinite universe * '''7th century'''&nbsp;– The [[Quran]] says in Chapter 21: Verse 30 – "Have those who disbelieved not considered that the heavens and the earth were a joined entity, and We separated them". * '''9th–12th centuries'''&nbsp;– [[Al-Kindi]] (Alkindus), [[Saadia Gaon]] (Saadia ben Joseph) and [[Al-Ghazali]] (Algazel) support a universe that has a finite past and develop two logical arguments for the notion. * '''12th century'''&nbsp;– [[Fakhr al-Din al-Razi]] discusses [[Islamic cosmology]], rejects Aristotle's idea of an Earth-centered universe, and, in the context of his commentary on the [[Quran]]ic verse, "All praise belongs to God, Lord of the Worlds," and proposes that the universe has more than "a thousand worlds beyond this world."<ref>{{cite journal|title=Fakhr Al-Din Al-Razi on Physics and the Nature of the Physical World: A Preliminary Survey |author=Adi Setia |journal=Islam & Science |volume=2 |date=2004 |url=http://findarticles.com/p/articles/mi_m0QYQ/is_2_2/ai_n9532826/ |archive-url=https://archive.today/20120710164222/http://findarticles.com/p/articles/mi_m0QYQ/is_2_2/ai_n9532826/ |url-status=dead |archive-date=2012-07-10 |access-date=2010-03-02 }}</ref> * '''14th century'''&nbsp;– Christian scholar [[Nicholas of Cusa]] and proposed that the Earth rotates on its axis in his book, ''On Learned Ignorance'' (1440).<ref>Misner, Thorne and Wheeler</ref> * '''14th century'''&nbsp;– Several European [[mathematician]]s and [[astronomer]]s develop the theory of Earth's rotation including [[Nicole Oresme]]. Nicole Oresme also give logical reasoning. empirical evidence and [[Mathematics|mathematical]] proofs for his notion.<ref>{{Citation |last=Kirschner |first=Stefan |title=Nicole Oresme |date=2021 |url=https://plato.stanford.edu/archives/fall2021/entries/nicole-oresme/ |work=The Stanford Encyclopedia of Philosophy |editor-last=Zalta |editor-first=Edward N. |edition=Fall 2021 |publisher=Metaphysics Research Lab, Stanford University |access-date=2022-11-09}}</ref><ref>{{Cite web |date=2022-09-28 |title=Episode 11: The Legacy of Ptolemy's Almagest |url=https://www.aip.org/initialconditions/episode-11-legacy-ptolemys-almagest |access-date=2022-11-09 |website=www.aip.org |language=en}}</ref> * '''15th–16th centuries'''&nbsp;– [[Nilakantha Somayaji]] and [[Tycho Brahe]] propose a universe in which the planets orbit the Sun and the Sun orbits the Earth, known as the [[Tychonic system]] * '''1543'''&nbsp;– [[Nicolaus Copernicus]] publishes his [[Copernican heliocentrism|heliocentric universe]] in his {{lang|la|[[De revolutionibus orbium coelestium]]}}.<ref>{{Cite web |title=Nicolaus Copernicus - University of Bologna |url=https://www.unibo.it/en/university/who-we-are/our-history/famous-people-and-students/nicolaus-copernicus |access-date=2022-11-09 |website=www.unibo.it |language=en}}</ref> * '''1576'''&nbsp;– [[Thomas Digges]] modifies the [[Copernican heliocentrism|Copernican system]] by removing its outer edge and replacing the edge with a [[star]]-filled unbounded space * '''1584'''&nbsp;– [[Giordano Bruno]] proposes a non-hierarchical cosmology, wherein the Copernican [[Solar System]] is not the center of the universe, but rather, a relatively insignificant [[star system]], amongst an infinite multitude of others * '''1610'''&nbsp;– [[Johannes Kepler]] uses the dark night sky to argue for a finite universe * '''1687'''&nbsp;– Sir Isaac Newton's [[Physical law|laws]] describe large-scale motion throughout the universe * '''1720'''&nbsp;– [[Edmund Halley]] puts forth an early form of [[Olbers' paradox]] * '''1729'''&nbsp;– [[James Bradley]] discovers the [[aberration of light]], due to the Earth's motion around the Sun. * '''1744'''&nbsp;– [[Jean-Philippe de Cheseaux]] puts forth an early form of Olbers' paradox * '''1755'''&nbsp;– [[Immanuel Kant]] asserts that the [[nebulae]] are really [[galaxy|galaxies]] separate from, independent of, and outside the [[Milky Way Galaxy]]; he calls them ''[[island universe]]s''. * '''1785'''&nbsp;– [[William Herschel]] proposes [[heliocentrism#William Herschel's heliocentrism|a heliocentric model of the universe]] that Earth's Sun is at or near the center of the universe, which at the time was assumed to only be the [[Milky Way Galaxy]].