Speaker 1: Welcome to Tech Stuff, a production from iHeartRadio. Hey there,
Speaker 1: and welcome to tech Stuff. I'm your host, Jonathan Strickland.
Speaker 1: I'm an executive producer with iHeart Podcasts and how the
Speaker 1: tech are you so, y'all. I love to travel. I
Speaker 1: love to visit new places or revisit ones after I've
Speaker 1: been away for a long time. I even don't really
Speaker 1: mind the journey part of travel, which can often be
Speaker 1: you know, stressful, in a hassle if things aren't going well.
Speaker 1: One thing that does give me a huge amount of
Speaker 1: anxiety if I'm traveling is just getting lost or even
Speaker 1: the thought of getting lost. I do not do very
Speaker 1: well with that. There's some part of my brain that
Speaker 1: mistakenly believes that as long as I know where I am,
Speaker 1: nothing can go too wrong. And boy I wish that
Speaker 1: were true, but but yeah, whatever, I just need my
Speaker 1: brain to let me function properly when I'm out on holidays.
Speaker 1: So I remember traveling on my honeymoon to London. At
Speaker 1: that point, I had never been outside the United States before.
Speaker 1: This was my first trip outside the country, and I
Speaker 1: was going to a city that I had read about extensively.
Speaker 1: I knew a lot about London. My major in college
Speaker 1: was in English literature, but it was with a focus
Speaker 1: on medieval studies, so things had changed slightly by the
Speaker 1: time I got there, and reading about a city is
Speaker 1: very different from actually walking around one. Also, my honeymoon
Speaker 1: was in the nineteen nineties because I'm old, and that
Speaker 1: meant I was a decade out from the era of smartphones,
Speaker 1: so I didn't have a handy mobile device to tell
Speaker 1: me where I was as I wandered around the city.
Speaker 1: Even if smartphones had been around back then, I wouldn't
Speaker 1: have been able to rely on map apps on the
Speaker 1: smartphone because of something called selective availability. More on that
Speaker 1: in a bit, but at any rate, I had to
Speaker 1: rely on physical maps to get around and hope that
Speaker 1: I didn't mess it up too badly. Yeah, it's like
Speaker 1: the Stone Age right. Well, these days, as long as
Speaker 1: I have my smartphone with me and I'm not buried
Speaker 1: under a mountain or something, I feel fairly confident I'm
Speaker 1: not going to get lost. If I'm going somewhere that
Speaker 1: has limited connectivity, like limited view of the sky, then
Speaker 1: my anxiety starts to creep in again. But usually I'm okay,
Speaker 1: and that's thanks to the Global Positioning System or GPS.
Speaker 1: So today we're going to learn about GPS, what makes
Speaker 1: it work, how the technology has to take into account,
Speaker 1: Einstein's theories of relativity and more. And a huge thank
Speaker 1: to JP Morgan, Chase Bank, and the United Explorer Card
Speaker 1: for sponsoring this episode. We'll hear more about them later too.
Speaker 1: So GPS, well, that story begins back in the nineteen
Speaker 1: teen fifties when the United States and the then Soviet
Speaker 1: Union were locked in a Cold war, and that cold
Speaker 1: war manifested in many different ways, including an effort to
Speaker 1: launch vehicles into space. For one thing, if you could
Speaker 1: launch a rocket into orbit, then you could show your
Speaker 1: technological superiority over your opponent and say, look how much
Speaker 1: further advanced we are compared to you. But you could
Speaker 1: also send the message of hey, if I can send
Speaker 1: a rocket to space, I could send a rocket to
Speaker 1: your front door, all the way from across the world,
Speaker 1: and it could be carrying a heck of a boom boom.
Speaker 1: Now this gram message underpinned what would become the space race.
Speaker 1: But the space race also meant that brilliant engineers and
Speaker 1: scientists would actually get the resources they needed to advance
Speaker 1: technology by incredible leaps and bounds over the following decades.
Speaker 1: So you got to take the good with the bad, right.
Speaker 1: The good part is you suddenly had actual financial support
Speaker 1: for or incredibly important scientific and engineering work. The bad is, well,
Speaker 1: it was all done in service of this perceived rivalry
Speaker 1: with this massive country on the other side of the globe.
Speaker 1: On October fourth, nineteen fifty seven, at approximately seven thirty pm,
Speaker 1: the USSR launched the first man made satellite into orbit, Sputnik.
Speaker 1: Non past episodes, I have referred to the satellite as
Speaker 1: the ball that went beep. That's not exactly inaccurate. The
Speaker 1: satellite was spherical in shape. It did have these long
Speaker 1: antenna extending out the back of it, so it kind
Speaker 1: of looks like a comet, like a silver comet. But
Speaker 1: the antenna transmitted short radio pulses, and these pulses could
Speaker 1: be picked up very easily by ground based audio receivers,
Speaker 1: including radio sets operated by amateurs, just an amateur radio set.
