Editing Fine-tuned universe

{{Short description|Hypothesis about life in the universe}}
{{for|the concept of a fine-tuned Earth|Rare Earth hypothesis}}
{{pp-pc}}
{{Use dmy dates|date=March 2024}}
{{Physical cosmology}} 
{{Intelligent Design}}

'''The fine-tuned universe''' is the hypothesis that, because "life as we know it" could not exist if the [[fundamental physical constants|constants of nature]] – such as the [[electron charge]], the [[gravitational constant]] and others – had been even slightly different, the universe must be tuned specifically for life.<ref name= ":0">{{Cite book |title = Just Six Numbers: The Deep Forces That Shape The Universe|last = Rees|first = Martin |publisher = Basic Books | edition= 1st American |date = May 3, 2001 |location = New York |page = 4}}</ref><ref name=":1">Gribbin. J and Rees. M, ''Cosmic Coincidences: Dark Matter, Mankind, and Anthropic Cosmology'' pp. 7, 269, 1989, {{ISBN|0-553-34740-3}}</ref><ref>{{Cite book |title = Cosmic Jackpot: Why Our Universe Is Just Right for Life |last = Davis |first = Paul |publisher = Orion Publications |year = 2007 |isbn = 978-0-61859226-5 |location = New York |page = [https://archive.org/details/cosmicjackpotwhy0000davi/page/2 2] |url = https://archive.org/details/cosmicjackpotwhy0000davi/page/2 }}</ref><ref name=":2" /> In practice, this hypothesis is formulated in terms of [[dimensionless physical constants]].<ref name=stanford_encylopedia>{{cite web|url=https://plato.stanford.edu/entries/fine-tuning/|title=Fine-Tuning|website=The Stanford Encyclopedia of Philosophy|publisher=Center for the Study of Language and Information (CSLI), Stanford University|access-date=2020-01-18|date=August 22, 2017}}</ref>

== History ==
In 1913, [[chemist]] [[Lawrence Joseph Henderson]] wrote ''The Fitness of the Environment,'' one of the first books to explore fine tuning in the universe. Henderson discusses the importance of water and the environment to living things, pointing out that life as it exists on Earth depends entirely on Earth's very specific environmental conditions, especially the prevalence and properties of water.<ref>{{Cite book |last=Henderson |first=Lawrence Joseph |title=The fitness of the environment: an inquiry into the biological significance of the properties of matter |publisher=The Macmillan Company |year=1913 |lccn=13003713 |oclc=1146244 |ol=6554703M}}</ref>

In 1961, physicist [[Robert H. Dicke]] argued that certain forces in physics, such as [[gravity]] and [[electromagnetism]], must be perfectly fine-tuned for life to exist in the universe.<ref name=Dicke>{{cite journal | author-link = Robert Dicke |author = R. H. Dicke|s2cid = 4196678| journal = Nature | title = Dirac's Cosmology and Mach's Principle | volume = 192 | pages = 440–41| date = 1961 | doi = 10.1038/192440a0 | bibcode = 1961Natur.192..440D | issue=4801}}</ref><ref>[[John L. Heilbron|Heilbron, J. L.]], ''The Oxford Guide to the History of Physics and Astronomy'', Volume 10 (Oxford: Oxford University Press, 2005), [https://books.google.com/books?id=WqyudPS7EZEC&pg=PA8&redir_esc=y#v=onepage&q&f=false p. 8].</ref>

Astronomer [[Fred Hoyle]] argued for a fine-tuned universe: "From 1953 onward, Willy Fowler and I have always been intrigued by the remarkable relation of [...] and your fixing would have to be just where these levels are actually found to be. [...] A common sense interpretation of the facts suggests that a superintellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature."<ref>[[Fred Hoyle|Hoyle, F.]], ''The Universe: Past and Present Reflections'' | Department of Applied Mathematics and Astronomy, University College, 1981).</ref> In his 1983 book ''The Intelligent Universe'',<ref>[[Fred Hoyle|Hoyle, F.]], ''The Intelligent Universe'' ([[London]]: [[Michael Joseph (publisher)|Michael Joseph Ltd]], 1983).</ref> Hoyle wrote, "The list of anthropic properties, apparent accidents of a non-biological nature without which carbon-based and hence human life could not exist, is large and impressive."<ref>[http://www.optcorp.com/edu/articleDetailEDU.aspx?aid=1530 Profile of Fred Hoyle at OPT] {{webarchive|url=https://web.archive.org/web/20120406200054/http://www.optcorp.com/edu/articleDetailEDU.aspx?aid=1530 |date=2012-04-06 }}. Optcorp.com. Retrieved on 2019-08-02.</ref>

Belief in the fine-tuned universe led to the expectation that the [[Large Hadron Collider]] would produce evidence of [[physics beyond the Standard Model]], such as [[supersymmetry]],<ref name=rosaler>
{{cite web
 |title=Fine Tuning Is Just Fine: Why it's not such a problem that the Large Hadron Collider hasn't found new physics.
 |url=https://nautil.us/fine-tuning-is-just-fine-7681/
 |last=Rosaler
 |first=Joshua
 |website=Nautil.us
 |publisher=NautilusThink Inc
 |date=2018-09-20
 |access-date=2020-01-18
}}</ref> but by 2012 it had not produced evidence for supersymmetry at the energy scales it was able to probe.<ref>
{{cite magazine
 |url=https://www.quantamagazine.org/physicists-debate-future-of-supersymmetry-20121120/
 |title=As Supersymmetry Fails Tests, Physicists Seek New Ideas
 |last=Wolchover
 |first=Natalie
 |authorlink=Natalie Wolchover
 |magazine=[[Quanta Magazine]]
 |date=2012-11-20
 |access-date=2020-01-18
}}</ref>