<ref name="Berendzen">{{cite journal |last1=Berendzen |first1=Richard |title=Geocentric to heliocentric to galactocentric to acentric: the continuing assault to the egocentric |journal=Vistas in Astronomy |date=1975 |volume=17 |issue=1 |pages=65–83 |doi=10.1016/0083-6656(75)90049-5 |bibcode=1975VA.....17...65B }}</ref> * '''1791'''&nbsp;– [[Erasmus Darwin]] pens the first description of a cyclical expanding and contracting universe in his poem ''[[The Botanic Garden|The Economy of Vegetation]]'' * '''1826'''&nbsp;– [[Heinrich Wilhelm Olbers]] puts forth [[Olbers' paradox]] * '''1837'''&nbsp;– Following over 100 years of unsuccessful attempts, [[Friedrich Bessel]], Thomas Henderson and Otto Struve measure the [[parallax]] of a few nearby stars; this is the first measurement of any distances outside the Solar System. * '''1848'''&nbsp;– [[Edgar Allan Poe]] offers first correct solution to Olbers' paradox in ''[[Eureka: A Prose Poem]]'', an essay that also suggests the expansion and collapse of the universe * '''1860s'''&nbsp;– [[William Huggins]] develops astronomical [[spectroscopy]]; he shows that the [[Orion nebula]] is mostly made of gas, while the Andromeda nebula (later called [[Andromeda Galaxy]]) is probably dominated by stars. ==1900–1949hi I like dick * '''1905'''&nbsp;– [[Albert Einstein]] publishes the [[Special relativity|Special Theory of Relativity]], positing that space and time are not separate continua * '''1912'''&nbsp;– [[Henrietta Leavitt]] discovers the period-luminosity law for [[Cepheid variable]] stars, which becomes a crucial step in measuring distances to other galaxies. * '''1915'''&nbsp;– Albert Einstein publishes the [[General Theory of Relativity]], showing that an energy density warps [[spacetime]] * '''1917'''&nbsp;– [[Willem de Sitter]] derives an isotropic static cosmology with a [[cosmological constant]], as well as an empty [[metric expansion of space|expanding cosmology]] with a cosmological constant, termed a [[de Sitter universe]] * '''1918'''&nbsp;– [[Harlow Shapley]]'s work on [[globular clusters]] showed that the [[heliocentrism]] model of cosmology was wrong, and [[galactocentrism]] replaced heliocentrism as the dominant model of cosmology.<ref name="Berendzen"/> * '''1920'''&nbsp;– The [[Shapley-Curtis Debate]], on the distances to spiral nebulae, takes place at the [[Smithsonian]] * '''1921'''&nbsp;– The [[United States National Research Council|National Research Council]] (NRC) published the official transcript of the [[Shapley-Curtis Debate]] * '''1922'''&nbsp;– [[Vesto Slipher]] summarizes his findings on the [[galaxy|spiral nebulae]]'s systematic [[redshift]]s * '''1922'''&nbsp;– [[Alexander Friedmann]] finds a solution to the [[Einstein field equation]]s which suggests a general expansion of space * '''1923'''&nbsp;– [[Edwin Hubble]] measures distances to a few nearby spiral nebulae (galaxies), the [[Andromeda Galaxy]] (M31), [[Triangulum Galaxy]] (M33), and [[NGC 6822]]. The distances place them far outside the Milky Way, and implies that fainter galaxies are much more distant, and the universe is composed of many thousands of galaxies. * '''1927'''&nbsp;– [[Georges Lemaître]] 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'''&nbsp;– [[Howard P. Robertson]] briefly mentions that Vesto Slipher's redshift measurements combined with brightness measurements of the same galaxies indicate a redshift-distance relation * '''1929'''&nbsp;– [[Edwin Hubble]] demonstrates the linear redshift-distance relation and thus shows the expansion of the universe * '''1933'''&nbsp;– [[Edward Arthur Milne|Edward Milne]] names