What is proposed as evidence that supports the big bang theory?

That's not the way it works.

Real scientists don't gather evidence to support a theory that they made up.

Real scientists build a theory to explain the evidence that they observed.

The so-called "Big Bang" theory is the best explanation ... so far ... of:

-- the observed Cosmic Background radiation,

-- the observed probable expansion of the universe (not "proved"),

-- the observed probable existence of "dark matter" (not "proved"),

-- the observed success of predictions that come from standard theories of fundamental particles, and

-- the observed success of predictions (like GPS) that come from Einstein's general theory of relativity.  

BUT ! If you come up with a better explanation tomorrow ... one that explains the observed evidence more accurately, and makes more accurate predictions of things that we can observe or test ... then the "Big Bang" theory will go out the window, and the scientific world will adopt the "Sid4067" theory for the same evidence that we already have.

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