WEBVTT - TechStuff Classic: How LIGO Works 0:00:04.360 --> 0:00:12.560 Welcome to Tech Stuff, a production from iHeartRadio. Hey there, 0:00:12.680 --> 0:00:16.760 and welcome to tech Stuff. I'm your host Jonathan Strickland. 0:00:16.880 --> 0:00:21.160 I'm an executive producer with iHeartRadio and how the tech 0:00:21.320 --> 0:00:25.599 are here. It is time for a classic episode. This 0:00:25.680 --> 0:00:29.680 one is called How Lego Works. Originally published on February 0:00:29.760 --> 0:00:33.440 twenty fourth, twenty sixteen. This was really cool because this 0:00:33.520 --> 0:00:38.479 came out shortly after we were learning about how Lego 0:00:38.920 --> 0:00:42.639 had detected gravitational waves, which up to that point had 0:00:42.720 --> 0:00:47.239 largely been a hypothetical concept. So this was one of 0:00:47.240 --> 0:00:50.279 those things where we finally figured out a way to 0:00:50.560 --> 0:00:55.760 detect something that had been hypothesized about but previously undetected, 0:00:56.080 --> 0:01:02.600 So really cool use of technology. Then the Ligo Observatory 0:01:02.800 --> 0:01:06.720 had picked up a gravitational wave, and this was huge 0:01:06.880 --> 0:01:10.880 news around the world. And in case you were wondering, 0:01:10.959 --> 0:01:13.600 what the heck is this news all about? How did 0:01:13.600 --> 0:01:17.080 they pick up that gravitational wave? What exactly is the 0:01:17.120 --> 0:01:22.320 technology powering our sensors to detect this stuff? How does 0:01:22.319 --> 0:01:25.160 it all work? That's what this episode's all about. So 0:01:25.480 --> 0:01:27.800 this was the very first time anyone had been able 0:01:27.840 --> 0:01:32.039 to measure a gravitational wave directly So today we're going 0:01:32.120 --> 0:01:36.080 to talk all about what that means and how it happened. Now, 0:01:36.120 --> 0:01:39.800 to begin with, we need to lay some groundwork and 0:01:40.000 --> 0:01:43.360 to really get an understanding of what gravitational waves are. 0:01:44.000 --> 0:01:48.639 So gravitational waves ultimately were one of the predictions made 0:01:48.760 --> 0:01:54.040 by a certain Albert Einstein with this theory of general relativity. 0:01:54.160 --> 0:01:58.160 So in that theory, Einstein presented this idea that our 0:01:58.240 --> 0:02:02.720 universe is filled with spacetime. If you're a fan of 0:02:02.720 --> 0:02:07.240 science fiction, you have undoubtedly come across that term star 0:02:07.320 --> 0:02:10.079 trek is all about the spacetime continuum, and that you've 0:02:10.080 --> 0:02:12.000 got to be careful. You could rip a hole in 0:02:12.040 --> 0:02:15.399 the fabric of spacetime. As far as we know, that's 0:02:15.440 --> 0:02:19.480 not really that possible. I mean, black holes could sort 0:02:19.520 --> 0:02:22.640 of be that maybe, But at any rate, spacetime itself 0:02:22.720 --> 0:02:27.520 is this calling it stuff is probably the wrong way 0:02:27.520 --> 0:02:29.920 of putting it, but it is like a fabric and 0:02:30.240 --> 0:02:34.480 mass hangs inside this fabric, And by mass, i'm talking 0:02:34.480 --> 0:02:38.320 about stuff like stars or even an entire solar systems 0:02:38.440 --> 0:02:43.760 or galaxies that hang in this fabric, and just like 0:02:44.040 --> 0:02:48.440 you would see in a two dimensional display, it ends 0:02:48.520 --> 0:02:53.320 up curving the fabric around the mass. We often talk 0:02:53.480 --> 0:02:58.000 about this in terms of a very simple example that's 0:02:58.000 --> 0:03:01.760 easy to imagine. You get some sort of stretching material. 0:03:01.840 --> 0:03:04.559 Often you'll just hear someone say, okay, get a trampoline. 