Makes ya feel kinda small, donit?

In Astronomy 101, the prof says, "The sun will have used up all its fuel about five to seven billion years from now, and when that happens, it will swell into a red giant, expanding well beyond the orbit of earth before it finally collapses into a white dwarf."
A hand goes up in the back row.
"Yes?" says the prof. "You have a question.?"
"Yes. How long did you say it would be before that happens?"
"Five to seven billion years."
"Oh, thank God! I thought you said million!!"

Don Firth