HOUSTON—I'd guess that the majority of Ars readers are familiar with xkcd, the stick-figure Web comic drawn by former NASA contractor and engineer (and now Hugo award winner) Randall Munroe. It's rare for Ars to stop by a workplace to interview a source where there aren't xkcd comic strips festooning the walls (the "sudo make me a sandwich" comic is particularly popular among sysadmins), and discussion threads on forums across the Internet will frequently include a "relevant xkcd" link to emphasize or summarize a particular point with a comic on the topic.

Munroe draws and releases xkcd under Creative Commons licensing, and makes the majority of his income these days from xkcd merchandise—like his new book, Thing Explainer, which Munroe is currently promoting. The book takes the conceit demonstrated in the "Up-Goer Five" comic—labeling a diagram of a complex machine using only first thousand most-common English words—and goes nuts with it, breaking out dozens of different drawings with a similar labeling style. Highlights include "the pieces everything is made of" (the periodic table), the bags of stuff inside you (the organs and systems inside a human body), and "the shared space house" (the International Space Station).

Ars caught up with Munroe before a book-related talk at Space Center Houston, and he was kind enough to give us a few minutes to talk about space, Up-Goers, and the iterative process of explaining things.

Many Kerbals died to bring us this book

Thing Explainer's genesis was the "Up-Goer Five" comic, which had Munroe take NASA's Saturn V rocket—the launch vehicle responsible for putting astronauts on the moon—and label its parts using those thousand most-common English words. Geeks tend to love supernals, and as the largest, most powerful rocket to successfully fly the Saturn V definitely qualifies for that description, but Munroe's initial attachment to the rocket came from an off-the-wall direction.

"I worked for NASA for a while," explained Munroe. He's a soft-spoken fellow, with an engineer's habit of rarely letting his eyes rest on a single spot for long—the better to quickly assess the world. "But what I worked on was pretty unconnected to rockets—I was working on robots," he continued, "and they were like robots that were technology demonstration platforms for different sensors they were testing." The personal connection with space came not from his time at NASA's Langley Research Center, but instead from Kerbal Space Program—which, if you're not familiar, is a video game wherein you build rockets to send little green men into space.

"I got really into that!" he laughed. "And sort of the more I played that, the more I appreciated just how weird and unbelievable the Saturn V is….the thing that's most extraordinary about is, that was the most practical solution anyone could come up with."

"It seems like you must be missing something if you're like, ‘All right, this is really hard so let's just build a skyscraper-sized fuel tank and then, like start a fire under it and it will fly up into space!' And getting to the moon is harder, and getting there and landing and taking off is even harder, well, let's just make it huge! Looking at the videos of it starting and the scale of all the parts—that was really the least out-there idea anyone could come up with?"

The KSP playing figured heavily into the actual idea behind the "Up-Goer Five" strip and Thing Explainer. "I started giving my spacecraft increasingly dumb names in Kerbal Space Program, and then eventually I got to ‘up-goer,' which I thought was the dumbest I could do, and I was like, ‘Hey, I wonder if I could label the rest of it in terms that are just as simple?" Munroe's Up-Goer series of rockets in KSP actually ended up flying pretty well, in contrast to his earlier more traditionally named efforts, which though they carried grand names like "Apollo" and "Chariot," would frequently explode and kill all his Kerbals.

Thing explainer explainer

Some of Munroe's best comics—and the ones he says are among his most favorite to draw—are the ones that illustrate or explain a concept, like showing how much money exists in the world or a logarithmic radiation dose chart. Those comics, explained Munroe, typically come from him wanting to see what a data set looks like or why a thing works the way it works. Rather than relying on inherent knowledge, the comics often require Munroe to educate himself on the topics at hand (although he does admit that he was able to do the comic showing the paths taken by all the characters in the Lord of the Rings trilogy mostly off the cuff, due to being really familiar with the series). The results are often extremely accessible and demonstrate concepts simply and clearly. Between xkcd and his companion site What If, Munroe is rapidly becoming the Internet's explainer-guy.