0:03:04.639 --> 0:03:08.079 You've got a trampoline, and you put a big, heavy 0:03:08.160 --> 0:03:11.639 bowling ball on the trampoline. So that bowling ball is 0:03:11.680 --> 0:03:15.320 going to deform the trampoline surface. It's no longer going 0:03:15.360 --> 0:03:18.560 to be straight. It's going to end up curving around 0:03:18.600 --> 0:03:20.840 the bowling ball to some extent, creating kind of a 0:03:21.000 --> 0:03:25.560 dmple where the bowling ball has has created this impression 0:03:25.600 --> 0:03:27.760 inside the trampoline, and as long as the bowling ball 0:03:27.840 --> 0:03:31.280 is there, that impression is going to stay. This is 0:03:31.320 --> 0:03:34.880 sort of the like the way spacetime curves around giant 0:03:34.920 --> 0:03:40.400 masses like stars and black holes things like that. Of course, 0:03:40.800 --> 0:03:43.880 we have to remember that spacetime is actually four dimensional, 0:03:44.000 --> 0:03:46.640 not a two dimensional thing like a trampoline. I mean, 0:03:46.680 --> 0:03:49.800 I know that trampolines technically have three dimensions, but we're 0:03:49.840 --> 0:03:51.840 really looking at a surface, so it's more like a 0:03:51.920 --> 0:03:56.320 two dimensional plane. In reality. In spacetime it's four dimensional 0:03:56.320 --> 0:04:00.400 because you've got the three spatial dimensions plus time, and 0:04:00.480 --> 0:04:02.600 that is a little difficult to get your head around. 0:04:03.400 --> 0:04:05.680 But that's why we tend to look at this two 0:04:05.680 --> 0:04:08.360 dimensional example. It's a lot easier for us to imagine. 0:04:08.880 --> 0:04:12.240 So let's go a little further with that analogy to 0:04:12.320 --> 0:04:15.320 kind of talk about gravity. See Einstein proposed that gravity 0:04:15.440 --> 0:04:19.120 was a manifestation of this curved space time. And if 0:04:19.120 --> 0:04:21.599 we take that trampoline example, Let's say that you have 0:04:21.680 --> 0:04:23.800 a regular trampoline. You haven't put the bowling ball on 0:04:23.839 --> 0:04:26.359 there yet, so it's a nice flat surface, and you 0:04:26.400 --> 0:04:28.839 have a marble, and you roll the marble across the 0:04:28.839 --> 0:04:31.279 surface of the trampoline. So if there's nothing else there, 0:04:31.279 --> 0:04:33.880 and if the trampoline is level, if the surface is level, 0:04:34.800 --> 0:04:37.280 the marble should just roll in the straight line from 0:04:37.320 --> 0:04:40.359 one side of the trampoline to the other, no problem. 0:04:40.560 --> 0:04:42.599 Now let's say you put that big, heavy bowling ball 0:04:42.600 --> 0:04:45.200 on the trampoline. It creates that dimple, and then you 0:04:45.240 --> 0:04:48.680 try and roll the marble across the trampoline surface. Well, 0:04:48.720 --> 0:04:51.800 now that dimple is going to end up affecting the 0:04:51.800 --> 0:04:54.400 pathway of the marble. It's going to start to spiral 0:04:54.520 --> 0:04:58.920 inward toward the bowling ball. Ultimately it'll end up making 0:04:58.960 --> 0:05:02.680 contact with the bowling ball, and Einstein said, that's essentially 0:05:02.680 --> 0:05:07.120 what gravity is. It's that you've got these large masses 0:05:07.640 --> 0:05:12.000 that curves spacetime to the extent that smaller masses are 0:05:12.120 --> 0:05:15.520 spiraling inward toward the large mass. It's just happening on 0:05:15.560 --> 0:05:18.960 a scale that's much much, much larger than any bowling ball, 0:05:19.040 --> 0:05:23.919 marble example. But that this isn't essentially what we see 0:05:23.960 --> 0:05:28.400 when we see planets orbiting a sun, or we see 0:05:28.560 --> 0:05:31.719 a moon orbiting a planet, or we see star systems 0:05:31.800 --> 0:05:34.720 orbiting a galaxy, you know, the center of a galaxy, 0:05:35.480 --> 0:05:40.159 and it's all because of this curve spacetime. Now, all 0:05:40.160 --> 0:05:42.880 of that already is pretty heavy stuff. And keep in mind, 0:05:42.920 --> 0:05:47.120 there was not really any way to directly observe this. 0:05:47.320 --> 0:05:53.000 It was mostly the the just Einstein using logic to 0:05:53.760 --> 0:05:57.239 work all this out and math, logic and math, and 0:05:58.480 --> 0:06:02.200 ultimately it fit with what we saw of the universe. 0:06:02.240 --> 0:06:04.520 But we weren't able to test a lot of this. 0:06:05.080 --> 0:06:08.800 But then it gets even more mind blowing because now 0:06:08.800 --> 0:06:12.400 we have to get to gravitational waves. So Einstein said 0:06:12.400 --> 0:06:15.400 that if a mass were large enough and either changed 0:06:15.680 --> 0:06:19.760 shape rapidly enough or it changed its movement in some way, 0:06:21.120 --> 0:06:24.320 really really quickly. It would cause ripples of space time 0:06:24.360 --> 0:06:28.920 to move outward from that event at the speed of light. 