I recently stumbled upon an essay by Howard Georgi called “Effective quantum field theories”, which was published in a book called “The New Physics” edited by P. Davies. Quite surprisingly, near the end of the essay he starts writing “about how theoretical particle physics works as a sociological and historical phenomenon“.
Georgi is not only the inventors of one of my favorite ideas for physics beyond the standard model (Grand Unified Theories), but also the author of “Lie algebras in particle physics”, one of the best books on the role on group theory in physics. (The role of group theory in physics happens to be my favorite topic). So he knows what he is talking about.
The essay is from 1989, but in the light of recent experimental null results, I thought it sounded as it could’ve been written a few days ago. He outlines a quite unique perspective and I’m pretty sure not many people have heard of it. Especially when we take into account how good this passage is hidden in a big book, in an essay about a completely different topic.
Thus, here is the relevant passage:
“The progress of the field is determined, in the long run, by the progress of experimental particle physics. Theorists are, after all, parasites. Without our experimental friends to do the real work, we might as well be mathematicians or philosophers.
When the science is healthy, theoretical and experimental particle physics track along together, each reinforcing the other. These are the exciting times. But there are often short periods during which one or the other aspect of the field gets way ahead. Then theorists tend to lose contact with reality. This can happen either because there are no really surprising or convincing experimental results being produced (in which case I would say that theory is ahead – this was the situation in the late 1970s and early 1980, before the discovery of the W and Z) or because the experimental results, while convincing, are completely mysterious (in which case I would say that experiment is ahead – this was the situation during much of the 1960s).
During such periods, without experiment to excite them, theorists tend to relax back into their ground states, each doing, whatever comes most naturally. As a result, since different theorists have different skills, the field tends to fragment into little subfields. Finally, when the crucial ideas or the crucial experiments come along and the field regains its vitality, most theorists find that they have been doing irrelevant things.
But the wonderful thing about physics is that good theorists don’t keep doing irrelevant things after experiment has spoken. The useless subfields are pruned away and everyone does more or less the same thing for a while, until the next boring period. […]
As I suggested at the beginning of this chapter, I am somewhat concerned about the present state of particle theory. The problem is, as I mentioned before, that we are in a period during which experiment is not pushing us in any particular direction. As such times, particle physicists must be especially careful.
We now understand the strong, weak and electromagnetic interactions pretty well. Of course, that doesn’t mean that there isn’t anything left to do in these fields any more than the fact that we understand quantum electrodynamics means that there is nothing left to do in atomic physics. The strong interactions, quantum chromodynamics, in particular will rightly continue to absorb the energies of lots of theorists for many decades to come. But it is no longer frontier particle physics in the sense that it was fifteen years ago.”
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