Relativistic Doppler Effect

The relativistic Doppler effect describes how the frequency of light or other waves changes when the source and observer move relative to each other at speeds close to the speed of light. Unlike everyday Doppler shifts (like sound from a passing siren), relativistic effects also account for Einstein's theory of relativity, causing phenomena like time dilation. When the source moves toward you, the waves are compressed, increasing their frequency (blueshift); moving away stretches the waves, lowering their frequency (redshift). This combined effect influences the observed color and wavelength of distant astronomical objects, revealing their motion and speed relative to us.