0:06:29.440 --> 0:06:32.479 And those ripples are what we call gravitational waves, which 0:06:32.480 --> 0:06:35.479 are different from gravity waves. By the way, I have 0:06:35.520 --> 0:06:38.920 been known to accidentally say gravity waves instead of gravitational waves, 0:06:38.920 --> 0:06:41.719 but the two are different things. A gravity wave is 0:06:41.720 --> 0:06:45.840 a wave that exists because of gravity. In other words, 0:06:45.880 --> 0:06:48.360 it's a physical wave of some sort of fluid system, 0:06:48.400 --> 0:06:53.200 whether it's atmosphere or water or some other liquid. That's 0:06:53.240 --> 0:06:55.960 a gravity wave on a planet's surface. It's not the 0:06:56.000 --> 0:06:58.159 same thing as a gravitational wave, which is really a 0:06:58.240 --> 0:07:01.400 ripple of space time, and like I said, it moves 0:07:01.440 --> 0:07:04.280 outward from that event at the speed of light. And 0:07:04.360 --> 0:07:08.160 stuff that could cause significant gravitational waves, things that would 0:07:08.160 --> 0:07:10.800 be big enough for us to potentially pick up here 0:07:10.880 --> 0:07:13.520 on Earth if we had the right equipment, would include 0:07:13.520 --> 0:07:16.680 things like two black holes orbiting or colliding with one another, 0:07:16.840 --> 0:07:20.160 which in fact, that was the event that we were 0:07:20.200 --> 0:07:24.280 able to pick up with the Ligo facilities. And I'll 0:07:24.320 --> 0:07:27.600 talk about those in just a bit. But there could 0:07:27.640 --> 0:07:30.320 be other stuff too, like neutron stars orbiting one another 0:07:30.440 --> 0:07:35.960 fast enough would generate gravitational waves, or a supernova explosion 0:07:36.240 --> 0:07:38.840 would create one as well. And each of these events 0:07:38.880 --> 0:07:41.760 give off a huge amount of energy, and some of 0:07:41.800 --> 0:07:44.760 that energy gets converted into making these gravitational waves. So 0:07:44.840 --> 0:07:48.239 one takeaway from this prediction something that Einstein said would happen, 0:07:49.240 --> 0:07:53.720 is that any event that produces gravitational waves is an 0:07:53.720 --> 0:07:57.040 event in which energy is being lost, So you would 0:07:57.040 --> 0:08:02.160 expect to see less energy within that system afterward than before. 0:08:03.160 --> 0:08:06.400 And it would be a hundred years from the time 0:08:06.440 --> 0:08:10.560 of publication of the theory of general relativity to the 0:08:10.600 --> 0:08:13.760 time when scientists announced that they had detected a gravitational 0:08:13.840 --> 0:08:19.520 wave directly. And that's because gravitational waves are devilishly difficult 0:08:19.560 --> 0:08:22.760 to detect. And that's some alliteration for you right there. 0:08:23.520 --> 0:08:27.080 So gravitational waves are invisible. They don't emit any sort 0:08:27.120 --> 0:08:31.160 of electromagnetic radiation, so we can't see them. We can't 0:08:31.200 --> 0:08:36.480 detect them with radio detectors, nothing like that, and that 0:08:36.520 --> 0:08:39.000 makes it pretty tricky to figure out where they are. 0:08:39.559 --> 0:08:41.760 But they do just pass through the universe. They don't 0:08:41.920 --> 0:08:46.520 get absorbed or scattered the way electromagnetic radiation does. If 0:08:46.520 --> 0:08:48.920 you hold up a mirror and light hits the mirror, 0:08:49.040 --> 0:08:51.600 light will bounce off the mirror. That's not the case 0:08:51.679 --> 0:08:56.079 with gravitational waves. They pass right through, so it's a 0:08:56.160 --> 0:09:02.720 very different thing than electromagnetic radiation. And while they're generated 0:09:02.800 --> 0:09:06.160 from enormous events, the gravitational waves aren't very strong. By 0:09:06.160 --> 0:09:09.760 the time they get to Earth. They are pretty weak, 0:09:10.160 --> 0:09:13.000 so weak that you would need an incredibly sensitive tool 0:09:13.080 --> 0:09:15.240 in order to pick them up. And also you have 0:09:15.280 --> 0:09:17.880 to be searching at the right time, because if the 0:09:17.960 --> 0:09:22.200 event that generated the gravitational waves happened a billion years ago, 0:09:22.920 --> 0:09:25.920 but the location is four billion light years from Earth, 0:09:26.880 --> 0:09:29.520 then we would have to wait another three billion years 0:09:29.960 --> 0:09:33.000 for those gravitational waves to get to us, because again, 0:09:33.040 --> 0:09:35.160 they travel at the speed of light. That's their limit. 