WEBVTT - Little Boy and Fat Man 0:00:04.440 --> 0:00:12.320 Welcome to Tech Stuff, a production from iHeartRadio. Hey there, 0:00:12.320 --> 0:00:16.160 and welcome to tech Stuff. I'm your host, Jonathan Strickland. 0:00:16.160 --> 0:00:19.960 I'm an executive producer with iHeartRadio. And how the tech 0:00:20.000 --> 0:00:24.480 are Yet. So this past weekend two films did quite 0:00:24.480 --> 0:00:26.920 well at the box office here in the United States. 0:00:27.240 --> 0:00:31.800 And while I could do an episode about Barbie, talking about, 0:00:31.880 --> 0:00:34.479 you know, some of the Barbie dolls and various toys 0:00:34.520 --> 0:00:38.320 that have crossed over into the tech sphere and some 0:00:38.360 --> 0:00:41.519 of the issues that those toys created, primarily regarding you know, 0:00:41.600 --> 0:00:45.000 privacy concerns, I thought instead we'd talk about the atomic 0:00:45.080 --> 0:00:48.560 bombs used in World War Two Batman and Little Boy, 0:00:48.880 --> 0:00:51.960 because you know, Oppenheimer was also a pretty big hit 0:00:52.280 --> 0:00:55.760 at the box office this weekend. So in World War two, 0:00:55.920 --> 0:00:59.639 the United States dropped two different types of atomic bombs 0:00:59.680 --> 0:01:04.840 on the US hit Hiroshima with a bomb called Little Boy, 0:01:05.520 --> 0:01:10.360 and Little Boy used uranium enriched uranium as the fissionable 0:01:10.480 --> 0:01:15.639 material that would produce the intense energy of the bomb. 0:01:16.319 --> 0:01:20.679 And then the US dropped a bomb on Nagasaki. That 0:01:20.760 --> 0:01:25.560 one was called fat Man. Fat Man had a plutonium core, 0:01:25.959 --> 0:01:30.360 not uranium. But how did these bombs actually work well. 0:01:30.720 --> 0:01:33.959 First of all, it boils down to atomic physics. So 0:01:34.000 --> 0:01:39.080 some heavier atoms are unstable, and you know, with the 0:01:39.160 --> 0:01:43.240 right instigating incident or with enough time, the heavier atom 0:01:43.319 --> 0:01:48.200 will split into smaller atoms and release neutrons. Also in 0:01:48.240 --> 0:01:52.520 the process doing this ends up also releasing a tremendous 0:01:52.520 --> 0:01:56.480 amount of energy. Splitting the atom is also called fission, 0:01:57.160 --> 0:01:59.720 and this is the type of technology our nuclear power 0:01:59.760 --> 0:02:03.440 play rely upon. The big difference being that in nuclear 0:02:03.480 --> 0:02:08.480 power plants you have a controlled nuclear fission reaction and 0:02:08.639 --> 0:02:13.880 in a bomb, ultimately you have an uncontrolled chain reaction 0:02:14.720 --> 0:02:18.600 that releases a tremendous amount of energy. Now, you do 0:02:18.680 --> 0:02:21.320 get a whole lot of energy just by splitting one atom, 0:02:21.360 --> 0:02:23.600 but you could really get a big release if you 0:02:23.639 --> 0:02:27.000 were able to set up a chain of atomic reactions. 0:02:27.400 --> 0:02:30.720 So how do you do that? How did the engineers 0:02:30.760 --> 0:02:34.680 and scientists who worked for the Manhattan Project, because that 0:02:34.840 --> 0:02:37.360 was the name of the project that developed the atomic 0:02:37.400 --> 0:02:42.880 bomb for the United States, how would they guarantee a 0:02:43.000 --> 0:02:46.560 chain reaction? Well, let's talk about those two elements that 0:02:46.600 --> 0:02:49.760 were used in each of the atomic bombs, or rather, 0:02:50.160 --> 0:02:54.560 you know uranium in Little Boy and plutonium and fat Man. 0:02:55.040 --> 0:02:58.360 So the type of uranium that little Boy used was 0:02:58.560 --> 0:03:03.840 uranium two thirty five. Fat Man was dependent upon plutonium 0:03:04.000 --> 0:03:07.679 two thirty nine. Both of these are isotopes, and both 0:03:07.760 --> 0:03:13.119 of these isotopes regularly undergo fission. They are very much 0:03:13.200 --> 0:03:17.440 ready to split apart with the right situation. Now, the 0:03:17.480 --> 0:03:21.760 way you start all that is that you shoot the 0:03:21.840 --> 0:03:25.440 isotope with a fast moving particle, essentially a neutron neutrally 0:03:25.520 --> 0:03:29.080 charged particle, sub atomic particle that if you were to 0:03:29.120 --> 0:03:32.920 shoot that at a uranium two thirty five atom and 0:03:33.000 --> 0:03:37.720 