Speaker 1: Welcome to Tech Stuff, a production from iHeartRadio. Hey therein
Speaker 1: Welcome to Tech Stuff, I'm your host, Jonathan Strickland. I'm
Speaker 1: an executive producer with iHeartRadio, and how the tech are you.
Speaker 1: We have an episode that originally published on July first,
Speaker 1: twenty twenty. It's called It's All Relative And when I
Speaker 1: was a kid, I was convinced that Einstein's theories were
Speaker 1: these super complicated explanations of the universe that really had
Speaker 1: no real intersection with my daily life. But as it
Speaker 1: turns out, without an understanding of relativity, a lot of
Speaker 1: the technology we rely upon wouldn't work properly. And it's
Speaker 1: fascinating stuff. Hope you enjoy. The hertz unit refers to
Speaker 1: the number of repeated phenomena over the course of a second.
Speaker 1: So well, imagine that you're dribbling a basketball, so that
Speaker 1: the ball goes from your hand to the ground back
Speaker 1: up to your hand once per second. Well, you could
Speaker 1: describe your dribbling as being one hurts in frequency one
Speaker 1: full cycle per second, up down, up. Now, if you
Speaker 1: dribbled twice as fast, so that the ball went up, down,
Speaker 1: up two full times per second, then it would be
Speaker 1: two hurts. Well, we can describe lots of stuff with
Speaker 1: the unit hurts. We use it to describe sounds, in
Speaker 1: which case we're talking about the frequency at which stuff vibrates.
Speaker 1: Typical human hearing spans a range of frequencies that at
Speaker 1: the low end is at twenty hurts. That represents the
Speaker 1: lowest pitches of sounds. You get to go those deep
Speaker 1: bass notes. That's around the twenty hurts of area, and
Speaker 1: then it goes all the way up to twenty kill
Speaker 1: a hurts or twenty thousand hurts. That represents the very
Speaker 1: highest pitches that people can typically hear, and those frequencies
Speaker 1: correlate to how quickly stuff is vibrating back and forth. Now,
Speaker 1: when it comes to us hearing things, we usually mean
Speaker 1: that we're talking about the vibrations and fluctuation and air pressure,
Speaker 1: and those fluctuations and air pressure interact with our ear drums.
Speaker 1: But we can use hurts to talk about all sorts
Speaker 1: of stuff, including the processor speed of a CPU. In
Speaker 1: that case, we're really talking about the number of clock
Speaker 1: cycles per second, So you get it. This is a
Speaker 1: description of the frequency of the number of times a
Speaker 1: certain thing happens like within a second. And I also
Speaker 1: explained that we measure the rate at which we can
Speaker 1: send data using the term bits. A bit is a
Speaker 1: basic unit of digital information, and when we talk about computers,
Speaker 1: we're talking about bits in the form of a zero
Speaker 1: or a one binary information, just like your basic two
Speaker 1: way physical switch has two positions off or on. So
Speaker 1: if you hear a term like kill a bit, that
Speaker 1: means one thousand bits, and a megabit is one million bits,
Speaker 1: and a gigabit would be one billion bits. Likewise, megabits
Speaker 1: per second tells us how many million bits can move
Speaker 1: from one point to another per second over that connection.
Speaker 1: So if you've got a one hundred megabit per second connection,
Speaker 1: theoretically it would mean that up to one hundred million
Speaker 1: bits can transfer across that communication channel per second, though
Speaker 1: that's not how it works out most of the time,
Speaker 1: but that's a matter for a different episode. I didn't
Speaker 1: mention that this is different from something like megabytes. So
Speaker 1: a byte is a unit that consists of eight bits.
Speaker 1: And this gets confusing because we often describe stuff like
Speaker 1: file sizes in terms of bytes, but transfer speeds in
Speaker 1: terms of bits. So let's say that you do have
Speaker 1: that one hundred megabits per second download speed, and you
Speaker 1: want to download a one hundred megabyte file, well, that
Speaker 1: means it's not going to take one second. It's going
Speaker 1: to take eight seconds to download the file, because a
Speaker 1: megabyte is eight times larger than a megabit. And actually
Speaker 1: even that is a little bit misleading because in computer
Speaker 1: memory terms, we typically look at units of memory based
Speaker 1: on powers of two rather than powers of ten. So
Speaker 1: instead of a kilobyte being one thousand bytes, it's actually
Speaker 1: one thy twenty four bytes. And there's no standardization in
Speaker 1: the tech industry, so sometimes people will say a kilobyte
Speaker 1: and they mean one thousand bytes. Sometimes they'll say killobyte
Speaker 1: and they mean one thy twenty four bytes, and you
Speaker 1: will want to tear your hair out, and then you'll
Speaker 1: look like I do, I'm bald if you didn't know.
Speaker 1: But this episode isn't about the peculiarities of our naming
Speaker 1: conventions and the computer information age. Instead, I wanted to
Speaker 1: tackle something else that affects everything really, but in particular,
Speaker 1: we really had to suss it out in order to
Speaker 1: make certain types of satellites work properly, and this is
Speaker 1: the concept of relativity. So in this episode, we're really
Speaker 1: going to learn why an understanding of relativity is important
Speaker 1: if we want our certain satellite technologies to work, and
Speaker 1: it serves as a great reminder that technology is only
Speaker 1: really possible through an understanding of science. You can think
Speaker 1: of tech as the physical manifestation of our understanding of
Speaker 1: scientific principles, and that means if we were wrong in
Speaker 1: our understanding of science, the technology shouldn't really work. So
Speaker 1: in a way, you can think of technology that works
Speaker 1: as evidence that the scientific method is a darn good formula.
Speaker 1: Since we're talking about relativity, it means we're going to
Speaker 1: be talking about a real Einstein today. His name was Einstein,
Speaker 1: which is convenient. But before we get to Einstein, we
Speaker 1: have Galileo Galileo Galileo figure Ro. Wait No, I'm sorry,
Speaker 1: wait that's Bohemian Rhapsody. I meant Galileo Galilei. This. Galileo
Speaker 1: made an observation that if you've got two observers moving
Speaker 1: at a constant speed and direction, so they're moving at
Speaker 1: the same velocity, they will get the same results for
Speaker 1: any experiment that involves moving stuff around a mechanical experiment.
