Randall Munroe

Transcription

MALE SPEAKER: Let's give it up for Randall, all right. RANDALL MUNROE: Hi. All right, so I wrote a book. It's full of my answers to questions that people submitted through my website. And so one of the questions that was submitted that I would like to talk about today is the question that someone asked-- what if you built a periodic table using bricks, where each brick was made from the corresponding element? And so for-- there's a bunch of different elements, some of which are easier or harder to get a hold of. All in all, there are-- of the 118 elements in the periodic table, there is about 30 of them which you can get at the local supermarket. You can get samples of aluminum. You can get samples of-- oxygen and nitrogen are not hard to find, either. And then there are another bunch of elements that you can get if you're a little bit more creative. For example, if you need a radioactive source for a cloud chamber, which is a science project you can do, you can take apart a smoke detector, because they'll have a tiny lump of americium in the middle of it. And if you-- it's a very small amount-- but if you wanted to make a brick, you could just buy a whole bunch of smoke detectors and disassemble them all and gather all the americium together. And this is an effective way to A, get a brick-sized sample of a rare element that's otherwise hard to find, and B, get yourself onto a bunch of government watch lists really quickly. But despite-- there are some dangers to this, for example, a lot of these elements, in addition to being maybe hard to find and/or some degree of illegal, some of them are kind of dangerous to handle. So mercury, depending on what form it's in, can cause mercury poisoning, which is really bad. Even some of the elements up near the top of the table, like beryllium, is-- it's not radioactive or anything-- but you don't want to get it on your hands and into your food. So there is-- but despite this, people try to collect samples of as many elements as they can. And I totally understand this sort of collector's compulsion that people have, because I played the original Pokemon on Game Boy. And if you look up what year I was born and the release dates when "Pokemon Blue" and "Gold" came out, you'll realize that I was actually not quite in the-- I was a little older than the demographic that was supposed to be playing Pokemon. But I played through, and there's the appealing idea that there's-- originally-- 151, plus or minus, Pokemon. And the goal is to collect them all. And so there are 118 elements. So it's easy to think of them as sort of radioactive, and sometimes very short-lived, Pokemon. But people who try to collect them usually top out somewhere around 80 to 90, depending on how comfortable you are with your health and safety, how much money you have to put into this, and-- in the case of plutonium-- how many international laws you're willing to violate. And the elements at the very bottom of the table are the ones that they typically have a hard time with for reasons which will become clear in a moment. So we're going to start with the top of the table. So what I decided to do is think, OK, I'm going to build a periodic table. There's going to be trouble near the bottom. But let's start with the top. So the first row of the periodic table is just hydrogen and helium. And that would be easy to build, because you get a bunch of hydrogen, get a bunch of helium. I think we have a helium shortage, but you can still buy it at party stores. And so you if you made a brick of those, it would be really anti-climactic. It would just sort of diffuse and float away, but this would be a good place to stop. Because we have seven rows to build-- so of these rows, the first two rows really you can build without too much trouble. The third row will burn you with fire. The fourth row will choke you with toxic smoke. The fifth row will do all of the things that the first rows did, plus give you a mild dose of radiation. The sixth row will disintegrate instantly in a column of steam and extremely toxic dust and smoke and destroy whatever building you're doing this in. And you should not build the seventh row. But the first two rows are OK. You can build these without trouble. The second row you also-- if you built this, you'd have some elements that are solid and some that are gases, but they would basically float away. The one, though, that I want to point out here is fluorine. Fluorine is really, I think, the worst element. It's the most reactive element in the periodic table, and I was recently reading a list of chemists who have been mauled or killed doing fluorine experiments. So not only is it super-reactive, there's a fluorine compound which, if you have a gas of this compound, and you place things in it, almost any substance will spontaneously catch fire in a fluorine atmosphere, including, for one of these compounds, ice cubes. So you definitely don't want to breathe it in. It would just sort of spread out across the ground, but you can back away slowly. I do remember seeing in a data sheet that it will also eat through many common gas mask materials. So be careful with your safety equipment. But it really doesn't become a scary situation until we get to the third row. So the third row has a couple of troublemakers. Over on the left is phosphorus-- over on the left is sodium and magnesium, and those would probably also-- you can see the sodium actually-- I think drew it starting to tarnish a little bit. Depending on how moist the air is and what the conditions are like, those would more or less rapidly start to oxidize, either slowly or quickly. But over on the right, we have phosphorus. And because it's, I guess, more fun to draw, I assumed that we were using the white allotrope of phosphorus, which will spontaneously ignite when it comes into contact with air. And so we have this lump of burning phosphorus, and then the things around it, which might not normally spontaneously catch fire, will be lit on fire by the phosphorus. And as if the whole situation were not combustible enough, it's not just happening in oxygen, because we've got fluorine from the row before spreading out over it, and then also we have chlorine that's just below the fluorine, which is almost as bad. So at this point, you definitely don't want to breathe this in. You want