TechStuff Classic: How Satellites Work

is something that's in orbit around another object. And of course Earth has had a satellite for billions of years. That would be the Moon. That's a natural satellite. But if we want to look at man made satellites, we have to go back a few decades. And in fact, the foundation for man made satellites, the principles, the idea of what would be required go act well before the space race ever started. That would be Isaac Newton who came up with the idea of what would be required

to create a satellite. Now that's not what he necessarily called it, but this was published in a famous thought experiment back in seventeen twenty nine, and at the time he was really concentrating on gravity, which is pretty heavy stuff. So Newton's thought experiment was famous. People have talked about

this a lot. You've probably heard about it. He said, what if you were to go at the top of a really really tall mountain and you build a cannon on the top of that mountain, and you aim that cannon so that the barrel is parallel with the earth below you, so it's at at the same you know, same angle as the ground down at the base of the mountain. You fire the cannon, the cannon ball flies out and it moves away from the cannon, and but it also starts to fall because gravity has been pulling

on the cannonball the whole time. You know, gravity was pulling on the cannonball when it was in the cannon. It's pulling on the cannonball now that it's emerged from the cannon. Eventually, this cannonball is going to fall to the ground. And by eventually, it's it's based upon the altitude that the cannonball already is at. Uh doesn't have anything to do with the forward velocity so much as

the altitude. He said, well, what if you were to to pack more gunpowder in this cannon and you fire it, might it will go further because it's moving out a forward velocity. That's that's greater than the previous one, but it still will eventually fall to the earth. Uh really in that same amount of time. It's just gonna be

further out from their first shot. But then you keep packing more and more gunpowder in, and eventually you pack enough gunpowder in so that when you fire the cannonball, it is flying out at a forward velocity at a at a rate that is equal to how the Earth

is curving a way from the cannonball. So, in other words, the canniballs falling toward the Earth, but the Earth is curving away from the cannonball at that same rate, so the cannibal never falls down to hit the Earth's surface because the Earth is falling away from the cannonball at the same rate that the cannonball itself is falling. This would mean that eventually you would shoot yourself in the back, because the cannonball would make a full rotation around the

Earth and come back to its point of origin. At least, that was the thought experiment that Newton had proposed, which seemed like a really clever idea, but there was no practical means of testing it or putting it to any use back in Newton's day, it was just an interesting idea. It would not be until October four, nineteen seven, and that's when the then Soviet Union made history by launching the first man made satellite into Earth orbit, and that

satellite was the spot Nick one. But it was fairly simple. It was a ball all that was silver in color. It was about twenty two point eight inches in diameter, which is around fifty eight centimeters, so not very big, and it weighed a hundred eighty three point nine pounds or eighty three point six ms. The body was made out of an aluminum alloy, and the shell of that aluminum was just two millimeters thick. It was actually two hemispheres of a globe that were connected together by thirty

six bolts around the circumference of those hemispheres. It had two antennas, and each antenna had two beams, so like four prongs extending backward from the scent from the sphere itself, almost like it had four legs. One pair of antenna where seven point nine feet long or about two point four meters. The other pair was twelve point eight feet long or three point nine meters. Inside the satellite. There wasn't a whole lot, not compared to what had originally

been planned to put in the satellite. Inside it was a radio transmitter so it could communicate back to Earth, had three silver zinc batteries that would provide power. It had a couple of different switches inside of it, remote switches, a thermal system fan was in there, a controlled thermal switch, and a barrel metric switch. We're in there. So and

it was also filled with nitrogen gas to create internal pressure. Essentially, the only things this this was really the only thing this this um satellite could do was monitor its own systems like how hot was it or cold was it? What was the pressure like, and then it would beam down information in a series of beeps. In fact, my former co host Chris Palette used to refer to spot Nick as the thing what beeps. It actually sounded a

bit like this. So if you had had a Ham radio back in nine and you were tuning in, you could actually pick up that signal as sput Nick passed overhead because it was broadcasting on a frequency that was within the citizen band radio frequency, and that meant that people could actually listen in as sput Nick went overhead. It only took ninety eight minutes for the satellite to go around the Earth, so every hour and a half or so you would be able to pick this up.

