Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] cosmology



-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu
[mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf
Of John Denker
Sent: Sunday, September 09, 2007 9:42 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] cosmology

On 09/09/2007 08:31 AM, Jeffrey Schnick wrote:
What
does it even mean to say that the universe was the size of an atom?

It may or may not mean anything.

Often such things are said without much regard to whether
they mean anything or not.

1) If the universe is closed, then it has a well-defined size.


Would a measure of that size be the distance measured along a straight
line from a given point in space back to that same point in space?

I think of "closed" as meaning that the density of the universe will not
continue decreasing forever but that at some future time the density
will stop decreasing and start increasing and continue increasing until
it is again infinite. How does this necessarily imply that the universe
is of finite size?