This theory states that the entire universe began as a small, hot, energy point that expanded over billions of years into the universe we see today. This theory is supported by:
- Cosmic background radiation left over from the big bang.
- Galaxies are still moving apart.
- If the big bang occurred the way scientists think it did, they predicted that there would be a certain amount of helium out in space. In 1995 a space shuttle mission measured that level of helium in space.
