Question: i dont understand how when the big bang happened it expanded into space time but how can it have expandedd if there was nothing before the big bang for it to expand it into. Also, how can there have been nothing before the big bang? there must have been something for thwere to be nothing??

Pete Edwards answered on 20 Jun 2010:

This is a great question – if there was nothing before the big bang then what went bang?
We believe that the whole of the fabric of our universe, both it’s space AND time began in the big bang. So the universe’s clock began ticking when it was born. Not only was there no space before the big bang, there was also no time. So the question of what happened before the big bang has no meaning for us – there was no before!
The idea of something coming from nothing is very difficult for us to come to terms with. But if we could build an infinitely powerful microscope and look at the space around us, we would see things popping in and out of existence all the time – something coming from nothing and disappearing again! The real problem we have to explain with the big bang is why the universe didn’t disappear very quickly.
Some cosmologists think the universe will ultimately vanish, so maybe we really will end up with nothing again and we are just worrying about the length of time this takes………