WEBVTT - TechStuff Gets on the Radar 0:00:04.160 --> 0:00:07.160 Get in text with technology with tech Stuff from how 0:00:07.240 --> 0:00:13.840 stuff Works dot com. Hey there, and welcome to tech Stuff. 0:00:13.880 --> 0:00:17.600 I'm your host, Jonathan Strickland. I'm an executive producer at 0:00:17.600 --> 0:00:21.160 how Stuff Works in a love all things tech, and 0:00:21.239 --> 0:00:25.040 today we're going to talk about radar, the history of radar, 0:00:25.120 --> 0:00:27.360 how it works, that kind of stuff. This comes to 0:00:27.440 --> 0:00:32.320 us courtesy of some listener requests. Actually two different listeners, 0:00:32.440 --> 0:00:36.120 Scott and Doug both asked about this. Doug specifically was 0:00:36.159 --> 0:00:39.800 curious about radar guns. But the technology is pretty simple 0:00:39.840 --> 0:00:43.600 once you know the the underlying principles. So I'm gonna 0:00:43.800 --> 0:00:46.000 lump them all together here. Plus I've talked a lot 0:00:46.040 --> 0:00:50.279 about radar recently, with topics on folks like Alfred Lee 0:00:50.320 --> 0:00:54.600 Loomis and his Loran navigation system, so a lot of 0:00:54.600 --> 0:00:57.160 that's going to tie in here as well. Now, to 0:00:57.240 --> 0:01:01.080 begin with, in order to understand radar and all the 0:01:01.160 --> 0:01:04.720 different principles behind it, we have to look back to 0:01:04.800 --> 0:01:08.440 the nineteenth century, all the way back in eighteen forty two. 0:01:08.840 --> 0:01:13.119 And no, we weren't using radar in eighteen forty two. 0:01:13.520 --> 0:01:17.440 He didn't have a bunch of nineteenth century military officials 0:01:17.440 --> 0:01:19.600 trying to figure out where the next wooden boat was. 0:01:20.360 --> 0:01:24.000 But in eighteen forty two, an Austrian physicist and astronomer 0:01:24.080 --> 0:01:29.520 named Christian Johann Doppler published a paper on the determination 0:01:29.720 --> 0:01:33.280 of motion using the frequency of light in the study 0:01:33.400 --> 0:01:36.679 of the movement of stars, and this became known as 0:01:36.720 --> 0:01:40.760 the Doppler principle. And here's what he was talking about. So, 0:01:41.000 --> 0:01:45.160 light is a type of electro magnetic radiation as part 0:01:45.160 --> 0:01:48.880 of the electromagnetic spectrum. You can measure light in waves, 0:01:49.280 --> 0:01:51.920 though light can also behave as a particle, but let's 0:01:51.920 --> 0:01:54.360 put that aside for an How we're specifically talking about 0:01:54.440 --> 0:01:57.960 light in its nature as a wave, and waves have 0:01:58.120 --> 0:02:02.320 a wave length. That is where you can measure from 0:02:02.360 --> 0:02:05.440 one point on a wave to the next point that 0:02:05.600 --> 0:02:08.360 is the exact same sort of point further down the wavelength. 0:02:08.400 --> 0:02:11.360 That's the wavelength. So like the crest, if you go 0:02:11.440 --> 0:02:14.480 to the very peak and you measure to the next peak, 0:02:15.000 --> 0:02:18.320 that would be one wavelength of that wave. Visible light 0:02:18.360 --> 0:02:22.440 has a very very small wavelength. The visible light spectrum 0:02:22.520 --> 0:02:26.919 ranges from around three nine nanometers to seven hundred nanometers, 0:02:26.960 --> 0:02:30.080 and a nanometer is one billionth of a meter, so 0:02:31.080 --> 0:02:35.280 very very tiny wavelengths. Now, do you remember your pneumonic 0:02:35.320 --> 0:02:38.720 device for the color spectrum, You know, the roy G BIV, 0:02:39.160 --> 0:02:42.720 which stands for red, orange, yellow, green, blue, indigo, violet. 0:02:43.360 --> 0:02:46.280 That's not just the spectrum, that's not just the colors 0:02:46.280 --> 0:02:51.080 of a rainbow. Those colors actually represent wavelengths of descending length. 