WEBVTT - RERUN: How LIGO Works 0:00:04.120 --> 0:00:07.160 Get in touch with technology with tech Stuff from how 0:00:07.200 --> 0:00:14.000 stuff Works dot com. Hey everybody, and welcome to tech Stuff. 0:00:14.040 --> 0:00:16.680 I'm your host, Jonathan Strickland. I'm an executive producer with 0:00:16.720 --> 0:00:18.599 How Stuff Works in my Heart Radio, and I love 0:00:18.840 --> 0:00:24.000 all things tech. If you're wondering why I said it 0:00:24.000 --> 0:00:26.080 that way, is because I was watching my producer Tari, 0:00:26.160 --> 0:00:28.520 who likes to try and lip sync as I do 0:00:28.640 --> 0:00:30.840 my intro, and sometimes I tried to throw her off 0:00:30.880 --> 0:00:33.120 on purpose. And you, guys, get to enjoy the fruits 0:00:33.159 --> 0:00:35.680 of my labor. You also are going to get to 0:00:35.760 --> 0:00:38.680 enjoy a classic episode of tech Stuff because I'm still 0:00:38.720 --> 0:00:42.839 on vacation and by now I'm sure I'm deep in 0:00:42.840 --> 0:00:47.839 Harry Potter World probably, So this classic episode is all 0:00:47.920 --> 0:00:53.440 about Howlego works. This was the facility that detected gravitational 0:00:53.479 --> 0:00:57.160 waves a few years ago, which was a big, big 0:00:57.200 --> 0:01:01.000 deal in the science world. It went from talking about 0:01:01.080 --> 0:01:06.839 a hypothetical effect to detecting said hypothetical effect does proving 0:01:06.880 --> 0:01:09.880 it's not just hypothetical. So I hope you enjoy this 0:01:09.959 --> 0:01:15.199 classic episode. The Ligo Observatory had picked up a gravitational wave, 0:01:16.040 --> 0:01:20.040 and this was huge news around the world and in 0:01:20.120 --> 0:01:22.760 case you were wondering, what the heck is this news 0:01:22.760 --> 0:01:25.480 all about? How did they pick up that gravitational wave? 0:01:26.120 --> 0:01:30.440 What what exactly is the technology powering our sensors to 0:01:30.680 --> 0:01:33.360 detect this stuff? How does it all work? That's what 0:01:33.440 --> 0:01:36.640 this episode is all about. So this was the very 0:01:36.680 --> 0:01:39.520 first time anyone had been able to measure a gravitational 0:01:39.560 --> 0:01:44.039 wave directly. So today we're gonna talk all about what 0:01:44.200 --> 0:01:47.120 that means and how it happened. Now, to begin with, 0:01:48.160 --> 0:01:51.080 we need to lay some groundwork and to to really 0:01:51.080 --> 0:01:57.240 get an understanding what gravitational waves are. So gravitational waves, ultimately, 0:01:57.280 --> 0:02:00.560 we're one of the predictions made by a certain Albert 0:02:00.560 --> 0:02:05.720 Einstein with this theory of general relativity. So in that theory, 0:02:06.000 --> 0:02:11.560 Einstein presented this idea that our universe is filled with spacetime. 0:02:12.000 --> 0:02:15.400 If you're a fan of science fiction, you have undoubtedly 0:02:15.480 --> 0:02:18.680 come across that term star trek is all about the 0:02:18.720 --> 0:02:20.959 space time continuum, and that you've got to be careful. 0:02:21.040 --> 0:02:23.720 You could rip a hole in the fabric of space time. 0:02:24.639 --> 0:02:28.040 As far as we know, that's not really that possible. Um, 0:02:28.080 --> 0:02:30.760 I mean, black holes could sort of be that maybe, 0:02:30.840 --> 0:02:36.440 But at any rate, spacetime itself. Is this calling it 0:02:36.520 --> 0:02:38.440 stuff is probably the wrong way of putting it. But 0:02:38.880 --> 0:02:43.079 it is like a fabric and mass hangs inside this fabric. 0:02:43.840 --> 0:02:46.960 And by mass, i'm talking about stuff like stars or 0:02:46.960 --> 0:02:51.960 even an entire solar systems or galaxies that hang in 0:02:52.320 --> 0:02:55.600 this fabric, and just like you would see in a 0:02:55.680 --> 0:03:00.320 two dimensional display, Uh, it ends up curving the brick 0:03:00.480 --> 0:03:05.320 around the mass. Uh. We often talk about this in 0:03:05.440 --> 0:03:10.040 terms of a very simple example that's easy to imagine. Uh. 0:03:10.240 --> 0:03:12.840 You get some sort of stretchy material. Often you'll just 0:03:12.880 --> 0:03:15.919 hear someone say, okay, get a trampoline. You've got a trampoline, 0:03:16.680 --> 0:03:20.800 and you put a big, heavy bowling ball on the trampoline. 