Speaker 1: This is easier to understand if we use an example,
Speaker 1: and I like one that my colleague Robert Lamb used
Speaker 1: when he wrote about relativity for HowStuffWorks dot com back
Speaker 1: in the day. He used an example of a train
Speaker 1: and a scientific ping pong ball. All right, so imagine
Speaker 1: you've got a scientist who's standing in the middle of
Speaker 1: an aisle on a moving train, and the train is
Speaker 1: moving at a steady speed in a straight line, so
Speaker 1: there are no active forces of acceleration going on here. Remember,
Speaker 1: acceleration describes a force that involves a change in velocity,
Speaker 1: so that either means a change in direction or a
Speaker 1: change in speed, or both. But in this case constant
Speaker 1: speed constant direction. Robert used nice round numbers in his examples,
Speaker 1: so he suggested that the train is moving at one
Speaker 1: hundred miles per hour. Well it's not round. If we
Speaker 1: go to the metric system, that would be one hundred
Speaker 1: and sixty one kilometers per hour. If the train stays
Speaker 1: steady to the scientist, it will feel as if that
Speaker 1: scientist is actually just standing still, just anywhere, and we're
Speaker 1: conveniently ignoring an emotion that would happen due to irregularities
Speaker 1: with the train's wheels or the train tracks or anything
Speaker 1: like that. And if this is hard for you to imagine,
Speaker 1: just think about how you feel when you're standing still
Speaker 1: or sitting still or laying down here on Earth. We
Speaker 1: know the Earth is moving through space. It is a
Speaker 1: body in motion, but when we are still relative to
Speaker 1: the Earth itself, we don't feel that motion. Assuming there's
Speaker 1: not some other weird event going on, like an earthquake,
Speaker 1: which is something separate. But back to our hypothetical train,
Speaker 1: the scientist tosses the ping pong ball down the aisle. Now,
Speaker 1: from the scientist's perspective, this ping pong ball will travel
Speaker 1: at whatever speed they threw it at. Robert actually suggests
Speaker 1: a relatively gentle toss of five miles per hour or
Speaker 1: eight kilometers per hour. The ping pong ball would bounce
Speaker 1: down the aisle, just as it would if the scientists
Speaker 1: were to toss the ball on a train that isn't
Speaker 1: moving at all, or on just flat ground. However, let's
Speaker 1: say we have a second observer who's not on the train.
Speaker 1: They're standing off to the side, and they can see
Speaker 1: through the train. To this person, it will appear as
Speaker 1: if the ping pong ball is moving very fast. Indeed,
Speaker 1: relative to this stationary observer, the ping pong ball will
Speaker 1: appear to move at the speed at which it was
Speaker 1: thrown in addition to the speed of the train itself.
Speaker 1: So if we take the two figures, we would get
Speaker 1: one hundred five miles per hour or one hundred and
Speaker 1: sixty nine per hour. This is called a Galilean transformation. Alternatively,
Speaker 1: if the scientists were throwing the ping pong ball in
Speaker 1: the opposite direction of the train's travel, so they're facing
Speaker 1: toward the back of the train, it would appear to
Speaker 1: this second observer the ping pong ball was moving at
Speaker 1: a slightly slower speed than the overall train was, whereas
Speaker 1: to the scientist on board, the ping pong ball would
Speaker 1: still be traveling at that five mile per hour speed.
Speaker 1: So this is where the term relativity comes into play.
Speaker 1: The effects observed are relative to the perspective of the observer.
Speaker 1: It's all based on the reference frame of that observer.
Speaker 1: If you're on the train, then you're just looking at
Speaker 1: a ping pong ball bouncing at a relatively slow speed
Speaker 1: down the aisle. If you're not on the train, the
Speaker 1: ping pong ball is moving quite fast, so it's all relative.
Speaker 1: Isaac Newton would follow along and say, yeah, mate, this
Speaker 1: all tracks. I don't know why he talked like that.
Speaker 1: In his Laws of Motion, Newton stated that these laws
Speaker 1: of motion should hold in an inertial frame as well
Speaker 1: as reference frame that was moving at a constant velocity
Speaker 1: relative to the inertial frame. An inertial frame, by the way,
Speaker 1: is just a frame of reference in which there are
Speaker 1: zero net forces acting upon it, so that there are
Speaker 1: no forces of acceleration in play. So in our example,
Speaker 1: the train that we talked about, that would be our
Speaker 1: inertial frame. All of this is fairly intuitive, but then
Speaker 1: we get to something really tricky. Einstein would establish that
Speaker 1: the speed of light in a vacuum is the fastest
Speaker 1: speed in our universe. Nothing can go faster than that.
Speaker 1: But hey, what if you're on a train that's traveling
Speaker 1: one hundred miles per hour and you're facing forward, you're
Speaker 1: facing the direction of travel, and then you have a
Speaker 1: flashlight and you turn on the flashlight. Well, doesn't that
Speaker 1: mean you should perform a Galileean transformation on this and
Speaker 1: say the light from that flashlight in your hands is
Speaker 1: actually traveling at the normal speed of light on board
Speaker 1: the train. But also get that boost of the trains travel,
Speaker 1: so it should be the speed of light plus one
Speaker 1: hundred miles per hour. Doesn't that make sense? While according
Speaker 1: to actual experiments performed before Einstein would come around to
Speaker 1: explain things, the answer was Nope, doesn't look like it
Speaker 1: works that way. Scientists Edward Morley and Albert A. Michelson
Speaker 1: created an experiment to measure the speed of light back
Speaker 1: in eighteen eighty seven, and actually they were looking for
Speaker 1: something else. They were looking for evidence of a hypothetical
Speaker 1: substance called luminiferous ether. Say why, all right, we'll stick
Speaker 1: with me, because in a way this does make sense. Okay,
Speaker 1: So on Earth we see waves traveling through a medium, right,
Speaker 1: Like if you look out in the ocean, you can
Speaker 1: see actual waves in the water, and the water is
Speaker 1: a physical medium through which these waves travel. Sound can't
Speaker 1: travel in space because space is effect actively a vacuum.