to back away. It's going to be a lot more smoky than the previous one. But you could probably survive this. The fourth row gets trickier. So the fourth row introduces a bunch of new elements, including the metals-- a lot of the more traditional metals. And also we have a lump-- underneath the phosphorus is a lump of arsenic. And so arsenic is sort of a really recognizable element, and we have a lot of associations with it. And I remember hearing an interview with a spokesperson for a chemical plant in Texas, I think, where there had been groundwater contamination downstream from the plant. And the spokesman said, you know, yeah, they've detected arsenic in the water, but arsenic is really a scare word. And on one hand, that is probably not the best public relations, to say, oh, it's arsenic, but arsenic is not that bad. But on the other hand, he has a point, which is that there are trace amounts of arsenic in just about everything. So all of our food has a little bit of arsenic in it-- few parts per million or billion-- and that's OK. And there could be a little bit more than that, and it's also OK. It's not going to be toxic. But on the other hand, this is a lump of arsenic, one part per lump. And the reason that we-- even though there is a little bit of arsenic in everything-- the reason we have these associations for it is that in large enough quantities it is toxic to virtually all forms of life. And this is-- a lump about yea big is definitely a large enough quantity. So the phosphorus has the burning sulfur-- the burning phosphorus and then the sulfur sitting on top of it. Next to it is the selenium and the bromine, which are also reacting pretty vigorously, although probably at this point cloaked in the smoke that's bubbling off of the phosphorus here. And all of this is wrapped in this smoke that's boiling off, which is also smoke that's full of fluorine compounds, just to make things more exciting. And so you have all the burning chunks-- arsenic combining with the phosphorus and making all these compounds that are arsenic-something-something oxide, arsenic fluoride, and things that. If you don't get away pretty quickly, you will be breathing in a bunch of stuff that could definitely kill you. So the right thing to do here is to run away very quickly and not keep building rows, which is what we're going to do. This fifth row I think of as sort of the foreshadowing row, because the fifth row is the place where we meet our first mildly radioactive element. And this is one that I have heard-- so I memorized the periodic table. If you hadn't gathered from the Pokemon story, I was not always the best at being social and finding other people who shared my interests. So one thing was I learned the periodic table from books, but did not talk to a lot of people about it. And so this is an element where it's sort of like the aluminum-aluminium thing-- I've always pronounced it "tech-net-ium," but the few times I have heard someone else pronounce it, which I have-- although, come to think of it, I'm not sure why I had heard that-- but I've also heard technetium. And that led me-- I was wondering about that. But then I got distracted because I decided to look it up on Wikipedia, and then got diverted into reading the something like 10,000-word talk page argument over aluminum versus aluminium. And I got into, like, archive seven of that and then had totally forgotten what I was originally supposed to be doing. But this element, whichever one it is, is the first mildly radioactive one. Now in this scenario, it would not kill you before the arsenic, the phosphorus, the smoke, the fluorine, and then also, again, the left side of the table here, which is like slightly less bad, but still bad-- the potassium and sodium. Those would all kill you first. The "tech-net-ium" or technetium is not radioactive enough to kill you. At least, I think you would have to cradle it to your body for a day or so, or if you managed to eat a chunk of it, or wore it as a hat that could give you a lethal dose. Hopefully they can add that to the material safety data sheet-- do not wear as hat. But the radiation itself would really not be the biggest problem you would be facing here. For that, we're going to go to the sixth row, because the sixth throw contains astatine. It contains a lot of other things too. And I remember when I first saw this printed in the book I was reading, I was flipping through, and I hit this article, and I hit this illustration, and it was like, oh, hey, I stopped drawing all the smoke and stuff. I wonder why. Was that a mistake? I had the-- the mercury should be flowing just like the bromine was. How come I just drew them sort of stationary like that? And then I remembered that the only chance we will have to see this table is the snapshot taken right at this moment, because-- so plutonium is radioactive. And we use it-- we use uranium in reactors, where we trigger chain reactions in the uranium. And those chain reactions-- the uranium undergoes fission, and because I can never figure out the verb form that I would use there to say where it fizz-- fizzes-- fissions-- nothing sounds right, so I'm just avoiding saying that. It undergoes fission. It splits into chunks, and that releases energy which splits more of it and splits more of it. But it will also-- if you have plutonium sitting there, it's radioactively decaying, and so it emits heat. And that is what we used to power a bunch of the long-term space probes. So the Curiosity Rover has-- and I really find this amusing for some reason-- but they have a chunk of plutonium, which-- I think we've come very close to running out at this point and may be buying it from Russia. So if you're an element collector, I know that there's someone out there who's selling it. If you can avoid all of the federal agents who will try to find you if you Google-- I did Google plutonium prices for this and then started thinking, like, wait a minute, well, I'm probably on that watch list already. I think, actually someone asked me if any of my research got me in trouble, and as far as I know, all of that googling-- like there was a question I answered where I was writing about the most expensive thing you could put in a shoe box. And I've looked up prices of a bunch of hard drugs and then realized my search history is now how much does heroin cost? How much does