My brother and I were rappelling the nearly vertical face of Prince of Darkness at Red Rocks. When we pulled the ropes they sailed past us and we heard a loud whip-like crack. Upon examination we discovered that the end of our new rope had exploded into tatters. What's the best procedure for pulling ropes on multiple hanging rappels? What should we do about our rope?

In 1877 the Austrian physicist Ernst Mach laid down the principles of supersonics, or objects traveling greater than the speed of sound, later called Mach 1, which is 761 miles per hour. Mach also described the sound effects created by supersonic objects. Your outing perfectly illustrated his theorems. When you pulled your cord, the tail of your new rope cascaded down in a loop, rather than falling straight. When the loop straightened as a result of the rope coming taut on the anchor, the tail accelerated at such a speed it created a vacuum in space. The cracking sound you heard was made by air rushing back into the vacuum, creating a mini sonic boom that would have made Mach yelp his safe word. The cracking of a bullwhip is identical to what your rope experienced, and, as anyone in a back leather mask can attest, is not to be trifled with.

Unfortunately, there is nothing you can do to prevent a repeat performance. The instant the tail of your rope pulls through the upper anchor, it becomes as uncontrollable as fission. Best to just duck and cover.

Don't fret, your rope is fine, it just needs a little surgery to get up to snuff. Tightly wrap a piece of athletic tape around the rope a few inches down from the exploded end. With sharp scissors or a knife, cut through the tape, then cauterize the fresh rope end with the hot flame from a Zippo. Next!