0:03:21.120 --> 0:03:24.600 So that bowling ball is going to deform the trampoline surface. 0:03:24.760 --> 0:03:27.440 It's no longer going to be straight. It's going to 0:03:27.520 --> 0:03:30.280 end up curving around the bowling ball to some extent, 0:03:30.360 --> 0:03:33.440 creating kind of a dimple where the bowling ball has 0:03:33.520 --> 0:03:37.280 has created this impression inside the trampoline, and as long 0:03:37.280 --> 0:03:39.960 as the bowling ball is there, that impression is going 0:03:40.000 --> 0:03:42.920 to stay. This is sort of the like the way 0:03:43.000 --> 0:03:48.760 spacetime curves around giant masses like stars and black holes, 0:03:48.880 --> 0:03:52.040 things like that. Of course, we have to remember that 0:03:52.120 --> 0:03:55.720 spacetime is actually four dimensional, not a two dimensional thing 0:03:55.760 --> 0:03:58.320 like a trampoline. I mean, I know that trampolines technically 0:03:58.360 --> 0:04:01.320 have three dimensions, but we're really looking at a surface, 0:04:01.360 --> 0:04:04.640 so it's more like a two dimensional plane. In reality, 0:04:04.760 --> 0:04:07.560 In spacetime it's four dimensional because you've got the three 0:04:07.880 --> 0:04:11.960 spatial dimensions plus time, and that is a little difficult 0:04:11.960 --> 0:04:15.080 to get your head around. But that's why we tend 0:04:15.120 --> 0:04:17.240 to look at this two dimensional example. It's a lot 0:04:17.320 --> 0:04:21.039 easier for us to imagine. So let's go a little 0:04:21.040 --> 0:04:23.800 further with that analogy to kind of talk about gravity. 0:04:23.880 --> 0:04:26.840 See Einstein proposed that gravity was a manifestation of this 0:04:26.920 --> 0:04:30.839 curved space time. And if we take that trampoline example, 0:04:30.960 --> 0:04:33.240 Let's say that you have a regular trampoline. You haven't 0:04:33.240 --> 0:04:35.200 put the bowling ball on there yet, so it's a 0:04:35.279 --> 0:04:37.720 nice flat surface, and you have a marble, and you 0:04:37.880 --> 0:04:40.440 roll the marble across the surface of the trampoline. So 0:04:40.480 --> 0:04:43.000 if there's nothing else there, and if the trampoline is level, 0:04:43.080 --> 0:04:46.600 if the surfaces level, the marble should just roll in 0:04:46.640 --> 0:04:48.760 the straight line from one side of the trampoline to 0:04:48.800 --> 0:04:52.080 the other. No problem. Now, let's say you put that big, 0:04:52.080 --> 0:04:54.640 heavy bowling ball on the trampoline. It creates that dimple, 0:04:55.080 --> 0:04:57.200 and then you try and roll the marble across the 0:04:57.240 --> 0:05:00.960 trampoline surface. Well, now that dim bowl is going to 0:05:01.080 --> 0:05:03.560 end up affecting the pathway of the marble. It's going 0:05:03.600 --> 0:05:08.320 to start to spiral inward toward the bowling ball. Ultimately 0:05:08.360 --> 0:05:11.159 it'll end up making contact with the bowling ball. And 0:05:11.440 --> 0:05:14.880 Einstein said, that's essentially what gravity is. It's that you've 0:05:14.920 --> 0:05:20.040 got these large masses that curves spacetime to the extent 0:05:20.160 --> 0:05:24.839 that smaller masses are spiraling inward toward the large mass. 0:05:24.920 --> 0:05:27.600 It's just happening on a scale that's much much, much 0:05:27.720 --> 0:05:32.599 larger than any bowling ball marble example. But that this 0:05:32.680 --> 0:05:36.320 isn't essentially what we see when we see planets orbiting 0:05:36.520 --> 0:05:40.239 a sun, or we see a moon orbiting a planet, 0:05:40.440 --> 0:05:43.719 or we see star systems orbiting a galaxy, you know, 0:05:43.839 --> 0:05:48.040 the center of a galaxy. And uh, it's all because 0:05:48.080 --> 0:05:51.280 of this curve spacetime. Now, all of that already is 0:05:51.320 --> 0:05:53.600 pretty heavy stuff. And keep in mind, there was not 0:05:53.640 --> 0:05:59.159 really any way to directly observe this. It was mostly 0:05:59.200 --> 0:06:04.320 the the uh just just Einstein using logic to work 0:06:04.360 --> 0:06:09.320 all this out and math logic and math, and ultimately 0:06:09.839 --> 0:06:12.599 it fit with what we saw of the universe. But 0:06:13.120 --> 0:06:15.440 we weren't able to test a lot of this. But 