0:02:51.560 --> 0:02:55.120 So red light has the longest wavelength invisible light, and 0:02:55.240 --> 0:02:59.799 violet the shortest wavelength invisible light. All light travels at 0:02:59.840 --> 0:03:04.160 the same speed, which here you go, mind blowing fact. 0:03:04.200 --> 0:03:06.799 Here that's the speed of light. Now, keep in mind 0:03:06.840 --> 0:03:09.920 the speed of light actually changes somewhat depending upon the 0:03:09.960 --> 0:03:12.560 medium it passes through. When we typically say the speed 0:03:12.560 --> 0:03:15.799 of light, we usually mean through a vacuum, But speed 0:03:15.800 --> 0:03:18.600 of light through air is slightly slower because it's moving 0:03:18.639 --> 0:03:22.440 through a different medium. When I say slightly slower, I 0:03:22.480 --> 0:03:27.520 mean incredibly incredibly tiny difference for us, Like, it's still 0:03:28.040 --> 0:03:32.760 wicked fast. So all light travels at that speed. Really, 0:03:32.800 --> 0:03:36.800 all electromagnetic radiation travels at that speed. But this also 0:03:36.880 --> 0:03:40.600 means that shorter wavelengths of light have a higher frequency, 0:03:40.920 --> 0:03:44.000 meaning you have more instances of a wave pass a 0:03:44.080 --> 0:03:47.720 specific point within a specific amount of time. Because the 0:03:47.760 --> 0:03:50.360 waves are shorter, but they're moving at the same speed 0:03:50.400 --> 0:03:53.760 as the longer waves. Now, I used an analogy recently 0:03:54.320 --> 0:03:57.960 of a highway with cars on it. So just imagine 0:03:57.960 --> 0:03:59.920 you're standing on the side of this highway and all 0:04:00.120 --> 0:04:03.800 the cars are traveling at the same speed. Now, first, 0:04:04.160 --> 0:04:06.800 let's say that there are a there's a row of 0:04:06.800 --> 0:04:09.440 buses and they're just passing you, and they're all traveling 0:04:09.480 --> 0:04:13.320 at this particular speed, and for the purposes of this example, 0:04:13.360 --> 0:04:16.560 we'll just say it's fifty miles per hour. They're equally spaced, 0:04:16.720 --> 0:04:21.000 just inches apart from each other, so it's incredibly dangerous, 0:04:21.040 --> 0:04:23.640 but they're all moving at this fifty miles per hour 0:04:23.720 --> 0:04:27.320 speed and they're passing you. Next, imagine that there is 0:04:27.360 --> 0:04:30.200 a row of tiny smart cars that are passing you. 0:04:30.320 --> 0:04:33.479 These are also inches apart from each other, so uh, 0:04:33.520 --> 0:04:35.960 they are very close together, and they're traveling at the 0:04:36.000 --> 0:04:38.600 same speed the buses were. Earlier, they're also traveling at 0:04:38.640 --> 0:04:41.919 fifty miles per hour. You'll have more smart cars pass 0:04:42.000 --> 0:04:45.400 you by in that same amount of time because they're smaller. 0:04:45.720 --> 0:04:47.880 They're traveling at the same speed as the buses, but 0:04:48.000 --> 0:04:50.360 they have less lengths, so you get more of them. 0:04:50.400 --> 0:04:53.120 In in the same amount of time. Same thing is 0:04:53.160 --> 0:04:58.880 true with frequencies electromagnetic frequencies. Uh, light is the same thing. 0:04:58.920 --> 0:05:01.039 All light is traveling at the same speed, but shorter 0:05:01.120 --> 0:05:03.479 wavelengths mean that you have a higher frequency, a higher 0:05:03.560 --> 0:05:07.240 number of waves passing through a certain point at a 0:05:07.240 --> 0:05:10.120 certain a certain amount of time. So what exactly was 0:05:10.160 --> 0:05:13.039 Doppler saying. Well, he was talking about how you could 0:05:13.080 --> 0:05:16.880 tell whether stars were moving toward or away from the 0:05:16.960 --> 0:05:20.279 viewer by the wavelength of light that you observed when 0:05:20.279 --> 0:05:23.839 looking at the star. A body moving away from the 0:05:23.920 --> 0:05:27.719 viewer would have elongated waves, almost as if it were 0:05:27.760 --> 0:05:31.600 stretching out the light behind it, So it would be 0:05:31.680 --> 0:05:35.000 a red shift because you'd be shifting closer towards the 0:05:35.040 --> 0:05:37.920 red side of the spectrum. Uh, that's the side of 0:05:37.920 --> 0:05:41.080 the spectrum that has the longer wavelengths. So something moving 0:05:41.120 --> 0:05:44.479 away from you with these elongated wavelengths would be red shifted. 0:05:44.640 --> 0:05:48.520 But if a star were moving toward you, then it 0:05:48.560 --> 0:05:51.880 would have compressed waves of light pushed ahead of it, 0:05:52.320 --> 0:05:55.520 so you would have the more of these wavelengths pushed 0:05:55.520 --> 0:05:58.680 towards you would be scrunched up. This would be blue 0:05:58.720 --> 0:06:02.200 shifted toward you. And we call this the Doppler effect, 0:06:02.240 --> 0:06:05.240 and it would become really important in radar, and it's 0:06:05.240 --> 0:06:08.080 also something that we can observe in our regular lives. 