0:09:36.000 --> 0:09:37.680 So you have to be at the right place at 0:09:37.720 --> 0:09:41.280 the right time to pick these things up, and in 0:09:41.320 --> 0:09:45.959 some cases you might argue that that's incredibly fortuitous. Although 0:09:46.679 --> 0:09:50.760 to be fair, it looks like the events that could 0:09:50.840 --> 0:09:54.679 generate gravitational waves happen pretty frequently throughout the universe. But 0:09:54.760 --> 0:09:58.240 the universe is huge, so if they're happening far away, 0:09:58.679 --> 0:10:01.200 far enough away, will take a very long time for 0:10:01.240 --> 0:10:04.920 that information to get to us. So before the announcement 0:10:04.960 --> 0:10:08.600 on February eleventh, twenty sixteen, scientists had observed phenomena that 0:10:08.800 --> 0:10:13.080 supported the existence of gravitational waves, but were not direct 0:10:13.280 --> 0:10:17.199 observations of a gravitational wave. Here's an example. A pair 0:10:17.240 --> 0:10:20.880 of astronomers in Puerto Rico in the nineteen seventies noticed 0:10:20.920 --> 0:10:25.360 that there was a binary pulsar system and they went 0:10:25.400 --> 0:10:28.439 back to the theory of general relativity because this was 0:10:28.480 --> 0:10:31.200 a sort of system that would be exactly the type 0:10:31.240 --> 0:10:35.360 to generate gravitational waves according to the predictions from general relativity, 0:10:36.080 --> 0:10:39.800 and because general relativity predicted, hey, if it can create 0:10:39.840 --> 0:10:44.160 gravitational waves, it's going to lose energy over time, they 0:10:44.640 --> 0:10:47.559 ended up coming up with the hypothesis that, well, over time, 0:10:47.640 --> 0:10:51.360 this binary pulsar system should start to slow down because 0:10:51.360 --> 0:10:54.600 it's losing energy. It can't keep up at the speed 0:10:54.640 --> 0:10:59.120 it's going. So they decided to keep an eye on it. 0:10:59.400 --> 0:11:01.760 And by keeping an eye on it, I mean they 0:11:01.840 --> 0:11:06.360 continue to observe this pulsar system over the course of 0:11:06.400 --> 0:11:09.760 eight years, and by the end of the eight year period, 0:11:09.760 --> 0:11:13.280 they were comparing the findings they were observing to the 0:11:13.320 --> 0:11:16.319 predictions made by general relativity, and they were matching up. 0:11:17.040 --> 0:11:20.960 It was unfolding exactly the way Einstein predicted it should 0:11:21.040 --> 0:11:25.160 unfold based upon his theory of general relativity, which is 0:11:25.200 --> 0:11:28.080 incredible when you think about it, that the observations are 0:11:28.120 --> 0:11:32.160 matching up so neatly against the predictions. You know, it 0:11:32.200 --> 0:11:37.360 just shows how how keenly aware Einstein was of how 0:11:37.400 --> 0:11:40.720 our universe appears to work. Keeping in mind that general relativity, 0:11:41.160 --> 0:11:47.520 while an amazing idea collection of ideas, really it doesn't 0:11:47.960 --> 0:11:52.160 encompass everything that we know, right. It doesn't really address 0:11:52.240 --> 0:11:55.600 quantum mechanics, for example, at least not in a way 0:11:55.600 --> 0:12:01.200 that incorporates it with classical physics. But based upon what 0:12:01.280 --> 0:12:04.160 it did cover, it seems like it was an incredibly 0:12:04.280 --> 0:12:10.520 accurate theory, all right. So this was really considered strong 0:12:10.640 --> 0:12:15.199 but indirect support of gravitational waves, because again the astronomers 0:12:15.200 --> 0:12:18.680 didn't observe gravitational waves directly. They couldn't see them or 0:12:18.720 --> 0:12:23.240 detect them, but they could see the effects, and again 0:12:23.280 --> 0:12:26.320 it was matching up with the predictions made from general relativity. 0:12:26.400 --> 0:12:30.160 So it was good indirect evidence that gravitational waves existed. 0:12:31.160 --> 0:12:32.880 Then there was an event a couple of years ago 0:12:33.600 --> 0:12:37.520 that you might have heard about when a team of 0:12:38.000 --> 0:12:42.600 researchers working on the BICEP two telescope, which is an 0:12:43.080 --> 0:12:47.920 Antarctica had announced that they thought they might have discovered 0:12:48.000 --> 0:12:54.120 evidence of gravitational waves that supported a hypothesis called cosmic inflation. 