The South Pole Telescope, which began scientific observations in 2007, surveys the sky for cosmic microwave background radiation, the "afterglow" of the Big Bang. Free electrons in galaxy clusters distort the radiation, casting "shadows" in the background radiation that astrophysicists have already used to identify previously unknown galaxy clusters.

The South Pole is the best place on the planet for these observations, as it's on a plateau that's almost 2 miles high, and the high, cold air contains very little radiation-distorting water vapor.