# Re: Universe a black hole? Probably (Was: Re: evidence?)

From: Thomas Buckner (tcbevolver@yahoo.com)
Date: Sun Aug 26 2007 - 05:09:42 MDT

--- Jeff L Jones <jeff@spoonless.net> wrote:

> I get:
>
> mass of sun = 2*10^30 kg
> total energy in observable universe ~ 10^55 kg
> ~ 10^25 suns
> radius of observable universe = 78 billion
> lightyears = 7*10^23 km
> Schwarzschild radius of observable universe =
> 3*10^25 km
>
> So it looks like, just based on the usual
> linear scaling of
> Schwarzshild radius with mass, one would think
> our universe would be
> the current observable
> horizon. Interesting that they are so close
> (less than 2 orders of
> magnitudes away)... I'm not sure why.
>
> However, I don't think you can apply the usual
> relationship between
> mass and Schwarzschild radius to the universe
> as a whole. Several
> reasons I can thnk of why it probably shouldn't
> apply: 1.) we've
> measured the universe to be approximately
> flat... if it were a black
> hole, it should be highly curved, 2.) it's
> expanding, which makes the
> geometry different from a usual black hole, and
> 3.) the dark energy is
> exerting negative pressure (that is, outward
> pressure) which might be
> another way of understanding what's keeping it
> from collapsing into a
> black hole.
>
> I think the formula for calculating
> Schwarzschild radius in terms of
> mass is a useful rule of thumb, but you have to
> look at more than that
> to actually see if you get a real black hole.
>
> Jeff

You're probably right; in any case something
being the inside of a black hole implies spatial
regions outside, which may not apply here. We
simply don't know what's beyond the Hubble sphere
and we won't know pre-Singularity anyway.

Tom Buckner

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