and formalizes the [[cosmological principle]] * '''1933'''&nbsp;– [[Fritz Zwicky]] shows that the [[Coma cluster]] of galaxies contains large amounts of dark matter. This result agrees with modern measurements, but is generally ignored until the 1970s. * '''1934'''&nbsp;– [[Georges Lemaître]] interprets the cosmological constant as due to a [[vacuum energy]] with an unusual perfect fluid [[equation of state]] * '''1938'''&nbsp;– [[Paul Dirac]] suggests the [[Dirac large numbers hypothesis|large numbers hypothesis]], that the gravitational constant may be small because it is decreasing slowly with time * '''1948'''&nbsp;– [[Ralph Alpher]], [[Hans Bethe]] ([[Alpher-Bethe-Gamov paper|"in absentia"]]), and [[George Gamow]] examine element synthesis in a rapidly expanding and cooling universe, and suggest that the elements were produced by rapid [[neutron]] capture * '''1948'''&nbsp;– [[Hermann Bondi]], [[Thomas Gold]], and [[Fred Hoyle]] propose [[steady state theory|steady state]] cosmologies based on the perfect cosmological principle * '''1948'''&nbsp;– [[George Gamow]] predicts the existence of the [[cosmic microwave background radiation]] by considering the behavior of primordial radiation in an expanding universe ==1950–1999== * '''1950'''&nbsp;– [[Fred Hoyle]] 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'''&nbsp;– [[Robert Dicke]] argues that [[carbon]]-based [[life]] can only arise when the gravitational force is small, because this is when burning stars exist; first use of the weak [[anthropic principle]] * '''1963'''&nbsp;– [[Maarten Schmidt]] discovers the first [[quasar]]; these soon provide a probe of the universe back to substantial redshifts. * '''1965'''&nbsp;– [[Hannes Alfvén]] proposes the now-discounted concept of [[ambiplasma]] to explain [[baryon asymmetry]] and supports the idea of an infinite universe. * '''1965'''&nbsp;– [[Martin Rees]] and [[Dennis Sciama]] analyze [[quasar]] source count data and discover that the quasar density increases with redshift. * '''1965'''&nbsp;– [[Arno Penzias]] and [[Robert Woodrow Wilson|Robert Wilson]], astronomers at [[Bell Labs]] discover the 2.7 K ''microwave background radiation'', which earns them the 1978 [[Nobel Prize]] in Physics. [[Robert Dicke]], [[Jim Peebles|James Peebles]], Peter Roll and [[David Todd Wilkinson]] interpret it as a relic from the big bang. * '''1966'''&nbsp;– [[Stephen Hawking]] and [[George Francis Rayner Ellis|George Ellis]] show that any plausible general relativistic cosmology is [[gravitational singularity|singular]] * '''1966'''&nbsp;– [[Jim Peebles|James Peebles]] shows that the hot [[Big Bang]] predicts the correct helium abundance * '''1967'''&nbsp;– [[Andrei Sakharov]] presents the requirements for [[baryogenesis]], a [[baryon]]-[[antimatter|antibaryon]] [[asymmetry]] in the universe * '''1967'''&nbsp;– [[John Bahcall]], [[Wal Sargent]], and [[Maarten Schmidt]] measure the fine-structure splitting of [[spectral line]]s in 3C191 and thereby show that the [[fine-structure constant]] does not vary significantly with time * '''1967'''&nbsp;– [[Robert Wagner]], [[William Alfred Fowler|William Fowler]], and Fred Hoyle show that the hot Big Bang predicts the correct [[deuterium]] and [[lithium]] abundances * '''1968'''&nbsp;– [[Brandon Carter]] 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'''&nbsp;– [[Charles Misner]] formally presents the Big Bang [[horizon problem]] * '''1969'''&nbsp;– Robert Dicke formally presents the Big Bang flatness problem * '''1970'''&nbsp;– [[Vera Rubin]] and Kent Ford measure spiral galaxy rotation curves at large radii, showing evidence for substantial amounts of [[dark matter]]. * '''1973'''&nbsp;– [[Edward Tryon]] proposes that the universe may be a large scale [[quantum mechanics|quantum mechanical]] [[quantum fluctuation|vacuum fluctuation]] where positive mass-energy is balanced by negative [[gravitational energy|gravitational