it makes contact, Essentially, the two thirty five would absorb 0:03:37.840 --> 0:03:41.080 that neutron and then the atom would split apart and 0:03:41.120 --> 0:03:44.720 in the process also release other neutrons, So that neutron 0:03:44.840 --> 0:03:48.400 strikes the isotope, you get the split, you get more 0:03:48.440 --> 0:03:52.800 neutrons released. If you've got more atoms of that same 0:03:52.880 --> 0:03:56.480 heavy atom, like U two thirty five, packed together, then 0:03:56.640 --> 0:04:01.400 the release neutrons can make contact with those uranium atoms 0:04:01.840 --> 0:04:04.760 and then cause the reaction to continue. So you've got 0:04:04.800 --> 0:04:08.000 to pack enough of these atoms together to increase the 0:04:08.120 --> 0:04:11.360 chances of that happening. You know, keep in mind, like 0:04:11.400 --> 0:04:14.400 when we're talking about atoms like very very tiny stuff 0:04:14.680 --> 0:04:17.520 and subatomic particles even tinier. You've got to pack a 0:04:17.520 --> 0:04:20.280 whole lot of it together to increase the odds of 0:04:20.320 --> 0:04:25.240 a neutron hitting an isotope. Otherwise, if it doesn't, if 0:04:25.240 --> 0:04:28.480 the neutron ends up being absorbed by something else or 0:04:28.839 --> 0:04:32.760 escapes or whatever, then it doesn't continue the reaction. You 0:04:32.880 --> 0:04:34.600 have to have it set up so it creates the 0:04:34.640 --> 0:04:37.560 sort of domino effect, except we're not talking on one 0:04:37.560 --> 0:04:40.200 to one relationship here. It'd be a domino effect where 0:04:40.600 --> 0:04:44.640 you know, you have a domino that, when you knock 0:04:44.680 --> 0:04:47.800 it over, makes contact with two other dominoes at the 0:04:47.800 --> 0:04:51.000 same time, knocking both of those over, which in turn 0:04:51.600 --> 0:04:54.120 make contact with two other dominoes, and so on and 0:04:54.160 --> 0:04:57.080 so forth, so that by knocking one domino over, you'll 0:04:57.120 --> 0:05:00.520 ultimately knock over a whole bunch. Same idea here, except 0:05:00.520 --> 0:05:04.719 we're talking about isotops. We're talking about individual atoms and 0:05:04.760 --> 0:05:07.200 packing enough of them together so that you do get 0:05:07.200 --> 0:05:10.479 this chain reaction. And once you do that and you 0:05:10.560 --> 0:05:14.000 have nothing there to rain in that chain reaction, you 0:05:14.080 --> 0:05:17.720 get a truly tremendous release of energy in the process. 0:05:18.920 --> 0:05:22.600 So again we use the same sort of process in 0:05:22.680 --> 0:05:26.040 nuclear power plants. But we have tools there and processes 0:05:26.400 --> 0:05:30.880 that allow engineers to control the sequence, this rate of release, 0:05:31.520 --> 0:05:35.680 and that way they can release enough in order to 0:05:35.800 --> 0:05:39.280 generate electricity. So, in other words, they can allow this 0:05:39.360 --> 0:05:44.720 process to occur at a specific rate, and then the 0:05:44.839 --> 0:05:46.760 energy they release in the process they can use to 0:05:46.800 --> 0:05:49.680 generate electricity. I'm actually skipping a step here because the 0:05:49.839 --> 0:05:53.720 energy that gets released ends up essentially being incredibly intense heat, 0:05:53.960 --> 0:05:56.680 which you then use to turn water into superheated steam, 0:05:57.279 --> 0:06:01.520 use that to turn turbines which generate electricity. The steam 0:06:01.520 --> 0:06:04.960 eventually condenses down into water, and then that's in its 0:06:04.960 --> 0:06:07.800 own closed system, and you just keep doing that. But 0:06:07.839 --> 0:06:11.280 in a bomb, you don't have these tools and processes 0:06:11.680 --> 0:06:13.760 to keep it under control. Right. You don't have a 0:06:13.800 --> 0:06:17.640 way of absorbing neutrons, for example, So the whole point 0:06:17.680 --> 0:06:21.240 is to get that uncontrolled chain reaction that, by the way, 0:06:21.320 --> 0:06:25.120 is not a foregone conclusion. You can't really control where 0:06:25.160 --> 0:06:28.640 a release neutron is going to go, So again, you 0:06:28.760 --> 0:06:32.520 have to have the right amount of fissionable material in 0:06:32.560 --> 0:06:36.080 the right density, otherwise your bomb will only release a 