When a scientific result seems to show something genuinely new, subsequent experiments are supposed to either confirm it — triggering a textbook rewrite — or show it to be a measurement anomaly or experimental blunder. But some findings seem to remain forever stuck in the middle ground between light and shadow.
Here’s one of the six:
Diabolical proton discrepancy
Given that protons are among the most common and well-studied particles in the Universe, one would expect physicists to have a solid grasp of their size. But in 2010, Randolf Pohl of the Max Planck Institute of Quantum Optics in Garching, Germany, and his team measured the radius of the proton and found it to be 4% smaller than previous estimates14. The team used a novel technique that involves replacing the electrons in hydrogen atoms with negatively charged particles called muons, and then measuring subtle shifts in the energy that is required to bump a muon into a higher-energy orbit around the single-proton nucleus. This shift is sensitive to the proton’s radius, and muons — which some 200 times more massive than electrons — make it millions of times easier to measure.
In 2013, a second study15 using the muon technique confirmed the discrepancy with previous estimates of proton size, which had come from determinations involving electrons rather than muons. Researchers tried to find flaws in the muon technique, but have now given up. “Nobody questions this experiment,” says Krzysztof Pachucki, a theoretical physicist at the University of Warsaw.
At the same time, no one can work out what could be wrong with the electron-based measurements either. The next suite of experiments, some of which are already running, could potentially solve the problem, says John Arrington, a physicist at the Argonne National Laboratory in Illinois. “It’s a zombie we hope to be able to put back in the ground soon.” More.
Yeh. We shoulda run this on Frite Nite. Meanwhile, relax physics heads, you have your work cut out for you, which means you have jobs.
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