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What is general relativity?

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Quick answer

General relativity is Einstein's 1915 theory of gravity, which describes gravity not as a force but as the curving of space and time by mass and energy. Massive objects bend spacetime, and other objects move along those curves — which we feel as gravity.

Key things to understand

  1. Mass and energy curve the fabric of spacetime; objects follow the straightest path through that curved space.
  2. What we experience as gravitational 'pull' is really this curvature guiding motion.
  3. It predicts light bends around massive objects (gravitational lensing), confirmed during a 1919 eclipse.
  4. It explains black holes, the expansion of the universe, and tiny shifts in planetary orbits.
  5. It extends special relativity to include gravity and accelerating frames.

People also ask

How is general relativity different from Newton's gravity?
Newton described gravity as a force between masses; Einstein showed it's the curvature of spacetime. Einstein's version is more accurate, especially near very massive objects.
What is gravitational lensing?
Massive objects bend the path of light passing nearby, so distant galaxies can appear distorted or magnified — direct evidence that mass curves spacetime.
Does GPS rely on general relativity?
Yes. Clocks on satellites run slightly faster due to weaker gravity up there; GPS corrects for this relativistic effect to pinpoint locations accurately.