The other day I was wondering if as the universe is infinite and you can say that every single point in it is the centre of the universe, or that there is no centre for the same matter. Since you are not able to set up a centre in earth's surface. Is then earth's surface infinite? When you talk about straights in an x and y axis, you notice that they are endless, and therefore, they have infinite points. You cannot set up a centre in that line because it is infinite. Actually my question is also applicable to a sphere such as a regular tennis ball. What do you think?