Re: accelerating universe and Leslie constraints

Michael S. Lorrey (
Fri, 26 Mar 1999 10:16:14 -0500

Damien Broderick wrote:

> Some time ago we had a discussion on the Doomsday arguments advanced by
> John Leslie and others. This spills over into anthropic cosmology, the
> Great Filter, etc. The Guardian published an account recently of a paper
> (posted on the Net) by Lawrence Krauss and Glenn Starkman, both of Case
> Western Reserve U., that the newly discovered acceleration of the
> observable universe implies a light-cone horizon that will isolate our
> local cluster some 100 billion years from now. The farthest galaxies will
> start to be carried away faster than light some 15 billion years hence.
> I wonder what impact this has on the Leslie argument?

So the Guardian thinks matter can travel faster than light? Whoever wrote that is mistaken. The 'accelertion' in the expansion rate manifests itself in an increase in mass and emission wavelength. A better question is that if this expansion accleration is in fact true, this means the mass of the universe will increase as the expansion rate increases, due to relativistic effects. At what point will the expansion speed be high enough to make the mass of the universe great enough to contract again? Or is it a diverging function?

> Indeed, I wonder if it has any salience to the traditional explanation for
> Olber's paradox. Might the universe be eternal after all, except for
> bubbles like our own that are observable only under (somewhat) anthropic
> conditions?

If the universe were eternal, we would have infinitely bright starscapes. We do not, so it is not.

Mike Lorrey