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Fine-tuned universe
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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.
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Encyclopedia
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.
The arguments relating to the fine-tuned universe concept involve the anthropic principle, which states that any valid theory of the universe must be consistent with our existence as human beings at this particular time and place in the universe. In other words, even if the actual probability of our universe that supports intelligent life may be very low, the conditional probability of supporting intelligent life, given our existence in it, is 1. Even if there could be other universes, less "fine-tuned" and so devoid of life, there would be no one there to observe them.
Premise
The premise of the fine-tuned universe assertion is that a small change in several of the approximately 26 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 prevent the universe from developing life as it is currently observed on the earth. However, many of the 26 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.
Larry Abbott wrote: "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." John Polkinghorne, broadly following Martin Rees formulates the fine-tuning in terms of six principal constants:
- N - the ratio of the strength of the electrical forces and the strength of gravity
- Epsilon - defining how firmly atomic nuclei bind together
- Omega - which measures the relative importance of gravity and expansion energy in the universe
- Lambda - the "Cosmological Constant"
- Q - the ratio of the gravitational energy required to pull galaxies apart and their mass
- D - the number of space-like dimensions in the universe
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. Therefore 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.
There are fine tuning arguments that are naturalistic, however, the assertion that the universe was designed to be fine-tuned is largely put forward by advocates of intelligent design and other forms of creationism. This apparent fine-tuning of the universe is cited by 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."
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).
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".
Nature of the constants
Modern science as practiced since René Descartes is reductionist, meaning that it attempts to discover the most fundamental objects and rules governing the observable behavior of the universe. In descriptions of the physical universe, fundamental rules take the form of laws (usually equations relating physical quantities and properties) involving physical constants, while the fundamental objects are elementary particles with constant mass, charge, and other physical properties. This reductionism is a pragmatic approach that obtains results and is not a philosophical position on ontology. The nature of these constants is a much debated topic in physics and metaphysics (see string theory).
Meaning of "universe"
Both popular and professional research articles in cosmology often use the term "universe" to refer to the observable universe. The reason for this usage is that only observable phenomena are scientifically relevant. Since unobservable phenomena have no perceptible effects, physicists argue that they "causally do not exist". Since unobservable parts of the universe cannot be measured, hypotheses about them are not testable, and thus inappropriate for a scientific theory.
In metaphysics, "universe" refers to everything that exists. This encompasses both observable and unobservable phenomena. Metaphysics seeks to describe everything that is knowable about existence.
All the arguments that refer to the observable universe would not necessarily apply to the unobservable parts of reality sometimes called "other universes", if such there be. Although our observable universe has the parameters necessary for carbon based life, other parts of a larger multiverse may be sterile, or may have physical parameters conducive to different types of life or other, possibly self-aware, systems.
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 demonstrated 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.
Naturalistic possibilities
If it is accepted that the universe is fine-tuned, there are a number of naturalistic explanations that attempt to account for it.
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. 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, 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.
Bubble universe 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.
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. Leading 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 writes:
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.
Counterarguments to Naturalistic Hypotheses
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. Against the specific Bubble universe Hypothesis described above, Craig argues "Inflationary models not only face the problems of how to get the inflation started, how to get it to end without excess turbulence, and how to get it to allow galaxy formation, but more importantly they themselves require an extraordinary amount of fine-tuning prior to inflation, so that the appearance of design is not eluded".
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.
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 fully compatible with known scientific facts (notwithstanding their use of metaphysical ideas which are beyond the domain of science). 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, of whom Alister McGrath is probably the most prolific in this area. 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.
An implication of intelligent design may be that the designer is benevolent and, as such, the constants and structures of the universe are "life-friendly". However such intelligent designer may conceivably be malevolent.
Bayesian arguments
A Bayesian probabilistic discussion by mathematician Michael Ikeda and astronomer William H. Jefferys in 2006 argues that the traditional reasoning about intelligent design from the presence of fine-tuning does not properly condition on the existence of life and is also based on an incorrect reversal of conditional probabilities. They argue that it is an example of the prosecutor's fallacy, which in this form erroneously claims that if fine-tuning is rare in naturalistic universes, then a fine-tuned universe is unlikely to be naturalistic.
The philosopher of science Elliott Sober makes a similar argument (2004). Richard Swinburne reaches the opposite conclusion using Bayesian probability (Swinburne 1990).
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. The most obvious example is Raft in which the force of gravity is a billion times stronger than in our universe. The novel, Time of the Manifold sequence includes the interesting concept that the universe itself is not perfectly tuned for life to exist and is still in the process of evolution itself. The climax of the book involves the destruction of the universe so that a new version, better suited to life, may replace it.
- Robert J. Sawyer discusses the fine-tuned universe novel at length in his Hugo Award-nominated novel Calculating God (2000), which features an alien race that has developed a grand unified theory that includes these conclusions (presented in dialog):
Sawyer also explores the fine-tuned universe argument in his short story The Abdication of Pope Mary III, first published in Nature: International Weekly Journal of Science, July 6, 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. Their form of life was not compatible with the current physical laws of our universe (as evidenced by their quickly decaying bodies), and thus needed to make said changes in order to conquer and live in our 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.
See also
External links
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- , at the Secular Web
- , by Robin Collins
- by Hugh Ross
- by Michael Ikeda and Bill Jefferys
- Stephen M. Barr. July 2001. First Things, the Journal of Religion, Culture, and Public Life.
- by Elliott Sober (Adobe PDF format)
- by William H. Jefferys and James O. Berger (Adobe PDF format)
- at the talk.origins index to creationist claims.
- (Adobe PDF format)
- with Charles Townes discussing science and religion.
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