Time

People are very attached to time. They don't like it when you take it away from them. They value it, measure it, parcel it out, and are very upset when they run out of it. "An atomic clock defines time," they'll say. "That proves time exists. Besides, I have a wedding to go to on Saturday, and I haven't even bought a gift yet." But an atomic clock only measures time, the way a ruler does: by sitting next to it and providing markings that show regular intervals in parallel. The oscillation of a crystal is a wiggly line.