Welcome to Tech Stuff, a production from iHeartRadio. Hey there, and welcome to tech Stuff. I'm your host Jonathan Strickland. I'm an executive producer with iHeartRadio and how the tech are here. It is time for a classic episode. This one is called How Lego Works. Originally published on February twenty fourth, twenty sixteen. This was really cool because this came out shortly after we were learning about how Lego had detected gravitational waves, which up to that point had largely been a hypothetical concept. So this was one of those things where we finally figured out a way to detect something that had been hypothesized about but previously undetected, So really cool use of technology. Then the Ligo Observatory had picked up a gravitational wave, and this was huge news around the world. And in case you were wondering, what the heck is this news all about? How did they pick up that gravitational wave? What exactly is the technology powering our sensors to detect this stuff? How does it all work? That's what this episode's all about. So this was the very first time anyone had been able to measure a gravitational wave directly So today we're going to talk all about what that means and how it happened. Now, to begin with, we need to lay some groundwork and to really get an understanding of what gravitational waves are. So gravitational waves ultimately were one of the predictions made by a certain Albert Einstein with this theory of general relativity. So in that theory, Einstein presented this idea that our universe is filled with spacetime. If you're a fan of science fiction, you have undoubtedly come across that term star trek is all about the spacetime continuum, and that you've got to be careful. You could rip a hole in the fabric of spacetime. As far as we know, that's not really that possible. I mean, black holes could sort of be that maybe, But at any rate, spacetime itself is this calling it stuff is probably the wrong way of putting it, but it is like a fabric and mass hangs inside this fabric, And by mass, i'm talking about stuff like stars or even an entire solar systems or galaxies that hang in this fabric, and just like you would see in a two dimensional display, it ends up curving the fabric around the mass. We often talk about this in terms of a very simple example that's easy to imagine. You get some sort of stretching material. Often you'll just hear someone say, okay, get a trampoline. You've got a trampoline, and you put a big, heavy bowling ball on the trampoline. So that bowling ball is going to deform the trampoline surface. It's no longer going to be straight. It's going to end up curving around the bowling ball to some extent, creating kind of a dmple where the bowling ball has has created this impression inside the trampoline, and as long as the bowling ball is there, that impression is going to stay. This is sort of the like the way spacetime curves around giant masses like stars and black holes things like that. Of course, we have to remember that spacetime is actually four dimensional, not a two dimensional thing like a trampoline. I mean, I know that trampolines technically have three dimensions, but we're really looking at a surface, so it's more like a two dimensional plane. In reality. In spacetime it's four dimensional because you've got the three spatial dimensions plus time, and that is a little difficult to get your head around. But that's why we tend to look at this two dimensional example. It's a lot easier for us to imagine. So let's go a little further with that analogy to kind of talk about gravity. See Einstein proposed that gravity was a manifestation of this curved space time. And if we take that trampoline example, Let's say that you have a regular trampoline. You haven't put the bowling ball on there yet, so it's a nice flat surface, and you have a marble, and you roll the marble across the surface of the trampoline. So if there's nothing else there, and if the trampoline is level, if the surface is level, the marble should just roll in the straight line from one side of the trampoline to the other, no problem. Now let's say you put that big, heavy bowling ball on the trampoline. It creates that dimple, and then you try and roll the marble across the trampoline surface. Well, now that dimple is going to end up affecting the pathway of the marble. It's going to start to spiral inward toward the bowling ball. Ultimately it'll end up making contact with the bowling ball, and Einstein said, that's essentially what gravity is. It's that you've got these large masses that curves spacetime to the extent that smaller masses are spiraling inward toward the large mass. It's just happening on a scale that's much much, much larger than any bowling ball, marble example. But that this isn't essentially what we see when we see planets orbiting a sun, or we see a moon orbiting a planet, or we see star systems orbiting a galaxy, you know, the center of a galaxy, and it's all because of this curve spacetime. Now, all of that already is pretty heavy stuff. And keep in mind, there was not really any way to directly observe this. It was mostly the the just Einstein using logic to work all this out and math, logic and math, and ultimately it fit with what we saw of the universe. But we weren't able to test a lot of this. But then it gets even more mind blowing because now we have to get to gravitational waves. So Einstein said that if a mass were large enough and either changed shape rapidly enough or it changed its movement in some way, really really quickly. It would cause ripples of space time to move outward from that event at the speed of light. And those ripples are what we call gravitational waves, which are different from gravity waves. By the way, I have been known to accidentally say gravity waves instead of gravitational waves, but the two are different things. A gravity wave is a wave that exists because of gravity. In other words, it's a physical wave of some sort of fluid system, whether it's atmosphere or water or some other liquid. That's a gravity wave on a planet's surface. It's not the same thing as a gravitational wave, which is really a ripple of space time, and like I said, it moves outward from that event at the speed of light. And stuff that could cause significant gravitational waves, things that would be big enough for us to potentially pick up here on Earth if we had the right equipment, would include things like two black holes orbiting or colliding with one another, which in fact, that was the event that we were able to pick up with the Ligo facilities. And I'll talk about those in just a bit. But there could be other stuff too, like neutron stars orbiting one another fast enough would generate gravitational waves, or a supernova explosion would create one as well. And each of these events give off a huge amount of energy, and some of that energy gets converted into making these gravitational waves. So one takeaway from this prediction something that Einstein said would happen, is that any event that produces gravitational waves is an event in which energy is being lost, So you would expect to see less energy within that system afterward than before. And it would be a hundred years from the time of publication of the theory of general relativity to the time when scientists announced that they had detected a gravitational wave directly. And that's because gravitational waves are devilishly difficult to detect. And that's some alliteration for you right there. So gravitational waves are invisible. They don't emit any sort of electromagnetic radiation, so we can't see them. We can't detect them with radio detectors, nothing like that, and that makes it pretty tricky to figure out where they are. But they do just pass through the universe. They don't get absorbed or scattered the way electromagnetic radiation does. If you hold up a mirror and light hits the mirror, light will bounce off the mirror. That's not the case with gravitational waves. They pass right through, so it's a very different thing than electromagnetic radiation. And while they're generated from enormous events, the gravitational waves aren't very strong. By the time they get to Earth. They are pretty weak, so weak that you would need an incredibly sensitive tool in order to pick them up. And also you have to be searching at the right time, because if the event that generated the gravitational waves happened a billion years ago, but the location is four billion light years from Earth, then we would have to wait another three billion years for those gravitational waves to get to us, because again, they travel at the speed of light. That's their limit. So you have to be at the right place at the right time to pick these things up, and in some cases you might argue that that's incredibly fortuitous. Although to be fair, it looks like the events that could generate gravitational waves happen pretty frequently throughout the universe. But the universe is huge, so if they're happening far away, far enough away, will take a very long time for that information to get to us. So before the announcement on February eleventh, twenty sixteen, scientists had observed phenomena that supported the existence of gravitational waves, but were not direct observations of a gravitational wave. Here's an example. A pair of astronomers in Puerto Rico in the nineteen seventies noticed that there was a binary pulsar system and they went back to the theory of general relativity because this was a sort of system that would be exactly the type to generate gravitational waves according to the predictions from general relativity, and because general relativity predicted, hey, if it can create gravitational waves, it's going to lose energy over time, they ended up coming up with the hypothesis that, well, over time, this binary pulsar system should start to slow down because it's losing energy. It can't keep up at the speed it's going. So they decided to keep an eye on it. And by keeping an eye on it, I mean