Speaker 1: This meant that Sputnik's existence couldn't be kept a secret
Speaker 1: because if you or someone you knew operated a radio,
Speaker 1: you could learn about the thing. And in the United States,
Speaker 1: it prompted no small amount of anxiety. Americans believed their
Speaker 1: country was well ahead of the Soviet Union, at least
Speaker 1: on a technological basis. But here they could see that
Speaker 1: their adversary had launched stuff into space and did it
Speaker 1: before the US could do it. That really kicked things
Speaker 1: into gear here in the United States. But I would
Speaker 1: argue that Sputnik would ultimately plant a seed that would
Speaker 1: blossom into GPS further down the line, because here you
Speaker 1: had a satellite sending regular radio signals to Earth, and
Speaker 1: those signals were pretty primitive. Essentially, the satellite was signaling
Speaker 1: that it was within range overhead, along with basic information
Speaker 1: about stuff like air pressure and temperature indicated by the
Speaker 1: length of the radio pulses. Like the pulses didn't give
Speaker 1: data the way Wi Fi does. Literally, you would measure
Speaker 1: how long the pulse lasted and that would tell you, oh,
Speaker 1: the temperature is whatever, if you happen to have the chart.
Speaker 1: Two scientists were able to adfer other information, however, from
Speaker 1: this signal, such as how the propagation of radio signals
Speaker 1: interacted in the upper atmosphere like the ionosphere, and it
Speaker 1: hinted that there could be other uses for as satellite
Speaker 1: beaming information down to Earth. Also, those signals were subject
Speaker 1: to what we call the Doppler effect. It's named after
Speaker 1: Christian Doppler effect. No, I'm sorry, it's just Christian Doppler.
Speaker 1: He first observed this effect back in eighteen forty two.
Speaker 1: And this is how the frequency of a wave changes
Speaker 1: relative to an independent observer if the thing that's emitting
Speaker 1: the wave is moving toward or away from that observer.
Speaker 1: Which was a clumsy explanation, Let's just take an example
Speaker 1: because that makes it way more clear. So let's say
Speaker 1: you're just walking down the street. You're on a sidewalk,
Speaker 1: and say one hundred feet or so in front of you,
Speaker 1: there's an emergency vehicle and it's parked. It's not currently
Speaker 1: driving anywhere, but it is running its siren. The sound
Speaker 1: of that siren is going to remain consistent relative to you, right,
Speaker 1: it may increase and decrease in pitch because the nature
Speaker 1: of the siren, but it's going to keep doing that
Speaker 1: pattern over and over again. But now let's say that
Speaker 1: it's an emergency vehicle that's rushing off away from you.
Speaker 1: It's driving off. You'll notice the pitch of the siren
Speaker 1: will start to go lower. The frequency of the sound
Speaker 1: wave decreases as the vehicle accelerates away from you, or
Speaker 1: let's say the vehicle is driving towards you, the pitch
Speaker 1: of the siren will go up as the frequency increases.
Speaker 1: You can kind of think of it like this. An
Speaker 1: approaching object emitting a wave is effectively pushing or compressing
Speaker 1: that wave as it moves closer to you. An object
Speaker 1: moving away from you is stretching out the wave it's
Speaker 1: emitting as it moves away from you. That is the
Speaker 1: Doppler effect. Scientists at the Applied Physics Laboratory or APL,
Speaker 1: at Johns Hopkins University noticed that the Doppler effect was
Speaker 1: also applicable to Sputnik's radio waves. The satellite's radio pulses
Speaker 1: were compressed as Sputnik would approach, and then they would
Speaker 1: stretch out as the satellite would move away from their
Speaker 1: point of observation, and this meant that just by listening
Speaker 1: to the pulses, the scientists could track Sputnik's movements. They
Speaker 1: didn't need to have eyes on the satellite to track it.
Speaker 1: They could just follow the pulses and observe the Doppler
Speaker 1: effect in order to know generally where it was and
Speaker 1: when it was heading away, but very generally, like they
Speaker 1: couldn't give you a pinpointed location. However, this was another
Speaker 1: important seed for what would become GPS, because it would
Speaker 1: lead to the hypothesis that a satellite could send signals
Speaker 1: to a receiver on Earth, and if that receiver quote
Speaker 1: unquote knew how far away the satellite was from the receiver,
Speaker 1: you could determine the location of that receiver on Earth.
