Part 1! What are gravitational waves? What makes them? How can we detect them here on Earth, and why is it a big deal? I discuss these questions and more in today’s Ask a Spaceman!
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I'm a sushi chef. I also happen to be a cat. How to get here. Adobe Photoshop. It turned a cute kitty like me into a sashimi master, and it can make your images look amazing, too. In just a few clicks, you can replace a boring background, swap out a so so sky and remove distractions like people in power lines. With Photoshop. Everyone can. I love playing with this mouse. Click or tap the banner to visit Photoshop dot com and pounce on your free trial today, my first research advisor ever. And this is way back when I was an undergraduate at California Polytechnic State University or Cal Poly, if you're cool. Uh, this is back in the early two thousands. My advisor was Dr Semi Tanaka. He was an expert in relativity in general relativity, special relativity. He taught courses on the subjects. His own research was was based in relativity.
And now relativists are not as common as you might think. But he was He was one of them. He was an expert in general relativity, and one day I remember in class was a class on general relativity, and he's talking to the class And you know, when you when you can get a professor going on some little side tangent, especially about their lives, they always take you up on the offer and they start reminiscing. And I remember him distinctively making an offhand comment about the career options for scientists, for physicists and then, especially specialists like him and relativity relativists. And he said, uh, if you wanna be a relativist, all you get to do is make templates, templates, templates, templates, just a bunch of templates. It's so boring. I went on to do a project with him that had nothing at all to do with templates, and if you're curious, it was calculating kasmir forces for flat universes with different Toppo.
But the paper is on my website if you're interested. But to get at what Doctor Tenna was talking about, we need to set the clock back another 100 years. We need to talk about Einstein and the discovery of gravitational waves. First off, the equations of general relativity are hard, and not just Oh, physics is hard, hard for physicists. General relativity is hard general relativity. This is our understanding of gravity. It's so easy to say that Oh, if you have mass or energy, you distort space time around you, and then the distortion of spacetime tells mass and energy how to behave and move, and stuff sounds super easy. In reality, it is a set of 10 nonlinear equations that are all coupled together and are basically impossible to solve. It is a nasty set of equations.
It's very elegant. It's very beautiful to write down. You can write down very, very compact forms of these equations, but buried under the surface is just nastiness. And that's why there are not a lot of relativists. There are not a lot of specialists in general relativity among the physics community because it's hard and it's complicated and it's tough to make progress. And this is one of the reasons why general relativity took forever to take off like Einstein made it in the 19 tens. And then we we realized it was largely correct. But then no one knew how to actually make progress in it and how to solve problems with it and and apply it to interesting, unusual circumstances. And so it just sat around for decades. It took really until the 19 fifties and sixties before general relativity became, you know, a fashionable topic, and even then, even after that, it hasn't been the hottest topic in physics. It's high energy physics, particle colliders. That stuff is easier than general relativity.
But because the equations of GR are so damn hard, you have to come up with lots of tricks to simplify them so you can actually get work done. One trick is called linear, and I won't get into the technical details of that little nugget, but for our purposes is it just means that the equations are simpler to handle. You're looking at a simplified version of the equations that are not applicable to all cases. But you can actually write down solutions and get work done and make progress, and so you can hopefully gain some some physical insight. And it's an approximation that holds true when gravity isn't all that strong. And it's in this simplified version of GR that Einstein discovered gravitational waves, which is, as the name suggests, a literal wave in space time. It's a ripple in spacetime, just like you can have water waves and sound waves and electromagnetic waves. You can have waves of gravity gravity can come at you in waves. It's so cool to think about it.
We're used to gravity as just being a presence, a force. The earth exerts a gravitational force on us, and we feel it all the time. And it's constant. It's just there. But a gravitational wave is a ripple of gravity, where the gravity can get stronger and weaker as the ripple washes over you. It's a cool concept. It's a weird thing to think about, and at first glance it might be a little bit too weird. Einstein himself. As soon as he wrote the paper saying, Hey, gravitational waves might exist, he he doubted their existence. He thought it might be an artifact of the simplification process and not a real thing, which is a valid argument. It's like saying, Well, the math says so this is why we use math is because it tells us things that are true in physics. But we did all this simplification process. So are we seeing something that's actually reflected in nature or because this approximation doesn't actually hold?