LSD cost? OK, but, like, on the street, in the city, how much does it cost? Or what about this city-- trying to get a real practical street price. But really the only consequence I've ever suffered was there was an article I was writing a couple of months ago, and at one point I wanted to include a sample of the items in the collection of the Library of Congress and what kinds of things they were on the whole. And it was sort of hard to get broad statistics of the kind I wanted. So I figured, oh, hey, I'll just randomly sample their collection and look at 100 items and see how many of them are books and how many of them are other things. And so I found-- they had a web API and collection items had one number. And I was like, OK, the number looks-- it's not too many digits. It's probably not too sparse a space. I'll just start requesting random IDs. And then I parallelized that, because that was going too slowly. And then I found it was really hard to get good data. And so I was ramping up the number of requests I was making. And then suddenly they stopped returning anything, and then I found that not only had the API blocked me, but the entire Library of Congress website was now redirecting me to a 403. And in fact, everyone in my building was also redirected to the 403. And I felt like that's totally fair, because I was definitely spamming their API and abusing it, but I also felt really bad about that, because I have never been kicked out of a library before. And I felt like that was a line I had crossed. So I really wanted to apologize to them, that I just wanted to tell people about their cool collection, but sorry. So the thing that really entertains me about plutonium is that you think of these sort of complicated reactors, but with plutonium electric generators, we're just using the fact that this thing gets really hot. We just wrap it in things that will generate electricity from the heat and from the radiation that's being put off by this. But then we have the problem that it's a big chunk of plutonium, and it's hot, and it's radioactive. And so they put it out on a long stick and just hold it away from the Rover. And so you can see on the Voyager probe they've done the same thing. And so they've got this long scaffolding arm. And at the end there's a little thing that I always assumed is a scientific instrument. But no, it's just a chunk of plutonium. And the Curiosity rover has the same thing. And this plutonium has a half-life on the order of a century, which means that after a century or so-- or whatever the specific half-life is-- 80-something years-- the heat and power output will drop in half. And so they've designed it to keep working until the voltage drops to a certain point. And so it can keep running for decades, assuming the other stuff holds up. But if you wanted to run something for longer than that, you would need something with a longer half-life. I did work out, by the way-- the plutonium chunk that they're using on Curiosity, if you had a Nintendo Game Cube and a TV hooked up to it, it would provide enough power for about 130 years of continuous play. So if you are stuck on Mars, and you've managed to commandeer the Curiosity Rover, if you have brought nothing except a Game Cube and a TV-- But the half-life of plutonium is just about right, because if it were much longer, that also means that it is less radioactive, because it's taking longer for half of it to decay, which means it will be producing less power and less heat. And so you always try to find a balance. And this is also why nuclear contamination sites-- when a reactor melts down or something-- the really nasty elements are the ones that half-lives of about 30 years, because the ones that have half-lives of a day or two are incredibly radioactive, but then they all decay, and they're done. And so those will be the things that will give people lethal doses very, very quickly. And then the things that have really long half-lives-- like uranium 238 is on the order of billions of years-- that stuff does not decay often enough to emit much energy. So the really bad stuff is the stuff that is like a 30 year half-life, so it will contaminate the area for a couple of decades, but also be short enough that it's emitting a lot of radiation. And plutonium is, again, about a century. So it emits all of that heat in about a century. So astatine, in its most stable form, has a half-life of eight hours, which means that all of the energy emitted by the plutonium powering the Curiosity Rover over the course of the next century, if it keeps running, is being limited by our lump of astatine in an afternoon. This is why no one has ever collected enough of a sample of astatine to really look at it, because any sample large enough to see with a naked eye would also melt the naked eye and vaporize itself from its own heat. This actually leads to a really funny situation. My favorite thing about looking up these elements is, if you look under astatine, there are all these great chemistry data tables, like "CRC Handbook of Chemistry" that list all of the elements and every conceivable property you could want. And actually during the street drug research, I remember I was trying to figure out cocaine density, or something like that, and found that they actually have a whole bunch of data on a bunch of these, but for some of the drugs they have mysteriously missing chunks. I didn't know if those were removed for some reason-- if that's sensitive information, or if it's just no one else has really tried to figure out the physics of a shoe box of LSD. In the handbooks, if you look up astatine, you'll find all its density and stuff and its various properties. But if you look at-- surface appearance is a field that they'll have where they'll say is it shiny? Is it reddish? Is it matte? Does it have a luster? Is it black? And astatine will just have a question mark, because there is no way-- if you have a sample that is large enough to reflect light, the light that the astatine is emitting will be brighter than whatever it is you're trying to illuminate it with. And so no one has ever-- I think that I've read that the best guess is that it is probably black if you were able to illuminate it brightly enough to see. But it's also possible that it's shiny and kind of metallic-looking. And that will probably be a mystery forever, because