Speaker 1: The particles that are in space are so far apart
Speaker 1: from one another that there's no way for the vibration
Speaker 1: of one particle to come into contact and affect another particle.
Speaker 1: So sound can't travel. Sound travels through the propagation of
Speaker 1: vibrational waves. And if your stuff isn't in contact with
Speaker 1: each other, there's no way for them to have that
Speaker 1: wave propagate. So there has to be some sort of
Speaker 1: medium like air or solid surfaces or something in order
Speaker 1: for sound travel. Well, if that's the case, said the
Speaker 1: folks of the time, then stuff like light must need
Speaker 1: some sort of medium to travel through, right. I mean
Speaker 1: sound has to have something. Light must have something too.
Speaker 1: Light can definitely travel through space. I mean, that's how
Speaker 1: we can see anything, because light from the Sun travels
Speaker 1: through space to hit the Earth. So the light has
Speaker 1: to be moving through some sort of medium we cannot
Speaker 1: observe directly. This hypothetical medium was the aforementioned maniferous ether.
Speaker 1: But assuming this ether existed at all, it had to
Speaker 1: be pretty darn special because we can't feel it, we
Speaker 1: can't detect it, it creates no observable effects, So if
Speaker 1: it were real, it had to be unlike pretty much
Speaker 1: anything else we had discovered up to that point. Now,
Speaker 1: let's assume that the universe is filled with this ether stuff.
Speaker 1: The question rises, how the heck does the ether interact
Speaker 1: with all the physical stuff that's in the universe, the
Speaker 1: actual matter and also energy. After all, the bodies in
Speaker 1: space like stars, planets, moons and all that other stuff.
Speaker 1: All of that is moving, none of it is standing still,
Speaker 1: and if it is moving, it would presumably disturb this
Speaker 1: ether medium, right. I mean, if you move your hand
Speaker 1: through a pool of water, you are disturbing that water.
Speaker 1: You're making currents and eddies. So it was thought that
Speaker 1: the motion of all these elements in space would disturb
Speaker 1: the ether in some way, and hypothetically there would be
Speaker 1: some sort of ether wind. But if there were a wind,
Speaker 1: then presumably the speed of light would be affected depending
Speaker 1: upon the wind's direction in relation to the light's direction.
Speaker 1: So think of a really windy day in the real world.
Speaker 1: If you're walking against a very very tough wind, like
Speaker 1: a gale force wind, you have to power through it
Speaker 1: to keep moving forward. Now, if you're walking with the wind,
Speaker 1: like the wind is to your back and pushing you,
Speaker 1: then you get a big boost. Well, the same thing
Speaker 1: should be happening with light if ether wind were real,
Speaker 1: and so Mickelson and Morley devised a gadget that would
Speaker 1: split light into two beams, directing those beams down different paths,
Speaker 1: using mirrors in different directions, and seeing if those two
Speaker 1: beams of light would hit an eyepiece at different times.
Speaker 1: The thought being well, one of these directions would theoretically
Speaker 1: be in the same direction as the ether wind, and
Speaker 1: one would be at a cross direction of ether wind,
Speaker 1: So we should see a difference in the amount of
Speaker 1: time it takes for the light from this one source
Speaker 1: that's been split into two to arrive at an eyepiece.
Speaker 1: But that's not what they found. They observed no such effect.
Speaker 1: So if there were such a thing as ether, the
Speaker 1: stuff wasn't giving either a boost or a drag on
Speaker 1: light itself. No matter what. The light was traveling at
Speaker 1: a constant speed, which turned out to be approximately one
Speaker 1: hundred eighty six thousand miles per second or around three
Speaker 1: hundred thousand kilometers per second. Now that flew in the
Speaker 1: face of classic Newtonian physics clearly. With the example of
Speaker 1: the ping pong ball and the train, the ping pong
Speaker 1: ball has to be traveling faster than the train it's on.
Speaker 1: I mean, that just makes sense. If you were standing
Speaker 1: on the top of the very front of the train
Speaker 1: and then you threw the ping pong ball, and we
Speaker 1: ignore stuff like wind resistant, the ping pong ball would
Speaker 1: land ahead of the train, So it has to be
Speaker 1: going faster. So what the heck was so special about
Speaker 1: light and what was going on? Well, this was one
Speaker 1: of the great mysteries that Albert Einstein set his mind
Speaker 1: to unraveling, and it formed the basis of one of
Speaker 1: his great theories of relativity. And this would be the
Speaker 1: theory of special relativity, which poses that the laws of
Speaker 1: physics are in the same in all inertial frames of references.
Speaker 1: And that means the speed of light will be the
Speaker 1: same for all observers, regardless of their relative perspectives. It
Speaker 1: doesn't matter the context. The speed of light is the
Speaker 1: speed of light. Now, there's an implication to this theory
Speaker 1: that really got people scratching their heads. If the speed
Speaker 1: of light is absolutely constant, that would mean that stuff
Speaker 1: like distance and time are not. And as a heck
Speaker 1: of a brain teaser, when we come back, we'll explore
Speaker 1: this more. Let's imagine that you live half a mile
Speaker 1: away from a lovely park, and it's a half mile
Speaker 1: away in the morning, it's a half mile away. At night,
Speaker 1: it's a half mile away. On a Tuesday, it's a
Speaker 1: half mile away. On a Saturday. Half a mile is
Speaker 1: half a mile, right, it's a reliable constant in our lives.
