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Gravitational redshift
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Light climbing out of a gravity well loses energy.
Photons climbing out of a gravity well lose energy: Δf/f = −GM/(rc²) = −gh/c². Verified by Pound–Rebka (1959).
Light from white dwarfs.
Same effect as gravitational time dilation.
In more detail
Light climbing out of a gravitational well loses energy and is shifted to lower frequency, a gravitational redshift. This was measured by Pound and Rebka in 1959.
Real-world uses
- Gravitational redshift is observed for white dwarfs and neutron stars.
- It is tested with precision atomic clocks.
- Astronomers measure the gravitational redshift of light from white dwarfs and neutron stars to test general relativity.
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Frequently asked questions
What is gravitational redshift?
The shift of light to longer wavelengths as it climbs out of a gravitational field.
Who measured it on Earth?
Pound and Rebka, in 1959, using the Mössbauer effect.
Why does light lose energy climbing out of gravity?
It must do work against gravity, and the energy loss shows up as a longer wavelength.
Related topics in Relativity
Tachyons · Equivalence principle · Gravitational time dilation · GPS and relativity · Curved spacetime · Einstein field equations