Editing Universe (section)

{{Short description|Everything in space and time}}
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{{Infobox
| title            = Universe
| image            = [[File:Hubble ultra deep field.jpg|300px]]
| caption          = The [[Hubble Ultra-Deep Field]] image shows some of the most remote [[Galaxy|galaxies]] visible to present technology (diagonal is ~1/10 apparent [[Moon]] diameter)<ref name="spacetelescope.org">{{cite web |url=http://spacetelescope.org/images/heic0406a/ |title=Hubble sees galaxies galore |work=spacetelescope.org |access-date=April 30, 2017 |archive-date=May 4, 2017 |archive-url=https://web.archive.org/web/20170504043058/http://www.spacetelescope.org/images/heic0406a/ |url-status=live}}</ref>
| label1           = [[Age of the universe|Age]] (within [[Lambda-CDM model|ΛCDM model]])
| data1            = 13.787 ± 0.020 billion years<ref name="Planck 2015" />
| label2           = Diameter
| data2            = Unknown<ref name="Brian Greene 2011" /><br>[[Observable universe]]: {{val|8.8|e=26|u=m}} {{nowrap|(28.5 G[[parsec|pc]] or 93 G[[light-year|ly]])}}<ref>{{cite book |first1=Itzhak |last1=Bars |first2=John |last2=Terning |title=Extra Dimensions in Space and Time |url=https://books.google.com/books?id=fFSMatekilIC&pg=PA27 |access-date=May 1, 2011 |date=2009 |publisher=Springer |isbn=978-0-387-77637-8 |pages=27–}}</ref>
| label3           = Mass (ordinary matter)
| data3            = At least {{val|e=53|u=kg}}<ref name="Paul Davies 2006 43">{{cite book |first=Paul |last=Davies |date=2006 |title=The Goldilocks Enigma |pages=43ff |publisher=First Mariner Books |isbn=978-0-618-59226-5 |url=https://archive.org/details/cosmicjackpotwhy0000davi |url-access=registration}}</ref>
| label4           = Average density (with [[energy]])
| data4            = {{val|9.9|e=-27|u=kg/m3}}<ref name="wmap_universe_made_of">{{cite web |author=NASA/WMAP Science Team |date=January 24, 2014 |title=Universe 101: What is the Universe Made Of? |url=http://map.gsfc.nasa.gov/universe/uni_matter.html |publisher=NASA |access-date=February 17, 2015 |archive-date=March 10, 2008 |archive-url=https://web.archive.org/web/20080310235855/http://map.gsfc.nasa.gov/universe/uni_matter.html |url-status=live}}</ref>
| label5           = Average temperature (cosmic microwave background)
| data5            = {{val|2.72548|ul=K}}<br>({{val|-270.4|ul=°C}}, {{val|-454.8|ul=°F}})<ref name=Fixsen>{{Cite journal |last1=Fixsen |first1=D.J. |date=2009 |title=The Temperature of the Cosmic Microwave Background |journal=[[The Astrophysical Journal]] |volume=707 |issue=2 |pages=916–920 |arxiv=0911.1955 |bibcode=2009ApJ...707..916F |doi=10.1088/0004-637X/707/2/916 |s2cid=119217397 |issn=0004-637X}}</ref>
| label6           = Main contents
| data6            = [[Baryon#Baryonic matter|Ordinary (baryonic)]] [[matter]] (4.9%)<br />[[Dark matter]] (26.8%)<br />[[Dark energy]] (68.3%)<ref name="planck2013parameters" />
| label7           = Shape
| data7            = [[Shape of the universe|Flat]] with 0.4% error margin<ref>{{cite web |author=NASA/WMAP Science Team |date=January 24, 2014 |url=http://map.gsfc.nasa.gov/universe/uni_shape.html |title=Universe 101: Will the Universe expand forever? |publisher=NASA |access-date=April 16, 2015 |archive-date=March 9, 2008 |archive-url=https://web.archive.org/web/20080309164248/http://map.gsfc.nasa.gov/universe/uni_shape.html |url-status=live}}</ref>
}}