0:06:08.080 --> 0:06:10.960 We don't have to have a powerful telescope or a 0:06:11.360 --> 0:06:14.200 spectroscope to be able to do this because it works 0:06:14.200 --> 0:06:16.880 with lots of different kinds of waves, not just electro 0:06:16.960 --> 0:06:20.640 magnetic waves. It also works with sound waves. If you've 0:06:20.680 --> 0:06:24.000 ever heard a vehicle with a siren coming toward you, 0:06:24.000 --> 0:06:26.000 you might have noticed that it has a higher pitch 0:06:26.120 --> 0:06:29.680 sound as it approaches you, and then after it passes you, 0:06:29.760 --> 0:06:33.240 the pitch on the siren goes down as the vehicles 0:06:33.279 --> 0:06:36.479 moving away. This is the Doppler effect, in which the 0:06:36.520 --> 0:06:39.960 sound waves are compressed as the vehicle is coming towards you, 0:06:40.560 --> 0:06:44.480 and they are elongated as the vehicles moving away from you. 0:06:44.480 --> 0:06:46.960 And the vehicle we're staying perfectly still, you would hear 0:06:47.000 --> 0:06:51.279 a pitch somewhere in between those two other pitches. Also, 0:06:51.400 --> 0:06:53.520 if you're going faster than the speed of sound, if 0:06:53.600 --> 0:06:57.560 you your vehicles traveling faster than sound itself can travel, 0:06:57.800 --> 0:07:00.679 you would create what's called a sonic boom. But that's 0:07:00.800 --> 0:07:05.520 beside the point. So Smarty Pants Doppler observes this phenomena, 0:07:05.600 --> 0:07:08.440 which would allow future engineers a chance to determine if 0:07:08.480 --> 0:07:11.160 something was coming toward them or moving away from them 0:07:11.200 --> 0:07:14.560 based off of radar. It would take nearly a century 0:07:14.600 --> 0:07:17.840 for that to pay off in that way. However, The 0:07:17.880 --> 0:07:21.920 next person I need to talk about briefly is Heinrich Hurtz, 0:07:22.080 --> 0:07:26.040 who was a German physicist who conducted numerous experiments in 0:07:26.080 --> 0:07:30.560 the late nineteenth century around the eighteen eighties, and Hurts 0:07:30.600 --> 0:07:33.120 has a familiar name if you have talked a lot 0:07:33.120 --> 0:07:37.440 about frequencies. Hurts, in turn was building off of theoretical 0:07:37.480 --> 0:07:41.520 work that was done by a Scottish physicist named James 0:07:41.600 --> 0:07:45.280 Clerk Maxwell. So Maxwell had this idea. He had a 0:07:45.360 --> 0:07:48.840 theory that light and radio waves were all part of 0:07:48.880 --> 0:07:52.440 a larger spectrum of waves, so effectively this would be 0:07:52.440 --> 0:07:56.000 the electro magnetic spectrum, and that all of these waves 0:07:56.000 --> 0:07:59.800 would follow the same fundamental rules. Though the waves of 0:08:00.000 --> 0:08:03.160 cells would have a have very different wavelengths and frequencies, 0:08:03.480 --> 0:08:07.920 so the specific reactions will be a little different based 0:08:08.000 --> 0:08:10.640 upon the wavelengths and frequencies involved, but they would all 0:08:10.680 --> 0:08:14.480 follow the same basic set of rules. Maxwell's work suggested 0:08:14.520 --> 0:08:19.160 that radio waves could be reflected off of metallic surfaces 0:08:19.200 --> 0:08:21.880 just as light. Could you know if you have a mirror, 0:08:21.920 --> 0:08:24.240 you can bounce light around. Well, he said, well, if 0:08:24.240 --> 0:08:27.080 that's the case, if light behaves this way, and if 0:08:27.080 --> 0:08:31.120 electromagnetic radiation also behaves in that way, then you would 0:08:31.120 --> 0:08:35.160 expect electromagnetic radiation to also bounce off these surfaces. We 0:08:35.240 --> 0:08:37.840 can't see it, but it should still happen because they 0:08:37.840 --> 0:08:41.080 should still follow those rules. So Hurts set out to 0:08:41.200 --> 0:08:45.760 test that theory through experimentation, and he used radio waves 0:08:45.760 --> 0:08:48.960 that are frequency of about four hundred fifty five mega hurts, 0:08:49.000 --> 0:08:52.840 which meant the wavelengths were about sixty six centimeters in length. 0:08:53.320 --> 0:08:57.840 And he found in eight eight that Maxwell's theories held merit. 