MadSci Network: Astronomy
Query:

Re: is the universe smaller the further we look?

Date: Sun Sep 12 19:05:26 1999
Posted By: Brian Kane, Post-doc/Fellow, Astronomy, AstroPlace, Inc.
Area of science: Astronomy
ID: 935269654.As
Message:

It depends on what you mean by distortions: the overall curvature of space, or the distortions caused by variations in the density of matter?

If the former, yes, the observable universe is smaller, the farther we look back, to the remote past --- because it is denser. However, we can't see far enough back in time and out into distant space to directly detect a noticeable distortion of space-time (other than the ubiquitous red shifts). Indirectly, we notice that the curvature of spacetime at very early epochs is likely influencing how much light we see coming from young galaxies, but there is enough uncertainty that is not yet possible to infer the curvature of space at that epoch.

If the latter, the Big Bang theory its remnant distortions from hyperinflation *were* detected in the past few years by the Cosmic Backround Explorer (COBE) satellite, which mapped the sky in microwaves and found very subtle (one part in one hundred thousand) differences in background temperature.

[Moderator's Note:
In theory we could use the distortion of spacetime at large redshift to measure whether we live in an open or closed universe. In practice, however, this is an extremely difficult problem. For a rather technical explanation of this, please see the Many Distances section of Ned Wright's Cosmology tutorial.

Jim O'Donnell, jim@penfold0.demon.co.uk ]


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