Question: what was the big bang and how did it start

Louise Dash answered on 24 Jun 2010:

The “big bang” is the best theory scientists have come up with for how our universe was formed. It says that it was formed out of a “singularity” with infinite density about 13.7 billion years ago, and has been expanding ever since. There’s a lot of evidence to support this – as scientists have observed that galaxies are moving away from each other (so the universe must be expanding) and something called “cosmic background radiation” which is a faint glow coming from all directions that we think is a remnant from the big bang itself.