0:06:36.080 --> 0:06:39.039 fraction of the energy you were planning on and you 0:06:39.160 --> 0:06:41.920 won't get the effect you were hoping for. It won't 0:06:41.920 --> 0:06:45.480 be nearly as devastating. And the only reason to use 0:06:45.520 --> 0:06:49.880 a weapon as devastating as an atomic bomb or nuclear 0:06:49.920 --> 0:06:56.000 weapon is to convince an opponent to surrender, because it's 0:06:56.080 --> 0:06:59.320 just such a truly devastating weapon, and it's not like 0:06:59.360 --> 0:07:03.560 you can use it to target specifically just military installations 0:07:03.680 --> 0:07:08.080 for example. You're going to be taking out civilian sites 0:07:08.160 --> 0:07:12.960 and innocent people who are not soldiers. So it's a horrible, 0:07:13.000 --> 0:07:15.760 horrible weapon, and the only reason you use it is 0:07:15.840 --> 0:07:22.240 to convince your opponent to surrender. Anyway, in order to 0:07:22.280 --> 0:07:23.800 do that, you have to make sure you've got enough 0:07:23.840 --> 0:07:27.040 fissionable material in your bomb, or else it's not going 0:07:27.080 --> 0:07:29.520 to have the effect you want and the conflict will 0:07:29.600 --> 0:07:32.240 just continue. So you have to reach what is called 0:07:32.360 --> 0:07:38.960 critical mass. This is the mass of fissionable material you 0:07:39.120 --> 0:07:43.600 need in order to start a chain reaction. That mass 0:07:43.640 --> 0:07:48.080 is completely dependent upon things like how much volume the 0:07:49.080 --> 0:07:51.720 fissionable material takes up, which we'll talk about when we 0:07:51.800 --> 0:07:54.680 get to the fat Man. So the more material you have, 0:07:55.040 --> 0:07:57.440 or the more mass you have, the greater the odds 0:07:57.480 --> 0:08:00.440 are that neutrons that get released in this reaction are 0:08:00.480 --> 0:08:05.200 going to hit another heavy atom, another heavy isotope, and 0:08:05.240 --> 0:08:07.520 you've arrived at critical mass when it's likely that a 0:08:07.560 --> 0:08:11.000 release neutron is going to create a subsequent heavy atom 0:08:11.040 --> 0:08:14.480 to split and release more neutrons. Now, finding out what 0:08:14.520 --> 0:08:17.240 it would take to achieve critical mass, that was a 0:08:17.280 --> 0:08:20.720 big part of the work over at the Manhattan Project 0:08:20.800 --> 0:08:24.280 was to actually determine what that would be. How much 0:08:24.600 --> 0:08:28.200 enriched uranium or how much plutonium two thirty nine would 0:08:28.200 --> 0:08:31.280 you actually need in order to achieve this and have 0:08:31.400 --> 0:08:36.439 it be a chain reaction that actually works. So Oppenheimer 0:08:36.840 --> 0:08:39.760 and others, he wasn't the only one, obviously, this was 0:08:39.800 --> 0:08:42.559 a huge team of scientists and engineers who worked on 0:08:42.600 --> 0:08:45.800 the Manhattan Project. They were trying to develop a weapon 0:08:45.840 --> 0:08:49.199 that could initiate an atomic reaction that would rapidly consume 0:08:49.320 --> 0:08:53.240 a core of heavy atoms to generate an enormous destructive 0:08:53.280 --> 0:08:55.920 wave of energy. That was the whole goal, and they 0:08:55.960 --> 0:08:58.439 came up with two different ways of doing that using 0:08:58.480 --> 0:09:01.360 the two different elements of you know, uranium two thirty 0:09:01.360 --> 0:09:03.839 five in one case and plutonium two thirty nine in 0:09:03.880 --> 0:09:07.960 the other. So first we'll talk about uranium two thirty five, 0:09:08.240 --> 0:09:12.520 also known as refined uranium, because most of the uranium 0:09:12.600 --> 0:09:16.600 we encounter naturally on Earth is a totally different isotope. 0:09:16.640 --> 0:09:19.680 It's not you two thirty five, it's uranium two thirty eight. 0:09:20.240 --> 0:09:23.400 And you might wonder why does that make a difference, 0:09:23.559 --> 0:09:26.880 Like why is one type of uranium useful for weapons 0:09:27.080 --> 0:09:29.760 and the other one isn't. Well to do that, we 0:09:29.840 --> 0:09:33.800 have to talk about isotopes. So an isotope is just 0:09:34.120 --> 0:09:36.920 a form of an element, right, you have, and when 0:09:36.920 --> 0:09:39.439 you're talking about isotopes, you're talking about two or more 0:09:40.040 --> 0:09:43.360 forms of the same element. Each isotope of an element 0:09:43.400 --> 0:09:45.640 will have the same number of protons as all the 0:09:45.679 --> 0:09:48.679 other isotopes of that element, right, because if you were 0:09:48.720 --> 0:09:52.360 to add or subtract protons, you would change the element itself. 