Speaker 1: If it weren't, we could never give directions to anywhere
Speaker 1: because all the measurements and landmarks would change all the time,
Speaker 1: and our world wouldn't make sense the way it does
Speaker 1: to us now. So in our individual experiences, in our
Speaker 1: day to day lives, stuff like distance seems pretty darn
Speaker 1: reliable and fixed. So how dare Einstein come along with
Speaker 1: this theory of special relativity at nineteen oh five and say, well, yeah,
Speaker 1: but see, the speed of light is really the true constant,
Speaker 1: and for that to work, time and distance or space,
Speaker 1: in other word, words, must be somewhat mutable. Einstein positive
Speaker 1: that there is no absolute frame of reference in our universe,
Speaker 1: which means there is no place in the universe that
Speaker 1: is totally stationary. Everything is moving, which means all motion
Speaker 1: is relative. You can't really talk about moving except in
Speaker 1: reference to some other moving thing. So even as we
Speaker 1: sit still and try to meditate, we do so on
Speaker 1: a planet that is hurtling through space. We are in motion.
Speaker 1: We're all moving through space and time, and we all
Speaker 1: have a frame of reference, and each frame of reference
Speaker 1: is just as legitimate as every other frame of reference,
Speaker 1: or I guess you could say, if everybody's super, nobody is.
Speaker 1: I guess I've watched The Incredibles too many times. Well, anyway,
Speaker 1: this particular nineteen oh five theory is called special relativity
Speaker 1: because Einstein's explanation only covered special cases, that being when
Speaker 1: two inertial frames are in constant motion with regard to
Speaker 1: one another, and there can be no acceleration, so the
Speaker 1: motion had to be in a straight line at a
Speaker 1: constant speed. A change in direction or speed would be
Speaker 1: an acceleration, and to cover those instances we would have
Speaker 1: to wait a decade for Einstein to work out his
Speaker 1: theory of general relativity. We'll get to that, but we've
Speaker 1: got a lot more to say about special relativity. So
Speaker 1: Einstein was taking a different approach to the results of
Speaker 1: the experiments done by people like Michelson and Morley. The
Speaker 1: scientific world at large was essentially saying, well, this can't
Speaker 1: be right. These results can't be right. There must be
Speaker 1: something wrong with the experiment or the equipment, because we're
Speaker 1: sure this theory is correct and that ether is there.
Speaker 1: Einstein was taking a totally different perspective. He was saying,
Speaker 1: if we assume the experiments are producing accurate results, then
Speaker 1: it stands to reason that the prevailing theory is flawed
Speaker 1: and we have to figure out what the real explanation is.
Speaker 1: And this is one of those important points in science.
Speaker 1: It's that if your results in your experiment don't meet
Speaker 1: your hypothesis, it's very possible that your hypothesis is wrong.
Speaker 1: Now you need to do multiple experiments to find out
Speaker 1: and to test your equipment make sure there's not any
Speaker 1: errors there that could be causing the issues. But it
Speaker 1: does mean that you need to re examine that hypothesis,
Speaker 1: and at this time the scientific community wasn't really doing that,
Speaker 1: so Einstein did away with the ether. His explanation suggested
Speaker 1: that our observable universe has four dimensions, not that there
Speaker 1: can only be four dimensions, but rather there are four
Speaker 1: dimensions we can detect and observe, and these would be up, down, left, right, forward, backward,
Speaker 1: and then the fourth dimension, which is time. Collectively, those
Speaker 1: three dimensions are space. The fourth dimension is time, and
Speaker 1: we get the space time continuum, this intrinsic relationship between
Speaker 1: space and time or space time continuum, which also gives
Speaker 1: us dozens of Star Trek episodes that would use it
Speaker 1: as shorthand, for things are about to get really weird.
Speaker 1: Einstein positive that the speed of light is measured as
Speaker 1: constant in all frames of reference. And let's think for
Speaker 1: a second. What we mean by speed. Speed is a
Speaker 1: description of how much distance can be covered per unit
Speaker 1: of time. So a speed of one hundred miles per
Speaker 1: hour means that in one hour's time we will cover
Speaker 1: a distance of one hundred miles. That's very obvious. But
Speaker 1: if the speed of light is constant for all frames
Speaker 1: of reference, regardless of how those frames are moving relative
Speaker 1: to each other, that must mean something about space and
Speaker 1: or time is a little wonky. And let's think about
Speaker 1: our train experiment again. If you are aboard a train
Speaker 1: moving at a move one hundred miles per hour in
Speaker 1: a straight line, and you toss a ping pong ball
Speaker 1: straight up in the air, well, it's gonna go straight
Speaker 1: up and come right back down to your hand in
Speaker 1: a nice vertical line. From an outside observer who isn't
Speaker 1: on the train, it would look a little differently. You
Speaker 1: would throw the ball up at one point relative to
Speaker 1: this outside observer, and the ball would appear to move
Speaker 1: not just vertically, but horizontally before coming back down. Now,
Speaker 1: if we repeat this experiment but we use light, we
Speaker 1: really see how it gets confusing. Okay, so now you're
Speaker 1: on a train, but it's going really fast, like let's say,
Speaker 1: half the speed of light. But the speed and direction
Speaker 1: are constant. So you're on this train. You don't feel
Speaker 1: any acceleration forces because you're moving at a constant speed
Speaker 1: and in a constant direction, so your velocity remains the same.
Speaker 1: In fact, if there were no windows on the train,
Speaker 1: you wouldn't even be able to tell that the train
Speaker 1: was moving at all. So let's say you've got a
Speaker 1: laser pointer and you've got a mirror on the ceiling
Speaker 1: of the train and a foton detector on the floor
Speaker 1: of the train. You shoot the laser up at the mirror,
Speaker 1: it reflects off the mirror, and then it comes back
Speaker 1: down and hits the detector on the floor, and it
Speaker 1: registers how long it took the light to travel from
Speaker 1: your laser pointer to hit the detector. And to you,
Speaker 1: the laser makes a vertical line. All that makes sense, right,
Speaker 1: you can imagine that, But for our outside observer who's
Speaker 1: not on the train, it would appear as though the
Speaker 1: laser were actually traveling at a diagonal up to that mirror,
Speaker 1: and then a diagonal back down toward the detector. So
Speaker 1: for one observer, the one on the train, we have
Speaker 1: a straight line. It's vertical up down. For the second
Speaker 1: observer off the train, we have an angled path, sort
Speaker 1: of like how a billiard ball can hit the side
Speaker 1: of a pool table and bounce off at an angle.
