It's All Relative


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I'm an executive producer with iheartradio and a love, all things tech, and in our last episode I explained how communications satellites send information via radio waves, which is why we talked about signals from such things in terms like hurts. Hurts unit refers to the number of repeated phenomena over the course of a second, so imagine that you're dribbling a basketball so that the ball goes from your hand to the ground backup to your hand once per second well, you could describe your dribbling as being one hurts in frequency, one full cycle per second up. Up Now. If you dribbled twice as fast so that the ball went up down up to full times per second, then there would be too hertz well. We can describe lots of stuff with the unit hurts. We use it to describe sounds in which case we're talking about. The frequency at which stuff vibrates. Typical human hearing spans a range of frequencies that at the low end is at twenty hurts. That represents the lowest pitches of sounds, those deep bass notes that's around the twenty hertz of area and then it goes all the way up to twenty kilohertz or twenty thousand Hertz, that represents the very highest pitches that people can typically here, and those frequencies correlate to how quickly stuff is vibrating back and forth now when it comes to us hearing things, we usually mean that we're talking about the vibrations and fluctuation in air pressure, and those fluctuations in air pressure interact with our eardrums. But we can use hurts to talk about all sorts of stuff including the processor speed of a CPU. In that case, we're really talking about the number of clock cycles per second, so you get it. This is a description of the frequency of the number of times. A certain thing happens like within a second and I also explained that we measure the rate at which we can send data using the term bits. A bit is a basic unit of digital information, and when we talk about computers were talking about bits in the form of a zero or a one binary information. Just like your basic to way. Physical switch has two positions off or on so if If, you hear a term like kill a bit that means one thousand bits, and megabit is one million bits, and a gigabit would be one billion bits likewise, megabits per second tells us how many million bits can move from one point to another per second over that connection, so if you've got a one hundred megabits per second connection, theoretically, it would mean that up to one hundred million bits can transfer across that communication channel per second, though that's not how it works out most of the time, but that's a matter for a different episode. I didn't mention that this is different from something like megabytes, so a bite is a unit that consists of eight bits. And this gets confusing because we often described stuff like file sizes in terms of bites, but transfer speeds in terms of bits, so let's say that you do have that. One hundred megabits per second download speed, and you want to download a one hundred megabyte file will that means it's not going to take one second. It's GonNa. Take eight seconds to download the file because a megabyte is eight times larger than a mega bit and actually even that is a little bit misleading. Misleading because in computer memory terms, we typically look at units of memory based on powers of two rather than powers of ten, so instead of a kilobytes being one thousand bytes. It's actually one thousand twenty four bites, and there's no standardization in the tech industry so sometimes people will say kilobytes, and they mean one thousand bytes sometimes they'll say kilobytes, and they mean one thousand twenty four bites, and you will want to tear your hair out, and then you'll look like I do. I'm bald if you didn't know, but this episode isn't about the peculiarities of our naming conventions in the computer information age instead I wanted to tackle something else. That affects everything really, but in particular. We really had to Suss it out. In order to make certain types of satellites work properly, and this is the concept of relativity so in this episode. We're really going to learn why and understanding of relativity is important if we want our certain satellite technologies to work. Work and it serves as a great reminder that technology is only really possible through an understanding of science you can think of tech as the physical manifestation of our understanding of scientific principles, and that means if we were wrong in our understanding of science, technology shouldn't really work so in the way you can think of technology that works as evidence that the scientific method is a darn good formula. Since we're talking about, relativity means we're GONNA. Be Talking about R real. Today his name was Einstein which is convenient, but before we get to Einstein, we have. Galileo Galileo Galileo Figaro. Wait No, I'm sorry that's Bohemian. RHAPSODY I meant. Galileo Gallo lay this Galileo made an observation that if you've got to observers moving at a constant speed and direction, so they're moving at the same velocity, they will get the same results for any experiment that involves stuff around a mechanical experiment. This is easier to understand if we use an example and I like one that my colleague Robert Lamb used when he wrote about relativity for how stuff works dot com back in the day he used. Used an example of a train and A. Scientific Ping Pong. Ball Art. So imagine you've got a scientist who standing in the middle of an aisle on a moving train, and the train is moving at a steady speed in a straight line, so there are no active forces of