"I think there are a lot of issues where people are recognizing that we need an in-between role," he said, referring to STEM topics or other science-y issues that might not be immediately graspable to the lay person. "There was a really big paper I've been thinking a lot about on antibiotic resistance, and it was finding just how much people were misinterpreting the language around it, in a way that doctors had never realized—and it was a big wake-up call. Even the stuff that we think is clear public communication isn't always having the effect we want, and maybe relying on scientists to also be communicators is a bad strategy, because they're busy being scientists."

"But I don't think of myself as being really squarely in that area," he continued, referring to a full-time science-communication role. "I guess my current book really is, but mostly I'm a chronic explainer—when I was five years old, I was very shy, but show-and-tell was my favorite! I've been a chronic explainer from a very young age."

Munroe said that the comics dealing with complex science topics—and the books he writes—are more often than not written for himself, as sort of a summary from his future self back to his past self before he did the research and grokked the concepts. "Like, I'm writing for myself before I understood this thing…and at the end, I'm like, ‘Okay, I feel like understand this now, if I were writing myself Cliff's Notes on this, what would be the simplest way to get this across?'"

Munroe was excited to stretch his explainer muscles in Thing Explainer, but some topics proved too esoteric to fit into the "thousand most-common words" format. One thing that Munroe wanted to put into the book that he wasn't able to make work was an explainer on mechanical watches.

"There's a weird problem you run into, which I almost feel is the same problem you run into with quantum mechanics," he said. "It's that there are all these different parts" to a mechanical watch, "and you're like, ‘what does this part do?' And the answer is, like, ‘it is that shape, because that will fit into the ones around it…' There is no simpler explanation of what it does except the shape itself. Like, ‘it's that shape because it fits into the other one because it's that shape,' and the whole thing is a bazillion parts like that. Language doesn't map very well to the concepts in a watch—or, at least, I don't know how to do it!"

At other times, sticking the limited vocabulary caused headaches. Because of his background in physics, Munroe was particularly pained at being able to use "weight" but not "mass," since the latter was not on his word list. Additionally, the most appropriate word he had available to use when describing structures inside a human body was "bag," which he had to use to refer to organs and also lots of other things, including cell components. But having to use "bag" over and over again resulted in an insight Munroe said he might not have otherwise said: the human body can almost be described in terms of set theory, with interlocking containers containing containers, all arranged just right in such a way that their interlocking manages to sustain itself.

Space, above and beyond

When it comes to the current state of space, Munroe is taciturn. "That's a really political question," he responded when I asked. "Like a lot of nerdy, space-associated people, I like space—I like going there and the idea of building cool stuff to go there. The question of how to do that, and the policy stuff involved, is really a whole different set of questions—one which I don't have the expertise to talk about very coherently."

"I did have a friend, Allison Wilgus—she writes about space and does comics, and she said that the ideal space program is the one that we actually do—and I thought that was a good point. You can criticize the Space Launch System for being over budget…or the ISS for not having a clear mission or whatever, but it isn't like we get to just pick which one we do and then do it. It's a hugely political enterprise and getting anything done at all—getting any huge group of interests to cooperate to get anything done is amazing."

As we wrapped and the sound techs came over to wire Munroe up for his talk, he smiled and we said our quick goodbyes. In spite of the amount of detail in the "Up Goer Five" comic, Munroe had never actually seen a Saturn V in person, and the day's schedule was being tightly orchestrated so that before he left, he'd be able to stop by the Johnson Space Center's Rocket Park and take a gander at the 363-foot (111 meter) rocket on static display.

But he had one more thing to add about space. With a quick laugh, he looked around the auditorium, which was softly lit and decorated with NASA logos. "I would like to go to the moon," he said softly. "Because then we could have an extreme sports dome on the moon where people could fly on their own muscle power. In my ideal world, that's what I'd be doing."

Thing Explainer is on sale right now, in hardback or e-reader formats. Amazon has the hardback for $14.97, and the Kindle version is $12.99.

Listing image by Lee Hutchinson