And yeah, it comes out in the math. But this this setup doesn't actually accurately describe nature. The math says so. But if you have to torture the math to get there, you know you're not exactly sure if it's telling the truth or not. Maybe it's just telling you what you want to hear. Einstein equivocated on it to his grave. The debate went on for decades because GR is really, really hard to make progress in, and not a lot of people were working on it at the time. Quantum mechanics, quantum field theory were way more interesting and way more attractable. You can actually make progress in those fields, and so people made progress in those fields. Eventually, in the 19 fifties, we realized that gravitational ways work in the full, non simplified equations of GR, which means they were legit. Now what gravitational waves exist. What does a gravitational wave do? First off, I need to clarify something about the name here. I'm gonna be absolutely careful during this episode, and I need you to be absolutely careful when you talk about it with friends and, well, relatives and acquaintances and dinner dates.
It is not a gravity wave. It is a gravitational wave. The reason they are called gravitational waves and not gravity waves is because the name gravity waves is already taken. These are a kind of wave in the atmosphere that were studied decades before GR came on the scene. So the name was taken. We couldn't call these things gravity waves because gravity waves is something else. You have to call it gravitational waves to think of a gravitational wave. Let's start with a water wave like when you think of a water wave, you think of up and down. The wave washes over you and you, bob up and down when a sound wave comes at you. These are waves of pressure in the air and you think in and out the the air molecules get closer together and then they spread out and they get closer together and then they spread. So you think in and out, in and out. When it comes to gravitational waves, you need to think stretch and squeeze. Remember this ripple in the fabric of space Time is literally a wave of gravity.
It is waves of forces of gravity. So as the wave washes over you, you will get squeezed in one direction and pulled in the other, and then more of the wave washes over you and you get squished in the opposite direction and then pulled in the opposite direction, then back and forth. So, like your sides will go in and out and your head and toes will go in and out and they're alternate back and forth, and you will feel it. You will feel this force. You will feel like giant soft hands are squishing on your side and then pulling on your side and squishing on your head and pulling on your head, stretching and squeezing like you're a piece of play doh that what it feels like to experience a gravitational wave is this stretching and pulling and the stretching and squeezing will be perpendicular to the direction of motion for a gravitational wave. When a water wave is washing over you, it might be moving in one direction, but you move perpendicular to that to that direction.
It's say the wave is going to shore in that direction, but you go up and down. You're moving perpendicular to that. When the gravitational wave is moving through you front to back, you are getting squeezed head to toe in side to side the force, the action of the force is perpendicular to that. There is no back and forth motion when it comes to gravitational waves. It's just the stretching and the squeezing. Also, I've seen a lot of people ask like you people if there is also time dilation going on here and the answer is no. Gravitational waves are just waves of space. So sometimes when when writers are talking about gravitational waves, they'll say ripples in the fabric of space time and yeah, that's technically true. Uh, because all spacetime is unified, you always have to talk about it connected together. But it is just gravitational waves of space. There is no effect on time here. The dimension of time is not getting manipulated by a gravitational wave.
A gravitational wave has all the normal wave properties that you have come to know and love and respect and expect there is a wavelength or a frequency as the gravitational wave is washing over you. And there's these invisible soft hands squeezing on you and pulling on you in very odd ways. It's like a a massage that you're not sure if you should pay for at the end or not, because it's getting weird. Like any wave, there will be a frequency how often the squeezing comes, how often the stretching comes. Like any wave, there will be an amplitude. How big the stretch is, how big the squeeze is. Like any wave, it will carry energy and momentum away from one place and towards another place like you are getting stretched and squeezed by the wave. That is a transfer of energy, something generated that way. Something generated the energy necessary. That energy was carried away by the wave. And then the wave manipulating you sends some of that energy to you that was radiated long ago. Just like any other wave.
You know, storm hits the middle of the ocean and then you get to bob up and down in the shore. That is the transfer of energy from the storm to your body through the action of the ocean waves, just like any other wave, they travel at a certain speed. Sound waves go at a certain speed. Ocean waves go at a certain speed. In this case, the speed of gravitational waves is the speed of light. One way to understand why gravitational waves travel at the speed of light is to look at the role that gravitational waves play in GR. And keep in mind that what I'm about to describe is a very modern understanding of how gravitational waves work and how they operate and the, uh, the role they play in the whole gravity game. This was not at all obvious to Einstein when he first discovered them. It took many decades to figure out exactly how gravitational waves work, but I want you to imagine this scenario because it's very helpful. Pedagogically. All right, we've got our sun right. It's It's the big glowing thing in the sky. In case you haven't been out in a while, let's say we got the Earth in orbit around the sun and let's say the sun disappeared just just just gone.
