Editing Fine-tuned universe (section)

== 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>