Welcome to tech Stuff, a production from I Heart Radio. Hey there, and welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm an executive producer with I Heart Radio. And how the tech are you? You know? Ever since the then Soviet Union sent ups foot Nick way back in nineteen fifties, seven man made satellites have played a really important role in our world in multiple contexts. You know, in the early days, at least from a political standpoint, it was a lot about demonstrating scientific and engineering superiority. That was kind of what was driving the space race, at least from a financial and political standpoint, back when the US and USS are we're racing to achieve first in space. But I mean, obviously they're also important to further our scientific under standing of our world and beyond, and also to do stuff like layout communications infrastructure that would allow for global communication. And of course there are thousands of other applications and satellites are really out of this world. And yes, I also hate me for saying that, And I thought it could be a little beneficial to talk about the various orbits that satellites can inhabit and then explain the differences between those orbits and the purposes of them. And I think that's really helpful in order to understand stuff like why is the James Webb Space Telescope in an orbit that's so far out that we cannot reach it with a human crew? Right? Why is that? Or why scientists warn us about the dangers of space chunk. I mean, space is huge, so you would think the odds of any two objects colliding with one another out in space would be astronomical. Man, I'm gonna have a lot of puns in this episode. So we're gonna go through the various orbits and explain we would send certain types of satellites to one orbit versus another. And first of all, let's let's actually just talk about the word orbit. And I'm sure everyone out there has a grasp on this, but technically, what we're talking about is a curved path that causes one object to move around a second object, or two objects to move around each other due to the poll of gravity. And gravity is one of the fundamental forces of the universe. It's also the weakest one, by the way, it has practically no effect once you get down to the molecular or atomic level. Gravity is a force of attraction that exists between stuff in our universe. What has mass, right, anything that has mass experiences the effects of gravity. So technically you could say there's a gravitational attraction between every object that has mass and every other object that has mass. However, the magnitude of that attractive force is dependent upon two really important factors. One is the actual mass of the objects in question. The more mass, the greater the attraction, So to truly massive objects will have a greater attraction to one another than two very small objects. This is why when we get down to the molecular and atomic levels, gravity is is negligible. We can just ignore it. Uh. This, by the way, is also why the gravity on the Moon is so much less than the gravity on Earth. The acceleration due to gravity on the Moon is a little less than sevent of that what we'd experienced here on Earth, So the gravitational pull between say the Moon and an astronaut is much less than what that astronaut would experience while walking around on Earth. Because the Moon is less massive than the Earth, the astronaut is probably about the same. But the other factor is the distance that's between those two objects if they are really far apart, the gravitational force between them, while technically still being present, will be extremely weak. Again, if it's really really far apart, you can ignore it because it's so weak as to be you know, almost nothing. I should also add the Einstein's theory of general relativity actually dismissed the idea of gravity being an actual force. Rather, gravity is the consequence of objects with mass bending spacetime, and that gets a little difficult to envision, so let's simplify it. Imagine that you have a trampoline and then you put a pretty heavy bowling ball in the middle of that trampoline. Well, the weight of the bowling ball will cause the trampoline's surface to deform right, it will dip downward because the weight of the bowling ball. And if you were to try and roll a marble across the trampoline, then it's stead of traveling in a straight line, the marble's path would be affected by that bend in the trampoline. It would actually turn towards the dip and thus towards the bowling ball. Well, Einstein's theory stated that we're seeing that exact same effect out in the universe, except while we could describe the surface of a trampoline effectively as a two dimensional object, you know, an object that doesn't have depth to it. In space, we have to deal with three dimensions, that being spatial dimensions. I mean we also have time, which is the fourth dimension. And this gets are a bit tricky for us to visualize, or at least I find it tricky. Maybe you can do it. I can't. But yeah, when we often refer to gravity as a force, Einstein would correct us on that one and say it's not really a force. Now, with that bowling ball and marble trampoline example, we can actually understand why satellites have to work in the way that they do. So let's say you roll the marble hard enough to reach the point where the bowling ball's presence is going to cause the marble's pathway to change, But you're not rolling it so hard that the marble can make it out the other side to the opposite, you know, into the trampoline. So, in other words, the marble is unable to escape the bowling balls gravitational pull. The marble will roll down and hit the bowling ball and come to a stop it at some point. Now, if you rolled the marble really hard. It might be able to get through the deformed area of the trampoline's surface like it might have enough momentum too to navigate through the dip. But its path is still going to change, right. It's not a flat surface. It's not going to travel in a straight line. It will have a bend in its pathway. But maybe it will get all the way across the trampoline. Uh, it just won't be directly across. However, if you wanted to keep the marble so that it's constantly circling the bowling ball, well, we would have to have some way to keep the marble at just the right speed. It would need to be fast enough to counteract the marble's tendency to fall toward the bowling ball, but not be so fast as to cause the marble to continue off the pathway and eventually off the edge of the trampoline. If we could add energy to the marble consistently, we would be all set, because otherwise, the friction that the marble would encounter as it rolled across the trampoline would be enough to slow it down and it would fall towards the bowling ball. So we'd have to find a way to give the marble a little boost now and then in order for it to maintain its circular pathway around the bowling ball. So satellites in orbit around something else, whether it's our planet or some other celestial body, need to move at a speed that's fast enough to avoid falling toward whatever it is orbiting around. So out in space there aren't nearly as many factors that would slow down a satellite speed as we find here on Earth. There's very little friction or air resistance out there, So once you get a satellite in orbit, the speed the satellite has courtesy of the launch vehicle is sufficient to keep most satellites in an orbit for many years. Satellites have thrusters, and they have fuel, but those thrusters are not meant to accelerate the satellite in order for it to maintain orbital speed. Those thrusters