The Fine Structure Constant

Well, it's very late, so let's talk about one of the most interesting and obscure "things/values/contstants/whatever" in the universe: the 'fine structure constant', universally represented by the Greek letter alpha 'α'.
It's a coupling constant, in that it characterizes the strengh of the electromagetic interactions of everything.
In other words, it's fundamentally involved in one of the four fundamental interactions in the universe:
Electromagnetism
the strong nuclear force
the weak nuclear force, and
gravitation.
(PS: That's all there is, as we know it)
Alpha has always been mysterious, since it's a dimensionless number -- not 'meters per second' or 'pounds per square foot' or anything -- it's just a number. Where the hell did it come from, and why is it what it is, and not something else?

Here's a prophetic comment from the Nobel-prize-winning physicist Richard Feynman, more than 40 years ago:
There is a most profound and beautiful question associated with the observed coupling constant e the amplitude for a real electron to emit or absorb a real photon. It is a simple number that has been experimentally determined to be close to -0.08542455. (My physicist friends won't recognize this number, because they like to remember it as the inverse of its square: about 137.03597 with about an uncertainty of about 2 in the last decimal place. It has been a mystery ever since it was discovered more than fifty years ago, and all good theoretical physicists put this number up on their wall and worry about it.) Immediately you would like to know where this number for a coupling comes from: is it related to π or perhaps to the base of natural logarithms? Nobody knows. It's one of the greatest damn mysteries of physics: a magic number that comes to us with no understanding by man. You might say the "hand of God" wrote that number, and "we don't know how He pushed his pencil." We know what kind of a dance to do experimentally to measure this number very accurately, but we don't know what kind of dance to do on the computer to make this number come out, without putting it in secretly!

Feynman anticipated by a great leap of intuition and genius, that  'alpha' IS actually related to pi and and e (the base of natural logarithms), as has been subsequently shown - maybe.

But it's still a fundamental issue in the 'anthropic' question about physical theories: are the theories we use to explain the universe -- right down to its fundamental constants -- a necessary result that observations of the physical universe have to be compatible with the intelligent life which observes it? (Take an aspirin here).
It's relatively-easily calculated that alpha (the fine-structure constant) could not be greatly different from what it is, in our universe: a small variation on either side would make it impossible for stars to form, and eventually for carbon and oxygen atoms to be created through nuclear synthesis: no carbon atoms = no carbon-based lifeforms like us. Thus also, no one to measure these constants....

So, physicists still ask -- why 'this' rather than 'that'? ...

PS: this is still an open and controversial question. Some recent experimental evidence suggests that this constant: isn't.
It may now or have in the past varied in different parts of our universe. If this is the case, it is still unclear what this means...
Ref:
http://www.physorg.com/news202921592.html