Re: against UD+ASSA, part 1

From: Russell Standish <>
Date: Fri, 28 Sep 2007 09:39:47 +1000

On Thu, Sep 27, 2007 at 12:06:42PM -0000, wrote:
> OK, new thought experiement. ;)
> Barring a global disaster which wiped out all of the humanity or its
> descendents, there would exist massively more observers in the future
> than currently exist.
> But you (as an observer) find you born amongst the earliest humans.
> Since barring global disaster there will be massively more observers
> in the future, why did you find yourself born so early? Surely your
> probability of being born in the future (where there are far more
> observers) was much much higher than your chances of being born so
> early among a far smaller pool of observers?
> The conclusion appears to be that there is an overwhelming probability
> that we are on the brink of some global disaster which will wipe out
> all humanity, since that would explain why we don't find ourselves
> among the pool of future observers (because there are none).
> Is the conclusion correct?

This is the standard Doomsday argument, which has been well
discussed. In this case, "disaster" just means population decline. A
world population decline to say 1 billion over the next couple of
centuries, with a slower decline after that is probably enough to
ensure the SSA predicts a near peak population observation. Although I
haven't done the maths on this one - I did it on assuming current
exponential growth continues, how long have we got until the crash,
and it's less than 100 years, so we can say there must be a population
decline of some sort before then (assuming validity of the DA).

The only other historical time the Doosmday Argument predicts
"disaster" before our current time was during the Golden Age of
ancient Greece. And, sure enough, there was a significant population
decline around 200 BCE. This is in appendix B of my book - I really
must get around to writing this up as a peer reviewed article though.


A/Prof Russell Standish Phone 0425 253119 (mobile)

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Received on Thu Sep 27 2007 - 20:56:07 PDT

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