The Quest for Mysterious Forces
Physicists stalk a delicate “fifth force” of nature, hidden within the interstices of the other four. What they have not found is even more amazing.
The trend toward unification and simplification is a major theme of modern physics. At the same time, nature has ways of surprising us, and it pays to be watchful. We know a lot about the physics of the macroscopic world, but can we be sure that we aren’t missing one of those crucial ingredients? The answer is yes: In certain well-defined cases, we can be very sure. Physicists long ago mapped the entire electromagnetic spectrum. The modern version of the search for new kinds of radiation is the search for new forces of nature. Scientists say that four forces control the entire universe? This is a pretty astonishing claim. In fact, putting aside microscopic processes happening inside atoms, everything we see can be accounted for in terms of particles interacting through just gravity and electromagnetism. From the orbits of the planets to the flexing of your muscles, every movement in the macroscopic world arises from the interplay of these two aspects of nature. At least, that’s the current picture. If that’s not right, all bets are off. How can we be so sure there aren’t other forces that we just haven’t yet been clever enough to find? The answer is, we can look for them. We know where to look, and indeed we have looked. Other forces are not out there, at least not to any significant extent.
Any new force we might someday discover must be so impotent over everyday distances that there’s no way it can affect the macroscopic world. If it could, we would already have found it. And yet a few researchers continue the search, since even an extremely feeble new force would be of enormous theoretical importance. If there are new forces, then, they are either too weak or too short-range to be relevant to our macroscopic world. Physicists still hope something will show up, perhaps at powerful particle accelerators, because discovering new forces would mean we’d have to develop completely new theories. But if we find them, these hidden forces will leave no imprint on the motions of atoms, molecules, or larger objects such as ourselves. The bad news is, no tractor beams. If we want to build an apparatus that exerts influence over large distances, we are limited to using gravity and electromagnetism. Even if that’s an established fact, though, it raises as many questions as it answers. Why just those two forces? Why do they interact the way they do? How do they relate to the possibly hidden forces at shorter distances?
We can marvel at how well we understand certain aspects of nature, while never forgetting how very far we have left to go.
Kemo D. 7