are really used to maneuver the satellite so it can either transition from one orbit to another, go through a transfer orbit in other words, or used to move the satellite out of the pathway of potential space junk or other debris. Now, satellites and lower orbits can and do experience drag from the Earth's atmosphere, so there's actually no hard boundary for where our planet's atmosphere ends. We do have the Carmen line, which is sort of a convenient definite mission of the edge of space, but it's mainly there as a way to define it for political purposes and just to have a practical definition, because it's so nebulous again to use another pun and so vague that it's very difficult to say this is uh categorically where space begins, and the common line is at a hundred kilometers above sea level here on Earth. Now, that does not mean that there is no atmosphere beyond one kilometers in altitude. There is atmosphere beyond that limit, but it's extremely thin. Individual particles can be very far apart from each other, so it doesn't resemble the atmosphere we have here on the surface. UH. And these few particles are still enough to cause drag on lower altitude satellites, so gradually those satellite speeds will slow down enough that, um, you know, it will eventually de orbit. It will lose enough velocity and fall back to Earth unless we were to do something like if we were to move it to a different orbit than that could be enough to extend the life of the satellite, or we might even use thrusters to push the satellite out into an orbit where it'll just be dead out there in space. Now we can classify Earth satellite orbits in different ways, including their altitude. Now, we can classify Earth satellite orbits in several different ways, and I'll explain some of those ways when we come back from this break. Okay, before the break, I mentioned we can classify Earth orbits in several different ways. One of those ways is the altitude of those orbits. Generally speaking, we can split altitudes into low Earth orbit, mid Earth orbit, and high Earth orbit. The low orbit range is around one to two thousand kilometers above sea level, so these are well above the Carmen line. Obviously, remember the carbon lines at a hundred kilometers above sea level. These satellites move really wicked fast. Uh. These are satellites that orbit the Earth several times each day, so they're not orbiting the Earth in time with the Earth's rotation. They're actually going faster than the Earth's rotation. The lowest orbiting satellites are completing in orbit somewhere around minutes per orbit. That means a satellite like that could orbit the Earth around sixteen times each day. However, lower satellites are going to encounter more drag because they're gonna be hitting the occasional particle of atmosphere and their orbits will deteriorate faster than those satellites that are at a higher orbit. And these lower satellites and only be useful for a few years. So you wouldn't want anything designed for a long term mission to be in that orbit. Uh, it would it would not be able to maintain that orbit for longer than a few years. In the low Earth orbit range, we have a lot of satellites that do Earth observations, so satellites meant for Earth sciences often occupy this space. In addition, satellites like space x is Starlink network, they occupy the low Earth orbit range. There around five kilometers above sea level, so not quite in the middle of low Earth orbit range. They're actually on the lower end. And part of SpaceX's strategy for Starlink is to launch tens of thousands of satellites into that general orbit to provide global consistent coverage for Internet service and to essentially resupply those satellites as older ones are decommissioned, which is kind of a fancy way of saying, they either get e orbited as then they fall back to Earth or they're pushed into an orbit that no one is using, kind of a graveyard orbit. Now, the mid Earth orbit that ranges from two thousand kilometers above sea level up to thirty five thousand, seven hundred eighty kilometers, so a big big range here, and a lot of navigational satellites and spy satellites occupy this space. Um As out here, you can put satellites in an orbit where they stay above particular regions for a good amount of time each day. And in fact, now we need to talk about a special subset of orbits that are kind of between Mid Earth and High Earth orbits. And you probably heard terms like geosynchronous and geo stationary orbits. These orbits are just a touch further out from the mid orbits, and sometimes they even get grouped with High Earth orbits. It really just depends on whom you're talking to, UH, and it's very easy to confuse geosynchronous with geostationary. Technically, geostationary orbits are a subset of geosynchronous orbits. So at this altitude, this far out from the Earth, the satellites orbit is the same as the rotational speed of the Earth. So, in other words, the satellite maintains its relative position to the Earth throughout the full day. The satellite remains over the same general region of the Earth throughout the entirety of the day. Now we have to remember that the Earth also has a tilt to its axis, and this means that if a satellite is at this altitude but not directly over the equator, the satellite's position with reference to the Earth's surface will actually move north and south throughout the day. So it will still maintain its position with regard to longitude, that is, east and west. It's gonna remain in its same location east versus west, but it's latitudinal position north versus south that'll vary throughout the day. A geo stationary orbit is an orbit above the equator. That means there's a zero degree inclination with reference to the equator, and the satellite will remain over the same spot on the Earth's surface. But again, this only works if you are along the equator. This can get pretty congested like there's a There are a lot of reasons why you might want to put a satellite there so that it's over the same reference point on Earth throughout the day. But obviously there's a limited number of of orbits that you can put satellites in above the equator for one thing, you know, just to avoid things like communication interference, so it gets pretty tricky. Also, you you often will find countries that do have space programs getting treaties and agreement with countries that don't but are equatorial countries so that they can essentially get the rights to place a satellite above those countries. This is one of those cases where it's not just science and technology but politics that become important. And then you also have high Earth orbit was where we start to go beyond the geo stationary and geosynchronous orbits. We're talking about altitudes greater than thirty five thousand seven kilometers now way out here, you typically are talking about things like communications, satellites, um it can be other things too, but you know, you start to get limited in what useful stuff you can put out in this orbit. Oddly enough, when you go much further out you can find uh other really interesting uses like the James Webb Space Telescope. But we'll get there now. I mentioned geo stationary orbits, which requires the satellite to not only be above the mid Earth orbital age, but also over the equator ak zero inclination with reference to the equatorial plane. But we can classify other orbits by referencing inclination. For example, a polar orbit is one that passes over the North and South Pole over the course of its orbit, and this requires an inclination of ninety degrees. That is, it needs to be at a right angle with