Talk:General relativity/WIP

This is the general relativity sandbox (WIP, Work in Progress). At the moment, there is a cooperative effort to rework the main article; this is a place to store major changes until consensus has been reached. We do not need to make this a complete parallel article; it should be perfectly alright to start moving sections or subsections over to the main article once we have agreed on them. (Once we do, it should be noted here that the section has been moved, so no-one tries to start a new version here!)

Please use Harvard referencing style here and in any references you add to the main article! (If you don't know how this works, there's a helpful starter on the gr talk page, here).

General relativity (GR) or the General theory of relativity (GTR) is the geometric theory of gravitation published by Albert Einstein in 1915/16. It unifies special relativity and Newton's law of universal gravitation, resulting in a theory in which gravity is a property of the geometry of space and time; in particular, the curvature of space-time is directly related to the mass-energy and momentum of whatever matter is present through the Einstein field equations a system of partial differential equations.

General relativity predicts a number of novel effects relating to the passage of time, the geometry of space, the motion of bodies in free fall and the propagation of light, such as gravitational time dilation, the gravitational redshift of light, and the gravitational time delay; in numerous observations and experiments to date, its predictions have been confirmed. Although general relativity is not the only relativistic theory of gravity, it is the simplest such theory that is consistent with the experimental data. However, a number of open questions remain: the most fundamental is how general relativity can be reconciled with the laws of quantum physics to produce a complete and self-consistent theory of quantum gravity.

The theory also has a number of astrophysical applications. It predicts black holes as an end-state for massive stars and there is evidence that, indeed, such black holes 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 curious phenomenon of multiple images of one and the same astronomical object being visible in the sky, an effect that is called gravitational lensing and which has spawned an active new branch of astronomy. General relativity also predicts the existence of gravitational waves, which have been measured, albeit indirectly, and it is the basis of current cosmological models of an expanding universe.