1 00:00:04,480 --> 00:00:12,399 Speaker 1: Welcome to Tech Stuff, a production from iHeartRadio. Hey there, 2 00:00:12,440 --> 00:00:16,120 Speaker 1: and welcome to tech Stuff. I'm your host, Jonathan Strickland. 3 00:00:16,160 --> 00:00:19,200 Speaker 1: I'm an executive producer with iHeart Podcasts and how the 4 00:00:19,239 --> 00:00:23,720 Speaker 1: tech are you so, y'all. I love to travel. I 5 00:00:23,760 --> 00:00:28,360 Speaker 1: love to visit new places or revisit ones after I've 6 00:00:28,400 --> 00:00:31,240 Speaker 1: been away for a long time. I even don't really 7 00:00:31,320 --> 00:00:35,160 Speaker 1: mind the journey part of travel, which can often be 8 00:00:35,320 --> 00:00:38,520 Speaker 1: you know, stressful, in a hassle if things aren't going well. 9 00:00:38,880 --> 00:00:41,400 Speaker 1: One thing that does give me a huge amount of 10 00:00:41,400 --> 00:00:46,240 Speaker 1: anxiety if I'm traveling is just getting lost or even 11 00:00:46,280 --> 00:00:48,880 Speaker 1: the thought of getting lost. I do not do very 12 00:00:48,880 --> 00:00:51,159 Speaker 1: well with that. There's some part of my brain that 13 00:00:51,200 --> 00:00:53,840 Speaker 1: mistakenly believes that as long as I know where I am, 14 00:00:54,560 --> 00:00:58,640 Speaker 1: nothing can go too wrong. And boy I wish that 15 00:00:58,720 --> 00:01:02,600 Speaker 1: were true, but but yeah, whatever, I just need my 16 00:01:02,720 --> 00:01:06,360 Speaker 1: brain to let me function properly when I'm out on holidays. 17 00:01:06,400 --> 00:01:11,280 Speaker 1: So I remember traveling on my honeymoon to London. At 18 00:01:11,280 --> 00:01:14,600 Speaker 1: that point, I had never been outside the United States before. 19 00:01:14,720 --> 00:01:18,040 Speaker 1: This was my first trip outside the country, and I 20 00:01:18,080 --> 00:01:20,800 Speaker 1: was going to a city that I had read about extensively. 21 00:01:21,400 --> 00:01:24,720 Speaker 1: I knew a lot about London. My major in college 22 00:01:24,800 --> 00:01:27,959 Speaker 1: was in English literature, but it was with a focus 23 00:01:28,000 --> 00:01:31,200 Speaker 1: on medieval studies, so things had changed slightly by the 24 00:01:31,240 --> 00:01:33,760 Speaker 1: time I got there, and reading about a city is 25 00:01:33,920 --> 00:01:38,600 Speaker 1: very different from actually walking around one. Also, my honeymoon 26 00:01:38,640 --> 00:01:41,959 Speaker 1: was in the nineteen nineties because I'm old, and that 27 00:01:42,080 --> 00:01:46,480 Speaker 1: meant I was a decade out from the era of smartphones, 28 00:01:46,800 --> 00:01:49,440 Speaker 1: so I didn't have a handy mobile device to tell 29 00:01:49,440 --> 00:01:52,080 Speaker 1: me where I was as I wandered around the city. 30 00:01:52,280 --> 00:01:55,480 Speaker 1: Even if smartphones had been around back then, I wouldn't 31 00:01:55,520 --> 00:01:58,800 Speaker 1: have been able to rely on map apps on the 32 00:01:58,840 --> 00:02:03,960 Speaker 1: smartphone because of something called selective availability. More on that 33 00:02:04,560 --> 00:02:07,520 Speaker 1: in a bit, but at any rate, I had to 34 00:02:07,560 --> 00:02:11,800 Speaker 1: rely on physical maps to get around and hope that 35 00:02:11,800 --> 00:02:14,600 Speaker 1: I didn't mess it up too badly. Yeah, it's like 36 00:02:14,639 --> 00:02:17,760 Speaker 1: the Stone Age right. Well, these days, as long as 37 00:02:17,760 --> 00:02:20,680 Speaker 1: I have my smartphone with me and I'm not buried 38 00:02:20,760 --> 00:02:23,840 Speaker 1: under a mountain or something, I feel fairly confident I'm 39 00:02:23,880 --> 00:02:26,320 Speaker 1: not going to get lost. If I'm going somewhere that 40 00:02:26,320 --> 00:02:30,120 Speaker 1: has limited connectivity, like limited view of the sky, then 41 00:02:30,240 --> 00:02:33,720 Speaker 1: my anxiety starts to creep in again. But usually I'm okay, 42 00:02:34,160 --> 00:02:38,040 Speaker 1: and that's thanks to the Global Positioning System or GPS. 43 00:02:38,360 --> 00:02:41,720 Speaker 1: So today we're going to learn about GPS, what makes 44 00:02:41,720 --> 00:02:44,600 Speaker 1: it work, how the technology has to take into account, 45 00:02:44,639 --> 00:02:48,679 Speaker 1: Einstein's theories of relativity and more. And a huge thank 46 00:02:48,720 --> 00:02:51,839 Speaker 1: to JP Morgan, Chase Bank, and the United Explorer Card 47 00:02:51,919 --> 00:02:55,400 Speaker 1: for sponsoring this episode. We'll hear more about them later too. 48 00:02:55,960 --> 00:03:00,000 Speaker 1: So GPS, well, that story begins back in the nineteen 49 00:03:00,000 --> 00:03:03,280 Speaker 1: teen fifties when the United States and the then Soviet 50 00:03:03,400 --> 00:03:06,760 Speaker 1: Union were locked in a Cold war, and that cold 51 00:03:06,760 --> 00:03:09,960 Speaker 1: war manifested in many different ways, including an effort to 52 00:03:10,040 --> 00:03:13,080 Speaker 1: launch vehicles into space. For one thing, if you could 53 00:03:13,160 --> 00:03:17,320 Speaker 1: launch a rocket into orbit, then you could show your 54 00:03:17,320 --> 00:03:20,760 Speaker 1: technological superiority over your opponent and say, look how much 55 00:03:20,800 --> 00:03:23,959 Speaker 1: further advanced we are compared to you. But you could 56 00:03:24,000 --> 00:03:26,480 Speaker 1: also send the message of hey, if I can send 57 00:03:26,520 --> 00:03:29,200 Speaker 1: a rocket to space, I could send a rocket to 58 00:03:29,280 --> 00:03:31,960 Speaker 1: your front door, all the way from across the world, 59 00:03:32,200 --> 00:03:34,440 Speaker 1: and it could be carrying a heck of a boom boom. 60 00:03:34,960 --> 00:03:39,360 Speaker 1: Now this gram message underpinned what would become the space race. 61 00:03:39,400 --> 00:03:42,520 Speaker 1: But the space race also meant that brilliant engineers and 62 00:03:42,560 --> 00:03:46,680 Speaker 1: scientists would actually get the resources they needed to advance 63 00:03:46,720 --> 00:03:50,880 Speaker 1: technology by incredible leaps and bounds over the following decades. 64 00:03:51,200 --> 00:03:53,920 Speaker 1: So you got to take the good with the bad, right. 65 00:03:54,360 --> 00:03:59,480 Speaker 1: The good part is you suddenly had actual financial support 66 00:03:59,800 --> 00:04:05,920 Speaker 1: for or incredibly important scientific and engineering work. The bad is, well, 67 00:04:06,040 --> 00:04:10,480 Speaker 1: it was all done in service of this perceived rivalry 68 00:04:10,760 --> 00:04:13,920 Speaker 1: with this massive country on the other side of the globe. 69 00:04:14,080 --> 00:04:18,279 Speaker 1: On October fourth, nineteen fifty seven, at approximately seven thirty pm, 70 00:04:18,360 --> 00:04:24,040 Speaker 1: the USSR launched the first man made satellite into orbit, Sputnik. 