Speaker 1: But this creates an apparent paradox. The path viewed by
Speaker 1: you on the train is a straight line, and by
Speaker 1: definition that is the shortest distance between two points. The
Speaker 1: path observed by the person who is not on the
Speaker 1: train is an angled line, and by definition that has
Speaker 1: to be longer. The speed of light is constant in
Speaker 1: both cases, but the distance is different between the two
Speaker 1: points of reference. And because speed is distance divided by time,
Speaker 1: if the distance is different, the time must also be
Speaker 1: different between those two points of reference. Crazy This brings
Speaker 1: us to the concept of time dilation. It also, by
Speaker 1: the way, can affect distance. The faster an object gets,
Speaker 1: the more squished it gets. So if you had this
Speaker 1: train and you were to get up to near the
Speaker 1: speed of light, the train to an outside observer would
Speaker 1: appear to be shorter than it normally would be to
Speaker 1: anyone inside the train, the dimensions would remain exactly the same.
Speaker 1: You would not suddenly see a shorter train. It wouldn't
Speaker 1: be like you were in that compressor scene in Star Wars.
Speaker 1: The train would appear to be normal only from an
Speaker 1: outside observer who is not traveling at that speed, when
Speaker 1: it appeared that the train itself was getting squished shorter. Likewise,
Speaker 1: the faster something goes with respect to some other point
Speaker 1: of reference that's important, the more quickly time appears to
Speaker 1: pass for those at the other point of reference. Or alternatively,
Speaker 1: the more slowly time seems to pass for the fast
Speaker 1: moving thing from the frame of reference of the person
Speaker 1: who's not moving fast. This gets really clunky. I know,
Speaker 1: it gets confusing. So let's talk about space travels some more,
Speaker 1: because examples actually make this way easier to explain. All right,
Speaker 1: So let's say you've built a spaceship and this spaceship
Speaker 1: can go wicked fast, like eighty percent of the speed
Speaker 1: of light, and you're gonna go on a year long
Speaker 1: jaunt out in space, and your best friend is hanging
Speaker 1: back on Earth. Now we now have our two frames
Speaker 1: of reference. We have the spaceship, and then we have
Speaker 1: the person on Earth. So let's ignore accelerative forces for
Speaker 1: the moment because we're gonna have to just focus on
Speaker 1: special relativity. We'll get to general relativity in a moment.
Speaker 1: So you're in your spaceship. You're zooming around at eighty
Speaker 1: percent the speed of light, and for you, time is
Speaker 1: passing normally. The seconds feel like seconds, minutes feel like minutes,
Speaker 1: hours feel like hours, et cetera. And you're on there
Speaker 1: for a full year. Back on Earth, time is passing normally.
Speaker 1: For your best friend who's just hanging out on Earth,
Speaker 1: they feel their seconds pass like seconds. They're minutes passing minutes,
Speaker 1: and so on. However, when we look at the two
Speaker 1: of you in reference to one another, something unusual happens.
Speaker 1: So to your best friend on Earth, it looks like
Speaker 1: time is passing very slowly for you aboard your spaceship.
Speaker 1: To you on your spaceship, it looks like time is
Speaker 1: passing super fast for your friend back on Earth. So
Speaker 1: when you do get back to Earth a year later
Speaker 1: than the two of you enter the same point of reference,
Speaker 1: things are weird. From your perspective, you've only aged a
Speaker 1: year because you spend a year aboard your SPA ship,
Speaker 1: but a little more than a year and a half
Speaker 1: has passed on Earth while you were gone. Your calendars
Speaker 1: wouldn't line up anymore. The faster you go relative to
Speaker 1: your frame of reference, the more pronounced the time dilation. Now,
Speaker 1: I do want to be clear about this, it's not
Speaker 1: really correct to say that as speed increases time slows down.
Speaker 1: You have to always relay this in terms of having
Speaker 1: another frame of reference, because within a single frame of reference,
Speaker 1: time just passes normally. There's no difference. By the way,
Speaker 1: This is also why star dates in the Star Trek
Speaker 1: universe don't make a whole lot of sense. They tried
Speaker 1: to retroactively make it make sense. But keeping time when
Speaker 1: you're on a ship that can travel at the speed
Speaker 1: of light or in the case of Star Trek, magically
Speaker 1: going faster than the speed of light and we won't
Speaker 1: even get into warp speed at all, is crazy. But
Speaker 1: being able to use that and somehow relate it to
Speaker 1: making sense on time passing on planets or space stations
Speaker 1: or whatever. That's a huge mess. But it's also outside
Speaker 1: of our episode, so we'll just leave it at that.