0:12:55.400 --> 0:12:57.360 That's a lot of information right there, So let me 0:12:57.400 --> 0:13:02.439 explain what all that means. Cosmic inflation is a hypothesis 0:13:02.480 --> 0:13:05.840 that relates to the Big Bang theory. So, with the 0:13:05.840 --> 0:13:08.880 Big Bang theory, you've got this event in which the 0:13:09.000 --> 0:13:13.920 universe undergoes a period of rapid expansion. Cosmic inflation is 0:13:14.440 --> 0:13:19.720 kind of that rapid expansion on steroids. The idea being that, well, 0:13:19.880 --> 0:13:22.400 when we look at our universe and we look at 0:13:23.920 --> 0:13:27.880 what we can observe, it appears that our observations don't 0:13:27.920 --> 0:13:31.560 quite match up with what we would expect if we 0:13:31.920 --> 0:13:38.440 had just steady expansion since the Big Bang. In other words, 0:13:38.800 --> 0:13:41.079 we look at all the information we have available to us, 0:13:41.160 --> 0:13:44.440 and it looks to us that it doesn't quite match up. 0:13:44.480 --> 0:13:49.000 Something's got to be wrong. Well, one possible explanation is 0:13:49.040 --> 0:13:52.360 that shortly after the Big Bang, and by shortly, I 0:13:52.400 --> 0:13:56.280 mean tend to the negative thirty sixth power seconds after 0:13:56.360 --> 0:13:59.320 the Big Bang, So you take a ten, you put 0:13:59.320 --> 0:14:01.640 a decimal point behind the ten, then you move the 0:14:01.640 --> 0:14:05.360 decimal point to the left thirty six times that you 0:14:05.440 --> 0:14:08.040 put seconds behind that. We're talking a fraction of a 0:14:08.080 --> 0:14:12.040 fraction of a fraction of a second. The universe underwent 0:14:12.640 --> 0:14:17.559 massive expansion, and it only lasted from that point to 0:14:17.679 --> 0:14:20.640 about ten to the negative thirty third power or thirty 0:14:20.680 --> 0:14:28.280 second power seconds. So again an instant. It's completely unimaginable, 0:14:28.520 --> 0:14:31.960 at least for myself, how short an amount of time 0:14:32.000 --> 0:14:37.280 this was. But that's how quickly the universe expanded significantly, 0:14:37.880 --> 0:14:42.200 and then it slowed, but it continued to expand. Now, 0:14:42.360 --> 0:14:46.560 if in fact, cosmic inflation is correct, it solves a 0:14:46.560 --> 0:14:49.360 lot of the problems we have between the what we 0:14:49.440 --> 0:14:52.880 observe today and what we believe happened with the Big Bang, 0:14:53.880 --> 0:14:58.720 and reconciles those differences. If cosmic inflation is wrong, then 0:14:58.800 --> 0:15:02.280 something else that we believe is wrong. Right. It means 0:15:02.320 --> 0:15:06.600 that what we observe either isn't representative of reality somehow 0:15:06.640 --> 0:15:08.920 we're not getting a big enough picture to understand it, 0:15:09.680 --> 0:15:12.400 or that the Big Bang theory itself is flawed in 0:15:12.440 --> 0:15:16.920 some fundamental way. Hey, we'll be back with this heavy 0:15:16.960 --> 0:15:21.120 subject of detecting gravitational waves with LEGO after this short break, 0:15:30.960 --> 0:15:33.800 so the BIS of two team what they were looking 0:15:33.800 --> 0:15:37.360 for was some evidence of gravitational waves that would have 0:15:37.400 --> 0:15:41.200 been generated during the Big Bang. This would end up 0:15:41.240 --> 0:15:44.520 supporting the cosmic inflation hypothesis. And the way they did 0:15:44.600 --> 0:15:47.480 this was they were looking at the cosmic microwave background 0:15:47.640 --> 0:15:52.320 or CMBAM. Now, the cosmic microwave background emerged about three 0:15:52.400 --> 0:15:57.040 hundred eighty thousand years after the Big Bang. This was 0:15:57.080 --> 0:15:59.720 still a period where the universe was so dense that 0:16:00.000 --> 0:16:02.800 I could not pass through it. It was dark and dense, 0:16:03.440 --> 0:16:07.800 but the cosmic microwave background formed around that time, and 0:16:07.880 --> 0:16:14.040 the hypothesis stated, well, gravitational waves would have affected the 0:16:14.160 --> 0:16:19.160 cosmic microwave background, polarizing some of those some of those 