71 00:04:24,480 --> 00:04:27,560 Speaker 1: Non past episodes, I have referred to the satellite as 72 00:04:27,640 --> 00:04:31,520 Speaker 1: the ball that went beep. That's not exactly inaccurate. The 73 00:04:31,560 --> 00:04:34,400 Speaker 1: satellite was spherical in shape. It did have these long 74 00:04:34,440 --> 00:04:36,680 Speaker 1: antenna extending out the back of it, so it kind 75 00:04:36,680 --> 00:04:39,719 Speaker 1: of looks like a comet, like a silver comet. But 76 00:04:39,800 --> 00:04:43,680 Speaker 1: the antenna transmitted short radio pulses, and these pulses could 77 00:04:43,720 --> 00:04:47,440 Speaker 1: be picked up very easily by ground based audio receivers, 78 00:04:47,480 --> 00:04:52,360 Speaker 1: including radio sets operated by amateurs, just an amateur radio set. 79 00:04:52,600 --> 00:04:56,159 Speaker 1: This meant that Sputnik's existence couldn't be kept a secret 80 00:04:56,360 --> 00:04:59,520 Speaker 1: because if you or someone you knew operated a radio, 81 00:05:00,040 --> 00:05:03,320 Speaker 1: you could learn about the thing. And in the United States, 82 00:05:03,320 --> 00:05:07,280 Speaker 1: it prompted no small amount of anxiety. Americans believed their 83 00:05:07,320 --> 00:05:10,400 Speaker 1: country was well ahead of the Soviet Union, at least 84 00:05:10,400 --> 00:05:14,160 Speaker 1: on a technological basis. But here they could see that 85 00:05:14,200 --> 00:05:17,760 Speaker 1: their adversary had launched stuff into space and did it 86 00:05:17,839 --> 00:05:21,120 Speaker 1: before the US could do it. That really kicked things 87 00:05:21,160 --> 00:05:23,680 Speaker 1: into gear here in the United States. But I would 88 00:05:23,760 --> 00:05:27,200 Speaker 1: argue that Sputnik would ultimately plant a seed that would 89 00:05:27,240 --> 00:05:30,720 Speaker 1: blossom into GPS further down the line, because here you 90 00:05:30,760 --> 00:05:34,840 Speaker 1: had a satellite sending regular radio signals to Earth, and 91 00:05:35,000 --> 00:05:38,240 Speaker 1: those signals were pretty primitive. Essentially, the satellite was signaling 92 00:05:38,279 --> 00:05:41,840 Speaker 1: that it was within range overhead, along with basic information 93 00:05:41,880 --> 00:05:45,720 Speaker 1: about stuff like air pressure and temperature indicated by the 94 00:05:45,800 --> 00:05:48,440 Speaker 1: length of the radio pulses. Like the pulses didn't give 95 00:05:48,960 --> 00:05:52,400 Speaker 1: data the way Wi Fi does. Literally, you would measure 96 00:05:52,440 --> 00:05:55,279 Speaker 1: how long the pulse lasted and that would tell you, oh, 97 00:05:55,360 --> 00:05:59,960 Speaker 1: the temperature is whatever, if you happen to have the chart. 98 00:06:00,080 --> 00:06:05,040 Speaker 1: Two scientists were able to adfer other information, however, from 99 00:06:05,279 --> 00:06:09,200 Speaker 1: this signal, such as how the propagation of radio signals 100 00:06:09,200 --> 00:06:12,880 Speaker 1: interacted in the upper atmosphere like the ionosphere, and it 101 00:06:13,000 --> 00:06:16,080 Speaker 1: hinted that there could be other uses for as satellite 102 00:06:16,400 --> 00:06:20,640 Speaker 1: beaming information down to Earth. Also, those signals were subject 103 00:06:20,680 --> 00:06:23,400 Speaker 1: to what we call the Doppler effect. It's named after 104 00:06:23,640 --> 00:06:27,600 Speaker 1: Christian Doppler effect. No, I'm sorry, it's just Christian Doppler. 105 00:06:27,839 --> 00:06:31,480 Speaker 1: He first observed this effect back in eighteen forty two. 106 00:06:32,080 --> 00:06:35,160 Speaker 1: And this is how the frequency of a wave changes 107 00:06:35,279 --> 00:06:39,360 Speaker 1: relative to an independent observer if the thing that's emitting 108 00:06:39,400 --> 00:06:43,800 Speaker 1: the wave is moving toward or away from that observer. 109 00:06:44,400 --> 00:06:46,920 Speaker 1: Which was a clumsy explanation, Let's just take an example 110 00:06:46,920 --> 00:06:50,000 Speaker 1: because that makes it way more clear. So let's say 111 00:06:50,480 --> 00:06:53,520 Speaker 1: you're just walking down the street. You're on a sidewalk, 112 00:06:53,920 --> 00:06:56,159 Speaker 1: and say one hundred feet or so in front of you, 113 00:06:56,440 --> 00:06:59,480 Speaker 1: there's an emergency vehicle and it's parked. It's not currently 114 00:06:59,560 --> 00:07:02,880 Speaker 1: driving anywhere, but it is running its siren. The sound 115 00:07:02,920 --> 00:07:06,279 Speaker 1: of that siren is going to remain consistent relative to you, right, 116 00:07:06,839 --> 00:07:10,800 Speaker 1: it may increase and decrease in pitch because the nature 117 00:07:10,840 --> 00:07:14,360 Speaker 1: of the siren, but it's going to keep doing that 118 00:07:14,440 --> 00:07:18,120 Speaker 1: pattern over and over again. But now let's say that 119 00:07:18,360 --> 00:07:21,360 Speaker 1: it's an emergency vehicle that's rushing off away from you. 120 00:07:21,400 --> 00:07:24,120 Speaker 1: It's driving off. You'll notice the pitch of the siren 121 00:07:24,160 --> 00:07:26,720 Speaker 1: will start to go lower. The frequency of the sound 122 00:07:26,720 --> 00:07:30,680 Speaker 1: wave decreases as the vehicle accelerates away from you, or 123 00:07:31,120 --> 00:07:33,840 Speaker 1: let's say the vehicle is driving towards you, the pitch 124 00:07:33,840 --> 00:07:37,320 Speaker 1: of the siren will go up as the frequency increases. 125 00:07:37,720 --> 00:07:39,480 Speaker 1: You can kind of think of it like this. An 126 00:07:39,560 --> 00:07:44,480 Speaker 1: approaching object emitting a wave is effectively pushing or compressing 127 00:07:44,520 --> 00:07:47,600 Speaker 1: that wave as it moves closer to you. An object 128 00:07:47,680 --> 00:07:50,600 Speaker 1: moving away from you is stretching out the wave it's 129 00:07:50,600 --> 00:07:53,960 Speaker 1: emitting as it moves away from you. That is the 130 00:07:54,040 --> 00:07:58,960 Speaker 1: Doppler effect. Scientists at the Applied Physics Laboratory or APL, 131 00:07:59,080 --> 00:08:03,080 Speaker 1: at Johns Hopkins University noticed that the Doppler effect was 132 00:08:03,280 --> 00:08:07,720 Speaker 1: also applicable to Sputnik's radio waves. The satellite's radio pulses 133 00:08:07,760 --> 00:08:11,440 Speaker 1: were compressed as Sputnik would approach, and then they would 134 00:08:11,440 --> 00:08:14,600 Speaker 1: stretch out as the satellite would move away from their 135 00:08:14,680 --> 00:08:18,280 Speaker 1: point of observation, and this meant that just by listening 136 00:08:18,320 --> 00:08:22,400 Speaker 1: to the pulses, the scientists could track Sputnik's movements. They 137 00:08:22,400 --> 00:08:24,800 Speaker 1: didn't need to have eyes on the satellite to track it. 138 00:08:24,920 --> 00:08:27,400 Speaker 1: They could just follow the pulses and observe the Doppler 139 00:08:27,400 --> 00:08:31,360 Speaker 1: effect in order to know generally where it was and 140 00:08:31,400 --> 00:08:34,240 Speaker 1: when it was heading away, but very generally, like they 141 00:08:34,240 --> 00:08:37,880 Speaker 1: couldn't give you a pinpointed location. However, this was another 142 00:08:37,920 --> 00:08:41,400 Speaker 1: important seed for what would become GPS, because it would 143 00:08:41,440 --> 00:08:45,160 Speaker 1: lead to the hypothesis that a satellite could send signals 144 00:08:45,200 --> 00:08:48,080 Speaker 1: to a receiver on Earth, and if that receiver quote 145 00:08:48,120 --> 00:08:52,000 Speaker 1: unquote knew how far away the satellite was from the receiver, 146 00:08:52,440 --> 00:08:56,240 Speaker 1: you could determine the location of that receiver on Earth. 147 00:08:56,679 --> 00:08:58,240 Speaker 1: You would need to be able to get signals from 148 00:08:58,240 --> 00:09:00,679 Speaker 1: more than one satellite, however, to do that, otherwise, you 149 00:09:00,679 --> 00:09:02,920 Speaker 1: would really just know how far away you were from 150 00:09:03,000 --> 00:09:06,200 Speaker 1: one satellite. But that's not really useful information because it 151 00:09:06,200 --> 00:09:08,719 Speaker 1: doesn't narrow stuff down enough, or to put it in 152 00:09:08,760 --> 00:09:12,720 Speaker 1: another way, let's say, let's take this to two dimensions. 