Word: electronics
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Dates: during 1990-1999
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Members of the NASA-led team arrived in Washington fully prepared to enter the fray. They distributed copies of their peer-reviewed report, which the prestigious journal Science accepted for publication in this week's issue, and displayed some remarkable scanning electron-microscope images of the tiny structures found inside the meteorite...
...neutron in the nucleus doesn't make the water's appearance, chemistry or taste any different from ordinary water used in other detectors. It does, however, change its nuclear structure enough to make this observatory sensitive not just to one but to all three known varieties of neutrinos. Only electron neutrinos--one of the three types--generate flying electrons. But all three will knock the extra neutron from heavy-water molecules...
...allow the device to solve one of the enduring mysteries of astrophysics. Known as the solar neutrino problem, it was discovered back in the 1960s. According to calculations originally made by Bahcall, the nuclear fusion reactions at the sun's core should be generating about 200 trillion trillion trillion electron neutrinos every second. But when physicists set out to find them, they were shocked to see evidence of only about a third that number. Among the possible explanations: perhaps scientists didn't understand nuclear physics as well as they thought, or maybe some unknown factor was cooling...
...physicists eventually became intrigued with a third idea. Perhaps some electron neutrinos were switching identities, changing by a process called oscillation into muon or tau neutrinos (the two other varieties) en route to Earth. If so, existing detectors could never see them. And while some of the fine print in the laws of physics says that a massless neutrino can't change its stripes, a neutrino with even a tiny bit of mass might. If neutrinos have mass, they can change; conversely, if they can change, they must have mass, despite what textbooks have been saying for decades...
Thanks to its exquisite sensitivity, however, S.N.O. may be able to settle the question of whether the sun's deficit in electron neutrinos is offset by a previously undetected flood of the other kinds. If this works as expected, it should determine once and for all whether neutrinos oscillate. If they don't, solar physics will have to be revised; if they do, particle physics will be turned on its head. "I'd say our solar models are quite reliable," says Bahcall. "But that's why you do experiments. Because what you think you know might turn...