they continue to observe this pulsar system over the course of eight years, and by the end of the eight year period, they were comparing the findings they were observing to the predictions made by general relativity, and they were matching up. It was unfolding exactly the way Einstein predicted it should unfold based upon his theory of general relativity, which is incredible when you think about it, that the observations are matching up so neatly against the predictions. You know, it just shows how how keenly aware Einstein was of how our universe appears to work. Keeping in mind that general relativity, while an amazing idea collection of ideas, really it doesn't encompass everything that we know, right. It doesn't really address quantum mechanics, for example, at least not in a way that incorporates it with classical physics. But based upon what it did cover, it seems like it was an incredibly accurate theory, all right. So this was really considered strong but indirect support of gravitational waves, because again the astronomers didn't observe gravitational waves directly. They couldn't see them or detect them, but they could see the effects, and again it was matching up with the predictions made from general relativity. So it was good indirect evidence that gravitational waves existed. Then there was an event a couple of years ago that you might have heard about when a team of researchers working on the BICEP two telescope, which is an Antarctica had announced that they thought they might have discovered evidence of gravitational waves that supported a hypothesis called cosmic inflation. That's a lot of information right there, So let me explain what all that means. Cosmic inflation is a hypothesis that relates to the Big Bang theory. So, with the Big Bang theory, you've got this event in which the universe undergoes a period of rapid expansion. Cosmic inflation is kind of that rapid expansion on steroids. The idea being that, well, when we look at our universe and we look at what we can observe, it appears that our observations don't quite match up with what we would expect if we had just steady expansion since the Big Bang. In other words, we look at all the information we have available to us, and it looks to us that it doesn't quite match up. Something's got to be wrong. Well, one possible explanation is that shortly after the Big Bang, and by shortly, I mean tend to the negative thirty sixth power seconds after the Big Bang, So you take a ten, you put a decimal point behind the ten, then you move the decimal point to the left thirty six times that you put seconds behind that. We're talking a fraction of a fraction of a fraction of a second. The universe underwent massive expansion, and it only lasted from that point to about ten to the negative thirty third power or thirty second power seconds. So again an instant. It's completely unimaginable, at least for myself, how short an amount of time this was. But that's how quickly the universe expanded significantly, and then it slowed, but it continued to expand. Now, if in fact, cosmic inflation is correct, it solves a lot of the problems we have between the what we observe today and what we believe happened with the Big Bang, and reconciles those differences. If cosmic inflation is wrong, then something else that we believe is wrong. Right. It means that what we observe either isn't representative of reality somehow we're not getting a big enough picture to understand it, or that the Big Bang theory itself is flawed in some fundamental way. Hey, we'll be back with this heavy subject of detecting gravitational waves with LEGO after this short break, so the BIS of two team what they were looking for was some evidence of gravitational waves that would have been generated during the Big Bang. This would end up supporting the cosmic inflation hypothesis. And the way they did this was they were looking at the cosmic microwave background or CMBAM. Now, the cosmic microwave background emerged about three hundred eighty thousand years after the Big Bang. This was still a period where the universe was so dense that I could not pass through it. It was dark and dense, but the cosmic microwave background formed around that time, and the hypothesis stated, well, gravitational waves would have affected the cosmic microwave background, polarizing some of those some of those particles really not particles, but some of that energy polarizing some of the cosmic microwave background in such a way that if you were to observe it, you could see the effect of a gravitational wave passing through the cmb And then as the universe expand expanded, rather that mark would also expand. It's kind of like imagine leaving a fingerprint on some sort of stretchy material and then stretching that material out, the fingerprint is still there. It's deformed, but still there. That's what the BICEP two team was looking for, was this pattern in the CMB that would indicate that gravitational waves from the Big Bang had passed through, and if they found that, that would be a huge support for cosmic inflation. And in the spring of twenty fourteen, they announced that they believed they had found such evidence, and they also invited other researchers to take a look at their data and see if it was verifiable or maybe they overlooked something. And in the fall of twenty fourteen, another team said, we're sorry, but it looks to us like space dust might have created a false positive that what you thought it was the polarized CMB that you had been looking for was actually just space dust that's not actually part of the CMB. And so that ended up kind of putting a dampener on the whole celebration of finding gravitational waves to support cosmic inflation. But even if it was completely verified, even if BICEP two had irrefutable evidence that they had found the presence of gravitational waves through a you know, the way it affected the CMB. Even then that's not direct detection. It's still indirect. You're looking at the way it's affected something else. So you know, again we're still not discovering one. And part of that is that BICEP two is a telescope. It's looking at through the electromagnetic spectrum, and again, gravitational waves don't show up that way. So no telescope would help you find a gravitational wave directly. You might be able to find how it affected something else, but not the wave itself. Now that's not the case with the LIGO observatories. Actually it's technically one observatory, but it has four different facilities, two detectors and two research facilities that are all part of the LIGO observatory. LIGO itself is an acronym and it stands for Laser Interferometer Gravitational Wave Observatory. So it's a pair of giant detectors built on the surface of the Earth. One is located in Hanford, Washington, the other is in Livingstone, Louisiana. Now they're about just a little under two thousand miles apart, or just over three thousand kilometers apart from each other, and that's really important. I'll explain why in a little bit. So to understand how they work, we also have to talk about something else that gravitational waves do as they pass through space. They stretch and compress space itself. So again, if you were if you were to take a piece of elastic, I'd say, you've got a rubber band, a nice thick rubber band, and you cut it so that it's just one strip. When you pull on that rubber band, it stretches along the line where you're applying force, So it stretches in that direction, in the perpendicular direction ninety degrees from where you're pulling. It compresses, it gets more narrow, and then when you let it return to its normal shape, it gets you know, the long part ends up getting shorter and the narrow part ends up getting wider as a result, gravitational waves do this to reality. They do this to actual space. They stretch and compress, and it happens several times as the wave oscillates through. Really I should just say as the wave passes through, rather than oscillates. The distortion oscillates, but the wave passes through, so That means the actual distance changes between two points as that gravitational wave passes through that area. So if we were to magnify this effect, and I mean magnify it to a ludicrous degree, you would be able to see it. You would actually be able to witness this. You could stand ten feet away from someone else and when the gravitational wave passes through, it would make it look like the two of you suddenly got further away and then closer to each other, and then further away and closer to each other, even though you haven't moved anywhere, because the distance itself is stretching and compressing. So why don't we see that? I mean, if these celestial events that produce gravitational waves happen on the order of something like every fifteen minutes, why are we all noticing this whibbly wobbly effect. Well, it's because the actual distortion that happens here on Earth is much much much smaller in magnitude, so much more so much smaller that it's difficult to even explain. But if you were to have a supernova explode in the Milky Way galaxy, in our galaxy, the gravitational waves generated by that explosion would maybe be powerful enough to distort the distance between the Earth and the Sun by about the diameter of a hydrogen atom, so not noticeable to any degree, and not at least to human senses. So if you were to even go on a smaller scale, let's say that you pick two points that are a kilometer apart here on the surface of the Earth, the amount of distortion would be equivalent to a few thousandth of the diameter of a proton, So you're talking about a subatomic particle, and just a tiny, tiny, tiny fraction of that subatomic particles diameter would be the amount of distortion that would happen across a kilometer worth of distance here on Earth. Again, that means it's so small that it's incredibly difficult to detect, so much so that Einstein himself was pretty sure we would never be able to directly detect gravitational waves