Now my understanding of neutrino detectors is that there are two common fluids used in the detectors, either Tetrachloroethylene (C2Cl4) aka "dry-cleaning fluid", and heavy water (D20). Why were these substances chosen specifically? Is there something about the elements within these substances that make them easier to study vs. any other element on the periodic table? Also within these two substances, only one of the elements in each is singled out for study. In the case of C2Cl4, it is the Chlorine that is studied, and not the Carbon. In the heavy water, it is the Deuterium that is studied and not the Oxygen. Why is that? Isn't a neutrino just as likely to hit the Carbon or the Oxygen atoms, in each case? Now, a related question. Is the Sudbury Neutrino Observatory (SNO) the only one in the world that can detect all neutrino events, and not just electron-neutrino events, or are there others now? SNO uses heavy water, is heavy water better for all-neutrino detection vs. C2Cl4? According to the following article, under the section about Cerenkov radiation: http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/einvel.html According to the above, a muon-neutrino strike maintains a very well-defined light-cone, whereas an electron-neutrino strike results in an electron shower which produces a very diffuse light-cone. Why should there be an electron shower from a single electron-neutrino hit, while a muon-neutrino hit doesn't result in a muon shower? Aren't each neutrino strike just producing one electron or one muon, respectively? Why should there even be a shower of electrons, when only one new electron is produced?