Scientists do not yet know what came before the big bang but there are some theories. Some believe that before the big bang the universe was just a big ball of matter and light and energy. Another theory is the big bang started within the black hole of another universe.
Another possibility is that the folds in space and time within the universe mean there is no beginning and end to the universe, just like a circle. It can be difficult to imagine, much like the rest of the universe, but time may be something that does not exist the way we think of it on earth.
