AT THE BOTTOM OF THE WORLD, buried beneath more than two kilometers of ice, there lies a trap. But it doesn’t lie in wait for seals, penguins or other unsuspecting antarctic beasties; it seeks one of the most elusive beasts in the Universe – a particle so numerous it outnumbers every other particle in the cosmos, yet so stealthy that billions of their number can (and do) pass right through your body without prompting so much as a tickle. It seeks the ultimate cosmic ghost: the neutrino.
The trap is actually a neutrino detector aptly known as IceCube that, instead of scanning the heavens, gazes through the Earth – using its mass to filter out any unwanted particles – in the hope that a neutrino from beyond our galaxy stops by to say hello.
Neutrinos are created by all sorts of high-energy phenomena. We make them in our nuclear reactors and thermonuclear reactions in the Sun spew countless trillions of them in our direction every second. But the neutrinos IceCube seeks are the product of even more violent processes beyond our solar system, such as supernovae and radiation vented from supermassive black holes.