From: Amara Graps (Amara.Graps@mpi-hd.mpg.de)
Date: Mon Aug 27 2001 - 10:00:41 MDT
Extropes,
Saw a message on sci.astro.research today that looks useful, so
then forwarding...
Amara
======================================================
Newsgroups: sci.astro.research
From: nedwright@my-deja.com (Ned Wright)
Subject: Variable constants?
Date: Sat, 25 Aug 2001 12:22:54 GMT
On 24 Aug 2001, NPR reported on the paper by Webb etal in the 27 Aug
2001 Physical Review Letters on variable physical constants. So I
have added the following commentary to the News of the Universe
section of my cosmology tutorial at
http://www.astro.ucla.edu/~wright/cosmolog.htm
http://www.usatoday.com/news/healthscience/science/astro/2001-08-15-speed-of-light.htm
In the 15 Aug 2001 USA Today reported on this paper
[http://xxx.lanl.gov/abs/astro-ph/0012539] that claims to have
seen a variation in the fine structure constant, alpha =
e^2/hbar*c. Since one of the factors in this dimensionless ratio
[=1/137.036...] is the speed of light, USA Today headlined the
idea that the speed of light might have varied. Coverage on the
first page of the Week in Review section of the 19 Aug 2001 New
York Times was more restrained. But John Bahcall of the IAS is
cautious about this result, and I also urge caution because of
several factors:
The measurement requires 1 part per million accuracy in
measuring the wavelength of absorption lines in faint quasars.
Averaging over 49 quasar absorption line systems gives only a 4
standard deviation result, which is barely statistically
significant.
Previous work [http://xxx.lanl.gov/abs/astro-ph/9803165] by the
same team also gave a 4 standard deviation result but with
larger errors. Thus improved accuracy did not give improved
statistical significance, but rather a smaller effect.
A similar measurement that compares the redshifted wavelength
of the 21 cm line of atomic hydrogen to redshifted wavelengths
of optical lines does not show this effect.
http://www.astro.ucla.edu/~wright/Dalpha.gif is a graph showing
the claimed detection of a variable alpha versus redshift as
the red points while the blue points show the 21 cm results
with no apparent variation in the physical constants. Of
course, this could be due to a compensating variation in the
proton magnetic moment.
--Edward L. (Ned) Wright, UCLA Professor of Physics and Astronomy
See http:www.astro.ucla.edu/~wright/cosmolog.htm
--
*******************************************************************
Amara Graps, PhD | Max-Planck-Institut fuer Kernphysik
Heidelberg Cosmic Dust Group | Saupfercheckweg 1
+49-6221-516-543 | 69117 Heidelberg, GERMANY
Amara.Graps@mpi-hd.mpg.de * http://galileo.mpi-hd.mpg.de/~graps
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