A muon is like an overweight electron. Like many subatomic particles, it doesn’t live very long. In 2001, scientists at Brookhaven National Laboratory in Long Island discovered that muons didn’t have the predicted magnetism. It was 2.5 times as large. Since science studies require replication and the experiment was expensive, Brookhaven could not try to verify their result. Fermi Lab in the US took up the challenge. Fermi Lab is near Chicago in Illinois and not far from where I once lived and took advantage of their theater offerings to provide convenient cultural events for their researchers.
Brookhaven retired the 50 ft diameter magnet racetrack that spun the muons, and it was sent on a 3,200 mile trip from Long Island to Batavia, Illinois in 2013 via barge around Florida, up the Mississippi River, then by truck through Illinois. It took years for Fermilab to gear up, but they recently replicated the results.
The result is deemed as important as finding the Higgs Boson. So the magnetism is not what they expected. What’s the big deal? Science is not like mathematics where theories can be proved or disproved. A scientific theory cannot be proved, but it can be disproved. If a scientific theory predicts X, Y, and Z, and later it turns out the X, Y, and Z occur, it is only evidence that the theory is correct. It does not mean that X, Y, and Z are true because of the theory. However, if something predicted by the theory turns out not to be the case, the theory cannot be right. That’s what has just happened. Now, all of the believed theory mostly emanating from Einstein must have a flaw! The challenge is to find it.