(Radi Khrapko) wrote in
om:


An answer to the Fermi's question, `Where are they?', is
presented. The answer is: we are alone because our Universe
is bad for a civilization. The combination of physical constants
does not need to be more fine tuned than is necessary to permit
one civilization and, since extreme fine tuning of the constants
is a very unlikely event, it is most likely that our Universe is
just good enough to permit development of only one
civilization. The alternative anthropic principle can be
formulated as follows: `It is most likely to observe a universe
in which civilized life is an extremely rare phenomenon.'

Astronomical and Astrophysical Transactions 22 (2003) 847-850

This is an interesting idea, but the answer is far from obvious. Assume
that there are 100 universes where intelligent life is so unlikely to occur
that it only happens on one place and 1 universe where it is a bit more
likely so it exist on 900 planets. Then there is 90% probability that we
live in the last one, even if most of the universes where life can occur
are more hostile.

By observing how common life is we may then draw some conclusion about
exactly how sensitive the parameters are that control the likelyhood of
life in the universe, although obviously statistics based on a single
sample is chancy.