== Motivation ==
Physicist [[Paul Davies]] said: "There is now broad agreement among physicists and cosmologists that the Universe is in several respects 'fine-tuned' for life. But the conclusion is not so much that the Universe is fine-tuned for life; rather it is fine-tuned for the building blocks and environments that life requires".<ref>Smith, W. S., Smith, J. S., & Verducci, D., eds., ''Eco-Phenomenology: Life, Human Life, Post-Human Life in the Harmony of the Cosmos'' (Berlin/Heidelberg: Springer, 2018), [https://books.google.com/books?id=4-piDwAAQBAJ&pg=PA131&redir_esc=y#v=onepage&q&f=false pp. 131–32].</ref> He also said that {{" '}}[[Anthropic principle|anthropic]]' reasoning fails to distinguish between minimally [[Biophilia hypothesis|biophilic]] universes, in which life is permitted, but only marginally possible, and optimally biophilic universes, in which life flourishes because [[biogenesis]] occurs frequently".<ref name=Davies200>{{cite journal |author1=Davies |title=How bio-friendly is the universe |date=2003 |volume=2 |issue=115 |journal=Int. J. Astrobiol. |arxiv=astro-ph/0403050 |doi=10.1017/S1473550403001514 |page=115|bibcode = 2003IJAsB...2..115D |s2cid=13282341 }}</ref> Among scientists who find the evidence persuasive, a variety of [[Naturalism (philosophy)|natural explanations]] have been proposed, such as the existence of [[multiverse|multiple universes]] introducing a [[survivorship bias]] under the [[anthropic principle]].<ref name=stanford_encylopedia/>

The premise of the fine-tuned universe assertion is that a small change in several of the physical constants would make the universe radically different. [[Stephen Hawking]] observed: "The laws of science, as we know them at present, contain many fundamental numbers, like the size of the electric charge of the electron and the ratio of the masses of the proton and the electron. ... The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life".<ref name=":2">[[Stephen Hawking]], 1988. ''A Brief History of Time,'' Bantam Books, {{ISBN|0-553-05340-X}}, pp. 7, 125.</ref>

For example, if the strong nuclear force were 2% stronger than it is (i.e. if the [[coupling constant]] representing its strength were 2% larger) while the other constants were left unchanged, [[diproton]]s would be stable; according to Davies, hydrogen would [[hydrogen fusion|fuse]] into them instead of [[deuterium]] and [[helium]].<ref name=Davies1993>Paul Davies, 1993. ''The Accidental Universe'', Cambridge University Press, [https://books.google.com/books?id=s2s4AAAAIAAJ&lpg=PP1&hl=cs&pg=PA70&redir_esc=y#v=onepage&q&f=false pp. 70–71]</ref> This would drastically alter the physics of [[star]]s, and presumably preclude the existence of life similar to what we observe on Earth. The diproton's existence would short-circuit the slow fusion of hydrogen into deuterium. Hydrogen would fuse so easily that it is likely that all the universe's hydrogen would be consumed in the first few minutes after the [[Big Bang]].<ref name=Davies1993/> This "diproton argument" is disputed by other physicists, who calculate that as long as the increase in strength is less than 50%, stellar fusion could occur despite the existence of stable diprotons.<ref name =macdonald>{{cite journal | last1 = MacDonald | first1 = J. | last2 = Mullan | first2 = D. J. | year = 2009 | title = Big Bang nucleosynthesis: The strong nuclear force meets the weak anthropic principle | journal = [[Physical Review D]] | volume = 80 | issue = 4| page = 043507 |quote=Contrary to a common argument that a small increase in the strength of the strong force would lead to destruction of all hydrogen in the Big Bang due to binding of the diproton and the dineutron with a catastrophic impact on life as we know it, we show that provided the increase in strong force coupling constant is less than about 50% substantial amounts of hydrogen remain. | doi=10.1103/physrevd.80.043507| arxiv = 0904.1807 | bibcode = 2009PhRvD..80d3507M | s2cid = 119203730 }}</ref>

The precise formulation of the idea is made difficult by the fact that it is not yet known how many independent physical constants there are. The [[standard model of particle physics]] has 25 freely adjustable parameters and [[general relativity]] has one more, the [[cosmological constant]], which is [[Accelerating expansion of the universe|known to be nonzero]] but profoundly small in value. Because physicists have not developed an empirically successful theory of [[quantum gravity]], there is no known way to combine quantum mechanics, on which the standard model depends, and general relativity.<ref name="The Mystery of the Cosmological Con">
{{cite journal
 | last1 = Abbott | first1 = Larry
 | authorlink = Larry Abbott
 | date = May 1988
 | title = The Mystery of the Cosmological Constant | journal = [[Scientific American]]
 | volume=258
 | issue = 5
 | pages=106–13
 | doi=10.1038/scientificamerican0588-106
 | bibcode = 1988SciAm.258e.106A
}}</ref>

Without knowledge of this more complete theory suspected to underlie the standard model, it is impossible to definitively count the number of truly independent physical constants. In some candidate theories, the number of independent physical constants may be as small as one. For example, the cosmological constant may be a fundamental constant but attempts have also been made to calculate it from other constants, and according to the author of one such calculation, "the small value of the cosmological constant is telling us that a remarkably precise and totally unexpected relation exists among all the parameters of the [[Standard Model of particle physics]], the bare cosmological constant and unknown physics".<ref name="The Mystery of the Cosmological Con"/>

