# What are the pieces of evidence that universe is expanding? [duplicate]

Do we have any other evidence other than red shift? Is anyone trying to disapprove inflation? Also, can red shift occur because of large distance, not only because two objects are going farther from each other?

• Commented Mar 20, 2016 at 1:00

## 1 Answer

The evidence is in the red shift of the light received from galaxies. Farther the galaxies, more is the red shift. Red shift is caused if source of light is moving away from us.

How far a galaxy is, is figured with the help of supernova (a standard candle). Scientists know how bright the supernova of a certain class should be depending upon how far it is.

1. The brightness of Supernova gives the distance

2. Red shift of supernova light and matching red shift of galaxy light tells that galaxy is at same distance as the supernova.

3. Farther the distance, more red shift confirms that farther galaxies are moving away faster indicating universe is not only expanding, the expansion is accelerating.

There are bunch of documentaries on youtube that explain this.

• Your answer raises many other questions. Are all supernova equally bright? Equally, I mean producing same intensity of light, so that with an increase in distance, intensity decreases. Commented Mar 20, 2016 at 11:25
• My next question is about your point 2 and 3. What will happen when A object is at distance(x) to object B and also A object is at distance (y) to object C and x < y and object B and C are at rest when seen from frame of reference to A. Will there be red shift? (is it determined experimentally) Commented Mar 20, 2016 at 11:38
• I wrote the evidence used for the expansion of universe. For validity, and explanation of accuracy, please do some internet searching of the topic, and read about it. Wevelength shift is well established effect related to moving source, and is a topic in itself. The supernova are classified and there is one class of supernova that gives same brightness at same distances. There is a lot of literature on this subject on the internet.
– kpv
Commented Mar 20, 2016 at 16:34
• Ya, all literature are mathematical based and don't give any intuitive understanding of the subject. Commented Mar 22, 2016 at 15:02
• @user1566713: Youtube documentaries on dark energy explain it, Look for Alex Filipenko for example.
– kpv
Commented Mar 22, 2016 at 17:22