Speaker 1: We don't notice the effects of special relativity in most
Speaker 1: of our day to day lives, because we are not
Speaker 1: traveling fast enough relative to each other for it to
Speaker 1: be a real factor most of the time. But it
Speaker 1: does get even more weird. Were it possible to build
Speaker 1: a spaceship that could travel at the speed of light,
Speaker 1: and you were to take this sort of trip to
Speaker 1: an outside observer, time would appear to stop for you
Speaker 1: aboard your spaceship. Now if assuming this was even possible,
Speaker 1: you would still experience time in your own frame of
Speaker 1: reference as per normal, but your friend back on Earth
Speaker 1: would see that it looked like you were frozen in time. However,
Speaker 1: this is a moot point. Matter cannot travel at the
Speaker 1: speed of light, so it's more of a thought experiment anyway. However,
Speaker 1: we can actually detect time dilation with extremely accurate time
Speaker 1: measurement device like atomic clocks. In fact, we've done it
Speaker 1: in experiments. Scientists have synchronized two atomic clocks, and these
Speaker 1: atomic clocks keep incredibly accurate time down to a matter
Speaker 1: of nanoseconds, and a nanosecond is one billionth of a second,
Speaker 1: So one clock was kept stationary, you know, relatively speaking,
Speaker 1: here on Earth. The other traveled aboard a high speed aircraft,
Speaker 1: and at the end of the experiment they compared the
Speaker 1: two clocks against each other, and the one that was
Speaker 1: aboard the aircraft had measured less time than the one
Speaker 1: that stayed on the ground on Earth. Less time passed
Speaker 1: on that aircraft relative to the amount of time passing
Speaker 1: on the ground. It wasn't just that one clock was
Speaker 1: moving more slowly than the other. Literally less time was
Speaker 1: passing in reference to the other point of from the
Speaker 1: perspective of the other point of reference, that is, the
Speaker 1: difference was right in line with Einstein's calculations. Now, as
Speaker 1: we'll see, this ends up being an important point when
Speaker 1: we get to satellites. But we can't just jump on
Speaker 1: that yet. We do need to take into consideration general relativity. So,
Speaker 1: as i mentioned, special relativity only looks at frames of
Speaker 1: reference that are in a constant and consistent motion with
Speaker 1: regard to one another. There could be no change in
Speaker 1: direction or speed because that introduces accelerative forces and that
Speaker 1: changes things. So to take acceleration into account. Einstein proposed
Speaker 1: his theory of general relativity ten years after his theory
Speaker 1: of special relativity, so this would be nineteen fifteen For
Speaker 1: those who are keeping track, This theory would incorporate the
Speaker 1: force of gravity into Einstein's work, which means factoring in acceleration.
Speaker 1: So in this theory, Einstein introduced the equivalence principle, which
Speaker 1: says that gravity pulling in one direction is equivalent to
Speaker 1: acceleration in another direction. So we can actually experience this.
Speaker 1: It's easy to remember and imagine. Imagine getting on an
Speaker 1: elevator and it's going up, and as it goes up,
Speaker 1: you feel that sense of increased gravity pulling down on
Speaker 1: you as the elevator accelerates. When the elevator is going down,
Speaker 1: you feel a sense of decreased gravity as the elevator
Speaker 1: accelerates downward. So gravity and acceleration are equivalent, which means
Speaker 1: that it can also affect our measurements of space and time.
Speaker 1: Einstein hypothesized that gravity was warping space time itself. Take
Speaker 1: something that's really massive, like a huge dense star, that
Speaker 1: would warp space time around it through its gravity, and
Speaker 1: we can even observe this scientifically, scientists have measured light
Speaker 1: that has curved around massive stars. This is called gravitational lensing.
Speaker 1: Now here's another thing that gets a bit confusing. The
Speaker 1: effects of gravity on time mean that time passes differently
Speaker 1: for objects in orbit when taken in reference to time
Speaker 1: passing on Earth itself, time pass this is faster in
Speaker 1: orbit than it does on Earth. Now, again, this is
Speaker 1: a frame of reference thing, because if you were on
Speaker 1: a spaceship in orbit, your experience of time would feel
Speaker 1: exactly the way it does when you are on Earth.
Speaker 1: It's only when we look at this from two frames
Speaker 1: of reference that we see how it doesn't match up.
Speaker 1: So what does this all mean for satellites. Well, it
Speaker 1: means that satellites in orbit have a couple of different
Speaker 1: relativistic effects going on. In our frame of reference here
Speaker 1: on Earth, satellites are traveling faster than we are to
Speaker 1: maintain orbit, which means that if we compare the passing
Speaker 1: of time in each frame of reference, time would pass
Speaker 1: faster for us than for the satellite. However, due to
Speaker 1: the gravitational effect on space time, we also know that
Speaker 1: something in orbit will have time pass faster for that
Speaker 1: thing than we would experience here on Earth. So it's
Speaker 1: the opposite of the effect of special relativity in a way,
Speaker 1: and the effects of special relie relativity and general relativity
Speaker 1: don't actually cancel each other out, which means ultimately that
Speaker 1: time on a satellite and time down here on Earth
Speaker 1: are not syncd up with reference to one another. And
Speaker 1: for some types of satellites that's a problem. I'll explain
Speaker 1: more after we take this quick break to understand why
Speaker 1: relativity is important with certain satellites, let's talk about the
Speaker 1: Global Positioning System or GPS. Now, this is the satellite
Speaker 1: system that provides data back to Earth that makes it
Speaker 1: possible to get precise coordinates using a GPS receiver. So
Speaker 1: how does that work? Well, here on Earth, you could
Speaker 1: get a very imprecise idea of your general coordinates through
Speaker 1: a trilateration using signals from cell phone towers. This works
Speaker 1: on a fairly simple principle. So we know that the
Speaker 1: radio signals sent to and from cell phones travel at
Speaker 1: essentially the speed of light. So if a cell phone
Speaker 1: tower broadcasts out a short command that just requests your
Speaker 1: phone to respond back with a quick response a ping.
Speaker 1: In other words, the amount of time it would take
Speaker 1: for the ping to reach the cell tower could be
Speaker 1: used to work backward and figure out how far away
Speaker 1: the phone is from that cell phone tower. Because you
Speaker 1: know the speed of travel, right is the speed of light,
Speaker 1: so you also know how much time it took. That
Speaker 1: means you can work backward to figure out the distance
Speaker 1: between those two points. However, that's just a distance, there's
Speaker 1: no direction there. Now, if you did this with multiple
Speaker 1: cell towers, the collective data from those towers could be
Speaker 1: used to get a rough estimate of where the phone is.
Speaker 1: So let's imagine we've got a map, and on that
Speaker 1: map we've got three cell towers A, B, and C.
Speaker 1: You can see exactly where each one is. And let's
Speaker 1: say that you've got a phone that located somewhere within
Speaker 1: the broadcast range of those three cell towers. Each tower
Speaker 1: sends a ping to your phone, Your phone responds with
Speaker 1: a ping back, and you are given the amount of
Speaker 1: distance between your phone and each of those three towers. Well,
Speaker 1: Tower a's result says that you are a mile away
Speaker 1: from Tower A, so you actually have to draw a
Speaker 1: full circle around Tower A to represent all the possible
Speaker 1: points you could be that are one mile away from
Speaker 1: Tower A, So you're drawing a mile radius around Tower A.
