Topical science magazine. Washington state, in the north west of America, is home to one of the most bizarre scientific experiments in the world. In the middle of a landscape that comes straight out of a cowboy movie, there's a long metal structure that stretches as far as the eye can see. This is Ligo, an incredibly precise instrument that's searching for some of the faintest signals in the universe, gravitational waves. Geoff Watts meet the physicists who are searching for these cosmological needles in a haystack.