OK, so my 15 year old daughter just asked me a tricky question...
None of those easy parenting questions like "where to babies come from, Daddy?"*, it was "how can the Internet run out, Daddy?"
Fortunately I have spent all morning making slides to explain all of this to Reading University, and given that it is pitched at the level of university students, I gave her the talk.
I think she got the gist of it quite well :-)
[*OK I know, bad example for a 15 year old]