Special Relativity has a wide range of consequences which have been experimentally verified, including counter-intuitive ones such as length contraction, time dilation and relativity of simultaneity, contradicting the classical notion that the duration of the time interval between two events is equal for all observers.

Caption: A simulated black hole of ten solar masses as seen from a distance of 600 kilometers with the Milky Way in the background.

Einstein's theory has important astrophysical implications. It points towards the existence of black holes - regions of space in which space and time are distorted in such a way that nothing, not even light, can escape - as an end-state for massive stars. There is evidence that such stellar black holes as well as more massive varieties of black hole are responsible for the intense radiation emitted by certain types of astronomical objects such as active galactic nuclei or microquasars. The bending of light by gravity can lead to the phenomenon of gravitational lensing, where multiple images of the same distant astronomical object are visible in the sky. General Relativity also predicts the existence of gravitational waves, which have since been measured indirectly; a direct measurement is the aim of projects such as LIGO. In addition, General Relativity is the basis of current cosmological models of a consistently expanding universe.