How would you explain universe expansion and its relation to red shift?
Principle of Doppler shift is based on sound..It can also applied to Light as both are waves.
When a whistling train is moving away from you the sound waves gets elongated and when it comes to wards you the sound waves get compressed,..When a galaxy is moving away from you its light get elongated.This is called red shift ..The spectral lines are moving to wards red end of the light spectrum..So a red shift shows that the object is moving away from you. In 1909 s Ediwin Hubble found that the spectrum of galaxies are red shifted are moving away from us. .REad about Hubblelaw in this link.From wikipedia"Hubble's brilliant observation was that the red shift of galaxies was directly proportional to the distance of the galaxy from earth. That meant that things farther away from Earth were moving away faster. In other words, the universe must be expanding. He announced his finding in 1929." picture credit commons wikimedia.Edu.
The red shift is evidence that the universe is expanding.
Hubble discovered that the vast majority of objects in the universe exhibit a red shift in the frequency of light waves. This is because of the doppler effect.
Objects that are moving toward an observer exhibit a blue shift as the the light waves are compressed and moved closer together.
Objects that are moving away from an observer exhibit a red shift as the light waves are stretched and are spread further apart. Red is the longer wave length, so objects moving away from an observer are seen as moving to the red part of the spectrum.
Hubble discovered the red shift doppler effect and changed the way scientists view the Universe. The red shift doppler effect is strong evidence that the universe is expanding from a point of origin. The concept of an expanding universe destroyed the world view of a steady state universe that had always existed.