== Examples ==
[[Martin Rees]] formulates the fine-tuning of the universe in terms of the following six [[dimensionless physical constant]]s.<ref name=":0" /><ref name="discover nov 2000 cover story">{{cite magazine|last1=Lemley|first1=Brad|title=Why is There Life?|date=1 November 2000|publisher=Kalmbach Publishing Co.|url=https://www.discovermagazine.com/the-sciences/why-is-there-life|access-date=25 April 2025|magazine=[[Discover magazine]]|archive-url=https://web.archive.org/web/20140722210250/http://discovermagazine.com/2000/nov/cover/|archive-date=2014-07-22}}</ref>
* ''N'', the ratio of the electromagnetic force to the gravitational force between a pair of protons, is approximately 10<sup>36</sup>. According to Rees, if it were significantly smaller, only a small and short-lived universe could exist.<ref name="discover nov 2000 cover story" /> If it were large enough<!--clarify by what extent -->, they would repel them so violently that larger atoms would never be generated.
* ''Epsilon'' (''ε''), a measure of the nuclear efficiency of [[Stellar nucleosynthesis#Hydrogen fusion|fusion from hydrogen to helium]], is 0.007: when four nucleons fuse into helium, 0.007 (0.7%) of their mass is converted to energy. The value of ''ε'' is in part determined by the strength of the [[strong nuclear force]].<ref>{{cite book|last1=Morison|first1=Ian|title=Introduction to astronomy and cosmology|date=2013|publisher=Wiley|location=Hoboken, NJ|isbn=978-1118681527|chapter=9.14: A universe fit for intelligent life}}<!--|access-date=13 May 2016--></ref> If ''ε'' were 0.006, a proton could not bond to a neutron, and only hydrogen could exist, and complex chemistry would be impossible. According to Rees, if it were above 0.008, no hydrogen would exist, as all the hydrogen would have been fused shortly after the [[Big Bang]]. Other physicists disagree, calculating that substantial hydrogen remains as long as the strong force coupling constant increases by less than about 50%.<ref name=macdonald /><ref name="discover nov 2000 cover story" />
* ''Omega'' (Ω), commonly known as the [[Density parameter#Density parameter|density parameter]], is the relative importance of gravity and expansion energy in the universe. It is the ratio of the mass density of the universe to the "critical density" and is approximately 1. If gravity were too strong compared with dark energy and the initial cosmic expansion rate, the universe would have collapsed before life could have evolved. If gravity were too weak, no stars would have formed.<ref name="discover nov 2000 cover story" /><ref>{{cite AV media | author=[[Sean Carroll (physicist)|Sean Carroll]] and [[Michio Kaku]] | title=How the Universe Works 3 | volume=End of the Universe | date=2014 | publisher=Discovery Channel}}</ref>
* ''Lambda'' (Λ), commonly known as the [[cosmological constant]], describes the ratio of the density of [[dark energy]] to the critical energy density of the universe, given certain reasonable assumptions such as that dark energy density is a constant. In terms of [[Planck units]], and as a natural dimensionless value, Λ is on the order of {{val|e=-122}}.<ref>{{cite journal|arxiv=1105.3105|doi=10.1007/s10714-011-1199-1|title=The value of the cosmological constant|journal=General Relativity and Gravitation|volume=43|issue=10|pages=2555–60|year=2011|last1=Barrow|first1=John D.|last2=Shaw|first2=Douglas J.|bibcode=2011GReGr..43.2555B|s2cid=55125081}}</ref> This is so small that it has no significant effect on cosmic structures that are smaller than a billion light-years across. A slightly larger value of the cosmological constant would have caused [[spacetime|space]] to expand rapidly enough that stars and other astronomical structures would not be able to form.<ref name="discover nov 2000 cover story" /><ref name=susskind>{{cite web|last=Ananthaswamy|first=Anil|author-link=Anil Ananthaswamy|title=Is the Universe Fine-Tuned for Life? |date=7 March 2012 |url=https://www.pbs.org/wgbh/nova/blogs/physics/2012/03/is-the-universe-fine-tuned-for-life/|publisher=Public Broadcasting Service (PBS)}}</ref>
* ''Q'', the ratio of the gravitational energy required to pull a large galaxy apart to the energy equivalent of its mass, is around 10<sup>−5</sup>. If it is too small, no stars can form. If it is too large, no stars can survive because the universe is too violent, according to Rees.<ref name="discover nov 2000 cover story" />
* ''D'', the number of spatial [[dimensionality|dimensions in spacetime]], is 3. Rees claims that life could not exist if there were 2 or 4 spatial dimensions.<ref name="discover nov 2000 cover story" /> Rees argues this does not preclude the existence of [[String theory#Number of dimensions|ten-dimensional strings]].<ref name=:0 />
[[Max Tegmark]] argued that if there is more than one time dimension, then physical systems' behavior could not be predicted reliably from knowledge of the relevant [[partial differential equation]]s. In such a universe, intelligent life capable of manipulating technology could not emerge. Moreover, [[proton]]s and [[electron]]s would be unstable and could decay into particles having greater mass than themselves. This is not a problem if the particles have a sufficiently low temperature.<ref name="tegmark-dim">{{cite journal| last = Tegmark| first = Max| author-link = Max Tegmark| title = On the dimensionality of spacetime| journal = Classical and Quantum Gravity| volume = 14 | issue = 4| pages = L69–L75| date= April 1997| url = https://space.mit.edu/home/tegmark/dimensions.pdf| doi = 10.1088/0264-9381/14/4/002| access-date = 2006-12-16 |arxiv = gr-qc/9702052 |bibcode = 1997CQGra..14L..69T| s2cid = 15694111}}</ref>