those are chunks of astatine that are a collection of a bunch of molecules in one place. This would be a chunk of about a liter, which is more astatine than has ever been made or exists in the world. And this lump of astatine would promptly turn into a column superheated steam by that heat that it's pouring out. But this column of superheated steam will continue pouring out that heat steadily for the next eight hours, and then the next day for less than that, and less than. And this is-- so if someone were actually trying to do this table following these instructions, first of all, there's a legal disclaimer at the front of my book. They said, you can make this kind of a joke, but definitely do put this in about not doing this at home. And this is one where if somehow you were a bunch of people with both the resources to get a hold of some of these elements and an environment that was fostering really weird experiments in the building where you might be able to get away with doing something like that, the amount of astatine that you would be using here is a quantity that maximizes the amount of paperwork you're going to have to face, because if it were smaller-- a liter is enough that it will probably demolish the building that you're doing this in. And there are going to be a lot of people asking questions. For example, whoever owns the building, or whoever was paying you to do something else when instead you were doing this. Do you still have 20 percent time? Is that? Well, I guess you've already seen all the Google searches I've done for plutonium suppliers. You can find that out. But if you did this, there would be no way-- if it were a smaller amount of energy coming from the astatine, you might be able to cover it up. You could just-- if it was a well-built room and sealed away, and then you'd have charred walls, a lot of radioactivity, but you could in your 20 percent time discretely work to clean that up, and maybe the news of what happened would not reach your immediate superiors. If it were a substantially larger chunk of astatine, then there would be no one left to submit paperwork to. And that is what would happen with the seventh row. And so the seventh row-- we're getting down into the elements that just have numbers, and they have not settled on names yet. When I was a kid and learning the periodic table-- and playing Pokemon and being really totally well-adjusted and very, very popular and social, but also memorizing the periodic table-- I found there were a whole bunch of elements that got you up to 100-- you could get up to 105 or so, or 110. Some of the books I had went up to 110. But then they stopped, and all of those didn't have names. They would just be like "unun-something-ium" that was like this naming convention. And they've start assigning names recently. They've started finishing it up. But we're also at a really interesting situation, which is that they have synthesized elements, as of a couple of years ago, they finally synthesized element number 118 in a particle accelerator, which means that they've squared off the bottom of the periodic table, because they finished out a row, which is not something-- which has not been the case for a very, very, very long time. And when I saw that, because all the periodic tables I learned as a little kid had an extra line that ended halfway across. And I don't know if it's a typographic thing, but I feel like it's very, very satisfying have the nice, square, rounded-off shape. And it gives me this weird urge to sabotage particle physics experiments, so they don't synthesize element 119 and ruin the really nice justification. But the reason that the elements are only being filled in right now is that they're very hard to produce, and they are very short-lived. And so astatine, the reason it decays so violently and destroys the building you're in, is that its half-life is only eight hours. So it dumps all of that stored up radioactive energy in eight hours. Some of the elements at the bottom of the periodic table will decay-- they have half-lives-- some of them are measured in seconds and a couple of them in milliseconds. So all of the energy that's released by your column of heated astatine rising into the stratosphere over the course of an afternoon will be released by these elements now, right away. It would be sort of like a nuclear chain reaction, only it's not one part triggering-- it's not one of them decays, and that triggers the other ones to decay. It's not a chain in that sense. It's just a reaction. It all happens it once. However, there is sort of a chain element, because the elements that are up way far on the periodic table, some of them will emit a couple of protons and neutrons, which now makes-- element 118 has 118 protons-- it decays immediately, releases some protons, and becomes element-- maybe it drops down two spaces-- it becomes element 116, which is also extremely radioactive and has a very short half-life. And so you get these decay chains, all of them pouring out a whole bunch more and more and more energy all at once. And the energy released-- so if you were able to watch this whole scenario from very, very, very far away, on one of the mountains-- which way are the prevailing winds here? They come in from the ocean, so I guess from the west, out over the east, so maybe to the south in the mountains, southwest-- anyway you would first see this, because the energy released in the first few seconds would be on the order of that from a medium-sized nuclear weapon. But because of these decay chains, these things just continue and continue decaying and decaying. So it's like a nuclear bomb which just keeps exploding. And what happens is you've got your wall, which existed for-- if it's made out of one liter blocks, I guess it'll be a couple of metres wide. It will take light in the neighborhood of 10 nanoseconds to cross from one side of the wall to the other. So you have that much time to enjoy it before the radiation vaporizes it. But it vaporizes it, but you've still got this plasma of these radioactive nuclei, which are continuing to decay. So your mushroom cloud is now pouring out all these radioactive products and elements, and it's continuing to become super-hot the winds carry it away from you, cover everything downwind, and it's only-- I only realized very, very recently that when you have