Portal:Astronomy/Featured/March 2005

An artist's impression of an accretion disc of a black hole

A black hole is a theoretical concentration of mass with a gravitational field so strong that its escape velocity exceeds the speed of light. This implies that nothing, not even light, can escape its gravity, hence the word "black". The term "black hole" is widespread, even though the theory does not refer to any hole in the usual sense. According to classical general relativity, no matter or information can flow from the interior of a black hole to an outside observer, although quantum mechanics may allow deviations from this strict rule. The existence of black holes in the universe is well-supported both theoretically and by astronomical observation; however, a minority of physicists dissent.