acceleration. Going on here remember acceleration describes a force that involves a change in velocity. The other means a change in direction or a change in speed or both, but in this case constant speed constant direction Robert used nice round numbers in his example, so he suggested that the train is moving at one hundred miles per hour. Well, it's not round if we go to the metric system that would be one hundred sixty one kilometers per hour. If the train stays steady to the scientist, it will feel as if that scientists is actually just standing still just anywhere, and we're conveniently ignoring an emotion that would happen due to irregularities with the train's wheels or the train tracks or anything like that, and if this is hard for. For you to imagine just think about how you feel when you're standing still or sitting still or laying down here on earth, we know the earth is moving through space. It is a body in motion, but when we are still relative to the earth itself. We don't feel that motion. Assuming there's not some other weird event going on like an earthquake, which is something separate, but back to our hypothetical. Hypothetical train, the scientists tosses the Ping Pong ball down the aisle. Now from the scientists perspective this Ping Pong Ball will travel at whatever speed they threw it at Robert, actually suggests a relatively gentle toss of five miles per hour or eight kilometers per hour. The Ping Pong Ball would bounce down the aisle just as it would. If the scientists were to toss the ball on a train that isn't. Isn't moving at all or on just flat ground. However, let's say we have a second observer. WHO's not on the train? They're standing off to the side and they can see through the train to this person. It will appear as if the Ping Pong ball is moving very fast indeed relative to this stationary observer, the Ping Pong. Ball will appear to move at the speed at which it was thrown. In addition to the speed of the train itself, so if we take the two figures, we get one hundred five miles per hour or one hundred sixty nine kilometers per hour. This is called Galileo on transformation alternatively, if the scientists were throwing the ping pong ball in the opposite direction of the trains travel so there facing towards the back of the train, it would appear to the second observer. The Ping Pong ball was moving at a slower speed than the overall train was whereas to the scientists on board. The Ping Pong ball would still be traveling. Traveling at that five mile per hour speed, so this is where the term relativity comes into play. The effects observed are relative to the perspective of the Observer. It's all by based on the reference frame of that observer. If you're on the train, then you're just looking at a ping pong ball bouncing at a relatively slow speed down the aisle. If you're not on the train the ping, Pong, ball is moving quite fast, so it's all relative Isaac. Newton would follow along and say yeah. May, this old tracks, I don't know I, talk like that. In his laws of Motion Newton stated that these laws of motion should hold in an inertial frame as well as reference frame that was moving at a constant velocity, relative to the inertial frame and inertial frame by the way is just a frame of reference, in which there are zero net forces acting upon it so that there are no forces of acceleration in play, so in our example. The train that we talked about that would be our initial frame. All of this is fairly intuitive, but then we get to something really tricky Einstein would establish that these speed of light in vacuum is the fastest speed in our universe. Nothing can go faster than that, but hey, what if you're on a train? That's traveling one hundred miles per hour and facing forward facing the direction of travel, and then you have a flashlight and you turn on the flashlight. Well doesn't mean you should perform a Galilea transformation on this and say the light from that flashlight in your hands is actually travelling at the normal speed of light on board the train, but also get that boost of the trains travel, so it should be the speed of light plus one hundred miles per hour. Doesn't that make sense bowl? According to actual experiments performed before Einstein would come around to explain things the answer was. Not done the like it works that way. Scientists Edward Morley and Albert a Mickelson created an experiment to measure the speed of light back in eighteen, eighty seven, and actually they were looking for for something else. They were looking for evidence of a hypothetical substance called luminous. Ether. Saywhat. All right, we'll stick with me because. In a way, this does make sense okay, so on earth we see waves traveling through a medium right like if you look out in the ocean, you can see actual waves in the water, and the water is a physical medium through which these waves travel sound can't travel in space because space is effectively a vacuum, the particles that are in space are so far apart from one another then there's no way for the vibration of one particle to come into contact an effect. Another particle sound can't travel sound travels through the propagation of vibrational waves, and if your stuff isn't in contact with each other, there's no way for. For them to have that wave propagate, so there has to be some sort of medium like air or solid surfaces or something in order for sound travel. Well, if that's the case, said the folks of the time, then stuff like light must need some sort of medium to travel through right. I mean sound has to have lite must have something to like indefinitely. Travel through space I. Mean That's how we can see anything. Because light from the