0:09:52.400 --> 0:09:55.240 It would no longer be the element you started with. 0:09:55.720 --> 0:09:59.239 So the number of protons remains consistent across all isotopes. 0:10:00.000 --> 0:10:02.280 The difference is in the number of neutrons that are 0:10:02.280 --> 0:10:06.440 in the nucleus. So uranium two thirty five has one 0:10:06.559 --> 0:10:10.559 hundred forty three neutrons in its nucleus. Uranium two thirty 0:10:10.559 --> 0:10:15.199 eight has one hundred forty six neutrons, And this might 0:10:15.240 --> 0:10:18.360 lead you to say, well, neutrons are neutrally charged. That's 0:10:18.400 --> 0:10:21.360 why they're called neutrons. They have a neutral charge. How 0:10:21.400 --> 0:10:24.960 does that make it a difference, Like, what difference do 0:10:25.120 --> 0:10:29.640 three neutrons make? Well, isotopes can actually have different chemical 0:10:29.679 --> 0:10:32.800 properties from one another, which is kind of crazy, right, 0:10:32.800 --> 0:10:35.360 You're talking about two things of the same element, but 0:10:35.360 --> 0:10:39.400 they can have different chemical properties. So uranium two thirty 0:10:39.400 --> 0:10:42.520 five and uranium two thirty eight are both isotopes of uranium, 0:10:42.520 --> 0:10:45.560 but they don't always behave the same way. So let's 0:10:45.600 --> 0:10:48.440 take uranium two thirty eight. Now, I mentioned that to 0:10:48.559 --> 0:10:53.040 initiate nuclear fission, you would fire a neutron at an 0:10:53.040 --> 0:10:57.000 isotope and it would split that isotope up. But if 0:10:57.040 --> 0:10:59.440 you were to fire a neutron at uranium two thirty eight, 0:10:59.800 --> 0:11:03.040 instead of splitting up, it could just capture that neutron 0:11:03.200 --> 0:11:06.640 and become uranium two thirty nine. So instead of two 0:11:06.679 --> 0:11:08.600 thirty eight, you got two thirty nine, but you don't 0:11:08.640 --> 0:11:11.840 get that split. And that means that if uranium two 0:11:11.920 --> 0:11:15.480 thirty eight absorbs the neutron and becomes uranium two thirty nine, 0:11:16.400 --> 0:11:19.400 there's no chain reaction because it didn't split apart. It 0:11:19.440 --> 0:11:22.920 didn't release more neutrons to cause that reaction to continue. 0:11:24.120 --> 0:11:26.520 So your reaction would go nowhere. You would just have 0:11:26.840 --> 0:11:29.800 uranium two thirty nine now, and that wouldn't do you 0:11:29.880 --> 0:11:33.520 any good. You wouldn't have an explosion. Uranium two thirty 0:11:33.559 --> 0:11:36.000 five is a totally different story. If you fire a 0:11:36.040 --> 0:11:38.679 neutron at uranium two thirty five, you're gonna get an 0:11:38.720 --> 0:11:41.760 atomic split and a whole butt load of energy in 0:11:41.800 --> 0:11:45.559 the process. But here's the thing. Uranium two thirty eight, 0:11:45.640 --> 0:11:48.120 that's the stuff that's abundant. That's the stuff we can 0:11:48.160 --> 0:11:50.960 find naturally on Earth. Uranium two thirty five makes up 0:11:51.040 --> 0:11:55.360 less than one percent of naturally existing uranium, which meant 0:11:55.720 --> 0:11:59.400 the scientists had to develop a means to refine uranium 0:11:59.400 --> 0:12:04.320 two thirty eight into uranium two thirty five. All Right, 0:12:04.559 --> 0:12:06.280 we're going to take a quick break. When we come back, 0:12:06.320 --> 0:12:09.599 we'll talk more about the challenges that the engineers and 0:12:09.640 --> 0:12:22.720 scientists of the Manhattan Project were facing. We're back now. 0:12:22.840 --> 0:12:27.319 During the Manhattan Project, obviously time was ticking. This wasn't 0:12:27.360 --> 0:12:29.360 some R and D project that could just take as 0:12:29.440 --> 0:12:31.960 much time as necessary. There was actually a war on 0:12:32.720 --> 0:12:35.240 there was a concern that access nations could be developing 0:12:35.280 --> 0:12:38.080 their own atomic weapons. So the United States poured a 0:12:38.160 --> 0:12:44.720 lot of resources into this research, and the desire was 0:12:44.760 --> 0:12:48.120 to find a process that would work, and it didn't 0:12:48.160 --> 0:12:51.200 matter which process it was, So actually the Manhattan Project 0:12:51.280 --> 0:12:57.520 was pursuing different strategies simultaneously. One of the overseers of 0:12:57.559 --> 0:13:01.960 the Manhattan Project was General Leslie Groves, who authorized four 0:13:02.040 --> 0:13:05.480 separate projects to explore how to refine you two thirty 0:13:05.520 --> 0:13:09.480 eight into You two thirty five. And again they wanted results. 