And it freaked people out, particularly in the United States. People were freaking out because they were able to actually hear evidence of the Soviet Union's ability to send an

object into space. And if they could do that, there was also the fear that they could perhaps fire a ballistic missile, maybe with a nuclear warhead, at the United States that they had had now had the capability to fire massive destructive weapons at the US from a world away, and at this time the Cold War was going on strong. So it caused more than a little stir. It was

the fuel for tons of different science fiction films. Uh, They're all these different U instructional movies that explained what you need to do in the case of a nuclear war, and most of them were freakishly optimistic. At any rate, it propelled the United States into a new era of research and development. The US had already been planning on getting into the space race, but this meant that suddenly everything was cranked up to eleven, as spinal tap would say.

So it really literally launched the space race between the United States and the Soviet Union. Now, for the story of spot Nick itself, you actually have to go back much further back to the nineteen forties in fact, or even earlier, when you're looking at the the rocket program out of the Soviet Union during World War Two. So officially you would argue that nineteen fifty two was was

what got Sputnik itself going. Within the Soviet Union, that's what an organization called the International Council of Scientific Unions called for artificial satellites to be launched in order to study solar activity, which was going to be reaching a peak in nineteen fifty eight, and the United States started planning a launch at least as far back as nineteen fifty five, and their project was called Vanguard, and pretty much the world was looking at the United States as

the leader. It was going to be the US that would be launching a satellite sometime around the summer of nineteen fifty seven. But the Soviet Union thought, hey, we have the opportunity to show up our rival, and so they really put Sputnik on the fast track now to to look at what was going on in the Soviet Union. Going back to the nineties, there was a man named Mikhail tiken Revov. I'm gonna mess up that name all the time. Tick Hanravov who led a team of scientists

to design, build, and launch spot Nick one. But their early work was really looking at missile systems, ballistic missile missile systems for military use. Uh, they just saw the potential for using those same systems to launch satellite into space. And they were really looking at the possibility of using multi stage rockets in order to get the right amount of acceleration to push an object into orbit. And they were often relying on research performed not just by their team,

but by other scientific teams around the world. Often this was information that we're that was pulled in through espionage. It wasn't necessarily the scientific community openly sharing this information. And originally, uh, they were really looking at how can

we make missiles better missiles for the Soviet Union. The group would form in nineteen forty six, so not long after the end of World War Two, and the team worked on satellite plans pretty much in secret because they weren't sure if the Soviet government would actually appreciate their interest in scientific research that did not have an immediate

military application. Now, keep in mind that until nineteen fifty three, the Soviet Union was being led by Joseph Stalin, and he was an incredibly brutal dictator, and paranoia was rampant in the Soviet Union. There were stories about secret police and kidnappings in the middle of the night. People lived in constant fear of being arrested or executed. But after Stalin died in March ninette, people were able to concentrate

on something beyond just not being noticed. It's hard to imagine how terrifying that time must have been, but it's probably no coincidence that it was nineteen fifty for when the Soviet scientists stopped hiding the fact that they were performing this satellite research. They would talk about it openly, and the project received support from various scientific societies within the USSR, but it wouldn't be until nineteen fifty six

that they received official approval from the Kremlin. So if you want to hear a really amazing story about bureaucracy, science, politics, and how messed up everything was in the Soviet Union in the nineteen fifties, you should really research the full story of spot Nik because it's amazing that this project

ever really got a lot of of support. In large part the support was coming from the Soviet Union wanting to demonstrate its power, not to pursue science, but in order to show the rest of the world we're the big bear, don't mess with us. There were a whole bunch of different departments. It all worked on the design of the spot Nick project, and it's kind of interesting to see how diverse this group was. So those those different departments included the Academy of Sciences of USSR, which

oversaw the scientific research and development of the project. There was the organization Okay b DASH one, which was the u s s R Experimental Design Bureau. It's essentially was the equivalent of our DARPA here in the United States. It was a research and development program that really took big risks to see if they could find big reward from scientific research implemented in practical ways. That particularly, that particular department fell under the direction of the Ministry of