153 00:09:12,720 --> 00:09:15,200 Speaker 1: So let's talk about a map. Let's say you've got 154 00:09:15,240 --> 00:09:18,200 Speaker 1: a map of North Georgia, Okay, because that's where I live. 155 00:09:18,600 --> 00:09:22,520 Speaker 1: And I could say, hey, I live twenty miles away 156 00:09:22,559 --> 00:09:25,480 Speaker 1: from my parents. And let's say you happen to know 157 00:09:25,520 --> 00:09:28,320 Speaker 1: where I live. Not that I'm gonna dox myself, but 158 00:09:28,400 --> 00:09:30,200 Speaker 1: let's say you know where I live, so you can 159 00:09:30,240 --> 00:09:33,360 Speaker 1: take that point on the map you could draw out 160 00:09:33,400 --> 00:09:35,960 Speaker 1: a line that's twenty miles out and then create a 161 00:09:36,000 --> 00:09:40,560 Speaker 1: circle with a radius of twenty miles but without more information, 162 00:09:40,679 --> 00:09:43,760 Speaker 1: that could mean they could be anywhere along that circumference 163 00:09:43,760 --> 00:09:46,440 Speaker 1: of the circle right in a radius of twenty miles 164 00:09:46,480 --> 00:09:48,720 Speaker 1: from me. They could be east or west, or north 165 00:09:48,800 --> 00:09:51,440 Speaker 1: or south, or any point in between, as long as 166 00:09:51,480 --> 00:09:54,440 Speaker 1: it was twenty miles out from my location. We'll come 167 00:09:54,480 --> 00:09:58,000 Speaker 1: back to this analogy in a little bit. Let's get 168 00:09:58,040 --> 00:10:00,640 Speaker 1: back to the Doppler effect. It could all be used 169 00:10:00,640 --> 00:10:04,440 Speaker 1: to get a more accurate location. If you know where 170 00:10:04,480 --> 00:10:07,600 Speaker 1: the satellite is as you receive signals, you can use 171 00:10:07,640 --> 00:10:10,560 Speaker 1: a series of pulses from that satellite to determine your 172 00:10:10,640 --> 00:10:13,440 Speaker 1: location on Earth. This actually takes a bit, right. So 173 00:10:13,440 --> 00:10:15,520 Speaker 1: if you know where a satellite is as it's beaming 174 00:10:15,559 --> 00:10:18,680 Speaker 1: down these radio pulses to you, and you are able 175 00:10:18,760 --> 00:10:22,160 Speaker 1: to get a sequence of measurements, and you're taking the 176 00:10:22,200 --> 00:10:26,000 Speaker 1: Doppler effect into account, and you have all this information 177 00:10:26,040 --> 00:10:29,600 Speaker 1: available to you, you can then use that info to 178 00:10:30,280 --> 00:10:33,760 Speaker 1: reckon where you are on Earth. You have to keep 179 00:10:33,800 --> 00:10:36,560 Speaker 1: receiving signals as the satellite is moving through its orbit 180 00:10:36,760 --> 00:10:40,400 Speaker 1: and then use the series of data pulses to track 181 00:10:40,440 --> 00:10:44,080 Speaker 1: where you are on Earth. If a satellite isn't within range, 182 00:10:44,320 --> 00:10:46,360 Speaker 1: then you have to wait until one is close enough 183 00:10:46,400 --> 00:10:48,240 Speaker 1: to you for you to start picking up the signals. 184 00:10:48,240 --> 00:10:50,640 Speaker 1: That could be up to an hour, depending upon when 185 00:10:50,640 --> 00:10:53,880 Speaker 1: the last one passed overhead, but it would work. So 186 00:10:54,280 --> 00:10:58,760 Speaker 1: this would become a very early satellite based navigation system 187 00:10:58,840 --> 00:11:02,360 Speaker 1: for the US Navy. So back to our history lesson. 188 00:11:02,720 --> 00:11:06,960 Speaker 1: Following Sputnik's incredible impact both figuratively and then semi literally, 189 00:11:07,000 --> 00:11:09,760 Speaker 1: because it would burn up upon descending through the Earth's 190 00:11:09,760 --> 00:11:13,440 Speaker 1: atmosphere about three months and more than fourteen hundred orbits 191 00:11:13,440 --> 00:11:17,480 Speaker 1: after initial launch, the US Advanced Research Projects Agency, or 192 00:11:17,720 --> 00:11:20,840 Speaker 1: ARPA got to work on funding research for a satellite 193 00:11:20,920 --> 00:11:24,439 Speaker 1: navigation system that would be called TRANSIT. Today we call 194 00:11:24,600 --> 00:11:28,319 Speaker 1: ARPA DARPA, and it's a branch of the US Department 195 00:11:28,360 --> 00:11:31,760 Speaker 1: of Defense that offers contracts to various organizations and companies 196 00:11:31,800 --> 00:11:35,480 Speaker 1: to advance technologies that would be potentially useful in national defense. 197 00:11:35,840 --> 00:11:39,160 Speaker 1: It's the agency that's responsible for bringing together the folks 198 00:11:39,160 --> 00:11:43,600 Speaker 1: who actually built the infrastructure for the Internet. It's also 199 00:11:44,200 --> 00:11:51,400 Speaker 1: largely responsible for the initial boom in autonomous vehicle research. Anyway, 200 00:11:51,679 --> 00:11:55,000 Speaker 1: Transit would be handy for the United States Navy. The 201 00:11:55,200 --> 00:11:59,199 Speaker 1: boffins over at Johns Hopkins University APL designed the satellites, 202 00:11:59,240 --> 00:12:03,640 Speaker 1: which were intend to provide location information on Earth and 203 00:12:04,520 --> 00:12:07,600 Speaker 1: in the Earth's socians, to an accuracy of within tens 204 00:12:07,640 --> 00:12:11,320 Speaker 1: of meters, which thay sounds pretty loosey goosey, right, Like, 205 00:12:11,559 --> 00:12:14,840 Speaker 1: if you were tens of meters away from your location 206 00:12:15,000 --> 00:12:16,960 Speaker 1: based upon the app you would think, wow, this is 207 00:12:16,960 --> 00:12:21,360 Speaker 1: not very useful. But at the time it was significantly 208 00:12:21,360 --> 00:12:23,720 Speaker 1: more accurate than what we had been used to, So 209 00:12:23,880 --> 00:12:26,960 Speaker 1: we were able to use this for mapping purposes and 210 00:12:27,040 --> 00:12:30,400 Speaker 1: it was really handy. It would allow for far more precision, 211 00:12:30,880 --> 00:12:33,320 Speaker 1: and it proved beyond a shadow of a doubt that 212 00:12:33,400 --> 00:12:37,199 Speaker 1: England is not a conspiracy among cartographers and shout out 213 00:12:37,240 --> 00:12:40,520 Speaker 1: to me if you actually recognize that reference. The first 214 00:12:40,559 --> 00:12:44,400 Speaker 1: attempt to get a Transit satellite into orbit was a failure. 215 00:12:44,679 --> 00:12:47,600 Speaker 1: As Monty Python might put it, it sank into the swamp, 216 00:12:47,920 --> 00:12:50,760 Speaker 1: but it did not take four tries to get it right. 217 00:12:51,040 --> 00:12:55,720 Speaker 1: Transit one B successfully achieved orbit on April thirteenth, nineteen sixty. 