How long would it take for us to find out? Well, we know that it takes light 8.5 minutes to go from the surface of the sun to our eyeballs, and so presumably you might guess it would take 8.5 minutes for us to find out, because all of a sudden the sun would stop sending out light. But it had already sent out light and and it's gonna take 8.5 minutes for that lack of light to reach the earth. And we're gonna be like, Oh, right. Wow, There's no more sun who turned it off. What do we do now? Do we start eating each other now or do we do we wait until the food? OK, we wait. It's the ethical thing to wait. OK, so if the sun were to go out, it would take 8.5 minutes for the electromagnetic waves. The light waves to reach us for that signal to reach us. But what about gravity? The earth is in orbit around the sun. It's traveling at this incredibly fast speed, but it's kept in orbit from the gravity of the sun. Now, if the sun were to disappear, there'd be no more gravity, and the Earth would just fling off into space, heading out into the interstellar voids as we eat each other.
Would that be felt instantly? I mean, that's how we thought normal gravity worked back before GR, and it was just Newtonian gravity. The assumption was, gravity happened instantaneously, which seems kind of weird because If the light doesn't reach us for 8.5 minutes, why should the gravitational signal get here any sooner? So now we have a complete picture of what would happen. We we you can think of the sun embedded in space time as bending and curving spacetime, and however you want to envision that in your mind, feel free if you want to imagine a heavy bowling ball sitting on a rubber mat. If you want to see, imagine it embedded in three dimensions and everything's like curving around it. Go right ahead. But the mass of the sun is causing space to bend around it, which is what's keeping the earth in its orbit. And if you were to get rid of the sun, well, there'd be a big plot. There'd be a big change. All this bending would go away, and the first parts to go away would be the parts closest to the sun.
They'd be like, 00, no more sun here. So I got to return back to flat space time and then the parts just passed. That would get that signal. Oh, there's nothing inside of me, so I got to return to flat space. Um, and then it would go outward outward, outward. You can imagine a pulse of signal in gravity. As space itself reset from the lack of the presence of the sun, a pulse would go out and that pulse would travel at the speed of light because it's not gonna get here any faster. So take that scenario in your head and and instead of having the sun disappear in us eating each other, imagine taking the sun and just wiggling it back and forth. You can imagine the pulses of that signal rippling away from the sun. Those pulses traveling at the speed of light are the gravitational waves and like to make to make something a wave. All you need to do is wiggle. This is not surprising. If you're sitting in ocean water and you wiggle around you, you generate water waves. If you're sitting in an atmosphere and you make your voice box, your larynx wiggle.
You make sound waves. If you take an electron and wiggle it back and forth, you make electromagnetic waves, and if you take a massive object and wiggle it back and forth, you get gravitational waves and these waves travel at the speed of light because what else? What other speed could they possibly travel at? I need to mention something else about the waves. Gravitational waves are exceedingly weak, and I mean exceedingly, and I don't think you understand just how exceedingly I mean here. Gravity is by far the weakest of the forces, which is a big mystery in physics. But that's an another show. Feel free to ask. Why is gravity so weak? It's called the hierarchy problem. Love to do an episode on that, but not today. If gravity were a billion billion billion billion times stronger than it is, it would still be the weakest force by billions and billions. It's just so weak, and the gravitational waves are tiny little things on top of the normal grav. So this isn't the normal gravity of the earth. Gravitational waves are something tiny on top of that, so you're taking something that is billions of times weaker than anything else in the universe.
And then you're taking a weaker version of that tiny little variations on that so gravitational waves are exceedingly weak. But that's a bad thing because it makes them hard to detect, but it's also a good thing. It's a good thing because gravitational waves don't really interact with matter. So they pass through the universe without any scattering or absorption. All the nasty stuff we have to deal with with light. Oh, there's some dust and absorbed all the light and so we can't get a good image of that supernova. Oh, our planet is opaque, so we can't see inside of it to know what's going on in our core. The light can't get out. That's not true with gravitational. Its gravitational is because they're so weak they barely interact with matter. And so they just sail on through and they sail on through the universe. Gravitational waves can go for billions of light years. And yeah, they'll get weaker because they're getting spread out in more volume. But they won't scatter. They won't get absorbed. They'll just keep on going.