Defense Industry. So that group was responsible for designing the body of the satellite, and in the Satellite biz we referred to this as the bus. The bus is essentially the the body or shell inside which all the instrumentation exists apart from you know, some instrumentation obviously has to be on the outside of the bus, like any sort of imagery or antenna, but you get what I mean. Next, we have the Ministry of Radio Industry. They were in

charge of flight control systems, radio and telemetry systems. Then you had the Ministry of ship Building. The ship Building Ministry was responsible for designing the gyroscopes that would go in the satellite. You had the Ministry of Machine Building. They were responsible for ground processing, transport, fueling, and launch hardware. You had the Ministry of Defense itself which was in

charge of launch operations. You had the Ministry of Avia Aviation Industry which was in charge of the tracking systems, and the Special Committee of the Soviet of Ministers, which were all about the management and coordination of the program overall. Now, originally spot NICK was referred to as Object D and it was supposed to be a much larger, much more sophisticated satellite. It was not supposed to just be the

thing what beeps. It was supposed to have a lot of instrumentation for actual scientific study, with a collection of useful instruments but the projects suffered several setbacks in the design process that kept pushing back when they would be able to launch, and there was a growing concern that the United States was going to be able to launch a satellite in orbit starting on July first nine. So they had a new goal. They wanted to strip down their ideas to just the most essential elements to try

and beat America to the punch, and they did. They were able to create a much smaller, more basic satellite and they were able to launch it before the United States could send their own satellite into space, and they set a precedent, and in fact, only did the USSR beat the USA, they did it twice. We'll be back with more of this classic episode about how satellites work

after this quick break. The second satellite, which was Sputnik two, contained the first life form sent into Earth orbit, and that was the dog named Lyca, and Likeca, was always destined to die during this mission. There was no plan for Lyca to return to Earth safely. Uhlica was going to die inside the satellite, either by starvation or thirst. It was just no or suffocation that was just known that this was a one way trip for the dog. Um, the dog likely died due to overheating fairly early in

the mission based upon what the instrumentation was saying. And there have been a lot of web comics, cartoons and an amazing song. More than one song, but there's a great song called Space Doggedy which was written by Jonathan Colton and obviously has uh a lot of influence from Space Oddity from David Bowie Space Oddity in there. Space Doggy great song. There's actually a video on YouTube someone's put together with actual footage of like a from spot

Nick two. And that's all I'm going to say about that, because otherwise I'm gonna get all choked up because to me, it's a very sad story and necessary story. I totally understand why we need to use animals to test the systems, because clearly you can't just put a human in there and hope everything turns out all right. But it's still a very sad story to me because I'm I'm a squishy dog lover. I have a dog, and I when I look at my dog and imagine what Lica was

going through, I just fall to pieces. At any rate, the United States response to sput Nick was to go back to the drawing board. They had their Vanguard design mind that they had planned to launch, but that now felt that it was no longer a strong enough offering. They needed to come up with a better satellite to really be a good response to the Soviet Union's project. So the new USA project was called Explorer, and it was led by a rocket scientist named Werner von Brown.

Von Brown was a brilliant physicist, a very intelligent rockets scientist, but he had an incredibly dark past. UH. He was born in Germany in nineteen twelve and he was part of the Rocket Society as early as nineteen twenty nine. As the Nazis gained power in Germany during the thirties, Von Brown chose to work for the German Army to

develop missiles. He wanted to continue his research and work, and it seemed like the UH the most opportune place, and his work was instrumental in the development of the V two ballistic missile, which was a tool the Nazis used to some effect, perhaps not as great as it could have been, but certainly was a destructive weapon that caused a lot of damage and death. He was eventually awarded an honorary rank in the s S by Heinrich Himmler.

