Re: Fermi Paradox in the news

From: Michael S. Lorrey (
Date: Tue Oct 24 2000 - 23:39:23 MDT

Nick Bostrom wrote:
> Oh yes, the second data point would make a helluva difference! The problem
> with the one data point we have is that because of observational selection
> effects it doesn't tell us much. No matter how small a fraction of all
> planets in our infinite universe develop life, we would by necessity find
> that we originate from one of the exceptional ones that did. So this data
> point is predicted equally well (i.e. has a conditional probability of one)
> given any theory that says that intelligent life would develop somewhere.
> But finding a second source of intelligent life, in our relative vicinity,
> would dramatically boost the support for those theories which say that
> intelligent life is common. (My PhD thesis at
> has more on this and many other
> related topics.)

I'm enjoying your thesis immensely, Nick. I'm currently in Chapter 2, regarding
Hackings mistake with the Inverse Gambler's Fallacy as applied to Wheeler type
universes. I don't notice that you've accounted for the fact that Wheeler
universes, in depending on being able to collapse again to generate the next
iteration, exclude the set of possible open ended universes (which our own seems
to be), and thus is a Self Selected set. In your variable example of the
expansion rate, a Wheeler Universe dictates a maximum limit to the expansion
rate as a precondition of its being a Wheeler Universe.

You then go on to White and Dowe's analysis to decribe the other error of the
IGF, the assumption that the fact that this universe is fine tuned implies that
many other universes exist in the ensemble multiverse, when the odds are the
same for every individual toss of the die, irrespective of the number or results
of previous tosses. The thing is that if the odds of any given toss being double
sixes is 1 in 36, then if there have been 36 tosses, the odds that at least one
such toss is double sixes approaches unity.

Likewise, given a plenum of possible values of tunable criteria, and the degree
of precision required to acheive a 'tuned' universe in any given toss, the more
tosses there are increases the odds that there is at least one such tuned
universe among the ensemble. However White objects to the supposition that that
one such tuned universe is the one we happen to be in as a result of that
tossing. Your demolition of this argument in respect to life bearing universes
due to the IF..THEN..ELSE nature of quantum mechanics is rather good, but may or
may not apply to the present case of intelligent species on other worlds within
this universe. I initially think its safe to assume that most all, if not all,
selection criteria for intelligent life developing on any given planet occur
long after an intelligent life bearing planety in one star system has had any
significant effect on another in another star system (however this is where we
begin to collide with the Fermi Paradox, depending on the propability of
intelligent technological space faring life in any given light year range versus
their racial/cultural life expectancy (i.e. racial death or other ending like a
technological singularity)).

If space travelers do influence the selection criteria for other worlds or not
is a point of potential information transfer, and thus, selection. Because the
odds are low that any given spacefaring race would be developmentally parallel
to any other race at any range of proximity, and thus that any given point of
selection in our own development could have been, or could have been interrupted
by a spacefaring race visiting our planet (of which we have no evidence to
support), from the prokaryotic shift onward, we can infer that not only is there
a limit on the rate at which a space faring race can spread, but a time limit on
how long any given space faring race retains either or both any interest or
reason to be involved with terrestrial type worlds, as well as any means of
embodiment by which a more primitive race would recognise groups and/or
individual members of such races (and their impact upon the surrounding
universe) as a sign of intelligence (as well as other possible limitations).
These possible obervational selection effects thus not only determine why life
exists in this universe, but why one life form has not overrun the universe
previously, that the selection criteria that remove them from the stage are
mandated in order for us to exist to observe this universe.

These alternative explanations to the Fermi Paradox have been hashed out here
time and again in various forms, but I do enjoy your much more formal treatment
of the subject. Your demolition of White does seem to be supported by M Theory,
which explains six possible classes of universes, one of which our own universe
belongs to.

Now, in a tuned universe that is hospitible to the development of life, to use
your delineation between surprising outcomes and improbable but unsurprising
outcomes, we need to decide which is which: Is the existence and evidence of
only one intelligent species in x cubic light years of space surprising, or
improbable but unsurprising? If it is the first, then Fermi's Paradox is a
problem. If it is the second, then Fermi's Paradox is not.

Mike Lorrey
"No matter where you find yourself, there you are."
                                - Buckaroo Banzai
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