New instruments will study the universe’s most mysterious component

LIKE A BLINDLSSTLSSTLSST prophet, the observatory perched atop Cerro Pachón in the Chilean Andes ponders the heavens. Eyeless for now, the Large Synoptic Survey Telescope () will from 2022 turn into the biggest digital camera on Earth. Taking 3,200 megapixel snaps with an exposure time of 15 seconds, to capture an area 40 times the size of the full moon, the will map almost the entire southern hemisphere once every three or four nights for a decade. The picture so generated will assess how matter (in the form of stars and galaxies) is distributed, shedding light on the clash of forces that have brought the universe to its current state, and thus scrying its future.The is one of a string of ground and space-based experiments that will soon help physicists understand a celestial tug-of-war. One side of the contest, gravity, is described by Albert Einstein’s general theory of relativity. The attractive effects of gravity on matter thrown apart by the Big Bang would be expected to slow the universe’s expansion over the course of time. In 1998, though, astronomers discovered that the opposite was true—the universe is now expanding at a faster clip than before.