because he could not imagine a system that would be sensitive enough to pick up such a minute change, a distortion that's happening so quickly because it's a fraction of a second, and it's so small as to be unnoticeable. So the other problem here is not just that it's such a very tiny effect that lasts a short amount of time. It's also that a lot of other stuff could create false positives. You can have incredibly instrumentation, but if that instrument is really really sensitive, any sort of interference could set off and you could end up getting false readings. So a change in air pressure or temperature, or seismic activity, even a heavy truck driving nearby could set off false results. So you'd have to come up with a really clever way to measure distortion, to limit vibration, and to eliminate the chance that it was a false positive. And Lego is the answer to all of that. So the Lego Observatory is actually the result of decades of collaborative work among different scientific research centers and internet national bodies and universities, and all started back in nineteen seventy nine. That's when the National Science Foundation approved funds for Caltech and MIT to develop laser interferometer research and development. And a few years later, in nineteen eighty three, Caltech and MIT submitted a proposal for a kilometer scale detector. But keep in mind, all right, so in nineteen seventy nine you get the funding for R and d nineteen eighty three, there's the submission of a proposal for a kilometer scale detector. There wouldn't be approval for a detector until nineteen ninety, so almost a decade later, and which turns out was probably okay, because we really didn't have the technological ability to detect things on a scale small enough to register a gravitational wave in the first place. But still, you know, a decade's delay before you even get approval is still pretty rough. Construction didn't begin until nineteen ninety four. The inauguration of the Ligo Observatory took place in nineteen ninety nine, but even then that didn't mean that the observatory was online collecting data. It didn't do that until two thousand and two. And here's the kicker. Eventually scientists came to the conclusion that this Ligo observatory was not sensitive enough to detect gravitational waves. That despite the fact that it was this large detector or pair of large detectors, actually because again one in Louisiana one in Washington, it wasn't sensitive enough to be effective. So it was not quite back to the drawing board, but it did mean that they had to think about how they would upgrade these facilities so that they could be sensitive enough to pick up a gravitational wave. So in twenty ten, Ligo went offline to undergo a big overhaul, and it took four years of construction and testing to get it into shape and another year to set it up for new observations, which means that it wasn't until twenty fifteen that it was ready to come back online. By now it was called the Advanced Ligo Observatory and it began collecting data in September twenty fifteen. Literally days after it had come online, it picked up a gravitational wave. So that's pretty phenomenal that just a couple of days, just a few days really after it had been turned on again in twenty fifteen, we got a hit. So that was incredibly exciting. So how did this happen? How does it actually work? Well, we have to take a look at what interferometers are all about. An interferometer uses a technique in which electromagnetic waves are superimposed on one another in order to get information. Now, Ligo does this with a laser beam because it's a laser interferometer, and the laser beam gets shot through a beam splitter, and the beams, the two beams that result go down two long vacuum tubes. So both of the Lego detectors are in an L shape. So you've got these long, long vacuum tubes that extend two and a half miles or about four kilometers out from the crux from the angle where they meet up, and each one is you know, they're both the same length. They have to be exactly the same length. And the way this works is that kind of behind the crux, you've got a laser that shoots out a beam of light to a beam splitter. The splitter does exactly what it sounds like. It does. It splits the beam into two separate beams with alternating canceling wavelengths. I guess I should say, so the troughs and peaks on one match up with the peaks and troughs of the other. That's really important when we get a little further down the line here. So one of those two beams goes down one branch of this L shaped detector. The other beam goes down the other branch. And keep in mind, like I said, both of these branches are exactly the same length. Two and a half miles or four kilometers. When the laser gets to the end, they hit a mirror. Each beam hits a mirror, they come back to the point of origin, and because the two laser beams have these counteracting wavelengths, they cancel each other out, so the peaks on one cancel out the troughs of the other, and vice versa. That means that no light gets emitted through this system. And that's important because there's actually a light detector that's part of this system as well. It's looking for any sign of laser light, because a sign of laser light would say that something has changed somehow the distances between these or the distances represented by these two vacuum tubes has changed, and that would be indicative of an event like a gravitational wave moving through. So if any light shines through, you know something has happened. Essentially, it says that there's a mismatch in the lengths of the vacuum tubes themselves. So when a gravitational wave passes through, one vacuum tube will get shorter while the other gets longer. And that's because the two tubes are offset by ninety degrees, so one is going to be along one side of the wave and that will lengthen the other will be along will be perpendicular to that, and will shorten as a result. And this means that the lasers will have different distances to travel down, So the laser traveling the shorter distance takes less time to get back to the crux. The laser going down the longer distance takes more time. And even though this is only happening within a fraction of a second, it's long enough for us to be able to detect the difference. And it also means that those wavelengths don't match up anymore, they don't cancel each other out anymore. So some of that laser light gets emitted to the light detector, which then indicates what's going on. It knows which one of the branches was short versus long, and knows how long it happened. It knows how much it oscillated back and forth, because obviously this is continuing as these as the gravitational wave moves through, So you collect a lot of data in a short amount of time. And we're talking like teeny tiny slices of a second. As we're getting all this information, which is pretty incredible. We're almost done with our discussion about LEGO, but before we can do that, we need to take one more quick break. So once you get all that data, you can then analyze it. Actually, more importantly, before you analyze it, you have to verify it. Now. This is why it's important that there are two detectors, and it's also important that they are so far apart, like three thousand kilometers apart from each other. That's because if you get a blip on one of them, if it's a true gravitational wave, you should also get a blip on the other one. And because gravitational waves move at the speed of light, there should be a slight difference in time when both detectors pick up on this gravitational wave, somewhere right around ten milliseconds or less. In the case of the one that was detected back in the fall of twenty fifteen but not announced until twenty sixteen, it hit the Louisiana detector first, and seven milliseconds later it hit the Washington detector, So that is indicative of something like a gravitational wave as opposed to some local event that would have caused interference and created a false positive. If an earthquake had happened in Washington, then the facility may may have picked something up, but you wouldn't expect to see it in Louisiana because it was a localized event. Same thing is true if something had happened in Louisiana. So by seeing it happen at both within this ten millisecond timeframe meant that it was a very good candidate for a gravitational wave passing through. And that's exactly what happened. It was a home run in the first ending of the game, or even really the first at bat of the game. It's like your first player steps up on the first day of baseball and knocks a home run and that defines the moment the season. Really, that's that's the equivalent of what we saw here on a scientific basis. So the other thing I want to talk about was how LEGO tries to minimize the possibility of detecting a false positive in the first place. So, yeah, false positives are something that they worry about, and the fact that there are two detectors helps minimize that. But even so, you want to eliminate the possibility of a false positive so that you're not constantly sifting through noise looking for a signal. Do you want to minimize noise as much as possible. So Lego does this through using combinations of active and passive vibration reduction systems. One thing that they do is they remove the air from the tubes. That is why they're vacuum tubes. They remove the air for two reasons. One, they don't want any sound passing through the chambers. Sound could possibly interfere with the measurements. Sound would impact the mirrors, and even a small impact would be enough to cause a problem when you're measuring this laser. For one thing, they're looking at distances when they're measuring the changes between the two branches. You know, I mentioned that one's getting longer, one's getting smaller. The distances they're looking at are very very tiny. We're talking ten to the negative nineteenth power meters. So again, you take the number ten, you move a decimal place