About how many billion years ago did the big bang occur? a. 5 b. 11 c. 14 d. 19 what is a scientific theory? a. a guess b. a final conclusion that will never be altered or improved c. an idea that is supported by and explains a wide variety of facts d. a hypothesis which evidence proves the universe began with the big bang? a. craters on the moon left by universal forces b. leftover energy in the universe from the event c. the force of gravity d. the existence of atoms