=== Carbon and oxygen ===
{{Further|Triple-alpha process#Improbability and fine-tuning}}
An older example is the [[Hoyle state]], the third-lowest energy state of the [[carbon-12]] nucleus, with an energy of 7.656&nbsp;MeV above the ground level.<ref>[[Evry Schatzman|Schatzman, E. L.]], & Praderie, F., ''The Stars'' ([[Berlin]]/[[Heidelberg]]: [[Springer Science+Business Media|Springer]], 1993), [https://books.google.com/books?id=FtZ_cNTPv8gC&pg=PA125&redir_esc=y#v=onepage&q&f=false pp. 125–27].</ref> According to one calculation, if the state's energy level were lower than 7.3 or greater than 7.9&nbsp;MeV, insufficient carbon would exist to support life. To explain the universe's abundance of carbon, the Hoyle state must be further tuned to a value between 7.596 and 7.716&nbsp;MeV. A similar calculation, focusing on the underlying fundamental constants that give rise to various energy levels, concludes that the [[strong force]] must be tuned to a precision of at least 0.5%, and the electromagnetic force to a precision of at least 4%, to prevent either carbon production or oxygen production from dropping significantly.<ref>{{cite journal|last1=Livio|first1=M.|authorlink1=Mario Livio|last2=Hollowell|first2=D.|last3=Weiss|first3=A.|last4=Truran|first4=J. W.|authorlink4=James W. Truran|s2cid=4273737|title=The anthropic significance of the existence of an excited state of 12C|journal=Nature|date=27 July 1989|volume=340|issue=6231|pages=281–84|doi=10.1038/340281a0|bibcode = 1989Natur.340..281L }}</ref>

== Explanations ==
Some explanations of fine-tuning are [[Metaphysical naturalism|naturalistic]].<ref>[[John Hinnells|Hinnells, J.]], ''The Routledge Companion to the Study of Religion'' ([[Abingdon-on-Thames]]: [[Routledge]], 2010), [https://books.google.com/books?id=1M-OAgAAQBAJ&pg=PA119&redir_esc=y#v=onepage&q&f=false pp. 119, 125].</ref> First, the fine-tuning might be an illusion: more fundamental physics may explain the apparent fine-tuning in physical parameters in the current understanding by constraining the values those parameters are likely to take. As [[Lawrence Krauss]] put it, "certain quantities have seemed inexplicable and fine-tuned, and once we understand them, they don't seem to be so fine-tuned. We have to have some historical perspective".<ref name=susskind/> [[Victor J. Stenger]] has shown that random selection of physical parameters can still produce universes capable of harboring life.<ref>{{Cite web |last=Lewis |first=Geraint |date=12 September 2011 |title=Peer Review: The Fallacy of Fine-Tuning |url=https://theconversation.com/peer-review-the-fallacy-of-fine-tuning-2540 |access-date=31 May 2025 |website=The Conversation}}</ref> Some argue it is possible that a final fundamental [[theory of everything]] will explain the underlying causes of the apparent fine-tuning in every parameter.<ref>{{cite magazine|last1=O'Keefe |first1=Madeleine |title=Fine-tuning versus naturalness |url=https://www.symmetrymagazine.org/article/fine-tuning-versus-naturalness |magazine=Symmetry Magazine |access-date=18 February 2021 |date=28 January 2020}}</ref><ref name=susskind/>

Still, as modern cosmology developed, various hypotheses not presuming hidden order have been proposed. One is a [[multiverse]], where fundamental physical constants are postulated to have different values outside of the known universe.<ref>{{cite journal| first=Max| last=Tegmark|authorlink=Max Tegmark|journal=Scientific American|date=May 2003| title=Parallel Universes| doi=10.1038/scientificamerican0503-40| volume=288| issue=5| pages=40–51| pmid=12701329|arxiv = astro-ph/0302131 |bibcode = 2003SciAm.288e..40T }}</ref><ref>[[John Archibald Wheeler|Wheeler, J. A.]], "Genesis and Observership," in R. E. Butts, [[Jaakko Hintikka|J. Hintikka]], eds., ''Foundational Problems in the Special Sciences'' ([[Dordrecht]]: [[D. Reidel]], 1977), [https://books.google.com/books?id=OEfzCAAAQBAJ&newbks=1&newbks_redir=0&printsec=frontcover&pg=PA3&hl=en&redir_esc=y#v=onepage&q&f=false pp. 3–33].</ref>{{rp|3–33}} On this hypothesis, separate parts of reality would have wildly different characteristics. In such scenarios, the appearance of fine-tuning is explained as a consequence of the weak [[anthropic principle]] and [[selection bias]], specifically [[survivorship bias]]. Only those universes with fundamental constants hospitable to life, such as on Earth, could contain life forms capable of observing the universe who can contemplate the question of fine-tuning.<ref>{{cite book |last=Bostrom |first=N. |author-link=Nick Bostrom |url=https://books.google.com/books?id=2UpUAQAAQBAJ |title=Anthropic Bias: Observation Selection Effects in Science and Philosophy |date=2002 |publisher=Routledge |isbn=978-0-415-93858-7 |chapter=Fine-Tuning in Cosmology |chapter-url=https://anthropic-principle.com/q=book/chapter_2/}}</ref> Zhi-Wei Wang and [[Samuel L. Braunstein]] argue that the apparent fine-tuning of fundamental constants could be due to the lack of understanding of these constants.<ref name="Sciama's argument on life in a rand">{{cite journal |last1=Wang |first1=Zhi-Wei |last2=Braunstein |first2=Samuel L. |year=2023 |title=Sciama's argument on life in a random universe and distinguishing apples from oranges |journal=Nature Astronomy |volume=7 |issue=2023 |pages=755–756 |doi=10.1038/s41550-023-02014-9 |arxiv=2109.10241 |bibcode=2023NatAs...7..755W }}</ref>

=== Multiverse ===
{{Main|Multiverse}}
{{See also|Anthropic principle}}
If the universe is just one of many and possibly infinite universes, each with different physical phenomena and constants, it is unsurprising that there is a universe hospitable to intelligent life. Some versions of the multiverse hypothesis therefore provide a simple explanation for any fine-tuning,<ref name=stanford_encylopedia/> while the analysis of Wang and Braunstein challenges the view that this universe is unique in its ability to support life.<ref name="Sciama's argument on life in a rand"/>