potential energy]] * '''1976'''&nbsp;– [[Alex Shlyakhter]] uses [[samarium]] ratios from the [[Oklo]] prehistoric [[natural nuclear fission reactor]] in [[Gabon]] to show that some laws of physics have remained unchanged for over two billion years * '''1977'''&nbsp;– [[Gary Steigman]], [[David Schramm (astrophysicist)|David Schramm]], and [[James Gunn (astronomer)|James Gunn]] examine the relation between the primordial helium abundance and number of neutrinos and claim that at most five [[lepton]] families can exist. * '''1980'''&nbsp;– [[Alan Guth]] and Alexei Starobinsky independently propose the [[cosmic inflation|inflationary]] Big Bang universe as a possible solution to the horizon and flatness problems. * '''1981'''&nbsp;– [[Viatcheslav Mukhanov]] and G. Chibisov propose that quantum fluctuations could lead to large scale structure in an [[cosmic inflation|inflationary]] universe. * '''1982'''&nbsp;– The first CfA galaxy redshift survey is completed. * '''1982'''&nbsp;– Several groups including [[Jim Peebles|James Peebles]], J. Richard Bond and George Blumenthal propose that the universe is dominated by cold [[dark matter]]. * '''1983–1987''' &nbsp;– The first large computer simulations of cosmic structure formation are run by Davis, Efstathiou, Frenk and White. The results show that cold dark matter produces a reasonable match to observations, but hot dark matter does not. * '''1988'''&nbsp;– The [[CfA2 Great Wall]] is discovered in the CfA2 redshift survey. * '''1988'''&nbsp;– Measurements of galaxy large-scale flows provide evidence for the [[Great Attractor]]. * '''1990'''&nbsp;– Preliminary results from [[NASA]]'s [[Cosmic Background Explorer|COBE]] mission confirm the [[cosmic microwave background radiation]] has a [[blackbody]] spectrum 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. * '''1992'''&nbsp;– Further [[Cosmic Background Explorer|COBE]] measurements discover the very small [[anisotropy]] of the [[cosmic microwave background]], providing a "baby picture" of the seeds of large-scale structure when the universe was around 1/1100th of its present size and 380,000 years old. * '''1996'''&nbsp;– The first [[Hubble Deep Field]] is released, providing a clear view of very distant galaxies when the universe was around one-third of its present age. * '''1998'''&nbsp;– Controversial evidence for the [[fine-structure constant]] varying over the lifetime of the universe is first published. * '''1998'''&nbsp;– The [[Supernova Cosmology Project]] and [[High-Z Supernova Search Team]] discover [[dark energy|cosmic acceleration]] based on distances to [[Type Ia supernova]]e, providing the first direct evidence for a non-zero [[cosmological constant]]. * '''1999'''&nbsp;– Measurements of the [[cosmic microwave background radiation]] with finer resolution than COBE, (most notably by the [[BOOMERanG experiment]] see Mauskopf et al., 1999, Melchiorri et al., 1999, de Bernardis et al. 2000) provide evidence for oscillations (the first acoustic peak) in the [[anisotropy]] angular spectrum, as expected in the standard model of cosmological structure formation. The angular position of this peak indicates that the geometry of the universe is close to flat. ==Since 2000== * '''2001'''&nbsp;– The [[2dF Galaxy Redshift Survey]] (2dF) by an Australian/British team gave strong evidence that the matter density is near 25% of critical density. Together with the CMB results for a flat universe, this provides independent evidence for a [[cosmological constant]] or similar [[dark energy]]. * '''2002'''&nbsp;– The [[Cosmic Background Imager]] (CBI) in [[Chile]] 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'''&nbsp;– NASA's [[Wilkinson Microwave Anisotropy Probe]] (WMAP) obtained full-sky detailed pictures of the cosmic microwave background radiation. The images can be interpreted to indicate that the universe is 13.7 billion years old (within one percent error), and are very