Column: Looking for New Forces

While my first column for Discover was on the multiverse, the second one is more down to Earth (as these things go): searching for new forces. Of course we are searching for new short-range forces at the Large Hadron Collider and in other particle-physics experiments, but here I'm talking about long-range "fifth forces." While there are plausible motivations for searching for such forces, and the experimentalists have done an heroic job in constraining them, I argue that the most impressive thing is how we can say what forces are not out there -- in particular, anything that would have any important effect on everyday life. There probably are more forces than we know about, but they're only going to be of direct interest to physicists, I'm afraid. No tractor beams.