0:13:09.520 --> 0:13:11.400 They didn't really care which one was going to be 0:13:11.440 --> 0:13:14.760 the best. They just needed that uranium. So the scientists 0:13:14.800 --> 0:13:18.599 already knew that standard chemical processes were not going to 0:13:18.679 --> 0:13:22.000 necessarily work to refine You two thirty eight into You 0:13:22.080 --> 0:13:25.360 two thirty five because the two isotopes, while they are different, 0:13:25.720 --> 0:13:29.080 share enough chemical similarities that it just wasn't going to 0:13:29.120 --> 0:13:34.440 be a way forward. So instead they looked at methods 0:13:34.440 --> 0:13:39.760 that included liquid thermal diffusion, gaseous diffusion, separating the components 0:13:39.760 --> 0:13:44.360 with the centrifuge, and electromagnetic separation. I should probably do 0:13:44.360 --> 0:13:48.280 an episode really that really focuses on those four specific approaches, 0:13:48.679 --> 0:13:51.679 but for the process here, it just meant that they 0:13:51.679 --> 0:13:55.600 were able to generate enough you two thirty five to 0:13:55.760 --> 0:14:00.800 make a viable weapon. So they finally got enough fissionable 0:14:00.840 --> 0:14:04.560 material to construct a bomb. They did a test bomb, obviously, 0:14:04.600 --> 0:14:09.160 but they also put together Little Boy. This bomb worked 0:14:09.160 --> 0:14:13.000 on what was called a gun type device inside of it. 0:14:13.600 --> 0:14:16.040 The bomb itself had a bunch of different elements so 0:14:16.080 --> 0:14:19.480 that it would explode the way the engineers intended. That is, 0:14:19.680 --> 0:14:22.840 it would explode in the air. This was not a 0:14:22.880 --> 0:14:25.560 bomb that was meant to collide with the ground and 0:14:25.600 --> 0:14:30.680 then explode. That would have limited its destructive capacity. So instead, 0:14:31.360 --> 0:14:35.480 the engineers designed it so that at a specific altitude 0:14:36.000 --> 0:14:38.960 it would initiate the explosion. So to achieve this, the 0:14:39.000 --> 0:14:41.840 bomb actually had several systems on board to measure when 0:14:42.440 --> 0:14:46.960 to ignite its explosive charge that would initiate the nuclear 0:14:46.960 --> 0:14:49.400 reaction inside the bomb. So the explosive charge wasn't the 0:14:49.440 --> 0:14:52.880 bomb itself. The explosive charge was kind of the trigger 0:14:53.160 --> 0:14:56.120 to start the nuclear reaction, which then would release the 0:14:56.160 --> 0:15:01.680 truly enormous amount of destructive energy. So the tools they 0:15:01.760 --> 0:15:04.480 used in order to measure altitude for the bomb so 0:15:04.480 --> 0:15:07.120 that it would go off at the correct height above 0:15:07.200 --> 0:15:12.640 the target. Included barometric press sensors. Those measure barometric pressure, 0:15:13.160 --> 0:15:17.480 so they would essentially monitor for the pressure to reach 0:15:17.560 --> 0:15:19.320 a point that would indicate that it was at the 0:15:19.400 --> 0:15:24.240 right altitude. But they also had radar altimeters on this bomb, 0:15:24.560 --> 0:15:28.000 and they were essentially shooting down radio waves toward the 0:15:28.000 --> 0:15:31.680 ground and listening back for echos, And when those echoes 0:15:31.720 --> 0:15:35.080 would indicate that the bomb was at the proper altitude, 0:15:35.840 --> 0:15:40.120 then it would trigger the explosive, the conventional explosive that 0:15:40.120 --> 0:15:45.480 would then lead to the actual nuclear reaction. So if 0:15:45.520 --> 0:15:49.320 you were able to look inside the Little Boy bomb, 0:15:50.080 --> 0:15:53.080 you would see that the conventional explosives were at