China’s moon mission will probe cosmic dark ages

On 21 May, China plans to launch a satellite with a vital but unglamorous mission. From a vantage point beyond the moon, Queqiao, as the satellite is called, will relay data from Chang'e 4, a lander and rover that is supposed to touch down on the lunar far side before the end of the year. But a Dutch-made radio receiver aboard Queqiao will attempt something more visionary. In the quiet lunar environment, it will listen to the cosmos at low frequencies that carry clues to the time a few hundred million years after the big bang, when clouds of hydrogen gas were spawning the universe's first stars.