The year is 1714. You are in a dark Spanish prison. You wake up to find yourself tied to a table with ropes. In the darkness you hear a rhythmic swishing sound-something going back and forth, back and forth. Eventually your eyes get accustomed to the dark and see that the source of the sound is a sharp bade at the end of a long pendulum that’s swinging back and forth over your body. With each sweep it gets a little lower-and a little closer to your chest. You note how long it takes between those swishes: exactly 7 seconds. And with each swish, the blade drops 1 inch lower. The last passing was only 15 inches above your chest. It won’t be much longer before the blade slices right through you. Should you scream for help? That would probably just summon a guard, who would run through with a sword then and there. But wait! You see a rat by your arms and he’s gnawing at the rope that binds you to the table. In fact, he has only 1 minute to go before he gnaws through it all the way. When he does that, you can get free! Will the rat chew through the rope before or after the blade has slashed through your chest? How much time do you have exactly?