The multiverse idea has led to considerable research into the anthropic principle and has been of particular interest to [[particle physics|particle physicist]]s because [[theory of everything|theories of everything]] do apparently generate large numbers of universes in which the physical constants vary widely. Although there is no evidence for the existence of a multiverse, some versions of the theory make predictions of which some researchers studying [[M-theory]] and gravity leaks hope to see some evidence soon.<ref name = "Michio Kaku">[[Michio Kaku|Kaku, M.]], [[Parallel Worlds (book)|''Parallel Worlds'']] (New York: [[Doubleday (publisher)|Doubleday]], 2004), pp. 220–221.</ref> According to [[Laura Mersini-Houghton]], the [[WMAP cold spot#Parallel universe|WMAP cold spot]] could provide testable empirical evidence of a [[multiverse|parallel universe]].<ref>{{cite web|url=https://www.bbc.co.uk/programmes/b00vdkmj |title=Two Programmes – Horizon, 2010–2011, What Happened Before the Big Bang? |publisher=BBC |access-date=2011-01-02}}</ref> Variants of this approach include [[Lee Smolin]]'s notion of cosmological [[natural selection]], the [[ekpyrotic universe]], and the [[Eternal inflation#Overview|bubble universe theory]].<ref name="Michio Kaku" />{{rp|220–221}}

It has been suggested that invoking the multiverse to explain fine-tuning is a form of the [[inverse gambler's fallacy]].<ref>{{cite journal |last1=Hacking |first1=Ian |authorlink=Ian Hacking|title=The Inverse Gambler's Fallacy: the Argument from Design. The Anthropic Principle Applied to Wheeler Universes |journal=Mind |date=1 July 1987 |volume=96 |issue=383 |pages=331–340 |doi=10.1093/mind/XCVI.383.331}}</ref><ref>{{cite web |last1=Goff |first1=Philip |authorlink=Philip Goff (philosopher)|title=Why the Multiverse Can't Explain Fine-Tuning |date=8 June 2022 |url=https://conscienceandconsciousness.com/2022/06/08/why-the-multiverse-cant-explain-fine-tuning/ |access-date=June 8, 2022}}</ref>

=== Top-down cosmology ===
[[Stephen Hawking]] and [[Thomas Hertog]] proposed that the universe's initial conditions consisted of a [[Quantum superposition|superposition]] of many possible initial conditions, only a small fraction of which contributed to the conditions seen today.<ref>
{{Cite journal
 | last = Ball
 | first = Philip
 | authorlink = Philip Ball
 | title = Hawking Rewrites History...Backwards
 | journal = [[Nature (journal)|Nature]]
 | date = June 21, 2006
 | pages = news060619–6
 | url = https://www.nature.com/news/2006/060619/full/news060619-6.html
 | access-date = April 19, 2010| doi = 10.1038/news060619-6
 | s2cid = 122979772
}}</ref> According to their theory, the universe's "fine-tuned" physical constants are inevitable, because the universe "selects" only those histories that led to the present conditions. In this way, top-down cosmology provides an anthropic explanation for why this universe allows matter and life without invoking the multiverse.<ref>{{Cite journal | last1=Hawking | first1=S. W. | author-link1=Stephen Hawking | last2=Hertog | first2=Thomas |date=February 2006 | title=Populating the Landscape: A Top Down Approach | journal=Phys. Rev. | volume=D73 | page=123527 | arxiv=hep-th/0602091v2 | doi=10.1103/PhysRevD.73.123527 |bibcode = 2006PhRvD..73l3527H | issue=12 | s2cid=9856127 | url=https://cds.cern.ch/record/928933 }}</ref>

=== Carbon chauvinism ===
Some forms of fine-tuning arguments about the formation of life assume that only carbon-based life forms are possible, an assumption sometimes called [[carbon chauvinism]].<ref name="stenger">{{cite web|last=Stenger|first=Victor J.|author-link=Victor J Stenger|title=Is The Universe Fine-Tuned For Us?|url=http://www.colorado.edu/philosophy/vstenger/Cosmo/FineTune.pdf#search=%22Fine%20tuned%20universe%22|url-status=dead|archive-url=https://web.archive.org/web/20120716192004/http://www.colorado.edu/philosophy/vstenger/Cosmo/FineTune.pdf#search=%22Fine%20tuned%20universe%22|archive-date=2012-07-16|publisher=University of Colorado}}</ref> Conceptually, [[alternative biochemistry]] or other forms of life are possible.<ref>See, e.g. [[Jack Cohen (biologist)|Cohen, J.]], & [[Ian Stewart (mathematician)|Stewart, I.]]: ''What Does a Martian Look Like: The Science of Extraterrestrial Life'', Wiley, 2002, p. 159.</ref>

=== Simulation hypothesis ===
The [[simulation hypothesis]] holds that the universe is fine-tuned simply because the more technologically advanced simulation operator(s) programmed it that way.<ref>{{cite journal | doi=10.1017/S1477175617000094 | title=The Fine-Tuning Argument and the Simulation Hypothesis | year=2017 | last1=Mizrahi | first1=Moti | journal=[[Think (journal)|Think]] | volume=16 | issue=46 | pages=93–102 | s2cid=171655427 | url=https://philpapers.org/archive/MIZTFA.pdf}}</ref>

=== No improbability ===
[[Graham Priest]], [[Mark Colyvan]], [[Jay L. Garfield]], and others have argued against the presupposition that "the laws of physics or the boundary conditions of the universe could have been other than they are".<ref>Colyvan, M., J. L. Garfield & G. Priest (2005). [http://www.colyvan.com/papers/finetuning.pdf "Problems with the Argument from Fine Tuning"]. ''Synthese'' 145 (3), pp. 325–338.</ref>