nineteen times to the left of that, and you put meters at the end. That's the distance that these lasers are are measuring the distortion and distance. So it's very very very tiny, and something as simple as sound could change that. So you can't have any sound in these vacuum tubes, you've got to get the air out. Also, air can absorb and scatter laser light, which would interfere with the experiment as well, so you've got to get air out. Now down to the vibration reduction systems. So the active isolation system is meant to weed out the majority of vibration, and it's active because it is actively working against any vibration it encounters. You've got sensors that detect vibration, they send commands to force actuators that move in opposition to the vibration. So it's kind of like noise canceling headphones. If you put on a pair of noise canceling headphones, what they're supposed to do is pick up any incoming sound and then generate sound waves that are in direct opposition of the incoming sound, so that you get a cancelation effect. That's the same thing that these active systems are trying to do at LIGO, except instead of it just being sound, it's really any vibration. Although I guess you could argue that any vibration really is sound, so it's kind of a moot point. But anyway, they're actively trying to counteract that vibration. But then you've got the passive system. This is the suspension system for the mirrors, and this is the next step. So you've eliminated a huge percentage of the vibration at this point, but that's not good enough. You need to eliminate as much as close to one hundred percent of the vibration as you possibly can. So next we look at the suspension system of Ligo's mirrors, and they are at the base of a four pendulum system. Meaning imagine you've got a string and it ends in a pendulum. A weight a mass of some sort, and it has to be a mass of significant size so that it will it'll resist moving. It's the law of inertia. You know, an object at rest tends to stay at rest, so it will end up absorbing a lot of vibration and minimizing it on the other end. So you've got that first pendulum, that's pendulum number one. From that you suspend pendulum number two. So already you're getting fewer vibrations because pendulum number one is picking them up. What vibrations do manage to pass through start to get picked up by pendulum number two, and again the law of inertia means that it will dampen a lot of that vibration. Then you've got pendulum number three, and then beneath that you finally have the mirror, which is forty kilograms or about eighty eight pounds worth of mirror. And hopefully, after the active impassive systems have all taken care of the vibration, nothing else is getting to that mirror. By the way, you can actually test this out yourself, if you like, by getting four strings that are all equal length, and some washers, some nice heavy washers. Tie a washer at the end of the string of the first string. Then tie a washer so that one end of the string connects to washer number one, one end of the string connects to washer number two, and so on and so forth. And if you hold it up and you start shaking your hand holding the string, notice that the washer at the top moves more than the second washer, which moves more than the third, And by the time you get down to the fourth one, it's not moving much at all because it's been the vibrations have been dampened by the previous pendulums. That's the principle of this passive system. So that helps eliminate a lot of that vibration. Without those dampening systems in place, the two LIGO detectors would be picking up a lot of noise, and since we're still not really sure how often gravitational waves pass through the Earth, that would be a problem now. Between two thousand and two and twenty and ten, with the early version of LEGO, they didn't pick up any gravitational waves at all, which we think is because the detectors weren't sensitive enough. We think that's the reason, but an alternative reason could be that gravitational waves aren't as frequent as we think they are, that they don't pass through the Earth as frequently as we otherwise believe. However, the opposite could be true. We could have way more gravitational waves passing through Earth than we had anticipated. Some of them may be so faint that even this advanced LIGO system cannot pick it up. There are already plans to upgrade LIGO again, and there are other LIGO observatory systems that will that are in development now that will also listen in for gravitational waves. And listen tends to be the way most people refer to it, like you're listening for this universal vibration moving through the Earth. So because it was only a few days after they came online, a lot of people are thinking that gravitational waves are probably fairly common. Otherwise, it was just extraordinarily lucky that we picked it up just days after the observatory was online. Again, the one that we did pick up one point three billion light years away, which means that the event happened one point three billion years ago. That event being two black holes colliding with one another to form a solitary black hole mass. In the process, it vaporized about three solar masses worth of mass I guess, which is a huge amount to think about being converted into energy, and the gravitational waves emanated from there at the speed of light. So one point three billion years later, Earth, which was one point three billion light years away, picked them up. So in a way, it was incredibly lucky. But if this happens more frequently than we originally believed, we might see that this is not an uncommon event. It's very possible that there are things we cannot see in the universe that create gravitational waves. So in other words, it's off that does not give off electromagnetic radiation at all, but it does create gravitational waves, meaning that we now have the capacity to detect things that otherwise would have remained completely undetectable by us. So one of the many reasons why this discovery is so exciting, it opens up brand new science. It creates a new discipline of science, gravitational astronomy, which can really get going now because it's not that different from when the telescope was invented. Before the telescope, astronomy was pretty limited. You could map out astrological bodies when you were way back in the day before the science of astronomy had really gotten going. Once you started figuring out the difference between mythology and science, then astronomy really takes over. You could map out where these different bodies go. You could figure out which ones are must be planets versus stars, but you couldn't really gather a lot more information than that. You could still get an impressive amount of data just from observing with the naked eye, but the telescope opened up a whole new world of study, and this gravitational wave detector system has opened up a similar, all new world that was not accessible by us until this year really late last year, late twenty fifteen, So we might end up discovering things that we've never been able to observe before. Will also likely be able to study all sorts of cool stuff, like how fast is the universe expanding, how much dark energy is in our universe. We might learn more about black holes already. The gravitational wave detected by LIGO has given us the strongest direct evidence of black holes. I guess I should say indirect evidence because it's the gravity waves generated by the black holes. But not that we ever doubted the existence of black holes, but this is yet more evidence in support of them. So it's really an exciting time. We could end up learning all sorts of stuff, stuff that we can't even anticipate right now, and that's why it's such a big deal. I also think that LEGO is just an incredibly elegant way of detecting something that otherwise is impossible for us to see or feel or experience, and it's incredibly simple, at least on the principle of it. The technology itself is very complicated because it has to be so sensitive to detect these very tiny changes in distance and time. But the principle behind it is elegant, and I mean, you don't get much more simple than a ninety degree angle. That's pretty bare bones there, but a very clever way of detecting something that Einstein believed was going to be beyond our ability to ever experience. So now we have a revolutionary new way to examine the universe. We have no way of knowing what sort of stuff we might learn as a result, which is incredibly exciting. And it's all due to some lasers, some beam splitters, and some mirrors. And since we're already looking at lots of different organizations building their own LIGO observatories and also increasing the capacity or at least the sensitivity of the current LEGO system, who knows what we're going to see next. I hope you enjoyed that classic episode on HOWLEGO works way back in twenty sixteen. I should definitely do an update on that and talk more about the sort of things we've learned since the detection of gravitational waves and how that has affected science. But if you have suggestions for things I should cover in future episodes of tech Stuff, I'd love to hear. There are a couple of different ways you can do that. You can download the iHeartRadio app. It's free to downloads free to us. You can just navigate over to tech Stuff. Put tech Stuff in that little search field. It'll take it to the podcast page. You'll see a little microphone icon. If you click on that, you can leave a voice message up thirty seconds in length, and I love hearing from y'all, so feel free to do that. If you would prefer to send me something via text, well, you can go over to Twitter and use send a message to the handled text Stuff HSW that's our handle, and let me know what it is you would like me to do. Cover in future episodes of tech Stuff and I'll talk to you again really soon. Text Stuff is an iHeartRadio production. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.

