Incredibly large numbers.. Seti at Home
I just thought this issue with scale was kind of cool. Lifted from SETI@Home.
There’s a third type of incorrect result that occurs, too. Sometimes, very rarely, a computer will get the wrong answer to a calculation for no apparent reason. This appears to happen about one out of every 3,000,000,000,000,000,000 calculations. If you let your computer run SETI@home for a thousand years, it would get the wrong answer once. (Of course by then your computer would have failed for some other reason). But since SETI@home gets a thousand years of CPU time every day, we see one or more of these failures per day.