It is said, however, that von Brown only accepted that rank because he and his team were worried that Himmler would be angry if he had declined it. So at least some accounts state that von Brown didn't share the political ideology of the Nazis. He just saw this as the opportunity for him to actually do his work, and if he didn't join the Nazis then he would not be able to do his work. Von Brown realized that

Germany would lose the war. I think a lot of people realized that it was getting to a point where it was deniable, and so he made plans to surrender himself and his team of around five rockets scientists to the Allies and offered to do research for the United

States to help them develop their ballistic missiles. Further So, Fan Brown and his scientists would create a rocket research center that originally fell under the guidance of the United States Army, but eventually it would get shifted to a new organization called NASA, which was founded mainly in reaction to spot Nick and really be part of the space race. Explorer one would launch on January thirty one, nineteen eight, and it made an actual scientific discovery on its orbital flight.

It discovered magnetic radiation belts around the Earth, which are now called the Van Allen Belt after one of the lead researcher on the project. Now, these days, satellites are way more sophisticated than spot Nick or even Explorer one, and they typically use solar panels to capture solar energy and convert it into electricity that's used to charge batteries

for power. Some of them actually use fuel cells rather than batteries to generate electricity, And we've used nuclear power in some probes that we've sent away from our planet, but in general we tend to be a bit skittish about the idea of putting nuclear power into stuff that's going to be orbiting our own planet. Satellites tend to have some pretty sophisticated stuff inside them these days, like computer control systems, which were well beyond the abilities of

the early satellites which had electro mechanical controls. But now we've got computer control systems, radio communications, attitude control systems. Attitude in this case isn't about personality, but rather the satellites orientation with respect to the position of the Earth, and satellites can have different shaped orbits. Some have circular or bits, which are very regular and uh and predictable,

but some have elliptical orbits. And elliptical orbits are interesting because a satellite will travel at different speeds along its orbital path. So there are two points along that path that we call the foci of the elliptical orbit. The point that's closest to the planet is the parage, and that's the point at which the satellite will be moving fastest through its orbit. It's like think of it like the sling shot effect. The furthest point from a planet.

The furthest point in the orbit the satellite's orbit from a planet is the apogee, and that's where the satellite will move the slowest in its orbital path. Now, launching a satellite into orbit obviously requires rockets, and in a rocket launch, a special system is used called the inertial guidance system, which calculates the adjustments needed to push a satellite into the correct orbit. I'll talk about the different

orbits in a second. Typically, rockets are fired so that they head eastward, and that means that the Earth's rotation gives those rockets a speed boost. It's like the rockets are actually flying faster than they really are because of the relative motion of the Earth. If you were to launch your rocket at the equator, you would get the biggest boost because the Earth bulge is out there. It's the largest diameter. So here's how you would determine the

boost you get to your speed. You take the Earth's circumference, which is about two thousand, nine hundred miles or forty thousand sixty kilometers. You figure out how fast the Earth rotates, which is one full rotation in approximately twenty four hours, which gives us a speed of around one thousand, thirty eight miles per hour or one thousand, six hundred sixty nine kilometers per hour. That's the rotational speed of the Earth.

That's typically that's actually at the equator. If you were to look at a launch facility at Cape Canaveral, the rotational speed is different because you're further north of the equator. You're not at the thickest part of the Earth. Uh Therefore, the circumference is smaller and you have a slower speed, So a slower rotational speed at that point so it's closer to around eight miles per hour or one thousand, four hundred forty kilometers per hour, but that speed boost

gives us a big help. So to get the satellite into orbit, you have to be going wicked fast, but not as fast as what you would need to actually escape Earth's gravity. So if you wanted to go out into space and beyond Earth's gravity, you're leaving Earth orbit, you're heading out to Mars or something. You would have to accelerate to at least twenty five thousand, thirty nine miles per hour or forty kilometers per hour to escape

