‘The Martian’ Is Full of Math Word Problems, Says Author Andy Weir

By Liana Loewus — October 02, 2015 6 min read
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Today marks the much-anticipated nationwide release of “The Martian,” a science-fiction film directed by Ridley Scott about a NASA astronaut who has to survive on Mars after being accidentally left behind by his crew. Matt Damon plays Mark Watney, the ever-quipping hero forced to “science the sh--t out of,” well, everything he’s left with on the Red Planet.

The movie is based on Andy Weir’s debut novel by the same name, which has been a New York Times best-seller for nearly a year straight and currently tops the list. Weir, it’s clear, did not see any of this coming. A computer programmer who studies orbital dynamics for fun, he originally posted the book as a series on his blog for free. He eventually put it on Amazon for the minimum 99 cents, and sales took off. The print publishing and movie deals came within four days of each other.

What’s special about this book—nay, what makes it a seemingly incomprehensible feat—is its attention to scientific accuracy. The Mars mission and Watney’s survival tactics—he creates water by burning hydrazine and he turns about a dozen Thanksgiving potatoes into a crop of potato plants using Martian soil and his own waste, to name two—are scientifically vetted and largely possible.

NASA officials count themselves among Weir’s many fans—and since all the hype, Weir has become somewhat of an unofficial spokesman for the agency. Scientist Neil deGrasse Tyson has called the plot a “celebration” of scientific literacy. We caught up with Weir today to talk about problem-solving on Mars and how the book might be used in classrooms.

How do you know so much about space? And botany and mechanical engineering and chemistry?

I just know how to use Google actually. ... I’ve spent my whole life as a space dork. I started with more than a layman’s knowledge but am not an expert. It’s just tons of research but it’s easy to do tons of research on something that’s interesting to you.

Do you think your book has utility in classrooms?

Definitely. It’s basically a collection of word problems. I think it could be used well for education. I’ve been contacted by a lot of teachers who are doing that. I didn’t consider that while writing the book—the whole book is riddled with profanity. When I wrote it, I was writing for what I thought was a niche audience of hard-core space dorks who are all adults and already scientists. That’s why I went into such detail in the science and used swear words.

Random House did consider a school edition [with words like] “crap” and “screwed.” They decided not to do that because it causes a real logistical nightmare to have two different versions of the book out. But I’ve always wanted to do it. I am going to push for it. I suspect they’ll be more amenable to the idea once sales fall off.

So what exactly have you heard from teachers?

They love it. Every teacher everywhere in the universe throughout all time is trying to get kids into STEM. This is a good way to present science in an interesting way kids will like.

[The book] presents word problems, effectively. Teachers can say, “Read to this point and stop. Your homework is to solve this problem he has.” It turns out to be a good study aid there. There’s lots of math that isn’t that complicated—some is, but some can be good for algebra-level math and science. What a lot of teachers have done is made a curriculum around it. It’s not like they’re using The Martian as their textbook or something but it’s a study aid.

Some teachers have gone so far as to basically download illegal copies of the book and print it up as worksheets and stuff for their kids. I’m not allowed to suggest that to anybody, but I’m not that upset about what people do to help kids learn science.

What’s an example of a word problem math teachers can use?

A good simple algebra problem in the book is Mark has enough food to last this long and can grow potatoes at this rate. Every potato has this many calories. How long now until he runs out of food? It works out to be like a bucket with a hole in it [problem, in which the bucket is leaking and being refilled]. It’s exactly that same format just with calories and time. That’s a good one for 9th grade algebra.

Are you a writer who loves science or a scientist who likes to write?

I guess I’m a scientist who likes to write. I spent 25 years as a computer programmer and writing was my hobby. It’s weird because they’re unrelated interests of mine.

For me, the Martian science drove the plot. I’d discover cool new plot points by sitting down and doing the math. He’s going to grow potatoes in the Hab [i.e., habitat]. I’m like, alright, let’s do the math on everything. How much land does he need to grow potatoes? And I realized, wait, I have a problem with water. Martian soil doesn’t have any water in it—at least at the time I wrote the book. I went online and found the moisture requirements for dirt if you’re going to grow potatoes in it. He’s gonna need many hundreds of liters of water, ... and that’s a problem he needs to solve. That took me on a whole plotline. I wouldn’t have come up with any of that if I hadn’t run the numbers on how to grow potatoes.

Sometimes I’d get into trouble, and he couldn’t possibly survive. That’s when instead of taking a math approach I’d take a literary approach. I’d say, “What’s the minimum gift from the gods he’d need to survive this?” There’d be some piece of technology he needs to have, and I’d figure out how do I justify that being on a Mars mission. So then I’d go back and mention it here and there [in previous chapters] so that from the reader’s point of view it was always there.

[An example of something he added retroactively, for those who have read the book or seen the movie, is the RTG—the heat source Watney digs up and uses to keep himself from freezing in the rover.]

Were you surprised a book with so many technical scientific details had such strong mass appeal? What do you make of that?

It was really a surprise to me it had mass appeal. I think people really like Mark and kind of want to see his adventures. Folks who are not as into science or math have said they would glaze over during the deep technical details; they’d skim it, which is actually really cool to me. It means that at some point during the novel I establish a bond of trust with the reader where they just say, “I’m sure all these numbers check out.” Establishing that level of trust with the reader is great and it’s not an automatic thing.

What advice do you have for teachers looking to motivate STEM students and inspire little Andy Weirs (and Mark Watneys)?

[I’d say] something they’d already know, which is that if you make the subject matter interesting, it’s easier for the students to learn. Rather than presenting math and science problems as dry numerical problem solving, present students with a tangible, real-world problem to solve and just hear what they have to say.

Instead of [the classic two-trains-leave-the-station word problem], say, OK, you’re going to rob this train that’s going from Chicago to L.A., and you need to be somewhere isolated. ... If you give them more information than they need to solve the problem then they have to pick and choose what matters.

So, one last question: Are you feeling the need for a rewrite now that

NASA has discover

ed evidence of flowing water on Mars


Well, ignoring the discovery from this week, even a few years ago Curiosity [a robotic rover built to explore the Red Planet] did photo tests and found there’s an enormous amount of water in the form of ice. So Mark could have baked the water out of it. My workaround on that is ... Mars has regional climates and Mark is in a desert. The soil where Mark is does not have that moisture. So no one can prove me wrong.

As for the briny water flows confirmed this week, those are not universal. They’re found in specific places. They occur on steep slopes. There isn’t much of that in Acidalia Planitia [where Mark was].

Image (top): Twentieth Century Fox Film Corp.

Image (middle): Andy Weir

Image (bottom): This NASA photo, taken by an instrument aboard the agency’s Mars Reconnaissance Orbiter, shows dark, narrow, 100 meter-long streaks on the surface of Mars that scientists believe were caused by flowing streams of salty water. —NASA/JPL/University of Arizona via AP

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A version of this news article first appeared in the Curriculum Matters blog.