Speaker 1: You would need to be able to get signals from
Speaker 1: more than one satellite, however, to do that, otherwise, you
Speaker 1: would really just know how far away you were from
Speaker 1: one satellite. But that's not really useful information because it
Speaker 1: doesn't narrow stuff down enough, or to put it in
Speaker 1: another way, let's say, let's take this to two dimensions.
Speaker 1: So let's talk about a map. Let's say you've got
Speaker 1: a map of North Georgia, Okay, because that's where I live.
Speaker 1: And I could say, hey, I live twenty miles away
Speaker 1: from my parents. And let's say you happen to know
Speaker 1: where I live. Not that I'm gonna dox myself, but
Speaker 1: let's say you know where I live, so you can
Speaker 1: take that point on the map you could draw out
Speaker 1: a line that's twenty miles out and then create a
Speaker 1: circle with a radius of twenty miles but without more information,
Speaker 1: that could mean they could be anywhere along that circumference
Speaker 1: of the circle right in a radius of twenty miles
Speaker 1: from me. They could be east or west, or north
Speaker 1: or south, or any point in between, as long as
Speaker 1: it was twenty miles out from my location. We'll come
Speaker 1: back to this analogy in a little bit. Let's get
Speaker 1: back to the Doppler effect. It could all be used
Speaker 1: to get a more accurate location. If you know where
Speaker 1: the satellite is as you receive signals, you can use
Speaker 1: a series of pulses from that satellite to determine your
Speaker 1: location on Earth. This actually takes a bit, right. So
Speaker 1: if you know where a satellite is as it's beaming
Speaker 1: down these radio pulses to you, and you are able
Speaker 1: to get a sequence of measurements, and you're taking the
Speaker 1: Doppler effect into account, and you have all this information
Speaker 1: available to you, you can then use that info to
Speaker 1: reckon where you are on Earth. You have to keep
Speaker 1: receiving signals as the satellite is moving through its orbit
Speaker 1: and then use the series of data pulses to track
Speaker 1: where you are on Earth. If a satellite isn't within range,
Speaker 1: then you have to wait until one is close enough
Speaker 1: to you for you to start picking up the signals.
Speaker 1: That could be up to an hour, depending upon when
Speaker 1: the last one passed overhead, but it would work. So
Speaker 1: this would become a very early satellite based navigation system
Speaker 1: for the US Navy. So back to our history lesson.
Speaker 1: Following Sputnik's incredible impact both figuratively and then semi literally,
Speaker 1: because it would burn up upon descending through the Earth's
Speaker 1: atmosphere about three months and more than fourteen hundred orbits
Speaker 1: after initial launch, the US Advanced Research Projects Agency, or
Speaker 1: ARPA got to work on funding research for a satellite
Speaker 1: navigation system that would be called TRANSIT. Today we call
Speaker 1: ARPA DARPA, and it's a branch of the US Department
Speaker 1: of Defense that offers contracts to various organizations and companies
Speaker 1: to advance technologies that would be potentially useful in national defense.
Speaker 1: It's the agency that's responsible for bringing together the folks
Speaker 1: who actually built the infrastructure for the Internet. It's also
Speaker 1: largely responsible for the initial boom in autonomous vehicle research. Anyway,
Speaker 1: Transit would be handy for the United States Navy. The
Speaker 1: boffins over at Johns Hopkins University APL designed the satellites,
Speaker 1: which were intend to provide location information on Earth and
Speaker 1: in the Earth's socians, to an accuracy of within tens
Speaker 1: of meters, which thay sounds pretty loosey goosey, right, Like,
Speaker 1: if you were tens of meters away from your location
Speaker 1: based upon the app you would think, wow, this is
Speaker 1: not very useful. But at the time it was significantly
Speaker 1: more accurate than what we had been used to, So
Speaker 1: we were able to use this for mapping purposes and
Speaker 1: it was really handy. It would allow for far more precision,
Speaker 1: and it proved beyond a shadow of a doubt that
Speaker 1: England is not a conspiracy among cartographers and shout out
Speaker 1: to me if you actually recognize that reference. The first
Speaker 1: attempt to get a Transit satellite into orbit was a failure.
Speaker 1: As Monty Python might put it, it sank into the swamp,
Speaker 1: but it did not take four tries to get it right.
Speaker 1: Transit one B successfully achieved orbit on April thirteenth, nineteen sixty.
