A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » Research
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Cosmology



 
 
Thread Tools Display Modes
  #1  
Old July 2nd 03, 04:52 PM
AMMS716
external usenet poster
 
Posts: n/a
Default Cosmology

Hello All,

Please reduce my level of ignorance. I am not a physicist, but I am a
mathematician. (number theorist). I can deal with tensors. And Riemann
surfaces.
I have several questions.

(1) Apparently, recent supernova observations have lead to the conclusion that
omega = 1. I do not see why this must lead to the conclusion that the (topology
of) the universe is necessarily Euclidean. Can't it be Elliptic (i.e.
positively curved )
yet still forever expanding with omega = 1? One obvious way to prove that it
is
Euclidean is to show that the angles in a triangle add to exactly Pi. However,
we can't possibly have sufficiently accurate observations to verify this. Or
can we?

(2) Let us assume it is Euclidean. How do we know that the observable
universe is NOT the entire universe? Theoretical models may suggest an
infinite
universe, but there is no way EVER to confirm it by observation. And from a
practical point of view, if something can NEVER be observed, than it doesn't
really
exist.

(3) If the universe is Euclidean and infinite, how is this possible? The
universe
is a finite age and the speed of light is finite. There simply hasn't been
enough
time for it to expand to infinity. Furthermore, inflation does not seem to
provide
for an infinite universe either, for even a sudden (finite) period of
exponential
expansion in the very early universe does not lead to an infinite one.
How do we know (or how CAN we know) that the Universe is not Euclidean and
bounded? How do we know that Mach's principle must apply at a point in space
13 billion LY away? How can we know that at an observer there sees that in
some directions there are no stars? (because beyond the boundary there is
literally nothing)

Bob Silverman


[[Mod. note --
Ed Wright's Cosmology FAQ,
http://www.astro.ucla.edu/~wright/cosmology_faq.html
gives a nice general introduction to cosmology, and would probably
provide insight into (3), and possibly also (1) and (2).
-- jt]]
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Breakthrough in Cosmology Kazmer Ujvarosy Space Shuttle 3 May 22nd 04 09:07 AM
Breakthrough in Cosmology Kazmer Ujvarosy Astronomy Misc 3 May 22nd 04 08:07 AM
Breakthrough in Cosmology Kazmer Ujvarosy Space Station 0 May 21st 04 08:02 AM
Breakthrough in Cosmology Kazmer Ujvarosy Policy 0 May 21st 04 08:00 AM
Cosmology insanity Powdered Toast Man Amateur Astronomy 26 July 14th 03 05:26 PM


All times are GMT +1. The time now is 05:44 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.