Earth's gravity and enter outer space. Putting a satellite in orbit requires less speed, and it all depends upon which orbit you're trying to insert the satellite into. The orbits determine the speed, so lower orbits require faster speeds, which might seem counter and tuitive at first, but you gotta remember those lower orbits that that speed is meant to counteract the gravitational pull of Earth so that the object in orbit remains in orbit doesn't get pulled back down

to the ground. So when you're closer to Earth, the force of gravity is greater, as you probably Remember, gravity is dependent upon two things, the mass of two objects and their relative distance to one another. So as distance increases gravitation, gravitational pull decreases, and you don't need to counteract that with more velocity to make sure an object stays within its orbital path and doesn't deteriorate and fall

into the Earth. So higher orbits require lower speeds, and if you get far enough out there, you can have a satellite that orbits at the same speed as Earth's rotation. Uh, those would be geostationary orbits. They would appear to be directly above a fixed point on the Earth and they would not move from that point. I'll get into that more just a second. First, let's talk about the various types of orbits from an altitude, because we can describe

orbits in different ways. You can describe their orbital pathway whether it's circular or elliptical. You can describe it in its altitude, and you can describe it in its orientation as in is it equatorial, is it directly above the equator? Is there any degree of inclination? Um? Is it a polar orbit which goes north south not east west? Lots of different ways to describe them. So from an altitude perspective,

we start with lower orbit. That's the one closest end to the Earth, and that's an a range that's between a hundred eleven miles and one thousand, two hundred three miles above the surface of the Earth. In kilometers, I would be a hundred eighty to two thousand uh. This tends to be the altitude we use for satellites that collects surface observations, photography, weather satellites, that kind of thing.

When you go further out, you get to medium Earth orbit that's in a zone the between one thousand, two hundred forty three miles and twenty two thousand, two hundred twenty three miles or in kilometers way easier two thousand to thirty six thousand kilometers. Navigation satellites like GPS tend to be at this altitude, although summer at higher altitudes.

Then you get to geosynchronous orbit. That's when you are at an altitude that's greater than twenty two thousand, twenty three miles, in other words, greater than thirty six thousand kilometers. The orbital period is the same as the Earth's rotational period, meaning it takes a full day for the satellite to

go all the way around the Earth. There are is a subset of geosynchronous satellites called geo stationary satellites, So all geostationary satellites are also geosynchronous, but not all geosynchronous satellites are geo stationary. If you have a geostationary satellite, that's one of those satellites that remains over a fixed position on the Earth's surface, So you could build and enter at that point pointed straight up into the atmosphere, and it's going to be aimed directly at that satellite.

And as long as nothing changes in that satellite's orbit. Things do change over time, so you have to correct it occasionally, but as long as nothing changes, uh, the antenna and satellite will always be in alignment. That's a geostationary satellite. Uh. It doesn't matter if it's day or night. You're always going to have a direct line of sight between the antenna and the satellite, and the satellite is gonna be too far away from you to see it, but there's a direct line of site as far as

the antenna is concerned. All geostationary satellites are geosynchronous. Like I said, But if the opposite isn't true, what's going on? How are geo secret as satellites that aren't geostationary. How does that work? Well, the geosynchronous satellite does make one orbit around the Earth in the same amount of time it takes Earth to make one rotation in inertial or fixed space, which is also called a sidereal day. It's

actually not twenty four hours. Specifically, it is twenty three hours, fifty six minutes and four seconds of mean solar time. You've got a bit more to say about how satellites work, but before we get to that, we need to take another quick break. If the satellite has any inclination or a non circular orbital path, it will not be geo stationary. The satellite will appear to roam over the Earth's surface, so in elliptical orbits, those egg shaped orbits, the satellite

would be moving at different speeds along its journey. Remember the paragean apogee, It's going to be moving it at different velocities as it goes around the Earth. Inclination, by the way, is the angle between a reference plane and the orbital plane. The reference plane in this case, Uh, we're talking specifically about the equator. So imagine you've got the Earth globe, you've got it tilted at a slight angle because the axis is on an angle, and you've

got the equator. If you have a geosynchronous satellite directly above the equator, it's going to be geo stationary. It's going to stay around that fixed point. But if you go north or south of the equator and you place a satellite there, it will it will not stay above a fixed point. Its orbit is going to be slightly angled. That's the inclination we would talk about. UH, So as it would go around the pathway, uh, it would actually

