Question: is it true that the big-bang really happened?

Edward Bovill answered on 12 Mar 2013:

While the theory of the Big Bang can not currently be proven as the absolute truth, all current evidence seems to state that it is the most likely way that our universe started.

There are several observations that support the Big bang theory. One of which is that all the galaxies are getting further and further away from each other all the time.

Imagine you have a deflated balloon and you draw some little dots all over it. These dots represent the galaxies and the balloon represents the universe. As you blow up the balloon, the dots get further and further apart, just like the galaxies are getting further apart as the universe expands. Scientists have measured the speeds of a lot of galaxies and they are all moving away from us, and the further they are away from us the faster they are moving! If you go back in time, all the galaxies look like they started out at exactly the same point (about 14 billion years ago).

When the Big Bang happened, all the matter in the universe exploded out from this one point, forming all the stars and galaxies, and they are still moving away from this starting point now.