sun travels through space to hit the earth, so the light has to be moving through some sort of medium, we cannot observe directly. This hypothetical medium was the aforementioned luminous versus either. Either but assuming this ether existed at all, it had to be pretty darned special, because we can't feel it. We can't detect it. It creates no observable effects. So if it were real, it had to be unlike pretty much anything else. We had discovered up to that point now. Let's assume that the universe is filled with this ether stuff. The question arises held the heck. Does the ether interact with all the physical stuff that's in the universe, the actual matter and also energy after all the bodies in space, stars, planets, moons, and all that other stuff. All of that is moving. None of it is standing still and if. If it is moving. It would presumably disturb this ether medium. Right I mean if you move your hand through a pool of water, you are disturbing that water. You're making currents and eddies, so it was thought that the motion of all these elements in space would disturb the ether in some way, and hypothetically there would be some sort of ether wind, but if there were a wind, then presumably, the speed of light would be affected depending upon the wind's direction in relation to the lights direction, so think of a really windy day in the real world. If you're walking against a very very tough wind like gale, force. Wind Power through it to keep moving forward now. If you're walking with the wind, the wind is to your back and pushing you then you get a big boost while the same thing should be happening with light if ether wind were real, and so Mickelson and morally devised a gadget that would split light into two beams, directing those beams down different paths using mirrors in different directions and seeing if those. Those two beams of light would hit an piece at different times. The thought being well one of these directions would theoretically be in the same direction as the ether wind, and one would be at a crossed direction of ether wind, so should be a difference in the amount of time it takes for the lightweight from this one source that's been split into two to arrive at an eye piece. But That's not what they found. They observed no such effect. So if there were such thing as ether, the stuff wasn't giving either a boost or drag online itself no matter what the light was traveling at a constant speed, which turned out to be approximately one hundred, eighty, six thousand miles per second or around three hundred thousand kilometers per second. Now that flew in the face of Classic Newtonian, Physics, clearly with the example, the Ping Pong Ball and the train. The Ping Pong ball has to be traveling faster than the train. It's on. I mean that just makes sense. If you were standing on the top of the very front of the train, and then you through the Ping Pong Ball, and we ignore stuff like wind resistance. The Ping Pong ball would land ahead of the train, so it has to be going faster. So what the heck was so special about light and what was going on well, this was one of. Of the great mysteries that Albert Einstein said his mind to unraveling, and it formed the basis of one of his great theories of relativity, and this would be the theory of special relativity, which poses that the laws of physics are in the same in all nurses frames of references, and that means the speed of light will be the same for all observers regardless of their relative perspectives. It doesn't matter the context. The speed of light is the speed of light now there's an implication to this theory. That really got people scratching their heads. If the speed of light is absolutely constant. Stuff like distance and time are not in those a heck of a brain teaser. When we come back, we'll explore this more This episode brought to you by tide, one wash, miracle and guys I mean I got a little cute doggy is also stinky, little guy sometimes so when it comes time to wash his dog bed I have tried all sorts of stuff in order to get those odors out I'm talking belling Baking Soda we've tried the spray vodka thing on there, but one thing that really. Really has made that easier is tied one wash miracle. It's a powerful deep cleaning laundry solution that can remove particles that are deeply trapped in fibers, causing impossible odors that linger even after washing, you can order yours today from tied one wash Miracle Dot Com and get twenty percents off using the code tech stuff again. That is tied O. N. E.. Wash Miracle Dot, com. This! Episode is brought to you by IBM Today. Every answer matters more than ever before, because whether it's about health deliveries or finance, some things just can't wait. That's why IBM's helping. Businesses manage millions of calls texts and chats with Watson Assistant. It's conversational. A I designed to help your customers find the answers. They need faster. No matter the industry. Let's put smart to work with IBM DOT COM Slash Watson Assistant to learn more. Let's imagine that you live half a mile away from a lovely park and it's a half mile away in the morning. It's a half mile away at night. It's a half mile away on a Tuesday. It's a half mile away on a Saturday half. A mile is half a mile road. It's a reliable constant in our lives. If it weren't, we could never give directions to anywhere because all the. The measurements and landmarks would change all the time, and our world wouldn't make sense the way it does to us now, so in our individual experiences in our day to day lives stuff like distance seems pretty darn reliable and fixed, so how dare Einstein come along with his theory of special relativity in nineteen o five