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Redshift/Blueshift-The Doppler Effect

Redshift aka MOVING AWAY

Blueshift aka MOVING CLOSER

Also known as the Doppler effect

It’s name comes from physicist Christian Doppler who first recognized the change in sound waves when moving closer or further in 1842.
It was tested by Buys Ballot in 1845 by using a group of musicians playing a note on a train.

When sound moves further away like an ambulance driving past you the sound waves become longer due to more space being present between you and the ambulance.

Blue shifts when the ambulance is approaching the sound waves (wavelength) become more “squished” together which cause the sound waves (and wavelength) to become shorter.

This also can apply to LIGHT.

Like measuring the distance of a star and also this is what made astronomers realize that the universe was EXPANDING-and rapidly.
By measuring the change in brightness of a star, galaxy, supernova-astronomers can determine if objects are moving towards or away.
Just like the theory of dark energy and the Hubble constant.

Astronomers found that the observed brightness of a Type Ia supernova was red-shifting much more than estimated. This showed that it was moving away much faster.

This showed that the universe was expanding much faster.
And this leads into other things like how the theory of dark energy was derived.
But for now this is Redshift vs Blueshift…