a mushroom cloud, and you have all the heavy dust and stuff with the uranium dust on it that is in the mushroom cloud, but it's heavier than air-- so as it cools, it falls down from the cloud on to the ground, which is actually why it is called fallout, because it falls out of the mushroom cloud. And I guess that's sort obvious in retrospect, but it had never occurred to me until just now. So this cloud is full of this stuff, which falls out of it and covers land. And this stuff is rapidly decaying. All of these elements way down the table are decaying until they reach something so stable as astatine, and then they take a break. And that is a much more calm situation, because then it's just superheated plasma and not quite as superheated exotic particle mess. So this whole mushroom cloud will continue spilling out this stuff as it goes downwind, rendering more and more areas uninhabitable for long periods of time. And from a nuclear cleanup point of view, it's sort of hard to figure out what to model this on, because of the way that the steam is superheated, and it's all mixed in this cloud. And you've got a lot of heat, and then a lot of cold environments, and a lot of high pressure environments, and then low pressure environments. And you have samples of literally every single element in this-- at least at first-- you have all of chemistry happening at once. Every different pair of atoms that can run into each other will be running into each other here somewhere in your cloud. And they were doing it under every different kind of condition. So every product that could happen from a reaction that you're like, oh, this is hard to clean up, will be happening in this cloud. So in addition to all of the radioactivity and all of everything, if you just flip through a chemistry book, and you can point like anything, you will have that problem to deal with too. And also at this point, it's definitely the least your problems, but all I can think is also there's a liter of fluorine in there too. And I'll just have my gas mask, and I'd be thinking about that too. So this, if nothing else, definitely helped me come to terms with my sort of Pokemon-inspired frustration that you can only buy 85 or 90 of the 118 elements, because this has really driven home that the most important thing an element collecting is that you do not catch them all. But I got this-- I had come up with the scenario. And I have physics background. And in doing what-- I've gotten a lot more into geology. I was learning about the way continents break apart as you do various horrible things to them-- that's been a lot of fun. And I've also learned a lot more biology lately, but I feel like chemistry has always been something that I've had a harder time with, maybe just because there are a lot of things that-- this atom is more electronegative than this atom. But we don't have a real life-- it's sort of harder to connect that to real life. And you know quantum mechanics can be hard in the same way. And I really like stuff where it's easy to think about intuitively, like mass and speed and force, because you can think about this is an object. This is an apple. This weighs this much. This is what a kilogram means. This is what a ton means. And so I feel like I had a harder time with chemistry. And so after I finished this article I got, because I was writing this for my book and had a little bit more luxury-- I could have a longer deadline-- I got in touch with a professional chemist, because I wanted to run it by him. And I said here are all these reactions that I've worked out that I think will happen, but I wanted you to look over it. And let me know what you think. And this guy was really helpful. I talked to Derek Lowe, who's a chemist who also writes the drug industry blog "In the Pipeline," which I had read for a while. And so he went through my article. And actually his first question was, if you're going to build this, this would definitely not be a good idea. He said, so what form is the carbon in? Do I get to specify? Do I get to be a giant chunk of diamond? And I said, I don't know. And he said, well, because diamond, it will actually burn if you get it hot enough. But that's pretty difficult. And you'd have sort of the problem-- the same thing that happened with some of the Cold War-era projects, which is if you have an explosion like this, that's this violent, the question is will it fling the thing away before it delivers enough energy to disintegrate it? So he said there's a decent chance that-- when you have this radioactive nuclear bomb going off-- that it's possible that the diamond will not be incinerated. So back in the early days when we were still doing nuclear weapons tests, there was this series of tests underground. One of them was Operation Plumbbob, where they had a nuclear weapon going off in an underground chamber with a shaft connecting to the surface. And the shaft had a cement plug and an iron-- some kind of heavy steel-- cap on it blocking the top of it. And some of them had been doing some calculations about when you have the incredibly high pressures in this, they have nowhere to go except up the shaft. They're going to hit this plug. And they think the plug will not actually be disintegrated by this, but it might be hurled away. And there was an interview with one of them, where he talked about it they weren't sure how fast it was-- they thought it was going to be flung / and they were coming up with some sort of high numbers for the speed. And so they what did is they trained a high-speed camera about a quarter mile away on the mouth of the shaft, just to catch anything that happened. And so they detonated the bomb and they had this high-speed camera-- I think they said it was running around 300 frames a second-- the plug that was over the top of the shaft appears in the air in one frame. So they can put a lower bound on how fast it was going, but they do not have an upper one. The lower bound is a-- I tried to run through the calculations myself using the field of view of the camera. It's a little bit tricky calculate-- but it is a double digit number of kilometers per second. One of them-- one [INAUDIBLE] was about 65 kilometers per second. And that's interesting because you'll see sometimes the Helios 2 probes that we sent around the sun are often listed as the fastest human objects-- the fastest