roam over the surface of the Earth. So a satellite that has degrees of inclination and its orbit with respect to the equator will move north and south of the equator as it completes an orbit. So this satellite is going to stay more or less in the same east west area, but it's going to go north south as it goes throughout its orbit. Satellites with an elliptical path will drift east and west for any fixed point on the Earth. As a satellite moves faster or slower through

its Earth orbit. We have seen There are several satellites that use this where they are both a inclination and an elliptical path, so they make this almost like a figure eight kind of pattern over a general region of the Earth's surface, which could be really useful for things like communication satellites or or even GPS in that In that sense, there are some GPS satellites that work under this principle. Geo stationary satellites have a view of about

of the Earth's surface. Just a single geo stationary satellite can see about fort of the Earth's surface from where it is. So if you just create a network of a few geostationary satellites, you can get a view of practically the entire Earth, really everything between eighty one degree south and eighty one degrees north. Beyond those those uh those degrees, you wouldn't be able to see it from the way the Earth is curved, but you'd get to

see everything between the two. Geo stationary satellites tend to be used for communications. That's great solution for us on the ground because you don't need to move the antenna on the surface to stay in contact with the satellite. If the satellite we're drifting if it if it orbited the Earth multiple times during a rotation, you would constantly have to adjust your antenna to remain in contact with the satellite, and there will be times where you would

be out of contact with the satellite. It would have the Earth between you and the antenna. So geo stationary makes this easy because it's always going to be directly above the antenna. So it makes an ideal communication satellite in that respect. But there are a limited number of slots for geostationary satellites. You know, you could go to different altitudes, but you're going to be You're going to be stuck at that equator plane. So you don't want

satellites to collide with one another. Obviously, that would destroy or an least damage one or both satellites, and you don't want the actual data communication to interfere with each other, so you have to separate them out by space. You can't have them to pack pecked in too closely together, and a satellite geo stationary orbit will not stay there forever.

Other gravitational forces from the Sun and the Moon, plus the fact that the Earth is not perfectly round, will cause the satellites to increase in inclination over time, so they'll they'll start to drift a little bit and then they will no longer be geo stationary UH satellites. They'll have thrusters on them and fuel inside them in order to make small corrections, which is called station keeping, and that's so that they can stay in the right relative location.

But once the satellite is used up all its fuel, it will experience an increase in inclination. It's unavoidable. You can't fix it at that point, and it's possible, depending upon how the satellite is located, that it could become a hazard to other geo stationary or geosynchronous satellites. So normally at the end of a geo stationary satellites useful LIFESPAN will send a command to the satellite to say,

get the heck out of the neighborhood. Boost it at a higher altitude, a higher orbit, which moves out of the way of other satellites, because it's not gonna be useful anyway, so you might as well boost it further out and not have it become space junk closer into the Earth. There's already a lot of space junk that's out there. Fortunately, space is really big. So while there's always a threat of space junk being a problem with satellites, it's such a huge space that the odds on any

given day are fairly low of an incident. But the more stuff we send up there, the better the odds are that something bad will happen. Now, not all orbits are in an east west orientation. You're probably imagining that these satellites are orbiting the Earth more or less in the same direct shouldn't that the Earth rotates, that they are going around and around, uh, the same axis of rotation. Not all of them do. Some of them are rotating

north south, they're going around the poles. You have polar orbits, which are really good for photography and mapping because as these satellites move north to south or south and north, depending upon which way you're going, um, the Earth is rotating under the satellites, so they get a really good view of the Earth. They're great if you want to have a satellite map of a region. They're also not bad if you're hoping for satellite to pass over a certain region on the Earth so you can get a

better look. In other words, these are used for spying, and one particular type of orbit, very specific type of orbit is the mulnia or lightning orbit, and the orbit takes its name from Soviet satellites that use this particular style of orbit or communications networks. It's an elliptical shape, which means the satellite spends a lot of its time near the apoge poet point the of the orbit, because

that's where it moves the slowest. So if you plan out the telemetry of your satellite in such a way so that the apoge is over a specific region, you know that when the satellite orbits the Earth, it's gonna be spending the majority of its orbit over where the apogee is. So if you locate it in a place that you're interested in, you're gonna get more coverage of that region throughout the duration of the orbit of the satellite.

