Most of you have probably seen a story or post about the Fermilab Muon g-2 experiment. I have two problems with the way this has been treated by most science popularizers.
In keeping with the worst features of pedantry I'm not going to give a good explanation of the experiment in this post, just complain about certain elements in the coverage. For an explanation that avoids the first problem try this.
The first issue is pretty straightforward and, in the spirit of this blog, rather pedantic. In an attempt to explain what the experiment is measuring many stories describe gyroscopic precession as a "wobble". This is a mistake. Wobble is defined as an irregular (e.g.) action. The effect at the heart of the g-2 experiment is far from irregular. In fact it is extremely regular, so regular that it can be measured to an incredible level of precision. Without that level of precision the experiment would be useless to look at the phenomena involved. The use of a term that has irregularity at its heart in a story about extreme precision produces a level of cognitive confusion that cannot help but cause confusion. I suspect that most people don't realize that this confusion is an issue but I've seen this effect in many cases where the popular treatment of a subject produces lots of misunderstandings.
The second issue is more interesting. This experiment, if confirmed, reveals that our theories fail to accurately predict experiments. But the more interesting question is: What will fix this error? Every story, including the one I linked to above, says that this experiment may be pointing to the existence of unknown particles or forces that aren't included in the Standard Model. This is true but it ignores what I think is a far more exciting possibility.
If we look back at the history of physics, when there have been mismatches between theory and experiment, there are two different kinds of changes that were made to our theories. The first kind of change leaves the basic theory unchanged but changes some details like the contents of list of particles. In the Standard Model calculations that go into the theoretical predictions of g-2, every type of particle needs to be considered. The second kind of change to our theories is different. Rather then keeping the basic structure of the theory unchanged and changing the details, this possibility involves an entirely new theory.
An example, that is probably familiar to most readers of this blog, involves planetary motion. The details aren't important here but a detail of Mercury's orbit wasn't being predicted correctly by Newton's Law of Universal Gravitation. Previously, errors were noticed in the orbit of Uranus. Those could be eliminated if another planet was out there and this lead to discovery of Neptune. This was an example of the first class I'm talking about. In the case of Mercury the problem wasn't a missing input in our theory. The problem was that Newton's theory of gravity needed to be replaced by Einstein's. In the limit of small masses and low velocities Einstein's theory gives the same results as Newton's. But the theories are fundamentally different. They use an entirely different set of concepts to model reality. This new theory caused a fundamental shift in the scientific view of the cosmos and the birth of major new fields of science.
I don't have any reason to think that a new theory, one that reduces to the Standard Model in some limit like General Relativity reduces to Newtonian gravity, is going to be what is needed to explain the results of the Fermilab Muon g-2 experiments. But that is a possibility that shouldn't be ignored, instead I think it should be embraced. Who knows what wonderous changes it will produce in our view of reality?
