Infinity Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! ==Physics== In [[physics]], approximations of [[real number]]s are used for [[Continuum (theory)|continuous]] measurements and [[natural number]]s are used for [[countable|discrete]] measurements (i.e., counting). Concepts of infinite things such as an infinite [[plane wave]] exist, but there are no experimental means to generate them.<ref>[http://www.doriclenses.com/administrer/upload/pdf/NOT_AXI_ENG_070212_doricl97_doricle_kvgwQP.pdf Doric Lenses] {{webarchive|url=https://web.archive.org/web/20130124011604/http://www.doriclenses.com/administrer/upload/pdf/NOT_AXI_ENG_070212_doricl97_doricle_kvgwQP.pdf |date=2013-01-24 }} β Application Note β Axicons β 2. Intensity Distribution. Retrieved 7 April 2014.</ref> ===Cosmology=== The first published proposal that the universe is infinite came from Thomas Digges in 1576.<ref>John Gribbin (2009), ''In Search of the Multiverse: Parallel Worlds, Hidden Dimensions, and the Ultimate Quest for the Frontiers of Reality'', {{isbn|978-0-470-61352-8}}. p. 88</ref> Eight years later, in 1584, the Italian philosopher and astronomer [[Giordano Bruno]] proposed an unbounded universe in ''On the Infinite Universe and Worlds'': "Innumerable suns exist; innumerable earths revolve around these suns in a manner similar to the way the seven planets revolve around our sun. Living beings inhabit these worlds."<ref>{{cite book |title=Alien Life Imagined: Communicating the Science and Culture of Astrobiology |edition=illustrated |first1=Mark |last1=Brake |publisher=Cambridge University Press |year=2013 |isbn=978-0-521-49129-7 |page=63 |url=https://books.google.com/books?id=sWGqzfL0snEC&pg=PA63}}</ref> [[Cosmology|Cosmologists]] have long sought to discover whether infinity exists in our physical [[universe]]: Are there an infinite number of stars? Does the universe have infinite volume? Does space "[[Shape of the universe|go on forever]]"? This is still an open question of [[physical cosmology|cosmology]]. The question of being infinite is logically separate from the question of having boundaries. The two-dimensional surface of the Earth, for example, is finite, yet has no edge. By travelling in a straight line with respect to the Earth's curvature, one will eventually return to the exact spot one started from. The universe, at least in principle, might have a similar [[topology]]. If so, one might eventually return to one's starting point after travelling in a straight line through the universe for long enough.<ref>{{cite book |title=In Quest of the Universe |edition=illustrated |first1=Theo |last1=Koupelis |first2=Karl F. |last2=Kuhn |publisher=Jones & Bartlett Learning |year=2007 |isbn=978-0-7637-4387-1 |page=553 |url=https://books.google.com/books?id=6rTttN4ZdyoC}} [https://books.google.com/books?id=6rTttN4ZdyoC&pg=PA553 Extract of p. 553]</ref> The curvature of the universe can be measured through [[multipole moments]] in the spectrum of the [[Cosmic microwave background radiation|cosmic background radiation]]. To date, analysis of the radiation patterns recorded by the [[WMAP]] spacecraft hints that the universe has a flat topology. This would be consistent with an infinite physical universe.<ref name="NASA_Shape">{{cite web| title=Will the Universe expand forever?| url=http://map.gsfc.nasa.gov/universe/uni_shape.html| publisher=NASA| date=24 January 2014| access-date=16 March 2015| url-status=live| archive-url=https://web.archive.org/web/20120601032707/http://map.gsfc.nasa.gov/universe/uni_shape.html| archive-date=1 June 2012}}</ref><ref name="Fermi_Flat">{{cite web| title=Our universe is Flat| url=http://www.symmetrymagazine.org/article/april-2015/our-flat-universe?email_issue=725| publisher=FermiLab/SLAC| date=7 April 2015| url-status=live| archive-url=https://web.archive.org/web/20150410200411/http://www.symmetrymagazine.org/article/april-2015/our-flat-universe?email_issue=725| archive-date=10 April 2015}}</ref><ref>{{cite journal|title=Unexpected connections|author=Marcus Y. Yoo|journal=Engineering & Science|volume=LXXIV1|date=2011|page=30}}</ref> However, the universe could be finite, even if its curvature is flat. An easy way to understand this is to consider two-dimensional examples, such as video games where items that leave one edge of the screen reappear on the other. The topology of such games is [[torus|toroidal]] and the geometry is flat. Many possible bounded, flat possibilities also exist for three-dimensional space.<ref>{{cite book|last=Weeks|first=Jeffrey|title=The Shape of Space|year=2001|publisher=CRC Press|isbn=978-0-8247-0709-5|url-access=registration|url=https://archive.org/details/shapeofspace0000week}}</ref> The concept of infinity also extends to the [[multiverse]] hypothesis, which, when explained by astrophysicists such as [[Michio Kaku]], posits that there are an infinite number and variety of universes.<ref>Kaku, M. (2006). Parallel worlds. Knopf Doubleday Publishing Group.</ref> Also, [[cyclic model]]s posit an infinite amount of [[Big Bang]]s, resulting in an infinite variety of universes after each Big Bang event in an infinite cycle.<ref name="Nautilus2014">{{cite news |last1=McKee|first1=Maggie |title=Ingenious: Paul J. Steinhardt β The Princeton physicist on what's wrong with inflation theory and his view of the Big Bang |url=http://nautil.us/issue/17/big-bangs/ingenious-paul-j-steinhardt |access-date=31 March 2017 |work=Nautilus |issue=17 |publisher=NautilusThink Inc. |date=25 September 2014 |ref=Chapter 4}}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). 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