What If? 2 is here with even more serious answers to your weird questions

Forget debating the airspeed velocity of an unladen African versus a European swallow. How many pigeons would it take to lift a person seated in a launch chair to the top of the Q1 skyscraper in Australia? Answer: You could probably manage this with a few tens of thousands of pigeons, as long as they don't get spooked by a passing falcon or distracted by someone with a bag of seeds. That's just one of many fascinating (and amusing) tidbits to be gleaned from What If? 2, the latest book from cartoonist and author Randall Munroe and the sequel to 2014's bestselling What If? Regular Ars readers likely need no introduction to Munroe, or his hugely successful and influential webcomic xkcd. But we'll give you a brief rundown anyway. Munroe has a degree in physics and worked for NASA's Langley Research Center as a contract programmer and roboticist. As a student, he often drew charts and maps and "stick figure battles" in notebook margins and decided to scan them and post them to his personal website in 2005. The webcomic got its own website in 2006, when Munroe left NASA to write xkcd full time. It didn't take long for xkcd, with its distinctive stick figures, to become a daily staple for scientists, engineers, and online nerds in general. There's nothing quite like them. Longtime fans know all about the tooltip with the hidden secondary punchline for each cartoon and Munroe's obsession with possible velociraptor attacks. They spent hours with 2012's "Click and Drag" and eagerly followed the four-month-long journey of time-lapsed frames that comprised the experimental "Time," which won the 2014 Hugo Award for Best Graphic Story. Munroe's 2012 tribute to the Saturn V rocket inspired scientists to take the "Up-Goer Five Challenge": explaining their research papers in the most basic language possible. In fact, Munroe ended up writing an entire book, 2015's Thing Explainer, using only the 1,000 most commonly used words in the English language. (For instance, pencils were "writing sticks," airplane engines were "sky boat pushers," and microwave ovens were "food-heating radio boxes.") What If? 2 follows the same format as its 2014 predecessor. Munroe selects absurd-sounding reader-submitted questions and attempts to answer them, illustrated with his trademark drawings. Some have relatively short answers, like whether it's possible to build a sword of solid air. (Answer: Technically, yes, but "it wouldn't be very strong, it would be hard to sharpen, and it would quickly give your hand frost damage.") Others get the multi-page treatment, such as whether you could fill an entire church with bananas.

These are interspersed with "Weird and Worrying" questions, where Munroe doesn't even answer them; he included them because he thought the question itself was funnier than any answer he could come up with. Case in point: if Harry Potter forgot the location of the invisible entrance to Platform 9-3/4, how long would he have to crash into walls before discovering it? "You could calculate out the answer by counting all the brick walls in the train station," Munroe told Ars. "But really, I just like the mental image of Harry Potter being, like, 'All right, it wasn't the last five, I'm going to try this one now.'" In short, the book is chock full of even more serious answers to seemingly silly questions. "Even if the answers aren't useful, knowing them is fun," Munroe writes in his introduction. What If? 2, for example (the physical book), "weighs as much as the electrons in two dolphins. That information probably isn't useful for anything, but I hope you enjoy it anyway." Ars sat down with Munroe to learn more. Bonus: today's xkcd is a fun flow chart guide for those who acquire a copy of What If? 2. Ars Technica: Somehow people got into the habit of asking you these really weird, silly, sometimes impossible, implausible questions. And you started answering them. How exactly did that happen? Randall Munroe: When I started drawing comics, I was surprised to learn there were so many people who were entertained by the same niche science ideas or funny applications of math to different problems—stuff I laughed at but I didn't expect anyone else to. Then I put up these comics and found there are a whole bunch of people out there who think about stuff the way I do. That was really cool. But I definitely didn't expect that people would start thinking of me as the person to settle arguments. I'd get these emails: "Hey, me and my friend have been arguing about this for a while now, and we don't know how to answer the question. It feels like it's not a good enough question to bother a real scientist with. But we both agreed you seemed like a great person to send it to." Perhaps I should have felt a little bit miffed. Are you implying that I have nothing better to do with my time, that a real scientist has important things to do? But they were also right. I would get these questions, and then six hours later, I’d wake up from a kind of trance, because I'd gone down every research rabbit hole you can imagine. For me, seeing a really interesting question, where you don't know the answer but you think it might be solvable—it can be like getting a song stuck in your head. You just can't quite drop it until you figure it out. So people would have these arguments, and then I'd get sucked in. I'd be like, I think the answer is this, but I can't prove it. I'm going to try to prove it. So it started off as me just trying to prove that I was right about something to a random person on the Internet. But then I found that I learned so much cool stuff while I was doing it that I thought, man, I should save these answers somewhere and share them with people. And that's how my What If? blog and book got started.