Speaker 1: It passed test with orbiting colors, but it would take
Speaker 1: more satellites. To create a system that would be useful
Speaker 1: and reliable, you needed a group of them, or a
Speaker 1: constellation of satellites in other words, and that's what we
Speaker 1: call a collection of satellites that collectively provide some specific
Speaker 1: information or service. It's a constellation anyway. By the mid
Speaker 1: nineteen sixties, the US launched several satellites into orbit, and
Speaker 1: this orbital path took the satellites past the Earth's poles,
Speaker 1: and once there were six satellites making up a very
Speaker 1: small constellation. The Navy would use those satellites and the
Speaker 1: Doppler effect to keep track of US subs that happen
Speaker 1: to be carrying big old boom booms on them, like
Speaker 1: the nuclear kind of boom booms. When you're on a
Speaker 1: submersible that happens to be outfitted with nuclear weaponry, you
Speaker 1: want to keep an accurate account of where you are
Speaker 1: and where you're going, and more importantly, the country that's
Speaker 1: in charge of you wants to know where you are,
Speaker 1: because if you suddenly disappear, that's a huge problem. Using transit,
Speaker 1: the subs could gain accurate location reading from satellite in
Speaker 1: just a few minutes, which again was a huge improvement
Speaker 1: over simply using map making and plotting. I mean, there
Speaker 1: are people who are phenomenal at figuring out where a
Speaker 1: submarine is based upon knowing the heading and how long
Speaker 1: a sub was traveling in that direction. I marvel at
Speaker 1: it when I see films of navigators doing those kind
Speaker 1: of calculations. But the nice thing is this would allow
Speaker 1: for relatively quick and accurate results, assuming that you were
Speaker 1: within range of receiving a satellite signal. The US Navy
Speaker 1: took over the operation of these satellites from ARPA by
Speaker 1: the mid nineteen sixties, and by nineteen sixty eight the
Speaker 1: system had a total of thirty six satellites in orbit.
Speaker 1: While the primary function of the system was to keep
Speaker 1: tabs on nuclear armed submarines, researchers also used it to
Speaker 1: map out locations, including using it to get a more
Speaker 1: accurate measurement of Mount Everest's elevation, which I thought was
Speaker 1: pretty neat. Now. That was in the nineteen sixties and
Speaker 1: nineteen seventies, and transit would remain in operation until nineteen
Speaker 1: ninety six, at which point it was retired for navigational
Speaker 1: purposes anyway, in favor of GPS, which had come online
Speaker 1: not long before that, actually, but we've still got some
Speaker 1: steps in between that we're going to need to talk about.
Speaker 1: So while Transit was taking shape with occasional launches to
Speaker 1: build out its constellation, another team over at the Aerospace
Speaker 1: Corporation was developing a more advanced navigational satellite system. Among
Speaker 1: the scientists and engineers was Ivan getting Hideyoshi Nakamura, James Woodford,
Speaker 1: and Philip Diamond, and they figured out that with a
Speaker 1: large enough constellation of satellites, with each satellite carrying an
Speaker 1: incredibly accurate clock on board, you could provide even more
Speaker 1: accurate positional information to a receiver on Earth. What's more,
Speaker 1: the receiver itself wouldn't need to be a super accurate clock.
Speaker 1: The clocks would just be on the satellites, and this
Speaker 1: would dramatically reduce the cost of building out receivers on land.
Speaker 1: Like before, if the receiver on land needed to have
Speaker 1: an incredibly accurate clock as well as the satellite, then
Speaker 1: the cost would have been prohibitive for the average person.
Speaker 1: But this brought all the onus of time keeping onto
Speaker 1: the satellite site, not the receiver side, and it made
Speaker 1: it much much more affordable. So you still need those
Speaker 1: clocks in the satellites themselves, but the receivers on Earth
Speaker 1: could be drastically simplified and manageurized and again accurate reading
Speaker 1: on position. A receiver would need to connect with four satellites,
Speaker 1: so the constellation of navigational spacecraft would need to be
Speaker 1: fairly large in order to be able to receive signals
Speaker 1: from four satellites simultaneously. But those four satellites would give
Speaker 1: enough information to really hone in on the receiver's location
Speaker 1: here on Earth. So what we're going to do now
Speaker 1: is we're going to take a quick break to thank
Speaker 1: our sponsor, and then when we come back, I'll talk
Speaker 1: more about how this works, like how state lights are
Speaker 1: able to send information that a receiver on Earth can
Speaker 1: take and interpret as positional information on the surface of
Speaker 1: the planet. But first let's take this quick break, all right.
Speaker 1: I think it's best we now take time to talk
Speaker 1: about how all this works, and that's what we've been
Speaker 1: building towards. So remember when I said my parents live
Speaker 1: like twenty miles away from me, and that just tells
Speaker 1: you that they're somewhere within a twenty mile radius of
Speaker 1: my location. That's that's all it tells you. But if
Speaker 1: I gave you another data point. Let's say that I said, oh,
Speaker 1: they happen to live seventy miles from Athens, Georgia. Well,
Speaker 1: now you can take a map and draw two circles,
Speaker 1: assuming you know where I live. So one circle would
Speaker 1: be centered on my location with a twenty mile radius
Speaker 1: around it. The second circle would be around Athens, Georgia
Speaker 1: at the center. It would extend out seventy miles. So
Speaker 1: these two circles would overlap slightly. They kind of cross
Speaker 1: one another at two points, kind of like a ven diagram.
