My guess is that you haven’t spent a whole lot of time wondering what would happen if you pitched a baseball at 90 percent of the speed of light. I haven’t either.
But that’s okay, because Randall Munroe has figured it out and explained it really clearly in his book What If?.
It’s a collection of some of his favorite posts from one of the two blogs he keeps. His first blog, XKCD, which he’s also turned into a book, is made up of cartoons he draws making fun of things—mostly scientists and computers, but lots of other things too. There’s one about scientists holding a press conference to reveal their discovery that life is arsenic-based. They research press conferences and find out that sometimes it’s good to serve food that’s related to the subject of the conference. The last panel is all the reporters dead on the floor because they ate arsenic. It’s that kind of humor, which not everybody loves, but I do.
What If? may not be quite as funny as XKCD, but it’s a lot more interesting. The subtitle of the book is “Serious Scientific Answers to Absurd Hypothetical Questions,” and that’s exactly what it is. People write Munroe with questions that range over all fields of science: physics, chemistry, biology. Questions like, “From what height would you need to drop a steak for it to be cooked when it hit the ground?” The answer, it turns out, is “high enough that it would disintegrate before it hit the ground.” Another question: “What would happen if you made a periodic table out of cube-shaped bricks, where each brick was made of the corresponding element?” to which the answer is, essentially, the human race would be wiped out. Munroe’s explanations are funny, too—he’ll use giraffes as a unit of height measurement, and draw pictures of ten giraffes standing on top of each other.
Nevertheless, the explanations are scientifically valid. And they’re very well researched, with citations of obscure papers like “Sexual Cannibalism in Orb-Weaving Spiders: An Economic Model” (actually, that one is from the website, but I assume it’ll make it into the sequel, which I hope will be called What Iffer. Or the next one, What If? Strikes Back). He verifies his facts by calling expert scientists all over the world, and I have to imagine those conversations are amazing.
The reason Munroe’s approach is a great way to learn about science is that he takes ideas that everybody understands in a general way and then explores what happens when you take those ideas to their limits. For example, we all know pretty much what gravity is. But what if Earth’s gravity were twice as strong as it is? What if it were three times as strong, or a hundred? Looking at the question in that way makes you start to think about gravity a little differently.
Here’s another example. It turns out that, if you have a glass that’s literally half empty—the top half water and the bottom half a perfect vacuum—the glass shatters and the pieces fly up to the ceiling. But Munroe doesn’t just say, “the glass shatters.” He goes through every step of the process, so that you understand why the glass shatters. The suction squeezing together the glass and the water—which, by the way, is boiling—is so powerful that it actually lifts the glass off the table. When the glass and the water finally meet, the water is moving downward quickly enough that the shock breaks the bottom of the glass. Meanwhile, the glass is moving upward quickly enough that the broken pieces fly up to the ceiling. Munroe concludes: “If the optimist says the glass is half full, and the pessimist says the glass is half empty, the physicist ducks.”
So if you’re dying to know how fast you can drive over a speed bump and still live, or how many Legos it would take to build a bridge from London to New York, or whether we could make the moon change colors by pointing every single laser pointer on Earth at it—you’re in luck. Not only do you have a place to go for the answers, but you’ll also learn about a lot of other things like ballistics, DNA, the oceans, the atmosphere, and lightning. And when to duck if the glass is half full.