For example, the further a galaxy is from us, the more red it is.
In: Planetary Science
Say you’re releasing a pulse of light every 10 seconds. If you’re stationary, I’ll see a pulse of light every ten seconds – but if you’re moving away from me at 10% of the speed of light I’ll see a pulse every 11 seconds, because each pulse has to travel a little further to reach me than the one before it.
The colour of light is based on how often it peaks, with more common peaks being more blue, and less common being more red – it’s not exactly pulses, it’s a wave, but you can think of the peaks of the waves as pulses and get a reasonable understanding for this issue – so if a galaxy is moving away from us, the colour gets redder.
As it turns out, the further away from us a galaxy is the faster it’s moving away from us – so further away galaxies have all their light redshifted.
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