reference to the equator. And then you have sun synchronous orbits. Okay, so this gets really complicated, but I'll try and give you a very very high level view. Again. Another pun and you might want a satellite in a sun synchronous orbit to observe certain regions of the Earth, and you want the lighting of those regions to be consistent from one day to the next. Well, if you want to do that, you put a satellite in a polar sun synchronous orbit. This is an glinnation of about ninety eight degrees, so it's a little bit further out from a right angle, and a satellite in this orbit will orbit north south or depending upon your point of reference, south north around the Earth, and meanwhile the Earth is continuing to rotate east west below the satellite. Now, interestingly, the satellite's orbital path will also begin to rotate. In fact, that's actually crucial because if the orbital path did not rotate, you know, you can think of it like a hula hoop around a globe, where the hula hoop is going over the north and south pole, so it's vertical with respect to the globe. Then imagine that you would slowly twist the hula hoops so that it is actually orbiting the Earth that way as well. It's important because you have to remember the Earth is an orbit around the Sun. So in order for you to have a consistent satellite view with the same lighting over the same region each day, the orbit has to rotate, right, because the Earth is going around a circular path of the Sun. If the orbit didn't rotate, then you wouldn't have that effect of passing over the same region um at the same time of day each day. Now, the rotation of the orbit happens because the Earth is not a perfect sphere. It's a bit bigger around the equator and holy cats, I can totally relate to that. And so the equator region exerts the gravitational pull on the satellite that if no other physics were involved, would ultimately cause the satellite's orbit to drift into one that's over the equator. But due to the satellite's angular momentum, the satellites orbit doesn't tilt down to become equatorial. Instead, the whole orbit rotates. If you if you were to ever use a coin, and you've seen a coin start to do that that cool rotate thing on a table, like it's it's starting to fall, but it hasn't actually clattered flat on the table, but it's doing that thing where it's kind of rotating around, almost like a top. That's kind of what the orbit is doing. And the rotational speed of the Earth, the rotational speed of the orbit, and the period of the orbit line up so that the satellite will always pass over a specific spot on the Equator at the same time of day each day. So let's say it passes over Bogatam at three pm. Well that's gonna happen from there on out, So tomorrow it'll be overhead of Bogata at three pm, and the next day, and the next day and so on. Subsequent orbits throughout the day will have the satellite pass over different equatorial cities, like say Singapore or Nairobi, and it will always pass over those respective cities at the same time of day each day for that city. I'm not saying it will pass over Bogata, Singapore and Nairobi at three pm. That would be impossible, but that they will pass over uh those respective cities at the same time per day. And I realized that this gets really tricky to imagine. It's hard to explain without visual aids. So if you're having trouble getting a handle on polar Sun synchronous orbits, I recommend searching for videos that illustrate how they work. Also, I'm not even scratching the surface here as far as how complicated these get. If you really want to learn more, I recommend a paper by Ronald J. Bowaine, and it's titled A B C's of Sun Synchronous Orbit Mission Design. It is a really good paper that goes into the technical details. Anyway, you might wonder why we would even worry about getting that kind of information in the first place, Like what's the big deal. Why do we even care about getting a satellite out there to pass over the same part of the Earth at the same time of day each day. Well, one reason is that it helps us track changes in a region over time. This is particularly important as we examine the effects of climate change in that region. So you want as many factors to be the same in your observation so that any differences you see you can say, well, this clearly didn't show up because the satellite is passing over at a different time of day, so the lightings at a different angle instead, Uh, really reflective of actual changes that are happening on the ground. So keeping as much of your other factors consistent as possible is really important. Keeping in mind that obviously, like angles of light are going to change as the seasons change, but you know that's something you can you can factor in. Whereas like you want to be able to say, like, from one summer to the next, Oh, we've seen that, say the coastline of this region has changed dramatically, and potentially that's due to climate change. That's why you would need to have something like this so that you could draw those kind of conclusions. All Right, we've got more to say about orbits. I know it's just gonna keep on going around and around, because that's what orbits do. But before we get to that, let's take another quick break. Okay, so far, what I've described are you could essentially call them circular orbits. They don't have to be, but that's the way we typically imagine orbits, or at least the way I typically imagine an orbit is kind of like a circle around whatever body it's orbiting, so they more or less keep a a consistent distance from the the orbiting uh center, so Earth. In other words, like they would just keep a pretty consistent distance from the Earth. But orbits do not have to be perfectly circular, or even circular at all. You can have elliptical orbits, and an elliptical orbit is oval in shape, and this means that the satellite's distance from the Earth varies throughout its orbital path. That also means that the satellite's velocity will change as it orbits the Earth. So as the satellite is moving toward the Earth, its velocity will start to increase due to the Earth's gravitational pull, and as it moves away from the Earth, its velocity begins to slow down again because the Earth's gravity is pulling back on it. Now the low point of the orbit, so the part where the satellite is closest to the Earth is called the parage, the furthest point from the Earth is the apogee. That's the high point of the orbit. And a lot of communication satellites have an elliptical orbit. And you might wonder why, Well, because an elliptical orbit means that a satellite is going to travel over a specific region for a really long time as it moves through its apogee, right, because it's slow, and this is the part where it's for this from the Earth, So you can provide a long period of coverage UH using this kind of orbit. And then when it moves out of sight, when it's out of the line of sight, it's actually starting to approach its parage, so it speeds up, so it zips around the back of the Earth. So this way you have UH limited interruptions of coverage. And if you have just a few set communication satellites that have these kind of elliptical orbits over a region, you can have consistent communications coverage over that region and you don't have to use as many satellites. UH. You just have to have enough so that there's one to cover. When you know, when satellite A is moving out of site, you have a satellite B that you can switch to that will continue coverage. So these are really important orbits specifically for communications uh satellites, not just them, but that's a big reason to to use an