Scientists Confirm Existence of Moon

Sean Carroll in Preposterous Universe:


There it is! I can definitely make out the Moon.

Bit of old news here — well, the existence of the Moon is extremely old news, but even this new result is slightly non-new. But it was new to me.

Ice Cube is a wondrously inventive way of looking at the universe. Sitting at the South Pole, the facility itself consists of strings of basketball-sized detectors reaching over two kilometers deep into the Antarctic ice. Its purpose is to detect neutrinos, which it does when a neutrino interacts with the ice to create a charged lepton (electron, muon, or tau), which in turn splashes Cherenkov radiation into the detectors. The eventual hope is to pinpoint very high-energy neutrinos coming from specific astrophysical sources.

For this purpose, it’s the muon-creating neutrinos that are your best bet; electrons scatter multiple times in the ice, while taus decay too quickly, while muons give you a nice straight line. Sadly there is a heavy background of muons that have nothing to do with neutrinos, just from cosmic rays hitting the atmosphere. Happily most of these can be dealt with by using the Earth as a shield — the best candidate neutrino events are those that hit Ice Cube by coming up through the Earth, not down from the sky.

More here.