Re: Cold and Dark?
Mon, 25 Oct 1999 09:25:20 -0700

Anders Sandberg, <>, writes:
> I read the Krauss and Starkman paper "Life, The Universe, and Nothing:
> Life and Death in an Ever-Expanding Universe" (astro-ph/9902189) and
> it is really bad news.

This is bad news, but as far as I am concerned it is gilding the lily. Tipler has already argued very convincingly that life is impossible in an open universe. From page 139 of Physics of Immortality:

: As I discussed in Chapter III, Freeman Dyson pointed out that, although
: the energy is available in open and flat universes, the information
: processing must be carried out over larger and larger proper volumes.
: This fact ultimately makes impossible any communication between opposite
: sides of the 'living' region in a flat universe, because the redshift
: implies that arbitrarily large amounts of energy must be used to signal,
: and Dyson showed that only a finite amount of energy is availble.
: On the other hand, open universes expand so fast in the far future that
: it becomes impossible for structures to form of sufficiently larger and
: larger size to store a diverging amount of information.

This is very similar to the horizon argument of Krauss and Starkman. Frankly I think it is sloppy that they have not referenced Tipler in their paper. It looks to me like he has anticipated the thrust of their arguments, although not all the details. Hopefully before journal publication the referees will force some revisions and acknowledgement.

> So it seems that Tipler (expanding universe rather than big crunch)
> and Dyson (infinite survival in open universe) are out.

I don't rule out Tipler so quickly. The universe has only appeared open for a couple of years. Some people live in places where they say, if you don't like the weather, wait a few minutes and you'll get something new. Science on the frontiers works much the same way. Chances are in twenty years we'll have gone through a couple of revisions of our picture of the large scale nature of the universe.

> Fortunately we
> have a third candidate for transcendence, Linde. What if we can escape
> to other regions of the universe or make baby universes?

Tipler also analyzes this case and concludes that only a limited amount of information can be shoved into the baby universe, as in the other paper you mention. What is it with these guys, are they boycotting Tipler because he dared to mention God?

> Overall, the outlook is rather gloomy, but (you knew I couldn't
> possibly end on a low note) there are some hopeful possibilities. One
> could imagine using the matter collection scenario of Krauss and
> Starkmann to make a number of huge black holes in which to escape into
> new inflation regions using negative energy densities. Some of these
> will likely have better values of the cosmological constant or at
> least ones closer to zero - this way one could construct a Dyson-Linde
> scenario, with possible offshoots into the Tipler scenario if
> descendant civilizations happen to find themselves in closed
> universes.

This sounds like one loophole which Tipler did not consider, the possibility that a baby universe might be closed where the parent universe was open. I don't know if that is cosmologically possible but if so it could be an out.

> Perhaps the most optimistic thing about these two papers is not their
> conclusions, but the fact that physical eschatology and the effects
> intelligent life can have on the universe are not being increasingly
> studied by physicists. It is hardly a mainstream topic, but it is no
> longer utterly beyond the pale.

Hopefully they will eventually take the time to see what has been done before.