elliptical orbit. And sometimes we describe these satellites with these orbits as having highly elliptical orbits or h e O s. And then let's wrap this up with lagrange orbits or lagrange points. Okay, so there are a few positions in space in our Solar System where if you place an object there, it tends to stay there relatively speaking. I mean, you do have to remember that all of us, our Solar System included, we're all whizzing through space. So really when we say it stays there, we we mean relative to Earth or in it doesn't have to be Earth. You can have lagrange points around any orbiting objects, but we primarily concern ourselves with the Earth lagrange points. So at these points in space, the gravitational pull of two large masses on an object precisely matched this in tripetal force needed for that object to move with them, so that that's complicated, but it's kind of like saying, imagine you've got a tug of war game and both sides of the game are of perfectly equal strength. So the middle of the rope that's being used in the tug of war isn't going anywhere because the forces that are acting on it on either side are equal. Well, there are five lagrange points in our Earth and Sun relationship Earth Sun Moon. Really one is on the opposite side of the Earth from the Sun, so it's always on the night side because it's always going to be on the opposite side of the Earth from where the Sun is. This is at a point that's actually beyond our moon, so it's it's beyond lunar orbit. This is the L two lagrange point. This is where the James Web Space Telescope is, along with a few other space observation satellites, and it's useful because when you put satellites out in this point, they are protected from the radiation of the Sun. So if you're trying to detect very faint sources of radiation out in the in the in the universe, then you don't have to worry about the radiation from the Sun interfering um. You also only need a heat shield on one side of the satellite because it's going to be the heat that's radiated from the Sun and the Earth which will be behind that satellite. Well it's facing out towards you know, space. The L one lagrange point is between the Earth and the Sun. It's actually much closer to the Earth than the Sun. But that makes sense because remember gravitational force sorry Einstein, is dependent upon not just mass but distance. So you have, since the Earth is far less massive than the Sun, you have to have the satellite at a position that's much closer to the Earth than it is to the Sun. But once you get to that sweet spot, it'll pretty much stay there. And we've got satellites in that orbit that are designed to observe the Sun. So that's how we, you know, get something that is in a fixed orbit between the Earth and the Sun. It can maintain that orbit and it can have continuous observation of the Sun, which is really useful science information for us. There's the L four and L five lagrange points. These are actually along the Earth's orbit around the Sun. So there's one leading the Earth's orbit and one trailing behind the Earth's orbit, and they're each at a sixty degree angle out from the Earth with respect to the Sun. These points are the only ones where an orbit can just be stable without further adjustments orbits at the other lagrange points are delicate. They require near constant adjustments to maintain in place. I saw one uh analogy that suggested it's kind of like arching a ball on the point of a pyramid, and you have to do it just right for it to maintain balance, and you probably are going to have to do constant adjustments so that it doesn't tip over. And finally, we have the L three lagrange point. This one's on the opposite side of the Sun from the Earth, So if you were to draw a straight line from the Earth through the Sun to the other side, that's where the L three point is. We are not likely to ever use that for a satellite for a good reason, because the Sun would always be between us and that satellite, and the Sun would block any communications that we could send to or from that satellite. You could presumably have some form of space station there, I guess, but it would be one that would be effectively cut off from the Earth without you know, some other network out there, because again the Sun is huge, it's gonna block all other communication efforts. But that is a quick rundown of satellite orbits. Obviously, it gets way more complex than this, And again I didn't touch things like orbits around other planets, which can get pretty complicated, particularly with planets that have lots of moons on them. Um. And obviously the plants also have different masses, which means that you're taking different things into consideration as far as the gravitational pull. So yeah, it does get really complicated, but I wanted to make sure that we had sort of a basic coverage of the subject to kind of kind of get an appreciation for all how complicated this is. As for space junk, well, I mean, there are certain orbits that are very valuable and they can only hold a certain amount of satellites before you start to run into the possibility of collisions in that orbit, which obviously can cause an enormous problem. Not only are you talking about the potential destruction of at least two satellites, you're also talking about those satellites then creating more space junk, like more shrapnel if you will, that can potentially put other satellites in danger, and it can become this cascade effect. Uh, you know, there are graveyard orbits that we've had, you know, satellites get pushed into in order to kind of be out of the way. But that will eventually get pretty complicated to Also, another big issue for astronomers here on Earth is that the more satellites we put out in space, the more interference there is for astronomical observations, at least using earth bound telescopes. So that's another big issue UM, and it's complicated, Like you start looking at things like SpaceX's plan with Starlink, and it's not the only Internet based satellite system that's been proposed to use you know, thousands and thousands of satellites. There are others as well, and you start to see where the potential issues are. And we've had people warning about the dangers of space junk for a very long time, but I feel like there hasn't really been a huge move on the regulations side to kind of curb that UM. And of course certain countries are probably a bit more gung ho about pursuing opportunities to get satellites on in orbit than others. So this is going to continue to be an issue and it's just going to get worse before it gets better. Uh, it is odd to think that for something as vast as space, there is this ligitimate concern about the potential for collisions in these specific orbits. But that's where we are. Okay, that's it for our brief overview of satellite orbits. Hope you learn something, Hope you enjoyed this. Hope you go out and look up more information about this so that, uh, you know, my poor explanations can become more clear. As you see things like video representations of these orbits, you can kind of understand why we use the orbits that we do. And if you have suggestions for future topics I should cover on tech stuff, whether it's a technology, a company, a person in tech, a trend, something basic that you would like me to explain in the tech stuff tidbits, let me know the best way to do that is to reach out on Twitter. The handle for the show is tech Stuff hs W, and I'll talk to you again really soon. Text Stuff is an I Heart Radio production. For more podcasts from I Heart Radio, visit the i Heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows,