So the Soviets planned the apoge to be over the northern hemisphere so that they could serve as a communications network and maybe also you know, spy on Europe a little bit. Perhaps one thing we use satellites for is to spread a signal from one location to another, and this is a pretty simple idea. Actually, it's just bouncing a signal off of a satellite. It's amost like the satellite acts as a mirror, although it's also an amplifier.

So we use an antenna on the Earth pointed up towards the satellite we're interested in, and we beam a signal into space. It might be audio, it might be video, it could be anything really, and that antenna is the up link. Now the satellite receives this. They have it has its own antenna and receives the signal and then runs it through an amplifier and the beams the amplified signal back down to the Earth. And on Earth we have other antenna known as the down links, that receive

the incoming signal from the satellite. And using this model, we can beam all sorts of useful stuff like communication signals. Television studios would send feeds up to satellites, which then act as a distribution system. So you would have a centralized location where you would have the the video feed, video and audio feed. You would send that through an up link to a satellite. It would receive it and

beam it back down to receiving stations. And that was how you know, that's how we get television broadcast beyond just over the air broadcast. In fact, if you have a cable company, you could receive these signals yourself using satellites. Right, you could have part of the satellite TV system and you have your own little satellite that's pointed up and you receive your television signals that way. Or you could end up having cable but cable companies also use this method.

You would have a centralized location that beams a signal up, it comes down so that various cable distribution networks received the signal and then they send that through the actual cables that eventually terminate at your television. So this is a very important way of using satellites. Now, I want to conclude this episode with a quick discussion about how

relativity affects satellites, both special and general relativity. Now, these, of course are the the theories proposed by Einstein that ultimately proved true at least in the case of time dilation, because we see it in practice with satellites. One of the things we use satellites for is GPS, the Global Position System. So GPS positioning system, I should say, and

GPS is incredibly useful. That's what lets us use real time maps on our phones and GPS devices to go from point A to point B. But in order for GPS to work, it needs to be able to measure time very accurately, both for the person who's on Earth and the satellite that is providing the very satellites I should say that are providing the information that allows us to UH to triangulate where we are on the service of Earth. So here's the problem. Time dilation. Einstein's theory

gives us some uh some issues with time. Special relativity tells us that the faster we move relative to an independent observer, the slower time seems to pass for ourselves. Um again, based upon the relative observer to us, time will pass exactly the same way. No matter how fast we're going we will it will feel the same. So if you get on a spaceship that's going near the speed of light and you look at your watch, the second hand is going to take away as if you

were on Earth. But to an independent observer, it would look like that second hand is going super slow, and it would mean that when you finished your journey and came back to Earth, more time would appear to have passed on Earth than it did for you, even though for people on Earth, time was passing normally. For you on the spaceship, time was passing normally. It's really only when you have this point of reference that you realize that you've experienced different amounts of time. Uh, it's kind

of a mind bender. Well, special relativity tells us that these clocks on board the satellites will take a little more slowly because they're moving so fast out in space. They should actually fall behind the clocks here on Earth by about seven micro seconds per day, which doesn't sound like a lot, but if you're talking about very precise measurements to give you an idea of where you are

before long, that becomes an insurmountable problem. So seven micro seconds per day slower on the satellites compared to the clocks on Earth. If that were all there were to it, then we would just say, well, we have to find a way, like a program that will build in this error so that we know ahead of time how to adjust for it. But it gets more complicated than that. So that's special relativity. But general relativity also plays a part.