Speaker 1: And now you've narrowed down my parents' house to one
Speaker 1: of two possible points. Because where they live needs to
Speaker 1: be within twenty miles of me and seventy miles of Athens.
Speaker 1: That only leaves two locations on the map. Now, unless
Speaker 1: one of those points happens to be somewhere where a
Speaker 1: house could not possibly be located, like in the middle
Speaker 1: of a lake or something, they're still ambiguity. You don't
Speaker 1: know if they're in location one or location two. Ah.
Speaker 1: But what if I also said my parents live within
Speaker 1: or ten miles away from the amusement park six lags
Speaker 1: over Georgia. Well, you could draw a third circle with
Speaker 1: a radius of ten miles around that park, and you
Speaker 1: should see that this circle intersects with the other two
Speaker 1: already drawn at a single point. They three circles meet
Speaker 1: only in one location, and that is where my parents
Speaker 1: would live, or it would be if I weren't giving
Speaker 1: total made up answers to these different distances. For one thing,
Speaker 1: I don't think you could have circles that overlap seventy
Speaker 1: miles out from Athens and ten miles out from six Legs.
Speaker 1: They're too far apart. But you get the idea. GPS
Speaker 1: satellites work in a similar way, except we need to
Speaker 1: think about spheres rather than circles. We have to go
Speaker 1: into three dimensions, right, So a GPS satellite essentially sends
Speaker 1: out a pulse of data and it indicates a time
Speaker 1: stamp and the satellite's location. A receiver on Earth receives
Speaker 1: this message and by doing a little math, figures out
Speaker 1: how far away it is from the satellite by knowing
Speaker 1: how long it took the message to travel from the
Speaker 1: satellite to the receiver. These pulses are traveling at the
Speaker 1: speed of light, so we actually do know the velocity
Speaker 1: or the speed rather of those signals. So we've got
Speaker 1: time and we've got speed. We need to figure out
Speaker 1: the distance to know how far the receiver is from
Speaker 1: the specific satellite, and we can eliminate all the positions
Speaker 1: that aren't on Earth. Right once we figure out, oh,
Speaker 1: it took x amount of time to get here, that
Speaker 1: means where why number of miles away from the satellite
Speaker 1: we happen to know where the satellite is located, you
Speaker 1: could create a sphere representing all the points around the
Speaker 1: satellite that are the proper distance away. A lot of
Speaker 1: those points are going to be out in space. We
Speaker 1: can disregard those because obviously we're not in outer space.
Speaker 1: But for the ones that are on Earth, there's going
Speaker 1: to be a lot, right, Some are going to actually
Speaker 1: extend into the Earth. We can probably dismiss those as well.
Speaker 1: So we're just looking at the ones that actually intersect
Speaker 1: with the surface of the Earth. But there's still a lot,
Speaker 1: so we have to narrow it down. We do that
Speaker 1: by receiving multiple signals from multiple satellites, preferably for satellites
Speaker 1: to really get rid of any ambiguity. If the receiver
Speaker 1: does this with at least three but typically four satellites.
Speaker 1: Then it can pinpoint where on the surface of the
Speaker 1: Earth the receiver happens to be. It's a clever way
Speaker 1: to figure out locations because once we do figure out all, right,
Speaker 1: where why number of miles from satellite A, where Z
Speaker 1: number of miles from satellite B, where AA number of
Speaker 1: miles or satellite three and BB from satellite four, you
Speaker 1: create the spheres around all four of those satellites. You
Speaker 1: know where they are, they've told you where they are.
Speaker 1: You know what time stamps you're looking at. The time
Speaker 1: stamps also need to be in sync with the receiver's clock,
Speaker 1: but the receiver's clock can be modified here on Earth.
Speaker 1: We don't have to worry about the satellites doing that,
Speaker 1: and collectively that will end up giving you a single
Speaker 1: location where it's the only place on the surface of
Speaker 1: the Earth where all of those points of data converge.
