The fine structure constant is a dimensionless number derived from some fundamental physical constants like the speed of light in a vacuum. Its value is roughly 1/137. It was established in the first few moments of the big bang as matter solidified and reality as we know it more or less settled out. If the fine structure constant differed by just a few percent in either direction, the laws of nature would differ to the extent that the chemical reactions that life as we know it depends upon could not take place. The anthropic principle is a philosophical argument that says these fundamental constants are what they are because if they weren't we couldn't be here to measure them.
We can in fact measure these fundamental physical constants, and so compute alpha, not just in any well equipped laboratory, but also elsewhere at any number of observatories around the world by pointing telescopes at distant stars and using very accurate spectroscopes. We know about how distant these stars are from the amount the light from each is red-shifted.
But when we do this, we get different numbers for alpha, and the numbers we get do not depend on how far away the stars are (which would imply that the constant changes with time, which would be less troublesome) but in what direction we look (implying that it changes with location). This is mind boggling, because either the fundamental laws of nature vary from place to place, or something else is affecting our instruments in a strange but very consistent manner.
Mrs.Overclock (a.k.a. Dr. Overclock, Medicine Woman) and I were discussing this over dinner when my science fictional lobe came up with these ideas:
1. If the constant varies across space, that could explain the Fermi Paradox: there isn't life (as we define it anyway, which determines how we try to detect it) elsewhere because there really is something very special about our region of space.
2. An ultra-super-hella-weapon that altered the fine structure constant in a region of space would be... useful... for eliminating troublesome civilizations. The term "weapon of mass destruction" seems laughably modest to describe such a device.
This is the kind of stuff I think about on a daily basis.
The science/fiction blog io9 had a great article on this very topic that I missed while Mrs. Overclock and I were in Australia (at the World Science Fiction Convention in Melbourne) and New Zealand (touring The Lord of the Rings filming locations on the south island near Queenstown and Wanaka). Check it out!
Dave Goldberg, Ph.D. physicist, wrote a detailed and very readable article on this topic, also over at io9. Check it out squared!
Chip Overclock™ is the pen name of John Sloan, a freelance product developer based in Denver Colorado USA who specializes in very large and very small systems: distributed, real time, high performance, embedded, concurrent, parallel, close to bare metal.