Question

what is big bang theory is and what evidence scientists have that it occurred​

Answer 1

Answer:

The Big Bang theory predicts how much of each element should have been made in the early universe, and what we see in very distant galaxies and old stars is just right. You cannot look in new stars, like the Sun, for this evidence, because they contain elements that were created in previous generations of stars.

EVIDENCE : gravitational waves:

Astrophysicists at the Harvard-Smithsonian Center have observed gravitational waves — the first ever direct evidence of the Big Bang, the theory that the entire universe sprung into existence from a tiny spot in the universe 13.8 billion years ago