and say well. Yeah, but see the speed of light is really the true. True constant, and for that to work time and distance or space in other words must be somewhat able Einstein posited that there is no absolute frame of reference in our universe, which means there is no place in the universe that is totally stationary. Everything is moving, which means all motion is relative. You can't really talk about moving except in reference to some other moving thing so even as we. We, sit still and try to meditate. We do so on a planet that is hurtling through space. We are in motion. We're all moving through space and time, and we all have a frame of reference and each frame of reference is just as legitimate as every other frame of reference or I guess you could say if everybody's super nobody. Is I guess? I've watched the incredible too many times. One, anyway, this particular nineteen o five theory is called special relativity, because Einstein's explanation only covered special cases that being when two inertial frames are in constant motion with regard to one another, and there can be no acceleration, so the motion had to be in a straight line at a constant speed, a change in direction or speed would be an acceleration and to cover those instances. We would have to wait a decade for Einstein to work out his theory of general. Will get to that, but we've got a lot more to say about special relativity. So Einstein was taking a different approach to the results of the experiments by. michelson-morley, the scientific world at large was essentially saying this can't be right. These results can't be right. There must be something wrong with the experiment or the equipment because we're sure this theory is correct, and that ether is there Einstein was taking a totally different perspective. He was saying if we assume the experiments are producing accurate results, then it stands to reason that the prevailing theory is flawed, and we have to figure out what the real explanation, as and this is one of those important points in science. It's that if your results in your experiment, don't meet your hypothesis. It's very possible that your hypothesis is wrong now. You need to do multiple experiments to find out and to test your equipment. Make sure there's not any errors there. That could be causing the issues, but it does mean that you need to reexamine that hypothesis. And at this time, the scientific community wasn't really doing that. So Einstein did away with the ether. His explanation suggested that are observable universe has. Has Four dimensions not that there can only be four dimensions, but rather there are four dimensions we can detect and observe, and these would be up down left right forward backward, and then the fourth dimension, which is time collectively those three dimensions are space. The fourth dimension has time, and we get the space time continuum, this intrinsic relationship between space and time or space time continuum, which also gives us. Dozens of star trek episodes would use it. A shorthand for things are about to get really weird. Stein posited the speed of light is measured as constant in all frames of reference, unless think for a second what we mean by speed speed is a description of how much distance can be covered per unit of time, so speed of one hundred miles per hour means that in one hour's time we will cover a distance of one hundred miles. That's very obvious, but if the speed of light is constant for all frames of reference, regardless of how those frames are moving relative to each other that must. must mean something about space, and or time is a little Wonky, and let's think about our train experiment again. If you're aboard a train moving at a smooth one hundred miles per hour in a straight line and toss a ping pong ball straight up in the air. Well, it's GONNA. Go straight up and come right back down to your hand in a nice vertical line from an outside observer who is on the train? It would look a little differently. You would throw the ball up at one point. To this observer and the ball would appear to move not just vertically, but horizontally before coming back down now if we repeat this experiment, but we use light. We really see how he gets confusing. Okay, so now you're on a train, but it's going really fast like let's say half the speed of light, but the speed and direction are constant, so you're on this train. You don't feel any acceleration forces because you're moving at a constant speed any constant direction, so you're velocity remains same in fact. If there were no windows on the train, you wouldn't even be able. Able to tell that the train was moving at all. So let's say you've got a laser pointer and you've got a mirror on the ceiling of the train and the Photon detector on the floor of the train new shoot the laser up at the mirror reflects off the mirror, and then it comes back down and hits the detector on the floor, and it registers how long it took the light to travel from your laser pointer to hit the detector and to you. The laser makes a vertical line. All that makes sense right. You can imagine that, but for our. Observer, WHO'S NOT ON THE TRAIN? It would appear as though the laser actually travelling at a diagonal up to that mirror, and then a diagonal back down toward the detector, so for one observer, the one on the train. We have a straight line. It's vertical up down for the second observer off the train. We have an angled path sort of like how billiard ball can at the site of a pool table and bounce off at an angle? But this creates an apparent paradox. The Path viewed by you on the train is a straight line, and by definition that is the shortest distance between two