218 00:12:56,080 --> 00:13:00,320 Speaker 1: It passed test with orbiting colors, but it would take 219 00:13:00,360 --> 00:13:02,760 Speaker 1: more satellites. To create a system that would be useful 220 00:13:02,840 --> 00:13:05,240 Speaker 1: and reliable, you needed a group of them, or a 221 00:13:05,320 --> 00:13:08,880 Speaker 1: constellation of satellites in other words, and that's what we 222 00:13:08,920 --> 00:13:13,040 Speaker 1: call a collection of satellites that collectively provide some specific 223 00:13:13,080 --> 00:13:16,880 Speaker 1: information or service. It's a constellation anyway. By the mid 224 00:13:16,960 --> 00:13:20,800 Speaker 1: nineteen sixties, the US launched several satellites into orbit, and 225 00:13:20,840 --> 00:13:24,480 Speaker 1: this orbital path took the satellites past the Earth's poles, 226 00:13:24,920 --> 00:13:27,720 Speaker 1: and once there were six satellites making up a very 227 00:13:27,760 --> 00:13:30,959 Speaker 1: small constellation. The Navy would use those satellites and the 228 00:13:31,000 --> 00:13:34,040 Speaker 1: Doppler effect to keep track of US subs that happen 229 00:13:34,080 --> 00:13:37,160 Speaker 1: to be carrying big old boom booms on them, like 230 00:13:37,520 --> 00:13:40,360 Speaker 1: the nuclear kind of boom booms. When you're on a 231 00:13:40,400 --> 00:13:43,600 Speaker 1: submersible that happens to be outfitted with nuclear weaponry, you 232 00:13:43,679 --> 00:13:46,120 Speaker 1: want to keep an accurate account of where you are 233 00:13:46,280 --> 00:13:50,120 Speaker 1: and where you're going, and more importantly, the country that's 234 00:13:50,120 --> 00:13:52,400 Speaker 1: in charge of you wants to know where you are, 235 00:13:52,640 --> 00:13:56,880 Speaker 1: because if you suddenly disappear, that's a huge problem. Using transit, 236 00:13:56,920 --> 00:14:00,240 Speaker 1: the subs could gain accurate location reading from satellite in 237 00:14:00,400 --> 00:14:03,079 Speaker 1: just a few minutes, which again was a huge improvement 238 00:14:03,240 --> 00:14:08,360 Speaker 1: over simply using map making and plotting. I mean, there 239 00:14:08,400 --> 00:14:11,640 Speaker 1: are people who are phenomenal at figuring out where a 240 00:14:11,679 --> 00:14:16,040 Speaker 1: submarine is based upon knowing the heading and how long 241 00:14:16,280 --> 00:14:19,960 Speaker 1: a sub was traveling in that direction. I marvel at 242 00:14:20,000 --> 00:14:24,680 Speaker 1: it when I see films of navigators doing those kind 243 00:14:24,720 --> 00:14:28,480 Speaker 1: of calculations. But the nice thing is this would allow 244 00:14:28,600 --> 00:14:33,200 Speaker 1: for relatively quick and accurate results, assuming that you were 245 00:14:33,280 --> 00:14:37,800 Speaker 1: within range of receiving a satellite signal. The US Navy 246 00:14:37,800 --> 00:14:41,040 Speaker 1: took over the operation of these satellites from ARPA by 247 00:14:41,160 --> 00:14:44,240 Speaker 1: the mid nineteen sixties, and by nineteen sixty eight the 248 00:14:44,280 --> 00:14:47,720 Speaker 1: system had a total of thirty six satellites in orbit. 249 00:14:48,280 --> 00:14:50,480 Speaker 1: While the primary function of the system was to keep 250 00:14:50,560 --> 00:14:53,920 Speaker 1: tabs on nuclear armed submarines, researchers also used it to 251 00:14:53,920 --> 00:14:56,360 Speaker 1: map out locations, including using it to get a more 252 00:14:56,480 --> 00:14:59,720 Speaker 1: accurate measurement of Mount Everest's elevation, which I thought was 253 00:14:59,760 --> 00:15:02,920 Speaker 1: pretty neat. Now. That was in the nineteen sixties and 254 00:15:03,040 --> 00:15:06,360 Speaker 1: nineteen seventies, and transit would remain in operation until nineteen 255 00:15:06,440 --> 00:15:09,640 Speaker 1: ninety six, at which point it was retired for navigational 256 00:15:09,680 --> 00:15:14,480 Speaker 1: purposes anyway, in favor of GPS, which had come online 257 00:15:14,520 --> 00:15:18,680 Speaker 1: not long before that, actually, but we've still got some 258 00:15:18,720 --> 00:15:21,960 Speaker 1: steps in between that we're going to need to talk about. 259 00:15:22,000 --> 00:15:25,160 Speaker 1: So while Transit was taking shape with occasional launches to 260 00:15:25,160 --> 00:15:28,560 Speaker 1: build out its constellation, another team over at the Aerospace 261 00:15:28,600 --> 00:15:33,240 Speaker 1: Corporation was developing a more advanced navigational satellite system. Among 262 00:15:33,280 --> 00:15:40,200 Speaker 1: the scientists and engineers was Ivan getting Hideyoshi Nakamura, James Woodford, 263 00:15:40,320 --> 00:15:42,760 Speaker 1: and Philip Diamond, and they figured out that with a 264 00:15:42,840 --> 00:15:46,120 Speaker 1: large enough constellation of satellites, with each satellite carrying an 265 00:15:46,200 --> 00:15:50,000 Speaker 1: incredibly accurate clock on board, you could provide even more 266 00:15:50,040 --> 00:15:53,720 Speaker 1: accurate positional information to a receiver on Earth. What's more, 267 00:15:53,960 --> 00:15:57,280 Speaker 1: the receiver itself wouldn't need to be a super accurate clock. 268 00:15:57,720 --> 00:15:59,880 Speaker 1: The clocks would just be on the satellites, and this 269 00:16:00,040 --> 00:16:04,720 Speaker 1: would dramatically reduce the cost of building out receivers on land. 270 00:16:04,960 --> 00:16:08,200 Speaker 1: Like before, if the receiver on land needed to have 271 00:16:08,640 --> 00:16:12,920 Speaker 1: an incredibly accurate clock as well as the satellite, then 272 00:16:13,080 --> 00:16:16,320 Speaker 1: the cost would have been prohibitive for the average person. 273 00:16:16,760 --> 00:16:21,000 Speaker 1: But this brought all the onus of time keeping onto 274 00:16:21,040 --> 00:16:23,400 Speaker 1: the satellite site, not the receiver side, and it made 275 00:16:23,400 --> 00:16:27,040 Speaker 1: it much much more affordable. So you still need those 276 00:16:27,080 --> 00:16:29,600 Speaker 1: clocks in the satellites themselves, but the receivers on Earth 277 00:16:29,640 --> 00:16:33,200 Speaker 1: could be drastically simplified and manageurized and again accurate reading 278 00:16:33,240 --> 00:16:36,320 Speaker 1: on position. A receiver would need to connect with four satellites, 279 00:16:36,360 --> 00:16:39,040 Speaker 1: so the constellation of navigational spacecraft would need to be 280 00:16:39,120 --> 00:16:42,000 Speaker 1: fairly large in order to be able to receive signals 281 00:16:42,000 --> 00:16:45,520 Speaker 1: from four satellites simultaneously. But those four satellites would give 282 00:16:45,600 --> 00:16:49,280 Speaker 1: enough information to really hone in on the receiver's location 283 00:16:49,760 --> 00:16:52,200 Speaker 1: here on Earth. So what we're going to do now 284 00:16:52,280 --> 00:16:54,000 Speaker 1: is we're going to take a quick break to thank 285 00:16:54,080 --> 00:16:56,480 Speaker 1: our sponsor, and then when we come back, I'll talk 286 00:16:56,560 --> 00:17:00,960 Speaker 1: more about how this works, like how state lights are 287 00:17:01,320 --> 00:17:04,040 Speaker 1: able to send information that a receiver on Earth can 288 00:17:04,080 --> 00:17:08,320 Speaker 1: take and interpret as positional information on the surface of 289 00:17:08,320 --> 00:17:21,240 Speaker 1: the planet. But first let's take this quick break, all right. 290 00:17:21,320 --> 00:17:23,640 Speaker 1: I think it's best we now take time to talk 291 00:17:23,640 --> 00:17:27,040 Speaker 1: about how all this works, and that's what we've been 292 00:17:27,040 --> 00:17:29,960 Speaker 1: building towards. So remember when I said my parents live 293 00:17:30,400 --> 00:17:34,040 Speaker 1: like twenty miles away from me, and that just tells 294 00:17:34,080 --> 00:17:36,800 Speaker 1: you that they're somewhere within a twenty mile radius of 295 00:17:36,880 --> 00:17:40,239 Speaker 1: my location. That's that's all it tells you. But if 296 00:17:40,280 --> 00:17:42,800 Speaker 1: I gave you another data point. Let's say that I said, oh, 297 00:17:42,840 --> 00:17:46,400 Speaker 1: they happen to live seventy miles from Athens, Georgia. Well, 298 00:17:46,440 --> 00:17:48,679 Speaker 1: now you can take a map and draw two circles, 299 00:17:48,760 --> 00:17:51,640 Speaker 1: assuming you know where I live. So one circle would 300 00:17:51,640 --> 00:17:54,919 Speaker 1: be centered on my location with a twenty mile radius 301 00:17:54,960 --> 00:17:59,280 Speaker 1: around it. The second circle would be around Athens, Georgia 302 00:17:59,359 --> 00:18:02,080 Speaker 1: at the center. It would extend out seventy miles. So 303 00:18:02,119 --> 00:18:05,399 Speaker 1: these two circles would overlap slightly. They kind of cross 304 00:18:05,520 --> 00:18:08,080 Speaker 1: one another at two points, kind of like a ven diagram. 