Writers Do Math, When Necessary

Writers read, a lot, according to several authors whose opinion and craft I respect. Most notably, I remember Dean Koontz in his book on writing talking about the need to read constantly. I also just like to read, because it is entertaining, and fun, expands my vocabulary and world view, gives me things to talk about with friends, and quite honestly, it's easy to do. But it also takes time. And while "I don't have time" is the frequent excuse of people who waste vast amounts of time doing inconsequential things (I'm looking at you, television, FaceBook, Hulu, YouTube, and most of the Internet), it is still hard to muster the 8 - 30 hours that it can take to read a good book.

In order to consume more books, I started listening to books on tape years ago, and I now try to have a constant stream of books on CD from the local library in my car. They're free, they're extremely convenient, and given the limited selection the library can carry, they tend to be only the most popular titles, which are often things I wanted to read anyway. Even with my relatively short commute, I get through at LEAST 30 minutes of "reading" a day, and if you include all other driving, I probably clear about a CD a day on average. That means I can listen to a 15 CD novel in about 2 weeks. Yes, you can argue about the merits of listening to someone read the text versus reading the printed page yourself, but I find the narration usually doesn't get in the way, and the time savings is well worth it.

The latest book I'm listening to is Deception Point by Dan Brown. It's a techno-political thriller that he wrote in 2001, after Angels and Demons, and before The Da Vinci Code. I'm on disk 10 of 15 so far, and the story is okay, although it frequently feels a bit thin in places, like he's milking more pages than are really merited from many of the story elements. But the things that have bugged me the most are engineering related nits which could have been largely avoided with some basic math and physics.

The most glaring has to do with the weight of a rock. I'll attempt not to spoil any of the story here, but several times there are references made to a rock which is initially described as "10 feet in diameter" weighing "eight tons." The rock is described as approximately spherical, which would give it a radius = diameter / 2 = 5 feet. The volume of a sphere is 4/3 * pi * radius^3, which means the rock has an approximate volume of 1.333 * 3.14159 * 5 * 5 *5 = 523.5 cubic feet. Using Google, we can easily convert this to liters and we get 14824 liters. Now, if it were made of WATER, and not rock, that 14,824 liters would weight about 14,824 kilograms = 32681 pounds = about 16 tons. But it's not water, it's ROCK. The rock is described as granite like, which would have a specific gravity, or density relative to water, of about 2.6. This means that it would weight 16 * 2.6 = about 41.6 tons. But even if we say it is the least dense rock we can come up with, pumice stone, the air-filled "floating rock" ejected by volcanoes, it would STILL have a specific gravity of 0.64, and a mass of about 16 * 0.64 = 10 Tons. The "eight tons" sounded wrong when I first read it, and now, especially after doing the math, it grates on me every time it is repeated.

So the follow-up question, of course, is why did this happen? Is there some major plot point I haven't yet gotten to about the rock being only 25% of the weight it should be? Or was it just sloppiness by Dan Brown, and then by his editors? Given how lauded Brown is for his extensive research, it seems strange and jarring that such a relatively obvious factual error made it into the book... And if anyone reading this knows Mr. Brown, I'd love to hear his explanation!