Which is scarier: The zombie apocalypse or math? (Book review of The Calculus Diaries)

by Stephanie Chasteen on January 6, 2011

Mark Marek photography: Zombie walk in Edmonton

To continue the theme of the last post, today I’ll write about zombies.  I was happy to get a review copy of Jennifer Ouellette’s new book, The Calculus Diaries: How Math Can Help You Lose Weight, Win in Vegas, and Survive a Zombie Apocalypse.  Jennifer is a wonderful writer (and the reason I started blogging; she writes over at Cocktail Party Physics).   Though, admittedly, it’s a bit tough for me to give a totally accurate review — this book is geared to folks who don’t know calculus and want to know (a) how it works and (b) why they should care.  I already care, and forgot what it’s like not to know calculus, so I’m definitely not the intended test audience.  Perhaps when my significant other reads it, we’ll get a better sense of whether it hits its mark;  geeky curious but non-PhD folks are who she’s aiming for, I think.

The Diaries has a bit of the feel of a Mary Roach book, which is pretty high praise (Mary Roach wrote Spook: Science Tackles the Afterlife
and my alltime favorite book, Stiff: The Curious Lives of Human Cadavers).  Jennifer fills the book with interesting anecdotes, curious characters, and a lot of real substance.  My very favorite part is where she delivers on her promise to help us survive the zombie apocalypse.  The spread of disease is a pretty hot topic nowadays; how long after a disease — like swine flu — gets a hold on the population do we have to develop a vaccine?  Some diseases — like the common cold — affect a small amount of the population and die out.  Some — like the black plague — are more virulent and spread like wildfire.  A zombie invasion can be modeled with the same sort of epidemiological models used with more commonplace diseases.

People are infected by “zombification” if they are bitten by a zombie, or if they die and are ressurrected as a zombie.  Zombies die when you cut off their heads. But potential zombies (i.e., humans) are also born and die, adding and removing people from the potential zombie pool.  So, imagine that we create 10 new zombies every hour (through resurrection and bitten humans), but only kill 3 zombies every hour, she writes.  That’s a total of 7 new zombies every hour — the zombie equivalent of the black plague.  We’ll soon be overrun.  To really do this model right, you get some complicated interconnected differential equations (or, equations for how things change over time), since the number of new zombies that can be created depends on how many people are left alive, and on how many dead can be resurrected,  which depends on the number of zombies, and so on.  These “coupled” equations led the scientists (led by a guy named Smith) who came up with the models to conclude that it will take the zombies about 4 days to wipe out the humans.  Ouellette writes:

Quarantining the few healthy humans could help — the standard “hole up in a basement somewhere and hope the zombie hordes don’t find you” approach employed in classic zombie horror filmes.  We’ve se how (in)effective that strategy can be onscreen, and Smith’s number back up those observations.  However, another study by an Italian scientist named Davide Cassi implies that hiding out at hte mall (a la Dawn of the Dead) could vastly improve one’s chances of survival.  … The larger and more complex the structure — such as a large mall with many twists and turns — the lower the chances that the predator will stumble upon the prey.

Or, we could put the zombies in a holding pen — the equivalent of quarantining all the people infected with the Black Plague.  But this has to be done quickly, before the “infection” spreads too widely.  Smith concluded that the zombies have to be wiped out in a series of concentrated attacks, so that the outbreak dies out.  Sadly, this is actually similar to what happens in certain diseases that kill their victims so rapidly that they don’t have time to come in contact with many others (thus spreading the disease).  Or, on a positive note, Smith argues that we ought to combat HIB more aggressively — spending large sums over a short period of time — to follow the same sort of “impulsive eradication” scheme.  A more gradual approach, he says, is doomed to fail; HIV spreads too rapidly for a gentle approach to make a dent in the disease.

And if you want to know the answer to the burning question — can vampires survive a zombie apocalypse — take a look at Southern Fried Science.   I’ll give you the punchline — zombies always win.  But there is one ray of hope:  If the humans and the vampires join forces against the zombies, we might just survive.

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