Fine-tuned universe

The fine-tuned Universe is the idea that the conditions that allow life in the Universe can only occur when certain universal physical constants lie within a very narrow range, so that if any of several fundamental constants were only slightly different the universe would be unlikely to be conducive to the establishment and development of matter, astronomical structures, elemental diversity, or life as it is presently understood.

There is no firm scientific consensus that the fine-tuning hypothesis is correct. Among scientists who find the evidence persuasive, a variety of scientific explanations have been proposed, e.g., the anthropic principle. The idea has also attracted discussion among philosophers and theologians, as well as creationists.

Premise

Fine-tuned Universe proponents argue that deep-space structures such as the Eta Carinae Nebula would not form in a universe with significantly different physical constants. Photo: HST / NASA / ESA.

The premise of the fine-tuned universe assertion is that a small change in several of the dimensionless fundamental physical constants would make the universe radically different.

If, for example, the strong nuclear force were 2% stronger than it is (i.e., if the coupling constant representing its strength were 2% larger), diprotons would be stable and hydrogen would fuse into them instead of deuterium and helium. This would drastically alter the physics of stars, and presumably preclude the existence of life similar to what we observe on Earth. However, many of the fundamental constants describe the properties of the unstable strange, charmed, bottom and top quarks and mu and tau leptons which seem to play little part in the universe or the structure of matter.

The precise formulation of the idea is made difficult by the fact that physicists do not yet know how many independent physical constants there are. The standard model of particle physics has about 26 freely adjustable parameters. However, because the standard model is not mathematically self-consistent under certain conditions (e.g., at very high energies, at which both quantum mechanics and general relativity are relevant), physicists believe that it is underlaid by some other theory, such as a grand unified theory, string theory, or loop quantum gravity. In some candidate theories, the actual number of independent physical constants may be as small as 1. 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 these calculations, "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."

Martin Rees, formulates the fine-tuning of the universe in terms of the following six dimensionless constants:

• N = ratio of the strength of electromagnetism to that of gravity;
• Epsilon = strength of the force binding nucleons into nuclei;
• Omega = relative importance of gravity and expansion energy in the universe;
• Lambda = cosmological constant;
• Q = ratio of the gravitational energy required to pull a large galaxy apart to the energy equivalent of its mass;
• D = number of spatial dimensions in spacetime.

Disputes on the existence of fine-tuning

There are many cases where the known physical constants are argued to suggest fine tuning. However, the validity of these examples is sometimes questioned on the grounds that such reasoning is subjective anthropomorphism applied to natural physical constants. For example, Victor Stenger writes that "... The fine-tuning argument and other recent intelligent design arguments are modern versions of God-of-the-gaps reasoning, where a God is deemed necessary whenever science has not fully explained some phenomenon". Victor Stenger furthers his critical view that "... a wide variation of constants of physics leads to universes that are long-lived enough for life to evolve, although human life need not exist in such universes". These ideas are supported by other work: F.C. Adams published a paper describing the formation of stars in universes with different physical constants, which suggested that in 25% of cases it would be possible for stars to exist in some form. In a more extreme case, Harnik, Kribs and Perez argued for the viability of a universe with no weak interaction at all.

Critics suggest that the fine-tuned universe assertion and the anthropic principle are essentially tautologies. The fine-tuned universe argument has also been criticized as an argument by lack of imagination because it assumes no other forms of life, based upon alternative biochemistry, are possible . In addition, critics argue that humans are adapted to the universe through the process of evolution, rather than the universe being adapted to humans. They also see it as an example of the logical flaw of hubris or anthropocentrism in its assertion that humans are the purpose of the universe.

Possible scientific explanations

If it is accepted that the universe is fine-tuned, there are a number of scientific explanations that attempt to account for it.

There are fine tuning arguments that are naturalistic . As modern cosmology developed, various hypotheses have been proposed. One is an oscillatory universe or a multiverse where physical constants are postulated to resolve themselves to random values in different iterations of reality. Under this hypothesis, separate parts of reality would have wildly different characteristics. In such scenarios the issue of fine-tuning does not arise at all, as only those "universes" with constants hospitable to life (such as what we observe) would develop life capable of asking the question.