So great gravitational waves exist. They do things which is mostly wave around. How do you get one? Like I said, you get one by wiggling. If you start wiggling around, which I greatly encourage you to do, then you are generating gravitational waves like Look, I'm I'm waving my arm right now. Can't you hear it? I am making gravitational waves and if you wave your arm right now, you are making gravitational waves. You just take mass and you accelerate it. Boom. Done. Gravitational waves. Easiest thing to make in the world. This does lead to something cool. I absolutely need to tell you about. I cannot resist it. It's called permanence. Anything, any mass or energy that is changing or accelerating will create gravitational waves, including gravitational waves. So if you're waving your arm around, you make some gravitational waves. Those gravitational waves are energy moving around which generate gravitational waves. So gravity waves generate gravitational waves, weaker versions of them, but still gravitational waves. Then those gravitational waves go on to make more gravitational waves. It keeps going and going and going with every iteration getting weaker and weaker and weaker. But when you add up all the contributions to all those infinite waves that are constantly created, you actually end up with a permanent distortion in space.
Gravitational waves permanently shift space time behind them from this stacking of gravitational waves. Once you trigger one, you can't stop it, and it leaves behind a very, very, very tiny but very, very real permanent gravitational wave presence. I. I thought that was cool, but like I said, they're weak. So technically, any accelerating mass makes gravitational noise. But if you wanna make anything appreciable, anything decent, you need some really beefy stuff. Most importantly, you need a lot of energy concentrated into as small a volume as possible. Imagine making a water wave. If you drop a little a little leaf on a pond, it's gonna make any hardly any wave at all. But if you drop a massive boulder on the pond, that's gonna make a big wave. So you you need to you need something big here with gravitational waves. Some good candidates for making decent gravitational waves might be black holes colliding neutron stars colliding black holes colliding with neutron stars, supernova exploding giant black holes, colliding giant black holes eating things.
And let's not forget the entire universe. What hoes have in common is a lot of mass, concentrated into a very small volume, doing something really quickly, like when black holes collide. You've got a lot of mass in those singularities, a lot of density, infinite density. I guess crashing into each other at nearly the speed of light. That's gonna be pretty serious when a star turns itself inside out and goes supernova. That's a lot of mass, a lot of energy, a lot of action. When a giant black hole is literally tearing apart a star limb from limb, that's a lot of mass, a lot of energy, a lot of density, a lot of gravitational waves. The early universe was a very chaotic place I'm talking about. When it was less than a second old, it was going through some radical phase transitions. Those radical phase transitions released gravitational waves that shook the entire cosmos. These are prime sources for gravitational waves and gravitational waves.
Because they pass through matter so easily, they let us see inside of it a supernova you can't see inside of a supernova because prior to the supernova is just a star and you can't see inside of stars. And then it explodes and all you see is the explosion, so you don't actually get to see and observe directly what's happening inside of a supernova as it's going off. But as it's going off, it's releasing gravitational waves, which just stay on through. And if you can detect those gravitational waves, you can see what's happening inside of a star that dies when two black holes collide in the middle of the night. That's black hole number one, black hole number two Space itself is black. That's not a lot of electromagnetic radiation coming off of that thing. You're not gonna see it with any telescope, but you can detect the gravitational waves released. Gravitational waves are powerful because they let us see things that we can't normally see. And when it comes to detection, this is where the templates come in and what Dr Tanaka was complaining about before I continue, I want to let you know that this episode of Asa Spaceman is brought to you by my friends at better help.
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That's better help HE LP dot com slash spaceman. Now back to our astro therapy session brought to you by not a licensed psychologist, but an astrophysicist, but good enough right? At least for now. If we're going to build gravitational wave detectors if we want to actually see there are all these things happening in the universe that are generating gravitational waves. Presumably, these gravitational waves are washing over the earth right Now there are gravitational waves sailing through you right now from distant events, from neutron stars colliding from giant black holes, eating things from the 1st 2nd of the universe itself washing over you. Right now we need to know what we're looking for. We needed to model the unique gravitational wave signal or or the fingerprint of each of these sources. All these different sources the supernovae, the black holes colliding, the black holes, eating things, the black holes doing other things, the black holes just being black holes.
