Look closely at this spot .
Do you see a pile of neutrinos?
Your first task...find out what a neutrino is. A good start is Dave Casper's web site.
One place that collects evidence of neutrinos landing is Japan's Super-Kamiokande, which cost only about 100 million dollars. Holding 12.5 million gallons of water, the Super-K basically is a cylinder (41.4 meters high, 39.3 m diameter) whose surface is covered by glass photomultiplier tubes that detect the light emitted when a neutrino lands and collides with the water.
Since 1956, an estimated total of 725,000 neutrinos have been detected. Yet, neutrinos reach earth at a rate of 60 billion neutrinos per square centimeter per second.
Question: How many neutrinos reach the total surface of the earth each second? In a day? In a year?
Source: Wired, June 2006, p. 27