New research finds that the ideal time to study the cosmos was more than 13
billion years ago, just about 500 million years after the Big Bang - the era
(shown in this artist's conception) when the first stars and galaxies began
to form. Since information about the early universe is lost when the first
galaxies are made, the best time to view cosmic perturbations is right when
stars began to form. Modern observers can still access this nascent era from
a distance by using surveys designed to detect 21-cm radio emission from
hydrogen gas at those early times.