Newton's conception of time as being universal, with a unique, universally agreed upon notion of simultaneity of events and a unique, universally agreed upon time interval between [..]

Stephen Hawking's conjecture that the laws of physics do not allow time machines.

The property of space or spacetime that makes it violate Euclid's or Minkowski's notions of geometry; that is, the property that enables straight lines that are initially p [..]

A point in spacetime; that is, a location in space at a specific moment of time. Alternatively, something that happens at a point in spacetime, for example, the explosion of a firecracker.

Material that has a negative average energy density, as measured by someone moving through it at nearly the speed of light.

Something that is distributed continuously and smoothly in space. Examples are the electric field, the magnetic field, the curvature of spacetime, and a gravitational wave.

An object on which no forces act except gravity.

Einstein's laws of physics in which gravity is described by a curvature of spacetime.

A straight line in a curved space or curved spacetime. On the Earth's surface the geodesics are the great circles.

The slowing of the flow of time near a gravitating body.