Speaker 1: And that's how GPS works. So the scientists work fed
Speaker 1: nicely into work that was already being done at the
Speaker 1: US Naval Center for Space Technology, where other brilliant people
Speaker 1: were hard at work developing atomic clocks. So let's talk
Speaker 1: about that for a second too, because this timekeeping element
Speaker 1: is absolutely vital for navigation purposes. Remember, all of our
Speaker 1: navigation calculations are based upon how far we are from
Speaker 1: these satellites. But if the timekeeping is off, then our
Speaker 1: distance is going to be off, which means we're going
Speaker 1: to think we're somewhere else on the surface of the
Speaker 1: Earth and where we actually are. So let's take quartz
Speaker 1: based risk watches as sort of a starting point. Quarts
Speaker 1: will vibrate physically when subjected to a voltage. This relates
Speaker 1: to piezo electricity, which is the ability for certain materials
Speaker 1: like quartz to store an electric charge in response to
Speaker 1: mechanical force that's been applied to that substance. In other words,
Speaker 1: like if you'll whack quartz, it'll build up an electric charge.
Speaker 1: But the other effect can also be true. Certain materials,
Speaker 1: when exposed to an electric field, will produce physical vibrations,
Speaker 1: and quartz is one of those materials. What's more, it
Speaker 1: will always produce the same frequency of vibrations in response
Speaker 1: to specific applied voltage. So if you apply the same
Speaker 1: voltage over and over, is going to vibrate at the
Speaker 1: same frequency over and over. It does not vary, at
Speaker 1: least not for the purposes of wristwatches. As it turns out,
Speaker 1: for the purposes of space navigation, it's not nearly precise enough.
Speaker 1: But if you apply specific voltage to a quartz crystal,
Speaker 1: the crystal will produce a vibration of a specific frequency,
Speaker 1: which you can then use as if it were the
Speaker 1: swinging pendulum of an old timey grandfather clock, and you
Speaker 1: can calculate the passage of time by the frequency of vibrations.
Speaker 1: If you know that it takes twenty thousand vibrations per second,
Speaker 1: then once you hit twenty thousand, you know a second
Speaker 1: has passed. That's essentially how it works. Now, atomic clocks
Speaker 1: are not that different, but there are many orders of
Speaker 1: magnitude far more precise. So quartz crystals are consistent enough
Speaker 1: for our earthly needs, but when it comes to space operations,
Speaker 1: we need much more stability and much more accuracy. A
Speaker 1: quartz space clock will gradually start to drift and start
Speaker 1: to lose accuracy over time. Now, it typically takes a while.
Speaker 1: It might be more than a month before the clock
Speaker 1: is off by so much as a millisecond, but that
Speaker 1: would still be enough to provide extremely wrong navigational information.
Speaker 1: So imagine you're looking at your GPS app and you
Speaker 1: are flabbric acid because according to the app, you are
Speaker 1: like two hundred miles away from you where you actually are.
Speaker 1: And it's all because the receiver would be depending upon
Speaker 1: the wrong information, that time code would be wrong, and
Speaker 1: that would mean that it would be calculating the wrong distance.
Speaker 1: So yeah, a small error in space translates into an
Speaker 1: enormous error when you get to navigation systems on Earth.
Speaker 1: So atomic clocks rely upon oscillations of atomic energy states.
Speaker 1: Like think of electron energy states. You probably know atoms
Speaker 1: are made up of a nucleus around which are orbiting electrons.
Speaker 1: These electrons in habit various energy states. If you pour
Speaker 1: energy into an atom, you can make an electron go
Speaker 1: move out to a higher energy state, and then once
Speaker 1: you stop pouring energy in, the electron will naturally move
Speaker 1: back down to its normal energy state. So this can
Speaker 1: be an oscillation. Now to go into this further, to
Speaker 1: really dive into it, would get far too complicated for
Speaker 1: this episode. But the important thing to remember is that
Speaker 1: atomic clocks are both more stable and more accurate than
Speaker 1: quartz crystal based time pieces. Depending on the type of
Speaker 1: atom being used, the clock might count billions of oscillations
Speaker 1: per second, like more than nine billion, So you're really
Speaker 1: dividing a second down into unfathomably small units of time
Speaker 1: by looking at the frequency of these oscillations. This is
Speaker 1: an incredible level of accuracy, which is a necessary component
Speaker 1: when we're talking about navigation. But I also promise y'
Speaker 1: all some relativity up here in this podcast. So what
Speaker 1: does that have to do with anything, Well, Einstein's theories
Speaker 1: of relativity. Both of these special relativity and general relativity
Speaker 1: varieties have something to say about the passage of time.
Speaker 1: It's all relative, you see. And some factors that determine
Speaker 1: the speed at which time passes for a subject relative
Speaker 1: to an outside observer includes stuff like gravity and speed. Now,
Speaker 1: let's get one thing out of the way first, because
Speaker 1: this gets whibbly wobbly timey. Whymy, Like, you wouldn't believe
Speaker 1: the passage of time to an observer like their own sense,
Speaker 1: their own sensation of the passage of time, that doesn't change.