== Religious apologetics ==
{{See also|Teleological Argument#Fine-tuned universe}}

Some scientists, [[theologian]]s, and [[philosopher]]s, as well as certain religious groups, argue that [[Divine Providence|providence]] or [[Creation myth|creation]] are responsible for fine-tuning.<ref>Colyvan ''et al''. (2005). [http://colyvan.com/papers/finetuning.pdf ''Problems with the Argument from Fine Tuning'']. Synthese 145: 325–38.</ref><ref>Michael Ikeda and [[William H. Jefferys]], "The Anthropic Principle Does Not Support Supernaturalism," in ''The Improbability of God,'' [[Michael Lou Martin|Michael Martin]] and Ricki Monnier, editors, pp. 150–66. [[Amherst, New York|Amherst, NY]]: [[Prometheus Books]]. {{ISBN|1-59102-381-5}}.</ref><ref>[[Robert L. Park|Park, Robert L]]. (2009). ''Superstition: Belief in the Age of Science''. [[Princeton University Press]], [https://books.google.com/books?id=1XocNrUN_K4C&pg=PA11&redir_esc=y#v=onepage&q&f=false p. 11]. {{ISBN|978-0-691-13355-3}}</ref><ref>{{cite journal|last=Chown|first=Marcus|author-link=Marcus Chown|title=Why the universe wasn't fine-tuned for life|journal=New Scientist|volume=210|issue=2816|pages=49|date=14 June 2011|url=https://newscientist.com/blogs/culturelab/2011/06/why-the-universe-wasnt-fine-tuned-for-life.html|url-status=dead|archive-url=https://web.archive.org/web/20110614204934/https://newscientist.com/blogs/culturelab/2011/06/why-the-universe-wasnt-fine-tuned-for-life.html|archive-date=14 June 2011|bibcode=2011NewSc.210R..49C|doi=10.1016/S0262-4079(11)61395-X|url-access=subscription}}</ref><ref>[[Elliott Sober|Sober, E.]], 2004. "The Design Argument", in W. E. Mann, ed., ''The Blackwell Guide to the Philosophy of Religion'', [https://books.google.com/books?id=JhrPCWgqOfwC&pg=PT117 ch. 6]. [[Wiley-Blackwell#Blackwell Publishing history|Blackwell Publishing]]. {{ISBN|0-631-22129-8}}.</ref> Christian philosopher [[Alvin Plantinga]] argues that random chance, applied to a single and sole universe, only raises the question as to why this universe could be so "lucky" as to have precise conditions that support life at least at some place (the Earth) and time (within millions of years of the present).

{{Blockquote|One reaction to these apparent enormous [[Anthropic principle#Anthropic 'coincidences'|coincidences]] is to see them as substantiating the theistic claim that the universe has been created by a personal God and as offering the material for a properly restrained theistic argument{{snd}}hence the fine-tuning argument. It's as if there are a large number of dials that have to be tuned to within extremely narrow limits for life to be possible in our universe. It is extremely unlikely that this should happen by chance, but much more likely that this should happen if there is such a person as God.|Alvin Plantinga|"The Dawkins Confusion: Naturalism ''ad absurdum''"<ref name=Plantinga>Alvin Plantinga, [http://philvaz.com/apologetics/DawkinsGodDelusionPlantingaReview.pdf#page=4 "The Dawkins Confusion: Naturalism ''ad absurdum'',"] ''Christianity Today'', March/April 2007</ref>}}

[[William Lane Craig]], a philosopher and [[Christian apologist]], cites this fine-tuning of the universe as [[Argument from design|evidence]] for the existence of [[God]] or some form of [[intelligent designer|intelligence]] capable of manipulating (or designing) the basic [[physics]] that governs the universe.<ref name=Craig>William Lane Craig, [https://leaderu.com/offices/billcraig/docs/teleo.html "The Teleological Argument and the Anthropic Principle"]. leaderu.com</ref> Philosopher and theologian [[Richard Swinburne]] reaches the design conclusion using [[Bayesian probability]].<ref>[[Richard Swinburne|Swinburne, R. G.]] (1990). "Argument from the fine-tuning of the Universe", in [[John A. Leslie|J. A. Leslie]], ed., ''Physical Cosmology and Philosophy''. New York: [[Crowell-Collier Publishing Company|Collier Macmillan]], pp. 154–73.</ref> Scientist and theologian [[Alister McGrath]] observed that the fine-tuning of carbon is even responsible for nature's ability to tune itself to any degree.

<blockquote>The entire biological evolutionary process depends upon the unusual chemistry of carbon, which allows it to bond to itself, as well as other elements, creating highly complex molecules that are stable over prevailing terrestrial temperatures, and are capable of conveying genetic information (especially DNA). [...] Whereas it might be argued that nature creates its own fine-tuning, this can only be done if the primordial constituents of the universe are such that an evolutionary process can be initiated. The unique chemistry of carbon is the ultimate foundation of the capacity of nature to tune itself.<ref>{{cite book|last1=McGrath|first1=Alister E.|title=A Fine-Tuned Universe: The Quest for God in Science and Theology|date=2009|publisher=Westminster John Knox Press|location=Louisville, KY|isbn=978-0664233105|page=176|edition=1st}}</ref><ref>{{cite web|url=https://biologos.org/common-questions/what-do-fine-tuning-and-the-multiverse-say-about-god|title=What is the "fine-tuning" of the universe, and how does it serve as a "pointer to God"?|website=BioLogos.org|url-status=dead|archive-url=https://web.archive.org/web/20141221081439/http://biologos.org/questions/fine-tuning|archive-date=2014-12-21}}</ref></blockquote>

