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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Anthropic principle | 5/9 | https://en.wikipedia.org/wiki/Anthropic_principle | reference | science, encyclopedia | 2026-05-05T07:04:34.679097+00:00 | kb-cron |
Some have argued that fine-tuning is not astonishing at all in itself, but only from our situated point of view, which must be factored out of the question. This argument was given in 2021 by David Chauvet in his writings on natural law, which is linked to the question of God and therefore to cosmology: the universe is only astonishing to those who value life, such as the humans who arose from it. In the same way, the number on a lottery ticket is nothing special, unless it is associated with a sum of money, which is itself valued. Without this valorization of life, fostered by the fact that observers spontaneously value it, the universe's parameters are no more astonishing than a winning lottery ticket would be to an observer for whom money holds no interest. As Chauvet argues: It is arguably not surprising that those who have emerged from and are part of a life-supporting universe value a life-supporting universe over one that does not support life, just as someone who has emerged from and is part of a society where money is important values drawing a winning lottery number rather than drawing a losing number. If we consider this, there is no longer any real reason to be astonished by the fine-tuning of our universe, any more than there would be reason to be astonished by the fine-tuning of a universe that harbored nothing that seems interesting to us in one way or another.
== Observational evidence == No possible observational evidence bears on Carter's WAP, as it is merely advice to the scientist and asserts nothing debatable. The obvious test of Barrow's SAP, which says that the universe is "required" to support life, is to find evidence of life in universes other than ours. Any other universe is, by most definitions, unobservable (otherwise it would be included in our portion of this universe). Thus, in principle Barrow's SAP cannot be falsified by observing a universe in which an observer cannot exist. Philosopher John Leslie states that the Carter SAP (with multiverse) predicts the following:
Physical theory will evolve so as to strengthen the hypothesis that early phase transitions occur probabilistically rather than deterministically, in which case there will be no deep physical reason for the values of fundamental constants; Various theories for generating multiple universes will prove robust; Evidence that the universe is fine tuned will continue to accumulate; No life with a non-carbon chemistry will be discovered; Mathematical studies of galaxy formation will confirm that it is sensitive to the rate of expansion of the universe. Hogan has emphasised that it would be very strange if all fundamental constants were strictly determined, since this would leave us with no ready explanation for apparent fine tuning. In fact, humans might have to resort to something akin to Barrow and Tipler's SAP: there would be no option for such a universe not to support life. Probabilistic predictions of parameter values can be made given:
a particular multiverse with a "measure", i.e. a well defined "density of universes" (so, for parameter X, one can calculate the prior probability P(X0) dX that X is in the range X0 < X < X0 + dX), and an estimate of the number of observers in each universe, N(X) (e.g., this might be taken as proportional to the number of stars in the universe). The probability of observing value X is then proportional to N(X) P(X). A generic feature of an analysis of this nature is that the expected values of the fundamental physical constants should not be "over-tuned", i.e. if there is some perfectly tuned predicted value (e.g. zero), the observed value need be no closer to that predicted value than what is required to make life possible. The small but finite value of the cosmological constant can be regarded as a successful prediction in this sense. One thing that would not count as evidence for the anthropic principle is evidence that the Earth or the Solar System occupied a privileged position in the universe, in violation of the Copernican principle (for possible counterevidence to this principle, see Copernican principle), unless there was some reason to think that that position was a necessary condition for our existence as observers.
== Applications of the principle ==
=== The nucleosynthesis of carbon-12 === Fred Hoyle may have invoked anthropic reasoning to predict an astrophysical phenomenon. He is said to have reasoned, from the prevalence on Earth of life forms whose chemistry was based on carbon-12 nuclei, that there must be an undiscovered resonance in the carbon-12 nucleus facilitating its synthesis in stellar interiors via the triple-alpha process. He then calculated the energy of this undiscovered resonance to be 7.6 million electronvolts. Willie Fowler's research group soon found this resonance, and its measured energy was close to Hoyle's prediction. However, in 2010 Helge Kragh argued that Hoyle did not use anthropic reasoning in making his prediction, since he made his prediction in 1953 and anthropic reasoning did not come into prominence until 1980. He called this an "anthropic myth", saying that Hoyle and others made an after-the-fact connection between carbon and life decades after the discovery of the resonance.
An investigation of the historical circumstances of the prediction and its subsequent experimental confirmation shows that Hoyle and his contemporaries did not associate the level in the carbon nucleus with life at all.
=== Cosmic inflation ===