What is now in the position of the big bang?
If we were able to build a spaceship now, that was able to get to the universe where the Big Bang occurred, what would we find there now? Can we find the point where the Big Bang happened?
Chris: That's just not possible!
Dave: As far as we know, when the Big Bang happened, everything was not only closer together but space was smaller. When we say the universe was really, really tiny - maybe less than the size of an atom - that means all the space is not just all the particles close together. Literally, all of space was smaller as well.
In some senses we are, at the moment, where the Big Bang happened, because this bit of space we're in now was at the Big Bang - space has just expanded hugely since.