The property of spacetime that causes freely falling particles that are initially moving along parallel world lines to subsequently move together or apart. Spacetime curvature and tidal gravity are different names for the same thing. A diagram with time plotted upward and space plotted horizontally. Einstein's laws of physics in the absence of gravity. Gravitational accelerations that squeeze objects along some directions and stretch them along others.
Tidal gravity produced by the moon and sun is responsible for the tides on the Earth's oceans.
A device for traveling backward in time. The path of an object through spacetime or through a spacetime diagram.