On Wed, 13 Jan 1999 23:22:28 +0000 Chris Burford <cburford at gn.apc.org>
writes:
>Does anyone know the anthropic principle in cosmology?
>
>Is that idealist?
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>
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>Chris Burford
>
>London
>
The anthropic principle is actually a set of related ideas that
attempt to relate the structure of the universe and the constants
and the laws of nature to the conditions that are necessary for
the existence and evolution of life. There is not one anthropic
principle but actually four, each being more speculative than
its predecessor. The first one is the weak anthropic principle
which seems to go back to the physicist Robert Dicke in the
late 1950s. It essentially states that because we exist the
universe must be constructed in such a way so that we could
have evolved. The laws of nature must be such as to permit
the formation of carbon, hydrogen, oxygen, and nitrogen - the
four elements necessary for life as we know it. Although
at first glance the weak anthropic principle (WAP) seems trivial,
it actually has important implications for cosmology. It sets
limits on how old the universe must be. The universe must be
old enough for complex carbon-based organisms to have
evolved but it cannot be so old that the stars have become
extinguished and conditions so inhopsitable that life has
become extinct. Likewise given the fact that our universe
is an expanding one, the WAP implies that the universe
having expanded for at least ten billion years, must be
quite large (at lest ten billion light-years across). WAP
also can be seen as imposing constraints on the magnitudes
of fundamental physical constants. If Newton's gravitational
constant was even slightly different from what it is, it is
argued that the universe would have been inhospitable for
the emergence of life as we know it.
The strong anthropic principle (SAP) was introduced by British physicist, Brandon Carter. It asserts that the universe must have those properties which allow life to develop within it at some stage. This implies either the speculation that the universe is a teleological structure that was designed by an intelligence who intended that life exist (i.e. the famous argument from design that was so popular among natural theologians back in the 18th century) or it implies that there exists an ensemble of different possible universes and that we inevitably exist in one of the rare ones in which exist the right permutation of physical properties (natural laws and physical constants) which allow life to evolve. The SAP implies in some vague way that observers are necessary to give the universe "meaning."
Some physicists have argued that the role played by the observer in quantum mechanics as interpreted by the Copenhagen School allow us to formulate a more precise version of the SAP. According to the Copenhagen Interpretation, no phenomenon exists unless it is oberved because obervers are necessary to collapse quantum wave functions. The theoretical physicist John Wheeler has formulated what he calls the particpatory anthropic principle based on the Copenhagen Interpretation of quantum mechanics. According to the participatory anthropic principle (PAP) observers must exist for the universe to come into being. SOme physicists suggest that obervers may not have to be conscious but Eugen Wigner argued that consciousness was required for the collapsing of wave functions. On the other hand if we reject the Copenhagen Interpretation in favor of the Multiple worlds Interpretation (first proposed by Hugh Everett) according to which quantum wave functions do not collapse but rather physical interactions and observations split the universe into disjoint universes (which means that the universe or rather universes are constantly subdividing), with one universe for each possible outcome of an interaction or an observation. If we accept this interpretation of quantum mechanics then the SAP will be tautologically true.
Frank Tipler has proposed a fourth anthropic principle, the final anthropic principle (FAP) which hypothesizes that information processing can continue indefinitely in the universe.
The anthropic principles, especially PAP and FAP seem to have an idealist character.
Jim Farmelant
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