system
Given the following post, respond as if you're commenting on Reddit:
human
If the speed of light is constant, how does Red Shift happen?

The speed of light is always constant, regardless of the position and relative speed of the observer. In that case how come light is subject to the Doppler effect and gives us Red Shift?
gpt
The red shift is a shift in wavelength, not a shift in speed. Speed and wavelength are entirely different properties. They are related according to the equation:

frequency = speed/wavelength

Since the speed is constant in all frames, an increase in the wavelength (a redshift) must be accompanied by a decrease in the frequency.

The Doppler shift makes the most sense if you think of light as a wave. When a source is traveling away from you, each wave peak emitted at subsequently later moments in time is emitted at farther and farther away points in space. Therefore, the wave peaks that reach you must be farther apart, i.e. the wavelength has increased. But each individual wave peak still travels towards you at the same speed. People often think the Doppler shift should change the speed because they are picturing photons as literal little balls being shot out of a moving cannon, which is a false picture.