Wait what? (1+2+3+4+...

[eliasfrost]

But how can something approach infinity, infinity is not a number it's a concept. Can you please explain from the very grounds up how exactly infinity can be used to calculate something, how is it defined (because it has to be in order to be used, otherwise it's just hocus pocus and make-believe) and how can you be so sure that the result is in fact true when a part of the calculation is undefined, that is, have no value?

No, not that it wasn't true before we "discovered" it, but that we didn't know it was applicable before we invented it.