Speaker 1: To them. Time continues on as it would in any
Speaker 1: other condition. It's only as they observe outside points of
Speaker 1: reference that the sense of time changes. So like, for example,
Speaker 1: one thing is that the faster you go, the slower
Speaker 1: time moves for you relative to an outside observer. So
Speaker 1: if you're in a ship and you're going super super
Speaker 1: super fast, it would feel like time is passing as normal.
Speaker 1: To someone outside of the spaceship here on Earth, it
Speaker 1: would look like you were moving in slow motion. If
Speaker 1: they could magically see you inside this ship, even though
Speaker 1: the ship is moving super fast, you would appear to
Speaker 1: be moving at a crawl. And that's why at the
Speaker 1: end of your journey, when you would get off your spaceship,
Speaker 1: your friends and family who had stayed behind on Earth
Speaker 1: would have all aged much more than you did, because
Speaker 1: relative to them, time passed more slowly. For you. Your experience, however,
Speaker 1: was that time just continued on as it always has,
Speaker 1: very very mind binding kind of stuff. Right, But what
Speaker 1: does this have to do with satellites. Well, let's talk
Speaker 1: about general relativity first. It explains that gravity can alter
Speaker 1: time such that a satellite that's in orbit around Earth
Speaker 1: will have clocks that are running a little bit faster
Speaker 1: than they would if they were just on Earth. And
Speaker 1: by a little bit faster, I'm talking about like forty
Speaker 1: five microseconds per day drifting right, like they're getting ahead
Speaker 1: by about forty five microseconds per day. However, we also
Speaker 1: have special relativity. This says that because the satellites are
Speaker 1: whizzing through space pretty darn fast, the clocks run a
Speaker 1: little more slowly relative to the ones on Earth, and
Speaker 1: they end up losing about seven microseconds per day. So
Speaker 1: you've got to factor both of these in. Right, you're
Speaker 1: gaining forty five microseconds on one side and losing seven
Speaker 1: microseconds on the other side. But this means that we
Speaker 1: have to send up clock modifications corrections to the satellite's
Speaker 1: clocks in order to adjust them and make sure they
Speaker 1: don't drift too much over time, because the longer they
Speaker 1: do so without a correction, the more inaccurate the results
Speaker 1: are going to be here on Earth when we're depending
Speaker 1: upon them for navigation. All right, let's get back to
Speaker 1: our history. So in the late nineteen seventies, a US
Speaker 1: military GPS constellation was slowly taking shape, and initially it
Speaker 1: was called Navstar. And this project took the work that
Speaker 1: was being done independently in the Army, the Navy, and
Speaker 1: the Air Force and kind of brought all that learning
Speaker 1: together and became a really massive nationwide effort and eventually
Speaker 1: it would evolve into what we just referred to as
Speaker 1: GPS these days. The first fully operational satellite in the
Speaker 1: GPS constellation would finally launch in nineteen eighty nine. So yeah,
Speaker 1: this was a system that was in development for like
Speaker 1: two decades pretty much, and then finally in nineteen eighty nine,
Speaker 1: the first satellite goes up. And that's just one. You
Speaker 1: can't navigate just on one satellite, at least not using
Speaker 1: this trilateration approach. But meanwhile, manufacturers here on Terra Firma
Speaker 1: were busy building the navigation devices that would be reliant
Speaker 1: upon these satellites once there were more up in orbit,
Speaker 1: and this would include handheld navigation units. The constellation of
Speaker 1: GPS satellites wouldn't reach what old Emperor Palpatine would consider
Speaker 1: fully operational until nineteen ninety five. The military would end
Speaker 1: up receiving clear signals for the purposes of navigation. So
Speaker 1: if you were using GPS and you were in the
Speaker 1: military and you were using it officially, you would get
Speaker 1: really accurate results. However, the same was not true for
Speaker 1: everybody else. The rest of us got something that was
Speaker 1: called selective availability. I mentioned that at the top of
Speaker 1: this episode. So essentially for civilian use, the satellites were
Speaker 1: fudging the timecode just a tiny, tiny amount in those
Speaker 1: data pulses. Now, it wasn't fudging the timecode enough to
Speaker 1: put you well outside where you actually were and make
Speaker 1: it totally useless, but it was enough to muddle the
Speaker 1: accuracy to within maybe one hundred meters of your actual location.
Speaker 1: So you could still use GPS for general navigation, but
Speaker 1: it wouldn't be suitable for stuff like turn by turn
Speaker 1: directions because the muddled data would not be accurate to
Speaker 1: your real location. So why was this Well, it was
Speaker 1: to protect stuff like military bases and that sort of thing.