All these different sources have different characteristic frequencies wavelengths, amplitudes, behaviors, patterns. And as gravitational waves progress throughout the universe, there are affected by cosmological red shift. They get red shifted just like light. Does they get stretched to lower frequencies, just like light does. So we need to figure out what we can detect. Like if a supernova goes off in our backyard. What? How strong is that gravitational wave when it hits the earth? What does that gravitational wave look like? If two black holes merge in a distant galaxy and the gravitational wave finally reaches the earth, how strong is that gravitational wave? What's its frequency? What's its amplitude. Does it have any particular patterns? Does it shift to higher amplitude or lower amplitude? Does it change frequencies? What does it do? We need to figure it out. So we need templates for this. It's like being able to identify bird calls. You stand in the middle of a forest or a jungle and hear all sorts of noises and what you want to do.
You you really wanted, I don't know the the the ruby throated golden warbler, and you really, really want to hear and spot the ruby. What did I just make up the ruby throated golden warbler? And it has a distinct call. So you're sitting here in a jungle and imagine you're sitting and you're hearing all sorts of noises. There's the wind rustling through the trees. There's the buzzing of insects. There's there's a howler monkey nearby, and you are listening through all these sounds. But you've got a template because you had an app and you listened on the app to what? The ruby throated? Why did I pick this? The ruby throated golden warbler? What it sounds like that was your template, and you're listening to all these noises and then you finally hear it. There it is, and it matches the template, and it it it rises above. You can select it here. There's all these noises, but you know that noise and that noise is the ruby throated golden warbler.
That was it. Gravitational ways. We need these templates. There's gravitational ways washing over us nonstop from sources across the universe. We need to know what we are hearing so we can identify it. Plus, when black holes collide, all sorts of different masses of black holes can be involved, and so they'll be different templates. All sorts of different spins can be involved. We need different templates. Sometimes those black holes can have accretion discs, which have their own voice to the party. So any templates for that? So in the 19 eighties, 19 nineties, early two thousands it was Template Town. If you wanted to be a relativist, you needed to work on templates because that's what everyone was doing was building templates so that future gravitational wave detectors would be able to spot that ruby throated golden warbler, for example, black hole collisions if it's, uh, a black hole A few times, the mass of the sun have a gravitational wave frequency of about 100 hertz.
That means that as the gravitational wave from these black holes washed over you, you would get stretched and squeezed about 100 times per second. As the wave passed through, you converted into sound. If we were to take 100 hertz as a sound wave that's actually audible to humans, check this out so that could be the template or the beginning of a template for detecting black hole collisions. If you see a gravitational wave and you've got your detector and you see something that hits the detector with a frequency of about 100 hertz boom, you got it. That's the beginning of a template. Things like supernova are higher frequency. Things like giant merging black holes are lower frequency. But now we know because we spent a couple of decades developing all the templates for what the gravitational wave, signature or fingerprint would look like from these different sources. But even though these gravitational waves are coming from all across the universe passing through you right now, as we speak distorting you, don't you feel those awkward hands on you?
You don't exactly feel them. Remember how I said they were weak? Check this out. Let me let me give you some numbers. You know antimatter, right? It is exactly like matter, but has opposite electric charge. And the cool thing about antimatter is that if you touch regular matter to antimatter, they annihilate and convert all of their mass into 100% energy. They convert it into high energy photons. Very, very cool. If you smash £1 of antimatter into £1 of normal matter, you have released the same amount of energy as a 19 megaton nuclear bomb. £1 like £1 that you can hold in your end of antimatter. Basically, as soon as it touches your hand because your hand is made of normal matter, the whole thing explodes and you've released more energy than a 19 megaton nuclear bomb. That's that's a lot. Now imagine taking our son and then another son made out of antimatter. So we have a son in the anti sun and you smash him together to see what happens. Here's what happens.
They blow up every single atom of hydrogen. Every single atom of helium smashes into every single atom of antigen anti helium, all that mass in an entire sun's mass converted into pure energy, £1 could do more damage than a nuclear bomb. One. Sun's worth of antimatter colliding with one son's worth of matter releases more energy than every star in the entire observable universe is releasing right now. So in that one second when the explosion happened, it is more energetic than every single star in the universe combined. That's a lot of energy. A typical black hole collision will release several times that up to hundreds of times that in the form of gravitational waves. Imagine that scenario, these two black holes. You can't even see them. It's silent. This is dark. There's no flash. There's no bang. There's no explosion. There are no fireworks. But in the merger process, they release more energy than 100 universes worth of stars, all in the form of gravitational waves.
