Are there constants that used to be considered fundamental constants but aren't anymore? Are there efforts to show constants (that we currently consider fundamental) aren't really fundamental or that they are related to one another? For example does some theory predict (or almost predict if certain assumptions are made) the values of $c$ or $G$ or some other constant? Do any of the constants seem to have more potential than the others to emerge from a theory and no longer be "fundamental"?
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$\begingroup$ Are you referring to something like the hydrogen emission wavelengths that were later found to be described parametrically? $\endgroup$– ChemomechanicsCommented Jul 31, 2020 at 5:28
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$\begingroup$ I think the permittivity constant $\epsilon$ is an example of this. It used to be an empirically measured value much like $G$, but then we found out it was related to the speed of light and nowadays we define it in terms of $c$ and $\mu_{0}$. Hence it is no longer fundamental because it is related to $c$. $\endgroup$– MaximusIdealCommented Jul 31, 2020 at 5:44
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The numerical values possessed by fundamental constants of physics (G, c, hbar, etc.) are not predicted by any physical theories. In addition, the Standard Model of particle physics contains a whole list of coupling constants, masses, charges, etc. which have to be measured experimentally and then plugged into the model "by hand" since they are not furnished by the theory itself.
It is thought that a real "theory of everything" would not have any undetermined parameters in it; all the physical constants from the speed of light to the mass of an electron could be calculated from first principles within that theory. This is a very tall order for any model of the universe and we are nowhere near to having such a theory at hand.
answered Jul 31, 2020 at 5:28