If the big bang is true how did it start?

Answer 1

There are many theories but no one knows for certain. But that doesn't mean that theory of the big bang didn't happen, it just means we don't know for sure what created the energy. Because something is theorized this does not mean that every possible question about the theory is instantly cleared up. The evidence suggesting a "Big Bang" (a derogatory term, by the way, used by scientists who thought the idea prepostrous) includes the observed fact that the universe is expanding. Since the universe is expanding, we wonder what conditions were like at a previous time when extrapolations suggest that everything started out in one place. Anyone is free to interpret the observations differently, and to theorize what got the expansion started.