Welcome to tech Stuff, a production from I Heart Radio. Hey there, and welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm an executive producer with I Heart Radio. And how the tech are you? You know? Ever since the then Soviet Union sent ups foot Nick way back in nineteen fifties, seven man made satellites have played a really important role in our world in multiple contexts. You know, in the early days, at least from a political standpoint, it was a lot about demonstrating scientific and engineering superiority. That was kind of what was driving the space race, at least from a financial and political standpoint, back when the US and USS are we're racing to achieve first in space. But I mean, obviously they're also important to further our scientific under standing of our world and beyond, and also to do stuff like layout communications infrastructure that would allow for global communication. And of course there are thousands of other applications and satellites are really out of this world. And yes, I also hate me for saying that, And I thought it could be a little beneficial to talk about the various orbits that satellites can inhabit and then explain the differences between those orbits and the purposes of them. And I think that's really helpful in order to understand stuff like why is the James Webb Space Telescope in an orbit that's so far out that we cannot reach it with a human crew? Right? Why is that? Or why scientists warn us about the dangers of space chunk. I mean, space is huge, so you would think the odds of any two objects colliding with one another out in space would be astronomical. Man, I'm gonna have a lot of puns in this episode. So we're gonna go through the various orbits and explain we would send certain types of satellites to one orbit versus another. And first of all, let's let's actually just talk about the word orbit. And I'm sure everyone out there has a grasp on this, but technically, what we're talking about is a curved path that causes one object to move around a second object, or two objects to move around each other due to the poll of gravity. And gravity is one of the fundamental forces of the universe. It's also the weakest one, by the way, it has practically no effect once you get down to the molecular or atomic level. Gravity is a force of attraction that exists between stuff in our universe. What has mass, right, anything that has mass experiences the effects of gravity. So technically you could say there's a gravitational attraction between every object that has mass and every other object that has mass. However, the magnitude of that attractive force is dependent upon two really important factors. One is the actual mass of the objects in question. The more mass, the greater the attraction, So to truly massive objects will have a greater attraction to one another than two very small objects. This is why when we get down to the molecular and atomic levels, gravity is is negligible. We can just ignore it. Uh. This, by the way, is also why the gravity on the Moon is so much less than the gravity on Earth. The acceleration due to gravity on the Moon is a little less than sevent of that what we'd experienced here on Earth, So the gravitational pull between say the Moon and an astronaut is much less than what that astronaut would experience while walking around on Earth. Because the Moon is less massive than the Earth, the astronaut is probably about the same. But the other factor is the distance that's between those two objects if they are really far apart, the gravitational force between them, while technically still being present, will be extremely weak. Again, if it's really really far apart, you can ignore it because it's so weak as to be you know, almost nothing. I should also add the Einstein's theory of general relativity actually dismissed the idea of gravity being an actual force. Rather, gravity is the consequence of objects with mass bending spacetime, and that gets a little difficult to envision, so let's simplify it. Imagine that you have a trampoline and then you put a pretty heavy bowling ball in the middle of that trampoline. Well, the weight of the bowling ball will cause the trampoline's surface to deform right, it will dip downward because the weight of the bowling ball. And if you were to try and roll a marble across the trampoline, then it's stead of traveling in a straight line, the marble's path would be affected by that bend in the trampoline. It would actually turn towards the dip and thus towards the bowling ball. Well, Einstein's theory stated that we're seeing that exact same effect out in the universe, except while we could describe the surface of a trampoline effectively as a two dimensional object, you know, an object that doesn't have depth to it. In space, we have to deal with three dimensions, that being spatial dimensions. I mean we also have time, which is the fourth dimension. And this gets are a bit tricky for us to visualize, or at least I find it tricky. Maybe you can do it. I can't. But yeah, when we often refer to gravity as a force, Einstein would correct us on that one and say it's not really a force. Now, with that bowling ball and marble trampoline example, we can actually understand why satellites have to work in the way that they do. So let's say you roll the marble hard enough to reach the point where the bowling ball's presence is going to cause the marble's pathway to change, But you're not rolling it so hard that the marble can make it out the other side to the opposite, you know, into the trampoline. So, in other words, the marble is unable to escape the bowling balls gravitational pull. The marble will roll down and hit the bowling ball and come to a stop it at some point. Now, if you rolled the marble really hard. It might be able to get through the deformed area of the trampoline's surface like it might have enough momentum too to navigate through the dip. But its path is still going to change, right. It's not a flat surface. It's not going to travel in a straight line. It will have a bend in its pathway. But maybe it will get all the way across the trampoline. Uh, it just won't be directly across. However, if you wanted to keep the marble so that it's constantly circling the bowling ball, well, we would have to have some way to keep the marble at just the right speed. It would need to be fast enough to counteract the marble's tendency to fall toward the bowling ball, but not be so fast as to cause the marble to continue off the pathway and eventually off the edge of the trampoline. If we could add energy to the marble consistently, we would be all set, because otherwise, the friction that the marble would encounter as it rolled across the trampoline would be enough to slow it down and it would fall towards the bowling ball. So we'd have to find a way to give the marble a little boost now and then in order for it to maintain its circular pathway around the bowling ball. So satellites in orbit around something else, whether it's our planet or some other celestial body, need to move at a speed that's fast enough to avoid falling toward whatever it is orbiting around. So out in space there aren't nearly as many factors that would slow down a satellite speed as we find here on Earth. There's very little friction or air resistance out there, So once you get a satellite in orbit, the speed the satellite has courtesy of the launch vehicle is sufficient to keep most satellites in an orbit for many years. Satellites have thrusters, and they have fuel, but those thrusters are not meant to accelerate the satellite in order for it to maintain orbital speed. Those thrusters