On 10 August, an international collaboration of scientists at the Fermi National Laboratory (Fermilab) on the outskirts of Chicago announced an updated and more precise measurement of the way muons interact with a magnetic field.
The update was eagerly awaited, largely because previous measurements disagreed with the predictions of the Standard Model of particle physics. The discrepancy has led to talk of a possible fifth force of nature. But what would that mean, and what did the update tell us?
There are four known fundamental forces: gravity, the