IceCube, the world's largest observatory ever built to detect the elusive sub-atomic particles called neutrinos, has just been completed in the crystal-clear ice at the South Pole. Trillions of neutrinos stream through the human body at any given moment, but they rarely interact with regular matter, and researchers want to know more about them. The observatory provides an innovative means to investigate the sources and properties of neutrinos, which originate in some of the most spectacular phenomena in the universe.
Neutrinos are tiny—really, really, tiny—particles of matter. They are so small, in fact, that they pass between, and even through, atoms without interacting at all. Neutrinos are everywhere: If you start counting now, more than 10 quintillion (that's 10^19 or ten trillion billions) of them will have passed through your body by the time you finish this article. Yet only one of those 10 quintillion neutrinos will likely interact with an atom in your body. The rest will go merrily on their way.