This article was first published in the March 2016 issue of WIRED magazine. Be the first to read WIRED's articles in print before they're posted online, and get your hands on loads of additional content by subscribing online.
Deep beneath the Gran Sasso mountain in central Italy, the world's most sensitive dark-matter detector hangs suspended in a bath of liquid xenon. This is XENON1T, the Gran Sasso National Laboratory's attempt to observe the invisible stuff that is thought to make up 85 per cent of matter in the Universe.
"We know it's there, but we can't see it," says Elena Aprile, the project's leader. "We hope that a particle will eventually hit a normal atom [inside XENON1T] so we can see the signature."
XENON1T measures the flashes of light and charge released when a presumed dark-matter particle collides with ordinary matter. These collisions are rare -- only one a year for every tonne of xenon -- so the larger the experiment, the better chance there is of a positive result. The detector is 1m by 1m and contains 3,500kg of xenon, cooled to -95˚C to make it a liquid.
XENON1T is expected to deliver its first relevant data this spring, but even if everything goes to plan there may be nothing to report.
The experiment is based on the WIMP hypothesis, which suggests that dark matter is made of weakly interacting massive particles. "XENON1T will not see anything if the WIMP hypothesis is wrong," says Aprile. "These experiments will determine the next decade of effort in this search." Until then, we're in the dark.
This article was originally published by WIRED UK