thing we've ever made. And frame of reference questions, it's hard to figure out how to define that. But with reference to the sun, the thing it was going around, they dropped so close, they whipped around it really fast, and at the bottom of that they got up to about around 60 or 70 kilometers per second. Depending on exactly how fast this manhole cover that was on top of this thing was going, it is possible that for a moment this was the fastest object ever built. And there was some thought that this might have-- if it was going at 60 kilometers a second, the escape velocity from the surface of the earth is less than 10 kilometers per second. And in fact, the escape velocity from the whole solar system from where we are is only about 40 kilometers per second. And so this manhole cover, which was never found, may have left-- it's possible, given its speed, it made out of the atmosphere. And I actually started doing a bunch of calculations to figure out if it was going forward from the Earth-- like in the direction of the Earth's motion. If they were pointed toward the direction the Earth was going, you get to add on the Earth's 30 kilometers a second speed around the sun, when you're trying to get up to the escape velocity. And so this thing could be going over 100 kilometers a second, which would send it straight out of the solar system. And it would be going way, way faster, even after it had lost all its speed there than the Voyager probes at their fastest. And so that would now be our first representative heading for the stars, which is a really appealing idea. And I think I came up with-- I was digging through these files trying to find what time of day did this happen, so which way would the shaft have been pointed? And I think that the Earth's speed came out as kind of a wash. But it's also sort of a moot point, because further calculations show that probably the metal cover, because it was not quite large enough, probably did not survive the impact with the atmosphere. So it would have been sort of the only-- maybe the only time in Earth's history that we've seen a meteor going directly upward, burning up in a plasma trail. And so probably that manhole cover was destroyed, but it's possible it is still out there somewhere. So when I talked to the chemist his first question was, hey, that chunk of diamond-- it's possible that's just going to be flung free from this explosion, and have landed OK. And then at the very least, I would like to go and pick it up and then use it to pay for all of the damage that I did the labs, and to the city, and all the rebuilding. And then he thought for a second. He was like, I would definitely wipe it off first, though. What was really fun is he also got to-- he said you, yeah, these reactions that you've talked about, they would definitely-- they would happen. But there are a lot of really bad ones too that you didn't even get to, you know? And he said-- he pointed out that the selenium and the bromine would react vigorously. He said the fluorine-- he said you're right that fluorine is where this whole scheme goes to hell. That the fluorine, he said, it would be OK with the neon, and it would observe sort of an "armed truce" with the chlorine, but everything else-- his exact words were "but everything else, sheesh." But you get further down the table, and he got to throw in all these fun tidbits. He said that you're right. That this would be really toxic, but also the selenium would be burning, and burning selenium is the worst thing that he'd ever smelled. And he said it's like-- he said it makes sulfur smell like Chanel. So the selenium and the tellurium and would both be really, really awful smelling. And he listening then, this would produce all these chemicals. And this would produce all these chemicals. And this one I've never worked, and this is why. You know? And I found this really, really satisfying, because when I answer these questions, people say that I write all these articles, and how come I destroy the earth so often? And how come the articles always end with everyone dying or something? And it's really because that's the questions that people ask me. That would really be the consequence of the scenario you're talking about. But I'm trying to not make them more dramatic than they are. I'm trying to tell the real story of what would happen in as fun a way as possible. But especially with the chemistry things like this, I liked going to experts to find out-- make sure I'm not overselling this. Like, is this really-- the science that I'm talking about-- really this weird and this horrifying, or it is it more complicated than that? And it's really nice to learn that, in fact, reality is way more horrifying than I was able to imagine. And I think that's been the most fun thing about doing all of this, is getting to discover all this really crazy and exciting and fun and uplifting and sometimes really terrifying stuff that the science can show us. And so we also-- we have some time. I think we're running into-- we have some time for Q&A, if anyone wants to do any questions. We've got a microphone back here. So you can just-- if anyone wants to ask any questions, you can come up there. AUDIENCE: Hi, I'm Alex Weisen. I'm the tech lead manager for Google Voice. And you've made a few comic strips on "xkcd" that mentioned Google Voice. And so I just wondered, is there anything we can do for you, anything we can help you with? RANDALL MUNROE: Which ones? Sometimes I'll have people come up and say, oh, I really liked in comic 446. Can you say, is that from experience? And then they pause for a minute. And I have a moment where I'm like, oh god, they think that I know them all by heart. Do they know them all by heart? It's weird. And so when people both cite them by number I don't know, but also now I'm trying to think, what have I said about Google? Was it nice? AUDIENCE: Yeah, it was pretty nice. You just made funny jokes. It's cool. RANDALL MUNROE: I've had some fun transcripts delivered to my phone. I really enjoy the sort of the word play aspect of it. Like, here is how the transcript rendered my dad talking. Now it's like a crossword puzzle, figuring out what did he actually say? But I assume that a huge amount of that is the quality of the connection and everything. But I am kind of enjoying that part. So I would say keep that up. No, I've