points. The Path observed by the person who has not on the train is an angled line, and by definition that has to be longer. The speed of light is constant in both cases, but the distance is different between the two points of reference, and because speed distance divided by time. If the distance is different, the time must also be different between those two points of reference. Crazy. This brings us to the concept of time dilation it also by the way can affect distance, the faster and object gets the more squished it gets so if you had this train and you were to get up to near the speed of light, the train to an outside observer would appear to be shorter than it normally would be to anyone inside the train. The dimensions would remain exactly the same. You would not suddenly see a shorter train. It wouldn't be like you were in that compressor seen in star wars, the train with appear to be normal. From an outside observer, who is not traveling at that speed with it appeared that the train itself was getting squished shorter. Likewise, the faster something goes with respect to some other point of reference. That's important. The more quickly time appears to pass for those at the other point of reference or alternatively the more slowly time seems to pass for the fast moving thing. Thing from the frame of reference of the person who's not moving fast. This gets really clunky. I know it gets confusing, so let's talk about space travel. Some more examples actually make this way easier to explain all right, so let's say you've built a spaceship and this spaceship can go wicked fast like eighty percent of the speed of light and you're going. Going to go on a year long jaunt out in space, and your best friend is hanging back on earth. Now we now have our two frames of reference. We have the spaceship, and then we have the the person on earth, so let's ignore acceleration forces for the moment because we're going to have to just focus on special relativity, we'll get a general. General relativity in a moment, so your spaceship zooming around at eighty percent, the speed of light, and for you, time is passing. Normally. The seconds feel like seconds. Minutes feel like minutes hours feel like ours etc, and you're on there for a full year back on earth time is passing normally for your best friend. Who's just hanging on earth? They feel their. Their seconds pass like seconds there minutes past minutes, and so on however when we look at the two of you in reference to one, another something unusual happens so to your best friend on earth. It looks like time passing very slowly for you aboard your spaceship to you on your spaceship. It looks like time is passing super fast for your friend back. Back on Earth, so when you do get back to Earth a year later and the two of you enter the same point of reference. Things are weird from your perspective. You've only aged a year because you spent a year aboard your spaceship, but a little more than a year and a half has passed on earth while you were gone, your calendars wouldn't. Wouldn't lineup anymore. The faster you go, relative to your frame of Reference, the more pronounced the time dilation now I do want to be clear about this. It's not really correct to say that as speed increases, time slows down. You have to always relay this in terms of having another frame of reference, because within a single frame of reference. Time just passes. Passes normally. There's no difference by the way this is also why star dates in the Star Trek. Universe don't make a whole lot of sense. They tried to retroactively make it. Make sense, but keeping time when you're on a ship that can travel at the speed of light, or in the case of Star Trek magically going faster than the speed of light. And, we won't even get into warp speed all as crazy, but being able to use that and somehow related to making sense on time, passing on planets or space stations or whatever. That's a huge mess, but it's also outside of our episodes, so leave it at that. Don't notice the effects of special relativity in most of our day to day lives, because we are not traveling fast enough relative to each other for it to be a real factor most of the time. But it does get even more weird word possible to build a spaceship that could travel at the speed of light, and you were to take this sort of trip to an outside observer. Time would appear to stop for you aboard your spaceship now. If assuming this was even possible, you would still experience time in your own frame of reference as per normal, but your friend back on earth would see that. It looked like you were frozen in. In time, however, this is a moot point. Matter cannot travel at the speed of light, so it's more of a thought experiment. Anyway. However, we can actually detect time dilation with extremely accurate time measurement devices like atomic clocks. In fact, we've done it. In experiments, scientists have synchronized to atomic clocks and these atomic clocks keep incredibly accurate time down to a matter of nanoseconds a Nanosecond, one billionth of a second, so one clock was kept stationary. Speaking here on Earth, the other traveled aboard a high speed aircraft, and at the end of the experiment they compared the two clocks against each other and the one that was aboard the aircraft had measured less time than the one that stayed on the ground on earth less time passed on that aircraft relatives, the amount of time passing on the ground. It wasn't just that one clock was moving more slowly than the other. Literally less time was passing. In reference to the other point of from the perspective of the other point of reference that is the difference was right in line with Einstein's