Basic physics has taken a step forward in China. In its very first physics result, the Jiangmen Underground Neutrino Observatory (JUNO) has measured two of the fundamental parameters governing how neutrinos change identity as they travel—and done so with greater precision than all previous experiments of recent decades combined. The result, published in Nature on June 10, used just 59 days of data and cut the uncertainty on these “oscillation” parameters by roughly a factor of 1.6.
JUNO, led by the Institute of High Energy Physics of the Chinese Academy of Sciences, is a marvel of engineering: a 20,000-ton sphere of liquid scintillator suspended 650 meters underground, watched by more than 43,000 photomultiplier tubes that catch the faint flashes when a neutrino interacts. Locating the experiment deep underground serves to shield it from cosmic radiation interference, and its geographical location puts it equidistant from the reactor cores of two nuclear powerplants, whose emitted neutrinos the scientists are measuring. JUNO’s purpose is to help resolve one of the deepest open questions in physics—the ordering of the neutrino masses.
That the new detector reached this precision in two months of operation reminds us what human creativity can accomplish when organized for a meaningful purpose.