Einstein explained · 1907
Gravitational Redshift
Gravitational redshift means that light changes frequency when it moves through a gravitational field.
stronger gravity → slower clocks
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What it means
Light moving away from a strong gravitational field is observed at a lower frequency. The effect is closely connected with the fact that clocks deeper in gravity run more slowly.
Einstein's contribution
Einstein predicted a gravitational frequency shift while developing the equivalence principle. It showed that gravity affects both light and the passage of time.
Why it matters
Gravitational redshift has been measured experimentally and must be allowed for in precision clocks and satellite navigation systems.
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Einstein’s key theories and contributions
1905Special RelativityHow motion changes measurements of space and time while the speed of light stays constant.Read explainer →1905Mass–Energy EquivalenceWhy mass and energy are connected by Einstein's famous relation E = mc².Read explainer →1907Equivalence PrincipleWhy free fall and acceleration gave Einstein the starting point for a new theory of gravity.Read explainer →1916–1918Gravitational WavesHow changing masses can send ripples through spacetime at the speed of light.Read explainer →1915General RelativityHow Einstein described gravity as curved spacetime shaped by matter and energy.Read explainer →1916–1917Quantum Theory of RadiationHow atoms absorb and emit light, including Einstein's prediction of stimulated emission.Read explainer →1917Cosmological ConstantWhy Einstein added Λ to his gravity equations and how the term returned in modern cosmology.Read explainer →