The field of particle physics has a new and improbable star: the muon, which is sometimes referred to as a fat electron. For the second time, this unassuming resident of the subatomic world has appeared to flout the known laws of nature. To some experts, that suggests it might reveal entirely unknown rules.
Muons drew the attention of physicists around the world after an experiment at the Fermi National Accelerator Laboratory, or Fermilab, in Illinois demonstrated that they’re far more magnetic than expected. The results, published in April by the Muon g-2 collaboration (pronounced “g minus two”), run counter to the predictions of the top available particle physics theory. That leaves three possibilities: the theory itself is wrong, the experiment was faulty, or, most tantalizing, it could also mean that we're close to discovering new forms of matter and energy that are essential to the ordering of the cosmos but have gone undetected.
