Name this Book

When this book first came out, it was only read by a handful of rather wealthy people. Now almost everyone has a copy, and many people read it regularly. You cannot buy it from a bookstore or borrow it from the library. Can you name this book? Click below for the answer.

It's a phone book.

This is a good example of an old riddle that has not aged well, so don't feel bad if you found it a bit tricky. Newer technology has rendered phone books practically useless, yet I still get one delivered to my house every year. In another generation or so, many people might not know what they were used for.

The Brodie Helmet

At the outbreak of World War I, none of the combatant nations provided steel helmets to their troops. Soldiers of most nations went into battle wearing cloth or leather hats that offered little protection from modern weapons. As a result, many soldiers suffered head injuries from exploding shrapnel.

In April of 1916, British soldiers began using a metal helmet in battle called the Brodie helmet, but authorities discovered that the proportion of head injuries then increased. Why should the incidence of head injuries increase when soldiers wore metal helmets rather than cloth caps? Click below to see the answer.

The number of recorded head injuries did increase after the introduction of the Brodie helmet, but the number of deaths decreased. Prior to the introduction of metal helmets, if a soldier were hit in the head with a piece of shrapnel, it would have likely killed him. This would have been recorded as a death, not a head injury. More head injuries were recorded after the helmets were introduced due to the simple fact that more soldiers were surviving them.

Panama Canal

A ship sailed through the Panama Canal going from west to east. When it exited the canal, it entered the Pacific Ocean. (The ship did not double back.) How can this be so? Click below to see the answer.

Normally when we think about the American continents, we think of the Pacific Ocean being to the west and the Atlantic Ocean to the east, but that isn't strictly the case. Panama is an isthmus that curves, and the Panama Canal was constructed so that it runs from the Caribbean Sea on the northwest end to the Pacific Ocean on the southeast. In the age of instant access to world maps, this "puzzle" is probably a lot easier to verify now than when the canal was originally built.

Rope Around the Earth

Suppose you tie a rope tightly around the Earth at the equator. (Assume the Earth is perfectly spherical, and that the surface is smooth so that the rope lies tight against the surface at all points.) Now suppose that you add an additional 6 feet to the length of the rope. How high off the surface would the rope lie? You could look up the Earth's circumference and do the math to come up with an exact answer, but can you quickly come up with an intuitive guess? (High enough to slide a piece of paper under? To wave your hand under? To walk under?) Click below to see a hint or the answer.

Hint: If I reversed the parameters and told you that I increased the length enough to raise the rope 6 feet from the surface in all directions, could you tell me how much was added to the length of the rope? (Given the formula for the circumference of a circle, C = 2πr, but not knowing the circumference of the Earth, can you come up with a guess?) Reversing that, can you come up with the answer to the original problem?

Answer: The first time they hear this puzzle, many people will try to do the math starting with the circumference of the Earth. That doesn't matter though. It's a property of any circle that if you increase the circumference by a fixed amount, the radius will change by that amount divided by 2π (because r = C/2π). The rope could be tied around a beach ball or a tennis ball and the answer would not change. So the exact answer to the problem is 0.95493 feet, but if you said "about 1 foot" you were right.

Voyageurs

I've been reading The Revenant by Michael Punke and came across the following few passages. The main character, Hugh Glass, is embarking on a canoe trip up the Missouri River with a group of French Canadian fur traders known as voyageurs.

...For the rest of their voyage, Glass manned not a paddle but an enormous sponge, constantly bailing water as it pooled on the bottom of the canoe.

It was a full-time job, since the bâtard leaked steadily. The canoe reminded Glass of a floating quilt. Its patchwork skin of birch bark was sewn together with wattope, the fine root of a pine tree. The seams were sealed with pine tar, reapplied constantly as leaks appeared. As birch had become more difficult to find, the voyageurs were forced to use other materials in their patching and plugging. Rawhide had been employed in several spots, stitched on and then slathered in gum. Glass was amazed at the fragility of the craft. A stiff kick would easily puncture the skin, and one of La Vierge's main tasks as steersman was the avoidance of lethal, floating debris. At least they benefited from the relatively docile flow of the fall season. The spring floods could send entire trees crashing downstream.

If you've ever maintained a large code base, you probably already see where I'm going with this. The constant patching and plugging of leaks, the fragility of the craft, one man constantly bailing out water while several others row the boat guided by a steersman. These elements all remind me of several large software projects I've been on.  The passage continues.

There was an upside to the bâtard's shortcomings. If the vessel was frail, it was also light, an important consideration as they labored against the current. Glass came quickly to understand the odd affection of voyageurs for their craft. It was a marriage of sorts, a partnership between the men who propelled the boat and the boat that propelled the men. Each relied upon the other. The voyageurs spent half their time complaining bitterly about the manifold ails of the craft, and half their time nursing them tenderly.

This reminds me not only of the relationship programmers have with our code, but also of the relationship we have with our tools. How much time do we spend complaining about an IDE or a framework? How much time configuring them? But after we've gotten comfortable using them, most of us will strongly resist switching to a new one. Finally...

They took great pride in the appearance of the bâtard, dressing it in jaunty plumes and bright paint. On the high prow they had painted a stag's head, its antlers tilted challengingly toward the flowing water. (On the stern, La Vierge had painted the animal's ass.)

This final bit surprises me the most, but in a way I suppose it shouldn't. I don't know much about boating, but I do know that you should fix the leaks in your boat before you bother to decorate it. But that isn't how we always approach software development, is it? I've seen people spend plenty of time refactoring and cleaning code that didn't really need to change, or adding test cases just to get a higher percentage in test coverage. At times I've been guilty of this myself. I guess it's worth it to ask yourself, before you make a change to your code, am I fixing a leak, or am I just painting a stag's ass on this canoe?