Ars Technica: Nerd gassing is a time-honored tradition. What are the kinds of questions most likely to pique your interest? What are the elements that make a good question? Randall Munroe: I think the questions that don't interest me as much are ones that don't really have an answer. I guess that feels trite, but there's a whole category of questions where the answer is, well, it depends how you define that word. You get into how many angels can dance on the head of a pin territory, or whether a hot dog is a sandwich. There's some interesting stuff there. But a lot of it comes down to arguments about semantics or definitions or values or perspective. And there are trick questions, like what happens when an unstoppable force meets an immovable object, where there's not really an answer to that. What I really like are questions that have an answer but it's not obvious what it is, and the different possibilities are all interesting. So I need to go see which one it is. I also like showing people that we don't have to argue about these questions with our friends forever. Math and science give us tools that we can use to answer them. The same tools that we apply to frivolous questions about Superman or funneling all of Niagara Falls through a soda straw—those tools can be used to answer really tough and important questions about things like climate change. Ars Technica: That's perhaps my favorite thing about the books. You show the process. Fermi estimates, for example, come up repeatedly. This is how a scientist thinks. You've got a problem or a question that seems a bit speculative or silly. You show people how to go about answering it. Randall Munroe: When I got a degree in physics and spent a lot of time around people who knew a lot of technical stuff—you get really insecure about what you don't know and what you're not sure about. You want to gloss over the things that confuse you and focus on the things that you really know. I found that it's better to let go of that and focus on the stuff you don't understand. Let's acknowledge this is confusing. That often is what leads you to really interesting ideas and a better understanding. But it's hard to admit that you're confused. So part of my project with What If? is to say, here's how I look at this when I don't know what the answer is. Here's how to approach a problem when you're confused. You're not expected to know the answer to these ahead of time. This is about the fun of figuring them out. Now and then, you'll have philosophers of science talk about the steps in science. The first step is hypothesis generation in the classical model. But how do you do that? There's not a clear answer. The answer is you guess. You just throw random stuff out there, and there isn't a method for that. That's what you're doing when you really are at a loss. I think it's worth dwelling on that. This is a fun period in solving the problem—the period when you don't know what's going on. Ars Technica: I've heard it said that the most interesting science begins when a scientist notices an odd detail and thinks, "Huh, that's funny." We tend to dismiss these silly speculative questions as not being serious. You write that you can actually gain some interesting, and serious, insights by pursuing seemingly silly questions.  Randall Munroe: Think about how much time we spend in school solving problems. What you're doing all day long in math class is solving problems. "We're going to find the roots of this equation. We're going to solve for X." That's not even silly. It's completely meaningless. X doesn't mean anything at all. It's just an example that we're working with in order to learn how to use this tool. Picking a silly question—like what if you funnel all of Niagara Falls through a straw or what if you fill the Solar System with soup—at least anchors the equations to reality and shows why you should care about them. If you're a human with some curiosity, you're interested in what's going to happen if you did this thing, even if that thing will never happen and this scenario is not of any practical importance. It's just fun to think about. Physics in particular, I feel, is a real back and forth between simplifying and idealizing things to make them easier, and then trying to anchor the idealizations back to the real world. Probably all science is like that in a way. But with physics, it really feels like you're walking a fine line between engineering and math.

Ars Technica: Some of the questions in the book are great because they elucidate common misconceptions, such as whether we could solve global warming if everyone put their refrigerators outside and opened the doors. You started your answer with, "Look, refrigerators don't cool their surroundings. They heat them." That's something many people either forget or don't understand.  Randall Munroe:  I remember as a little kid noticing that the back of our refrigerator had big exposed coils, and they were really hot. I was a little confused about why we had the hot stuff right by the refrigerator. That seemed like a bad idea. That must make the refrigerator work harder. What I didn't understand at the time was that a refrigerator is moving heat from the inside out to the coils. Sometimes people without air conditioning think they can just open the refrigerator to cool down the room a little. Well, no, because all they're doing is moving the heat from the inside to the back, which is still in the room. And since refrigerators don't do this with perfect efficiency, they consume extra power in the process. So the amount of heat that comes out the back is larger than the amount that is being sucked into the interior. Ars Technica: Thermodynamics is a harsh mistress. Randall Munroe: Yeah. That means that if everyone put their refrigerators outside, it wouldn't cool the earth down. It would heat it up. It would not heat the earth by a measurable amount. So I tried considering the power to run the refrigerator. Let's assume that's being generated by a power plant similar to the mix of power that powers a normal, modern American town. Consuming that power burns some amount of fossil fuels, which puts carbon dioxide and stuff into the atmosphere, which changes the flow of the sun's heat and warms the planet. What if everyone in the world added one extra refrigerator running all the time, sitting out on their lawn? How much would that change the earth's temperature if you include the extra emissions from the power plants? That turns out to be a third of a degree over the next century—a really stark illustration of how human scale amounts of power consumption, when it's species-wide or planet-wide, can measurably affect the planet. A third of a degree hotter on average is a lot. The comparison I always use is the last Ice Age. It was 4° Celsius colder, roughly. At that point, where I live in Boston was under over a kilometer of ice. So if 4° is the difference between the current sunny summer Cape Cod weather and a kilometer of ice, that makes the future where we might be going up by 4° seem a lot darker. Ars Technica: One thing that surprised me was that the Air Force actually conducted research on airline catapults. Randall Munroe: I'm always happy whenever I discover a study where they've looked into some idea that sounds ridiculous. I always imagine the meeting where someone first brought it up. "Listen, I know this is going to sound ridiculous, but you know those little rubber band airplanes you have of balsa wood and you pull the rubber band back and let go? What if we build one of those for airliners?" But yeah, they've looked into this because of how much fuel airliners burn when they're taking off. If we could launch them with some device that we could power by electricity, then that electricity could come from a cleaner source than burning jet fuel, which is a major source of emissions. Unfortunately, it looks like it's a bad trade-off because of the effort to put in the catapult and the amount of space you need for a commercial flight. The gains are so minimal that those kinds of catapult launchers have really only found use when you're really limited on the amount of space you have and you need to accelerate up really fast. There's another crucial element: people need to be able to handle the acceleration involved. Pilots and crews are used to it on aircraft carriers and have signed up to experience massive accelerations. They're trained for that. Regular airline passengers would not be happy if they suddenly had a 2G acceleration slam them into the back of their seats so that the airline could save a little bit of fuel on takeoff.

