In 1988, Francis Halzen and John Learned proposed something that sounded eccentric. They wanted to turn part of the Antarctic ice sheet into a telescope. It would look not for light, but for neutrinos, the shyest particles in the universe.
Every second, some 65 bn of them from the Sun pass unnoticed through your fingernail. This indifference makes them ideal messengers for cosmic information. They carry no charge. So, magnetic fields cannot bend their paths. A high-energy neutrino points straight back to the cosmic accelerator that made it.
