The early universe hides behind the cloak of its Dark Ages, a period of time light can't seem to pierce. Even the length of those unseen years remains uncertain. As part of its efforts to probe the secrets of those hidden years, the European Space Agency's Planck Satellite recently announced the most precise constraints on the universe's evasive era, for the first time revealing that the first stars and their galaxies are enough to light up the darkness. Read more about When did the Lights Turn On in the Universe?