calculations. Now as we'll see, this ends up being an important point when we get to satellites, but we can't just jump on that yet. We do need to take into consideration general relativity so as I mentioned special. Relativity only looks at frames of reference that are in constant. Constant and consistent motion with regard to one another that could be no change in direction or speed, because that introduces accelerate divorces, and that changes things so to take acceleration into account. Einstein proposed his theory of general relativity ten years after his theory of special relativity, so this would be nineteen fifteen for those who are keeping track. This theory would incorporate the force of gravity into Einstein's work, which means factoring in. In acceleration, so in this theory, Einstein introduced the equivalence principle, which says that gravity pulling in one direction is equivalent to acceleration in another direction, so we can actually experience this. It's easy to remember an imagine. Imagine getting on an elevator and it's going up and as it goes up, you feel that sense of increased gravity pulling down on you as the elevator accelerates when the elevator is going down, you feel. Feel a sense of decreased gravity as the elevator accelerates downward, so gravity and acceleration are equivalent, which means that it can also affect our measurements of space and time I'm Stein. The size that gravity was warping space time itself. Take something that's really massive like a huge dense star that would warp space time around it through its gravity, and we can even observe this. Scientifically scientists have measured light. The has curved. Massive Stars this is called Gravitational lensing. Now here's another thing that gets a bit confusing. The effects of gravity on time mean that time passes differently for objects in orbit when taken in reference to time passing on earth itself time passes Faster in orbit than it does on Earth now again. This is a frame of reference thing because if you're on a spaceship in orbit. Orbit, your experience of time would feel exactly the way it does. When you are on earth, it's only when we look at this from two frames of reference that we see how it doesn't match up. So, what does this all mean for? Satellites blown means that satellites in orbit have a couple of different relativistic effects going on in our frame of reference here on Earth. Earth satellites are traveling faster than we are to maintain orbit, which means that if we compare the passing of time in each frame of reference, time would pass faster for us than for the satellite, however, due to the gravitational effect on space time, we also know that something in orbit will have time pass faster for that thing then we would experience here on earth so. So it's the opposite of the effect of special relativity in way, and the effects of special relativity and general relativity, don't actually cancel each other out which means ultimately that time on a satellite and time down here on earth are not sinked up with reference to one another, and for some types of satellites. That's a problem I'll explain more after we take this quick break. Hey, podcast I'm Jada. Pinkett, Smith host to the Red Table Talk Podcast, and I want to introduce you to two of the most important women in my life. My Mom Adrienne Banfield Norris. She's really old school. I never wanted to be in that situation like not date will at all. Everything is by the book, and then we have my daughter Willow Camille Reign Smith. Smith I'm going to be like my ancestors in just do what I need to do. We've brought these three generations to the red. Table to talk about family relationships social issues in a whole bunch more. We're all going through something right, so put on your headphones. Join me, Jada, Pinkett Smith Gammy and willow for your favorite episodes on the rare table. Talk podcast. Like glowing. Mark. Thank you I. Appreciate it. Listen to the Red Table podcast presented by Facebook, watch and Westbrook audio on the iheartradio APP, apple podcasts or wherever you get your podcast. To understand why relativity is important with certain satellites, let's talk about the global positioning system or GPS. Now this is the satellite system that provides data back to earth that makes it possible to get precise coordinates using a GPS receiver. Does that work well here on earth you could get a very imprecise idea of your general coordinates through a trilateral commission using signals from cellphone towers. This works on a fairly simple principle, so we know that the radio signals sent to and from cell phones travel at essentially the speed of light, so if a cell phone tower broadcasts out a short command, the just requests your phone to respond back with a quick response, a pain in other words. The amount of time it would take for the pain to reach the cell tower could be used to work backward and figure out how far away the phone is from that cell phone tower. Because you know the speed of travel, right is the speed of light, so you also know how much time it took. That means you can work backward to figure out the distance between those two points. However, that's just a distance. There's no direction there now. If you did this with Multiple Cell Towers, the collective data from those. Those towers could be used to get a rough estimate of where the phone is. So let's imagine we've got a map and on that map. We've got three Cell Towers, a B and c. you can see exactly where each one is, and let's say that you've got a phone. That's located somewhere within the broadcast range of those three cell towers. Each Tower sends a ping to your phone. Your phone respond