the 0:15:53.120 --> 0:15:58.240 tail end of the bomb, and they would end up 0:15:58.360 --> 0:16:04.000 driving forward some thick disks of uranium two thirty five. 0:16:04.120 --> 0:16:06.080 So these disks, you know, they had a hole in 0:16:06.120 --> 0:16:09.000 the center of them, and they were at the tail 0:16:09.080 --> 0:16:11.400 end of the bomb. Like I said, the explosive would 0:16:11.440 --> 0:16:16.880 go off, it would end up propelling these discs forward 0:16:16.920 --> 0:16:19.640 toward the nose end of the bomb, just like a 0:16:19.880 --> 0:16:23.760 gun would propel a bullet, Like you know when the 0:16:24.200 --> 0:16:28.600 gunpowder inside a cartridge would ignite the gases expanding would 0:16:28.640 --> 0:16:31.920 push the bullet through the barrel of a gun, similar 0:16:31.960 --> 0:16:35.880 in that case, except there's no open end of this gun, 0:16:36.360 --> 0:16:41.160 So this stack of thick disks would shoot forward. On 0:16:41.240 --> 0:16:44.640 the opposite end of the bomb. In the nose end 0:16:44.760 --> 0:16:48.040 of the bomb would be a stack of uranium two 0:16:48.120 --> 0:16:50.320 thirty five that were at the diameter, so they would 0:16:50.360 --> 0:16:54.360 fit inside those thick disks. So what happens is you've 0:16:54.400 --> 0:16:58.080 got these two halves of a core essentially that came together, 0:16:58.960 --> 0:17:02.320 and now you suddenly had this solid core of uranium 0:17:02.360 --> 0:17:09.000 two thirty five. Also, there was some polonium inside this bomb. 0:17:09.080 --> 0:17:14.240 The polonium would actually act as the release of neutrons 0:17:14.240 --> 0:17:17.640 that would start the whole reaction going. So the conventional 0:17:17.680 --> 0:17:21.240 explosives were necessary to get the kinetic energy that would 0:17:21.320 --> 0:17:27.840 then launch this nuclear fission process that quickly became an 0:17:27.920 --> 0:17:32.040 uncontrolled chain reaction and would release an enormous amount of energy. 0:17:32.280 --> 0:17:36.560 In total, the Little Boy contained sixty four kilograms of 0:17:36.760 --> 0:17:45.720 enriched uranium. That's a lot of uranium, and the explosion 0:17:46.080 --> 0:17:50.000 it generated was the equivalent of fifteen kilo tons. So 0:17:50.040 --> 0:17:54.480 when you hear explosives being talked about in kilotons or megatons, 0:17:54.520 --> 0:17:58.359 whatever it may be. That's actually talking about how many 0:17:58.520 --> 0:18:01.760 tons of TNT it would take to get an equivalent 0:18:02.359 --> 0:18:05.919 release of energy. So fifteen kilotons means you would need 0:18:06.000 --> 0:18:13.080 fifteen thousand tons of TNT to get the equivalent explosion. So, yeah, 0:18:13.400 --> 0:18:19.240 you had this bomb that at the right altitude would 0:18:19.240 --> 0:18:22.280 have a gunshot essentially go off inside the bomb, the 0:18:22.320 --> 0:18:25.400 two halves would come together, some neutrons would get released, 0:18:25.880 --> 0:18:30.560 the nuclear reaction would immediately follow. You would get an instantaneous, 0:18:30.960 --> 0:18:35.760 uncontrolled chain reaction. And this truly tremendous amount of energy 0:18:35.800 --> 0:18:38.879 released overhead of the city because again they thought that 0:18:38.960 --> 0:18:41.560 if they could release the energy in the air, they 0:18:41.560 --> 0:18:46.400 would cause way more damage. It's hard to get your 0:18:46.400 --> 0:18:49.640 mind wrapped around how much damage you're talking about. At 0:18:49.680 --> 0:18:53.720 ground zero, where Little Boy exploded, there was a zone 0:18:53.760 --> 0:18:56.760 of around like zero point thirty six square kilometers that 0:18:56.840 --> 0:19:01.800 was just totally devastated. That was total, total destruction. Buildings 0:19:02.440 --> 0:19:06.359 were leveled, Any buildings that were remain standing had such 0:19:06.440 --> 0:19:11.520 structural damage that they were unstable. It would be possible 0:19:11.800 --> 0:19:16.280 to have survived in that blast zone initially anyway, if 0:19:16.320 --> 0:19:22.080 you were in a truly strong, stable structure underground really, 0:19:22.600 --> 0:19:25.040 so like if you were at the bottom of a 0:19:25.080 --> 0:19:30.160 really solid parking deck that wasn't just completely crushed by 0:19:30.240 --> 0:19:33.520 the energy of this explosion, you could have survived the 0:19:33.560 --> 0:19:37.679 initial blast potentially. However, there would be other issues, like 0:19:37.800 --> 0:19:41.359 the intense amount of radiation would certainly cause problems that 0:19:41.359 --> 0:19:47.560 wouldn't be just the concussive force of this energy radiating outward. 