Editing Nebular hypothesis (section)

== History ==
{{Main|History of Solar System formation and evolution hypotheses}}
There is evidence that [[Emanuel Swedenborg]] first proposed parts of the nebular theory in 1734.<ref name=Swedenborg1734>{{cite book |last= Swedenborg |first= Emanuel |date= 1734|title= (Principia) Latin: Opera Philosophica et Mineralia (English: Philosophical and Mineralogical Works)|volume= I}}</ref><ref name="Swenborg">[http://www.newchurchhistory.org/articles/glb2007/baker.pdf Baker, Gregory L. "Emanuel Swenborg – an 18th century cosomologist".] ''The Physics Teacher''. October 1983, pp. 441–446.</ref> [[Immanuel Kant]], familiar with Swedenborg's work, developed the theory further in 1755, publishing his own ''[[Universal Natural History and Theory of the Heavens]]'', wherein he argued that gaseous clouds ([[nebulae]]) slowly rotate, gradually collapse and flatten due to [[gravity]], eventually forming [[star]]s and [[planet]]s.<ref name=Woolfson1993>{{cite journal|last= Woolfson|first= M.M.|title= Solar System&nbsp;– its origin and evolution|journal= Q. J. R. Astron. Soc.|volume= 34| pages= 1–20|date= 1993|bibcode= 1993QJRAS..34....1W}} For details of Kant's position, see Stephen Palmquist, "Kant's Cosmogony Re-Evaluated", ''Studies in History and Philosophy of Science'' 18:3 (September 1987), pp.255–269.</ref>

[[Pierre-Simon Laplace]] independently developed and proposed a similar model in 1796<ref name=Woolfson1993 /> in his ''Exposition du systeme du monde''. He envisioned that the Sun originally had an extended hot atmosphere throughout the volume of the Solar System. His theory featured a contracting and cooling protosolar cloud—the protosolar nebula. As this cooled and contracted, it flattened and spun more rapidly, throwing off (or shedding) a series of gaseous rings of material; and according to him, the planets condensed from this material. His model was similar to Kant's, except more detailed and on a smaller scale.<ref name=Woolfson1993 /> While the Laplacian nebular model dominated in the 19th century, it encountered a number of difficulties. The main problem involved [[angular momentum]] distribution between the Sun and planets. The planets have 99% of the angular momentum, and this fact could not be explained by the nebular model.<ref name=Woolfson1993 /> As a result, astronomers largely abandoned this theory of planet formation at the beginning of the 20th century.

According to some, a major critique came during the 19th century from [[James Clerk Maxwell]] (1831–1879), who in some sources is claimed to have maintained that ''different rotation between the inner and outer parts of a ring'' could not allow condensation of material.<ref>George H. A. Cole (2013). Planetary Science: The Science of Planets around Stars, Second Edition, Michael M. Woolfson, p. 190</ref> However, both the critique and the attribution to Maxwell have been deemed to be incorrect upon further investigation, with the original error being made by [[George Gamow]] in some popular publications and propagated continually ever since.<ref name=CharlesPetzold>{{cite web |first = Charles |last = Petzold |title = Maxwell, Molecules, and Evolution | date = February 2005 |url = https://www.charlespetzold.com/etc/MaxwellMoleculesAndEvolution.html |access-date = 2023-01-03}}</ref> Astronomer [[Sir David Brewster]] also rejected Laplace, writing in 1876 that "those who believe in the Nebular Theory consider it as certain that our Earth derived its solid matter and its atmosphere from a ring thrown from the Solar atmosphere, which afterwards contracted into a solid terraqueous sphere, from which the Moon was thrown off by the same process". He argued that under such view, "the Moon must necessarily have carried off water and air from the watery and aerial parts of the Earth and must have an atmosphere".<ref>Brester, David (1876), "More Worlds Than One: The Creed of the Philosopher and the Hope of the Christian", Chatto and Windus, Piccadilly, p. 153</ref> Brewster claimed that [[Sir Isaac Newton]]'s religious beliefs had previously considered nebular ideas as tending to atheism, and quoted him as saying that "the growth of new systems out of old ones, without the mediation of a Divine power, seemed to him apparently absurd".<ref>As quoted by David Brewster, "More worlds than one : the creed of the philosopher and the hope of the Christian", Fixed stars and binary systems. p. 233</ref>

The perceived deficiencies of the Laplacian model stimulated scientists to find a replacement for it. During the 20th century many theories addressed the issue, including the ''planetesimal theory'' of [[Thomas Chrowder Chamberlin|Thomas Chamberlin]] and [[Forest Ray Moulton|Forest Moulton]] (1901), the ''tidal model'' of [[James Jeans]] (1917), the ''accretion model'' of [[Otto Schmidt]] (1944), the ''protoplanet theory'' of [[William McCrea (astronomer)|William McCrea]] (1960) and finally the ''capture theory'' of [[Michael Woolfson]].<ref name=Woolfson1993 /> In 1978 [[Andrew Prentice]] resurrected the initial Laplacian ideas about planet formation and developed the ''modern Laplacian theory''.<ref name=Woolfson1993 /> None of these attempts proved completely successful, and many of the proposed theories were descriptive.

The birth of the modern widely accepted theory of planetary formation—the solar nebular disk model (SNDM)—can be traced to the Soviet astronomer [[Victor Safronov]].<ref name=NewScientist>{{cite web |last= Henbest |first= Nigel |url= https://www.newscientist.com/channel/solar-system/comets-asteroids/mg13117837.100|title= Birth of the planets: The Earth and its fellow planets may be survivors from a time when planets ricocheted around the Sun like ball bearings on a pinball table|publisher= New Scientist|date= 1991|access-date= 2008-04-18}}</ref> His 1969 book ''Evolution of the protoplanetary cloud and formation of the Earth and the planets'',<ref name=Safronov1972>{{cite book |first= Viktor Sergeevich|last= Safronov|title= Evolution of the Protoplanetary Cloud and Formation of the Earth and the Planets|isbn= 978-0-7065-1225-0|date= 1972| publisher=Israel Program for Scientific Translations}}</ref> which was translated to English in 1972, had a long-lasting effect on the way scientists think about the formation of the planets.<ref name=Safronov>{{cite journal |last= Wetherill |first= George W. |bibcode= 1989Metic..24..347W|title= Leonard Medal Citation for Victor Sergeevich Safronov|journal= Meteoritics|date= 1989|volume= 24|issue= 4 |page= 347|doi= 10.1111/j.1945-5100.1989.tb00700.x|doi-access= free}}</ref> In this book almost all major problems of the planetary formation process were formulated and some of them solved. Safronov's ideas were further developed in the works of [[George Wetherill]], who discovered ''[[Accretion (astrophysics)#Runaway accretion|runaway accretion]]''.<ref name=Woolfson1993 /> While originally applied only to the [[Solar System]], the SNDM was subsequently thought by theorists to be at work throughout the Universe; as of {{Extrasolar planet counts|asof}} astronomers have discovered {{Extrasolar planet counts|planet_count}} [[extrasolar planet]]s in our [[galaxy]].<ref name="Encyclopaedia">
{{cite encyclopedia 
|last1= Schneider |first1= Jean 
|date= 10 September 2011 
|title= Interactive Extra-solar Planets Catalog 
|url= https://exoplanet.eu/catalog/
|encyclopedia= [[Extrasolar Planets Encyclopaedia]] |access-date= 2011-09-10
}}
</ref>