Welcome to Tech Stuff, a production from iHeartRadio. Hey there, and welcome to tech Stuff. I'm your host Jonathan Strickland. I'm an executive producer with iHeartRadio and how the tech are here. It is time for a classic episode. This one is called How Lego Works. Originally published on February twenty fourth, twenty sixteen. This was really cool because this came out shortly after we were learning about how Lego had detected gravitational waves, which up to that point had largely been a hypothetical concept. So this was one of those things where we finally figured out a way to detect something that had been hypothesized about but previously undetected, So really cool use of technology. Then the Ligo Observatory had picked up a gravitational wave, and this was huge news around the world. And in case you were wondering, what the heck is this news all about? How did they pick up that gravitational wave? What exactly is the technology powering our sensors to detect this stuff? How does it all work? That's what this episode's all about. So this was the very first time anyone had been able to measure a gravitational wave directly So today we're going to talk all about what that means and how it happened. Now, to begin with, we need to lay some groundwork and to really get an understanding of what gravitational waves are. So gravitational waves ultimately were one of the predictions made by a certain Albert Einstein with this theory of general relativity. So in that theory, Einstein presented this idea that our universe is filled with spacetime. If you're a fan of science fiction, you have undoubtedly come across that term star trek is all about the spacetime continuum, and that you've got to be careful. You could rip a hole in the fabric of spacetime. As far as we know, that's not really that possible. I mean, black holes could sort of be that maybe, But at any rate, spacetime itself is this calling it stuff is probably the wrong way of putting it, but it is like a fabric and mass hangs inside this fabric, And by mass, i'm talking about stuff like stars or even an entire solar systems or galaxies that hang in this fabric, and just like you would see in a two dimensional display, it ends up curving the fabric around the mass. We often talk about this in terms of a very simple example that's easy to imagine. You get some sort of stretching material. Often you'll just hear someone say, okay, get a trampoline. You've got a trampoline, and you put a big, heavy bowling ball on the trampoline. So that bowling ball is going to deform the trampoline surface. It's no longer going to be straight. It's going to end up curving around the bowling ball to some extent, creating kind of a dmple where the bowling ball has has created this impression inside the trampoline, and as long as the bowling ball is there, that impression is going to stay. This is sort of the like the way spacetime curves around giant masses like stars and black holes things like that. Of course, we have to remember that spacetime is actually four dimensional, not a two dimensional thing like a trampoline. I mean, I know that trampolines technically have three dimensions, but we're really looking at a surface, so it's more like a two dimensional plane. In reality. In spacetime it's four dimensional because you've got the three spatial dimensions plus time, and that is a little difficult to get your head around. But that's why we tend to look at this two dimensional example. It's a lot easier for us to imagine. So let's go a little further with that analogy to kind of talk about gravity. See Einstein proposed that gravity was a manifestation of this curved space time. And if we take that trampoline example, Let's say that you have a regular trampoline. You haven't put the bowling ball on there yet, so it's a nice flat surface, and you have a marble, and you roll the marble across the surface of the trampoline. So if there's nothing else there, and if the trampoline is level, if the surface is level, the marble should just roll in the straight line from one side of the trampoline to the other, no problem. Now let's say you put that big, heavy bowling ball on the trampoline. It creates that dimple, and then you try and roll the marble across the trampoline surface. Well, now that dimple is going to end up affecting the pathway of the marble. It's going to start to spiral inward toward the bowling ball. Ultimately it'll end up making contact with the bowling ball, and Einstein said, that's essentially what gravity is. It's that you've got these large masses that curves spacetime to the extent that smaller masses are spiraling inward toward the large mass. It's just happening on a scale that's much much, much larger than any bowling ball, marble example. But that this isn't essentially what we see when we see planets orbiting a sun, or we see a moon orbiting a planet, or we see star systems orbiting a galaxy, you know, the center of a galaxy, and it's all because of this curve spacetime. Now, all of that already is pretty heavy stuff. And keep in mind, there was not really any way to directly observe this. It was mostly the the just Einstein using logic to work all this out and math, logic and math, and ultimately it fit with what we saw of the universe. But we weren't able to test a lot of this. But then it gets even more mind blowing because now we have to get to gravitational waves. So Einstein said that if a mass were large enough and either changed shape rapidly enough or it changed its movement in some way, really really quickly. It would cause ripples of space time to move outward from that event at the speed of light. And those ripples are what we call gravitational waves, which are different from gravity waves. By the way, I have been known to accidentally say gravity waves instead of gravitational waves, but the two are different things. A gravity wave is a wave that exists because of gravity. In other words, it's a physical wave of some sort of fluid system, whether it's atmosphere or water or some other liquid. That's a gravity wave on a planet's surface. It's not the same thing as a gravitational wave, which is really a ripple of space time, and like I said, it moves outward from that event at the speed of light. And stuff that could cause significant gravitational waves, things that would be big enough for us to potentially pick up here on Earth if we had the right equipment, would include things like two black holes orbiting or colliding with one another, which in fact, that was the event that we were able to pick up with the Ligo facilities. And I'll talk about those in just a bit. But there could be other stuff too, like neutron stars orbiting one another fast enough would generate gravitational waves, or a supernova explosion would create one as well. And each of these events give off a huge amount of energy, and some of that energy gets converted into making these gravitational waves. So one takeaway from this prediction something that Einstein said would happen, is that any event that produces gravitational waves is an event in which energy is being lost, So you would expect to see less energy within that system afterward than before. And it would be a hundred years from the time of publication of the theory of general relativity to the time when scientists announced that they had detected a gravitational wave directly. And that's because gravitational waves are devilishly difficult to detect. And that's some alliteration for you right there. So gravitational waves are invisible. They don't emit any sort of electromagnetic radiation, so we can't see them. We can't detect them with radio detectors, nothing like that, and that makes it pretty tricky to figure out where they are. But they do just pass through the universe. They don't get absorbed or scattered the way electromagnetic radiation does. If you hold up a mirror and light hits the mirror, light will bounce off the mirror. That's not the case with gravitational waves. They pass right through, so it's a very different thing than electromagnetic radiation. And while they're generated from enormous events, the gravitational waves aren't very strong. By the time they get to Earth. They are pretty weak, so weak that you would need an incredibly sensitive tool in order to pick them up. And also you have to be searching at the right time, because if the event that generated the gravitational waves happened a billion years ago, but the location is four billion light years from Earth, then we would have to wait another three billion years for those gravitational waves to get to us, because again, they travel at the speed of light. That's their limit. So you have to be at the right place at the right time to pick these things up, and in some cases you might argue that that's incredibly fortuitous. Although to be fair, it looks like the events that could generate gravitational waves happen pretty frequently throughout the universe. But the universe is huge, so if they're happening far away, far enough away, will take a very long time for that information to get to us. So before the announcement on February eleventh, twenty sixteen, scientists had observed phenomena that supported the existence of gravitational waves, but were not direct observations of a gravitational wave. Here's an example. A pair of astronomers in Puerto Rico in the nineteen seventies noticed that there was a binary pulsar system and they went back to the theory of general relativity because this was a sort of system that would be exactly the type to generate gravitational waves according to the predictions from general relativity, and because general relativity predicted, hey, if it can create gravitational waves, it's going to lose energy over time, they ended up coming up with the hypothesis that, well, over time, this binary pulsar system should start to slow down because it's losing energy. It can't keep up at the speed it's going. So they decided to keep an eye on it. And by keeping an eye on it, I mean