305 00:18:08,200 --> 00:18:10,600 Speaker 1: And now you've narrowed down my parents' house to one 306 00:18:10,720 --> 00:18:14,199 Speaker 1: of two possible points. Because where they live needs to 307 00:18:14,200 --> 00:18:16,880 Speaker 1: be within twenty miles of me and seventy miles of Athens. 308 00:18:16,920 --> 00:18:19,880 Speaker 1: That only leaves two locations on the map. Now, unless 309 00:18:19,880 --> 00:18:21,840 Speaker 1: one of those points happens to be somewhere where a 310 00:18:21,880 --> 00:18:24,840 Speaker 1: house could not possibly be located, like in the middle 311 00:18:24,880 --> 00:18:28,120 Speaker 1: of a lake or something, they're still ambiguity. You don't 312 00:18:28,160 --> 00:18:31,320 Speaker 1: know if they're in location one or location two. Ah. 313 00:18:31,560 --> 00:18:34,240 Speaker 1: But what if I also said my parents live within 314 00:18:34,760 --> 00:18:38,080 Speaker 1: or ten miles away from the amusement park six lags 315 00:18:38,080 --> 00:18:40,800 Speaker 1: over Georgia. Well, you could draw a third circle with 316 00:18:40,880 --> 00:18:43,720 Speaker 1: a radius of ten miles around that park, and you 317 00:18:43,760 --> 00:18:46,440 Speaker 1: should see that this circle intersects with the other two 318 00:18:46,600 --> 00:18:50,480 Speaker 1: already drawn at a single point. They three circles meet 319 00:18:50,600 --> 00:18:53,639 Speaker 1: only in one location, and that is where my parents 320 00:18:53,680 --> 00:18:56,359 Speaker 1: would live, or it would be if I weren't giving 321 00:18:56,840 --> 00:19:00,800 Speaker 1: total made up answers to these different distances. For one thing, 322 00:19:00,880 --> 00:19:03,760 Speaker 1: I don't think you could have circles that overlap seventy 323 00:19:03,840 --> 00:19:06,280 Speaker 1: miles out from Athens and ten miles out from six Legs. 324 00:19:06,280 --> 00:19:09,720 Speaker 1: They're too far apart. But you get the idea. GPS 325 00:19:09,760 --> 00:19:12,199 Speaker 1: satellites work in a similar way, except we need to 326 00:19:12,200 --> 00:19:15,720 Speaker 1: think about spheres rather than circles. We have to go 327 00:19:15,760 --> 00:19:19,280 Speaker 1: into three dimensions, right, So a GPS satellite essentially sends 328 00:19:19,280 --> 00:19:22,200 Speaker 1: out a pulse of data and it indicates a time 329 00:19:22,320 --> 00:19:26,400 Speaker 1: stamp and the satellite's location. A receiver on Earth receives 330 00:19:26,480 --> 00:19:28,840 Speaker 1: this message and by doing a little math, figures out 331 00:19:29,040 --> 00:19:33,280 Speaker 1: how far away it is from the satellite by knowing 332 00:19:33,320 --> 00:19:35,879 Speaker 1: how long it took the message to travel from the 333 00:19:35,920 --> 00:19:38,800 Speaker 1: satellite to the receiver. These pulses are traveling at the 334 00:19:38,800 --> 00:19:41,560 Speaker 1: speed of light, so we actually do know the velocity 335 00:19:41,720 --> 00:19:44,680 Speaker 1: or the speed rather of those signals. So we've got 336 00:19:44,800 --> 00:19:48,360 Speaker 1: time and we've got speed. We need to figure out 337 00:19:48,480 --> 00:19:52,680 Speaker 1: the distance to know how far the receiver is from 338 00:19:52,720 --> 00:19:56,919 Speaker 1: the specific satellite, and we can eliminate all the positions 339 00:19:57,240 --> 00:20:00,880 Speaker 1: that aren't on Earth. Right once we figure out, oh, 340 00:20:00,880 --> 00:20:03,320 Speaker 1: it took x amount of time to get here, that 341 00:20:03,359 --> 00:20:06,800 Speaker 1: means where why number of miles away from the satellite 342 00:20:06,880 --> 00:20:09,600 Speaker 1: we happen to know where the satellite is located, you 343 00:20:09,640 --> 00:20:14,480 Speaker 1: could create a sphere representing all the points around the 344 00:20:14,480 --> 00:20:17,480 Speaker 1: satellite that are the proper distance away. A lot of 345 00:20:17,520 --> 00:20:19,600 Speaker 1: those points are going to be out in space. We 346 00:20:19,680 --> 00:20:23,359 Speaker 1: can disregard those because obviously we're not in outer space. 347 00:20:23,720 --> 00:20:26,439 Speaker 1: But for the ones that are on Earth, there's going 348 00:20:26,480 --> 00:20:28,320 Speaker 1: to be a lot, right, Some are going to actually 349 00:20:28,320 --> 00:20:32,359 Speaker 1: extend into the Earth. We can probably dismiss those as well. 350 00:20:32,640 --> 00:20:34,640 Speaker 1: So we're just looking at the ones that actually intersect 351 00:20:34,680 --> 00:20:37,439 Speaker 1: with the surface of the Earth. But there's still a lot, 352 00:20:37,600 --> 00:20:39,840 Speaker 1: so we have to narrow it down. We do that 353 00:20:40,240 --> 00:20:46,480 Speaker 1: by receiving multiple signals from multiple satellites, preferably for satellites 354 00:20:46,560 --> 00:20:49,679 Speaker 1: to really get rid of any ambiguity. If the receiver 355 00:20:49,760 --> 00:20:52,920 Speaker 1: does this with at least three but typically four satellites. 356 00:20:52,920 --> 00:20:55,080 Speaker 1: Then it can pinpoint where on the surface of the 357 00:20:55,119 --> 00:20:58,200 Speaker 1: Earth the receiver happens to be. It's a clever way 358 00:20:58,200 --> 00:21:01,040 Speaker 1: to figure out locations because once we do figure out all, right, 359 00:21:01,080 --> 00:21:05,159 Speaker 1: where why number of miles from satellite A, where Z 360 00:21:05,359 --> 00:21:08,439 Speaker 1: number of miles from satellite B, where AA number of 361 00:21:08,480 --> 00:21:13,840 Speaker 1: miles or satellite three and BB from satellite four, you 362 00:21:14,080 --> 00:21:16,600 Speaker 1: create the spheres around all four of those satellites. You 363 00:21:16,640 --> 00:21:18,440 Speaker 1: know where they are, they've told you where they are. 364 00:21:18,480 --> 00:21:21,080 Speaker 1: You know what time stamps you're looking at. The time 365 00:21:21,119 --> 00:21:24,720 Speaker 1: stamps also need to be in sync with the receiver's clock, 366 00:21:24,800 --> 00:21:27,040 Speaker 1: but the receiver's clock can be modified here on Earth. 367 00:21:27,040 --> 00:21:29,080 Speaker 1: We don't have to worry about the satellites doing that, 368 00:21:29,480 --> 00:21:33,520 Speaker 1: and collectively that will end up giving you a single 369 00:21:33,520 --> 00:21:37,040 Speaker 1: location where it's the only place on the surface of 370 00:21:37,040 --> 00:21:40,399 Speaker 1: the Earth where all of those points of data converge. 371 00:21:40,640 --> 00:21:43,960 Speaker 1: And that's how GPS works. So the scientists work fed 372 00:21:44,080 --> 00:21:46,720 Speaker 1: nicely into work that was already being done at the 373 00:21:46,800 --> 00:21:50,320 Speaker 1: US Naval Center for Space Technology, where other brilliant people 374 00:21:50,320 --> 00:21:53,480 Speaker 1: were hard at work developing atomic clocks. So let's talk 375 00:21:53,480 --> 00:21:57,120 Speaker 1: about that for a second too, because this timekeeping element 376 00:21:57,359 --> 00:22:02,199 Speaker 1: is absolutely vital for navigation purposes. Remember, all of our 377 00:22:02,280 --> 00:22:06,480 Speaker 1: navigation calculations are based upon how far we are from 378 00:22:06,520 --> 00:22:10,280 Speaker 1: these satellites. But if the timekeeping is off, then our 379 00:22:10,320 --> 00:22:13,080 Speaker 1: distance is going to be off, which means we're going 380 00:22:13,119 --> 00:22:15,600 Speaker 1: to think we're somewhere else on the surface of the 381 00:22:15,600 --> 00:22:18,199 Speaker 1: Earth and where we actually are. So let's take quartz 382 00:22:18,280 --> 00:22:21,480 Speaker 1: based risk watches as sort of a starting point. Quarts 383 00:22:21,600 --> 00:22:25,920 Speaker 1: will vibrate physically when subjected to a voltage. This relates 384 00:22:25,960 --> 00:22:29,200 Speaker 1: to piezo electricity, which is the ability for certain materials 385 00:22:29,200 --> 00:22:32,040 Speaker 1: like quartz to store an electric charge in response to 386 00:22:32,080 --> 00:22:35,720 Speaker 1: mechanical force that's been applied to that substance. In other words, 387 00:22:35,720 --> 00:22:39,680 Speaker 1: like if you'll whack quartz, it'll build up an electric charge. 