It’s a pretty safe bet that nobody is going to fill the solar system with soup, out to the orbit of Jupiter. For one thing, that would take a lot of soup—2 x 10 to the 39th power liters, which is also 10 to the 42nd power calories worth, or more energy than the sun has put out in its entire lifetime. So a soupy solar system is not likely to happen anytime soon.
That fact, however, did not stop a five year old girl named Amelia from asking about the possibility on the website xkcd.com, hosted and written by Randall Munroe, 37, the author of 2014’s bestseller What If? and the just-released sequel What If? 2. Since Amelia asked, Munroe answered, devoting the opening chapter of the new book to the matter of what he calls Soupiter. The answer, briefly, is not pretty—involving a soup-based black hole that would swallow up our entire solar system, annihilate everything caught within it, and cut a swath through a not-insignificant part of the Milky Way.
“I loved the specificity of the question,” Munroe says. “I mean, why soup? The questions I get from little kids are always the best, because they’re not being put together by adults, who understand lots of stuff. They’re just sort of pushing concepts together in surprising ways.”
There’s a little bit of Amelia in all of us—and Munroe has made it his mission to keep our curiosity satisfied. What If? 2, like the original, is stuffed with questions that are fanciful in the asking, but perfectly—and playfully—informative in the answering. If a T. Rex were released in New York City, how many humans would it need to eat per day to stay alive? (About half a human daily, or 55,000 calories worth.) Could you eat a cloud? (Maybe, but first you’d have to squeeze out all of the air, and the cloud would have to start out no bigger than a house, since one that size would contain about a liter of water, which is all the human stomach can hold at one time.) How long would it take you to fill an Olympic size swimming pool with your own saliva? (About 8,345 years, given that the average human produces about 500 milliliters of saliva a day.)
The questions throughout What If? 2 are equal parts brilliant, gross, and wonderfully absurd and the answers are thorough, deeply researched, and great fun—not least because they are accompanied by Munroe’s stick-figure artwork. Both books flow naturally—if somewhat circuitously—from Munroe’s earlier life.
A graduate of Christopher Newport University in Newport News, Va., Munroe studied physics, math and computer engineering and in his junior and senior years managed to nab himself an internship at NASA’s Langley Research Center in Hampton, Va. His work for NASA involved developing 3D visualizations and robot navigation systems for a prototype Mars airplane the Langley engineers were trying to develop.
“My job was to make the robot drive around the lab,” Munroe says, “so I was less worried about navigating over rocks on Mars and more about dodging chairs and trying not to hit the children of any of the Langley executives.”
The work was stimulating enough—indeed, more stimulating than the time Munroe spent in class back at Christopher Newport, much of which he passed by doodling in the margins of his notebooks. “I wasn’t great at taking notes,” he says. “I would draw stuff as I was listening—inventions I wanted to build or little stick figures running around and having little battles.”
Those scribbles eventually turned into something of a body of work, and ultimately Munroe decided he wanted to share them with the world via his own website. It was the frontier days of the Internet, when domain names were being scooped up by the bushelful and even the most imaginative names he could come up with turned out to have been claimed already. Finally, he decided that he’d have to get by on a string of nonsense letters.
“I didn’t want anything with an O in it because that can be mistaken for a zero,” he says. “And I didn’t want anything with an L because when that’s lowercase it can be mistaken for a one.” That brought him to the perfectly meaningless xkcd.com—a domain he claimed and quickly began filling with scanned-in versions of notebooks full of doodles, which he shared with friends, who then began sharing them with their own friends—and the following for the site began to grow.
Much of the subject matter of the drawings involved math and science, and before long, people began writing in with questions. “They’d ask me things like, ‘Me and my friend have been arguing about whether Superman could dodge a bullet without creating a shock wave,’” Munroe says. “Then they’d add, ‘This doesn’t seem like a question to bother a real scientist about and we both agreed you seemed like a good person to ask.’ Maybe I should have been insulted, but the truth was, they were right and so I would spend like the next six hours researching these questions.” (The answer, by the way, is that a bullet-dodging Superman could indeed create a shock wave—which would be decidedly disruptive to the nearby residents of his home city of Metropolis.)
Munroe found he quite enjoyed the hours he spent answering such fanciful inquiries, so he posted a note on the site soliciting more questions and from those, the original What If? was born. The book became a sensation, translated into 35 languages, and reaching number one on the New York Times bestseller list.
What If? 2 continues in the same spirit, even including another question about a bullet—specifically whether it would be possible to catch one fired straight up if you could somehow be positioned at the exact point at which it reached the peak of its arc and had lost its velocity. (The answer: yes, but it would be hot to the touch so maybe wear a catcher’s mitt.)
Getting playful with science doesn’t mean that Munroe isn’t also serious about science, and he does sometimes despair of our living in an age of scientific illiteracy or at least misinformation—with all manner of spurious beliefs at large concerning vaccines, climate change, the age of the Earth, and more. Some of this he ascribes to mere confusion about what’s true and what’s not, and he hopes his work offers something of a judgment-free zone for people who feel at sea about science.
“No one wants to look like the one person in class who isn’t following what’s going on,” he says. “People tend to think, ‘Oh, I must not be smart enough for this.’ So I think it’s really important to get across the idea that everyone is confused about scientific ideas. The most accomplished scientists and nonscientists—we’re all just trying to figure stuff out, and it’s OK to be confused.”
When Munroe finds himself in a position to debunk misconceptions, he leans on the facts—serving them up as neutrally as possible. “For someone who thinks the Earth is 6,000 years old, I would say, ‘Hey, have you seen this cool paper? It’s about this really neat dig site and it shows how the land shifted and it used to be underground and now it’s above ground.’ That might not lead to a conversion moment, but I find it’s better to engage with people rather than talking down to them.”
But reckoning with such politicized, third-rail topics is not what takes up most of Munroe’s mind-space. That remains devoted to the brand of fancy that fills What If? 2. If the universe stopped expanding by now, for example, how long would it take you to drive to its edge—assuming you observed a 65 mph speed limit? (4.8 x 10 to the 17th power years, or 35 million times the 13.8 billion years age of the universe so far.) If you were flying blind through the Milky Way, what would be your odds of hitting a star? (Just one in 10 billion—galaxies are mostly empty space.) How many constantly running toasters would it take to heat an average-sized home? (Surprisingly few—only about 20. If you decided to make toast in the process, you’d be going through roughly 30 loaves per hour.)
Do you need any of this information? No. Are you happy—indeed, delighted—to have it? Almost certainly yes. Science isn’t easy, but in Munroe’s capable hands, it surely can be fun.
Write to Jeffrey Kluger at jeffrey.kluger@time.com.