Theoretical physicist and Anglican priest [[John Polkinghorne]] stated: "Anthropic fine tuning is too remarkable to be dismissed as just a happy accident".<ref>Polkinghorne, J. C., ''Science and Theology: An Introduction'' (London: [[Society for Promoting Christian Knowledge|SPCK]], 1998), [https://books.google.com/books?id=q9wnAAAAYAAJ&q=%22Anthropic+fine+tuning+is+too+remarkable+to+be+dismissed+as+just+a+happy+accident.%22 p. 75].</ref>

Theologian and philosopher [[Andrew Loke]] argues that there are only five possible categories of hypotheses concerning fine-tuning and order: (i) chance, (ii) regularity, (iii) combinations of regularity and chance, (iv) uncaused, and (v) design, and that only design gives an exclusively logical explanation of order in the universe.<ref name="Palgrave">{{cite book |last1=Loke |first1=Andrew |title=The Teleological and Kalam Cosmological Arguments Revisited |date=2022 |publisher=Palgrave |location=Cham |page=7}}</ref> He argues that the [[Kalam Cosmological Argument]] strengthens the teleological argument by answering the question "[[Problem of the creator of God|Who designed the Designer?]]".<ref name="Palgrave" />

Creationist [[Hugh Ross (astrophysicist)|Hugh Ross]] advances a number of fine-tuning hypotheses.<ref>[https://www.reasons.org/explore/blogs/todays-new-reason-to-believe Reasons to Believe] (blog)</ref><ref>{{cite book |title=Improbable Planet: How Earth Became Humanity's Home |author=Hugh Ross}}</ref> One is the existence of what Ross calls "vital poisons", which are elemental [[Nutrient#Deficiencies and toxicity|nutrients that are harmful]] in large quantities but essential for animal life in smaller quantities.<ref>{{Cite web |last=Ross |first=Hugh |date=July 1, 1999 |title=Vital Poisons |url=https://reasons.org/explore/publications/articles/vital-poisons |access-date=March 23, 2024 |website=Reasons to Believe}}</ref>

Philosopher and theologian [[Robin Collins]] argues that theism entails the expectation that God would create a reality structured to allow for scientific discovery to easily happen. According to Collins, various physical constants such as the [[fine-structure constant]] allowing for efficient energy usage, the [[baryon]]-to-[[photon]] ratio allowing for the [[cosmic microwave background]] to be discovered, and the mass of the [[Higgs boson]] allowing it to be detected are examples of the laws of physics being fine-tuned for scientific discovery.<ref>{{cite web |url=https://www.academia.edu/72611587 |title=The Fine-Tuning for Discoverability  |last=Collins |first=Robin |date=2016 |website= |publisher=Philosophy Educator Scholarship |access-date=27 August 2024 |quote=}}</ref>

Evolutionary biologist [[Richard Dawkins]] dismisses the theistic argument as "deeply unsatisfying" since it leaves the existence of God unexplained, with a God capable of calculating the fine-tuning at least as improbable as the fine-tuning itself.<ref>{{Cite book |last=Dawkins |first=Richard |title=The God Delusion |publisher=Bantam Press |year=2006 |isbn=9780593055489 |location=London |pages=143}}</ref> Against this claim, it has been argued that theism is a simple hypothesis, allowing theists to deny that God is at least as improbable as the fine-tuning.<ref>{{Cite journal |last=Miller |first=Calum |date=2016 |title=Is theism a simple hypothesis? The simplicity of omni-properties |url=https://www.cambridge.org/core/journals/religious-studies/article/abs/is-theism-a-simple-hypothesis-the-simplicity-of-omniproperties/291A381E4AB22F59807CD245C6220E94 |journal=Religious Studies |language=en |volume=52 |issue=1 |pages=45–61 |doi=10.1017/S0034412514000523 |issn=0034-4125|url-access=subscription }}</ref><ref>{{Cite journal |last=Swinburne |first=Richard |date=2010 |title=God as the Simplest Explanation of the Universe |url=https://philarchive.org/rec/SWIGAT |journal=European Journal for Philosophy of Religion |volume=2 |issue=1 |pages=3–24 |doi=10.1017/s1358246111000142}}</ref><ref>{{Cite journal |last=Sijuwade |first=Joshua R. |date=2023 |title=The Theoretical Virtues of Theism |journal=Philosophies |language=en |volume=8 |issue=6 |pages=102 |doi=10.3390/philosophies8060102 |doi-access=free |issn=2409-9287}}</ref>

[[Douglas Adams]] satirized the theistic argument in his 2002 book ''[[The Salmon of Doubt]]'':<ref>{{cite book |last=Adams |first=Douglas |url=https://books.google.com/books?id=pDchCdg9K-8C&q=imagine+a+puddle#v=snippet&q=imagine%20a%20puddle&f=false |title=The Salmon of Doubt: Hitchhiking the Galaxy One Last Time |date=2002 |publisher=Harmony Books |isbn=9781400045082 |page=131 |accessdate=January 9, 2015}}</ref><blockquote>Imagine a puddle waking up one morning and thinking, "This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact, it fits me staggeringly well, must have been made to have me in it!" </blockquote>

== See also ==
{{Portal|Philosophy}}
{{cols|colwidth=26em}}
* {{annotated link|Abiogenesis}}
* {{annotated link|Anthropic principle}}
* {{Annotated link|CHNOPS}}
* {{annotated link|Clockwork universe}}
* {{annotated link|CP violation}}
* [[Fine-tuning (disambiguation)]]
* [[God of the gaps]]
* {{annotated link|Rare Earth hypothesis}}
* {{annotated link|Teleology}}
* {{annotated link|Ultimate fate of the universe}}
* {{Annotated link|Why is there anything at all?}}{{colend}}