0:16:20.000 --> 0:16:24.080 particles really not particles, but some of that energy polarizing 0:16:24.120 --> 0:16:26.760 some of the cosmic microwave background in such a way 0:16:26.800 --> 0:16:30.240 that if you were to observe it, you could see 0:16:30.280 --> 0:16:34.960 the effect of a gravitational wave passing through the cmb 0:16:36.800 --> 0:16:42.400 And then as the universe expand expanded, rather that mark 0:16:42.600 --> 0:16:45.760 would also expand. It's kind of like imagine leaving a 0:16:45.800 --> 0:16:50.200 fingerprint on some sort of stretchy material and then stretching 0:16:50.240 --> 0:16:53.680 that material out, the fingerprint is still there. It's deformed, 0:16:53.720 --> 0:16:56.200 but still there. That's what the BICEP two team was 0:16:56.240 --> 0:16:59.880 looking for, was this pattern in the CMB that would 0:17:00.040 --> 0:17:03.680 indicate that gravitational waves from the Big Bang had passed through, 0:17:04.320 --> 0:17:06.400 and if they found that, that would be a huge 0:17:06.400 --> 0:17:10.359 support for cosmic inflation. And in the spring of twenty fourteen, 0:17:10.359 --> 0:17:13.800 they announced that they believed they had found such evidence, 0:17:14.800 --> 0:17:18.040 and they also invited other researchers to take a look 0:17:18.040 --> 0:17:21.320 at their data and see if it was verifiable or 0:17:21.480 --> 0:17:25.680 maybe they overlooked something. And in the fall of twenty fourteen, 0:17:25.840 --> 0:17:29.040 another team said, we're sorry, but it looks to us 0:17:29.960 --> 0:17:34.159 like space dust might have created a false positive that 0:17:35.080 --> 0:17:38.479 what you thought it was the polarized CMB that you 0:17:38.520 --> 0:17:41.920 had been looking for was actually just space dust that's 0:17:41.960 --> 0:17:47.160 not actually part of the CMB. And so that ended 0:17:47.200 --> 0:17:50.840 up kind of putting a dampener on the whole celebration 0:17:50.920 --> 0:17:54.480 of finding gravitational waves to support cosmic inflation. But even 0:17:54.480 --> 0:17:57.840 if it was completely verified, even if BICEP two had 0:17:58.200 --> 0:18:01.399 irrefutable evidence that they had found the presence of gravitational 0:18:01.400 --> 0:18:07.040 waves through a you know, the way it affected the CMB. 0:18:07.800 --> 0:18:11.560 Even then that's not direct detection. It's still indirect. You're 0:18:11.560 --> 0:18:17.520 looking at the way it's affected something else. So you know, 0:18:17.760 --> 0:18:20.720 again we're still not discovering one. And part of that 0:18:20.800 --> 0:18:23.520 is that BICEP two is a telescope. It's looking at 0:18:23.520 --> 0:18:27.920 through the electromagnetic spectrum, and again, gravitational waves don't show 0:18:28.000 --> 0:18:30.840 up that way. So no telescope would help you find 0:18:30.920 --> 0:18:33.879 a gravitational wave directly. You might be able to find 0:18:34.320 --> 0:18:37.720 how it affected something else, but not the wave itself. 0:18:38.840 --> 0:18:42.040 Now that's not the case with the LIGO observatories. Actually 0:18:42.080 --> 0:18:46.640 it's technically one observatory, but it has four different facilities, 0:18:47.000 --> 0:18:51.800 two detectors and two research facilities that are all part 0:18:51.840 --> 0:18:56.439 of the LIGO observatory. LIGO itself is an acronym and 0:18:56.560 --> 0:19:02.760 it stands for Laser Interferometer Gravitational Wave Observatory. So it's 0:19:02.840 --> 0:19:05.560 a pair of giant detectors built on the surface of 0:19:05.560 --> 0:19:09.320 the Earth. One is located in Hanford, Washington, the other 0:19:09.400 --> 0:19:14.000 is in Livingstone, Louisiana. Now they're about just a little 0:19:14.080 --> 0:19:17.159 under two thousand miles apart, or just over three thousand 0:19:17.240 --> 0:19:20.600 kilometers apart from each other, and that's really important. I'll 0:19:20.600 --> 0:19:23.919 explain why in a little bit. So to understand how 0:19:23.960 --> 0:19:25.680 they work, we also have to talk about something else 0:19:25.720 --> 0:19:30.280 that gravitational waves do as they pass through space. They 0:19:30.359 --> 0:19:35.719 stretch and compress space itself. So again, if you were 0:19:35.920 --> 0:19:38.960 if you were to take a piece of elastic, I'd say, 0:19:38.960 --> 0:19:42.240 you've got a rubber band, a nice thick rubber band, 0:19:43.200 --> 0:19:45.959 and you cut it so that it's just one strip. 