On 30 Jul, 15:42, Joe Strout wrote:

On the lack of observed alien civilization, we need to remember that
the universe is still pretty young. Sure, 13 billion years sounds a
real lot, but remember if we subtract 3 billion years that leaves 10
billion. The point is, it?s taken life here about that time to evolve
intelligent life. While that might take shorter time ellsewhere, one
has to remember that evolution of life from bacteria is not simple and
unlikelly to take a short time.

This is missing the point. The time from the beginning of the Universe,
to the formation of a technological civilization, should take the form
of a normal distribution (i.e. bell curve), as pretty much any other
natural process does, due to the central limit theorem. If our
civilization is average (i.e. by the Copernican principle), then the
mean of this distribution is somewhere around the present. That means
that about half of the civilizations that will ever arise, arose before
us; and half will arise after us.

You are indeed correct, but how do you know the distribution is
Copernican. Why not a race? A race to me seems eminanly logical but so
far nobody has commented on it. If a race is indeed true there are
consequences in terms of how we should act.

1) We need to know how close to us other civilizations are. We are
running 42km and we need to look back and see where the other
competitors are. A 1km telescope - figure admittedly pluced out of the
air.

2) We do need to build interstellar VN probes. This to an extent
represents the tape.

Now, we don't know what the standard deviation of this distribution is,
but we can make some guesses by looking at our history. How tightly
constrained was the development of civilization just now, given our 4.5
GY history? The answer appears to be, not very. Some really pivotal
moments in evolution, like the CretaceousTertiary extinction event, were
the result of highly random processes (a major impact event in this
case) which could have just as easily happened much sooner or later. So
the standard deviation is probably hundreds of millions of years at
least.

This is to some extent of the nature of a BTW. Genetic markers on
mammalian species show that the main mammal types evolved in the early
to middle Cretaceous. Fossils BTW are quite rare because fossilization
is a rare process. Genetic markers are in fact better in showing when
Evolution took place.

Thus the Cretacious/Teriary extinction was less relevant than has been
supposed up to now.

But with a standard deviation that high, and given that there are over
200 billion stars in the galaxy, there would necessarily be some
outliers to the population who happened to evolve very much earlier than
the rest of the population -- even at 3 sigma (standard deviations) away
from the mean, you'll find 0.37% of the population, which would be 540
million civilizations, half of which evolved earlier than the mean by
three sigma. Even if most of those stars can never support life, the
numbers (of both stars and years) is so large that it's very hard to
avoid the conclusion that the first civilization must almost certainly
arise a billion years or more before the mean.

How many competitors are running? Are we winning? Will we send an
interstellar probe in the equivalent of 2hr 6min?

This, combined with the observation that it takes only a few hundred
million years (after the development of space colonization) to settle
the whole galaxy, presents Fermi's paradox.

We need to send an interstellar probe in 2hr 6 min. If we don't .....

There are darn few parameters you can tweak in this analysis that make
much difference. The only escape I see is to assume that planets where
civilization can arise are very, VERY rare, so that the total population
size is not in the billions but perhaps in the thousands. Of course,
even with N=1000, there should be at least one civilization that
develops at least three sigma before the mean. So we have to further
assume that we are NOT an average observer, but are one of the first
civilizations to arise, maybe even the very first. Otherwise, we would
have arisen in an already-settled galaxy, and this does not appear to be
the case.

But of course, that makes a philosopher of science uncomfortable as
well. The odds of us, as a civilization, happening to be the first are
quite low.

In a race situation the odds are high. If we were not the first we
would all be Centurians. Alpha Centurians would have terraformed the
solar system, and we would be in a park on Earth ... if that.

Moreover, if there are eventually going to be many orders of
magnitude more people, spread throughout the galaxy and over millions or
billions of years, why do you and I happen to be born into this time,
when there are fewer than 10 billion of us, all cooped up on one planet,
and within a few hundred thousand years of the birth of civilization?
The odds against THAT boggle the mind.

The most logical explanation is that all civilizations, including ours,
destroy themselves (or are destroyed) before interstellar colonization
begins. But, despite the logic of it, I find I can't accept that. So,
I'm left befuddled, with no neat solution. I consider this one of the
great mysteries of our time, right up there with the nature of
consciousness.

What reason have you got for assuming that? A race is equally logical.
Anyway if you really do believe we are going to destroy ourselves you
are duty bound to try to do something about it.

Von Neumann said half jokingly that supernova explosions, which we now
know to be supermassive stars, were civilizations detonating the
ultimate doomsday machine.

Von Neumann was wrong in his applicarions of games theory. The world
is not polulated by rational, intelligent Machiavellians, it is
populated by rather stupid people who often do not see where their
best interests lie. The Middle East situation to take an example is
really a "stag hunt" where both participants would do far better to
cooperate, if only they would realize it.


- Ian Parker