388 00:22:39,840 --> 00:22:43,679 Speaker 1: But the other effect can also be true. Certain materials, 389 00:22:43,720 --> 00:22:47,280 Speaker 1: when exposed to an electric field, will produce physical vibrations, 390 00:22:47,320 --> 00:22:50,720 Speaker 1: and quartz is one of those materials. What's more, it 391 00:22:50,760 --> 00:22:54,360 Speaker 1: will always produce the same frequency of vibrations in response 392 00:22:54,400 --> 00:22:58,159 Speaker 1: to specific applied voltage. So if you apply the same 393 00:22:58,280 --> 00:23:01,600 Speaker 1: voltage over and over, is going to vibrate at the 394 00:23:01,640 --> 00:23:05,400 Speaker 1: same frequency over and over. It does not vary, at 395 00:23:05,480 --> 00:23:09,320 Speaker 1: least not for the purposes of wristwatches. As it turns out, 396 00:23:09,359 --> 00:23:13,760 Speaker 1: for the purposes of space navigation, it's not nearly precise enough. 397 00:23:13,920 --> 00:23:16,479 Speaker 1: But if you apply specific voltage to a quartz crystal, 398 00:23:16,480 --> 00:23:19,200 Speaker 1: the crystal will produce a vibration of a specific frequency, 399 00:23:19,240 --> 00:23:21,240 Speaker 1: which you can then use as if it were the 400 00:23:21,280 --> 00:23:24,760 Speaker 1: swinging pendulum of an old timey grandfather clock, and you 401 00:23:24,800 --> 00:23:28,560 Speaker 1: can calculate the passage of time by the frequency of vibrations. 402 00:23:28,840 --> 00:23:33,760 Speaker 1: If you know that it takes twenty thousand vibrations per second, 403 00:23:34,240 --> 00:23:36,600 Speaker 1: then once you hit twenty thousand, you know a second 404 00:23:36,640 --> 00:23:40,480 Speaker 1: has passed. That's essentially how it works. Now, atomic clocks 405 00:23:40,520 --> 00:23:44,679 Speaker 1: are not that different, but there are many orders of 406 00:23:44,720 --> 00:23:48,920 Speaker 1: magnitude far more precise. So quartz crystals are consistent enough 407 00:23:48,960 --> 00:23:52,159 Speaker 1: for our earthly needs, but when it comes to space operations, 408 00:23:52,160 --> 00:23:55,879 Speaker 1: we need much more stability and much more accuracy. A 409 00:23:55,960 --> 00:23:59,359 Speaker 1: quartz space clock will gradually start to drift and start 410 00:23:59,400 --> 00:24:02,520 Speaker 1: to lose accuracy over time. Now, it typically takes a while. 411 00:24:02,920 --> 00:24:04,800 Speaker 1: It might be more than a month before the clock 412 00:24:04,880 --> 00:24:07,280 Speaker 1: is off by so much as a millisecond, but that 413 00:24:07,320 --> 00:24:11,520 Speaker 1: would still be enough to provide extremely wrong navigational information. 414 00:24:11,960 --> 00:24:15,560 Speaker 1: So imagine you're looking at your GPS app and you 415 00:24:15,800 --> 00:24:18,960 Speaker 1: are flabbric acid because according to the app, you are 416 00:24:18,960 --> 00:24:22,080 Speaker 1: like two hundred miles away from you where you actually are. 417 00:24:22,400 --> 00:24:24,520 Speaker 1: And it's all because the receiver would be depending upon 418 00:24:24,640 --> 00:24:27,399 Speaker 1: the wrong information, that time code would be wrong, and 419 00:24:27,440 --> 00:24:30,240 Speaker 1: that would mean that it would be calculating the wrong distance. 420 00:24:30,560 --> 00:24:35,560 Speaker 1: So yeah, a small error in space translates into an 421 00:24:35,760 --> 00:24:38,760 Speaker 1: enormous error when you get to navigation systems on Earth. 422 00:24:38,920 --> 00:24:43,479 Speaker 1: So atomic clocks rely upon oscillations of atomic energy states. 423 00:24:43,560 --> 00:24:47,680 Speaker 1: Like think of electron energy states. You probably know atoms 424 00:24:47,680 --> 00:24:51,800 Speaker 1: are made up of a nucleus around which are orbiting electrons. 425 00:24:51,800 --> 00:24:54,960 Speaker 1: These electrons in habit various energy states. If you pour 426 00:24:55,119 --> 00:24:58,920 Speaker 1: energy into an atom, you can make an electron go 427 00:24:59,440 --> 00:25:02,960 Speaker 1: move out to a higher energy state, and then once 428 00:25:03,040 --> 00:25:06,560 Speaker 1: you stop pouring energy in, the electron will naturally move 429 00:25:06,640 --> 00:25:10,800 Speaker 1: back down to its normal energy state. So this can 430 00:25:10,840 --> 00:25:13,879 Speaker 1: be an oscillation. Now to go into this further, to 431 00:25:14,000 --> 00:25:16,800 Speaker 1: really dive into it, would get far too complicated for 432 00:25:16,840 --> 00:25:19,199 Speaker 1: this episode. But the important thing to remember is that 433 00:25:19,280 --> 00:25:22,639 Speaker 1: atomic clocks are both more stable and more accurate than 434 00:25:22,720 --> 00:25:25,760 Speaker 1: quartz crystal based time pieces. Depending on the type of 435 00:25:25,840 --> 00:25:30,400 Speaker 1: atom being used, the clock might count billions of oscillations 436 00:25:30,440 --> 00:25:34,640 Speaker 1: per second, like more than nine billion, So you're really 437 00:25:34,680 --> 00:25:40,960 Speaker 1: dividing a second down into unfathomably small units of time 438 00:25:41,280 --> 00:25:44,240 Speaker 1: by looking at the frequency of these oscillations. This is 439 00:25:44,280 --> 00:25:47,600 Speaker 1: an incredible level of accuracy, which is a necessary component 440 00:25:47,600 --> 00:25:50,520 Speaker 1: when we're talking about navigation. But I also promise y' 441 00:25:50,520 --> 00:25:53,199 Speaker 1: all some relativity up here in this podcast. So what 442 00:25:53,359 --> 00:25:57,600 Speaker 1: does that have to do with anything, Well, Einstein's theories 443 00:25:57,600 --> 00:26:01,240 Speaker 1: of relativity. Both of these special relativity and general relativity 444 00:26:01,320 --> 00:26:04,600 Speaker 1: varieties have something to say about the passage of time. 445 00:26:04,880 --> 00:26:08,240 Speaker 1: It's all relative, you see. And some factors that determine 446 00:26:08,240 --> 00:26:11,240 Speaker 1: the speed at which time passes for a subject relative 447 00:26:11,280 --> 00:26:15,480 Speaker 1: to an outside observer includes stuff like gravity and speed. Now, 448 00:26:16,560 --> 00:26:19,040 Speaker 1: let's get one thing out of the way first, because 449 00:26:19,040 --> 00:26:22,439 Speaker 1: this gets whibbly wobbly timey. Whymy, Like, you wouldn't believe 450 00:26:22,920 --> 00:26:26,879 Speaker 1: the passage of time to an observer like their own sense, 451 00:26:26,920 --> 00:26:29,879 Speaker 1: their own sensation of the passage of time, that doesn't change. 