Too big for the universe

[DarkProtoman]

What if the universe was a sphere w/ a radius of 100'? What would
happen if let's say, that universe was once the size of ours, but
RAPIDLY shrunk, and there was a city in that universe. What would
happen when the universe got too small for them? What would the city's
inhabitants experience during the universe's shrinkage? I've always
wondered about this. Thanks!!!!!!!!

[DaveC426913]

There's a Star Trek Next Gen episode that deals with this. Crusher finds herself in a pocket universe. This is one of my fave eps.

"Computer, what are the dimensions of the known universe?"
"The known universe is a sphere, 700 metres in diameter. Correction, 600 metres. Correction, 500 metres..."
*Boom*
"Computer, what was that noise?"
"Explosive decompression on decks A through E."
"Cause?"
"There are no airtight bulkheads forward of section 27."
How can that be?
"An apparent design flaw. The Enterprise is larger than the known universe. 400 metres. 300 metres..."

I love that last line...




Anyway, of course this is not how it would happen.
Consider all the events that precede "The Big Crunch".
Stars crashing into each other as they crowd together, galaxies crashing into each other. You city would be vapourized by supernovae long before it exerienced any discomfort from a shrinking universe. As compression caused the temperature to skyrocket, the atoms that made up its matter would become plasma, then atoms would degenerate to pure energy, etc.

[Oh No]

Thus spake DarkProtoman <Protoman2050@gmail.com>
>What if the universe was a sphere w/ a radius of 100'? What would
>happen if let's say, that universe was once the size of ours, but
>RAPIDLY shrunk, and there was a city in that universe. What would
>happen when the universe got too small for them? What would the city's
>inhabitants experience during the universe's shrinkage? I've always
>wondered about this. Thanks!!!!!!!!
>
As the universe collapses and everything falls in on itself, everything
heats up, like the air heats up in a bicycle pump when you compress it.
The inhabitants would get vaporised long before they get crushed. In
practice, in an expanding universe, we will die of cold long before the
universe starts to collapse.

Regards

--
Charles Francis
substitute charles for NotI to email

[paul.valletta@ntlworld.com]

What the question is reasoning is that:

http://www.site.uottawa.ca:4321/astronomy/index.html#exponentialexpansion

or contraction, is an anology of the space/balloon?

[Henning Makholm]

Scripsit "DarkProtoman" <Protoman2050@gmail.com>

> What if the universe was a sphere w/ a radius of 100'? What would
> happen if let's say, that universe was once the size of ours, but
> RAPIDLY shrunk, and there was a city in that universe. What would
> happen when the universe got too small for them?

According to GR, universes simply _don't_ suddenly and rapidly shrink
without warning, so any answer must be higly speculative.

The most reasonable answer would be that the inhabitants of the city
would observe that _all the other matter_ in the universe suddenly
started moving roughly towards them at a speed very close to c. After
the first direct hit by a relativistically moving star, the city's
inhabitants would be beyond caring about the rest of the story, having
been ripped into plasma by the impact.

It is also possible, I would guess even probable, depending on the
particulars of the magic that makes the universe suddenly contract,
that before a star hits Earth the sky will start glowing with
ultra-blueshifted starlight, frying the city to radioactive cinders
before any heavy matter hits it.

Either way, by the time the geometry of space starts to diverge
significantly from Euclidean on a planetary scale there would not be
any solid matter left to notice it anyway.


But those answers probably sidestep the question you wanted to ask, so
let us instead imagine the city being on a planet that sits in an
otherwise empty contracting universe with positive curvature. In that
case the eventual demise of the city ought to look approximately as if
the ground around it started to rise. The inhabitants would (briefly)
find themselves living not on the outside of a sphere, but on the
inside of a shrinking, kind of spherical, void in a rock-filled
universe. There would be hyper-earthquakes as a constant amount of
planetary crust and mantle tried to share the rapidly shrinking
surface of the void. If you managed to stay on top, the antipodes
would eventually crunch into you from above.

--
Henning Makholm "De er da bare dumme. Det skal du bare sige til dem."

[Uncle Al]

DarkProtoman wrote:
>
> What if the universe was a sphere w/ a radius of 100'? What would
> happen if let's say, that universe was once the size of ours, but
> RAPIDLY shrunk, and there was a city in that universe. What would
> happen when the universe got too small for them? What would the city's
> inhabitants experience during the universe's shrinkage? I've always
> wondered about this. Thanks!!!!!!!!

Adiabatic heating. Cosmic background radiation would be bummer as
would the Schwarzschild radius crunch.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf