Re: The size of the universe <= 14E+9 light years
- From: Friar Broccoli <EliasRK@xxxxxxxxx>
- Date: Sun, 30 Sep 2007 22:23:30 -0000
On Sep 30, 10:38 am, josephus <dogb...@xxxxxxxxxxxxx> wrote:
[snipping preceding conversation]
ok how do you explain the relationship between recession and distance.
the velocity increases with distance. this does not mean our
fundamental measures are expanding but dopler effects are demonstrable
on the local level as well.
I'm not going to touch the "recessional velocity" question
because I am still as confused as hell by the claim that the
expansion rate cannot be interpreted as (an effective) velocity.
(For a few minutes I thought I understood but have changed my
mind repeatedly since then.)
However redshift vs distance can be explained without reference
to any velocities, and is perhaps best understood without it.
Basically, as light leaves a distant galaxy it is travelling
through expanding space. As light travels through such
expanding space it is stretched so the light waves become longer
and thus less energetic. This is called redshifting.
The more time (or farther) light spends traveling through
expanding space the more it is stretched, thus more distant
objects appear more redshifted than nearby ones.
In other words "recessional velocity" is not the only thing that
can cause redshift. In addition to expanding space, a strong
gravitational field can also cause redshift.
You may be asking yourself if "recessional velocity" and
expanding space aren't two aspects of exactly the same thing.
Almost certainly not, because light from a rapidly receding
object is immediately stretched relative to us the observer;
while light from a distant galaxy is gradually stretched over an
extended period of time.
Robert Keith Elias, Quebec, Canada Email: EliasRK (of) gmail * com
Best programmer's & all purpose text editor: http://www.semware.com
--------- I consider ALL arguments in support of my views ---------
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