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Relativistic Doppler effect
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Frequency shift for light.
f' = f√((1−β)/(1+β))f' = f√((1 − β)/(1 + β)) for approach/recession along the line of sight. A transverse Doppler shift exists, due to time dilation alone.
A galaxy at 0.1c shifts wavelengths by 10.5%.
Can't be explained by classical Doppler.
In more detail
The relativistic Doppler effect includes time dilation, so the observed frequency shift for light depends on the relative velocity and angle. It reduces to the classical result at low speeds.
Real-world uses
- Astronomers measure redshifts of distant galaxies with relativistic Doppler formulas.
- Radar speed measurements at high speeds use relativistic corrections.
- Astronomers use the relativistic Doppler formula to measure the velocity of distant jets and galaxies at high speed.
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Frequently asked questions
How does it differ from the classical Doppler effect?
It depends on time dilation, so it is symmetric between source and observer.
Does transverse motion shift frequency?
Yes, due to time dilation, even when the motion is perpendicular to the line of sight.
How is the relativistic Doppler shift different?
It includes the effect of time dilation, so it differs from the classical formula at high speeds.
Related topics in Relativity
Energy–momentum relation · Relativistic kinetic energy · Massless particles · Aberration of light · Four-vectors · Relativistic collisions