  The first solar neutrino experiment led by Raymond Davis Jr. showed a deficit
of neutrinos relative to the solar model prediction, referred to as the "solar
neutrino problem" since the 1970s. The Kamiokande experiment led by Masatoshi
Koshiba successfully observed solar neutrinos, as first reported in 1989. The
observed flux of solar neutrinos was almost half the prediction and confirmed
the solar neutrino problem. This problem was not resolved for some time due to
possible uncertainties in the solar model. In 2001, it was discovered that the
solar neutrino problem is due to neutrino oscillations by comparing the
Super-Kamiokande and Sudbury Neutrino Observatory results, which was the first
model-independent comparison. Detailed studies of solar neutrino oscillations
have since been performed, and the results of solar neutrino experiments are
consistent with solar model predictions when the effect of neutrino
oscillations are taken into account. In this article, the history of solar
neutrino observations is reviewed with the contributions of Kamiokande and
Super-Kamiokande detailed.