0:08:57.920 --> 0:09:01.800 They did a seemed to follow those fundamental rules. So 0:09:01.840 --> 0:09:03.960 in nineteen o four we then have to talk about 0:09:04.000 --> 0:09:08.120 a German engineer named Christian Hulsmeyer who applied for a 0:09:08.160 --> 0:09:11.840 patent for a quote an obstacle detector and ship navigation 0:09:11.880 --> 0:09:15.200 device end quote based off of this principle. This would 0:09:15.200 --> 0:09:18.280 have been a very early form of radar, but at 0:09:18.280 --> 0:09:21.400 the time no one was terribly interested in it, as 0:09:21.440 --> 0:09:24.800 there was no real practical use for it, yet not 0:09:24.920 --> 0:09:28.920 in nineteen o four. Uh. It would later become extremely practical, 0:09:28.960 --> 0:09:32.079 but no one could foresee that at the time. Skip 0:09:32.080 --> 0:09:36.160 ahead several decades after the development of radio, geniuses like 0:09:36.200 --> 0:09:39.640 Tesla and Marconi had advanced our understanding of radio waves 0:09:39.640 --> 0:09:42.640 and how to generate them, and by the nineteen thirties 0:09:43.000 --> 0:09:46.040 radio was widely deployed in many parts of the world. 0:09:46.400 --> 0:09:49.880 But engineers noticed something interesting. They saw that when you 0:09:49.960 --> 0:09:54.360 had transmitters posted across bodies of water, sometimes radio waves 0:09:54.400 --> 0:09:58.400 from one transmitter would bounce back to that source transmitter. 0:09:58.840 --> 0:10:03.080 It corresponded with ups passing between the two transmitters. The 0:10:03.120 --> 0:10:06.520 engineers and scientists observing this theorized that what must be 0:10:06.600 --> 0:10:09.440 happening is that some of those radio waves were going 0:10:09.480 --> 0:10:12.679 out over the water, colliding with a shop, and then 0:10:12.720 --> 0:10:15.720 bouncing back to the source. They were noticing the same 0:10:15.760 --> 0:10:19.840 effects that Hurts had tested decades earlier. But how would 0:10:19.840 --> 0:10:23.200 they make it a practical technology. Well, many different nations 0:10:23.240 --> 0:10:27.719 explored the possibility of using radio to detect large objects. 0:10:28.080 --> 0:10:31.079 In ninety two, in the United States, the United States 0:10:31.240 --> 0:10:35.800 Naval Research Laboratory in Washington, d C. Noted fluctuations in 0:10:35.960 --> 0:10:39.400 radio signal intensity between a transmitter on one side of 0:10:39.440 --> 0:10:42.440 the Potomac River and a receiver on the other side 0:10:42.440 --> 0:10:45.600 of the river. The fluctuations only occurred when a ship 0:10:45.679 --> 0:10:48.560 passed between the transmitter and the receiver on the river. 0:10:49.200 --> 0:10:52.160 But the upper levels of the Navy weren't interested in 0:10:52.200 --> 0:10:54.880 the technology as it stood, and it was only after 0:10:54.920 --> 0:10:58.280 the development of monostatic radar and which you used the 0:10:58.280 --> 0:11:02.160 exact same antenna as a transmitter and a receiver, that 0:11:02.240 --> 0:11:05.520 the Navy began to fund serious research and development. And 0:11:05.600 --> 0:11:09.720 that wouldn't happen until nineteen thirty nine. Enter Sir Robert 0:11:09.720 --> 0:11:15.400 Alexander Watson what a Scottish physicist. Now he is frequently 0:11:15.440 --> 0:11:18.480 credited as quote unquote the inventor of radar, but I 0:11:18.520 --> 0:11:21.360 need to say there were an awful lot of people, 0:11:21.520 --> 0:11:25.040 all working on similar ideas at the same time, so 0:11:25.120 --> 0:11:27.680 it's very difficult. In fact, it's impossible to say one 0:11:27.760 --> 0:11:31.280 person was the inventor of radar. One person tends to 0:11:31.320 --> 0:11:33.000 get the credit for it, but in fact this was 0:11:33.040 --> 0:11:38.560 happening all around the world simultaneously. So uh Watson what 0:11:38.840 --> 0:11:41.960 was born in eighteen ninety two. He attended the University 0:11:42.000 --> 0:11:44.600 of St Andrews, and he had begun his scientific career 0:11:45.000 --> 0:11:48.719 as sort of a meteorologist uh timpting to develop technology 0:11:48.760 --> 0:11:52.000 that could detect and track thunderstorms. He had observed this 0:11:52.040 --> 0:11:56.160 phenomenon of radio waves reflected off of things like ships, 