Based upon the Anthropic principle, physicist Robert H. Dicke proposed the "Dicke coincidence" argument that the structure (age, physical constants, etc) of the universe as seen by living observers is not random, but is constrained by biological factors that require it to be roughly a "golden age".

Multiverse

Main article: Multiverse

The Multiverse hypothesis assumes the existence of many universes with different physical constants, some of which are hospitable to intelligent life (see multiverse: anthropic principle). Because we are intelligent beings, we are by definition in a hospitable one. Mathematician Michael Ikeda and astronomer William H. Jefferys have argued that the anthropic principle resolves the entire issue of fine-tuning, as does philosopher of science Elliott Sober. Richard Swinburne reaches the opposite conclusion using Bayesian probability.

This approach has led to considerable research into the anthropic principle and has been of particular interest to particle physicists because theories of everything do apparently generate large numbers of universes in which the physical constants vary widely. As of yet, there is no evidence for the existence of a multiverse, but some versions of the theory do make predictions which some researchers studying M-theory and gravity leaks hope to see some evidence of soon. The existence of additional universes in a multiverse, other than the observable universe, is not falsifiable, and thus some are reluctant to call the multiverse idea a "scientific" idea. UNC-Chapel Hill professor Laura Mersini-Houghton claims that the WMAP cold spot may provide testable empirical evidence for a parallel universe.

Variants on this approach include Lee Smolin's notion of cosmological natural selection, the Ekpyrotic universe, and the Bubble universe theory.

Critics of the multiverse-related explanations argue that there is no evidence that other universes exist, or that these universes necessarily exhaust all possible physical properties as the anthropic principle requires.

Bubble universe theory

Main article: Chaotic inflation theory

See also: Multiverse § Bubble theory

The bubble universe model by physicist Andrei Linde, postulates that our universe is one of many that grew from a multiverse consisting of vacuum that had not yet decayed to its ground state.

According to this scenario, by means of a random quantum fluctuation the universe "tunneled" from pure vacuum ("nothing") to what is called a false vacuum, a region of space that contains no matter or radiation but is not quite "nothing." The space inside this bubble of false vacuum was curved, or warped. A small amount of energy was contained in that curvature, somewhat like the energy stored in a strung bow. This ostensible violation of energy conservation is allowed by the Heisenberg uncertainty principle for sufficiently small time intervals. The bubble then inflated exponentially and the universe grew by many orders of magnitude in a tiny fraction of a second. (For a not-too-technical discussion, see Stenger 1990). As the bubble expanded, its curvature energy was converted into matter and radiation, inflation stopped, and the more linear big bang expansion we now experience commenced. The universe cooled and its structure spontaneously froze out, as formless water vapor freezes into snowflakes whose unique patterns arise from a combination of symmetry and randomness.

— Victor J. Stenger, The Anthropic Coincidences

In standard inflation, inflationary expansion occurred while the universe was in a false vacuum state, halting when the universe decayed to a true vacuum state. The bubble universe model proposes that different parts of this inflationary universe (termed a Multiverse) decayed at different times, with decaying regions corresponding to universes not in causal contact with each other. It further supposes that each bubble universe may have different physical constants.

Alien design

The Universe may have been designed by an alien or by aliens. This would solve the problem of how a designer or design team capable of fine-tuning the Universe could come to exist. Cosmologist Alan Guth believes humans will in time be able to generate new universes. By implication previous intelligent entities may have generated our universe. This idea leads to the possibility that the extraterrestrial designer/designers are themselves the product of an evolutionary process in their own universe, which must therefore itself be able to sustain life. For instance, Richard Dawkins maintains that an alien designer or designers are more plausible than a supernatural designer or designers because there is a known mechanism to produce them. He calls it the “crane” of Natural selection.

The Simulation hypothesis promoted by Nick Bostrom and others have suggests that our universe may be a computer simulation by aliens.

The Biocosm hypothesis and the Meduso-anthropic principle both suggest that natural selection has made the universe biophilic. The universe enables intelligence because intelligent entities later create new biophilic universes. This is different from the suggestion above that aliens from a universe which is less finely tuned than ours made our universe finely tuned.

Religious opinions

As with theistic evolution, some individual scientists, theologians, and philosophers as well as certain religious groups have seized on the idea that providence or creation are responsible for fine-tuning.

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).

