From: Mark Walker (mail@markalanwalker.com)
Date: Mon Jun 10 2002 - 13:25:27 MDT
----- Original Message -----
From: "Hal Finney" <hal@finney.org>
To: <extropians@extropy.org>
Sent: Monday, June 10, 2002 1:54 PM
Subject: Re: Practical Cosmology Symposium--Five Papers Now Online
> I haven't had a chance to read all of the papers, but I've looked at the
> first few paragraphs of some and skimmed others. Many of them discuss
> the Fermi paradox but they mostly take a curiously nearsighted view.
>
> The Fermi paradox seems to be generally expressed in galactic terms.
> Why hasn't our galaxy been taken over by aliens? With all the stars in
> the galaxy, surely one or more besides our own should hold intelligent
> life, which can then sweep through the galaxy in a million years or less.
> Nick's paper looks at the local supercluster and implicitly assumes
> that it is unoccupied.
>
> But really, the Fermi paradox is worse than this, in that it goes beyond
> one galaxy. What about all the other galaxies we can see? Are they
> devoid of intelligent life as well?
>
I agree with you Hal. I made this same discovery as I was researching my
contribution for the symposium. (How's that go? "Small minds think alike?)
Milan and I are thinking about co-authoring a paper on the subject. Below is
part of something I sent to SL4 on April 30th:
Relatedly, while writing this I realized that a small but illuminating paper
might be
written on the idea of a "Fermi Equation". The idea of course is an equation
like the "Drake Equation" but with a difference. Here is a very rough stab
at it:
The Fermi Equation
N = N* fp ne fl fi fm fd
N: The number of civilizations that launch spaceships (or probes) that reach
Earth by
April 2002.
N*: Number of stars that our within traveling distance of the earth. (See
below)).
fp: represents the fraction of stars that have planets around them.
ne: represents the number of planets per star that are capable of sustaining
life.
fl is the fraction of planets in ne where life evolves
fi is the fraction of fl where intelligent life evolves
fm is the fraction of fi that have the technical means to launch spaceships
capable of reaching earth.
fd is fraction of fm that have the desire to launch spaceships to reach
earth.
Where are the colonizers, the explorers, and the solarformers? An answer to
this must invoke a bottleneck explanation. Somewhere in the evolution of
inorganic matter to a technologically advanced civilization there is at
least one bottleneck that is not immediately obvious, for if it were obvious
there would be no Fermi Paradox. (See Brin's "The Great Silence" and R.
Hanson's "The Great Filter"). Bottlenecks can be broken down into one of
the parameters of the Fermi Equation. The bottleneck then will be
attributable to an associated science. For convenience sake we will use
three divisions: The natural sciences (physics, chemistry, and cosmology,),
the biological sciences (botany, zoology, genetics, etc.) and the social
sciences (economics, psychology, sociology). Let us then look at each of the
variables:
N = 0 We have not been visited by aliens.
N* = Number of stars that our within traveling distance of the earth. (See
below)
fp Clearly a bottleneck could be attributable to a lack of planets available
for life to develop on. The discovery of a number of large planets has
assuaged fears that solar systems with planets might be a rarity.
Ne: It is obviously possible that a significant bottleneck may be discovered
here at some point, for example, many of the planets that have been
discovered thus far are large and in close orbits to their suns suggesting
that it might be difficult for earth-sized e planets to establish themselves
in the appropriate orbital radius. However, nothing so far says that we
should expect that fp is zero, indeed, quite the opposite.
fl: the process of getting life started is very difficult (blame it on
biology)
fi: the process of getting intelligence started is very difficult. (blame
it on psychology)
fm: the technical means to master space travel is much harder than it looks,
or there is a Galactic club that forbids travel to undeveloped planets like
earth. (Blame it on sociology).
fd: Perhaps many species have the means to travel to earth but none have the
desire. (Economics? Sociology? Psychology?)
Re: N* Originally [I was] thinking of just
following
Tipler in his paper on the Fermi paradox to get the numbers for N* but I
realized that Tipler made a huge
assumption in limiting N* the stars of this galaxy, about 200 billion.
Tipler calculates very
conservatively that it would take 300 million years to colonize the entire
galaxy. But what is to say that there cannot be intergalactic travel? If we
figure that older civilizations might have had say a five billion year head
start then N* must be "astronomical" (as it were) in size. To figure it out
we would
need an estimate of a reasonable maximum speed that a spaceship (or one of
Tipler's Von Neumann probes) could travel. Whatever N* turns out to be it
will be huge, which means that
at least one of the other variables in the Fermi equation must be pretty
small indeed. The problem of course is the "just one problem". It would take
only a single civilization to pass through the bottle neck and colonize the
universe (given enough time). I think that our universe is still a "buyers
market" should seem as perplexing as if one discovered life on a planet
(like ours) confined to a single continent.
Mark
Dr. Mark Walker
Research Associate (Philosophy), Trinity College, University of Toronto
Editor-in-Chief, Journal of Evolution and Technology,
(www.transhumanist.com)
Editor-in-Chief, Transhumanity, (www.transhumanism.com)
Home page: http://www.markalanwalker.com
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