are really used to maneuver the satellite so it can either transition from one orbit to another, go through a transfer orbit in other words, or used to move the satellite out of the pathway of potential space junk or other debris. Now, satellites and lower orbits can and do experience drag from the Earth's atmosphere, so there's actually no hard boundary for where our planet's atmosphere ends. We do have the Carmen line, which is sort of a convenient definite mission of the edge of space, but it's mainly there as a way to define it for political purposes and just to have a practical definition, because it's so nebulous again to use another pun and so vague that it's very difficult to say this is uh categorically where space begins, and the common line is at a hundred kilometers above sea level here on Earth. Now, that does not mean that there is no atmosphere beyond one kilometers in altitude. There is atmosphere beyond that limit, but it's extremely thin. Individual particles can be very far apart from each other, so it doesn't resemble the atmosphere we have here on the surface. UH. And these few particles are still enough to cause drag on lower altitude satellites, so gradually those satellite speeds will slow down enough that, um, you know, it will eventually de orbit. It will lose enough velocity and fall back to Earth unless we were to do something like if we were to move it to a different orbit than that could be enough to extend the life of the satellite, or we might even use thrusters to push the satellite out into an orbit where it'll just be dead out there in space. Now we can classify Earth satellite orbits in different ways, including their altitude. Now, we can classify Earth satellite orbits in several different ways, and I'll explain some of those ways when we come back from this break. Okay, before the break, I mentioned we can classify Earth orbits in several different ways. One of those ways is the altitude of those orbits. Generally speaking, we can split altitudes into low Earth orbit, mid Earth orbit, and high Earth orbit. The low orbit range is around one to two thousand kilometers above sea level, so these are well above the Carmen line. Obviously, remember the carbon lines at a hundred kilometers above sea level. These satellites move really wicked fast. Uh. These are satellites that orbit the Earth several times each day, so they're not orbiting the Earth in time with the Earth's rotation. They're actually going faster than the Earth's rotation. The lowest orbiting satellites are completing in orbit somewhere around minutes per orbit. That means a satellite like that could orbit the Earth around sixteen times each day. However, lower satellites are going to encounter more drag because they're gonna be hitting the occasional particle of atmosphere and their orbits will deteriorate faster than those satellites that are at a higher orbit. And these lower satellites and only be useful for a few years. So you wouldn't want anything designed for a long term mission to be in that orbit. Uh, it would it would not be able to maintain that orbit for longer than a few years. In the low Earth orbit range, we have a lot of satellites that do Earth observations, so satellites meant for Earth sciences often occupy this space. In addition, satellites like space x is Starlink network, they occupy the low Earth orbit range. There around five kilometers above sea level, so not quite in the middle of low Earth orbit range. They're actually on the lower end. And part of SpaceX's strategy for Starlink is to launch tens of thousands of satellites into that general orbit to provide global consistent coverage for Internet service and to essentially resupply those satellites as older ones are decommissioned, which is kind of a fancy way of saying, they either get e orbited as then they fall back to Earth or they're pushed into an orbit that no one is using, kind of a graveyard orbit. Now, the mid Earth orbit that ranges from two thousand kilometers above sea level up to thirty five thousand, seven hundred eighty kilometers, so a big big range here, and a lot of navigational satellites and spy satellites occupy this space. Um As out here, you can put satellites in an orbit where they stay above particular regions for a good amount of time each day. And in fact, now we need to talk about a special subset of orbits that are kind of between Mid Earth and High Earth orbits. And you probably heard terms like geosynchronous and geo stationary orbits. These orbits are just a touch further out from the mid orbits, and sometimes they even get grouped with High Earth orbits. It really just depends on whom you're talking to, UH, and it's very easy to confuse geosynchronous with geostationary. Technically, geostationary orbits are a subset of geosynchronous orbits. So at this altitude, this far out from the Earth, the satellites orbit is the same as the rotational speed of the Earth. So, in other words, the satellite maintains its relative position to the Earth throughout the full day. The satellite remains over the same general region of the Earth throughout the entirety of the day. Now we have to remember that the Earth also has a tilt to its axis, and this means that if a satellite is at this altitude but not directly over the equator, the satellite's position with reference to the Earth's surface will actually move north and south throughout the day. So it will still maintain its position with regard to longitude, that is, east and west. It's gonna remain in its same location east versus west, but it's latitudinal position north versus south that'll vary throughout the day. A geo stationary orbit is an orbit above the equator. That means there's a zero degree inclination with reference to the equator, and the satellite will remain over the same spot on the Earth's surface. But again, this only works if you are along the equator. This can get pretty congested like there's a There are a lot of reasons why you might want to put a satellite there so that it's over the same reference point on Earth throughout the day. But obviously there's a limited number of of orbits that you can put satellites in above the equator for one thing, you know, just to avoid things like communication interference, so it gets pretty tricky. Also, you you often will find countries that do have space programs getting treaties and agreement with countries that don't but are equatorial countries so that they can essentially get the rights to place a satellite above those countries. This is one of those cases where it's not just science and technology but politics that become important. And then you also have high Earth orbit was where we start to go beyond the geo stationary and geosynchronous orbits. We're talking about altitudes greater than thirty five thousand seven kilometers now way out here, you typically are talking about things like communications, satellites, um it can be other things too, but you know, you start to get limited in what useful stuff you can put out in this orbit. Oddly enough, when you go much further out you can find uh other really interesting uses like the James Webb Space Telescope. But we'll get there now. I mentioned geo stationary orbits, which requires the satellite to not only be above the mid Earth orbital age, but also over the equator ak zero inclination with reference to the equatorial plane. But we can classify other orbits by referencing inclination. For example, a polar orbit is one that passes over the North and South Pole over the course of its orbit, and this requires an inclination of ninety degrees. That is, it needs to be at a right angle with