Re: adapting to an open universe

Warrl kyree Tale'sedrin (
Sun, 18 Jan 1998 16:49:41 +0000

> From: Damien Broderick <>

> At 05:05 PM 1/18/98 +0000, Nick Bostrom wrote:
> >if d is big enough, then by the time the probes have traveled 10% of
> >the way, the remaining 90% will have grown larger than the original
> >100%, due to the expansion of space inbetween. So if that expansion
> >rate settles down to a constant, then there must be a sphere centered
> >around Earth such that nothing that is outside of that sphere can
> >*ever* affect Earth, even if it travels with the speed of light.
> I believe you have just reinvented the canonical explanation for Olbers'
> Paradox.

We can also use this to set bounds on the expansion rate. The
diameter of the sphere is set by the expansion rate, and we can (by
definition) observe the edges of the observable universe, but nothing
beyond those edges.

What's the current estimate of the diameter of the observable
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