How was the Earth made?
How was the Earth made? That's what Kate in Glasgow and Delyth in Wales wanted to know.
A very Big Question indeed, but luckily we have a very big name in science to answer it.
Brian Cox took time out of filming and looking into the depths of space to answer some big space questions for us, including this one.
Well strap in to the Newsround space-ship and let's find out!
Check out this other space-related Big Questions too: How old is the universe?