This question occurred to me while working through some textbooks. Since it is dimensionless, its value can't be explained away saying it's because of the way we chose the units. Well it turns out I'm a 100 years late to this game. I found it's even more serious than I had realized. (And it isn't really a constant?) Obviously, no one knows that answer to this question, but since it is such an outstanding question, what serious attempts are being made to answer it? Is there even a way to test it? All Google gives me is these "pop-sciency" quotes and anecdotes about how "amazing" and "mysterious" it is, often ending with an account of a scientist to [incorrectly] predict it's value based on dubious theoretical reasoning. Who works on this question and how? Do you think we'll know the answer one day? It seems to me that it might be insurmountable, but I'm sure there was a time when someone asked "Why is the sky blue?" and the best answer was "Because it is, and if it weren't then it wouldn't be."