For the past two years, xkcd creator Randall Munroe has been answering fantastical science questions for his popular webcomic’s sister site, What If?. In the new issue of TIME, Munroe talks about turning the project into a book (What If?: Serious Scientific Answers to Absurd Hypothetical Questions, hitting shelves Sept. 2) and how he conducts his investigations into topics like jetpacks and dinosaur nutrition.

“I try to be entertaining in the way I share them, but my real motivation with each question is that I want to know the answer,” Munroe says. “Once a question gets into my head, it will keep bugging me until I figure out the answer, whether I’m writing an article about it or not.”

Though Munroe says he uses stick-figures for xkcd and What If? because he’s “not very good at drawing,” we asked him to draw a self-portrait anyway — at least, as much of a self-portrait as you can get using only stick-figures. In the exclusive illustration above, also on newsstands now, Munroe has fun with the formulas for angular momentum of a spinning object (top) and centripetal force (bottom).

Write to Nolan Feeney at nolan.feeney@time.com.