they continue to observe this pulsar system over the course of eight years, and by the end of the eight year period, they were comparing the findings they were observing to the predictions made by general relativity, and they were matching up. It was unfolding exactly the way Einstein predicted it should unfold based upon his theory of general relativity, which is incredible when you think about it, that the observations are matching up so neatly against the predictions. You know, it just shows how how keenly aware Einstein was of how our universe appears to work. Keeping in mind that general relativity, while an amazing idea collection of ideas, really it doesn't encompass everything that we know, right. It doesn't really address quantum mechanics, for example, at least not in a way that incorporates it with classical physics. But based upon what it did cover, it seems like it was an incredibly accurate theory, all right. So this was really considered strong but indirect support of gravitational waves, because again the astronomers didn't observe gravitational waves directly. They couldn't see them or detect them, but they could see the effects, and again it was matching up with the predictions made from general relativity. So it was good indirect evidence that gravitational waves existed. Then there was an event a couple of years ago that you might have heard about when a team of researchers working on the BICEP two telescope, which is an Antarctica had announced that they thought they might have discovered evidence of gravitational waves that supported a hypothesis called cosmic inflation. That's a lot of information right there, So let me explain what all that means. Cosmic inflation is a hypothesis that relates to the Big Bang theory. So, with the Big Bang theory, you've got this event in which the universe undergoes a period of rapid expansion. Cosmic inflation is kind of that rapid expansion on steroids. The idea being that, well, when we look at our universe and we look at what we can observe, it appears that our observations don't quite match up with what we would expect if we had just steady expansion since the Big Bang. In other words, we look at all the information we have available to us, and it looks to us that it doesn't quite match up. Something's got to be wrong. Well, one possible explanation is that shortly after the Big Bang, and by shortly, I mean tend to the negative thirty sixth power seconds after the Big Bang, So you take a ten, you put a decimal point behind the ten, then you move the decimal point to the left thirty six times that you put seconds behind that. We're talking a fraction of a fraction of a fraction of a second. The universe underwent massive expansion, and it only lasted from that point to about ten to the negative thirty third power or thirty second power seconds. So again an instant. It's completely unimaginable, at least for myself, how short an amount of time this was. But that's how quickly the universe expanded significantly, and then it slowed, but it continued to expand. Now, if in fact, cosmic inflation is correct, it solves a lot of the problems we have between the what we observe today and what we believe happened with the Big Bang, and reconciles those differences. If cosmic inflation is wrong, then something else that we believe is wrong. Right. It means that what we observe either isn't representative of reality somehow we're not getting a big enough picture to understand it, or that the Big Bang theory itself is flawed in some fundamental way. Hey, we'll be back with this heavy subject of detecting gravitational waves with LEGO after this short break, so the BIS of two team what they were looking for was some evidence of gravitational waves that would have been generated during the Big Bang. This would end up supporting the cosmic inflation hypothesis. And the way they did this was they were looking at the cosmic microwave background or CMBAM. Now, the cosmic microwave background emerged about three hundred eighty thousand years after the Big Bang. This was still a period where the universe was so dense that I could not pass through it. It was dark and dense, but the cosmic microwave background formed around that time, and the hypothesis stated, well, gravitational waves would have affected the cosmic microwave background, polarizing some of those some of those particles really not particles, but some of that energy polarizing some of the cosmic microwave background in such a way that if you were to observe it, you could see the effect of a gravitational wave passing through the cmb And then as the universe expand expanded, rather that mark would also expand. It's kind of like imagine leaving a fingerprint on some sort of stretchy material and then stretching that material out, the fingerprint is still there. It's deformed, but still there. That's what the BICEP two team was looking for, was this pattern in the CMB that would indicate that gravitational waves from the Big Bang had passed through, and if they found that, that would be a huge support for cosmic inflation. And in the spring of twenty fourteen, they announced that they believed they had found such evidence, and they also invited other researchers to take a look at their data and see if it was verifiable or maybe they overlooked something. And in the fall of twenty fourteen, another team said, we're sorry, but it looks to us like space dust might have created a false positive that what you thought it was the polarized CMB that you had been looking for was actually just space dust that's not actually part of the CMB. And so that ended up kind of putting a dampener on the whole celebration of finding gravitational waves to support cosmic inflation. But even if it was completely verified, even if BICEP two had irrefutable evidence that they had found the presence of gravitational waves through a you know, the way it affected the CMB. Even then that's not direct detection. It's still indirect. You're looking at the way it's affected something else. So you know, again we're still not discovering one. And part of that is that BICEP two is a telescope. It's looking at through the electromagnetic spectrum, and again, gravitational waves don't show up that way. So no telescope would help you find a gravitational wave directly. You might be able to find how it affected something else, but not the wave itself. Now that's not the case with the LIGO observatories. Actually it's technically one observatory, but it has four different facilities, two detectors and two research facilities that are all part of the LIGO observatory. LIGO itself is an acronym and it stands for Laser Interferometer Gravitational Wave Observatory. So it's a pair of giant detectors built on the surface of the Earth. One is located in Hanford, Washington, the other is in Livingstone, Louisiana. Now they're about just a little under two thousand miles apart, or just over three thousand kilometers apart from each other, and that's really important. I'll explain why in a little bit. So to understand how they work, we also have to talk about something else that gravitational waves do as they pass through space. They stretch and compress space itself. So again, if you were if you were to take a piece of elastic, I'd say, you've got a rubber band, a nice thick rubber band, and you cut it so that it's just one strip. When you pull on that rubber band, it stretches along the line where you're applying force, So it stretches in that direction, in the perpendicular direction ninety degrees from where you're pulling. It compresses, it gets more narrow, and then when you let it return to its normal shape, it gets you know, the long part ends up getting shorter and the narrow part ends up getting wider as a result, gravitational waves do this to reality. They do this to actual space. They stretch and compress, and it happens several times as the wave oscillates through. Really I should just say as the wave passes through, rather than oscillates. The distortion oscillates, but the wave passes through, so That means the actual distance changes between two points as that gravitational wave passes through that area. So if we were to magnify this effect, and I mean magnify it to a ludicrous degree, you would be able to see it. You would actually be able to witness this. You could stand ten feet away from someone else and when the gravitational wave passes through, it would make it look like the two of you suddenly got further away and then closer to each other, and then further away and closer to each other, even though you haven't moved anywhere, because the distance itself is stretching and compressing. So why don't we see that? I mean, if these celestial events that produce gravitational waves happen on the order of something like every fifteen minutes, why are we all noticing this whibbly wobbly effect. Well, it's because the actual distortion that happens here on Earth is much much much smaller in magnitude, so much more so much smaller that it's difficult to even explain. But if you were to have a supernova explode in the Milky Way galaxy, in our galaxy, the gravitational waves generated by that explosion would maybe be powerful enough to distort the distance between the Earth and the Sun by about the diameter of a hydrogen atom, so not noticeable to any degree, and not at least to human senses. So if you were to even go on a smaller scale, let's say that you pick two points that are a kilometer apart here on the surface of the Earth, the amount of distortion would be equivalent to a few thousandth of the diameter of a proton, So you're talking about a subatomic particle, and just a tiny, tiny, tiny fraction of that subatomic particles diameter would be the amount of distortion that would happen across a kilometer worth of distance here on Earth. Again, that means it's so small that it's incredibly difficult to detect, so much so that Einstein himself was pretty sure we would never be able to directly detect gravitational waves