What does it mean for space to be curved? Moving through curved space is not the same as driving down a curved road, because when you're moving through curved space, you think you're travelling in a straight line! How can this be? Imagine approaching an area of great curvature, which therefore is very hard to traverse. The easiest way to get to the other side is to go around, rather than through. Thus the line (which is the shortest distance between two points, as defined by geometry) of your path is not straight, but curved. Such a line is called a geodesic. curved geodesics

In our universe, things travel along geodesics of spacetime. Because these geodesics are curved by the presence of matter, an object's geodesic will curve inward toward a massive body. We observe this effect as gravitation. Light, too, travels along geodesics, and its path is bent and curved as it speeds through spacetime.