0:06:15.520 --> 0:06:19.120 then it gets even more mind blowing because now we 0:06:19.160 --> 0:06:22.760 have to get to gravitational waves. So Einstein said that 0:06:22.800 --> 0:06:26.359 if a mass were large enough and either changed shape 0:06:26.920 --> 0:06:30.040 rapidly enough, or it changed its movement in some way, 0:06:30.800 --> 0:06:34.360 uh really really quickly, it would cause ripples of space 0:06:34.360 --> 0:06:38.799 time to move outward from that event at the speed 0:06:38.839 --> 0:06:42.320 of light. And those ripples are what we call gravitational waves, 0:06:42.560 --> 0:06:45.599 which are different from gravity waves. By the way, I 0:06:45.680 --> 0:06:48.200 have been known to accidentally say gravity waves instead of 0:06:48.240 --> 0:06:50.960 gravitational waves. But the two are different things. A gravity 0:06:50.960 --> 0:06:55.760 wave is a wave that exists because of gravity. In 0:06:55.760 --> 0:06:57.880 other words, it's a physical wave of some sort of 0:06:57.880 --> 0:07:01.880 fluid system, whether it's atmosphere or or water or some 0:07:01.960 --> 0:07:05.440 other liquid. Uh. That's a gravity wave on a planet's surface. 0:07:05.600 --> 0:07:07.880 It's not the same thing as a gravitational wave, which 0:07:07.920 --> 0:07:11.320 is really a ripple of space time and like I said, 0:07:11.360 --> 0:07:13.200 it moves outward from that event at the speed of 0:07:13.280 --> 0:07:17.840 light um and stuff that could cause significant gravitational waves. 0:07:17.880 --> 0:07:20.440 Things that would be big enough for us to potentially 0:07:20.520 --> 0:07:22.680 pick up here on Earth if we had the right equipment, 0:07:23.200 --> 0:07:26.280 would include things like two black holes orbiting or colliding 0:07:26.320 --> 0:07:29.240 with one another, which in fact, that was the event 0:07:29.920 --> 0:07:34.200 that we were able to pick up with the ligo facilities, 0:07:34.240 --> 0:07:37.440 and I'll talk about those in just a bit. But 0:07:37.520 --> 0:07:40.160 there could be other stuff too, like neutron stars orbiting 0:07:40.160 --> 0:07:45.080 one another fast enough would generate gravitational waves, or a 0:07:45.080 --> 0:07:48.560 supernova explosion would create one as well. And each of 0:07:48.560 --> 0:07:51.640 these events give off a huge amount of energy, and 0:07:51.760 --> 0:07:54.920 some of the energy gets converted into making these gravitational waves. 0:07:54.920 --> 0:07:58.000 So one takeaway from this prediction something that Einstein said 0:07:58.000 --> 0:08:03.200 would happen is that an event that produces gravitational waves 0:08:03.720 --> 0:08:06.960 is an event in which energy is being lost, So 0:08:07.000 --> 0:08:10.680 you would expect to see less energy within that system 0:08:10.720 --> 0:08:14.560 afterward than before. Uh. And it would be a hundred 0:08:14.640 --> 0:08:18.680 years from the time of publication of the theory of 0:08:18.720 --> 0:08:22.560 general relativity to the time when scientists announced that they 0:08:22.560 --> 0:08:27.560 had detected a gravitational wave directly. And that's because gravitational 0:08:27.560 --> 0:08:32.120 waves are devilishly difficult to detect. And that's some alliteration 0:08:32.240 --> 0:08:36.400 for you right there. So gravitational waves are invisible. They 0:08:36.440 --> 0:08:39.959 don't emit any sort of electromagnetic radiation, so we can't 0:08:40.000 --> 0:08:44.199 see them. We can't detect them with radio detectors, nothing 0:08:44.240 --> 0:08:48.200 like that. Uh And that makes it pretty tricky to 0:08:48.200 --> 0:08:50.800 figure out where they are. But they do just pass 0:08:50.840 --> 0:08:54.000 through the universe. They don't get absorbed or scattered the 0:08:54.000 --> 0:08:57.720 way electromagnetic radiation does. If you hold up a mirror 0:08:57.960 --> 0:09:00.920 and light hits the mirror, light will bounce off the mirror. 0:09:01.040 --> 0:09:04.440 That's not the case with gravitational waves. They pass right through. Uh. 0:09:05.280 --> 0:09:10.800 So it's a very different thing than electromagnetic radiation. UM. 0:09:10.840 --> 0:09:15.160 And while they're generated from enormous events, the gravitational waves 0:09:15.240 --> 0:09:17.440 aren't very strong. By the time they get to Earth. 0:09:17.640 --> 0:09:21.720 They are pretty weak, so weak that you would need 0:09:21.760 --> 0:09:24.400 an incredibly sensitive tool in order to pick them up. 0:09:24.840 --> 0:09:26.800 And also you have to be searching at the right time, 0:09:27.280 --> 0:09:31.280 because if the event that generated the gravitational waves happened 0:09:31.360 --> 0:09:35.040 a billion years ago, but the location is four billion 0:09:35.160 --> 0:09:38.280 light years from Earth, then we would have to wait 0:09:38.320 --> 0:09:42.360 another three billion years for those gravitational waves to get 0:09:42.400 --> 0:09:44.559 to us, because again, they travel at the speed of light. 0:09:44.679 --> 0:09:47.400 That's their limit, So you have to be at the 0:09:47.520 --> 0:09:49.320 right place at the right time to pick these things 0:09:49.400 --> 0:09:52.880 up and uh, and in some cases you might argue 0:09:52.880 --> 0:09:59.040 that that's incredibly fortuitous. Although to be fair, it looks 0:09:59.080 --> 0:10:03.160 like the events that could generate gravitational waves happened pretty 0:10:03.200 --> 0:10:06.800 frequently throughout the universe. But the universe is huge, so 0:10:06.960 --> 0:10:10.320 if they're happening far away, far enough away, it will 0:10:10.360 --> 0:10:12.400 take a very long time for that information to get 0:10:12.440 --> 0:10:17.040 to us. So before the announcement on February eleven, sixteen, 0:10:17.120 --> 0:10:21.600 scientists had observed phenomena that supported the existence of gravitational waves, 0:10:21.679 --> 0:10:26.640 but we're not direct observations of a gravitational wave. Here's 0:10:26.640 --> 0:10:29.720 an example. A pair of astronomers in Puerto Rico in 0:10:29.760 --> 0:10:32.800 the nineteen seventies noticed that there was a binary pulsar 0:10:32.840 --> 0:10:37.040 system and they went back to the theory of general 0:10:37.080 --> 0:10:40.319 relativity because this was a sort of system that would 0:10:40.360 --> 0:10:43.520 be exactly the type to generate gravitational waves according to 0:10:43.600 --> 0:10:48.880 the predictions from general relativity, and because general relativity predicted, hey, 0:10:49.040 --> 0:10:51.959 if it can create gravitational waves, it's going to lose 0:10:52.080 --> 0:10:55.880 energy over time, they ended up coming up with the 0:10:55.960 --> 0:11:00.000 hypothesis that well, over time, this binary pulsar system should 0:11:00.120 --> 0:11:03.240 start to slow down because it's it's losing energy. It 0:11:03.320 --> 0:11:07.760 can't keep up at the speed it's going. So they 0:11:07.800 --> 0:11:10.800 decided to keep an eye on it. And by keeping 0:11:10.800 --> 0:11:13.240 an eye on it, I mean they continue to observe 0:11:13.360 --> 0:11:18.600 this pulstar system over the course of eight years, and 0:11:18.640 --> 0:11:20.560 by the end of the eight year period, they were 0:11:20.640 --> 0:11:24.440 comparing the findings they were observing to the predictions made 0:11:24.440 --> 0:11:27.640 by general relativity, and they were matching up. It was 0:11:27.920 --> 0:11:31.240 it was unfolding exactly the way Einstein predicted it should 0:11:31.320 --> 0:11:35.440 unfold based upon his theory of general relativity, which is 0:11:35.480 --> 0:11:38.400 incredible when you think about it, that the observations are 0:11:38.400 --> 0:11:42.320 matching up so neatly against the predictions. Uh, you know, 0:11:42.320 --> 0:11:47.360 it just shows how how keenly aware Einstein was of 0:11:47.400 --> 0:11:50.000 how our universe appears to work. Keeping in mind the 0:11:50.000 --> 0:11:55.600 general relativity. While an amazing idea collection of ideas, really 0:11:57.040 --> 0:12:01.520 it doesn't encompass everything we know, right, it doesn't. It 0:12:01.520 --> 0:12:05.439 doesn't really address quantum mechanics, for example, at least not 0:12:05.440 --> 0:12:09.360 in a way that incorporates it with classical physics. But 0:12:10.720 --> 0:12:13.360 based upon what it did cover, it seems like it 0:12:13.400 --> 0:12:19.920 was an incredibly accurate theory. Alright, so this was really 0:12:19.920 --> 0:12:24.400 considered strong but indirect support of gravitational waves because again 0:12:24.600 --> 0:12:28.600 the astronomers didn't observe gravitational waves directly. They couldn't see 0:12:28.640 --> 0:12:31.679 them or detect them, but they could see the effects, 0:12:32.520 --> 0:12:35.400 and again it was matching up with the predictions made 0:12:35.400 --> 0:12:38.959 from general relativity, So it was good indirect evidence that 0:12:39.040 --> 0:12:42.600 gravitational waves existed. Then there was an event a couple 0:12:42.600 --> 0:12:45.880 of years ago that you might have heard about, when 0:12:46.640 --> 0:12:51.680 a team of researchers working on the BICEP two telescope, 0:12:52.280 --> 0:12:56.320 which is in an Antarctica, had announced that they thought 0:12:56.600 --> 0:13:01.480 they might have discovered evidence of gravitational waves that supported 0:13:01.800 --> 0:13:06.800 a hypothesis called cosmic inflation. That's a lot of information 0:13:06.920 --> 0:13:08.800 right there, so let me explain what all that means. 0:13:10.120 --> 0:13:14.000 Cosmic inflation is a hypothesis that relates to the Big 0:13:14.000 --> 0:13:17.280 Bang theory. So with a Big Bang theory, you've got 0:13:17.320 --> 0:13:21.160 this event in which the universe undergoes a period of 0:13:21.240 --> 0:13:26.520 rapid expansion. Cosmic inflation is kind of that rapid expansion 0:13:26.679 --> 0:13:30.640 on steroids. The idea being that well, when we look 0:13:30.679 --> 0:13:34.320 at our universe and we look at the the what 0:13:34.440 --> 0:13:38.480 we can observe, it appears that our observations don't quite 0:13:38.480 --> 0:13:42.520 match up with what we would expect if we had 0:13:42.960 --> 0:13:48.720 uh just steady expansion since the Big Bang. In other words, 0:13:49.120 --> 0:13:51.360 we look at all the information we have available to us, 0:13:51.440 --> 0:13:54.720 and it looks to us that it doesn't quite match up. 0:13:54.760 --> 0:13:59.280 Something's got to be wrong. Well. One possible explanation is 0:13:59.320 --> 0:14:02.520 that surely after the Big Bang, and I'm by shortly, 0:14:02.559 --> 0:14:06.199 I mean tend to the negative thirty six power seconds 0:14:06.240 --> 0:14:09.400 after the Big Bang. So you take a ten, you 0:14:09.440 --> 0:14:11.800 put a decimal point behind the tin, then you move 0:14:11.840 --> 0:14:15.560 the decimal point to the left thirty six times, then 0:14:15.600 --> 0:14:18.200 you put seconds behind that. We're talking a fraction of 0:14:18.240 --> 0:14:21.840 a fraction of a fraction of a second. The universe 0:14:21.920 --> 0:14:27.360 underwent massive expansion, and it only lasted from from that 0:14:27.440 --> 0:14:30.320 point to about ten to the negative thirty third power 0:14:30.440 --> 0:14:36.080 or thirty second power seconds, So again an instant. It's 0:14:36.160 --> 0:14:41.600 it's completely unimaginable, at least for myself, how short an 0:14:41.600 --> 0:14:44.440 amount of time this was. But that's how how quickly 0:14:44.480 --> 0:14:50.160 the universe expanded, uh significantly, and then it slowed, but 0:14:50.280 --> 0:14:54.280 it continued to expand. Now if in fact cosmic inflation 0:14:54.600 --> 0:14:57.720 is correct, it solves a lot of the problems we 0:14:57.800 --> 0:15:01.400 have between the what we observe of today and what 0:15:01.440 --> 0:15:05.160 we believe happened with the Big Bang um and reconciles 0:15:05.280 --> 0:15:09.800 those differences. If cosmic inflation is wrong, then something else 0:15:10.040 --> 0:15:13.120 that we believe is wrong. Right. It means that what 0:15:13.160 --> 0:15:17.200 we observe either isn't representative of reality somehow we're not 0:15:17.240 --> 0:15:20.240 getting a big enough picture to understand it, or that 0:15:20.360 --> 0:15:23.800 the Big Bang theory itself is flawed in some fundamental way. 0:15:24.360 --> 0:15:27.280 We'll be back with more about HOWLEGO works in just 0:15:27.320 --> 0:15:37.520 a second, but first let's take a quick break. So 0:15:38.320 --> 0:15:40.760 the BICEP two team, what they were looking for was 0:15:41.120 --> 0:15:44.360 some evidence of gravitational waves that would have been generated 0:15:44.480 --> 0:15:48.120 during the Big Bang. This would end up supporting the 0:15:48.120 --> 0:15:51.160 cosmic inflation hypothesis, and the way they did this was 0:15:51.200 --> 0:15:55.800 they were looking at the cosmic microwave background or c MB. Now, 0:15:55.800 --> 0:16:01.120 the cosmic microwave background emerged about three thousand years after 0:16:01.240 --> 0:16:04.320 the Big Bang. This was still a period where the 0:16:04.400 --> 0:16:07.680 universe was so dense that light could not pass through it. 0:16:07.680 --> 0:16:11.360 It was dark and dense, but the cosmic microwave background 0:16:11.360 --> 0:16:18.400 formed around that time. And the hypothesis stated, well, gravitational 0:16:18.480 --> 0:16:23.520 waves would have affected the cosmic microwave background, polarizing some 0:16:23.720 --> 0:16:28.280 of those uh, some of those particles really particles, but 0:16:28.320 --> 0:16:31.920 some of the energy polarizing some of the cosmic microwave 0:16:31.960 --> 0:16:33.960 background in such a way that if you were to 0:16:35.160 --> 0:16:38.560 observe it, you could see the effect of a gravitational 0:16:38.600 --> 0:16:43.720 wave passing through the CMB. Uh. And then as the 0:16:43.760 --> 0:16:49.920 universe expand expanded rather uh, that that mark would also expand. 0:16:49.960 --> 0:16:53.680 It's kind of like imagine leaving a fingerprint on some 0:16:53.840 --> 0:16:57.520 sort of stretchy material and then stretching that material out. 0:16:58.080 --> 0:17:00.760 The fingerprint is still there. It's deformed, but still there. 0:17:01.080 --> 0:17:03.240 That's what the Bicept two team was looking for, was 0:17:03.280 --> 0:17:07.920 this pattern in the CMB that would indicate that gravitational 0:17:07.920 --> 0:17:10.919 waves from the Big Bang had passed through, and if 0:17:10.960 --> 0:17:13.199 they found that, that would be a huge support for 0:17:13.240 --> 0:17:17.320 cosmic inflation. And in the spring often they announced that 0:17:17.359 --> 0:17:22.399 they believed they had found such evidence, and they also 0:17:22.440 --> 0:17:24.920 invited other researchers to take a look at their data 0:17:25.040 --> 0:17:29.040 and see if it was verifiable or maybe they overlooked something. 0:17:30.080 --> 0:17:34.159 And in the fall often another team said we're sorry, 0:17:34.280 --> 0:17:38.639 but it looks to us like space dust might have 0:17:38.760 --> 0:17:43.080 created a false positive that what you thought it was 0:17:43.160 --> 0:17:46.320 the polarized CMB that you had been looking for was 0:17:46.400 --> 0:17:49.840 actually just space dust that's not actually part of the CMB. 0:17:50.960 --> 0:17:55.119 And uh so that ended up kind of putting the 0:17:55.200 --> 0:17:58.639 dampener on the whole celebration of finding gravitational waves to 0:17:58.640 --> 0:18:02.680 support cosmic inflation. But even if it was completely verified, 0:18:02.720 --> 0:18:06.080 even if BICEP two had irrefutable evidence that they had 0:18:06.080 --> 0:18:11.000 found the presence of gravitational waves through a uh you know, 0:18:11.359 --> 0:18:15.080 the way it affected the CNB, even then that's not 0:18:15.280 --> 0:18:19.040 direct detection. It's still indirect. You're looking at the way 0:18:19.119 --> 0:18:24.720 it's affected something else. So uh, you know, again, we're 0:18:24.720 --> 0:18:27.159 still not discovering one. And and part of that is 0:18:27.160 --> 0:18:30.080 that BICEP two is a telescope. It's looking at through 0:18:30.480 --> 0:18:34.439 the electromagnetic spectrum. And again, gravitational waves don't show up 0:18:34.480 --> 0:18:37.320 that way. So no telescope would help you find a 0:18:37.320 --> 0:18:40.800 gravitational wave directly. You might be able to find how 0:18:40.840 --> 0:18:45.360 it affected something else, but not the wave itself. Now 0:18:45.359 --> 0:18:48.560 that's not the case with the ligo observatories. Actually it's 0:18:48.600 --> 0:18:53.639 technically one observatory, but it has four different facilities, two 0:18:53.640 --> 0:18:58.160 detectors UH and to research facilities that are all part 0:18:58.160 --> 0:19:02.800 of the LIGO Observatory. LEGO itself is an acronym and 0:19:02.880 --> 0:19:09.080 it stands for Laser Interferometer Gravitational Wave Observatory. So it's 0:19:09.200 --> 0:19:11.840 a pair of giant detectors built on the surface of 0:19:11.880 --> 0:19:15.640 the Earth. One is located in Hanford, Washington, the other 0:19:15.720 --> 0:19:20.280 is in Livingstone, Louisiana. Now they're about just a little 0:19:20.359 --> 0:19:23.479 under two thousand miles apart, or just over three thousand 0:19:23.560 --> 0:19:26.880 kilometers apart from each other, and that's really important. I'll 0:19:26.880 --> 0:19:30.239 explain why in a little bit. So to understand how 0:19:30.240 --> 0:19:32.000 they work, we also have to talk about something else 0:19:32.040 --> 0:19:36.639 that gravitational waves do as they pass through space. They 0:19:36.640 --> 0:19:42.040 stretch and compress space itself. So again, if you were 0:19:42.040 --> 0:19:43.800 to if you were to take a piece of elastic, 0:19:44.920 --> 0:19:47.880 Let's say you've got a rubber band, a nice thick 0:19:47.960 --> 0:19:51.560 rubber band, and you cut it so that it's just 0:19:51.680 --> 0:19:54.720 one strip. When you pull on that rubber band, it 0:19:54.840 --> 0:19:59.320 stretches along the line where you're applying force, So it 0:19:59.440 --> 0:20:04.560 stretches in that direction, in the perpendicular direction, ninety degrees 0:20:04.680 --> 0:20:08.919 from where you're pulling it compresses, it gets more narrow, 0:20:09.720 --> 0:20:12.920 and then when you let it return to its normal shape, 0:20:13.320 --> 0:20:16.560 it gets you know, the long part ends up getting 0:20:16.560 --> 0:20:19.600 shorter and the narrow part ends of getting wider as 0:20:19.600 --> 0:20:24.439 a result, gravitational waves do this to reality. They do 0:20:24.600 --> 0:20:28.280 this to actual space. They stretch and compress, and it 0:20:28.359 --> 0:20:32.560 happens several times as the wave oscillates through. Really I 0:20:32.560 --> 0:20:36.479 should just say as the wave passes through rather than oscillates. Uh, 0:20:36.600 --> 0:20:41.240 the distortion oscillates, but the wave passes through. So that 0:20:41.280 --> 0:20:45.920 means the actual distance changes between two points as the 0:20:46.080 --> 0:20:48.840 gravitational wave passes through that area. So if we were 0:20:48.880 --> 0:20:53.639 to magnify this effect, and I mean magnify it to 0:20:53.760 --> 0:20:56.800 a ludicrous degree, you would be able to see it. 0:20:57.040 --> 0:20:59.640 You would actually be able to witness this. You could 0:20:59.680 --> 0:21:02.679 stand ten feet away from someone else and when the 0:21:02.680 --> 0:21:06.440 gravitational wave passes through, it would make it look like 0:21:06.520 --> 0:21:08.920 the two of you suddenly got further away and then 0:21:08.960 --> 0:21:11.080 closer to each other, and then further away and closer 0:21:11.080 --> 0:21:14.040 to each other, even though you haven't moved anywhere, because 0:21:14.440 --> 0:21:21.000 the distance itself is stretching and compressing. So why don't 0:21:21.080 --> 0:21:23.639 we see that? I mean, if the celestial events that 0:21:23.680 --> 0:21:26.080 produce gravitational waves happen on the order of something like 0:21:26.119 --> 0:21:29.720 every fifteen minutes. Why are we all noticing this whibbly 0:21:29.800 --> 0:21:35.639 wobbly effect. Well, it's because the actual distortion that happens 0:21:35.720 --> 0:21:40.640 here on Earth is much much much smaller in magnitude, 0:21:41.480 --> 0:21:44.919 so much more, so much smaller that it's difficult to 0:21:44.920 --> 0:21:48.680 even explain. But if you were to have a supernova 0:21:48.800 --> 0:21:53.560 explode in the Milky Way galaxy, in our galaxy, the 0:21:53.600 --> 0:21:58.560 gravitational waves generated by that explosion would maybe be powerful 0:21:58.680 --> 0:22:01.520 enough to distort the distance between the Earth and the 0:22:01.560 --> 0:22:06.400 Sun by about the diameter of a hydrogen atom, so 0:22:07.040 --> 0:22:12.280 not noticeable to any degree, not at least to human senses. 0:22:12.840 --> 0:22:14.600 So if you were to even go on a smaller scale, 0:22:14.680 --> 0:22:17.480 let's say that you you pick two points that are 0:22:17.480 --> 0:22:20.080 a kilometer apart here on the surface of the Earth, 0:22:21.200 --> 0:22:24.240 the amount of distortion would be equivalent to a few 0:22:24.359 --> 0:22:28.639 thousands of the diameter of a proton. So you're talking 0:22:28.640 --> 0:22:31.840 about a sub atomic particle, and just a tiny, tiny, 0:22:31.880 --> 0:22:35.960 tiny fraction of that sub atomic particles diameter would be 0:22:36.000 --> 0:22:39.440 the amount of distortion that would happen across a kilometer 0:22:39.600 --> 0:22:43.560 worth of distance here on Earth. Again, that means it's 0:22:43.600 --> 0:22:48.040 so small that it's incredibly difficult to detect, so much 0:22:48.080 --> 0:22:52.000 so that Einstein himself I was pretty sure we would 0:22:52.000 --> 0:22:55.560 never be able to directly detect gravitational waves because he 0:22:55.560 --> 0:22:58.280 could not imagine a system that would be sensitive enough 0:22:58.400 --> 0:23:03.480 to pick up such a minute change, a distortion that's 0:23:03.520 --> 0:23:06.159 happening so quickly because it's a fraction of a second, 0:23:06.800 --> 0:23:12.359 and it's so small as to be unnoticeable. So the 0:23:12.400 --> 0:23:15.439 other problem here is not just that it's such a 0:23:15.560 --> 0:23:17.840 very tiny effect that lasts a short amount of time. 0:23:17.840 --> 0:23:20.520 It's also that a lot of other stuff could create 0:23:20.560 --> 0:23:26.280 false positives. You can have incredibly sensitive instrumentation, but if 0:23:26.720 --> 0:23:31.040 that instrument is really really sensitive, any sort of interference 0:23:31.080 --> 0:23:35.840 could set off and you could end up getting false readings. 0:23:35.880 --> 0:23:40.600 So a change in air pressure or temperature, or seismic activity, 0:23:40.920 --> 0:23:46.360 even a heavy truck driving nearby could set off false results. 0:23:46.920 --> 0:23:48.600 So you have to come up with a really clever 0:23:48.680 --> 0:23:53.160 way to measure distortion, to limit vibration, and to eliminate 0:23:53.200 --> 0:23:55.720 the chance that it was a false positive. And Lego 0:23:56.160 --> 0:23:59.040 is the answer to all of that. So the Lego 0:23:59.119 --> 0:24:03.040 Observatory is actually the result of decades of collaborative work 0:24:03.119 --> 0:24:08.080 among different scientific research centers and international bodies and universities, 0:24:08.960 --> 0:24:12.000 and all started back in nineteen seventy nine. That's when 0:24:12.040 --> 0:24:15.320 the National Science Foundation approved funds for cal Tech and 0:24:15.480 --> 0:24:18.639 m i T to develop laser interferometer research and development. 0:24:19.640 --> 0:24:22.160 And a few years later, in nineteen eighty three, Caltech 0:24:22.240 --> 0:24:24.560 and m i T submitted a proposal for a kilometer 0:24:24.720 --> 0:24:29.240 scale detector. Uh but keep in mind, all right, so 0:24:29.440 --> 0:24:31.879 nineteen seventy nine you get the funding for R and 0:24:32.000 --> 0:24:36.200 D three, there's the submission of a proposal for a 0:24:36.320 --> 0:24:41.640 kilometer scale detector. There wouldn't be approval for a detector 0:24:41.800 --> 0:24:48.680 until nineteen nine, so almost a decade later, and which 0:24:48.920 --> 0:24:52.160 turns out was probably okay, because we really didn't have 0:24:52.320 --> 0:24:57.720 the technological ability to detect things on a scale small 0:24:57.840 --> 0:25:01.880 enough to register a gravitational wave the first place. But 0:25:01.880 --> 0:25:04.840 but still, you know, a decade's delay before you even 0:25:04.880 --> 0:25:08.640 get approval is still pretty rough. Construction didn't begin until 0:25:10.880 --> 0:25:14.640 the inauguration of the Ligo Observatory took place in nineteen 0:25:16.359 --> 0:25:19.960 but even then that didn't mean that the the observatory 0:25:20.040 --> 0:25:23.040 was online collecting data. It didn't do that until two 0:25:23.040 --> 0:25:28.960 thousand two, and here's the kicker. Eventually scientists came to 0:25:28.960 --> 0:25:33.520 the conclusion that this Ligo observatory was not sensitive enough 0:25:33.560 --> 0:25:36.480 to detect gravitational waves. That despite the fact that it 0:25:36.600 --> 0:25:41.919 was this large UH detector or pair of large detectors, 0:25:41.920 --> 0:25:45.800 actually because again one in Louisiana one in Washington, it 0:25:45.880 --> 0:25:50.520