452 00:26:29,960 --> 00:26:33,600 Speaker 1: To them. Time continues on as it would in any 453 00:26:33,640 --> 00:26:38,240 Speaker 1: other condition. It's only as they observe outside points of 454 00:26:38,280 --> 00:26:42,440 Speaker 1: reference that the sense of time changes. So like, for example, 455 00:26:42,800 --> 00:26:45,040 Speaker 1: one thing is that the faster you go, the slower 456 00:26:45,080 --> 00:26:48,359 Speaker 1: time moves for you relative to an outside observer. So 457 00:26:49,000 --> 00:26:50,960 Speaker 1: if you're in a ship and you're going super super 458 00:26:51,000 --> 00:26:54,119 Speaker 1: super fast, it would feel like time is passing as normal. 459 00:26:54,200 --> 00:26:57,480 Speaker 1: To someone outside of the spaceship here on Earth, it 460 00:26:57,480 --> 00:27:00,520 Speaker 1: would look like you were moving in slow motion. If 461 00:27:00,520 --> 00:27:03,680 Speaker 1: they could magically see you inside this ship, even though 462 00:27:03,680 --> 00:27:05,679 Speaker 1: the ship is moving super fast, you would appear to 463 00:27:05,680 --> 00:27:08,320 Speaker 1: be moving at a crawl. And that's why at the 464 00:27:08,440 --> 00:27:11,600 Speaker 1: end of your journey, when you would get off your spaceship, 465 00:27:12,080 --> 00:27:14,920 Speaker 1: your friends and family who had stayed behind on Earth 466 00:27:14,960 --> 00:27:18,040 Speaker 1: would have all aged much more than you did, because 467 00:27:18,320 --> 00:27:22,199 Speaker 1: relative to them, time passed more slowly. For you. Your experience, however, 468 00:27:22,400 --> 00:27:25,639 Speaker 1: was that time just continued on as it always has, 469 00:27:26,200 --> 00:27:29,399 Speaker 1: very very mind binding kind of stuff. Right, But what 470 00:27:29,440 --> 00:27:32,000 Speaker 1: does this have to do with satellites. Well, let's talk 471 00:27:32,000 --> 00:27:36,000 Speaker 1: about general relativity first. It explains that gravity can alter 472 00:27:36,200 --> 00:27:39,639 Speaker 1: time such that a satellite that's in orbit around Earth 473 00:27:40,119 --> 00:27:42,560 Speaker 1: will have clocks that are running a little bit faster 474 00:27:43,000 --> 00:27:45,160 Speaker 1: than they would if they were just on Earth. And 475 00:27:45,240 --> 00:27:47,199 Speaker 1: by a little bit faster, I'm talking about like forty 476 00:27:47,200 --> 00:27:52,240 Speaker 1: five microseconds per day drifting right, like they're getting ahead 477 00:27:52,600 --> 00:27:56,680 Speaker 1: by about forty five microseconds per day. However, we also 478 00:27:56,760 --> 00:28:00,120 Speaker 1: have special relativity. This says that because the satellites are 479 00:28:00,119 --> 00:28:02,720 Speaker 1: whizzing through space pretty darn fast, the clocks run a 480 00:28:02,720 --> 00:28:06,040 Speaker 1: little more slowly relative to the ones on Earth, and 481 00:28:06,080 --> 00:28:09,399 Speaker 1: they end up losing about seven microseconds per day. So 482 00:28:09,920 --> 00:28:11,880 Speaker 1: you've got to factor both of these in. Right, you're 483 00:28:11,960 --> 00:28:15,000 Speaker 1: gaining forty five microseconds on one side and losing seven 484 00:28:15,080 --> 00:28:17,640 Speaker 1: microseconds on the other side. But this means that we 485 00:28:17,800 --> 00:28:23,560 Speaker 1: have to send up clock modifications corrections to the satellite's 486 00:28:23,800 --> 00:28:26,359 Speaker 1: clocks in order to adjust them and make sure they 487 00:28:26,359 --> 00:28:30,600 Speaker 1: don't drift too much over time, because the longer they 488 00:28:30,640 --> 00:28:33,600 Speaker 1: do so without a correction, the more inaccurate the results 489 00:28:33,600 --> 00:28:35,479 Speaker 1: are going to be here on Earth when we're depending 490 00:28:35,560 --> 00:28:37,879 Speaker 1: upon them for navigation. All right, let's get back to 491 00:28:37,920 --> 00:28:41,040 Speaker 1: our history. So in the late nineteen seventies, a US 492 00:28:41,080 --> 00:28:45,000 Speaker 1: military GPS constellation was slowly taking shape, and initially it 493 00:28:45,040 --> 00:28:48,080 Speaker 1: was called Navstar. And this project took the work that 494 00:28:48,160 --> 00:28:51,680 Speaker 1: was being done independently in the Army, the Navy, and 495 00:28:51,720 --> 00:28:55,240 Speaker 1: the Air Force and kind of brought all that learning 496 00:28:55,320 --> 00:29:01,160 Speaker 1: together and became a really massive nationwide effort and eventually 497 00:29:01,200 --> 00:29:03,240 Speaker 1: it would evolve into what we just referred to as 498 00:29:03,280 --> 00:29:07,240 Speaker 1: GPS these days. The first fully operational satellite in the 499 00:29:07,320 --> 00:29:11,520 Speaker 1: GPS constellation would finally launch in nineteen eighty nine. So yeah, 500 00:29:11,680 --> 00:29:14,120 Speaker 1: this was a system that was in development for like 501 00:29:14,240 --> 00:29:18,200 Speaker 1: two decades pretty much, and then finally in nineteen eighty nine, 502 00:29:18,240 --> 00:29:20,960 Speaker 1: the first satellite goes up. And that's just one. You 503 00:29:21,040 --> 00:29:24,280 Speaker 1: can't navigate just on one satellite, at least not using 504 00:29:24,320 --> 00:29:29,280 Speaker 1: this trilateration approach. But meanwhile, manufacturers here on Terra Firma 505 00:29:29,440 --> 00:29:33,280 Speaker 1: were busy building the navigation devices that would be reliant 506 00:29:33,360 --> 00:29:36,040 Speaker 1: upon these satellites once there were more up in orbit, 507 00:29:36,560 --> 00:29:41,200 Speaker 1: and this would include handheld navigation units. The constellation of 508 00:29:41,240 --> 00:29:44,960 Speaker 1: GPS satellites wouldn't reach what old Emperor Palpatine would consider 509 00:29:45,280 --> 00:29:50,600 Speaker 1: fully operational until nineteen ninety five. The military would end 510 00:29:50,680 --> 00:29:53,960 Speaker 1: up receiving clear signals for the purposes of navigation. So 511 00:29:54,000 --> 00:29:56,880 Speaker 1: if you were using GPS and you were in the 512 00:29:56,920 --> 00:29:59,520 Speaker 1: military and you were using it officially, you would get 513 00:29:59,640 --> 00:30:03,280 Speaker 1: really accurate results. However, the same was not true for 514 00:30:03,440 --> 00:30:06,360 Speaker 1: everybody else. The rest of us got something that was 515 00:30:06,400 --> 00:30:10,040 Speaker 1: called selective availability. I mentioned that at the top of 516 00:30:10,080 --> 00:30:14,360 Speaker 1: this episode. So essentially for civilian use, the satellites were 517 00:30:14,440 --> 00:30:19,120 Speaker 1: fudging the timecode just a tiny, tiny amount in those 518 00:30:19,200 --> 00:30:22,760 Speaker 1: data pulses. Now, it wasn't fudging the timecode enough to 519 00:30:22,920 --> 00:30:25,880 Speaker 1: put you well outside where you actually were and make 520 00:30:25,920 --> 00:30:29,840 Speaker 1: it totally useless, but it was enough to muddle the 521 00:30:29,920 --> 00:30:34,920 Speaker 1: accuracy to within maybe one hundred meters of your actual location. 522 00:30:35,360 --> 00:30:38,320 Speaker 1: So you could still use GPS for general navigation, but 523 00:30:38,360 --> 00:30:40,560 Speaker 1: it wouldn't be suitable for stuff like turn by turn 524 00:30:40,680 --> 00:30:43,880 Speaker 1: directions because the muddled data would not be accurate to 525 00:30:43,920 --> 00:30:47,400 Speaker 1: your real location. So why was this Well, it was 526 00:30:47,440 --> 00:30:50,520 Speaker 1: to protect stuff like military bases and that sort of thing. 