been really enjoying the rate at which the voice recognition has been improving. Especially recently, to where we're finally getting to the point where do not have to mode switch five times to get voice commands up, to then say, OK, now I want to search for this in a clear, loud voice projecting to everyone. I'm really looking forward to the future where you can just kind of discretely be like, oh, what's the weather right now? OK, it's this. So I'm enjoying that. And keep up the progress on that. Yeah, thank you. AUDIENCE: Hi. It's great to have you here. I missed your last talk, as I wasn't at Google yet, and I've been waiting-- waiting for this day we finally get to see Randall Munroe. RANDALL MUNROE: That's satisfying. AUDIENCE: In all of the submissions that you received for "What If," were there ever any that intrigued you, but that were just too frightening. You weren't going to touch them with a 10-foot pole? RANDALL MUNROE: Yeah, there have been a number of weird things. I had one person who in their job may have conceivably-- they asked a question about-- a fun earth science question involving nuclear weapons. And their from address, the TLD that it was coming from, and the title that was after their signature, and then some of what they described in the letter suggested that perhaps this was a person who had access to nuclear weapons. And that was a little worrying. I have also gotten ones from-- I had one that I think came from a doctor that was like, suppose that a toxin blocks the effect of so and so on a patient's so and so receptors, and it was delivered at this dose, what would be the effect of this toxin? And that's not sort of the vibe of the usual "What If" question I get. And it gave me the sense that somewhere there's a doctor who's in a hospital at a computer, and there's a nurse coming in who's like, Doctor, Doctor! Asking her, we have a patient so and so. What is your decision? What are you going to do? They have this talk, and the doctor's like, hang on. There's an internet cartoonist who I really think we should ask about this. And they're waiting for-- like, we have to wait for this week's article. But hopefully you'll tackle this for us. And so that's definitely sort of worrying. I also get a lot of questions that are very transparent attempts to get me to do people's homework. Like, what if you had a ball was on an inclined plane at this many degrees that was this many centimeters long, and you let it go? Like, how many seconds do you think it would take to hit the bottom? It's like, nice try. And then I think, actually, the most worrying ones are-- there are a bunch where they're totally reasonable, legitimate, answerable questions that I still just refuse to tackle. Which are like-- one of them was someone asked would it be possible to chill your teeth to such a low temperature that drinking a cup of hot coffee would cause them to shatter? And I included this question, and I have never been able to get beyond the end of that sentence without just cringing, because I imagine it. And so I have never-- I don't have the stomach to do the research to answer that question. And so there are a couple like that, where it's like this is just pushing it. But other than that, there's a huge number of what if Superhero X fought Superhero Y. And I feel like that's A, sort of hard to answer scientifically, because the powers of the superheros sort of change depending on who's writing them, and it will often be the ones who are sort of infinitely powerful, where it's not really well-defined what the limits of their powers are. But I've gotten to learn a great list of all of the near-infinite power superheroes, because people really like to pit them against each other. And part way I don't answer that is that, in addition to being hard to tackle with science, it's-- from what I understand-- that's basically the kind of question that superhero comics exist to try to answer in the first place. It's like, what if we took Hero X from mythology X and had crossover with someone from mythology y. And I was thinking that this-- but this interest in asking about infinity is a common trend, and it's not limited to just superheroes, because before that it's exactly the same impulse that leads people to ask the old question of could God make a rock so heavy that he can't lift it? And this question-- you've defined this person as infinitely powerful. How powerful are they really? Goku from "Dragon Ball Z" I gather, at some point becomes nearly infinitely powerful, because people keep asking questions about what if he fought the Hulk or Superman? And so I think this is sort of a common trend, although I was thinking that I don't think anyone has-- this has been a common trend throughout history-- but I don't know if they necessarily always combine them with the sort of pitting rivals, because I don't think anyone who's ever asked in. What if Goku "Dragon Ball Z" fought the God of the Old Testament? And I don't know what science has to say about that, but if anyone does discover if they've done a crossover comic of that, please let me know. I would read that. AUDIENCE: Thanks for coming. Hope you'll be back soon. RANDALL MUNROE: Yeah. Thank you. AUDIENCE: Hi, thanks for coming. You mentioned how you've been learning a lot about different subjects that are sort of out of your original realm of study, in terms of chemistry and biology and these things. How do you go about learning enough in this new domain to be able to produce a meaningful answer to these kinds of complex questions in a complex world? RANDALL MUNROE: I think one sort of skill that I have gained that I didn't really have before this, was I have learned to read-- skim-- a whole lot of research that does not turn out to be relevant really fast. Like download 40 PDFs on some subject, skim each one looking for, does this have the equation that I'm looking for? Does this have something that I'm looking for-- and discard them really quickly, like doing blind-- going down blind avenues or dead ends. I haven't learned to avoid doing dead end research, but I've learned to do it as quickly as possible. But the other thing is people are-- whenever I write about one of these-- I'll write about some space thing, and someone will say, oh, yeah, I don't know about that. I didn't-- I know you worked at NASA. So you know about what happens