consistent with the [[Lambda-CDM model]] and the density fluctuations predicted by [[cosmic inflation|inflation]]. * '''2003'''&nbsp;– The [[Sloan Great Wall]] is discovered. * '''2004'''&nbsp;– The Degree Angular Scale Interferometer (DASI) first obtained the E-mode polarization spectrum of the cosmic microwave background radiation. * '''2005'''&nbsp;– The [[Sloan Digital Sky Survey]] (SDSS) and [[2dF Galaxy Redshift Survey|2dF]] redshift surveys both detected the [[baryon acoustic oscillation]] feature in the galaxy distribution, a key prediction of cold [[dark matter]] models. * '''2006'''&nbsp;– Three-year [[WMAP]] results are released, confirming previous analysis, correcting several points, and including [[Cosmic microwave background radiation#Polarization|polarization]] data. * '''2009–2013'''&nbsp;– [[Planck (spacecraft)|Planck]], a space observatory operated by the [[European Space Agency]] (ESA), mapped the anisotropies of the [[cosmic microwave background radiation]], with increased sensitivity and small angular resolution. * '''2006–2011'''&nbsp;– Improved measurements from [[WMAP]], new supernova surveys ESSENCE and SNLS, and baryon acoustic oscillations from [[Sloan Digital Sky Survey|SDSS]] and [[Astronomical survey#List of sky surveys|WiggleZ]], continue to be consistent with the standard [[Lambda-CDM model]]. * '''2014'''&nbsp;– Astrophysicists of the [[BICEP and Keck Array|BICEP2]] collaboration announce the detection of inflationary [[gravitational waves]] in the [[B-modes|B-mode]] [[power spectrum]], which if confirmed, would provide clear experimental evidence for the [[Inflation (cosmology)|theory of inflation]].<ref name="BICEP2-2014">{{cite web |author=Staff |title=BICEP2 2014 Results Release |url=http://bicepkeck.org |date=March 17, 2014 |work=[[National Science Foundation]] |access-date=March 18, 2014 }}</ref><ref name="NASA-20140317">{{cite web |last=Clavin |first=Whitney |title=NASA Technology Views Birth of the Universe |url=http://www.jpl.nasa.gov/news/news.php?release=2014-082 |date=March 17, 2014 |work=[[NASA]] |access-date=March 17, 2014 }}</ref><ref name="NYT-20140317">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Space Ripples Reveal Big Bang's Smoking Gun |url=https://www.nytimes.com/2014/03/18/science/space/detection-of-waves-in-space-buttresses-landmark-theory-of-big-bang.html |date=March 17, 2014 |work=[[The New York Times]] |access-date=March 17, 2014 }}</ref><ref name="NYT-20140324">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Ripples From the Big Bang |url=https://www.nytimes.com/2014/03/25/science/space/ripples-from-the-big-bang.html |date=March 24, 2014 |work=[[New York Times]] |access-date=March 24, 2014 }}</ref><ref name="PRL-20140619"/><ref>{{Cite web | url=http://www.math.columbia.edu/~woit/wordpress/?p=6865 | title=BICEP2 News &#124; Not Even Wrong}}</ref> However, in June lowered confidence in confirming the [[cosmic inflation]] findings was reported.<ref name="PRL-20140619">{{cite journal |author=Ade, P.A.R. |author2=BICEP2 Collaboration |title=Detection of B-Mode Polarization at Degree Angular Scales by BICEP2 |date=June 19, 2014 |journal=[[Physical Review Letters]] |volume=112 |issue=24 |page=241101 |doi=10.1103/PhysRevLett.112.241101 |arxiv = 1403.3985 |bibcode = 2014PhRvL.112x1101B |pmid=24996078|s2cid=22780831 }}</ref><ref name="NYT-20140619">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Astronomers Hedge on Big Bang Detection Claim |url=https://www.nytimes.com/2014/06/20/science/space/scientists-debate-gravity-wave-detection-claim.html |date=June 19, 2014 |work=[[New York Times]] |access-date=June 20, 2014 }}</ref><ref name="BBC-20140619">{{cite news |last=Amos |first=Jonathan |title=Cosmic inflation: Confidence lowered for Big Bang signal |url=https://www.bbc.com/news/science-environment-27935479 |date=June 19, 2014 |work=[[BBC News]] |access-date=June 20, 2014 }}</ref> * '''2016'''&nbsp;– [[LIGO Scientific Collaboration]] and [[Virgo interferometer|Virgo Collaboration]] announce that gravitational waves were [[First observation of gravitational waves|directly detected]] by two [[LIGO]] detectors. The [[waveform]] matched the prediction of [[General relativity]] for a gravitational wave emanating from the inward spiral and merger of a pair of [[black hole]]s of around 36 and 29 [[solar mass]]es and the subsequent "ringdown" of the single resulting black hole.