archive: Re: SETI RE: [ASTRO] BIG bang question

Re: SETI RE: [ASTRO] BIG bang question

jerry and judy ( jerbidoc@zianet.com )
Sat, 17 Oct 1998 16:20:07 -0600

>In a message dated 10/17/98 2:30:45 PM Eastern Daylight Time,
>jerbidoc@zianet.com writes:
>
>> from S. Hawking (paraphrased)
>> If the initial density of the universe, one second after the Big Bang, had
>> been greater by one part in a thousand billion, it would have recollapsed
>> after only ten years.
>> Conversely, if the speed of expansion one second after the Big Bang had
>> been larger by one part in a hundred thousand million million the Universe
>> would be so expanded by now that we would not even be able to observe any
>> other galaxy that was not gravitationally bound to our own Local Group.
>> (Very few galaxies probably would have formed!) With only the slightest
>> decrease in its initial density, the universe would have been virtually
>> empty by the time it was ten years old. With little chance for complexity
>> to arise.
>
>I would like to know Steven Hawkings reasons for believing these things to be
>true. But if they are true, and I would tend to believe Steven Hawking even
>though I would probably struggle with the logic, then this implies that there
>is some reason the universe has exactly this much matter and expansion.
>Otherwise, why the exact right amount?

Sorry, I've read the reason why an early intense inflationary period would
automatically cause the rate of expansion to become very close to the
critical rate, no matter what its initial energy density, but I can't
recall how to explain it. I remember it's got something to do with the
homogeneity problem and the speed of light in a tennis ball-sized universe,
but that's not a lot of help. Anyway, it seems all 'size' universes will
'oscillate' eternally. (smile)

> And further reasoning would then argue
>against a closed universe, because there must be some reason it came out this
>way.

I don't follow that. Oh, because a perfectly balanced universe would be so
unlikely?

Yeah, it would seem so if the universe followed macro-world logic. The
obvious difference between a contracting universe and a black hole is the
"bounce" and the way I understand it (on a good day) is that the false
vacuum state, during the extreme conditions of superunification and quantum
gravity, causes the super-inflation, which doesn't happen even in
super-massive BHs (we're lucky it doesn't!). So the inflationary episode
results from this energetic reversal and the universe's initial expansion
rate is a 'calibrated' result of its own initial conditions and
consequently everything's perfectly balanced. This all happens long before
the first second, IIRC, while the size of the baby universe is still
"manageable". (grin)

>John Marcus MD
>KE3SW

Jerry