when the moon collides with something or something. And it's like my formal education. I was working in a robotics lab at NASA. And I've worked on some virtual reality stuff. But the physics of the moon running into things stuff was like if we were hanging out at lunch talking about it. But I think more than anything, just there hits a point in the night where I stop getting anything productive done. And if I have Wikipedia tabs open, I'll just start reading from there, and it will never be anything useful for what I'm doing right then, but often I'll learn all about something that two weeks later is the answer to a question that comes up. So just a lot of totally unfocused reading of Wikipedia or weird papers ends up coming in handy later on. AUDIENCE: And lots of Googling? RANDALL MUNROE: Hm? AUDIENCE: And lots of Googling? RANDALL MUNROE: Yes, I've actually found-- so everyone's like, oh, yeah, do spend a lot of time on ResearchGate, JSTOR-- how do you pronounce-- A-R-X-I-V? That's another I've never heard. Is it just archive? Yeah, but I found that-- and even Google Scholar and stuff-- and I use all of those, but I have found that if you're looking for weird research that maybe isn't the easiest to find-- maybe it was a government study in the Cold War that has been declassified, but not really they haven't published [INAUDIBLE]. I have a lot more luck just googling for the search terms that I would been looking for and adding "PDF" to the end. In terms of does this get me a paper that answers the question I'm looking for, that has a higher hit rate than any of the specialized services. So I appreciate that. AUDIENCE: Cool, thank you. RANDALL MUNROE: Thank you. AUDIENCE: Hi, so you had a lot of fans show up. And that's just to hear you talk. You must get a bunch of requests on the email address that you use for us to ask you questions. I was wondering how many of those do you get, and how do you whittle them down? And really what I would like to know is how do I ask you the perfect question that you end up answering? RANDALL MUNROE: I don't know. So it's really nice to that so many of you came out here. Although I feel like that's easier to do when it's appearing at a workplace, because it's like, so do I work on the thing that I'm supposed to do this evening, or go hang out of the talk about comics? I'm flattered, but I figure-- But there are definitely a lot of questions submitted, and I will admit to doing-- there's some sort of filters that I put on the inbox. So after a little bit I started filtering out the names of all of the invulnerable superheroes, because they were just too many questions about them that were never ones that I was going to be able to answer. I also filtered out the word "woodchuck" after week one. Because the first time someone submitted "hey, how much would could a woodchuck really chuck if a woodchuck could chuck wood?" I laughed. I was like that's funny, and then the second time I was like, oh, yeah, hey, someone else thought of that joke. And then in the first week it was like 70 or 80 emails that were just the same woodchuck joke, and then by then I was like, OK, I now hate that rhyme, and I refuse to answer any questions about woodchucks on principle. But other than that, I actually find some of my favorite questions come from little kids, because adults will sort of try to be really clever about it and come up with a question that suggests all these horrible consequences, and they've set up a scenario that's going to result in a mushroom cloud engulfing wherever it is you're doing this. Whereas little kids will ask extremely straightforward questions like, I want to build a billion-story building. Can I do that? And then answering takes you in a bunch of unexpected directions. So my advice to people who are submitting questions is mostly ask little kids for questions, because they have some of the best ones. AUDIENCE: Cool, thank you. RANDALL MUNROE: Yeah, thank you. AUDIENCE: I guess I am the last one here, so I want to ask you something I asked Vin Diesel, because you have a lot in common with him. RANDALL MUNROE: OK, wait. Hang on. Before you ask your question, which parts? AUDIENCE: I think both of you have a real passion for geeky things. RANDALL MUNROE: Yeah, he was a role playing guy, wasn't he? AUDIENCE: Yeah, so I was wondering if you'd want to join us for Dungeons and Dragons? RANDALL MUNROE: Sure, so here's the qualifier-- the thing for this-- possibly. Coming back to this theme again, the more social geeky pursuits, I didn't really get into until I went away to college. And then eventually got a job working with more geeky people. So when I was a kid, I knew about Dungeons and Dragons but never actually played it with people. So what I did is I got a bunch of-- my closest exposure to it was the single player NetHack and derivatives, Angband and stuff, which I played through for several years every day. So all of my Dungeons and Dragons knowledge is secondhand from that. The one time I did play Dungeons and Dragons, the DM was like, OK, your character. You've at this point picked up a weapon, which only you can pick it up. It's magically enchanted. If anyone else-- it's a 10-pound ax-- or something, and if anyone else picks it up, it weighs 1,000 pounds. If anyone else touches it, in fact, it weighs 1,000 pounds. And I was immediately like, OK, wait a minute. Is there a water wheel in this town? Can I get someone else from the party or a peasant or someone? I want to strap the ax to the water wheel, and have the handle sticking out, like my hand on one side and their hand on the other side. And we'll get it spinning. And then we'll have it weighted. So it's really heavy, but then it comes around to my side, and I touch it, and suddenly it's light, and the it starts spinning faster and faster. And then we get it spinning up to the speed that's the maximum speed that the water wheel can handle. And then we pull the axles out so it drops to the ground. And then we've got this giant heavy water wheel spinning at a fantastic rate. It'll go tearing across the landscape toward the enemies who we're trying to fight. There was this very nice woman in college who invited me to play that one time and then didn't invite me back. My D&D experience is limited, but I would love to try it out. AUDIENCE: Thank you very much. RANDALL MUNROE: And thank you.