RE: speed of light

This thread may have drifted beyond hope of returning to something

vaguely related to radiation protection (or at least the subject

header), but I will try.

The question of whether the speed of light in vacuum has changed over

cosmological time has significance for several cosmological models, in

part because of its relationship to the fine structure constant. In the

Standard Model the fine structure constant is one of five parameters

primarily determining the structure of the known universe (from nucleons

to galaxies). Last year some astronomers claimed they had evidence the

fine structure constant has increased slightly (10^-5) over the last 10

billion yrs.

Though small this change is near an upper limit set from another study

(A.I. Shlyakhter, Nature 264 (1976) 340), recently refined by Iwamoto et

al. (wwwndc.tokai.jaeri.go.jp/nds/proceedings/2000/o13.pdf), that uses

the long-lived samarium isotopic data from the Oklo (Africa) site, where

naturally occurring nuclear fission reactors operated some two billion

years ago (before radiation protection regulations were promulgated).

Any significant difference in the fine structure constant back then at

Oklo would have changed the neutron capture cross section resonances for

each isotope (compared to today's values) and produced a calculated

isotopic ratio different from the measured ratio value.

Rick

Richard G. Strickert, Ph.D.

Principal Scientist

Signature Science LLC

8329 North Mopac Blvd.

Austin, TX 78759

(512) 533-2009 (Phone)

(512) 533-9563 (Fax)

rstrickert@signaturescience.com

http://www.signaturescience.com

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