 The neutrino is a critical component in many nuclear reactions that occur in stars. The detection of solar neutrinos and of neutrinos from supernova 1987A marked the beginning of neutrino astronomy. Today there are a number of neutrino observatories in operation around the world and one under construction to better understand these fundamental but elusive particles. We'll take a closer look at one of them, the Super Kameikande, located 1,000 meters underground in a Japanese mine. It contains a lake holding 50,000 tons of ultra-pure water surrounded by an inner detector with over 11,000 photomultiplier tubes and flash when struck by a photon created by a neutrino interaction with the water. The speed of light in water is slower than the speed of light in a vacuum. A neutrino interaction with the electrons or nuclei of water can produce a charged particle that moves faster than the speed of light in water. This creates a cone of light known as Chernikov radiation. This is the optical equivalent of a sonic boom. The Chernikov light is projected as a ring on the wall of the detector and recorded by the photomultipliers. This figure shows the sun as observed by Super Kameikande. The sun sends about 65 billion neutrinos per square centimeter our way every second. That's over 400 billion neutrinos per square inch per second. That's a lot of neutrinos. And almost all of them pass right through the earth and out the other side. Trillions of neutrinos are passing through your body every second. I think that neutrinos will wind up playing a significant role in our understanding of dark matter.