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A Breakthrough in Measuring the Building Blocks of Nature - Facts So Romantic

Nautilus

In a recent experiment done at the Max Planck Institute for Quantum Optics, in Germany, physicist Alexey Grinin and his colleagues came a step closer to resolving one of the more significant puzzles to have arisen in particle physics over the past decade. The puzzle is this: Ordinarily, when you set about measuring the size of something, you'd expect to get the same answer no matter what you use to measure it--a soda can has the diameter it does whether you measure it with a tape measure or callipers (provided these are properly calibrated, of course). Something must be amiss if your attempts to measure the can return different answers depending on the equipment, yet this is precisely what's happened over multiple attempts to measure the spatial extent of a proton. What's potentially at stake is our understanding of the building blocks of reality: the differing measurements could be heralding the existence of new forces or particles. What does it mean for a subatomic particle to have a measurable "size"?


Physicists Finally Nail the Proton's Size, and Hope Dies Quanta Magazine

#artificialintelligence

In 2010, physicists in Germany reported that they had made an exceptionally precise measurement of the size of the proton, the positively charged building block of atomic nuclei. The result was very puzzling. Randolf Pohl of the Max Planck Institute of Quantum Optics and collaborators had measured the proton using special hydrogen atoms in which the electron that normally orbits the proton was replaced by a muon, a particle that's identical to the electron but 207 times heavier. Pohl's team found the muon-orbited protons to be 0.84 femtometers in radius -- 4% smaller than those in regular hydrogen, according to the average of more than two dozen earlier measurements. If the discrepancy was real, meaning protons really shrink in the presence of muons, this would imply unknown physical interactions between protons and muons -- a fundamental discovery.


Physicists Finally Nail the Proton's Size, and Hope Dies Quanta Magazine

#artificialintelligence

In 2010, physicists in Germany reported that they had made an exceptionally precise measurement of the size of the proton, the positively charged building block of atomic nuclei. The result was very puzzling. Randolf Pohl of the Max Planck Institute of Quantum Optics and collaborators had measured the proton using special hydrogen atoms in which the electron that normally orbits the proton was replaced by a muon, a particle that's identical to the electron but 207 times heavier. Pohl's team found the muon-orbited protons to be 0.84 femtometers in radius -- 4% smaller than those in regular hydrogen, according to the average of more than two dozen earlier measurements. If the discrepancy was real, meaning protons really shrink in the presence of muons, this would imply unknown physical interactions between protons and muons -- a fundamental discovery.


How big is a proton? No one knows exactly, and that's a problem

New Scientist

Six years after physicists announced a bafflingly too small measurement of the size of the proton, we're still not sure what's going on. With the release of new data today, the mystery has, if anything, got deeper. Protons are particles found inside the nucleus of atoms. For years, the proton's radius seemed pinned down at about 0.877 femtometres, or less than a quadrillionth of a metre. But in 2010, Randolf Pohl at the Max Planck Institute of Quantum Optics in Garching, Germany, got a worryingly different answer using a new measurement technique.


The 'Proton Radius Puzzle' Is Very Real, New Experiment Confirms

International Business Times

At first glance, this seems like a straightforward question that should have a straightforward answer. In real life, however, the situation is slightly more complicated. In 2010, a team of scientists observed something that still can't be explained. While trying to improve the accuracy of measurement of a proton's radius -- which had long back been pinned down at 0.877 femtometres -- they found that if the electron in a hydrogen atom is replaced by its heavier cousin -- the muon -- the proton seems to shrink. When this was done, the radius of the proton came out to be 0.84 femtometre -- 4 percent smaller than the average measured through other means.