== References ==
{{Reflist|30em}}

== Further reading ==
{{div col|colwidth=30em}}
* {{BarrowTipler1986}}
* [[John D. Barrow]] (2003). ''The Constants of Nature'', Pantheon Books, {{ISBN|0-375-42221-8}}
* [[Bernard Carr]], ed. (2007). [https://books.google.com/books?id=U_Jm2DT_AVAC ''Universe or Multiverse?''] Cambridge University Press.
* Mark Colyvan, Jay L. Garfield, [[Graham Priest]] (2005). [http://www.colyvan.com/papers/finetuning.pdf "Problems with the Argument from Fine Tuning"]. ''Synthese ''145: 325–38.
* [[Paul Davies]] (1982). [https://books.google.com/books?id=s2s4AAAAIAAJ ''The Accidental Universe''], Cambridge University Press, {{ISBN|0-521-24212-6}}
* [[Paul Davies]] (2007). ''[[Cosmic Jackpot|Cosmic Jackpot: Why Our Universe Is Just Right for Life]]'', Houghton Mifflin Harcourt, {{ISBN|0-618-59226-1}}. Reprinted as: [https://archive.org/details/cosmicjackpotwhy0000davi ''The Goldilocks Enigma: Why Is the Universe Just Right for Life?''], 2008, Mariner Books, {{ISBN|0-547-05358-4}}.
* [[Geraint F. Lewis]] and Luke A. Barnes (2016). [https://books.google.com/books?id=_Nb4DAAAQBAJ ''A Fortunate Universe: Life in a finely tuned cosmos''], Cambridge University Press. {{ISBN|1107156610}}
* [[Alister McGrath]]  (2009). ''A Fine-Tuned Universe: The Quest for God in Science and Theology'', Westminster John Knox Press, {{ISBN|0-664-23310-4}}.
* [[Timothy J. McGrew]], Lydia McGrew, Eric Vestrup (2001). "Probabilities and the Fine-Tuning Argument: A Sceptical View". [[Mind (journal)|''Mind'']] 110: 1027–37.
* [[Simon Conway Morris]] (2003). ''Life's Solution: Inevitable Humans in a Lonely Universe''. Cambridge Univ. Press.
* [[Martin Rees]] (1999). ''Just Six Numbers'', HarperCollins Publishers, {{ISBN|0-465-03672-4}}.
* [[Elliott Sober]] (2019). ''The Design Argument.'' Cambridge University Press, {{ISBN|978-1-108-45742-2}}.
* [[Victor J. Stenger]] (2011). [https://books.google.com/books?id=h9BAXtVsfdcC ''The Fallacy of Fine-Tuning: Why the Universe Is Not Designed for Us'']. Prometheus Books. {{ISBN|978-1-61614-443-2}}.
* [[Peter Ward (paleontologist)|Peter Ward]] and [[Donald Brownlee]] (2000). [https://books.google.com/books?id=cHwpBAAAQBAJ ''Rare Earth: Why Complex Life is Uncommon in the Universe'']. Springer Verlag.
* Jeffrey Koperski (2015). [https://books.google.com/books?id=kp5EBQAAQBAJ ''The Physics of Theism: God, Physics, and the Philosophy of Science''], John Wiley & Sons {{ISBN|978-1118932803}}
{{div col end}}

== External links ==
{{Wikiquote}}
=== Defense of fine-tuning ===
* [https://www.pbs.org/wgbh/nova/blogs/physics/2012/03/is-the-universe-fine-tuned-for-life/ Anil Ananthaswamy: Is the Universe Fine-tuned for Life?]
* [[Francis Collins]], [https://web.archive.org/web/20150321221010/http://news.nationalgeographic.com/2015/03/150319-three-questions-francis-collins-nih-science/ Why I'm a man of science-and faith]. ''[[National Geographic]]'' article.
* [http://www.abc.net.au/catalyst/customuniverse/default.htm ''Custom Universe''], Documentary of fine-tuning with scientific experts.
* {{cite journal | last1 = Mawson | first1 = T. J. | year = 2011 | title = Explaining the fine tuning of the universe to us and the fine tuning of us to the universe | url = https://ora.ox.ac.uk/objects/uuid:26d2f182-e4f1-44ee-954b-d519fd375565 | journal = Philosophy | volume = 68 | pages = 25–50 | doi=10.1017/s1358246111000075| s2cid = 123203362 | url-access = subscription }}
* [[Hugh Ross (creationist)|Hugh Ross]]: [https://sites.ualberta.ca/~dlamoure/h1.pdf Evidence for the Fine Tuning of the Universe]
* [https://newsarchive.berkeley.edu/news/media/releases/2005/06/17_townes.shtml Interview] with [[Charles Townes]] discussing science and religion.

=== Criticism of fine tuning ===
* [https://infidels.org/library/modern/theism-design/#fine Bibliography of online Links to criticisms of the Fine-Tuning Argument.] Secular Web.
* [[Victor Stenger]]:
** "[https://web.archive.org/web/20150605024914/http://www.colorado.edu/philosophy/vstenger/Fallacy/FTCosmo.pdf A Case Against the Fine-Tuning of the Cosmos]"
** "[https://web.archive.org/web/20051205085645/http://www.colorado.edu/philosophy/vstenger/Cosmo/anthro.skinq.html Does the Cosmos Show Evidence of Purpose?]"
** "[https://web.archive.org/web/20120716192004/http://www.colorado.edu/philosophy/vstenger/Cosmo/FineTune.pdf Is the Universe fine-tuned for us?]"


{{God arguments}}

{{Philosophy of religion}}

{{DEFAULTSORT:Fine-Tuned Universe}}
[[Category:Anthropic principle]]
[[Category:Astronomical hypotheses]]
[[Category:Intelligent design]]
[[Category:Philosophical arguments]]
[[Category:Physical cosmology]]