Speaker 1: The thought was that the information was potentially too dangerous
Speaker 1: to be made public. This would hold true until two thousand,
Speaker 1: when former President Bill Clinton rescinded select availability. At that point,
Speaker 1: GPS receivers could display accurate information to within a couple
Speaker 1: of meters of a person's actual location on the Earth,
Speaker 1: and this would improve over time, and this is when
Speaker 1: turn by turn directions will become a possibility for civilian use.
Speaker 1: Now today there are more than thirty satellites that are
Speaker 1: part of the GPS constellation. They are frequently updated where
Speaker 1: you know, a newer generation of tech satellite will go
Speaker 1: up and replace ones that are no longer in service
Speaker 1: or have stopped working, and our capabilities improve with each generation.
Speaker 1: The United States is also not the only nation to
Speaker 1: operate a global satellite based navigation system. Russia has an
Speaker 1: alternative to GPS. It's called Glonas GLO NASS. Receivers that
Speaker 1: can work with both GPS and clonos are typically more
Speaker 1: reliable because they can more easily receive signals from, at
Speaker 1: least for satellites, like even if you're a place that
Speaker 1: has lots of tall buildings that might block signals, you
Speaker 1: have a lot more satellites up there that you could
Speaker 1: potentially pull from and thus get a better reading on
Speaker 1: where you are, so you can get devices that are
Speaker 1: compliant with both GPS and GLONAS. Glonas initially completed its
Speaker 1: constellation in nineteen ninety five, the same year that the
Speaker 1: GPS constellation went fully operational, but budget cuts in Russia
Speaker 1: led to degradation of the constellation. It lost some of
Speaker 1: its capability, and eventually Russia was able to reinvest and
Speaker 1: in twenty eleven they were able to bring a full
Speaker 1: constellation back online. It's been pretty much that way ever since. Again,
Speaker 1: like the United States, Russia has also upgraded individual satellites
Speaker 1: in the constellation in order to provide better service. So
Speaker 1: that's it. That's kind of how GPS works. It's really
Speaker 1: all about figuring out where you are based on how
Speaker 1: long it took satellites to send you a little data message.
Speaker 1: You know, it's pretty cool, I think. I think it's
Speaker 1: a really intriguing way to figure out your location. It's
Speaker 1: so clever because it's not relying on things like landmarks
Speaker 1: or anything like that. Not the way that people like
Speaker 1: myself typically navigate, right. I navigate through landmarks and street
Speaker 1: names and that kind of stuff. Occasionally I will reorient
Speaker 1: myself based upon which where the sun is, because I
Speaker 1: know enough to know if it's before noon, the sun's
Speaker 1: in the eastern part of the sky, and if it's afternoon,
Speaker 1: it's in the western part of the sky. Once you
Speaker 1: get past that, all bets are off. I was never
Speaker 1: that good of a boy scout, but yeah, GPS is
Speaker 1: really truly revolutionized travel beyond what I can even express. Like,
Speaker 1: it's hard to communicate to people who have never lived
Speaker 1: without GPS what it was like to try and get around,
Speaker 1: like to have an atlass in your car and you know,
Speaker 1: rely on on paper maps or like in the old,
Speaker 1: the old days of things like map quest, you would
Speaker 1: find turn by turn directions on your computer and then
Speaker 1: print them out or write them down because smartphones weren't
Speaker 1: really a thing yet, so you need to have a
Speaker 1: way to actually carry the directions with you. It's a
Speaker 1: different world these days, but still pretty cool. Like I think,
Speaker 1: it's a neat thing to know that this system works
Speaker 1: in this way. It's also important, by the way, to
Speaker 1: learn how to read maps, because you never know. If
Speaker 1: stuff goes down for whatever reason, you want to be
Speaker 1: able to still get around, like things like solar flares
Speaker 1: coronal mass ejections. These big solar events can sometimes wipe
Speaker 1: out stuff or at least shut things down temporarily, and
Speaker 1: if in the process of that you still need to
Speaker 1: get around, knowing how to read a map can be
Speaker 1: really useful, so it's a skill I recommend developing. That's
Speaker 1: it for this episode. I hope you are all well.
Speaker 1: I hope those of you who have fun trips planned
Speaker 1: in the future can take a moment to appreciate the
Speaker 1: beauty and utility of GPS, and how amazing it is
Speaker 1: that we're using things like theory of relativity and space
Speaker 1: technology just so that you know where you need to
Speaker 1: turn to go to the next in and out burger.
Speaker 1: I think that's pretty cool and I will talk to
Speaker 1: you again really soon. Tech Stuff is an iHeartRadio production.
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Speaker 1: or wherever you listen to your favorite shows.