General relativity
From Simple English Wikipedia, the free encyclopedia
General relativity is the physics of the very large.
The earth is small, and our sun is far away, so anything an average person does can be described by the much simpler Newtonian physics. When you start dealing with things that are very large, like stars and galaxies, things start to move and interact differently. The science of how this works is called general relativity.
General relativity is a theory of space and time created by Albert Einstein and published in 1915. The central idea of general relativity is that space and time are two aspects of something called spacetime, which is curved in the presence of matter, energy, and momentum, in a way that Einstein wrote down in the Einstein Field Equations.
In general relativity, freefall is inertial motion instead of being at rest on a massive body such as the Earth, as described by the equivalence principle.
General relativity has made many successful predictions. These include:
- The bending of light as it passes the Sun by twice the Newtonian value for an object traveling at the speed of light. This was confirmed by Eddington in 1919, and the announcement forced scientists to take general relativity seriously.
- The perihelion of the planet Mercury advances more than is expected under Newtonian physics. General relativity accounts for the difference between what is seen and what is expected without it.
- The gravitational redshift effect, by which the wavelength of light increases as it moves away from a massive object. This was confirmed by the Pound-Rebka experiment.
- The Shapiro effect, under which light appears to slow down as it passes close to a massive object. This was first confirmed in the 1960s for space probes headed towards the planet Venus.