If you were within, say, a kilometer of the event, the gravitational waves would rip you to shreds. But gravitational waves are so weak. If you were 1000 kilometers away from a black hole collision, you'd be totally fine, you know, maybe a little uncomfortable like you had too much gas, but it wouldn't really trouble you. That's how weak these are. More energy than 100 universes worth of stars and 1000 kilometers away. You would barely feel it by the time those same gravitational waves make it to the earth billions of light years away, they are washing over you. Right now they are stretching and squeezing you less than the width of a proton. Like I said, they're weak. So to detect them, you have to be really, really, really, really, really clever. Really not a little bit extremely clever, extremely sensitive. And we did it. We did it with something called LIGO LIGO, the Laser Interferometer gravitational wave Observatory.
The wave is hyphenated there with gravitational. So it doesn't appear in the acronym because otherwise it would come out as like and then be so. It's just LIGO. Here's how we did it. We we used a trick called interferometry where we took a laser and we shot it down a really long tunnel, and then we bounced it off a mirror and then we brought it back, back and forth, back and forth, back and forth, back and forth. We used the fact that light radiation is a wave itself. And like any waves, you can combine waves together. And if you combine them where it's peak to peak, everything amplifies. And if it's peak to trough, you can get waves to cancel out. This is like how your noise canceling headphones work because they meet all the incoming sounds with the exact opposite sound, and everything cancels out so you can tune your in interferometer so that, like no light comes back. And then if there's any little shift, if you have these mirrors for your laser just hanging from the ceiling, and then there's any little shift at all, you will break that perfect noise cancellation light cancellation effect and you'll be able to detect the movement.
The LIGO detector is two arms perpendicular to each other, so as the gravitational wave washes over the Earth, it changes the lengths of these arms by a tiny bit less than the width of a proton. But it's enough that it shows up in this interference pattern. Of course, this is way harder to do than it sounds. It took nearly 25 years for the LIGO collaboration to make it work. And that's because gravitational waves aren't the only things that make these giant mirrors at the ends of your tunnels move around. If a truck drives outside, if there was an earthquake on the other side of the world, if someone's eating a sandwich in the control room, there's all this noise and vibration. And in order to detect a gravitational wave, you needed a detector. Sensi sensitive enough that it could actually pick up signals that are smaller than the width of a proton. And so it took years and years and decades and decades to figure that out.
And then once you have the sensitivity, there are all sorts of other things that are causing those mirrors to move. And so you need to understand those sources of noise. So make sure you're not making a mistake. Like, imagine you're in your jungle. You're listening to your What was it? The ruby throated golden warbler, and you're trying to listen for it. And then a hurricane comes in and the hurricane may just make a random sound that happens to briefly sound like at least a part of the bird call of the ruby throated golden warbler. So the people behind LIGO, this massive collaboration, they had to understand where the noise might come from. They had to be able to filter it out. They had to understand their instrument. It took them 25 years of advancing technology and theory and fine tuning to make one good enough and to search for patterns in those signals. These mirrors are constantly vibrating from all sorts of things. Filter out the noise. Look for something that matched one of the templates, As you might imagine, a giant interferometer that is miles long, that's waiting for just anything to pass over.
It may not be the best at pointing to sources on the sky like, Yeah, we got a gravitational wave. Where to come? I don't know. So we needed multiple detectors. LIGO itself has 21 in Washington state, one in Louisiana. There's a third companion, the Virgo Collaboration, based in Italy, and by triangulating they can get better. It's still not very, very precise, but they can pick out the source of gravitational waves, and that's because they know the gravitational waves that travel the speed of light so the gravitational waves will hit one detector and then another and then a third. And depending on the timing, they know which direction, general direction of of the sky to look for. But still, it took 25 years, a quarter century. I haven't done a quarter century doing anything except maybe eating cheese. That's like, That's my life achievement but a quarter century working on one instrument to get it to work. That's dedication, and it's somewhat amusing. Back in 2015, they had already been working for a quarter century.
They were slowly working out the bugs. They were making the detectors more sensitive. They are understanding their noise. They had just finished upgrades, a series of upgrades, and they were in a test run When chirp that's right, chirp. On September 14th, 2015, a signal came through that matched one of the templates. This was a template of two black holes merging, but the research won't run the actual let's go look for gravitational waves. Run wasn't supposed to start for another three days. The people at the station who saw the chirp is that, Did you? Did you see what I just saw? Because the there's a chirp, there's a signal there's black holes merging. They didn't know if this was a blind test. This is something that the LIGO collaboration did very well. Would there be a team who's in charge of like fire drills? Basically, but for science? And they would insert signals in to see if the software, the noise cancellation, the template matching algorithms actually worked.