0:11:56.480 --> 0:11:58.920 and wrote a memorandum to the British government in nineteen 0:11:59.000 --> 0:12:02.360 thirty five. It was his opinion that given a radio 0:12:02.440 --> 0:12:06.320 transmitter and a receiver, with sufficient power and radio waves 0:12:06.320 --> 0:12:10.679 in the proper frequency, you could potentially detect incoming aircraft, 0:12:10.960 --> 0:12:13.480 and such a device would be an incredibly powerful tool, 0:12:13.840 --> 0:12:16.679 not just in peace time, but also in war, and 0:12:16.880 --> 0:12:20.480 tensions were mounting in Europe in nineteen thirty five, so 0:12:20.520 --> 0:12:23.920 this was a high priority. Being able to detect an 0:12:23.960 --> 0:12:27.719 incoming air attack could save thousands of lives. And I'll 0:12:27.760 --> 0:12:30.000 talk more about what he did in just a second, 0:12:30.080 --> 0:12:32.920 but first let's take a quick break to thank our 0:12:33.000 --> 0:12:44.200 sponsor Watson what began to experiment with a design for 0:12:44.280 --> 0:12:48.120 detecting aircraft in ninety five. He developed a transmitter and 0:12:48.160 --> 0:12:51.480 a receiver and was using it to locate any sort 0:12:51.520 --> 0:12:54.520 of aircraft from a distance of about ninety miles or 0:12:56.600 --> 0:12:59.360 His work inspired the British government to fund a project 0:12:59.480 --> 0:13:03.240 called chain Home, which was a system of radars that 0:13:03.360 --> 0:13:07.959 operated on frequencies ranging from twenty two to fifty mega hurts. Now, 0:13:08.040 --> 0:13:10.960 visible light is in the four dred thirty to seven 0:13:11.400 --> 0:13:15.839 seventy terror hurts range. So how long were the wavelengths 0:13:15.880 --> 0:13:19.240 that Watson What was working with? While they ranged from 0:13:19.280 --> 0:13:23.080 about six meters or nineteen point seven ft to thirteen 0:13:23.160 --> 0:13:26.200 point six meters or forty four point seven feet, So 0:13:26.559 --> 0:13:29.600 these were waves that were on many orders of magnitude 0:13:29.640 --> 0:13:33.960 longer than the nanometer scale wavelengths of visible light. They 0:13:33.960 --> 0:13:38.480 were huge in comparison. Watson What said that the use 0:13:38.520 --> 0:13:41.719 of such long wavelengths followed a philosophy he called the 0:13:41.800 --> 0:13:46.160 cult of the imperfect. He defined this as quote, give 0:13:46.200 --> 0:13:49.480 them the third best to go on with, the second 0:13:49.480 --> 0:13:53.400 best comes too late, the best never comes end quote. 0:13:53.559 --> 0:13:56.280 So in other words, he says, yeah, we could have 0:13:56.320 --> 0:14:00.840 tried to generate smaller wavelengths, which would have solved a 0:14:00.880 --> 0:14:02.720 lot of problems. One, it would have given you better 0:14:02.720 --> 0:14:06.800 resolution to It would have cut down on noise and interference, 0:14:07.360 --> 0:14:10.360 but it also would have taken longer to develop. If 0:14:10.360 --> 0:14:12.800 you want something that you can deploy, you go with 0:14:12.880 --> 0:14:15.839 an easier solution, you have to set that goal lower 0:14:15.880 --> 0:14:18.320 than what you want in order to deliver on time 0:14:18.480 --> 0:14:23.080 if timeliness is more important than resolution. For example, the 0:14:23.200 --> 0:14:26.920 chain home system went online in September night as a 0:14:27.000 --> 0:14:31.040 twenty four hour detection system. The system helped England detect 0:14:31.160 --> 0:14:34.840 incoming bombing runs from the Germans and melt a limited 0:14:34.880 --> 0:14:38.480 air defense with their own capabilities, and without that system, 0:14:38.520 --> 0:14:41.080 the damage and losses from German attacks would have been 0:14:41.160 --> 0:14:44.400 much greater than what they were. Other nations such as 0:14:44.440 --> 0:14:48.280 the Soviet Union, Germany, Japan, the United States, and many 0:14:48.320 --> 0:14:52.280 others were all working on similar radar technologies around this time, 0:14:52.600 --> 0:14:56.840 primarily for use during the war. German systems operated at 0:14:56.880 --> 0:15:00.760 three five mega hurts and five hundred sixty egga hurts, 0:15:00.760 --> 0:15:04.520 which gave them superior resolution and accuracy, and it also 0:15:04.520 --> 0:15:07.200 meant German systems had less noise to deal with. So 0:15:07.320 --> 0:15:11.479 why is all this Well, remember that higher frequencies correspond 0:15:11.560 --> 0:15:15.760 with shorter wavelengths. Shorter wavelengths are more narrow and thus 0:15:15.800 --> 0:15:18.360 you can get a better picture of where something is 0:15:18.480 --> 0:15:22.720 when you're using them. So remember that radar is essentially echolocation. 