Think about the starting positions on a track. The track is divided into lanes and each player is set backwards based on their lane by a fixed distance, despit

Think about the starting positions on a track. The track is divided into lanes and each player is set backwards based on their lane by a fixed distance, despite the fact the finish line is in the same position. This is because of the curvature of the track - if everyone started at the same "line" across all lanes, the runners at the outer lanes would be running a further distance than those on the inner lanes! Gravity does the same thing to time itself. The curvature is not of a track but of spacetime. In Gravity, the main character starts at an inner lane and his daughter at an outer one - but the starting line is the same across all lanes. Gravity bends spacetime, such that the inner lane is shorter than the outer lane (in terms of distance in time). So when they ultimately arrive at the finish line, the daughter has traversed a longer path in the time dimension than her father.