And so the and the people actually running it don't know when these tests are happening. So they got the signal. They're like, Ha ha ha, we're doing another file drill. We'll do another test, OK? We'll do the things we're supposed to do, which is alert The rest of the collaboration Surprise. It wasn't a test. They weren't even quite ready for it. But as soon as they developed the upgrades to bring to to increase their level of sensitivity right to the edge of where they thought black hole signals might be. Basically, as soon as they turned on the machine and it was sensitive enough to find black hole signals, they found black hole gravitational wave signals This chirp signal. It's called a chirp because this template, this gravitational wave pattern for merging black holes, has a very distinct shape to it, a signal to it, a very distinct fingerprint to it. Like once you hear the ruby throated golden warbler you you can never un hear it again. And when black holes merge as they get closer together in that last fraction of a second, they're close enough.
They're moving fast enough that they start to generate some real serious gravitational waves. And so you get a ramp up, the amplitude ramps up. The frequency increases because the black holes are getting closer and closer. And so they're stirring space time even faster. So the amplitude goes up, the frequency goes up and then the black holes merge and there's a big collapse. And then there's something called a ring down because the newly merged black hole is vibrating like this and then it comes down. It's over and done with in 0.2 seconds. This particular event called GW 150914 15 for the year 09, because it happened in September and then 14 because it was the 14th of September. It lasted 0.2 seconds. The frequency range ran from 35 hertz to 250 hertz And if we converted that to sound, you can actually hear it, which is a real treat because this is a podcast about astronomy. So I usually have to describe things with words. But this time we can all experience together, we can actually listen to it.
What I'm about to play for you is the actual chirp. The actual gravitational wave signal converted directly into sound. So the amplitude of the gravitation wave signal goes up. The amplitude of the sound wave will go up. The frequency of the gravitational wave will go up. The frequency of the sound wave will go up. It's from 35 hertz to 250 hertz. It lasts just 0.2 seconds. So we're I'm I'm gonna put it on. Repeat for a while so you can hear it. Check it out. This is what it sounds. If you could hear gravitational waves from merging black holes, this is what you would hear. Let me let me modify this a little bit. I'm gonna keep the timing, because remember, this whole thing happens in 0.2 seconds. These two black holes collide in that fraction of a second. But let me ramp up the frequency a little. So it's more in the middle of the range of human hearing what you heard from 35 hertz to 250 hertz is like, way down low. Let me let me adjust it. So it's right in the middle. Here.
Here, check it out. Go to patreon dot com slash BM Sutter to support the show. Did you hear that? OK, I'm I'm just kidding. Here it is. This is real folks. What you're hearing is a gravitational way of converted to sound a tiny ripple in space time no bigger than a proton generated when two black holes 1 35 times the mass of the sun, the other 30 times the mass of the sun collided with each other over 1.4 billion years ago. That's well before multicellular life appeared on the earth. As far as our observations can tell of this event, there was no light. There was no flash. There was no explosion. This all happened in complete silence. In complete darkness, two shadows merging in the dark. That one event released more energy in the form of gravitational waves than 50 universes worth of stars.
The entire event lasted for 0.2 seconds, and all that remains is that one little chirp in our detectors. More to come in Part two. Thank you to my top patreon contributors this month. That's patreon dot com slash PM Sutter to help keep the show going Matthew K, Justin Z, Justin G, Camino Duncan, M Coy D, Barbara K Dude, Robert MN eight H and F, Chris Cameron, NAIA aone, Tom B, Scott M, Rob H and Lowell T is your contributions and everyone else's that keeps this show going. Also, what keeps the show going are questions, tons of questions about gravitational waves. Eric M on email. Matthew S on email. Brandon be on email Sean El on email. Lothian 53 on patreon. Ray F on email at I its real name, Read it for the first time on Twitter. Scott M on email at J Rods 5 60 on Twitter at a Piper on Twitter.
Craig B on Facebook at ur on Twitter. Mike R on email, Mary T on Facebook at Wardo Computer on Twitter at Laser 314 on Twitter, Jason G on email and at Ken 987779331 on Twitter. Thank you, everyone, for your questions, and I'll see you next time for more complete knowledge of time and space.