As we have seen, the fact that the observed flux of solar neutrinos was far less than that predicted by the Standard Solar Model cannot seemingly be explained by modifications of that model. Two alternative explanations have been offered. The first is the idea of neutrino decay. If neutrinos have a finite lifetime (less than approximately 8 minutes, the time of travel between the sun and the earth; otherwise, a significant number would not decay before the neutrinos reached the earth), then one could explain the solar neutrino deficit by the fact that the neutrinos decayed before reaching the earth. This possibility was ruled out when neutrinos from the supernova SN 1987A were observed at the earth (Hirata et al. 1988a). If the neutrino lifetime is short enough to explain the lack of solar neutrinos, then one would not expect to observe any neutrinos from the far more distant supernova. “The idea that neutrino decay into some sterile form 1 might provide an explanation of the solar neutrino problem died in its most straightforward form along with the supernova SN 1987A, since the observation of (anti)neutrinos from that stellar explosion clearly requires survival times much longer than the Sun to Earth transit” (Anselmann et al. 1992b, p. 395).