0:19:49.000 --> 0:19:52.600 So yeah, pretty much at ground zero, you would have 0:19:52.720 --> 0:19:57.480 people who likely would not survive either with the structures. 0:19:57.920 --> 0:20:00.399 Beyond that, you would have a zone that would be 0:20:00.400 --> 0:20:03.560 called like a moderate damage zone that could extend out 0:20:03.560 --> 0:20:06.399 to a radius of around a mile or one point 0:20:06.400 --> 0:20:11.440 six kilometers from the point of detonation. Here you would 0:20:11.480 --> 0:20:14.880 still have substantial damage to structures. Some of them might 0:20:14.960 --> 0:20:17.120 remain standing, but a lot of them would be leveled. 0:20:17.640 --> 0:20:20.479 And depending upon where you were at the moment, and 0:20:20.720 --> 0:20:22.679 if you were in a stable structure, you might have 0:20:23.359 --> 0:20:26.400 made it through. You might have survived within that moderate zone, 0:20:26.400 --> 0:20:28.719 but you would likely be in need of urgent medical 0:20:28.760 --> 0:20:31.719 attention due to other things. Like you got to remember, 0:20:32.880 --> 0:20:37.080 this explosion, it would create a like a fire ball 0:20:37.280 --> 0:20:39.600 or a wall of fire really that would extend out 0:20:39.720 --> 0:20:43.240 very quickly, and it was intense enough to vaporize you 0:20:43.320 --> 0:20:47.080 if you were just outside. I mean, it was incredibly 0:20:47.119 --> 0:20:50.920 intense energy. Beyond the moderate zone, then you have the 0:20:51.000 --> 0:20:55.120 light damage zone. This could extend ten miles out from 0:20:55.160 --> 0:20:59.639 ground zero. And even in this light damage zone, you 0:20:59.680 --> 0:21:04.199 could have, you know, an increase in air pressure that 0:21:04.280 --> 0:21:07.840 would cause all the windows to shatter. From there, you know, 0:21:07.880 --> 0:21:11.199 you might have more or less superficial damage from the 0:21:11.240 --> 0:21:16.280 actual physical blast, but again you still have the issues 0:21:16.320 --> 0:21:21.800 with radiation, and obviously the damage would create other problems, 0:21:21.800 --> 0:21:25.119 like you would get fires, and it would wipe out utilities. 0:21:25.800 --> 0:21:30.080 Truly devastating weapon. I know I'm using that word a lot, 0:21:30.119 --> 0:21:33.880 but I can't think of a word that's more fitting. Now. 0:21:33.920 --> 0:21:37.280 It's actually really hard to estimate how many people died 0:21:37.720 --> 0:21:42.240 from the detonation of Little Boy. There's a pretty huge 0:21:42.880 --> 0:21:46.439 span of estimates here, Like on the low end, on 0:21:46.520 --> 0:21:50.080 the low end of estimates, it's around seventy thousand who 0:21:50.160 --> 0:21:52.760 died as a result of Little Boy exploding. On the 0:21:52.800 --> 0:21:55.280 high end, you're talking one hundred and forty thousand, twice 0:21:55.320 --> 0:21:57.840 as many. It's a really tough question to answer. For 0:21:57.920 --> 0:22:02.640 one thing. Japanese authorities didn't have a really good handle 0:22:02.680 --> 0:22:05.480 on how many people were living in these cities in 0:22:05.520 --> 0:22:08.359 the first place, so it's hard to say, you know, 0:22:08.359 --> 0:22:13.040 how many people were missing afterward. And then they're also 0:22:13.160 --> 0:22:15.480 tougher parts of the question, like do you just count 0:22:15.600 --> 0:22:19.800 the deaths that happened as a result of the initial 0:22:19.840 --> 0:22:23.000 blast or the fires that were produced as part of it, 0:22:24.200 --> 0:22:27.920 What about other hazards that were more long term, where 0:22:28.400 --> 0:22:32.239 you know, it wasn't initially from the explosion, maybe it 0:22:32.320 --> 0:22:36.520 was in the hours or days or weeks that followed it, 0:22:36.800 --> 0:22:39.919 or if you're talking about radiation, what about the months 0:22:40.000 --> 0:22:43.640 or years that