because he could not imagine a system that would be sensitive enough to pick up such a minute change, a distortion that's happening so quickly because it's a fraction of a second, and it's so small as to be unnoticeable. So the other problem here is not just that it's such a very tiny effect that lasts a short amount of time. It's also that a lot of other stuff could create false positives. You can have incredibly instrumentation, but if that instrument is really really sensitive, any sort of interference could set off and you could end up getting false readings. So a change in air pressure or temperature, or seismic activity, even a heavy truck driving nearby could set off false results. So you'd have to come up with a really clever way to measure distortion, to limit vibration, and to eliminate the chance that it was a false positive. And Lego is the answer to all of that. So the Lego Observatory is actually the result of decades of collaborative work among different scientific research centers and internet national bodies and universities, and all started back in nineteen seventy nine. That's when the National Science Foundation approved funds for Caltech and MIT to develop laser interferometer research and development. And a few years later, in nineteen eighty three, Caltech and MIT submitted a proposal for a kilometer scale detector. But keep in mind, all right, so in nineteen seventy nine you get the funding for R and d nineteen eighty three, there's the submission of a proposal for a kilometer scale detector. There wouldn't be approval for a detector until nineteen ninety, so almost a decade later, and which turns out was probably okay, because we really didn't have the technological ability to detect things on a scale small enough to register a gravitational wave in the first place. But still, you know, a decade's delay before you even get approval is still pretty rough. Construction didn't begin until nineteen ninety four. The inauguration of the Ligo Observatory took place in nineteen ninety nine, but even then that didn't mean that the observatory was online collecting data. It didn't do that until two thousand and two. And here's the kicker. Eventually scientists came to the conclusion that this Ligo observatory was not sensitive enough to detect gravitational waves. That despite the fact that it was this large detector or pair of large detectors, actually because again one in Louisiana one in Washington, it wasn't sensitive enough to be effective. So it was not quite back to the drawing board, but it did mean that they had to think about how they would upgrade these facilities so that they could be sensitive enough to pick up a gravitational wave. So in twenty ten, Ligo went offline to undergo a big overhaul, and it took four years of construction and testing to get it into shape and another year to set it up for new observations, which means that it wasn't until twenty fifteen that it was ready to come back online. By now it was called the Advanced Ligo Observatory and it began collecting data in September twenty fifteen. Literally days after it had come online, it picked up a gravitational wave. So that's pretty phenomenal that just a couple of days, just a few days really after it had been turned on again in twenty fifteen, we got a hit. So that was incredibly exciting. So how did this happen? How does it actually work? Well, we have to take a look at what interferometers are all about. An interferometer uses a technique in which electromagnetic waves are superimposed on one another in order to get information. Now, Ligo does this with a laser beam because it's a laser interferometer, and the laser beam gets shot through a beam splitter, and the beams, the two beams that result go down two long vacuum tubes. So both of the Lego detectors are in an L shape. So you've got these long, long vacuum tubes that extend two and a half miles or about four kilometers out from the crux from the angle where they meet up, and each one is you know, they're both the same length. They have to be exactly the same length. And the way this works is that kind of behind the crux, you've got a laser that shoots out a beam of light to a beam splitter. The splitter does exactly what it sounds like. It does. It splits the beam into two separate beams with alternating canceling wavelengths. I guess I should say, so the troughs and peaks on one match up with the peaks and troughs of the other. That's really important when we get a little further down the line here. So one of those two beams goes down one branch of this L shaped detector. The other beam goes down the other branch. And keep in mind, like I said, both of these branches are exactly the same length. Two and a half miles or four kilometers. When the laser gets to the end, they hit a mirror. Each beam hits a mirror, they come back to the point of origin, and because the two laser beams have these counteracting wavelengths, they cancel each other out, so the peaks on one cancel out the troughs of the other, and vice versa. That means that no light gets emitted through this system. And that's important because there's actually a light detector that's part of this system as well. It's looking for any sign of laser light, because a sign of laser light would say that something has changed somehow the distances between these or the distances represented by these two vacuum tubes has changed, and that would be indicative of an event like a gravitational wave moving through. So if any light shines through, you know something has happened. Essentially, it says that there's a mismatch in the lengths of the vacuum tubes themselves. So when a gravitational wave passes through, one vacuum tube will get shorter while the other gets longer. And that's because the two tubes are offset by ninety degrees, so one is going to be along one side of the wave and that will lengthen the other will be along will be perpendicular to that, and will shorten as a result. And this means that the lasers will have different distances to travel down, So the laser traveling the shorter distance takes less time to get back to the crux. The laser going down the longer distance takes more time. And even though this is only happening within a fraction of a second, it's long enough for us to be able to detect the difference. And it also means that those wavelengths don't match up anymore, they don't cancel each other out anymore. So some of that laser light gets emitted to the light detector, which then indicates what's going on. It knows which one of the branches was short versus long, and knows how long it happened. It knows how much it oscillated back and forth, because obviously this is continuing as these as the gravitational wave moves through, So you collect a lot of data in a short amount of time. And we're talking like teeny tiny slices of a second. As we're getting all this information, which is pretty incredible. We're almost done with our discussion about LEGO, but before we can do that, we need to take one more quick break. So once you get all that data, you can then analyze it. Actually, more importantly, before you analyze it, you have to verify it. Now. This is why it's important that there are two detectors, and it's also important that they are so far apart, like three thousand kilometers apart from each other. That's because if you get a blip on one of them, if it's a true gravitational wave, you should also get a blip on the other one. And because gravitational waves move at the speed of light, there should be a slight difference in time when both detectors pick up on this gravitational wave, somewhere right around ten milliseconds or less. In the case of the one that was detected back in the fall of twenty fifteen but not announced until twenty sixteen, it hit the Louisiana detector first, and seven milliseconds later it hit the Washington detector, So that is indicative of something like a gravitational wave as opposed to some local event that would have caused interference and created a false positive. If an earthquake had happened in Washington, then the facility may may have picked something up, but you wouldn't expect to see it in Louisiana because it was a localized event. Same thing is true if something had happened in Louisiana. So by seeing it happen at both within this ten millisecond timeframe meant that it was a very good candidate for a gravitational wave passing through. And that's exactly what happened. It was a home run in the first ending of the game, or even really the first at bat of the game. It's like your first player steps up on the first day of baseball and knocks a home run and that defines the moment the season. Really, that's that's the equivalent of what we saw here on a scientific basis. So the other thing I want to talk about was how LEGO tries to minimize the possibility of detecting a false positive in the first place. So, yeah, false positives are something that they worry about, and the fact that there are two detectors helps minimize that. But even so, you want to eliminate the possibility of a false positive so that you're not constantly sifting through noise looking for a signal. Do you want to minimize noise as much as possible. So Lego does this through using combinations of active and passive vibration reduction systems. One thing that they do is they remove the air from the tubes. That is why they're vacuum tubes. They remove the air for two reasons. One, they don't want any sound passing through the chambers. Sound could possibly interfere with the measurements. Sound would impact the mirrors, and even a small impact would be enough to cause a problem when you're measuring this laser. For one thing, they're looking at distances when they're measuring the changes between the two branches. You know, I mentioned that one's getting longer, one's getting smaller. The distances they're looking at are very very tiny. We're talking ten to the negative nineteenth power meters. So again, you take the number ten, you move a decimal place