527 00:30:50,680 --> 00:30:53,600 Speaker 1: The thought was that the information was potentially too dangerous 528 00:30:53,640 --> 00:30:57,040 Speaker 1: to be made public. This would hold true until two thousand, 529 00:30:57,200 --> 00:31:02,080 Speaker 1: when former President Bill Clinton rescinded select availability. At that point, 530 00:31:02,120 --> 00:31:06,560 Speaker 1: GPS receivers could display accurate information to within a couple 531 00:31:06,560 --> 00:31:09,600 Speaker 1: of meters of a person's actual location on the Earth, 532 00:31:09,640 --> 00:31:12,440 Speaker 1: and this would improve over time, and this is when 533 00:31:12,480 --> 00:31:15,920 Speaker 1: turn by turn directions will become a possibility for civilian use. 534 00:31:16,200 --> 00:31:19,040 Speaker 1: Now today there are more than thirty satellites that are 535 00:31:19,040 --> 00:31:24,200 Speaker 1: part of the GPS constellation. They are frequently updated where 536 00:31:24,360 --> 00:31:28,640 Speaker 1: you know, a newer generation of tech satellite will go 537 00:31:28,720 --> 00:31:31,560 Speaker 1: up and replace ones that are no longer in service 538 00:31:31,640 --> 00:31:37,120 Speaker 1: or have stopped working, and our capabilities improve with each generation. 539 00:31:37,920 --> 00:31:40,240 Speaker 1: The United States is also not the only nation to 540 00:31:40,280 --> 00:31:44,120 Speaker 1: operate a global satellite based navigation system. Russia has an 541 00:31:44,120 --> 00:31:50,480 Speaker 1: alternative to GPS. It's called Glonas GLO NASS. Receivers that 542 00:31:50,520 --> 00:31:54,680 Speaker 1: can work with both GPS and clonos are typically more 543 00:31:54,720 --> 00:31:58,160 Speaker 1: reliable because they can more easily receive signals from, at 544 00:31:58,240 --> 00:32:00,840 Speaker 1: least for satellites, like even if you're a place that 545 00:32:01,160 --> 00:32:05,240 Speaker 1: has lots of tall buildings that might block signals, you 546 00:32:05,320 --> 00:32:07,680 Speaker 1: have a lot more satellites up there that you could 547 00:32:07,680 --> 00:32:11,400 Speaker 1: potentially pull from and thus get a better reading on 548 00:32:11,440 --> 00:32:15,360 Speaker 1: where you are, so you can get devices that are 549 00:32:15,960 --> 00:32:20,200 Speaker 1: compliant with both GPS and GLONAS. Glonas initially completed its 550 00:32:20,200 --> 00:32:22,960 Speaker 1: constellation in nineteen ninety five, the same year that the 551 00:32:23,040 --> 00:32:28,200 Speaker 1: GPS constellation went fully operational, but budget cuts in Russia 552 00:32:28,360 --> 00:32:31,760 Speaker 1: led to degradation of the constellation. It lost some of 553 00:32:31,760 --> 00:32:36,160 Speaker 1: its capability, and eventually Russia was able to reinvest and 554 00:32:36,480 --> 00:32:38,880 Speaker 1: in twenty eleven they were able to bring a full 555 00:32:38,960 --> 00:32:42,520 Speaker 1: constellation back online. It's been pretty much that way ever since. Again, 556 00:32:42,840 --> 00:32:46,880 Speaker 1: like the United States, Russia has also upgraded individual satellites 557 00:32:46,960 --> 00:32:50,000 Speaker 1: in the constellation in order to provide better service. So 558 00:32:50,080 --> 00:32:53,479 Speaker 1: that's it. That's kind of how GPS works. It's really 559 00:32:53,560 --> 00:32:56,800 Speaker 1: all about figuring out where you are based on how 560 00:32:56,840 --> 00:33:00,000 Speaker 1: long it took satellites to send you a little data message. 561 00:33:00,680 --> 00:33:03,760 Speaker 1: You know, it's pretty cool, I think. I think it's 562 00:33:03,800 --> 00:33:08,360 Speaker 1: a really intriguing way to figure out your location. It's 563 00:33:08,360 --> 00:33:11,400 Speaker 1: so clever because it's not relying on things like landmarks 564 00:33:11,480 --> 00:33:13,560 Speaker 1: or anything like that. Not the way that people like 565 00:33:14,160 --> 00:33:18,680 Speaker 1: myself typically navigate, right. I navigate through landmarks and street 566 00:33:18,880 --> 00:33:22,880 Speaker 1: names and that kind of stuff. Occasionally I will reorient 567 00:33:22,960 --> 00:33:26,760 Speaker 1: myself based upon which where the sun is, because I 568 00:33:26,800 --> 00:33:29,720 Speaker 1: know enough to know if it's before noon, the sun's 569 00:33:29,720 --> 00:33:32,720 Speaker 1: in the eastern part of the sky, and if it's afternoon, 570 00:33:32,760 --> 00:33:34,680 Speaker 1: it's in the western part of the sky. Once you 571 00:33:34,720 --> 00:33:37,520 Speaker 1: get past that, all bets are off. I was never 572 00:33:37,560 --> 00:33:40,600 Speaker 1: that good of a boy scout, but yeah, GPS is 573 00:33:40,680 --> 00:33:45,880 Speaker 1: really truly revolutionized travel beyond what I can even express. Like, 574 00:33:46,160 --> 00:33:49,520 Speaker 1: it's hard to communicate to people who have never lived 575 00:33:49,520 --> 00:33:52,719 Speaker 1: without GPS what it was like to try and get around, 576 00:33:52,800 --> 00:33:55,440 Speaker 1: like to have an atlass in your car and you know, 577 00:33:55,560 --> 00:33:58,520 Speaker 1: rely on on paper maps or like in the old, 578 00:33:59,560 --> 00:34:02,600 Speaker 1: the old days of things like map quest, you would 579 00:34:02,720 --> 00:34:05,640 Speaker 1: find turn by turn directions on your computer and then 580 00:34:05,840 --> 00:34:10,479 Speaker 1: print them out or write them down because smartphones weren't 581 00:34:10,480 --> 00:34:12,160 Speaker 1: really a thing yet, so you need to have a 582 00:34:12,200 --> 00:34:15,360 Speaker 1: way to actually carry the directions with you. It's a 583 00:34:15,360 --> 00:34:19,160 Speaker 1: different world these days, but still pretty cool. Like I think, 584 00:34:19,160 --> 00:34:23,240 Speaker 1: it's a neat thing to know that this system works 585 00:34:23,239 --> 00:34:25,360 Speaker 1: in this way. It's also important, by the way, to 586 00:34:25,520 --> 00:34:28,359 Speaker 1: learn how to read maps, because you never know. If 587 00:34:28,400 --> 00:34:31,000 Speaker 1: stuff goes down for whatever reason, you want to be 588 00:34:31,000 --> 00:34:35,160 Speaker 1: able to still get around, like things like solar flares 589 00:34:35,239 --> 00:34:40,000 Speaker 1: coronal mass ejections. These big solar events can sometimes wipe 590 00:34:40,040 --> 00:34:43,120 Speaker 1: out stuff or at least shut things down temporarily, and 591 00:34:43,480 --> 00:34:45,680 Speaker 1: if in the process of that you still need to 592 00:34:45,719 --> 00:34:47,640 Speaker 1: get around, knowing how to read a map can be 593 00:34:47,680 --> 00:34:51,760 Speaker 1: really useful, so it's a skill I recommend developing. That's 594 00:34:51,800 --> 00:34:55,360 Speaker 1: it for this episode. I hope you are all well. 595 00:34:55,440 --> 00:34:58,280 Speaker 1: I hope those of you who have fun trips planned 596 00:34:58,320 --> 00:35:01,560 Speaker 1: in the future can take a moment to appreciate the 597 00:35:01,600 --> 00:35:06,479 Speaker 1: beauty and utility of GPS, and how amazing it is 598 00:35:06,520 --> 00:35:10,280 Speaker 1: that we're using things like theory of relativity and space 599 00:35:10,360 --> 00:35:13,080 Speaker 1: technology just so that you know where you need to 600 00:35:13,120 --> 00:35:15,280 Speaker 1: turn to go to the next in and out burger. 601 00:35:15,400 --> 00:35:18,520 Speaker 1: I think that's pretty cool and I will talk to 602 00:35:18,560 --> 00:35:29,200 Speaker 1: you again really soon. Tech Stuff is an iHeartRadio production. 603 00:35:29,520 --> 00:35:34,520 Speaker 1: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, 604 00:35:34,680 --> 00:35:36,680 Speaker 1: or wherever you listen to your favorite shows.