The size of our world

This is interesting to me because i have always liked space just because of so much unknown and the vastness of it, also the sizes of things all of which are hard to really get a grip of how big they really are. As big as earth may seem it is a dot compared to other planets and stars. I think this would interest some of my classmates just to see the differents in size compared to other planets and stars. For sources they state that it is unknown.