The '''universe''' is all of [[space]] and [[time]]{{efn|name=spacetime|According to [[modern physics]], particularly the [[theory of relativity]], space and time are intrinsically linked as [[spacetime]].}} and their contents.<ref name="Zeilik1998">{{cite book |title=Introductory Astronomy & Astrophysics |last1=Zeilik |first1=Michael |last2=Gregory |first2=Stephen A. |year=1998 |edition=4th |publisher=Saunders College |quote=The totality of all space and time; all that is, has been, and will be. |isbn=978-0-03-006228-5}}</ref> It comprises all of [[existence]], any [[fundamental interaction]], [[physical process]] and [[physical constant]], and therefore all forms of [[matter]] and [[energy]], and the structures they form, from [[sub-atomic particles]] to entire [[Galaxy filament|galactic filaments]]. Since the early 20th century, the field of [[cosmology]] establishes that [[space and time]] emerged together at the [[Big Bang]] {{val|13.787|0.020|u=billion years}} ago<ref>{{Cite journal |last1=Planck Collaboration |last2=Aghanim |first2=N. |author2-link=Nabila Aghanim |last3=Akrami |first3=Y. |last4=Ashdown |first4=M. |last5=Aumont |first5=J. |last6=Baccigalupi |first6=C. |last7=Ballardini |first7=M. |last8=Banday |first8=A. J. |last9=Barreiro |first9=R. B.|last10=Bartolo|first10=N. |last11=Basak |first11=S. |date=September 2020 |title=Planck 2018 results: VI. Cosmological parameters |journal=Astronomy & Astrophysics |volume=641 |pages=A6 |doi=10.1051/0004-6361/201833910 |arxiv=1807.06209 |bibcode=2020A&A...641A...6P |s2cid=119335614 |issn=0004-6361}}</ref> and that the [[Expansion of the universe|universe has been expanding]] since then. The [[observable universe|portion of the universe that can be seen by humans]] is approximately 93 billion [[light-year]]s in diameter at present, but the total size of the universe is not known.<ref name="Brian Greene 2011">{{cite book |first=Brian |last=Greene |author-link=Brian Greene |title=The Hidden Reality |publisher=[[Alfred A. Knopf]] |year=2011 |title-link=The Hidden Reality}}</ref>

Some of the earliest [[Timeline of cosmological theories|cosmological models]] of the universe were developed by [[ancient Greek philosophy|ancient Greek]] and [[Indian philosophy|Indian philosophers]] and were [[geocentric model|geocentric]], placing Earth at the center.<ref>{{cite book |title=From China to Paris: 2000 Years Transmission of Mathematical Ideas |first=Yvonne |last=Dold-Samplonius |author-link=Yvonne Dold-Samplonius |year=2002 |publisher=Franz Steiner Verlag}}</ref><ref name="Routledge">{{cite book |title=Medieval Science Technology and Medicine: An Encyclopedia |first1=Thomas F. |last1=Glick |first2=Steven |last2=Livesey |first3=Faith |last3=Wallis |publisher=Routledge |year=2005 |isbn=978-0-415-96930-7}}</ref> Over the centuries, more precise astronomical observations led [[Nicolaus Copernicus]] to develop the [[heliocentrism|heliocentric model]] with the [[Sun]] at the center of the [[Solar System]]. In developing the [[Newton's law of universal gravitation|law of universal gravitation]], [[Isaac Newton]] built upon Copernicus's work as well as [[Johannes Kepler]]'s [[Kepler's laws of planetary motion|laws of planetary motion]] and observations by [[Tycho Brahe]].

