Re: Diameter of CMBR shell?
- From: "George Dishman" <george@xxxxxxxxxxxxxxxxx>
- Date: Fri, 16 Jun 2006 16:47:00 +0100
"Jeff Root" <jeff5@xxxxxxxxxxxx> wrote in message
news:1147866501.834470.101640@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
George Dishman replied to Jeff Root:
What was the diameter of the shell of ions-n-atoms from
which was emitted the light we currently see as the cosmic
microwave background radiation?
Diameter when it was emitted or diameter now?
I worded my question pretty carefully, and it still looks okay
to me. I said "was". Past tense. The light-emitting shell is
long gone, though of course the atoms are still there so it
would be an interesting trivia question to also ask how big
that shell might be now.
http://www.astro.ucla.edu/~wright/CosmoCalc.html
The redshift of the material is 1089 (IIRC) from WMAP.
Enter that and click 'flat'. The Hubble distance is
given as:
13995.2 Mpc or 45.647 Gly.
That's the radius of the shell "now". If anyone doesn't
understand what "Hubble distance" and "now" mean, read
this:
http://www.astro.ucla.edu/~wright/cosmo_02.htm#DH
Since z is also a measure of the change of scale factor,
the Hubble distance radius "then" is 13995.2 = 12.85 MPc.
I'll add another question: Some years ago I was told that
the optical thickness of the shell was about 100 parsecs.
Is that still a good figure?
I don't have any info on that.
George
.
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