Related topics: black holes

World celebrates centenary of confirmation of relativity

Celebrations are underway across the globe to commemorate 100 years since a UK-led expedition confirmed Einstein's general theory of relativity. The theory fundamentally changed our understanding of physics and astronomy, ...

Clocks, gravity, and the limits of relativity

The International Space Station will host the most precise clocks ever to leave Earth. Accurate to a second in 300 million years the clocks will push the measurement of time to test the limits of the theory of relativity ...

DIY gravitational waves with 'BlackHoles@Home'

Researchers hoping to better interpret data from the detection of gravitational waves generated by the collision of binary black holes are turning to the public for help.

First black hole photo confirms Einstein's theory of relativity

Black holes are long-time superstars of science fiction. But their Hollywood fame is a little strange given that no-one has ever actually seen one – at least, until now. If you needed to see to believe, then thank the Event ...

Black holes: picturing the heart of darkness

Astronomers are poised Wednesday to unveil the first direct image of a black hole and the surrounding whirlwind of white-hot gas and plasma inexorably drawn by gravity into its ravenous maw, along with the light they generate.

A new Einstein cross is discovered

This study, which has combined images from the Hubble Space Telescope with spectroscopic observations from the GTC, has confirmed the existence of a new example of a gravitational lens, a phenomenon predicted by Albert Einstein's ...

Mapping historical changes in dark matter

Combining Einstein's theory of relativity with one of the most powerful telescopes in the world has helped an international team of researchers measure where and how dark matter structures grow in the universe. Their analysis ...

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General relativity

General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics. It unifies special relativity and Newton's law of universal gravitation, and describes gravity as a geometric property of space and time, or spacetime. In particular, the curvature of spacetime is directly related to the four-momentum (mass-energy and linear momentum) of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of partial differential equations.

Many predictions of general relativity differ significantly from those of classical physics, especially concerning the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light. Examples of such differences include gravitational time dilation, the gravitational redshift of light, and the gravitational time delay. General relativity's predictions have been confirmed in all observations and experiments to date. Although general relativity is not the only relativistic theory of gravity, it is the simplest theory that is consistent with experimental data. However, unanswered questions remain, the most fundamental being how general relativity can be reconciled with the laws of quantum physics to produce a complete and self-consistent theory of quantum gravity.

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.

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