The very concept of infinity is challenged by some paradoxes that deal with the idea. If you have a printer that prints a page with a 1 on it in a minute, then prints a 2 in 30 seconds, then a 1 in 15, then a 2 in 7.5 etc. what number does it print last when 2 minutes are up? Sure, the printer isn't physically possible, but htink about it: on one hand you have the idea of infinity, that you can't reach the end of. On the other hand you have a finite amount of time with very discreet numbers. You surely have to have one or the other - a 1 or a 2 at the end of the second minute.The problem arises like in the guitar string problem of ftting a theory of the infinite onto a physical finite thing. Still, it is fun to get your head around.