0:19:46.800 --> 0:19:49.720 When you pull on that rubber band, it stretches along 0:19:49.960 --> 0:19:53.720 the line where you're applying force, So it stretches in 0:19:53.800 --> 0:19:58.920 that direction, in the perpendicular direction ninety degrees from where 0:19:58.920 --> 0:20:04.040 you're pulling. It compresses, it gets more narrow, and then 0:20:04.080 --> 0:20:07.200 when you let it return to its normal shape, it 0:20:07.320 --> 0:20:10.560 gets you know, the long part ends up getting shorter 0:20:10.720 --> 0:20:13.920 and the narrow part ends up getting wider as a result, 0:20:15.200 --> 0:20:18.560 gravitational waves do this to reality. They do this to 0:20:18.640 --> 0:20:22.760 actual space. They stretch and compress, and it happens several 0:20:22.800 --> 0:20:26.639 times as the wave oscillates through. Really I should just 0:20:26.680 --> 0:20:30.680 say as the wave passes through, rather than oscillates. The 0:20:30.760 --> 0:20:35.200 distortion oscillates, but the wave passes through, so That means 0:20:35.200 --> 0:20:40.359 the actual distance changes between two points as that gravitational 0:20:40.359 --> 0:20:42.679 wave passes through that area. So if we were to 0:20:42.720 --> 0:20:47.520 magnify this effect, and I mean magnify it to a 0:20:47.680 --> 0:20:50.760 ludicrous degree, you would be able to see it. You 0:20:50.760 --> 0:20:53.719 would actually be able to witness this. You could stand 0:20:53.800 --> 0:20:57.040 ten feet away from someone else and when the gravitational 0:20:57.040 --> 0:21:00.280 wave passes through, it would make it look like the 0:21:00.320 --> 0:21:03.040 two of you suddenly got further away and then closer 0:21:03.040 --> 0:21:04.879 to each other, and then further away and closer to 0:21:04.880 --> 0:21:08.280 each other, even though you haven't moved anywhere, because the 0:21:08.320 --> 0:21:14.840 distance itself is stretching and compressing. So why don't we 0:21:14.960 --> 0:21:17.679 see that? I mean, if these celestial events that produce 0:21:17.720 --> 0:21:20.080 gravitational waves happen on the order of something like every 0:21:20.119 --> 0:21:25.520 fifteen minutes, why are we all noticing this whibbly wobbly effect. Well, 0:21:26.200 --> 0:21:30.160 it's because the actual distortion that happens here on Earth 0:21:31.080 --> 0:21:35.920 is much much much smaller in magnitude, so much more 0:21:36.600 --> 0:21:40.359 so much smaller that it's difficult to even explain. But 0:21:40.760 --> 0:21:43.800 if you were to have a supernova explode in the 0:21:43.840 --> 0:21:48.840 Milky Way galaxy, in our galaxy, the gravitational waves generated 0:21:48.880 --> 0:21:53.200 by that explosion would maybe be powerful enough to distort 0:21:53.240 --> 0:21:56.679 the distance between the Earth and the Sun by about 0:21:56.720 --> 0:22:02.480 the diameter of a hydrogen atom, so not noticeable to 0:22:02.560 --> 0:22:06.600 any degree, and not at least to human senses. So 0:22:06.640 --> 0:22:08.320 if you were to even go on a smaller scale, 0:22:08.359 --> 0:22:11.280 let's say that you pick two points that are a 0:22:11.320 --> 0:22:15.360 kilometer apart here on the surface of the Earth, the 0:22:15.400 --> 0:22:18.680 amount of distortion would be equivalent to a few thousandth 0:22:18.880 --> 0:22:22.600 of the diameter of a proton, So you're talking about 0:22:22.600 --> 0:22:26.680 a subatomic particle, and just a tiny, tiny, tiny fraction 0:22:26.840 --> 0:22:30.159 of that subatomic particles diameter would be the amount of 0:22:30.200 --> 0:22:34.040 distortion that would happen across a kilometer worth of distance 0:22:34.080 --> 0:22:38.520 here on Earth. Again, that means it's so small that 0:22:38.720 --> 0:22:42.760 it's incredibly difficult to detect, so much so that Einstein 0:22:42.880 --> 0:22:46.560 himself was pretty sure we would never be able to 0:22:46.640 --> 0:22:50.159 directly detect gravitational waves because he could not imagine a 0:22:50.200 --> 0:22:53.040 system that would be sensitive enough to pick up such 0:22:53.119 --> 0:22:58.640 a minute change, a