<ref>{{Cite journal|title = Observation of Gravitational Waves from a Binary Black Hole Merger|journal = [[Physical Review Letters]]|date = 2016-02-11|issn = 0031-9007|volume = 116|issue = 6|doi = 10.1103/PhysRevLett.116.061102|language = en|first1 = B. P.|last1 = Abbott|first2 = R.|last2 = Abbott|first3 = T. D.|last3 = Abbott|first4 = M. R.|last4 = Abernathy|first5 = F.|last5 = Acernese|first6 = K.|last6 = Ackley|first7 = C.|last7 = Adams|first8 = T.|last8 = Adams|first9 = P.|last9 = Addesso|arxiv = 1602.03837 |bibcode = 2016PhRvL.116f1102A|pmid=26918975|pages=061102|s2cid = 124959784}}</ref><ref name="Nature_11Feb16">{{cite journal |title=Einstein's gravitational waves found at last |journal=Nature News |url=http://www.nature.com/news/einstein-s-gravitational-waves-found-at-last-1.19361 |date=11 February 2016 |last1=Castelvecchi |first1=Davide |last2=Witze |first2=Alexandra |doi=10.1038/nature.2016.19361 |s2cid=182916902 |access-date=11 February 2016}}</ref><ref name ="renn">{{cite web |last1=Blum |first1=Alexander |last2=Lalli |first2=Roberto |last3=Renn |first3=Jürgen |author-link3=Jürgen Renn |title=The long road towards evidence |url=http://www.mpg.de/9966773/background |work=[[Max Planck Society]] |date=12 February 2016 |access-date=15 February 2016}}</ref> The [[GW151226|second detection]] verified that GW150914 is not a fluke, thus opens entire new branch in astrophysics, [[gravitational-wave astronomy]].<ref name="PRL-20160615" >{{Cite journal| collaboration=LIGO Scientific Collaboration and Virgo Collaboration| last=Abbott| first=B. P.| date=15 June 2016| title=GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence| journal=Physical Review Letters| volume= 116| issue= 24| pages=241103|doi=10.1103/PhysRevLett.116.241103| pmid=27367379|arxiv = 1606.04855 |bibcode = 2016PhRvL.116x1103A | s2cid=118651851}}</ref><ref>{{Cite web| url=http://physicsworld.com/cws/article/news/2016/jun/15/ligo-detects-second-black-hole-merger| title=LIGO detects second black-hole merger |date=15 June 2016| first=Tushna| last=Commissariat| website=[[Physics World]]| publisher= [[Institute of Physics]]| access-date=15 June 2016}}</ref> * '''2019'''&nbsp;– <!--- More informative details could be added here. --->[[Event Horizon Telescope|The Event Horizon Telescope]] Collaboration publishes the image of the black hole at the center of the [[Messier 87|M87 Galaxy]].<ref>{{Cite web|url=https://eventhorizontelescope.org/blog/first-ever-image-black-hole-published-event-horizon-telescope-collaboration|title=First-ever Image of a Black Hole Published by the Event Horizon Telescope Collaboration|website=eventhorizontelescope.org|language=en|access-date=2020-03-30}}</ref> This is the first time [[astronomer]]s have ever captured an image of a [[black hole]], which once again proves the existence of black holes and thus helps verify [[Albert Einstein|Einstein]]'s [[General relativity|general theory of relativity]].<ref>{{Cite web|url=https://www.sciencenews.org/article/black-hole-first-picture-event-horizon-telescope|title=The first picture of a black hole opens a new era of astrophysics|date=2019-04-10|website=Science News|language=en-US|access-date=2020-03-30}}</ref> This was done by utilising [[very-long-baseline interferometry]].<ref>{{Cite web|url=https://skyandtelescope.org/astronomy-blogs/black-hole-files/how-does-very-long-baseline-interferometry-work/|title=How Does the Event Horizon Telescope Work?