Speaker 1: Tower B responds that you're within one point five miles
Speaker 1: of Tower B, so you have to draw a circle
Speaker 1: around Tower B to represent all the points where you
Speaker 1: could be that are a mile and a half away
Speaker 1: from it. Now, the circle from tower B in the
Speaker 1: circle from Tower A should intersect each other at two points,
Speaker 1: but that means you could be at either of those
Speaker 1: two points. Right, you could be at either overlap, so
Speaker 1: you don't have enough information yet. By coordinating with tower C,
Speaker 1: and let's say that one tells you you're within two miles,
Speaker 1: you can draw a third circle, and the point where
Speaker 1: all three circles would meet would be your general location.
Speaker 1: It's not incredibly precise, but it does give you an
Speaker 1: idea of where you are. The GPS constellation of satellites
Speaker 1: does something similar, only we have to think of this
Speaker 1: in terms of three dimensional space rather than a two
Speaker 1: dimensional map. So a satellite sends out a high frequency,
Speaker 1: low power radio signal and receivers pick that signal up.
Speaker 1: The receiver, let's say it's your smartphone, doesn't have to
Speaker 1: send data back up to the satellite, which is good
Speaker 1: because i'd be an enormous drain on your smartphone's power.
Speaker 1: So really it's just listening for these signals. Now, the
Speaker 1: receiver and satellite both run the same digital pattern relative
Speaker 1: to a specific time stamp. It's easy if we think
Speaker 1: of this as midnight. So let's say that midnight hits
Speaker 1: and and this particular digital pattern starts both on the
Speaker 1: satellite and the receiver, so they're both running the exact
Speaker 1: same pattern. The satellite beams out a signal carrying this
Speaker 1: digital pattern. The satellite is far away, so it takes
Speaker 1: a little time, you know, not much, but a little
Speaker 1: time for that signal to get to your receiver. And
Speaker 1: the lag between the pattern that's playing on your receiver
Speaker 1: and the signal of that same pattern coming in from
Speaker 1: the satellite tells the receiver how far away it is
Speaker 1: from that particular satellite, because again we know that the
Speaker 1: signal is moving at the speed of the transmission itself,
Speaker 1: and that's the speed of light, and that's a constant.
Speaker 1: So now the receiver knows how far away it is
Speaker 1: from that one satellite. And because the orbits of these
Speaker 1: satellites are predictable, the receiver has a record of where
Speaker 1: that satellite should be relative to your surface. Occasionally we
Speaker 1: have to tweak that record because stuff like gravity can
Speaker 1: pull a satellite slightly out of position over time, so
Speaker 1: that actually is something that has to be a rest
Speaker 1: on occasion. Now, this receiver will do this with at
Speaker 1: least four satellites the Y four and not three, and
Speaker 1: I gave the three cell phone tower examples. Well, it's
Speaker 1: because the clocks on satellites and the clock that's running
Speaker 1: on the device that the receiver is built into may
Speaker 1: not be and really aren't truly synchronized. And the intersection
Speaker 1: of for spheres of distance like these four spheres representing
Speaker 1: the various ranges that these satellites are finding themselves in
Speaker 1: with regard to this receiver can only intersect at one point.
Speaker 1: That's the only place they could all intersect. So if
Speaker 1: a GPS receiver's clock is not matching up to the
Speaker 1: clocks on the satellites, there will be no intersection at all.
Speaker 1: And the receiver will say, well, I can't find an intersection,
Speaker 1: so that I know that means my clock is off
Speaker 1: from all the other clocks, and it will then adjust
Speaker 1: its own clock to be an alignment so that the
Speaker 1: or spheres have a point of intersection and that is
Speaker 1: your location on Earth. Now, in order for our receivers
Speaker 1: to be able to do this, the accuracy of the
Speaker 1: atomic clocks aboard those GPS satellites has to be accurate
Speaker 1: within twenty to thirty nanoseconds. And remember a nanosecond is
Speaker 1: one billionth of a second. That is an astounding level
Speaker 1: of accuracy. And because these satellites are in motion and
Speaker 1: they are also affected by Earth's gravity, they are subject
Speaker 1: to the effects of special and general relativity, and this
Speaker 1: means we actually have to make calculations to take that
Speaker 1: into account. Now, according to special relativity and the relative
Speaker 1: speeds of satellites to a fixed point on the surface
Speaker 1: of the Earth, we would expect the atomic clock aboard
Speaker 1: that satellite to register seven fewer microseconds per day than
Speaker 1: a clock on Earth because these satellites are moving through
Speaker 1: space faster than we are, relatively speaking, so that means
Speaker 1: from our frame of reference, time is passing more slowly
Speaker 1: on that satellite than it does here on Earth. Ah.
Speaker 1: But general relativity comes into play too, and general relativity
Speaker 1: tells us that the Earth's gravity warps space time around
Speaker 1: our planet. And one of general relativity's predictions is that
Speaker 1: a clock closer to a massive object, so like a
Speaker 1: clock here on Earth, will tick more slowly than a
Speaker 1: clock that is further out from that same massive object.
Speaker 1: So the closer the clock is to the massive object,
Speaker 1: the less time it will experience it will measure compared
Speaker 1: to a clock that's further away, which is crazy, right.
Speaker 1: So taking only general relativity into account, we would see
Speaker 1: that a clock aboard one of these satellites would register
Speaker 1: more time having passed on that satellite than a clock
Speaker 1: here on Earth, meaning for our frame of reference, time
Speaker 1: is actually passing faster on those satellites than it does
Speaker 1: here for us. This would come out to about forty
Speaker 1: five microseconds a day, meaning that at the end of
Speaker 1: day one, the clock aboard that satellite would be ahead
Speaker 1: of a clock here on Earth by forty five microseconds,
Speaker 1: and this would continue day after day, with the gap
Speaker 1: growing wider every single day. Now, when we bring both
Speaker 1: special and general relativity together into consideration, we see that
Speaker 1: they don't just cancel each other out right, because we've
Speaker 1: got that seven microsecond lag due to special relativity, but
Speaker 1: we have the forty five microsecond surge due to general relativity.
