Gravitational Waves: How Einstein's spacetime ripples reveal the secrets of the universe

On 14 September 2015, after 50 years of searching, gravitational waves were detected for the first time and astronomy changed for ever.
Until then, investigation of the universe had depended on electromagnetic radiation: visible light, radio, X-rays and the rest. But gravitational waves – ripples in the fabric of space and time – are unrelenting, passing through barriers that stop light dead.
At the two 4-kilometre long LIGO observatories in the US, scientists developed incredibly sensitive...