[ExI] BICEP2 and the Fermi paradox

Rafal Smigrodzki rafal.smigrodzki at gmail.com
Tue Apr 1 04:54:34 UTC 2014

On Mon, Mar 31, 2014 at 6:46 PM, Alfio Puglisi <alfio.puglisi at gmail.com>wrote:

> After all the news about BICEP2's  (indirect) detection of gravitational
> waves produced by inflation, I was pointed by someone to this paper by Alan
> Guth, one of the fathers of inflationary theory:
> http://arxiv.org/PS_cache/hep-th/pdf/0702/0702178v1.pdf
> it goes something like this: if the eternal inflation hypotesis is true,
> the entire cosmos is undergoing continuous inflation, which gives birth to
> "ordinary" universes here and there. But since this is inflation, every
> second there is more room by a crazy factor like 10^37, and so each second
> 10^37 more universes are produced than the second before.
> Now, consider one of those universes. At a certain point, a first
> space-faring civilization may develop. As that universe gets a little
> older, it might develop a second one. But, older universes are vastly
> outnumbered by younger ones (by a factor of 10^37 for each second of
> difference), so a civilization picked up at random will almost always find
> itself in one of the youngest universes that permits its existance, and
> with no second civilization in sight.
> I am not sure that I got all of that correctly :-) It does make sense in a
> crazy way, with that biiiig assumption about the eternal inflation, which
> of course is unobservable as far as I know.

### A few years ago on this list I used this very argument against Nick
Bostrom's anthropic argument in favor of us being in a simulation -
although at that time inflation was more of a hypothesis rather than a
theory slouching towards becoming a fact, as it is doing today. There are
so may more young civilizations than older ones that no matter how popular
ancestor simulations are, you are vanishingly unlikely to be in one of

Also, inflation lifts the anthropic curse of doom - when young
civilizations are so frequently generated, sentients in these young
civilizations vastly outnumber sentients in old civilizations, even if each
old civ has orders of magnitude more members. So, there is no need to
invoke the great filter between us, a young civilization, and our
Hubble-spanning descendants.

And yes, it does seem to me that the Fermi paradox disappears as well in an
inflationary universe.

Interestingly, I came across an article where Baptists hail BICEP and
inflation as yet another proof of their god's existence. This flummoxed me
somewhat, I must admit.

Long live inflation!

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