distortion that's happening so quickly because 0:22:58.680 --> 0:23:01.920 it's a fraction of a second, and it's so small 0:23:02.119 --> 0:23:07.240 as to be unnoticeable. So the other problem here is 0:23:07.280 --> 0:23:10.280 not just that it's such a very tiny effect that 0:23:10.359 --> 0:23:12.919 lasts a short amount of time. It's also that a 0:23:12.920 --> 0:23:16.359 lot of other stuff could create false positives. You can 0:23:16.440 --> 0:23:22.880 have incredibly instrumentation, but if that instrument is really really sensitive, 0:23:23.400 --> 0:23:26.880 any sort of interference could set off and you could 0:23:26.960 --> 0:23:30.680 end up getting false readings. So a change in air 0:23:30.720 --> 0:23:36.720 pressure or temperature, or seismic activity, even a heavy truck 0:23:36.800 --> 0:23:41.000 driving nearby could set off false results. So you'd have 0:23:41.040 --> 0:23:43.720 to come up with a really clever way to measure distortion, 0:23:43.840 --> 0:23:47.760 to limit vibration, and to eliminate the chance that it 0:23:47.800 --> 0:23:50.679 was a false positive. And Lego is the answer to 0:23:50.760 --> 0:23:54.560 all of that. So the Lego Observatory is actually the 0:23:54.600 --> 0:23:59.120 result of decades of collaborative work among different scientific research 0:23:59.160 --> 0:24:03.240 centers and internet national bodies and universities, and all started 0:24:03.280 --> 0:24:06.639 back in nineteen seventy nine. That's when the National Science 0:24:06.680 --> 0:24:10.560 Foundation approved funds for Caltech and MIT to develop laser 0:24:10.560 --> 0:24:14.399 interferometer research and development. And a few years later, in 0:24:14.480 --> 0:24:17.600 nineteen eighty three, Caltech and MIT submitted a proposal for 0:24:17.680 --> 0:24:22.879 a kilometer scale detector. But keep in mind, all right, 0:24:22.920 --> 0:24:25.159 so in nineteen seventy nine you get the funding for 0:24:25.400 --> 0:24:28.879 R and d nineteen eighty three, there's the submission of 0:24:28.880 --> 0:24:33.840 a proposal for a kilometer scale detector. There wouldn't be 0:24:33.880 --> 0:24:38.520 approval for a detector until nineteen ninety, so almost a 0:24:38.680 --> 0:24:44.720 decade later, and which turns out was probably okay, because 0:24:44.720 --> 0:24:50.240 we really didn't have the technological ability to detect things 0:24:50.280 --> 0:24:53.640 on a scale small enough to register a gravitational wave 0:24:53.640 --> 0:24:57.560 in the first place. But still, you know, a decade's 0:24:57.560 --> 0:24:59.920 delay before you even get approval is still pretty rough. 0:25:00.880 --> 0:25:05.920 Construction didn't begin until nineteen ninety four. The inauguration of 0:25:05.960 --> 0:25:10.119 the Ligo Observatory took place in nineteen ninety nine, but 0:25:10.200 --> 0:25:14.320 even then that didn't mean that the observatory was online 0:25:14.359 --> 0:25:17.640 collecting data. It didn't do that until two thousand and two. 0:25:18.800 --> 0:25:23.320 And here's the kicker. Eventually scientists came to the conclusion 0:25:23.440 --> 0:25:27.719 that this Ligo observatory was not sensitive enough to detect 0:25:27.720 --> 0:25:30.600 gravitational waves. That despite the fact that it was this 0:25:31.440 --> 0:25:36.400 large detector or pair of large detectors, actually because again 0:25:36.440 --> 0:25:40.840 one in Louisiana one in Washington, it wasn't sensitive enough 0:25:41.040 --> 0:25:44.919 to be effective. So it was not quite back to 0:25:44.960 --> 0:25:47.600 the drawing board, but it did mean that they had 0:25:47.640 --> 0:25:52.240 to think about how they would upgrade these facilities so 0:25:52.280 --> 0:25:54.439 that they could be sensitive enough to pick up a 0:25:54.440 --> 0:25:58.320 gravitational wave. So in twenty ten, Ligo went offline to 0:25:58.440 --> 0:26:03.399 undergo a big overhaul, and it took four years of 0:26:03.440 --> 0:26:07.480 construction and testing to get it into shape and another 0:26:07.560 --> 0:26:10.760 year to set it up for new observations, which means 0:26:10.760 --> 0:26:13.080 that it wasn't until twenty fifteen that it was ready 0:26:13.119 --> 0:26:16.399 to come back online. By now it was called the 0:26:16.440 --> 0:26:20.880