0:15:23.040 --> 0:15:25.840 If you send out a very long wavelength and the 0:15:26.000 --> 0:15:28.920 very long wavelength returns to you. You know the wavelength 0:15:29.000 --> 0:15:31.640 encountered something that it reflected off of, but it's harder 0:15:31.680 --> 0:15:34.400 to figure out exactly where that object is because the 0:15:34.480 --> 0:15:38.320 wavelength is literally covering more space. You can tell how 0:15:38.400 --> 0:15:40.880 far away the object is, and the way you do 0:15:40.920 --> 0:15:42.680 that is you measure the amount of time it took 0:15:42.720 --> 0:15:46.040 the radio wave to leave the transmitter and then return 0:15:46.120 --> 0:15:49.080 to the receiver. You know that radio waves are traveling 0:15:49.080 --> 0:15:51.640 at the speed of light, so you take the amount 0:15:51.680 --> 0:15:53.280 of time it took for the radio wave to go 0:15:53.400 --> 0:15:56.560 out and back. Then you take half of that number, 0:15:57.160 --> 0:15:59.400 and you multiply at times the speed of light, and 0:15:59.440 --> 0:16:02.560 you get the sense of the object. You have the 0:16:02.640 --> 0:16:05.880 number because otherwise you have the round trip. Right, that's 0:16:05.920 --> 0:16:10.760 just the full distance between you and the target object doubled, 0:16:10.840 --> 0:16:13.200 so you have to take one half of that. Further, 0:16:13.680 --> 0:16:16.800 by looking for any changes in wavelength, you can determine 0:16:16.840 --> 0:16:20.000 if the object is moving towards you or away from you. 0:16:20.360 --> 0:16:23.960 This again is that Doppler effect. If the returning wavelengths 0:16:24.000 --> 0:16:26.640 are the same as the ones you sent out, the 0:16:26.680 --> 0:16:30.480 object you detected is sitting still relative to your position. 0:16:30.920 --> 0:16:34.000 If the wavelengths are shorter than the object is moving 0:16:34.040 --> 0:16:36.760 toward you, And if the wavelengths are longer than what 0:16:36.840 --> 0:16:39.360 you sent out, then the object is moving away from you. 0:16:39.920 --> 0:16:42.920 But if the wavelengths are already pretty long, you don't 0:16:42.960 --> 0:16:45.560 have a lot of accuracy when you're looking at the feedback. 0:16:45.640 --> 0:16:48.480 A narrower beam will give you a better idea of 0:16:48.520 --> 0:16:51.520 exactly where in the sky the object is. This is 0:16:51.560 --> 0:16:55.360 clearly more helpful in both military and peacetime operations. So 0:16:55.480 --> 0:16:58.320 Germany was way ahead of everyone else in terms of 0:16:58.400 --> 0:17:01.840 radar when World World War two began. The country had 0:17:01.880 --> 0:17:05.439 deployed radar on ships and on ground defense stations. They 0:17:05.440 --> 0:17:08.760 were using shorter wavelengths than just about anybody else. The 0:17:08.840 --> 0:17:13.080 country continued to develop the technology until about nineteen forty. 0:17:13.600 --> 0:17:17.040 So why did they stop Well, German leaders were confident 0:17:17.080 --> 0:17:19.400 that the war would soon be over and Germany would 0:17:19.400 --> 0:17:23.679 be victorious, so they stopped work on radar to concentrate 0:17:23.720 --> 0:17:26.919 on the war effort. Meanwhile, the UK and the US 0:17:27.000 --> 0:17:31.400 were stepping up their efforts accelerating the evolution of the technology. 0:17:31.440 --> 0:17:33.520 By the time Germany determined that the end of the 0:17:33.560 --> 0:17:36.320 war was still years away, it was too late the 0:17:36.359 --> 0:17:40.000 country was hopelessly left behind in terms of radar tech. 0:17:40.800 --> 0:17:42.600 And now we touch on the part of the story 0:17:42.640 --> 0:17:45.359 that I've mentioned in recent episodes about Alfred Loomis and 0:17:45.400 --> 0:17:50.040 the Loran system. Scientists at the University of Birmingham developed 0:17:50.080 --> 0:17:55.000 a cavity magnatron oscillator to produce waves in the microwave frequency, 0:17:55.040 --> 0:17:58.800 and I'm talking about Birmingham in the UK hunt Alabama. 