“Classic pursuit problem,” said math professor Craig Williams to a group of students and fellow faculty at the math and psychology building in Thomas T. Read Professor of Mathematics Colin Adams’ new book, Zombies and Calculus. They were watching Dean Collins flee a zombie chasing him across the science quad as he headed for Sleason Hall.
“If the zombie had a brain left in its head, it would cut him off, aim for a point on the path that Collins has to take,” Williams said. “But notice the zombie’s tangent vector is pointed straight at the dean at all times, not in front of him.”
Applied mathematician Oscar Gunderson stepped in to elaborate for Angus, a student, and Marsha, the department’s administrative assistant. Together, Gunderson and Williams explained that as long as the pursued is at least as fast as the pursuer, they will never be caught. They used this to their advantage: While Williams crossed the quad to rescue a fellow professor trapped in his car, Angus rode a bicycle in a wide circle, drawing all the zombies into pursuit. Soon, the zombies all shambled in a smaller circle inside Angus’ own, constantly pointing directly at him.
The standard version of this situation, Adams told me, involves a pirate ship chasing a merchant ship, but Adams adapted it to be suitable as the starting point of his book. “This is just something that’s true, and I thought it would be fun to explain it with zombies,” he said.
The book begins with a zombie student lurching into Williams’ calculus class and biting another student, and then proceeds to show how calculus helped the class survive the outbreak. It’s both a classic zombie thriller, with daring escapes and skull-cracking violence, and a calculus book, with regular interruptions for Williams and his fellow professors to explain how the apocalypse can be described or responded to using calculus.
Some of the problems addressed are not new. “There are courses at some colleges like this,” Adams said. Sections on the disease control and the predator-prey population dynamics have been taught using zombies before. All the applied math is based on observable evidence, he noted.
“For the audience, I was thinking of a high school or college student who has seen some calculus,” Adams said. “You can’t learn calculus from the book.” The book is intended, however, for readers with a wide range of calculus experience. When calculations get into gritty details in the course of the narrative, Adams directs readers to the appendix, so that those who already know the math can skip what may seem to them like busywork, while less savvy readers can take the time to really nail down the math problem.
Combining math with narrative and humor is nothing new to Adams. “I play characters when I give talks,” he said. Adams writes a humor column for the math journal Math Intelligencer and he’s also published a collection of short math-related stories. “I love thinking about interesting ways to teach math,” he said. “I’ve always loved to write, before I even wanted to be a mathematician. I wanted to write humor and fiction.” The first story he ever had published was in the Williams Literary Review.
Having written short-form and nonfiction for years, Adams took the opportunity to write Zombies and Calculus, his first novel, when he went on leave two years ago. “I considered it a hobby at the time,” he said.
He chose zombies because he “gets a kick out of the situation,” and thought it would provide useful angles into math. He watches The Walking Dead and consumes other zombie media, but admits that when a story is nothing but zombie killing, it can get boring. “It’s when there are various story lines and relationships that it gets interesting.”
In his book, the characters, one of whom is a biologist, hypothesize that perhaps the disease of becoming a zombie is a version of rabies, which, on infection, causes one to become aggressive and crazed. While it’s been eradicated in America, 50,000 people per year fall ill with rabies in India, Adams pointed out. He had to learn or relearn a reasonable amount of biology to write the book.
The other reason zombie stories are as resilient as the zombies themselves is that, as Adams said, “it’s fun to think about how you would survive under those circumstances.”
Once he completed the novel, Adams had friends in the College’s mathematics department edit it before sending it to the Princeton University Press.
Adams believes it is likely he will keep the character Craig Williams in his repertoire. He will give a talk in character during Family Days, and he was joined by fellow math faculty and several students for a NOVA video, in which they played human and zombie characters.
Adams says that any resemblance to real people is purely coincidental. The story takes place at Roberts College, in the Berkshire town of Westbridge, Mass., and the zombified bursar and provost are found in Hopson, not Hopkins, Hall. Even so, we can take comfort that were zombies to descend upon Williamstown, Adams has already figured out the math: It’s probably possible to knock out a zombie with a paperweight in a stocking.