Talk:Fine-structure constant

The stuff at http://www.fine-structure-constant.org looks like nonsense to me. If someone can convince me that it really belongs here, I'll put it back. --Lee Daniel Crocker

Yup, you're right, it's bogus. AxelBoldt

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Which Theories suggested that the fine structure constant should change?

JeffBobFrank 04:27, 2 Mar 2004 (UTC)

I think certain cosmic inflation models but I'm not sure. Sanders muc 21:02, 16 Apr 2004 (UTC)

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The section "Arthur Eddington and the fine structure constant" seems to contradict what it says at Eddington number. Here it states that he thought 137, then in 1938 changed to 136. There is says he started with 136 in 1938 and later changed it to 137. DÅ‚ugosz

I dont know too much about Eddington, but I would guess that when early measurements gave roughly 1/136 he said that was its exact value, and when the more accurate approximation 1/137 was known he changed it to that. It would seem a bit odd if he did it the other way around JeffBobFrank 16:04, 2 Apr 2004 (UTC)

Calculated value of alpha

The Feynman quote was good, but it sure didn't look like the rest of the section was physics. If we're going to have a section on a calculated value of <math> \alpha \ <math>, i think i've seen closer guesses than that (some English math prof named "Gilson" had a good one), but i think they're all numerology. What should a good section on this topic be? I am not sure, but i didn't think this last one was particularly good. any other ideas? r b-j 01:37, 9 Apr 2005 (UTC)

Why was the "α in the International System of Units" section removed? See this old version (http://en.wikipedia.org/w/index.php?title=Fine-structure_constant&oldid=7784963) The apparent inconsistency in the current set of SI recommended values and the CODATA one is certainly worth mentioning. I'll put it back in if I don't see a good argument materialise here. Urhixidur 13:19, 2005 Apr 9 (UTC)

there is no inconsistency in the most current value of <math> \alpha \ <math> outside of the normal experimental variance. it's just a number that we determine experimentally that presently is 1/137.03599911 . they used to think it was 1/137.03599976 . not much different. in that version, showing <math> \alpha \ <math> to 30+ digits is just very stupid. also, the expression of <math> \alpha \ <math> in terms of other fundamental constants was done both ways, using SI and cgs. it's the same number, but in cgs, they don't have an <math> \epsilon_0 \ <math> (they set <math> 4 \pi \epsilon_0 \ <math> to the dimensionless 1 by their choice of the unit charge statcoulomb ). r b-j 15:03, 9 Apr 2005 (UTC)

Definition on constant

Okey, I'm not a phycisist. But the def. of the constant seems a little odd.

"It can be defined as

<math>\alpha = \frac{e^2}{\hbar c 4 \pi \epsilon_0} \ <math>

where <math> e \ <math> is the elementary charge, <math>\hbar = h/(2 \pi) \ <math> is the

reduced Planck's constant, <math> c \ <math> is the speed of light in a vacuum, and

<math> \epsilon_0 \ <math> is the permittivity of free space."

Why don't define it like this:

<math> \alpha = \frac{e^2}{h c 2 \epsilon_0} \ <math>

Does anyone know why "they" define it this way? Thechamelon 16:41, 26 Apr 2005 (UTC)

Why define <math> \alpha<math> in terms of <math>\hbar<math> instead of h... well there are a number of reasons.

The <math> \alpha<math> factor comes from a combination of the equation of electrostatic potential, the Schrödinger equation and something I can't remeber right now. As the Schrödinger equation is defined in terms of <math>\hbar<math> then we tend to define <math> \alpha<math> using these terms.

However that just shifts the problem into why the Schrödinger equation is defined in terms of <math>\hbar<math>... well this is a little bit of waffle, but as we define wavefunctions as linear sums of eigenfunctions which are normally expressed in exponential functions. These are periodic with a period of 2 <math> \pi <math>, and I suspect it has something to do with that... But I can't manage to make the conceptual leap to give a coherant explanation why... sorry.

As one reaches deeper levels of physics, ones tends to use <math>\hbar<math> a lot more as this simplifies a lot of equations, but it is an arbitary choice in certain situations. Neo (ages ago...)

Okey then. I don't actually now anything about any of these levels of physics you are reffering to, but I understand now. Thanks! Thechamelon 19:21, 26 Apr 2005 (UTC)