One of the biggest science stories of 2016 was the observation of gravitational waves. These waves were predicted by Einstein when he developed his theory of general relativity. We usually think about Isaac Newton when we think about gravity, with the (perhaps apocryphal) apple falling from a nearby tree as inspiration. In Newton’s day and for a long time afterward, gravity was seen as a force that acted instantaneously no matter what the distance. If, say, the distance between two bodies changed, the entire universe would be affected by that change simultaneously.