followed. So it does make it very, 0:22:43.880 --> 0:22:46.919 very very hard to estimate the number of deaths, but 0:22:47.040 --> 0:22:50.159 clearly it was in the tens of thousands, and potentially 0:22:50.280 --> 0:22:54.359 well over one hundred thousand, just or Hiroshima. All right, 0:22:54.400 --> 0:22:56.400 we're going to take another quick break. When we come back, 0:22:56.800 --> 0:23:09.800 we'll talk about fat Man and Nagasaki. Okay, So I 0:23:09.800 --> 0:23:14.480 had mentioned that Little Boy used enrich uranium as its 0:23:14.600 --> 0:23:21.200 fissionable material. Fatman used plutonium, and this meant that the 0:23:21.320 --> 0:23:25.439 method that Little Boy used to initiate that nuclear reaction, 0:23:25.560 --> 0:23:29.720 that gun method wouldn't have worked with fat Man. It 0:23:29.720 --> 0:23:32.919 would actually have caused the bomb to undergo spontaneous vision 0:23:33.040 --> 0:23:36.280 before the gun mechanism could even fire, which means the 0:23:36.280 --> 0:23:38.359 bomb would lose a lot of its energy before it 0:23:38.359 --> 0:23:42.600 could even explode. So again, you wanted to maximize the 0:23:42.640 --> 0:23:44.840 effectiveness of this weapon, or at least that's what the 0:23:45.280 --> 0:23:48.680 scientists and engineers wanted to do, because the whole purpose 0:23:49.119 --> 0:23:52.600 was to create a weapon so terrible that your opponent 0:23:53.200 --> 0:23:57.199 surrenders rather than risk being hit by it again. So 0:23:57.280 --> 0:23:58.920 the team had to come up with a different way 0:23:59.520 --> 0:24:03.879 to have the mechanism explode. So one of the problems 0:24:03.880 --> 0:24:06.720 that they faced was actually that they needed to use 0:24:06.720 --> 0:24:12.320 plutonium two thirty nine, but their reactors couldn't create pure 0:24:12.680 --> 0:24:16.800 plutonium two thirty nine flawlessly. They kept creating trace amounts 0:24:16.800 --> 0:24:21.280 of plutonium two forty and plutonium two forty that isotope 0:24:21.320 --> 0:24:25.359 is more prone to spontaneous fission than plutonium two thirty nine. 0:24:25.680 --> 0:24:28.199 So what they needed was they needed a way to 0:24:28.359 --> 0:24:34.119 have a subcritical mass of plutonium. They needed it so 0:24:34.200 --> 0:24:39.240 that it would not spontaneously undergo fission because the atoms 0:24:39.240 --> 0:24:43.000 would be too widely spaced apart so you needed to 0:24:43.040 --> 0:24:46.760 be subcritical until the moment when you needed to initiate 0:24:47.440 --> 0:24:50.640 the nuclear reaction. Then you needed to somehow make this 0:24:50.880 --> 0:24:56.840 subcritical mass become a critical mass. So their approach was 0:24:56.960 --> 0:25:02.640 to surround a subcritical plutonium core with essentially a globe 0:25:03.200 --> 0:25:05.879 of conventional explosives. So think of like, you know the 0:25:05.920 --> 0:25:10.040 Earth has an iron core. Well, this was a explosive 0:25:10.160 --> 0:25:15.440 globe with a plutonium core. And the conventional explosives were 0:25:15.480 --> 0:25:19.280 designed so that they would ignite simultaneously and they would 0:25:19.320 --> 0:25:25.120 explode and collectively create this tremendous pressure on the plutonium 0:25:25.160 --> 0:25:28.440 core in the center implosion. In other words, that would 0:25:28.520 --> 0:25:32.320 end up squeezing this plutonium core and increasing its density, 0:25:32.400 --> 0:25:35.600 and that is what would push the plutonium core from 0:25:35.600 --> 0:25:40.880 being subcritical to critical by essentially physically squishing all those 0:25:40.920 --> 0:25:44.760 atoms closer together. Now, your subcritical plutonium mass is a 0:25:44.840 --> 0:25:49.040 critical plutonium mass, and that means that once that nuclear 0:25:49.320 --> 0:25:53.879 fission reaction can start, you've got yourself your chain reaction. Now, 0:25:54.720 --> 0:25:58.440 this was a really efficient weapon. It was much larger 0:25:58.480 --> 0:26:02.160 than Little Boy because you needed way more conventional explosives. Right, 0:26:02.240 --> 0:26:05.480 the gun method only needed a relatively small amount of 0:26:05.480 --> 0:26:09.040 conventional explosives to bring the two halves of the uranium 0:26:09.080 --> 0:26:12.960