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Originally built to speed up calculations, a machine-learning system is now making shocking progress at the frontiers of experimental quantum physicsQuantum physicist Mario Krenn remembers sitting in a café in Vienna in early 2016, poring over computer printouts, trying to make sense of what MELVIN had found. MELVIN was a machine-learning algorithm Krenn had built, a kind of artificial intelligence. Its job was to mix and match the building blocks of standard quantum experiments and find solutions to new problems. And it did find many interesting ones. But there was one that made no sense. “The first thing I thought...

Sophisticated measurements from experiments indicate the radius is 4% smaller than thought. If true, the finding could have major ramifications for the standard model used in modern physics. Physicists might have to rethink what they know about, well, everything. European researchers dropped a potential bombshell on their colleagues around the world Wednesday by reporting that sophisticated new measurements indicate the radius of the proton is 4% smaller than previously believed. In a world where measurements out to a dozen or more decimal places are routine, a 4% difference in this subatomic particle — found in every atom's nucleus — is...

An international team measures the charge radius of the hydrogen nucleus and stumbles across some mysteries of physics Big problems sometimes come in small packages. The problem with which physicists must now concern themselves measures a mere 0.0350 millionth of a millionth of a millimetre. This is precisely the difference between the new, smaller, dimension of the proton, the nucleus of the hydrogen atom, and the value which has been assumed so far. Instead of 0.8768 femtometres it measures only 0.8418 femtometres. At the Paul Scherrer Institute in Switzerland, an international team of researchers including physicists from the Max Planck...

Using the first new method in half a century for measuring the size of the proton via electron scattering, scientists have produced a new value for the proton's radius in a new experiment...The new value for the proton radius that was obtained is 0.831 fm, which is smaller than the previous electron-scattering value of 0.88 fm...

Only in physics can a few quintillionths of a meter be cause for uneasy excitement. A new measurement finds that the proton is about 4 percent smaller than previous experiments suggest. The study, published in the Jan. 25 issue of Science, has physicists cautiously optimistic that the discrepancy between experiments will lead to the discovery of new particles or forces. “Poking at small effects you can’t explain can be a way of unraveling a much bigger piece of physics,” says Carl Carlson, a theoretical physicist at the College of William and Mary in Williamsburg, Va., who was not involved in...