Astronomical joke

Two astrophysicists are discussing their research in a bar one evening when a drunk who has been sitting and listening in at the next seat turns and says, in a very worried voice, “What was that you just said!?”

“We were discussion stellar evolution, and I said to my colleague here that the Sun would run out of nuclear fuel and turn into a red giant star in about 5 billion years, possibly melting the Earth.”

“Whew!!,” says the drunk, “You really had me worried. I thought you said 5 million.”