reference to the equator. And then you have sun synchronous orbits. Okay, so this gets really complicated, but I'll try and give you a very very high level view. Again. Another pun and you might want a satellite in a sun synchronous orbit to observe certain regions of the Earth, and you want the lighting of those regions to be consistent from one day to the next. Well, if you want to do that, you put a satellite in a polar sun synchronous orbit. This is an glinnation of about ninety eight degrees, so it's a little bit further out from a right angle, and a satellite in this orbit will orbit north south or depending upon your point of reference, south north around the Earth, and meanwhile the Earth is continuing to rotate east west below the satellite. Now, interestingly, the satellite's orbital path will also begin to rotate. In fact, that's actually crucial because if the orbital path did not rotate, you know, you can think of it like a hula hoop around a globe, where the hula hoop is going over the north and south pole, so it's vertical with respect to the globe. Then imagine that you would slowly twist the hula hoops so that it is actually orbiting the Earth that way as well. It's important because you have to remember the Earth is an orbit around the Sun. So in order for you to have a consistent satellite view with the same lighting over the same region each day, the orbit has to rotate, right, because the Earth is going around a circular path of the Sun. If the orbit didn't rotate, then you wouldn't have that effect of passing over the same region um at the same time of day each day. Now, the rotation of the orbit happens because the Earth is not a perfect sphere. It's a bit bigger around the equator and holy cats, I can totally relate to that. And so the equator region exerts the gravitational pull on the satellite that if no other physics were involved, would ultimately cause the satellite's orbit to drift into one that's over the equator. But due to the satellite's angular momentum, the satellites orbit doesn't tilt down to become equatorial. Instead, the whole orbit rotates. If you if you were to ever use a coin, and you've seen a coin start to do that that cool rotate thing on a table, like it's it's starting to fall, but it hasn't actually clattered flat on the table, but it's doing that thing where it's kind of rotating around, almost like a top. That's kind of what the orbit is doing. And the rotational speed of the Earth, the rotational speed of the orbit, and the period of the orbit line up so that the satellite will always pass over a specific spot on the Equator at the same time of day each day. So let's say it passes over Bogatam at three pm. Well that's gonna happen from there on out, So tomorrow it'll be overhead of Bogata at three pm, and the next day, and the next day and so on. Subsequent orbits throughout the day will have the satellite pass over different equatorial cities, like say Singapore or Nairobi, and it will always pass over those respective cities at the same time of day each day for that city. I'm not saying it will pass over Bogata, Singapore and Nairobi at three pm. That would be impossible, but that they will pass over uh those respective cities at the same time per day. And I realized that this gets really tricky to imagine. It's hard to explain without visual aids. So if you're having trouble getting a handle on polar Sun synchronous orbits, I recommend searching for videos that illustrate how they work. Also, I'm not even scratching the surface here as far as how complicated these get. If you really want to learn more, I recommend a paper by Ronald J. Bowaine, and it's titled A B C's of Sun Synchronous Orbit Mission Design. It is a really good paper that goes into the technical details. Anyway, you might wonder why we would even worry about getting that kind of information in the first place, Like what's the big deal. Why do we even care about getting a satellite out there to pass over the same part of the Earth at the same time of day each day. Well, one reason is that it helps us track changes in a region over time. This is particularly important as we examine the effects of climate change in that region. So you want as many factors to be the same in your observation so that any differences you see you can say, well, this clearly didn't show up because the satellite is passing over at a different time of day, so the lightings at a different angle instead, Uh, really reflective of actual changes that are happening on the ground. So keeping as much of your other factors consistent as possible is really important. Keeping in mind that obviously, like angles of light are going to change as the seasons change, but you know that's something you can you can factor in. Whereas like you want to be able to say, like, from one summer to the next, Oh, we've seen that, say the coastline of this region has changed dramatically, and potentially that's due to climate change. That's why you would need to have something like this so that you could draw those kind of conclusions. All Right, we've got more to say about orbits. I know it's just gonna keep on going around and around, because that's what orbits do. But before we get to that, let's take another quick break. Okay, so far, what I've described are you could essentially call them circular orbits. They don't have to be, but that's the way we typically imagine orbits, or at least the way I typically imagine an orbit is kind of like a circle around whatever body it's orbiting, so they more or less keep a a consistent distance from the the orbiting uh center, so Earth. In other words, like they would just keep a pretty consistent distance from the Earth. But orbits do not have to be perfectly circular, or even circular at all. You can have elliptical orbits, and an elliptical orbit is oval in shape, and this means that the satellite's distance from the Earth varies throughout its orbital path. That also means that the satellite's velocity will change as it orbits the Earth. So as the satellite is moving toward the Earth, its velocity will start to increase due to the Earth's gravitational pull, and as it moves away from the Earth, its velocity begins to slow down again because the Earth's gravity is pulling back on it. Now the low point of the orbit, so the part where the satellite is closest to the Earth is called the parage, the furthest point from the Earth is the apogee. That's the high point of the orbit. And a lot of communication satellites have an elliptical orbit. And you might wonder why, Well, because an elliptical orbit means that a satellite is going to travel over a specific region for a really long time as it moves through its apogee, right, because it's slow, and this is the part where it's for this from the Earth, So you can provide a long period of coverage UH using this kind of orbit. And then when it moves out of sight, when it's out of the line of sight, it's actually starting to approach its parage, so it speeds up, so it zips around the back of the Earth. So this way you have UH limited interruptions of coverage. And if you have just a few set communication satellites that have these kind of elliptical orbits over a region, you can have consistent communications coverage over that region and you don't have to use as many satellites. UH. You just have to have enough so that there's one to cover. When you know, when satellite A is moving out of site, you have a satellite B that you can switch to that will continue coverage. So these are really important orbits specifically for communications uh satellites, not just them, but that's a big reason to to use an