{"id":604111,"date":"2026-04-14T20:06:20","date_gmt":"2026-04-14T20:06:20","guid":{"rendered":"https:\/\/www.newsbeep.com\/ca\/604111\/"},"modified":"2026-04-14T20:06:20","modified_gmt":"2026-04-14T20:06:20","slug":"physicists-think-theyve-resolved-the-proton-size-puzzle","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ca\/604111\/","title":{"rendered":"Physicists think they’ve resolved the proton size puzzle"},"content":{"rendered":"

A puzzling discrepancy<\/p>\n


\n \"A
\n <\/a><\/p>\n

A vacuum chamber used to measure electron transitions in atomic hydrogen<\/p>\n

\n Credit:
\n Axel Beyer\/MPQ\n <\/p>\n

\n A vacuum chamber used to measure electron transitions in atomic hydrogen<\/p>\n

Credit:<\/p>\n

Axel Beyer\/MPQ<\/p>\n

Subsequent measurements by various groups were inconclusive. For instance, in 2013<\/a>, the same international team performed muon-based experiments that confirmed their 2010 value, producing a measurement of 0.84 femtometers<\/a> for the proton\u2019s radius, with a discrepancy of 7 sigma. Another experimental variation in 2016<\/a> involved replacing the electron with a muon in a deuterium atom\u2014a heavier isotope of hydrogen, with a neutron as well as a proton and an electron. The idea was that the presence of a neutron would alter how electrons and muons perceive the proton\u2019s charge. That, too, was in line with the 2010 result.<\/p>\n

However, two experiments using regular hydrogen to measure the proton radius produced mixed results: A 2017 study<\/a> also confirmed the 2010 result, while a 2018 measurement<\/a> was in line with the larger value before the 2010 experiment. In 2019, York University scientists opted to make an electron-based measurement of the proton radius, in hopes of bringing the various conflicting results closer to a consensus. The result<\/a>: Their measurement of 0.833 femtometers agreed with the smaller value from the 2010 study.<\/p>\n

That brings us to the latest two papers, both of which involved experiments with hydrogen atoms in a vacuum chamber. They used lasers to control the electrons and measured the transitions between energies; this enabled them to infer the exact dimensions of the proton\u2019s charge radius. Based on the combined results, the proton has a radius of about 0.84 femtometers, or less than 1 million-billionth of a meter, once again in keeping with the 2010 measurement that kicked off the debate.<\/p>\n

\u201cThe proton radius should be a universal property; it should give the same result no matter how you look at it,\u201d Juan Rojo, a physicist at Vrije University Amsterdam in the Netherlands, who was not involved in either experiment, told New Scientist<\/a>. \u201cThis is why these two papers are quite nice, because they provide different perspectives to the same number.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"A puzzling discrepancy A vacuum chamber used to measure electron transitions in atomic hydrogen Credit: Axel Beyer\/MPQ A…\n","protected":false},"author":2,"featured_media":604112,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[49,48,314,66],"class_list":{"0":"post-604111","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-ca","9":"tag-canada","10":"tag-physics","11":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/604111","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=604111"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/604111\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/604112"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=604111"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=604111"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=604111"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}