with Ping back, and you are given the amount of distance between your phone and each of those three towers well. Tower as result says that you are a mile away from tower a so you actually have to draw a full circle around tower, a to represent all the possible points you could be. That are one mile away from tower a so you're drawing a mile radius around tower. A tower be responds that you're within one point five miles of tower being so you have to draw a circle round tower. Be To represent all the points where you could be. That are a mile and a half away from it. Now the circle tower be in the circle from top a should intersect each other at two points, but that means you could be at either of those two points right could be either overlap, so you don't have enough information yet by coordinating with tower. See and let's say that tells you. You're within two miles. You can draw a third circle and the point where all three circles would meet would be general location. It's not incredibly precise, but it does give you an idea of where you are. The GPS constellation of satellites does something similar only we have to think of this. In terms of three dimensional space, rather than a two dimensional map, so a satellite sends out a high frequency, low power, radio, signal and receivers pick that signal up. The receiver, let's say your smartphone doesn't have to send data backup to the satellite which is good, because would be an enormous drain on your smartphones power so really it's just listening for these signals now the receiver and satellite both run the same digital pattern relative to a specific time stamp. It's easy if we think of this as midnights, let's say that midnight hits, and this particular digital pattern starts both on the satellite and the receiver, so they're both running the exact same pattern. The satellite beams out of signal carrying this digital pattern. The satellite is far away so it takes a little time. You know not much, but a little time for that signal to get your receiver and the lag between. Between the pattern that's playing on your receiver and the signal of that same pattern coming in from the satellite tells the receiver how far away it is from that particular satellite because again we know that the city is moving at the speed of the transmission itself, and that's the speed of light, and that's constant so now the receiver knows how far away it is from that one satellite, and because the orbits of these satellites are predictable, the receiver has a record of where that satellite should be relative to the surface. Occasionally, we have to tweak that record because stuff like gravity can pull a satellite slightly out of position over time, so that actually is something that has to be addressed on occasion. This receiver will do this with at least four satellites, the y four and not three I gave the the three cell phone tower examples. Well, it's because the clocks on satellites and the clock that's running on the device that the receiver is built into may not be in, and really aren't truly synchronized and the intersection of force fears of distance like these four spheres represented various ranges that these satellites are finding themselves in with regard to this receiver. Can only intersect at one point. That's the only place they could all intersect. So if a GPS receivers clock is not matching up to the clocks on the satellites, there will be no intersection at all, and the receiver will say well. I can't find an intersection so I know that means. My clock is off from all the other clocks, and it will then adjust its own clock to be in alignment so that the four spheres have a point of intersection, and that is your location on earth now in order for our receivers to be able to do. Do, this the accuracy of the atomic clocks aboard those GPS, satellites has to be accurate within twenty to thirty nanoseconds and remember a nanosecond one billionth of a second that is an astounding level of accuracy, and because these satellites are in motion, and they are also affected by Earth's gravity, they are subject to the effects of special and general relativity, and this means we actually have to make calculations to take that into account now, according to special relativity and the relative speeds of satellites to a fixed point on the surface of the earth. We would expect the. The atomic clock aboard that satellite to register seven fewer macro seconds per day than o'clock on earth, because satellites are moving through space faster than we are relatively speaking, so that means from our frame of Reference Time is passing more slowly on that satellite than it does here on earth but general relativity comes into play, too, and general relativity tells us that the Earth's gravity warps space time around our planet and one of general relativity predictions. Is that a clock closer to a massive object so like a clock here on earth will tick more slowly than. Than a clock that is further out from that same massive object, so the closer the clock is to the mass of object. The less time it will experience, it will measure compared to a clock. That's further away, which is crazy right so taking only general relativity into account we would see that o'clock aboard one of these satellites would register more time having passed on that satellite then o'clock here on earth meaning from our frame of Reference Time is actually passing faster on those satellites than it does here for us. This would come out to about forty five. Five microseconds a day meaning that at the end of day one, the clock aboard that satellite would be ahead of o'clock here on Earth by forty five microseconds, and this would continue day