NEW YORK • When Randall Munroe is working, it can look a lot like procrastination.
A typical work day for the former Nasa roboticist-turned-Web cartoonist often involves drawing funny stick figures, diving into Internet sinkholes while researching obscure topics or mulling over absurd hypotheticals, such as what would happen if a pitcher threw a baseball at 90 per cent the speed of light (answer: a huge fireball would engulf the stadium), or how many model-rocket engines would it take to launch a real rocket into space (65,000, give or take).
But when Munroe, 31, is actually procrastinating, it can turn into work. That was what happened three years ago, when he was playing a space video game.
He started giving his rockets silly names, such as Up Goer and Skyboat, then wondered if he could explain how a rocket ship works using only the simplest terms.
So he drafted a detailed rendering of the Saturn V rocket that launched astronauts to the moon, working off a blueprint from Nasa's archives.
In his annotations, he limited himself to a rudimentary vocabulary, labelling the boosters as the spot where "lots of fire comes out" and the oxygen chambers as a place with "cold air for burning and breathing".
That diagram became the basis for his new book, Thing Explainer: Complicated Stuff In Simple Words.
The illustrated book consists of annotated blueprints with deceptively spare language, explaining the mechanics behind concepts such as data centres, smartphones, tectonic plates, nuclear reactors and the electromagnetic spectrum.
In his explanations, he avoided technical jargon and limited himself to the 1,000 most commonly used words in the English language.
This barred him from using words such as helium and uranium, a challenge when describing how a rocket ship or reactor works.
"The word limit is fun because it forces you to think about it some more," he said, with the calm swagger of someone offering to fight with one hand tied behind his back.
Thing Explainer, out last week with a hefty first printing of 300,000 copies, is already generating excitement among Munroe's core audience of technophiles and alpha geeks.
"It is a brilliant concept," Microsoft co-founder Bill Gates recently wrote in a glowing endorsement of the book on his blog, gatesnotes.com. "If you can't explain something simply, you don't really understand it."
Over the past decade, Munroe has won a cult following for his quirky Web comics about science, maths, technology and relationships.
Prominent fans of his offbeat brand of nerd humour include fantasy writer Neil Gaiman; actor Wil Wheaton, from the science- heavy sitcom The Big Bang Theory; and Andy Weir, author of the best-selling novel The Martian.
"I'm a nerd, I like science and I like science humour," Weir, a former computer programmer, said when explaining the appeal of Munroe's books."
Lately, however, Munroe's following has expanded far beyond his early audience of computer programmers and physics graduate students to include mainstream readers who are curious about how stuff works.
His 2014 book, What If?: Serious Scientific Answers To Absurd Hypothetical Questions, became an unexpected hit.
It sold about 625,000 copies and turned him into a sort of science and tech guru to the masses.
"After decades of being just the domain of nerds, science is edging its way more and more into daily life," Weir said. "Science is starting to become cool."
Growing up outside Richmond, Virginia, Munroe devoured popular science books such as The Way Things Work and entered youth robotics competitions.
He majored in physics at Christopher Newport University in Newport News, Virginia, and minored in mathematics and computer science.
In college, he got an internship at Nasa's Langley Research Center working on virtual reality systems, and then took a job in Nasa's robotics navigation lab.
"My job was to keep the robot from running into walls, and it kept running into walls," Munroe said.
"I guess robotics is hard."
He had doodled for fun since first grade. In 2005, while still in college, he started posting his droll stick- figure comics on his website, xkcd.com.
First, they circulated among his friends. Then, other bloggers took notice and traffic boomed. When his Nasa contract expired in 2006, he decided to pursue his cartooning hobby full time and started selling xkcd T-shirts, posters and mugs.
He published a collection of his comics in 2010 and sold more than 100,000 copies.
With his books and comics, he has built a career as a lifelong amateur who flits from one esoteric topic to the next, something he feels he never could have done had he pursued a career in physics.
He still vividly remembers when a college professor told him he needed to develop a sub-speciality in physics if he wanted to advance in the field. He found that prospect deeply unappealing.
"'You can't have all the candy store,' is what he said. 'You have to pick,'" Munroe said. "I was really lucky to hit on the career where I can have all the candy in the candy store."
NEW YORK TIMES
•Thing Explainer is available at Books Kinokuniya at $29.95 .