So one of the predictions made by general relativity is that clocks closer to a massive object will seem to take more slowly than those that are further away from a massive object. So if we look at it that way, these satellites are very far away from the surface of the Earth, so the clocks on the surface of the Earth are much closer to a massive object. The clocks on the satellites are much further away from a massive object,

and it's enough to make a big difference. It also means that the clocks on the satellites appear to be taking faster than the clocks on the ground. So if you calculate a prediction using general relativity as your basis for how fast those clocks will be ticking on the satellites, you would see that they be ahead of our ground

clocks by about forty five micro seconds per day. Now, this actually means that you have to take the difference between the forty five seconds in advance and the our forty five micro seconds I'm sorry, forty five micro seconds in advance from general relativity, and you have to act the seven micro seconds behind from special relativity. And it tells you that the clocks on board the satellites should take a little bit faster than the clocks here on

the ground. By the tune of thirty eight microseconds per day. You take those forty microseconds ahead general relativity, subtract the seven microseconds from behind from special relativity, and you get thirty eight microseconds ahead uh net. So it again is enough for it to cause a high precision system like GPS two have errors after just a few days, so you have to correct for that. You actually have to

create a navigational fix so that the system is accurate. Uh. Otherwise you would get errors in where the map would say you were. You would look at the map and as time would go by, these errors would get worse and worse, to the point where it would show you locations that are just ridiculous, you blocks away from where you actually were, and uh and more if time went on long enough. In the GPS satellite system was limited, so you're talking about you know, errors of around ten

kilometers every day. That's that's a big deal. You know, you're trying to get from point A to point B and you're getting errors that are ten kilometers off. That could be disastrous. So it would actually be useless after a very few days. That's why you have to have algorithms built in that take these relativistic effects into account so that the results you get on your GPS device

remain accurate. So I think that's pretty cool that you know, satellites are a practical way for us to see how relativity can affect us, and that relativity is in fact real. It's it's it's not it's not quote unquote just a theory. It's something that we can observe directly and though and know that this is at play. So I wanted to mention that because you know, it's it's pretty cool stuff. And honestly, when I was first looking into it years ago, when I was looking at how GPS works, I had

a handle on special relativity. I understood that the speed of the movement of the satellites would affect how time passes compared to what we see here on Earth on the surface, but I was not aware of the effects of general relativity. That was something I had to learn when I looked up GPS back in the day, which I think was a Tuesday, if I'm not mistaken, so

relatively obviously a very fascinating subject. I would love to go into further detail, but I think that's more of a stuff to blow your mind than a tech stuff topic. We have, of course touched upon RelA ativity a few times in our conversations about various types of technology. But maybe one day I'll get some stuff to blow your mind folks in here, and then we'll have a big discussion about relativity, not just what it is, but how

it directly affects some of the things we do. All right, So that wraps up this discussion about satellites, and I may do a future episode where I go into board detail about the different types of satellites, the instrumentation that is aboard these satellites, how they work, who owns them, maybe some interesting stories about notable discoveries that satellites have made and notable incidents that have happened because of satellites. I hope you enjoyed that classic episode of tech stuff

on how satellites work. I know I've talked about satellites and how they work several times since then. I often do kind of a truncated abbreviated version, if you will.

When I have to talk about stuff like Starlink, for example, which is space x is uh satellite based internet service provider and similar things, you know, I have to talk about how the satellites get into orbit, how they maintain orbit, what the different orbits mean, how satellites are able to keep track of things like making sure that you know when you're using a GPS device that you're getting accurate information instead of something that's telling you you're in a

totally different time zone. All this is incredible technology. It's really amazing stuff, and it's based off amazing ingenuity, and I'll constantly be going back and talking about it. But this is sort of the basic information about how satellites work. So I hope you enjoyed that. If you have suggestions for topics I should cover in future episodes of tech Stuff, please reach out to me. One way to do that is to download the I Heart radio app. It's free

to download. It's free to use. You can navigate over to the tech Stuff page for using the search bar. You can leave us a voicemail by clicking on the little microphone icon. Leave a message up to thirty seconds in length. If you would prefer, you can send me your message via Twitter. The handle for the show is text Stuff hs W and uh yeah. Just leave me your suggestions. Maybe it's a suggestion for a topic or

a guest. I'm always eager to see what you have to say, and I'll talk to you again really soon. Y Text Stuff is an I Heart Radio production. For more podcasts from my Heart Radio, visit the i heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.