0:17:59.160 --> 0:18:03.320 These devices used electric and magnetic fields to stimulate microwave 0:18:03.359 --> 0:18:07.880 generation and chambers called cavities within a vacuum tube like device. 0:18:08.600 --> 0:18:11.760 Microwaves can have a wavelength of between one meter all 0:18:11.760 --> 0:18:14.680 the way down to one millimeter, and that gives them 0:18:14.680 --> 0:18:19.000 frequencies of between three hundred megahurts to three hundred giga hurts. 0:18:19.359 --> 0:18:22.280 The scientists at the University of Birmingham had created a 0:18:22.359 --> 0:18:26.240 cavity magnetron capable of producing microwaves that were about ten 0:18:26.320 --> 0:18:29.840 centimeters in wavelength, meaning they were very close to three 0:18:29.840 --> 0:18:33.160 giga hurts and frequency. If used with radar, this would 0:18:33.160 --> 0:18:37.600 make a system capable of unprecedented accuracy and resolution. But 0:18:37.680 --> 0:18:40.840 the scientists needed help, and so they traveled to America 0:18:41.200 --> 0:18:44.040 to meet with experts at M i T Now to 0:18:44.119 --> 0:18:48.600 avoid suspicion, Taffy Bowen, a British scientist, traveled to the 0:18:48.720 --> 0:18:52.720 United States under the pretense of going on holiday. He 0:18:52.800 --> 0:18:55.560 made the trip aboard a cruise ship called the Duchess 0:18:55.680 --> 0:18:58.520 of Richmond, which is not a bad way to deliver 0:18:58.600 --> 0:19:03.400 top secret technology to allies across the ocean. The scientists 0:19:03.520 --> 0:19:07.680 collaborated together and they created the newly formed rad Lab 0:19:07.840 --> 0:19:11.679 at m I T to develop microwave radar technology. The 0:19:11.800 --> 0:19:15.359 United States Navy was the actual entity to name the 0:19:15.400 --> 0:19:19.040 technology radar, and originally that was an acronym that stood 0:19:19.040 --> 0:19:22.600 for radio detection and ranging. These days, it's just a 0:19:22.600 --> 0:19:24.840 regular noun. We just call it radar. You don't have 0:19:24.880 --> 0:19:27.960 to capitalize it either. One other thing to note about 0:19:28.000 --> 0:19:33.280 this time. On December seven, ninety one, and Army radar 0:19:33.359 --> 0:19:36.240 site picked up a signal that indicated more than a 0:19:36.400 --> 0:19:40.960 hundred aircraft were on approach to Hawaii. George Elliott, one 0:19:41.000 --> 0:19:44.240 of the two operators of the radar site, passed this 0:19:44.320 --> 0:19:46.760 information up the chain of command, but no one acted 0:19:46.840 --> 0:19:50.200 upon it. According to Elliott, he and his co operator, 0:19:50.280 --> 0:19:53.000 Joe Lockard were to run the station only between the 0:19:53.040 --> 0:19:56.200 hours of four and seven a m. But Elliott wanted 0:19:56.200 --> 0:19:58.439 to get in a bit more experience. He was brand 0:19:58.440 --> 0:20:01.119 new to operating radars, so he wanted to practice for 0:20:01.160 --> 0:20:03.280 a while, so he kept the system running for a 0:20:03.280 --> 0:20:05.960 few minutes after seven am, and it was seven oh 0:20:06.000 --> 0:20:08.200 two when he saw the large reading. It was actually 0:20:08.359 --> 0:20:11.280 larger than any other reading they had previously seen at 0:20:11.320 --> 0:20:14.240 that station. After calling in the report, he was told 0:20:14.560 --> 0:20:17.080 that it was likely a group of US bombers heading 0:20:17.080 --> 0:20:21.640 towards San Francisco. But then the Japanese forces unleashed a 0:20:21.680 --> 0:20:25.359 devastating attack on Pearl Harbor, which would pull the United 0:20:25.359 --> 0:20:30.080 States into World War Two. The microwave radar technology began 0:20:30.119 --> 0:20:33.240 to get a rapid deployment in the early nineteen forties 0:20:33.280 --> 0:20:35.480 as part of a top secret effort to gain an 0:20:35.520 --> 0:20:39.200 advantage in the war. The Axis forces had learned how 0:20:39.200 --> 0:20:43.480 to jam earlier radar systems like the SCR TO six eight, 0:20:43.800 --> 0:20:47.040 which used longer radio waves, and that was from the 0:20:47.119 --> 0:20:50.600 United States and it operated on a much lower frequency 0:20:50.600 --> 0:20:53.399 than the microwave radar stations they were, so the Germans 0:20:53.400 --> 0:20:56.320 were unprepared for the high precision of the new microwave 0:20:56.359 --> 0:20:59.640 systems that were represented in the s c R five 0:20:59.720 --> 0:21:03.600 eight four radar designation. The new radar had a parabolic 0:21:03.720 --> 0:21:07.320 reflector antenna that measured two meters or about six point 0:21:07.359 --> 0:21:10.080 six feet in diameter, and it was first used in 0:21:10.160 --> 0:21:13.480 combat in nineteen forty four in Italy to great effect. 