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Neutrinos are experimentally determined to have an extremer small mass. Huge numbers of neutrinos are created in a supernova at the same time as massive amounts at light ate ?rst produced. When the 1987A supernova occurred in the Large Magellanic Cloud, visible primarily in the Southern Hemisphere and some 100,000 light−years away from Earth, neutrinos from the explosion were observed at about the same time as the light from the blast. How could the relative arrival times of neutrinos and light be used to place limits on the mass of neutrinos?
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