Capricious constants

[Loren Booda]

Which of the following will prove not to be a fundamental constant?

[HallsofIvy]

Define "fundamental constant". e is simply a specific number. It is a "fundamental constant" in the same sense that 1, -5, or 37.324323 are. The others are all physics constants.

[plover]

Define "fundamental constant". e is simply a specific number. It is a "fundamental constant" in the same sense that 1, -5, or 37.324323 are. The others are all physics constants.

I expect he means the charge on an electron.

[Loren Booda]

Charge on an electron (or quark) it is.

[BobG]

Picked the universal gravitational constant, since satellites exiting the solar system have already raised some potential discrepancies that need to be explained (just a problem measuring the satellite's acceleration? or a 'true' discrepancy in acceleration?)

In general, I think the idea of fundamental constants that never change seems like a rather elusive idea. Even for 'c', speed of light, special conditions have to be set (only in a vacuum that doesn't actually exist) in order for the speed of light to remain constant. To be a 'fundamental constant', there should at least exist some unchanging value, even if our measurements of it undergo revision as our ability to measure it improve. Using that frame of reference, I think all of the above probably have some fundamental value, even if our measurement of it constantly undergoes revision.

[plover]

In general, I think the idea of fundamental constants that never change seems like a rather elusive idea. Even for 'c', speed of light, special conditions have to be set (only in a vacuum that doesn't actually exist) in order for the speed of light to remain constant.

When you say that vacuum "doesn't actually exist" are you referring to the difficulties of isolating a bit of space with no matter or force particles in it which could in principle be removed, or are you referring to the fact the space can never really be "empty" due to quantum effects?

Doesn't specification of a fundamental constant require that the properties of the "fabric" of spacetime be taken into account as part of the definition? Or to put it another way, is the idea of a fundamental "constant" as such essentially a classical idea as, in a quantum universe, the quantitatively stable values are averages?

Putting aside quantum issues (if this is possible without rendering the question meaningless), isn't a "vacuum" the stage for reactions between particles? So wouldn't the value of fundamental constants "in a vacuum" be in play in measurements taken for individual interactions such as those recorded in accelerators? (This of course assumes that the degree of transparency afforded by the detector can be determined.)

How are any of these considerations affected by the units of the "fundamental constant" in question? Would the speed of light, which superficially appears to have a more direct relation to the structure of spacetime be more affected by the above considerations than charge, which appears independent? Would the fine structure constant (being unitless) be a somehow "more fundamental" constant than the others mentioned?

My context for these questions is curiosity not challenge. I have no real sense of what the current consensus might be on these issues.