0:21:13.760 --> 0:21:17.080 Many different versions of radar were developed and deployed during 0:21:17.119 --> 0:21:20.720 the war, including radar systems aboard aircraft and those on 0:21:20.880 --> 0:21:25.800 naval vessels. On May nine, a German warship called the 0:21:25.880 --> 0:21:29.320 Bismarck sunk a British ship called the h MS Hood, 0:21:29.640 --> 0:21:33.080 but a British aircraft carrier called the Arc Royal used 0:21:33.160 --> 0:21:36.679 shipborn radar to detect and track the Bismarck, and that 0:21:36.760 --> 0:21:40.840 allowed Allied forces to converge and attack the ship, ultimately 0:21:40.960 --> 0:21:45.240 sinking it. After World War Two ended, Winston Churchill would 0:21:45.280 --> 0:21:48.000 say that while the atomic bomb may have ended the war, 0:21:48.680 --> 0:21:52.240 radar was the technology that won the war. Now I 0:21:52.240 --> 0:21:54.760 have a little bit more to say about radar, but 0:21:54.840 --> 0:21:57.640 first let's take another quick break to thank our sponsor. 0:22:05.119 --> 0:22:07.800 Towards the end of World War Two, the UK and 0:22:07.840 --> 0:22:10.760 the US had both worked with radar to aid with 0:22:10.960 --> 0:22:15.520 landing aircraft to guide them into landing strips safely. And 0:22:15.600 --> 0:22:19.399 that use of radar quickly expanded to civil oberations, and 0:22:19.440 --> 0:22:22.000 that would become the basis of air traffic control. And 0:22:22.040 --> 0:22:24.959 at first they would use this just for the purposes 0:22:25.080 --> 0:22:27.919 of guiding aircraft to land at landing strips or to 0:22:27.960 --> 0:22:32.120 take off, and then ultimately to become more of a 0:22:32.160 --> 0:22:35.480 holistic air traffic control system that could be handed off 0:22:35.520 --> 0:22:40.159 from one control tower to another to maintain contact with 0:22:40.280 --> 0:22:45.280 pilots as they traveled across vast distances. Advances in radar 0:22:45.320 --> 0:22:49.800 also helped fuel more study in radio astronomy. Radio astronomy 0:22:49.920 --> 0:22:53.639 uses large arrays of radio antenna to detect extra terrestrial 0:22:53.880 --> 0:22:57.240 radio signals, And by that I don't necessarily mean we're 0:22:57.240 --> 0:23:00.600 listening to the equivalent of alien television rerun ones. In fact, 0:23:00.640 --> 0:23:03.440 I don't mean that at all, because lots of stuff 0:23:03.520 --> 0:23:07.240 emits radio waves. So we're talking about studying signals from 0:23:07.320 --> 0:23:13.240 various celestial phenomenas just stars, galaxies, quasars, pulsars, and more. 0:23:13.680 --> 0:23:16.040 Another use of radar that grew out of military use 0:23:16.160 --> 0:23:20.880 was for meteorology. During the war, radar operators noted that 0:23:20.920 --> 0:23:25.160 many times they detected excess noise or clutter when they 0:23:25.280 --> 0:23:30.400 directed radar transmissions towards weather elements like precipitation. After the war, 0:23:30.720 --> 0:23:35.080 engineers and scientists began to adapt radar to track storms, Specifically, 0:23:35.440 --> 0:23:40.160 special radar systems that could detect precipitation, including how intense 0:23:40.240 --> 0:23:44.240 that precipitation was, began to help meteorologists track weather patterns 0:23:44.440 --> 0:23:47.440 and adjust forecasts. So you may have heard of Doppler 0:23:47.560 --> 0:23:50.840 radar on your local weather forecast. That's what's talking about. 0:23:50.840 --> 0:23:54.719 Their using radar to detect things like precipitation and the 0:23:54.760 --> 0:23:59.640 movement of these thunderstorms and weather patterns. Other advances include 0:23:59.720 --> 0:24:03.239