How do we know the universe is expanding using redshift?

2 Answers
Nov 4, 2017

We are seeing more things as red than blue compared to before.


So based on what I can remember from last year, things that are closer to us give us a more compressed wave length of light making it a higher frequency. That would make it look more blue. However as it shifts further away, the wave length becomes less compressed and a lower frequency. That would make it look more red (lower frequency is red, higher frequency is blue). So if things are becoming more red and less blue, that would mean it is moving away from us and if everything is moving away from us, that means the universe is expanding.

p.s. I may have inverted some of the things as in it might be the other way around

Nov 5, 2017

The red shift is a result of the doppler affect. Objects moving away shift to the red.


When Hubble discovered the red shift in the universe it created a siemic shift in the world view of the cosmos.

The red shift is a result of light waves being spread out as the waves move away from the observer. The spreading out of the waves increases the wave length observed. Red is the longest wave length in the visible spectrum. So the red shift indicated that the universe is moving away from the observers on the earth.

The conclusion from Hubble's observations of the red shift is that the universe is expanded outward from some beginning point in time. This conclusion is consistent with the observations of the red shift through the universe, and the physics of the doppler effect.

Before Hubble scientists believed that the present universe was eternal existing in a steady state. Hubble's observations destroyed this world view. The conclusion is that the present universe had a beginning and matter and energy are not eternal