elliptical orbit. And sometimes we describe these satellites with these orbits as having highly elliptical orbits or h e O s. And then let's wrap this up with lagrange orbits or lagrange points. Okay, so there are a few positions in space in our Solar System where if you place an object there, it tends to stay there relatively speaking. I mean, you do have to remember that all of us, our Solar System included, we're all whizzing through space. So really when we say it stays there, we we mean relative to Earth or in it doesn't have to be Earth. You can have lagrange points around any orbiting objects, but we primarily concern ourselves with the Earth lagrange points. So at these points in space, the gravitational pull of two large masses on an object precisely matched this in tripetal force needed for that object to move with them, so that that's complicated, but it's kind of like saying, imagine you've got a tug of war game and both sides of the game are of perfectly equal strength. So the middle of the rope that's being used in the tug of war isn't going anywhere because the forces that are acting on it on either side are equal. Well, there are five lagrange points in our Earth and Sun relationship Earth Sun Moon. Really one is on the opposite side of the Earth from the Sun, so it's always on the night side because it's always going to be on the opposite side of the Earth from where the Sun is. This is at a point that's actually beyond our moon, so it's it's beyond lunar orbit. This is the L two lagrange point. This is where the James Web Space Telescope is, along with a few other space observation satellites, and it's useful because when you put satellites out in this point, they are protected from the radiation of the Sun. So if you're trying to detect very faint sources of radiation out in the in the in the universe, then you don't have to worry about the radiation from the Sun interfering um. You also only need a heat shield on one side of the satellite because it's going to be the heat that's radiated from the Sun and the Earth which will be behind that satellite. Well it's facing out towards you know, space. The L one lagrange point is between the Earth and the Sun. It's actually much closer to the Earth than the Sun. But that makes sense because remember gravitational force sorry Einstein, is dependent upon not just mass but distance. So you have, since the Earth is far less massive than the Sun, you have to have the satellite at a position that's much closer to the Earth than it is to the Sun. But once you get to that sweet spot, it'll pretty much stay there. And we've got satellites in that orbit that are designed to observe the Sun. So that's how we, you know, get something that is in a fixed orbit between the Earth and the Sun. It can maintain that orbit and it can have continuous observation of the Sun, which is really useful science information for us. There's the L four and L five lagrange points. These are actually along the Earth's orbit around the Sun. So there's one leading the Earth's orbit and one trailing behind the Earth's orbit, and they're each at a sixty degree angle out from the Earth with respect to the Sun. These points are the only ones where an orbit can just be stable without further adjustments orbits at the other lagrange points are delicate. They require near constant adjustments to maintain in place. I saw one uh analogy that suggested it's kind of like arching a ball on the point of a pyramid, and you have to do it just right for it to maintain balance, and you probably are going to have to do constant adjustments so that it doesn't tip over. And finally, we have the L three lagrange point. This one's on the opposite side of the Sun from the Earth, So if you were to draw a straight line from the Earth through the Sun to the other side, that's where the L three point is. We are not likely to ever use that for a satellite for a good reason, because the Sun would always be between us and that satellite, and the Sun would block any communications that we could send to or from that satellite. You could presumably have some form of space station there, I guess, but it would be one that would be effectively cut off from the Earth without you know, some other network out there, because again the Sun is huge, it's gonna block all other communication efforts. But that is a quick rundown of satellite orbits. Obviously, it gets way more complex than this, And again I didn't touch things like orbits around other planets, which can get pretty complicated, particularly with planets that have lots of moons on them. Um. And obviously the plants also have different masses, which means that you're taking different things into consideration as far as the gravitational pull. So yeah, it does get really complicated, but I wanted to make sure that we had sort of a basic coverage of the subject to kind of kind of get an appreciation for all how complicated this is. As for space junk, well, I mean, there are certain orbits that are very valuable and they can only hold a certain amount of satellites before you start to run into the possibility of collisions in that orbit, which obviously can cause an enormous problem. Not only are you talking about the potential destruction of at least two satellites, you're also talking about those satellites then creating more space junk, like more shrapnel if you will, that can potentially put other satellites in danger, and it can become this cascade effect. Uh, you know, there are graveyard orbits that we've had, you know, satellites get pushed into in order to kind of be out of the way. But that will eventually get pretty complicated to Also, another big issue for astronomers here on Earth is that the more satellites we put out in space, the more interference there is for astronomical observations, at least using earth bound telescopes. So that's another big issue UM, and it's complicated, Like you start looking at things like SpaceX's plan with Starlink, and it's not the only Internet based satellite system that's been proposed to use you know, thousands and thousands of satellites. There are others as well, and you start to see where the potential issues are. And we've had people warning about the dangers of space junk for a very long time, but I feel like there hasn't really been a huge move on the regulations side to kind of curb that UM. And of course certain countries are probably a bit more gung ho about pursuing opportunities to get satellites on in orbit than others. So this is going to continue to be an issue and it's just going to get worse before it gets better. Uh, it is odd to think that for something as vast as space, there is this ligitimate concern about the potential for collisions in these specific orbits. But that's where we are. Okay, that's it for our brief overview of satellite orbits. Hope you learn something, Hope you enjoyed this. Hope you go out and look up more information about this so that, uh, you know, my poor explanations can become more clear. As you see things like video representations of these orbits, you can kind of understand why we use the orbits that we do. And if you have suggestions for future topics I should cover on tech stuff, whether it's a technology, a company, a person in tech, a trend, something basic that you would like me to explain in the tech stuff tidbits, let me know the best way to do that is to reach out on Twitter. The handle for the show is tech Stuff hs W, and I'll talk to you again really soon. Text Stuff is an I Heart Radio production. For more podcasts from I Heart Radio, visit the i Heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows,