WEBVTT - How LIGO Works 0:00:04.800 --> 0:00:14.840 With Technology Stuff. Hey there, and welcome to tex Stuff. 0:00:14.880 --> 0:00:18.239 I'm your host, Jonathan Strickland, and today I wanted to 0:00:18.280 --> 0:00:21.800 talk about something that was in the news recently, at 0:00:21.840 --> 0:00:26.560 least recently when I'm recording this episode. On February eleven, sixteen, 0:00:26.720 --> 0:00:29.280 that was, of course, the day when we got the 0:00:29.360 --> 0:00:33.960 confirmation from a collaboration of scientists that in fact, the 0:00:34.040 --> 0:00:38.800 Ligo Observatory had picked up a gravitational wave. And this 0:00:38.880 --> 0:00:43.000 was huge news around the world. And in case you 0:00:43.040 --> 0:00:45.720 were wondering, what the heck is this news all about? 0:00:45.840 --> 0:00:49.040 How did they pick up that gravitational wave? What what 0:00:49.200 --> 0:00:54.080 exactly is the technology powering our sensors to detect this stuff? 0:00:54.760 --> 0:00:56.480 How does it all work? That's what this episode is 0:00:56.520 --> 0:00:59.920 all about. So this was the very first time anyone 0:01:00.000 --> 0:01:03.680 had been able to measure a gravitational wave directly. So 0:01:03.800 --> 0:01:07.440 today we're gonna talk all about what that means and 0:01:07.480 --> 0:01:11.000 how it happened. Now, to begin with, we need to 0:01:11.080 --> 0:01:14.600 lay some groundwork and to to really get an understanding 0:01:14.680 --> 0:01:20.160 what gravitational waves are. So gravitational waves, ultimately, we're one 0:01:20.160 --> 0:01:25.080 of the predictions made by a certain Albert Einstein with 0:01:25.160 --> 0:01:29.040 his theory of general relativity. So in that theory, Einstein 0:01:29.080 --> 0:01:34.039 presented this idea that our universe is filled with spacetime. 0:01:34.480 --> 0:01:37.840 If you're a fan of science fiction, you have undoubtedly 0:01:37.959 --> 0:01:41.120 come across that term star trek is all about the 0:01:41.160 --> 0:01:43.560 spacetime continuum, and that you've got to be careful. You 0:01:43.560 --> 0:01:46.199 could rip a hole in the fabric of space time. 0:01:47.120 --> 0:01:50.480 As far as we know, that's not really that possible. Um. 0:01:50.520 --> 0:01:53.200 I mean, black holes could sort of be that maybe, 0:01:53.320 --> 0:01:58.880 But at any rate, spacetime itself is this calling it 0:01:58.960 --> 0:02:00.920 stuff is probably the wrong way of putting it, but 0:02:01.320 --> 0:02:05.560 it is like a fabric and mass hangs inside this fabric. 0:02:06.280 --> 0:02:09.400 And by mass, i'm talking about stuff like stars or 0:02:09.440 --> 0:02:14.440 even an entire solar systems or galaxies that hang in 0:02:14.760 --> 0:02:18.080 this fabric, and just like you would see in a 0:02:18.160 --> 0:02:22.720 two dimensional display, Uh, it ends up curving the fabric 0:02:22.919 --> 0:02:27.760 around the mass. Uh. We often talk about this in 0:02:27.919 --> 0:02:32.480 terms of a very simple example that's easy to imagine. Uh. 0:02:32.720 --> 0:02:35.280 You get some sort of stretchy material. Often you'll just 0:02:35.320 --> 0:02:38.359 hear someone say, Okay, get a trampoline. You've got a trampoline, 0:02:39.160 --> 0:02:43.280 and you put a big, heavy bowling ball on the trampoline, 0:02:43.560 --> 0:02:47.040 so that bowling ball is going to deform the trampoline surface. 0:02:47.240 --> 0:02:49.880 It's no longer going to be straight. It's going to 0:02:49.960 --> 0:02:52.720 end up curving around the bowling ball to some extent, 0:02:52.800 --> 0:02:55.880 creating kind of a dimple where the bowling ball has 0:02:56.000 --> 0:02:59.720 has created this impression inside the trampoline, and as long 0:02:59.760 --> 0:03:02.400 as the bowling ball is there, that impression is going 0:03:02.440 --> 0:03:05.400 to stay. This is sort of the like the way 0:03:05.480 --> 0:03:10.760 spacetime curves around giant masses like stars and and black 0:03:10.800 --> 0:03:14.360 holes things like that. Of course, we have to remember 0:03:14.400 --> 0:03:17.960 that spacetime is actually four dimensional, not a two dimensional 0:03:18.040 --> 0:03:20.360 thing like a trampoline. I mean, I know that trampolines 0:03:20.400 --> 0:03:23.760 technically have three dimensions, but we're really looking at a surface, 0:03:23.840 --> 0:03:27.120 so it's more like a two dimensional plane in reality. 0:03:27.200 --> 0:03:30.000 In spacetime it's four dimensional because you've got the three 0:03:30.320 --> 0:03:34.400 spatial dimensions plus time, and that is a little difficult 0:03:34.440 --> 0:03:37.560 to get your head around. But that's why we tend 0:03:37.600 --> 0:03:39.760 to look at this two dimensional example. It's a lot 0:03:39.760 --> 0:03:43.480 easier for us to imagine. So let's go a little 0:03:43.520 --> 0:03:46.520 further with that analogy to kind of talk about gravity. See, 0:03:46.560 --> 0:03:49.760 Einstein proposed that gravity was a manifestation of this curved 0:03:49.840 --> 0:03:53.640 space time. And if we take that trampoline example. Let's 0:03:53.640 --> 0:03:55.840 say that you have a regular trampoline. You haven't put 0:03:55.840 --> 0:03:57.920 the bowling ball on there yet, so it's a nice 0:03:57.920 --> 0:04:00.520 flat surface, and you have a marble, and you roll 0:04:00.600 --> 0:04:03.040 the marble across the surface of the trampoline. So if 0:04:03.040 --> 0:04:05.440 there's nothing else there, and if the trampoline is level, 0:04:05.520 --> 0:04:09.080 if the surfaces level, the marble should just roll in 0:04:09.120 --> 0:04:11.240 the straight line from one side of the trampoline to 0:04:11.240 --> 0:04:14.520 the other. No problem. Now let's say you put that big, 0:04:14.560 --> 0:04:17.080 heavy bowling ball on the trampoline. It creates that dimple, 0:04:17.520 --> 0:04:19.680 and then you try and roll the marble across the 0:04:19.680 --> 0:04:23.640 trampoline surface. Well, now that dimple is going to end 0:04:23.720 --> 0:04:26.120 up affecting the pathway of the marble. It's going to 0:04:26.160 --> 0:04:31.040 start to spiral inward toward the bowling ball. Ultimately it'll 0:04:31.120 --> 0:04:34.720 end up making contact with the bowling ball. And Einstein said, 0:04:34.760 --> 0:04:37.960 that's essentially what gravity is. It's that you've got these 0:04:38.600 --> 0:04:43.440 large masses that curves spacetime to the extent that smaller 0:04:43.480 --> 0:04:47.720 masses are spiraling inward toward the large mass. It's just 0:04:47.760 --> 0:04:50.800 happening on a scale that's much, much, much larger than 0:04:50.839 --> 0:04:55.840 any bowling ball marble example, But that this isn't essentially 0:04:55.920 --> 0:04:59.440 what we see when we see planets orbiting a sun, 0:04:59.839 --> 0:05:02.960 or or we see a moon orbiting a planet, or 0:05:03.040 --> 0:05:06.400 we see star systems orbiting a galaxy, you know, the 0:05:06.400 --> 0:05:10.560 center of a galaxy. And uh, it's all because of 0:05:10.640 --> 0:05:14.039 this curved spacetime. Now, all of that already is pretty 0:05:14.080 --> 0:05:16.320 heavy stuff. And keep in mind, there was not really 0:05:16.360 --> 0:05:21.960 any way to directly observe this. It was mostly the 0:05:21.960 --> 0:05:27.080 the just just Einstein using logic to work all this 0:05:27.160 --> 0:05:33.280 out and math, logic and math, and ultimately it fit 0:05:33.400 --> 0:05:36.000 with what we saw of the universe. But we weren't 0:05:36.000 --> 0:05:38.240 able to test a lot of this. But then it 0:05:38.279 --> 0:05:41.800 gets even more mind blowing because now we have to 0:05:41.800 --> 0:05:45.479 get to gravitational waves. So Einstein said that if a 0:05:45.520 --> 0:05:50.240 mass were large enough and either changed shape rapidly enough, 0:05:50.400 --> 0:05:54.120 or it changed its movement in some way, uh really 0:05:54.160 --> 0:05:57.160 really quickly, it would cause ripples of space time to 0:05:57.240 --> 0:06:01.640 move outward from that event at the speed of light. 0:06:02.240 --> 0:06:05.200 And those ripples are what we call gravitational waves, which 0:06:05.200 --> 0:06:08.200 are different from gravity waves. By the way, I have 0:06:08.279 --> 0:06:11.640 been known to accidentally say gravity waves instead of gravitational waves, 0:06:11.680 --> 0:06:14.440 but the two are different things. A gravity wave is 0:06:14.440 --> 0:06:18.599 a wave that exists because of gravity. In other words, 0:06:18.600 --> 0:06:21.080 it's a physical wave of some sort of fluid system, 0:06:21.120 --> 0:06:25.719 whether it's atmosphere or or water or some other liquid. Uh. 0:06:25.760 --> 0:06:28.520 That's a gravity wave on a planet's surface. It's not 0:06:28.600 --> 0:06:30.760 the same thing as a gravitational wave, which is really 0:06:30.800 --> 0:06:34.160 a ripple of spacetime, and like I said, it moves 0:06:34.160 --> 0:06:36.840 outward from that event at the speed of light um 0:06:36.920 --> 0:06:40.640 And stuff that could cause significant gravitational waves, things that 0:06:40.680 --> 0:06:43.400 would be big enough for us to potentially pick up 0:06:43.400 --> 0:06:45.880 here on Earth if we had the right equipment, would 0:06:45.880 --> 0:06:48.880 include things like two black holes orbiting or colliding with 0:06:48.880 --> 0:06:52.560 one another, which in fact, that was the event that 0:06:52.640 --> 0:06:56.640 we were able to pick up with the Ligo facilities. 0:06:56.720 --> 0:06:59.840 And I'll talk about those in just a bit. But 0:07:00.040 --> 0:07:02.599 there could be other stuff too, like neutron stars orbiting 0:07:02.640 --> 0:07:07.520 one another fast enough would generate gravitational waves, or a 0:07:07.560 --> 0:07:11.000 supernova explosion would create one as well. And each of 0:07:11.040 --> 0:07:14.120 these events give off a huge amount of energy, and 0:07:14.200 --> 0:07:17.360 some of that energy gets converted into making these gravitational waves. 0:07:17.400 --> 0:07:20.440 So one takeaway from this prediction something that Einstein said 0:07:20.440 --> 0:07:25.960 would happen is that any event that produces gravitational waves 0:07:26.200 --> 0:07:29.400 is an event in which energy is being lost, So 0:07:29.480 --> 0:07:33.040 you would expect to see less energy within that system 0:07:33.160 --> 0:07:36.960 afterward than before. Uh. And it would be a hundred 0:07:37.120 --> 0:07:41.160 years from the time of publication of the theory of 0:07:41.160 --> 0:07:45.040 general relativity to the time when scientists announced that they 0:07:45.040 --> 0:07:50.000 had detected a gravitational wave directly. And that's because gravitational 0:07:50.040 --> 0:07:53.840 waves are devilish lye difficult to detect. And that's some 0:07:53.960 --> 0:07:57.880 alliteration for you right there. So gravitational waves are invisible. 0:07:58.720 --> 0:08:01.840 They don't omit any sort of a electromagnetic radiation, so 0:08:01.880 --> 0:08:06.240 we can't see them. We can't detect them with radio detectors, 0:08:06.360 --> 0:08:10.480 nothing like that. Uh. And that makes it pretty tricky 0:08:10.560 --> 0:08:12.920 to figure out where they are. But they do just 0:08:13.000 --> 0:08:16.280 pass through the universe. They don't get absorbed or scattered 0:08:16.400 --> 0:08:19.760 the way electromagnetic radiation does. If you hold up a 0:08:19.800 --> 0:08:22.840 mirror and light hits the mirror, light will bounce off 0:08:22.880 --> 0:08:25.520 the mirror. That's not the case with gravitational waves. They 0:08:25.520 --> 0:08:29.680 pass right through. UH. So it's a very different thing 0:08:29.880 --> 0:08:36.480 than electromagnetic radiation. UM. And while they're generated from enormous events. 0:08:36.559 --> 0:08:39.320 The gravitational waves aren't very strong by the time they 0:08:39.320 --> 0:08:43.600 get to Earth. They are pretty weak, so weak that 0:08:43.720 --> 0:08:46.280 you would need an incredibly sensitive tool in order to 0:08:46.320 --> 0:08:48.480 pick them up. And also you have to be searching 0:08:48.520 --> 0:08:51.640 at the right time, because if the event that generated 0:08:51.640 --> 0:08:55.920 the gravitational waves happened a billion years ago, but the 0:08:56.000 --> 0:09:00.120 location is four billion light years from Earth, then we 0:09:00.160 --> 0:09:03.520 would have to wait another three billion years for those 0:09:03.600 --> 0:09:06.240 gravitational waves to get to us, because again, they travel 0:09:06.280 --> 0:09:09.360 at the speed of light, that's their limit. So you 0:09:09.400 --> 0:09:10.719 have to be at the right place at the right 0:09:10.720 --> 0:09:14.000 time to pick these things up. And uh, and in 0:09:14.080 --> 0:09:18.679 some cases you might argue that that's incredibly fortuitous. Although 0:09:19.400 --> 0:09:23.160 to be fair, uh, it looks like the events that 0:09:23.240 --> 0:09:27.120 could generate gravitational waves happened pretty frequently throughout the universe. 0:09:27.400 --> 0:09:31.360 But the universe is huge, so if they're happening far away, 0:09:31.400 --> 0:09:33.800 far enough away, it will take a very long time 0:09:33.840 --> 0:09:37.080 for that information to get to us. So before the 0:09:37.080 --> 0:09:41.360 announcement on February eleven, sixteen, scientists had observed phenomena that 0:09:41.520 --> 0:09:45.800 supported the existence of gravitational waves. But we're not direct 0:09:46.000 --> 0:09:49.920 observations of a gravitational wave. Here's an example. A pair 0:09:49.960 --> 0:09:53.640 of astronomers in Puerto Rico in the nineteen seventies noticed 0:09:53.679 --> 0:09:58.080 that there was a binary pulsar system and they went 0:09:58.160 --> 0:10:01.200 back to the theory of general relative because this was 0:10:01.200 --> 0:10:03.959 a sort of system that would be exactly the type 0:10:03.960 --> 0:10:08.720 to generate gravitational waves according to the predictions from general relativity, 0:10:08.880 --> 0:10:12.480 and because general relativity predicted, hey, if it can create 0:10:12.559 --> 0:10:17.120 gravitational waves, it's going to lose energy over time. They 0:10:17.360 --> 0:10:20.320 ended up coming up with the hypothesis that, well, over time, 0:10:20.400 --> 0:10:24.079 this binary pulsar system should start to slow down because 0:10:24.120 --> 0:10:27.040 it's it's losing energy. It can't keep up at the 0:10:27.040 --> 0:10:31.480 speed it's going. So they decided to keep an eye 0:10:31.520 --> 0:10:33.880 on it. And by keeping an eye on it, I 0:10:33.880 --> 0:10:38.720 mean they continued to observe this pulsar system over the 0:10:38.720 --> 0:10:41.680 course of eight years, and by the end of the 0:10:41.720 --> 0:10:44.920 eight year period, they were comparing the findings they were 0:10:44.920 --> 0:10:48.280 observing to the predictions made by general relativity, and they 0:10:48.320 --> 0:10:51.760 were matching up. It was. It was unfolding exactly the 0:10:51.800 --> 0:10:55.920 way Einstein predicted it should unfold based upon his theory 0:10:55.920 --> 0:10:59.400 of general relativity, which is incredible when you think about 0:10:59.400 --> 0:11:02.680 it that the observations are matching up so neatly against 0:11:02.679 --> 0:11:07.360 the predictions. Uh, you know, it just shows how how 0:11:07.520 --> 0:11:11.480 keenly aware Einstein was of how our universe appears to work. 0:11:11.760 --> 0:11:16.480 Keeping in mind that general relativity, while an amazing idea 0:11:16.840 --> 0:11:22.880 collection of ideas, really it doesn't encompass everything that we know, 0:11:23.080 --> 0:11:26.480 right it doesn't. It doesn't really address quantum mechanics, for example, 0:11:27.400 --> 0:11:29.480 at least not in a way that incorporates it with 0:11:30.280 --> 0:11:35.120 classical physics. But based upon what it did cover, it 0:11:35.160 --> 0:11:40.360 seems like it was an incredibly accurate theory alright. So 0:11:41.800 --> 0:11:45.199 this was really considered strong but indirect support of gravitational 0:11:45.200 --> 0:11:50.280 waves because again the astronomers didn't observe gravitational waves directly. 0:11:50.320 --> 0:11:53.200 They couldn't see them or detect them, but they could 0:11:53.200 --> 0:11:56.920 see the effects, and again it was matching up with 0:11:56.960 --> 0:12:00.000 the predictions made from general relativity, so it was good 0:12:00.040 --> 0:12:04.319 it indirect evidence that gravitational waves existed. Then there was 0:12:04.360 --> 0:12:06.839 an event a couple of years ago that you might 0:12:06.880 --> 0:12:12.079 have heard about, when a team of researchers working on 0:12:12.120 --> 0:12:17.480 the BICEP two telescope, which is an an Antarctica, had 0:12:17.480 --> 0:12:21.280 announced that they thought they might have discovered evidence of 0:12:21.320 --> 0:12:28.360 gravitational waves that supported a hypothesis called cosmic inflation. That's 0:12:28.360 --> 0:12:30.480 a lot of information right there, So let me explain 0:12:30.520 --> 0:12:35.320 what all that means. Cosmic inflation is a hypothesis that 0:12:35.360 --> 0:12:38.760 relates to the Big Bang theory. So, with the Big 0:12:38.760 --> 0:12:42.200 Bang theory, you've got this event in which the universe 0:12:42.400 --> 0:12:47.400 undergoes a period of rapid expansion. Cosmic inflation is kind 0:12:47.440 --> 0:12:52.440 of that rapid expansion on steroids. The idea being that, well, 0:12:52.600 --> 0:12:55.160 when we look at our universe and we look at 0:12:55.200 --> 0:12:59.559 the the what we can observe, it appears that are 0:12:59.600 --> 0:13:02.160 observed aitions don't quite match up with what we would 0:13:02.160 --> 0:13:08.720 expect if we had, uh, just steady expansion since the 0:13:08.760 --> 0:13:12.200 Big Bang. In other words, we look at all the 0:13:12.240 --> 0:13:14.600 information we have available to us, and it looks to 0:13:14.679 --> 0:13:17.839 us that it doesn't quite match up. Something's got to 0:13:17.880 --> 0:13:22.800 be wrong. Well, one possible explanation is that shortly after 0:13:22.840 --> 0:13:25.880 the Big Bang, and by shortly I mean tend to 0:13:25.960 --> 0:13:29.800 the negative thirty six power seconds after the Big Bang. 0:13:30.400 --> 0:13:32.800 So you take a ten, you put a decimal point 0:13:32.800 --> 0:13:35.160 behind the tin, then you move the decimal point to 0:13:35.200 --> 0:13:39.319 the left thirties six times did you put seconds behind that. 0:13:39.360 --> 0:13:41.840 We're talking a fraction of a fraction of a fraction 0:13:41.840 --> 0:13:47.880 of a second. The universe underwent massive expansion, and it 0:13:48.000 --> 0:13:51.080 only lasted from from that point to about ten to 0:13:51.120 --> 0:13:55.160 the negative thirty third power or thirty second power seconds. 0:13:55.600 --> 0:14:01.760 So again an instant. It's it's completely unimaginable, at least 0:14:01.880 --> 0:14:05.160 for myself, how short an amount of time this was. 0:14:05.640 --> 0:14:10.000 But that's how how quickly the universe expanded, uh significantly, 0:14:10.640 --> 0:14:14.960 and then it slowed, but it continued to expand. Now, 0:14:15.120 --> 0:14:19.240 if in fact cosmic inflation is correct, it solves a 0:14:19.320 --> 0:14:22.080 lot of the problems we have between the what we 0:14:22.160 --> 0:14:25.280 observe today and what we believe happened with the Big 0:14:25.320 --> 0:14:30.880 Bang um and reconciles those differences. If cosmic inflation is wrong, 0:14:31.280 --> 0:14:34.680 then something else that we believe is wrong. Right. It 0:14:34.760 --> 0:14:38.920 means that what we observe either isn't representative of reality 0:14:39.040 --> 0:14:42.320 somehow we're not getting a big enough picture to understand it, 0:14:42.440 --> 0:14:45.120 or that the Big Bang theory itself is flawed in 0:14:45.160 --> 0:14:49.200 some fundamental way. So the BICEP two team, what they 0:14:49.240 --> 0:14:52.920 were looking for was some evidence of gravitational waves that 0:14:52.960 --> 0:14:56.640 would have been generated during the Big Bang this would 0:14:56.760 --> 0:15:00.160 end up supporting the cosmic inflation hypothesis. And the way 0:15:00.200 --> 0:15:02.120 they did this was they were looking at the cosmic 0:15:02.200 --> 0:15:06.880 microwave background or c MB. Now, the cosmic microwave background 0:15:06.920 --> 0:15:12.640 emerged about three hundred eighty thousand years after the Big Bang. Uh. 0:15:12.680 --> 0:15:14.880 This was still a period where the universe was so 0:15:15.000 --> 0:15:17.440 dense that light could not pass through it. It was 0:15:17.600 --> 0:15:21.720 dark and dense, But the cosmic microwave background formed around 0:15:21.760 --> 0:15:28.840 that time, and the hypothesis stated, well, gravitational waves would 0:15:28.920 --> 0:15:34.360 have affected the cosmic microwave background, polarizing some of those uh, 0:15:34.440 --> 0:15:38.120 some of those particles really not particles, but some of 0:15:38.120 --> 0:15:42.080 the energy polarizing some of the cosmic microwave background in 0:15:42.120 --> 0:15:45.280 such a way that if you were to observe it, 0:15:45.360 --> 0:15:49.000 you could see the effect of a gravitational wave passing 0:15:49.080 --> 0:15:54.160 through the CMB. UH. And then as the universe expand 0:15:55.040 --> 0:15:59.600 expanded rather uh, that that mark would also expand. It's 0:15:59.680 --> 0:16:03.600 kind of like imagine leaving a fingerprint on some sort 0:16:03.600 --> 0:16:07.760 of stretchy material and then stretching that material out. The 0:16:07.800 --> 0:16:10.840 fingerprint is still there. It's deformed, but still there. That's 0:16:10.880 --> 0:16:12.920 what the Bicept two team was looking for. Was this 0:16:13.640 --> 0:16:17.880 pattern in the CMB that would indicate that gravitational waves 0:16:17.920 --> 0:16:20.640 from the Big Bang had passed through, and if they 0:16:20.680 --> 0:16:23.680 found that, that would be a huge support for cosmic inflation. 0:16:24.640 --> 0:16:27.600 And in the spring of they announced that they believed 0:16:27.760 --> 0:16:32.680 they had found such evidence, and they also invited other 0:16:32.760 --> 0:16:35.400 researchers to take a look at their data and see 0:16:35.440 --> 0:16:39.920 if it was verifiable or maybe they overlooked something. And 0:16:40.040 --> 0:16:43.920 in the fall often another team said, we're sorry, but 0:16:44.000 --> 0:16:48.680 it looks to us like space dust might have created 0:16:48.680 --> 0:16:52.760 a false positive that what you thought it was the 0:16:53.000 --> 0:16:56.360 polarized CMB that you had been looking for was actually 0:16:56.440 --> 0:16:59.400 just space dust that's not actually part of the CMB. 0:17:00.520 --> 0:17:03.840 And uh so that ended up kind of putting a 0:17:04.760 --> 0:17:08.200 dampener on the whole celebration of finding gravitational waves to 0:17:08.200 --> 0:17:12.240 support cosmic inflation. But even if it was completely verified, 0:17:12.280 --> 0:17:15.640 even if BICEP two had irrefutable evidence that they had 0:17:15.640 --> 0:17:20.560 found the presence of gravitational waves through a uh you know, 0:17:20.920 --> 0:17:24.639 the way it affected the CNB, even then that's not 0:17:24.840 --> 0:17:28.600 direct detection. It's still indirect. You're looking at the way 0:17:28.680 --> 0:17:34.280 it's affected something else. So uh, you know, again, we're 0:17:34.280 --> 0:17:36.720 still not discovering one and and part of that is 0:17:36.760 --> 0:17:39.640 that BICEP two is a telescope. It's looking at through 0:17:40.040 --> 0:17:44.000 the electromagnetic spectrum, and again, gravitational waves don't show up 0:17:44.040 --> 0:17:46.879 that way, So no telescope would help you find a 0:17:46.880 --> 0:17:50.400 gravitational wave directly. You might be able to find how 0:17:50.400 --> 0:17:54.920 it affected something else, but not the wave itself. Now 0:17:54.960 --> 0:17:58.120 that's not the case with the LIGO observatories. Actually it's 0:17:58.160 --> 0:18:03.880 technically one observatory, but it has four different facilities, two detectors, 0:18:04.440 --> 0:18:07.800 UH and to research facilities that are all part of 0:18:07.800 --> 0:18:12.520 the LIGO observatory. LIGO itself is an acronym and it 0:18:12.600 --> 0:18:18.840 stands for Laser Interferometer Gravitational Wave Observatory. So it's a 0:18:18.960 --> 0:18:21.760 pair of giant detectors built on the surface of the Earth. 0:18:21.800 --> 0:18:27.440 One is located in Hanford, Washington, the other is in Livingston, Louisiana. 0:18:27.640 --> 0:18:31.080 Now they're about just a little under two thousand miles 0:18:31.119 --> 0:18:34.680 apart or just over three thousand kilometers apart from each other. 0:18:35.280 --> 0:18:37.760 And that's really important. I'll explain why in a little bit. 0:18:38.920 --> 0:18:40.639 So to understand how they work, we also have to 0:18:40.640 --> 0:18:44.520 talk about something else that gravitational waves do. As they 0:18:44.560 --> 0:18:51.200 pass through space, they stretch and compress space itself. So again, 0:18:51.240 --> 0:18:52.520 if you were to if you were to take a 0:18:52.520 --> 0:18:56.440 piece of elastic, Let's say you've got a rubber band, 0:18:56.840 --> 0:19:00.639 a nice thick rubber band, and you cut it so 0:19:00.720 --> 0:19:03.520 that it's just one strip. When you pull on that 0:19:03.600 --> 0:19:07.760 rubber band, it stretches along the line where you're applying force. 0:19:08.600 --> 0:19:12.480 So it stretches in that direction, in the perpendicular direction 0:19:13.280 --> 0:19:17.560 ninety degrees from where you're pulling. It compresses, it gets 0:19:17.800 --> 0:19:21.480 more narrow, and then when you let it return to 0:19:21.520 --> 0:19:25.000 its normal shape, it gets you know, the the long 0:19:25.119 --> 0:19:28.199 part ends up getting shorter and the narrow part ends 0:19:28.240 --> 0:19:32.320 up getting wider as a result, gravitational waves do this 0:19:32.359 --> 0:19:36.160 to reality. They do this to actual space. They stretch 0:19:36.240 --> 0:19:39.680 and compress, and it happens several times as the wave 0:19:39.720 --> 0:19:43.240 oscillates through. Really, I should just say as the wave 0:19:43.280 --> 0:19:48.199 passes through rather than oscillates. Uh, the distortion oscillates, but 0:19:48.280 --> 0:19:52.040 the wave passes through. So that means the actual distance 0:19:52.240 --> 0:19:57.200 changes between two points as that gravitational wave passes through 0:19:57.200 --> 0:19:59.600 that area. So if we were to magnify this effect, 0:19:59.680 --> 0:20:05.159 and I mean magnify it to a ludicrous degree, you 0:20:05.200 --> 0:20:07.280 would be able to see it. You would actually be 0:20:07.320 --> 0:20:10.520 able to witness this. You could stand ten feet away 0:20:10.560 --> 0:20:14.359 from someone else, and when the gravitational wave passes through, 0:20:14.880 --> 0:20:16.639 it would make it look like the two of you 0:20:16.680 --> 0:20:19.359 suddenly got further away and then closer to each other, 0:20:19.400 --> 0:20:21.320 and then further away and closer to each other, even 0:20:21.320 --> 0:20:25.719 though you haven't moved anywhere, because the distance itself is 0:20:25.760 --> 0:20:31.720 stretching and compressing. So why don't we see that? I mean, 0:20:31.720 --> 0:20:34.760 if the celestial events that produce gravitational waves happen on 0:20:34.800 --> 0:20:37.959 the order of something like every fifteen minutes, why are 0:20:38.040 --> 0:20:42.639 we all noticing this wibbly wobbly effect. Well, it's because 0:20:42.640 --> 0:20:47.520 the actual distortion that happens here on Earth is much 0:20:47.920 --> 0:20:52.880 much much smaller in magnitude, so much more, so much 0:20:52.920 --> 0:20:56.919 smaller that it's difficult to even explain. But if you 0:20:56.960 --> 0:21:00.879 were to have a supernova explode in the Milky Way galaxy, 0:21:01.000 --> 0:21:05.760 in our galaxy, the gravitational waves generated by that explosion 0:21:06.760 --> 0:21:10.080 would maybe be powerful enough to distort the distance between 0:21:10.160 --> 0:21:13.439 the Earth and the Sun by about the diameter of 0:21:13.480 --> 0:21:19.480 a hydrogen atom, so not noticeable to any degree, and 0:21:19.720 --> 0:21:22.879 not at least to human senses. So if you were 0:21:22.920 --> 0:21:24.719 to even go on a smaller scale, Let's say that 0:21:24.760 --> 0:21:28.199 you you pick two points that are a kilometer apart 0:21:28.280 --> 0:21:31.760 here on the surface of the Earth, the amount of 0:21:31.760 --> 0:21:35.080 distortion would be equivalent to a few thousands of the 0:21:35.200 --> 0:21:38.720 diameter of a proton. So you're talking about a sub 0:21:38.760 --> 0:21:42.880 atomic particle, and just a tiny, tiny, tiny fraction of 0:21:42.920 --> 0:21:46.600 that subatomic particles diameter would be the amount of distortion 0:21:46.840 --> 0:21:50.080 that would happen across a kilometer worth of distance here 0:21:50.119 --> 0:21:54.800 on Earth. Again, that means it's so small that it's 0:21:55.280 --> 0:21:59.200 incredibly difficult to detect, so much so that Einstein himself 0:22:00.200 --> 0:22:02.920 was pretty sure we would never be able to directly 0:22:03.000 --> 0:22:06.480 detect gravitational waves because he could not imagine a system 0:22:06.520 --> 0:22:09.560 that would be sensitive enough to pick up such a 0:22:09.640 --> 0:22:14.679 minute change, a distortion that's happening so quickly because it's 0:22:14.720 --> 0:22:18.200 a fraction of a second, and it's so small as 0:22:18.240 --> 0:22:23.280 to be unnoticeable. So the other problem here is not 0:22:23.359 --> 0:22:26.520 just that it's such a very tiny effect that lasts 0:22:26.520 --> 0:22:28.960 a short amount of time. It's also that a lot 0:22:29.000 --> 0:22:32.399 of other stuff could create false positives. You can have 0:22:32.440 --> 0:22:38.760 incredibly sensitive instrumentation, but if that instrument is really really sensitive. 0:22:39.280 --> 0:22:42.760 Any sort of interference could set off and you could 0:22:42.840 --> 0:22:46.560 end up getting false readings. So a change in air 0:22:46.600 --> 0:22:52.600 pressure or temperature, or seismic activity, even a heavy truck 0:22:52.680 --> 0:22:56.879 driving nearby could set off false results. So you'd have 0:22:56.920 --> 0:22:59.600 to come up with a really clever way to measure distortion, 0:22:59.680 --> 0:23:03.600 to limit vibration, and to eliminate the chance that it 0:23:03.680 --> 0:23:06.560 was a false positive. And LEGO is the answer to 0:23:06.640 --> 0:23:10.439 all of that. So the Lego Observatory is actually the 0:23:10.440 --> 0:23:14.959 result of decades of collaborative work among different scientific research 0:23:15.000 --> 0:23:19.280 centers and international bodies and universities, and all started back 0:23:19.320 --> 0:23:23.040 in nineteen seventy nine. That's when the National Science Foundation 0:23:23.080 --> 0:23:25.600 approved funds for cal Tech and m i T to 0:23:25.680 --> 0:23:30.160 develop laser interferometer research and development. And a few years later, 0:23:30.200 --> 0:23:32.760 in nineteen eighty three, Caltech and m i T submitted 0:23:32.760 --> 0:23:38.240 a proposal for a kilometer scale detector. Uh. But keep 0:23:38.240 --> 0:23:40.520 in mind, all right, so nineteen seventy nine you get 0:23:40.520 --> 0:23:44.680 the funding for R and D three, there's the submission 0:23:44.680 --> 0:23:49.640 of a proposal for a kilometer scale detector. There wouldn't 0:23:49.680 --> 0:23:54.240 be approval for a detector until nineteen nine, so almost 0:23:54.320 --> 0:23:59.920 a decade later, and which turns out was probably a 0:24:00.119 --> 0:24:05.280 k because we really didn't have the technological ability to 0:24:05.440 --> 0:24:08.679 detect things on a scale small enough to register a 0:24:08.720 --> 0:24:12.639 gravitational wave in the first place. But but still, you know, 0:24:12.800 --> 0:24:15.280 a decade's delay before you even get approval is still 0:24:15.320 --> 0:24:21.800 pretty rough. Construction didn't begin until nine The inauguration of 0:24:21.840 --> 0:24:26.280 the Ligo Observatory took place in nineteen nine, but even 0:24:26.359 --> 0:24:30.160 then that didn't mean that the the observatory was online 0:24:30.200 --> 0:24:33.560 collecting data. It didn't do that until two thousand two. 0:24:34.720 --> 0:24:39.200 And here's the kicker. Eventually scientists came to the conclusion 0:24:39.320 --> 0:24:43.520 that this Ligo Observatory was not sensitive enough to detect 0:24:43.560 --> 0:24:46.480 gravitational waves. That despite the fact that it was this 0:24:47.320 --> 0:24:52.000 large UH detector or pair of large detectors, actually because 0:24:52.040 --> 0:24:56.280 again one in Louisiana one in Washington, it wasn't sensitive 0:24:56.440 --> 0:25:00.680 enough to be effective. So it was not quite back 0:25:00.720 --> 0:25:03.239 to the drawing board. But it didn't mean that they 0:25:03.280 --> 0:25:07.520 had to think about how they would upgrade these facilities 0:25:07.960 --> 0:25:10.199 so that they could be sensitive enough to pick up 0:25:10.240 --> 0:25:13.879 a gravitational wave. So in twos ten Ligo went offline 0:25:14.080 --> 0:25:19.159 to undergo a big overhaul, and it took four years 0:25:19.200 --> 0:25:22.840 of construction and testing to get it into shape, and 0:25:22.920 --> 0:25:26.359 another year to set it up for new observations, which 0:25:26.400 --> 0:25:28.720 means that it wasn't until twenty fifteen that it was 0:25:28.760 --> 0:25:32.280 ready to come back online. By now it's called the 0:25:32.320 --> 0:25:36.760 Advanced Ligo Observatory, and it began collecting data in September. 0:25:39.119 --> 0:25:44.080 Literally days after it had come online, it picked up 0:25:44.119 --> 0:25:48.159 a gravitational wave. So that's pretty phenomenal that just a 0:25:48.200 --> 0:25:51.199