Speaker 1: So in the end, we're looking at a thirty eight
Speaker 1: microsecond difference per day between a clock on a satellite
Speaker 1: and a clock here on Earth. The clocks on the
Speaker 1: satellites will get ahead of similar clocks here on Earth
Speaker 1: by thirty eight microseconds every single day. And while a
Speaker 1: microsecond is a very small amount of time, I mean
Speaker 1: we're talking at a level that we don't typically experience.
Speaker 1: We don't think of time in microseconds for our day
Speaker 1: to day lives. However, thirty eight microseconds is equal to
Speaker 1: thirty eight thousand nanoseconds, and if you're looking for an
Speaker 1: accuracy of around twenty to thirty nanoseconds, this becomes an
Speaker 1: enormous problem if we don't take it into account. And
Speaker 1: this brings us back round to something I mentioned at
Speaker 1: the top of the show. We know that Einstein was
Speaker 1: right about relativity because we have to account for it
Speaker 1: with technology like GPS. If we didn't take it into account,
Speaker 1: if we didn't factor in the effects of relativity, our
Speaker 1: GPS wouldn't work for very long at all. Our technology
Speaker 1: proves that the science is real, or else the tech
Speaker 1: would fail at what it needs to do now. In general,
Speaker 1: I think that's a great lesson to take home. There
Speaker 1: are a lot of voices out there that call science
Speaker 1: into questions, and some of them are more outlandish than others,
Speaker 1: a person who's passionately and sincerely arguing that the Earth
Speaker 1: is flat seems pretty far out there for me, because
Speaker 1: so much of our technology we've built upon and we
Speaker 1: rely upon wouldn't work if that were true. Even if
Speaker 1: you can't experience something directly, such as having a meaningful
Speaker 1: experience of time dilation, a ton of the stuff we
Speaker 1: do experience on a day to day basis is affected
Speaker 1: by this stuff, and it proves the existence and also
Speaker 1: the benefits of having the scientific method. Now I'll give
Speaker 1: a little side note on GPS to kind of wrap
Speaker 1: this up. The original GPS configuration came out of a
Speaker 1: United States Department a defense project. The original purpose was
Speaker 1: to provide positioning information for government and military, but specifically
Speaker 1: the United States and its allies, and for that reason,
Speaker 1: the US government wished to restrict access to this technology.
Speaker 1: The general line of thought was that it be better
Speaker 1: if the US didn't allow tech that could, you know,
Speaker 1: give precise coordinates for stuff like military bases or the
Speaker 1: position of various military units to people who didn't belong
Speaker 1: to those divisions. So, as a matter of national security,
Speaker 1: the US guarded this technology civilian receivers. So if you
Speaker 1: went out and you bought a GPS receiver, you could
Speaker 1: get public GPS signals, but the United States was purposefully
Speaker 1: instituting a policy called selective availability, which was an intentional
Speaker 1: degradation of public GPS signals. They were introducing errors on
Speaker 1: purpose so that GPS receivers couldn't get an accurate location.
Speaker 1: It limited accuracy to around fifty meters horizontally and one
Speaker 1: hundred meters vertically, and effectively that meant that you wouldn't
Speaker 1: really know your precise coordinates. You certainly couldn't use a
Speaker 1: GPS receiver as a turn by turn directions tool because
Speaker 1: you wouldn't even necessarily show up on the right street.
Speaker 1: You wouldn't know if you were approaching your turn or
Speaker 1: if you had already passed it. It was it was
Speaker 1: not practical for that. It was only in the year
Speaker 1: two thousand, when US President Bill Clinton directed the government
Speaker 1: to end selective availability, that civilian GPS receivers could actually
Speaker 1: get accurate data. And that's what made the modern GPS
Speaker 1: receivers and stuff like our phones possible. So before two thousand,
Speaker 1: GPS receivers didn't work very well for the average person,
Speaker 1: but it wasn't because the technology was bad, or that
Speaker 1: the science was wrong it worked that way, or if
Speaker 1: you prefer it, it didn't work properly on purpose. And
Speaker 1: that wraps up this episode about relativity and why it's
Speaker 1: important with technology, and it's not just satellite tech, but
Speaker 1: that's a big one, and it also ends up being
Speaker 1: a big thorn in the side for science fiction authors
Speaker 1: who want to write about interstellar travel at faster than
Speaker 1: light speeds, because you have to start finding alternative X
Speaker 1: nations for how that's possible, because we've come up against
Speaker 1: these limits that Einstein predicted, and so far his predictions
Speaker 1: have held true. So in order to travel faster than
Speaker 1: the speed of light, you do have to create something
Speaker 1: like warp drive, which theoretically warps space around you. So
Speaker 1: rather than traveling faster than light, you're decreasing the distance
Speaker 1: between your point of origin and your destination. It would
Speaker 1: be kind of like taking a map of the United
Speaker 1: States and saying I'm going to travel from Atlanta to
Speaker 1: Los Angeles, from one coast to the other, but instead
Speaker 1: of drawing a line from Atlanta to LA you just
Speaker 1: fold the map so that the two dots are next
Speaker 1: to each other, and then you draw a line that way.
Speaker 1: That's how warp speed is supposed to work, because it's
Speaker 1: the only way you can get around the fact that
Speaker 1: you can't really go faster than the speed of light.
Speaker 1: But that's a topic for another show. If you guys
Speaker 1: have suggestions for future topics I should tackle, please let
Speaker 1: me know. Send me a message on Twitter. The handle
Speaker 1: is text hsw and I'll talk to you again really soon.
Speaker 1: Tech Stuff is an iHeartRadio production. For more podcasts from iHeartRadio,
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