|date=2019-04-15|website=Sky & Telescope|language=en-US|access-date=2020-03-30}}</ref> * '''2020'''&nbsp;— Physicist [[Lucas Lombriser]] of the [[University of Geneva]] presents a possible way of reconciling the two significantly different determinations of the [[Hubble constant]] by proposing the notion of a surrounding [[Hubble bubble (astronomy)|vast "bubble"]], 250 million light years in diameter, that is half the density of the rest of the universe.<ref name="PHYS-20200310">{{cite news |author=University of Geneva |title=Solved: The mystery of the expansion of the universe |url=https://phys.org/news/2020-03-mystery-expansion-universe.html |date=10 March 2020 |work=[[Phys.org]] |access-date=10 March 2020 |author-link=University of Geneva }}</ref><ref name="PLB-20200410">{{cite journal |last=Lombriser |first=Lucas |title=Consistency of the local Hubble constant with the cosmic microwave background |date=10 April 2020 |journal=[[Physics Letters B]] |volume=803 |pages=135303 |doi=10.1016/j.physletb.2020.135303 |arxiv=1906.12347 |bibcode=2020PhLB..80335303L |s2cid=195750638 }}</ref> * '''2020'''&nbsp;— Scientists publish a study which suggests that the Universe is no longer [[Expansion of the Universe|expanding]] at the same rate in all directions and that therefore the widely accepted [[Isotropy#Cosmology|isotropy hypothesis]] might be wrong. While previous studies already suggested this, the study is the first to examine [[galaxy cluster]]s in X-rays and, according to Norbert Schartel, has a much greater significance. The study found a consistent and strong directional behavior of [[Hubble's law#Measured values of the Hubble constant|deviations – which have earlier been described to indicate a "crisis of cosmology" by others – of the normalization parameter A, or the Hubble constant H0]]. Beyond the potential [[cosmological]] implications, it shows that studies which assume perfect isotropy in the properties of galaxy clusters and their scaling relations can produce strongly biased results.<ref>{{cite web |title=Rethinking cosmology: Universe expansion may not be uniform (Update) |url=https://phys.org/news/2020-04-basic-assumption-universe.html |website=phys.org |access-date=15 May 2020 |language=en}}</ref><ref>{{cite news |title=Nasa study challenges one of our most basic ideas about the universe |url=https://www.independent.co.uk/life-style/gadgets-and-tech/news/universe-expanding-direction-nasa-esa-cosmology-isotropic-a9455641.html |archive-url=https://ghostarchive.org/archive/20220507/https://www.independent.co.uk/life-style/gadgets-and-tech/news/universe-expanding-direction-nasa-esa-cosmology-isotropic-a9455641.html |archive-date=2022-05-07 |url-access=subscription |url-status=live |access-date=23 May 2020 |work=The Independent |date=8 April 2020 |language=en}}</ref><ref>{{cite news |title=Parts of the universe may be expanding faster than others |url=https://newatlas.com/physics/universe-expansion-not-uniform/ |access-date=23 May 2020 |work=New Atlas |date=9 April 2020}}</ref><ref>{{cite news |title=Doubts about basic assumption for the universe |url=https://www.eurekalert.org/pub_releases/2020-04/uob-dab040820.php |access-date=23 May 2020 |work=EurekAlert! |language=en}}</ref><ref>{{cite journal |last1=Migkas |first1=K. |last2=Schellenberger |first2=G. |last3=Reiprich |first3=T. H. |last4=Pacaud |first4=F. |last5=Ramos-Ceja |first5=M. E. |last6=Lovisari |first6=L. |title=Probing cosmic isotropy with a new X-ray galaxy cluster sample through the LX–T scaling relation |journal=Astronomy & Astrophysics |date=8 April 2020 |volume=636 |pages=A15 |doi=10.1051/0004-6361/201936602 |arxiv=2004.03305 |bibcode=2020A&A...636A..15M |s2cid=215238834 |url=https://www.aanda.org/articles/aa/abs/2020/04/aa36602-19/aa36602-19.html |access-date=15 May 2020 |language=en |issn=0004-6361}}</ref> * '''2020'''&nbsp;— Scientists report verifying measurements 2011–2014 via [[ULAS J1120+0641]] of what seem