Neutrinos

a) what are neutrinos?
Neutrinos are similar to an electron, with one difference: neutrinos do not carry electric charge. Because neutrinos are electrically neutral, they are not affected by the electromagnetic forces that act on electrons. But the neutrinos are affected only by a "weak" sub-atomic force that is shorter range than electromagnetism, and because of that they are able to pass through long distances in matter without being affected by it.

b) why are they so important to understanding the sun?
They are important because the sun is a nuclear fusion reactor, which is powered by a proton-proton chain. This converts four hydrogen nuclei (protons) into helium, neutrinos and energy. The left over energy is released as gamma rays ands as kinetic energy of the particles, also which includes neutrinos. Neutrinos ravel from the suns core to earth without any absorption by the sun's outer layer.

c) Would YOU be able to persist for as long as Bahcall and Davis did when people doubted your experiment? No, because I would probably start doubting myself after 3 decades!

d) what is the importance of neutrinos having mass
Neutrinos that have mass can change from the type that had been expected to be produced in the Sun's interior. They change into two types that would not be caught by the detectors in use at the time. As neutrino detectors become sensitive measure the flow of neutrinos from the Sun, it was obvious that the number detected was lower than that predicted by models of the solar interior. In various experiments, the number of detected neutrinos was between one third and one half of the predicted number. This came to be known as the solar neutrino problem.

e) where are neutrinos being researched around the world?
They are being researched in South Dakota. Homestake Neutrino Detector 1.5 km underground. They are underground to protect them from the other unwanted cosmic ray particles. They are also being researched in Canada - Sudbury Neutrino Observatory which is 2 km underground. The tank is 12 meters in diameter and contains 1,000 tons of heavy water. Another location is in Japan - Kamiokande Neutrino Detector.