nineteen times to the left of that, and you put meters at the end. That's the distance that these lasers are are measuring the distortion and distance. So it's very very very tiny, and something as simple as sound could change that. So you can't have any sound in these vacuum tubes, you've got to get the air out. Also, air can absorb and scatter laser light, which would interfere with the experiment as well, so you've got to get air out. Now down to the vibration reduction systems. So the active isolation system is meant to weed out the majority of vibration, and it's active because it is actively working against any vibration it encounters. You've got sensors that detect vibration, they send commands to force actuators that move in opposition to the vibration. So it's kind of like noise canceling headphones. If you put on a pair of noise canceling headphones, what they're supposed to do is pick up any incoming sound and then generate sound waves that are in direct opposition of the incoming sound, so that you get a cancelation effect. That's the same thing that these active systems are trying to do at LIGO, except instead of it just being sound, it's really any vibration. Although I guess you could argue that any vibration really is sound, so it's kind of a moot point. But anyway, they're actively trying to counteract that vibration. But then you've got the passive system. This is the suspension system for the mirrors, and this is the next step. So you've eliminated a huge percentage of the vibration at this point, but that's not good enough. You need to eliminate as much as close to one hundred percent of the vibration as you possibly can. So next we look at the suspension system of Ligo's mirrors, and they are at the base of a four pendulum system. Meaning imagine you've got a string and it ends in a pendulum. A weight a mass of some sort, and it has to be a mass of significant size so that it will it'll resist moving. It's the law of inertia. You know, an object at rest tends to stay at rest, so it will end up absorbing a lot of vibration and minimizing it on the other end. So you've got that first pendulum, that's pendulum number one. From that you suspend pendulum number two. So already you're getting fewer vibrations because pendulum number one is picking them up. What vibrations do manage to pass through start to get picked up by pendulum number two, and again the law of inertia means that it will dampen a lot of that vibration. Then you've got pendulum number three, and then beneath that you finally have the mirror, which is forty kilograms or about eighty eight pounds worth of mirror. And hopefully, after the active impassive systems have all taken care of the vibration, nothing else is getting to that mirror. By the way, you can actually test this out yourself, if you like, by getting four strings that are all equal length, and some washers, some nice heavy washers. Tie a washer at the end of the string of the first string. Then tie a washer so that one end of the string connects to washer number one, one end of the string connects to washer number two, and so on and so forth. And if you hold it up and you start shaking your hand holding the string, notice that the washer at the top moves more than the second washer, which moves more than the third, And by the time you get down to the fourth one, it's not moving much at all because it's been the vibrations have been dampened by the previous pendulums. That's the principle of this passive system. So that helps eliminate a lot of that vibration. Without those dampening systems in place, the two LIGO detectors would be picking up a lot of noise, and since we're still not really sure how often gravitational waves pass through the Earth, that would be a problem now. Between two thousand and two and twenty and ten, with the early version of LEGO, they didn't pick up any gravitational waves at all, which we think is because the detectors weren't sensitive enough. We think that's the reason, but an alternative reason could be that gravitational waves aren't as frequent as we think they are, that they don't pass through the Earth as frequently as we otherwise believe. However, the opposite could be true. We could have way more gravitational waves passing through Earth than we had anticipated. Some of them may be so faint that even this advanced LIGO system cannot pick it up. There are already plans to upgrade LIGO again, and there are other LIGO observatory systems that will that are in development now that will also listen in for gravitational waves. And listen tends to be the way most people refer to it, like you're listening for this universal vibration moving through the Earth. So because it was only a few days after they came online, a lot of people are thinking that gravitational waves are probably fairly common. Otherwise, it was just extraordinarily lucky that we picked it up just days after the observatory was online. Again, the one that we did pick up one point three billion light years away, which means that the event happened one point three billion years ago. That event being two black holes colliding with one another to form a solitary black hole mass. In the process, it vaporized about three solar masses worth of mass I guess, which is a huge amount to think about being converted into energy, and the gravitational waves emanated from there at the speed of light. So one point three billion years later, Earth, which was one point three billion light years away, picked them up. So in a way, it was incredibly lucky. But if this happens more frequently than we originally believed, we might see that this is not an uncommon event. It's very possible that there are things we cannot see in the universe that create gravitational waves. So in other words, it's off that does not give off electromagnetic radiation at all, but it does create gravitational waves, meaning that we now have the capacity to detect things that otherwise would have remained completely undetectable by us. So one of the many reasons why this discovery is so exciting, it opens up brand new science. It creates a new discipline of science, gravitational astronomy, which can really get going now because it's not that different from when the telescope was invented. Before the telescope, astronomy was pretty limited. You could map out astrological bodies when you were way back in the day before the science of astronomy had really gotten going. Once you started figuring out the difference between mythology and science, then astronomy really takes over. You could map out where these different bodies go. You could figure out which ones are must be planets versus stars, but you couldn't really gather a lot more information than that. You could still get an impressive amount of data just from observing with the naked eye, but the telescope opened up a whole new world of study, and this gravitational wave detector system has opened up a similar, all new world that was not accessible by us until this year really late last year, late twenty fifteen, So we might end up discovering things that we've never been able to observe before. Will also likely be able to study all sorts of cool stuff, like how fast is the universe expanding, how much dark energy is in our universe. We might learn more about black holes already. The gravitational wave detected by LIGO has given us the strongest direct evidence of black holes. I guess I should say indirect evidence because it's the gravity waves generated by the black holes. But not that we ever doubted the existence of black holes, but this is yet more evidence in support of them. So it's really an exciting time. We could end up learning all sorts of stuff, stuff that we can't even anticipate right now, and that's why it's such a big deal. I also think that LEGO is just an incredibly elegant way of detecting something that otherwise is impossible for us to see or feel or experience, and it's incredibly simple, at least on the principle of it. The technology itself is very complicated because it has to be so sensitive to detect these very tiny changes in distance and time. But the principle behind it is elegant, and I mean, you don't get much more simple than a ninety degree angle. That's pretty bare bones there, but a very clever way of detecting something that Einstein believed was going to be beyond our ability to ever experience. So now we have a revolutionary new way to examine the universe. We have no way of knowing what sort of stuff we might learn as a result, which is incredibly exciting. And it's all due to some lasers, some beam splitters, and some mirrors. And since we're already looking at lots of different organizations building their own LIGO observatories and also increasing the capacity or at least the sensitivity of the current LEGO system, who knows what we're going to see next. I hope you enjoyed that classic episode on HOWLEGO works way back in twenty sixteen. I should definitely do an update on that and talk more about the sort of things we've learned since the detection of gravitational waves and how that has affected science. But if you have suggestions for things I should cover in future episodes of tech Stuff, I'd love to hear. There are a couple of different ways you can do that. You can download the iHeartRadio app. It's free to downloads free to us. You can just navigate over to tech Stuff. Put tech Stuff in that little search field. It'll take it to the podcast page. You'll see a little microphone icon. If you click on that, you can leave a voice message up thirty seconds in length, and I love hearing from y'all, so feel free to do that. If you would prefer to send me something via text, well, you can go over to Twitter and use send a message to the handled text Stuff HSW that's our handle, and let me know what it is you would like me to do. Cover in future episodes of tech Stuff and I'll talk to you again really soon. Text Stuff is an iHeartRadio production. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.