after day with the gap growing wider every single day now when we bring both special and general relativity together into consideration. We see that they don't just cancel each other out right because we've got that. Seven micro-second lag due to special relativity, but we have the forty five micro-second surge due to general relativity, so in the end we're looking at a thirty eight microseconds difference. Difference per day between a clock on the satellite and o'clock here on Earth, the clocks on the satellites will get ahead of similar clocks here on Earth, by thirty eight microseconds every single day, and while micro-second is a very small amount of time I. Mean we're talking at a level that we don't typically experienced. We don't think of time and microseconds for our day to day lives. However, thirty eight microseconds is equal to thirty eight thousand NANOSECONDS, and if you're looking for an accuracy of around twenty to thirty nanoseconds, district comes an enormous problem if we don't. Don't take it into account, and this brings us back round to something. I mentioned at the top of the show. We know that Einstein was right about relativity, because we have to account for it with technology like GPS. If we didn't take into account if we didn't factor in the effects of relativity, our GPS wouldn't work for very long at all. Our technology proves that the science is real or else. The tech would fail at what it needs to do now in general, I think that's a great lesson to take home. There are a lot of voices. Voices out there that call science into question, and some of them are more outlandish than others. A person who's passionately insincerely arguing that the earth is flat seems pretty far out there for me, because so much of our technology we built upon, and we rely upon wouldn't work if that were true, even if you can't experience something directly such as having a meaningful experience of time dilation, a ton of the stuff we do experience on day to day. Basis is affected by this stuff, and it proves the existence and also the benefits of having the scientific method. Now, give a little side note on GPS to kind of wrap this up the original GPS. Configuration came out of a United States Department of Defense Project the original purpose was to provide positioning information for government and military, but specifically the United States and its allies, and for that reason, the government wished to restrict access to this technology. The general thought was that it would be better if the US didn't allow tech. That could you know? Give precise coordinates for stuff like military bases or the position of. Of various military units to people who didn't belong to those divisions, so as a matter of national security. The US guarded this technology civilian receivers, so if you went out and bought a GPS receiver, you could get public GPS signals, but the United States was purposefully instituting a policy called selective availability, which wasn't intentional degradation of public GPS signals. They were introducing errors on purpose, so that GPS receivers couldn't get an accurate, wrote location at limited accuracy to around fifty meters horizontally and one hundred meters vertically. And effectively that meant that you wouldn't really know your precise coordinates. You certainly couldn't use a GPS receiver as a turn by turn directions tool because you wouldn't even necessarily show up on the right St. you wouldn't know if you were approaching your turn, or if you'd already passed it, it was. It was not practical for that. It was only in the year two thousand when US President Bill. Clinton directed the government to end selective availability that civilian gps receivers could actually get accurate data, and that's what made the modern gps receivers stuff like our phones possible. So before two thousand GPS receivers didn't work very well for the average person, but it wasn't because the technology was bad or that the science was wrong. It worked that way or if you prefer it, it didn't work properly on purpose, and that wraps up this episode about relativity, and why it's important with technology, and it's not just satellite tack, but that's a big one. And it also ends up being a big thorn in the side for science fiction authors who want to write about interstellar travel faster than light speeds because you have to start finding alternative explanations for how that's possible, because we we've come up against these limits. That Einstein predicted so far his predictions have held true so in order to travel faster than the speed of light. You do have to create something like warp drive, which theoretically warps space around you so rather than traveling faster than light your decreasing the distance between your point of. Of origin and your destination, it would be kind of like taking a map of the United States and saying I'm going to travel from Atlanta to Los Angeles from one coast to the other, but instead of drawing a line from Atlanta to La. You just fold the map so that the two dots are next to each other, and then you draw a line that way that's how warp speed is supposed to work, because it's the only way you can get around the fact that you can't really go faster than the speed of light. But, that's a topic for another show. If you guys have suggestions for future topics, I should tackle. Please let me know. Send me a message on twitter handle. Is Tech Stuff H. S. W. I'll talk to you again really soon. Tech stuff is an iheartradio production for more podcasts from iheartradio visit. The iheartradio APP apple podcasts wherever you listen to your favorite shows. 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