Re: value of the Fine Structure Constant

Sorry for the delay in response, Paul.

The paper you pointed me towards is very interesting in what it is trying 
to achieve and its method of experimental detection.

I'll get straight to answering your question and then give some previso's 
afterwards.

From the paper, they give the value of (-2.2+/-5.1)x10^(-16) per year as 
the mean rate of change of the fine structure constant divided by the fine 
structure constant. (/alpha)

They give there estimate of the age of the universe as 13x10^9 years.

This means that the fine structure constant (alpha) has changed by the 
amount -2.86x10^-6 (with the overal error making the value something in the 
range -9.49x10^-6 and +3.77x10^-6).

this means that the fine structure constant was anything from 0.99999xalpha 
(that's 99.999 percent of it's present value) to 1.000004xalpha (that's 
100.0004 percent of it's present value.)

So, the fine structure constant at t=0 could be anything from 7.27156x10^-3 
to 7.27166x10^-3 (fine structure constant right now is 7.27163x10^-3.)


Note from these results that the value of the fine structure constant at t=
0 can go up or down or stay the same. The results from the paper are not 
conclusive enough to state which way the constant went.

Second, it should be noted that the cosmological constants chosen to make 
the assumption of the /alpha value are not the 
only values. The lambda and q(0) chosen were such that the universe was 
taken to be flat (no intrinsic curvature) and has a euclidean geometry. 
q(0) when taken to be greater than 1/2 produce an open universe with nun-
euclidean geometry, and q(0) less than 1/2 is a closed universe with 
spherical geometry. The exact value of lambda and q(0) are not known 
accurately, and so this adds a further uncertainty into the papers value.

Yet another uncertainty is the age of the universe which can be seen to 
vary quite widely depending on whose research you read.

Finally, the fact that the data shown in their Fig.1 dips at around 
redshift=1 and seems to recover towards higher redshift suggests to me 
that, though they take scrupulous pains to rule out errors in their data 
acquisition, there is something not as it should be with their data 
acquisition and/or analysis. This is of course no slur on the 
experimenters. This measurement is very difficult, and that they seem to 
have got such good results is a testament to their efforts.

Thank you for pointing out this paper, it was an interesting read.