Further observational improvements led to the realization that the Sun is one of a few hundred billion stars in the [[Milky Way]], which is one of a few hundred billion galaxies in the observable universe. Many of the stars in a galaxy [[exoplanet|have planets]]. [[End of Greatness|At the largest scale]], galaxies are distributed uniformly and the same in all directions, meaning that the universe has neither an edge nor a center. At smaller scales, galaxies are distributed in [[galaxy cluster|clusters]] and [[supercluster]]s which form immense [[galaxy filament|filaments]] and [[void (astronomy)|voids]] in space, creating a vast foam-like structure.<ref>{{Cite book |url=https://books.google.com/books?id=RLwangEACAAJ |title=An Introduction to Modern Astrophysics |last1=Carroll |first1=Bradley W. |last2=Ostlie |first2=Dale A. |year=2013 |publisher=Pearson |isbn=978-1-292-02293-2 |edition=International |pages=1173–1174 |access-date=May 16, 2018}}</ref> Discoveries in the early 20th century have suggested that the universe had a beginning and has been expanding since then.<ref name="Hawking">{{cite book |last=Hawking |first=Stephen |url=https://archive.org/details/briefhistoryofti00step_1 |title=A Brief History of Time |year=1988 |publisher=Bantam |isbn=978-0-553-05340-1 |page=[https://archive.org/details/briefhistoryofti00step_1/page/43 43] |author-link=Stephen Hawking |url-access=registration}}</ref>

According to the Big Bang theory, the energy and matter initially present have become less dense as the universe expanded. After an initial accelerated expansion called the [[cosmic inflation|inflation]] at around 10<sup>−32</sup> seconds, and the separation of the four known [[fundamental interaction|fundamental forces]], the universe gradually cooled and continued to expand, allowing the first [[subatomic particle]]s and simple [[atom]]s to form. Giant clouds of [[hydrogen]] and [[helium]] were gradually drawn to the places where matter was most [[density|dense]], forming the first galaxies, stars, and everything else seen today.

From studying the effects of [[gravity]] on both matter and light, it has been discovered that the universe contains much more [[matter]] than is accounted for by visible objects; stars, galaxies, nebulas and interstellar gas. This unseen matter is known as [[dark matter]].<ref>{{cite web |last1=Redd |first1=Nola |title=What is Dark Matter? |url=https://www.space.com/20930-dark-matter.html |website=Space.com |access-date=February 1, 2018 |archive-date=February 1, 2018 |archive-url=https://web.archive.org/web/20180201075430/https://www.space.com/20930-dark-matter.html |url-status=live}}</ref> In the widely accepted [[Lambda-CDM model|ΛCDM]] cosmological model, dark matter accounts for about {{val|25.8|1.1|u=%}} of the mass and energy in the universe while about {{val|69.2|1.2|u=%}} is [[dark energy]], a mysterious form of energy responsible for the [[accelerated expansion|acceleration]] of the [[expansion of the universe]].<ref name="planck_2015">{{Cite web |url=https://www.aanda.org/articles/aa/full_html/2016/10/aa27101-15/T9.html |title=Planck 2015 results, table 9 |access-date=May 16, 2018 |archive-date=July 27, 2018 |archive-url=https://web.archive.org/web/20180727024529/https://www.aanda.org/articles/aa/full_html/2016/10/aa27101-15/T9.html |url-status=live}}</ref> Ordinary ('[[Baryon#Baryonic matter|baryonic]]') matter therefore composes only {{val|4.84|0.1|u=%}} of the universe.<ref name="planck_2015" /> Stars, planets, and visible gas clouds only form about 6% of this ordinary matter.<ref>{{Cite journal |last1=Persic |first1=Massimo |last2=Salucci |first2=Paolo |date=September 1, 1992 |title=The baryon content of the Universe |journal=Monthly Notices of the Royal Astronomical Society |volume=258 |issue=1 |pages=14P–18P |doi=10.1093/mnras/258.1.14P |doi-access=free |issn=0035-8711 |arxiv=astro-ph/0502178 |bibcode=1992MNRAS.258P..14P |s2cid=17945298}}</ref>

There are many competing hypotheses about the [[ultimate fate of the universe]] and about what, if anything, preceded the Big Bang, while other physicists and philosophers refuse to speculate, doubting that information about prior states will ever be accessible. Some physicists have suggested various [[multiverse]] hypotheses, in which the universe might be one among many.<ref name="Brian Greene 2011" /><ref name="EllisKS032" /><ref>{{Cite news |date=August 3, 2011 |title='Multiverse' theory suggested by microwave background |work=BBC News |url=https://www.bbc.com/news/science-environment-14372387 |access-date=February 14, 2023 |archive-date=February 14, 2023 |archive-url=https://web.archive.org/web/20230214233557/https://www.bbc.com/news/science-environment-14372387 |url-status=live}}</ref>

{{cosmology}}