Name three forms of evidence used to support the big bang theory.

The three forms of evidence used to support the "Big Bang theory" are as below:

The Red Shift. Microwave background radiation. The abundance of elements.

Explanation:

It is observed that the galaxies in the universe are "moving away" from each other. It is concluded from this distancing of the galaxies that they must have originated from a single source. The Big Bang Model put forward by Georges Lemaitre, the one who proposed the Big Bang theory, suggested that there must have been a microwave background radiation during the Big Bang, which was later discovered to be existent in the outer space. The abundance of elements in the lithosphere, atmosphere and in the outer space also points towards the possible occurrence of the Big Bang.