Morat

Isn't this a prediction of string theory? Relativity wouldn't go bye-bye anymore than Newton did. String theory encompasses relativity.

Demosthenes

and plus the relativity didn't deduce that the speed of light was a constant, it assumed that. If the constant is changing, it would change the results generated by the theory but I doubt that it'll radically affect the framework.

Ought Naught

I didn't have any trouble accessing the paper. It's a very brief communication, but I really don't have the background to relate their arguments properly.

<a href="http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v418/n6898/full/418602a_fs.html&content_filetype=pdf" target="_blank">Here's the PDF for subscribers</a>

strubenuff

Where does string theory state the light of spreed was orginally close to infinitity, and then leveled off?

Morat

I think string theory predicted a change in the fine structure constant in the early universe. Evidence of that was announced several months ago (with similiar threads popping up here). However, a change in the fine structure constant would require either the speed of light vary or the strength of the electromagnetic force would vary.

This paper supposedly rules out a change in the strength of the EM force, making a shift in the speed of light the culprit.

That's if I'm synthesizing this correctly based on the stuff I read months ago.

So, to sum up: String theory predicted that the fine structure constant would have been different in the early universe (or so I recall hearing). Evidence of that was found, but it was unknown whether this change was because of the speed of light changing, or EM strength. Several months later, these guys show (by demonstrating that changing the EM strength would savagley break the 2nd Law in certain cases), that the speed of light shifting was the culprit.

Starboy

This is hard to swallow. The Balmer series, which predicts the spectrum of hydrogen has a term that includes c. If c were changing over time wouldn't the hydrogen spectrum change over time? Does this paper have anything to say about that?

Starboy

Friar Bellows

But isn't that part of their point? I mean, if c does vary, then redshift wouldn't correlate so simply with distance. You'd have to somehow include the effect of a varying c. Err, I think.

Starboy

Yes but as far as I know, there is no change in the spectrum of hydrogen with distance.

Oops, except the fine structure constant. Now I remember reading about this some time ago. Has this result been verified by anyone else?

Starboy

&lt;added the oops&gt;

[ August 08, 2002: Message edited by: Starboy ]</p>

beausoleil

I think the sequence of events was:

postulated variation in fine structure constant due to spectral shifts
-&gt; new 'demonstration' that it must be c that is varying.

Friar Bellows

How do you know that? Redshift.

How do you really know that? "Standard candles". I think supernovae (SN type 1a) are the standard candles that go out the furthest. Maybe the departures from linearity that we're seeing in the plot of redshift vs distance (the latter derived from SN1a standard candles) for high redshifts has something to do with a varying c? I dunno.

My point is that maybe we are seeing a "change in the spectrum of hydrogen with distance", but we're misinterpreting the data which could indicate this. Or maybe this effect is only detectable over cosmologically large distances. Once again, I dunno. I'll have to read their paper, so I can get confused even more.