Ars Technica: One of the submitted questions produced what you called the most potentially destructive scenarios you've encountered yet: what if we had a proton Earth and electron Moon? Randall Munroe: Atoms are often explained as being little solar systems. It's not really right, that was an early model of the atom, but it's vaguely right. That is how they're physically arranged. You got protons in the middle and electrons around the outside. So what if you did that with a planet? The protons in the electrons would attract each other. You might think, then, that a proton Earth in the middle would attract the electron Moon that could orbit around it. But that's not how it would work at all. The electrons and protons would be attracting each other a little bit, but much more powerful than that would be the force pushing the protons apart and pushing the electrons apart, because you have a whole bunch of positive charges next to each other. They want to repel each other. The only reason atoms work is because there are a couple of other fundamental forces in the Universe. There's the strong and the weak nuclear forces and then some quantum mechanical principles that allow electrons to slot in next to each other and avoid pushing on each other and share the same space. Protons get to stay together because of this strong nuclear force and because of the presence of neutrons. But if you put a whole bunch of protons together, they start wanting to break apart. Even a regular atomic nucleus, if you have more than about 90 protons in there, it's prone to break apart on its own, even with the nuclear force holding it together. That's how we get fission bombs, and unstable isotopes. So if you try to put an Earth-sized ball of protons together, the amount of energy trying to push that thing apart is not only stronger than the force pulling on the Moon to keep it in orbit. It's more energy than basically anything you could compare it to. You'd just have this enormous amount of energy poured into one small area of space. And the scale is so different. It's hard to talk about what happens to space under those conditions. I actually ended up reaching out to Dr. Cindy Keeler, a string theorist, to ask, "What does it mean to put this many atoms together in a way that you could never get naturally, this many protons in one place?" She said, "We don't know." You put that much energy in one place, and you are subjecting space to conditions that are far beyond what we've been able to do in our biggest accelerators, beyond what cosmic rays achieve. I love stumbling on those things. One of my favorite things in this book was finding very simple questions where the answer is, scientists don't know.

Ars Technica: What was the most surprising thing that you learned while writing the book?  Randall Munroe: It was the question about whether it would be dangerous to stand next to an object that's at absolute zero. If you stand next to something that's the hottest anything can get, that's very bad. You will be disintegrated immediately. Super hot things put off huge amounts of radiation, and so you become exciting physics that you have to go ask a string theorist about. But at the other end of the temperature spectrum, really, really, really cold objects don't emit huge amounts of cold radiation. They just sit there. So you actually could walk up to a cube of metal that's 0° Kelvin or as close to it as you can physically get, and you would just feel cold. You'd probably need to put on a jacket if you stood there too long. You don't want to touch it. And definitely don't lick. But you could stand near it, and you'd probably be okay. Except I learned that if you're near 0° Kelvin, a cold surface will be below the boiling point of oxygen. So the oxygen in the air and also the nitrogen can condense onto the surface. And liquid oxygen, as we know from watching rockets explode sometimes, is really volatile and reactive. Things can catch fire when they are exposed to pure liquid oxygen that wouldn't ordinarily catch fire. Engineers who work with cryogenic fluids run into this problem. The idea that something can be so cold that it lights stuff on fire had never occurred to me. That just blew my mind. If you have a really cold object, it creates a fire hazard. I got a physics degree. I've read all about this stuff. I thought I knew how temperature worked, but that still caught me by surprise. Cold objects can start fires. Ars Technica may earn compensation for sales from links on this post through affiliate programs.