This apparent fine-tuning of the universe is cited by theologian William Lane Craig as an evidence for the existence of God or some form of intelligence capable of manipulating (or designing) the basic physics that governs the universe. Craig argues, however, "that the postulate of a divine Designer does not settle for us the religious question."

Variants on this approach include:

Intelligent design

Proponents of Intelligent design argue that certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection. The fine-tuned universe argument is a central premise or presented as a given in many of the published works of prominent Intelligent Design proponents, such as William A. Dembski and Michael Behe.

Other religious creation views

Most religions have some kind of account of the creation of the universe, although they generally differ in detail from the ones listed above. Some of these may be compatible with known scientific facts. For example scientist-theologians such as John Polkinghorne emphasise the implications of Anthropic Fine-Tuning within an orthodox Christian framework whilst fully accepting the scientific findings about Evolution and the age of the Universe. This is also the position of the Roman Catholic Church and of most Anglican theologians. The Jewish physicist Gerald Schroeder argues that the apparent discrepancy between the "days" in Genesis and the billions of years in a scientific understanding are due to the differences in frames of reference. Many other religious creation views are either incompatible with, or indifferent to, scientific understandings. Other scientists with similar views are physicist Freeman Dyson and astronomer Owen Gingerich.

Counter argument to religious views

The "argument from imperfection" suggests that if the universe were designed to be fine-tuned for life, it should be the best one possible and that evidence suggests that it is not. In fact, most of the universe is highly hostile to life.

In fiction and popular culture

• Stephen Baxter has written several novels and short stories in which the setting is an alternative universe with different physical laws.

• Robert J. Sawyer discusses the fine-tuned universe novel at length in his novel Calculating God (2000).

• The Sphere Builders of Star Trek: Enterprise created the Delphic Expanse in an attempt to alter the physical laws of our universe to match those of their own parallel universe.

• Author Neal Stephenson discussed the issue of fine-tuning in the conclusion to his essay In The Beginning Was The Command Line, speculating on what might happen if an all-powerful entity had access to a computer program that could generate universes with any desired set of properties.

The demiurge sits at his teletype, pounding out one command line after another, specifying the values of fundamental constants of physics:

universe -G 6.672e-11 -e 1.602e-19 -h 6.626e-34 -protonmass 1.673e-27....

and when he's finished typing out the command line, his right pinky hesitates above the ENTER key for an aeon or two, wondering what's going to happen; then down it comes--and the WHACK you hear is another Big Bang.

Further reading

• John D. Barrow and Frank J. Tipler, 1986. The Anthropic Cosmological Principle. Oxford Univ. Press. ISBN 0-19-282147-4
• John D. Barrow, 2003. The Constants of Nature, Pantheon Books, ISBN 0-375-42221-8
• Paul Davies, 1982. The Accidental Universe, Cambridge University Press, ISBN 0-521-24212-6
• Simon Conway Morris, 2003. Life's Solution: Inevitable Humans in a Lonely Universe. Cambridge Univ. Press.
• Ward, P. D., and Brownlee, D., 2000. Rare Earth: Why Complex Life is Uncommon in the Universe. Springer Verlag.

See also

• Fine-tuning
• Origin of life
• Rare Earth hypothesis
• Teleology
• Ultimate fate of the universe

External links

• Robin Collins's Fine-Tuning Website
• Does the Cosmos Show Evidence of Purpose?
• Fine-Tuning Argument links to online references, at the Secular Web
• Cosmological fine-tuning, by Robin Collins
• Design and the Anthropic Principle by Hugh Ross
• The Anthropic Principle Does Not Support Supernaturalism by Michael Ikeda and Bill Jefferys
• Overview of the Cosmological Intelligent Design argument Stephen M. Barr. July 2001. First Things, the Journal of Religion, Culture, and Public Life.
• The Design Argument by Elliott Sober (Adobe PDF format)
• Home page of Templeton Foundation project on fine-tuning
• Sharpening Ockham's razor on a Bayesian strop by William H. Jefferys and James O. Berger (Adobe PDF format)
• The cosmos is fine-tuned to permit human life at the talk.origins index to creationist claims.
• Is the Universe fine-tuned for us? (Adobe PDF format)
• Interview with Charles Townes discussing science and religion.
• Evidence For Design In The Universe
• Gerald Schroeder's Fine-turned universe page