A mechanic is driving his friends, an engineer and a physicist, and the brakes go out heading downhill. The car speeds up out of control and they think they're all going to die. Luckily, the mechanic is able to slow the car down on the shoulder, stop, and they all get out and breathe a sigh of relief. The mechanic says, "Wow, I better check the break line and see what happened." The engineer pulls out a phone and replies, "Well, it was probably a manufacturing defect. Let me see if there was a recall on this particular model." "Whoa whoa whoa, folks," says the physicist. "You're jumping the gun. First, let's get the car to the top of the hill, start back down it, and see if the same thing happens a second time."