Imagine: You wake up inside a room with no windows and one locked door (you checked). You cannot see outside. Looking around you see a table with a number of items on it: a desk lamp (plugged in and turned on), a tennis ball, a bunch of string, a pitcher of water and a cup, a candle, a box of matches, and a music player with headphones. A skateboard and a wooden stool are also in the room. The music player has a sign on it saying “Turn on for instructions,” so you do. You are told that you are in a specially designed vibration-proof and noise-proof train car on a set of straight and level train tracks. Your task is to use one or more of the items in the room, perhaps in combination with each other, to determine whether the train car is stationary or is moving on the tracks. There is a thirty-minute time limit for your test (or tests), and destroying or modifying the walls, floor, or ceiling of the car is not permitted.