to be [[fine-structure constant#Potential time-variation|a spatial variation in four measurements of the fine-structure constant]], a basic physical constant used to measure [[electromagnetism]] between charged particles, which indicates that there might be directionality with varying natural constants in the Universe which would have implications for [[Physical constant#Fine-tuned universe|theories on the emergence of habitability of the Universe]] and be at odds with the widely accepted theory of constant [[natural law]]s and the standard model of [[cosmology]] which is based on an [[Isotropy|isotropic]] Universe.<ref>{{cite news |title=The laws of physics may break down at the edge of the universe |url=https://futurism.com/the-byte/laws-physics-break-down-edge-universe |access-date=17 May 2020 |work=Futurism |language=en}}</ref><ref>{{cite news |title=New findings suggest laws of nature 'downright weird,' not as constant as previously thought |url=https://phys.org/news/2020-04-laws-nature-downright-weird-constant.html |access-date=17 May 2020 |work=phys.org |language=en}}</ref><ref name="SA-20200428">{{cite news |last=Field |first=David |title=New Tests Suggest a Fundamental Constant of Physics Isn't The Same Across The Universe |url=https://www.sciencealert.com/new-tests-suggest-the-fundamental-forces-of-nature-aren-t-constant-across-the-universe |date=28 April 2020 |work=ScienceAlert.com |access-date=29 April 2020 }}</ref><ref>{{cite journal |last1=Wilczynska |first1=Michael R. |last2=Webb |first2=John K. |last3=Bainbridge |first3=Matthew |last4=Barrow |first4=John D. |last5=Bosman |first5=Sarah E. I. |last6=Carswell |first6=Robert F. |last7=Dąbrowski |first7=Mariusz P. |last8=Dumont |first8=Vincent |last9=Lee |first9=Chung-Chi |last10=Leite |first10=Ana Catarina |last11=Leszczyńska |first11=Katarzyna |last12=Liske |first12=Jochen |last13=Marosek |first13=Konrad |last14=Martins |first14=Carlos J. A. P. |last15=Milaković |first15=Dinko |last16=Molaro |first16=Paolo |last17=Pasquini |first17=Luca |title=Four direct measurements of the fine-structure constant 13 billion years ago |journal=Science Advances |date=1 April 2020 |volume=6 |issue=17 |pages=eaay9672 |doi=10.1126/sciadv.aay9672 |pmc=7182409 |pmid=32426462 |arxiv=2003.07627 |bibcode=2020SciA....6.9672W |doi-access=free }}</ref> ==See also== {{Portal|Space}} ===Physical cosmology=== * [[Chronology of the universe]] ** [[Graphical timeline of the Big Bang]] ** [[Graphical timeline from Big Bang to Heat Death]] ** [[Timeline of cosmic microwave background astronomy]] * [[List of cosmologists]] * [[Interpretations of quantum mechanics]] * [[Non-standard cosmology]] * [[Timeline of knowledge about galaxies, clusters of galaxies, and large-scale structure]] ===Belief systems=== * [[Buddhist cosmology]] * [[Jain cosmology]] * [[Jainism and non-creationism]] * [[Hindu cosmology]] * [[Maya mythology]] ===Others=== * [[Cosmology@Home]] ==References== {{Reflist}} ==Bibliography== * Bunch, Bryan, and Alexander Hellemans, ''The History of Science and Technology: A Browser's Guide to the Great Discoveries, Inventions, and the People Who Made Them from the Dawn of Time to Today''. {{ISBN|0-618-22123-9}} * P. de Bernardis et al., astro-ph/0004404, Nature 404 (2000) 955–959. * {{cite book| last= Horowitz| first = Wayne| title = Mesopotamian cosmic geography | date = 1998| publisher = [[Eisenbrauns]]| url = https://books.google.com/books?id=P8fl8BXpR0MC| isbn = 978-0-931464-99-7}} * P. Mauskopf et al., astro-ph/9911444, Astrophys. J. 536 (2000) L59–L62. * A. Melchiorri et al., astro-ph/9911445, Astrophys. J. 536 (2000) L63–L66. * A. Readhead et al., Polarization observations with the Cosmic Background Imager, Science 306 (2004), 836–844. {{History of physics}} {{DEFAULTSORT:Cosmology}} [[Category:Astronomy timelines]] [[Category:Physical cosmology]] [[Category:Lists of inventions or discoveries]] [[Category:Physics timelines]]'