1 00:00:00,000 --> 00:00:00,500 English 2 00:00:00,500 --> 00:00:02,000 3 00:00:02,000 --> 00:00:03,420 4 00:00:03,420 --> 00:00:05,420 World Science Festival(Gravitational Waves) 5 00:00:05,420 --> 00:00:06,100 Applause 6 00:00:08,040 --> 00:00:08,760 Thank you. 7 00:00:13,180 --> 00:00:13,900 Thank you. 8 00:00:15,220 --> 00:00:16,720 Appreciate that thank you, I am Brian Green 9 00:00:16,720 --> 00:00:18,520 co-founder with Tracy and I also 10 00:00:18,520 --> 00:00:21,060 want to welcome you to day four 11 00:00:21,060 --> 00:00:23,600 of the 2016 world science festival. 12 00:00:23,720 --> 00:00:26,200 The program tonight 13 00:00:26,260 --> 00:00:28,800 on gravitational waves 14 00:00:28,800 --> 00:00:32,260 its a timely program I trust you all 15 00:00:32,260 --> 00:00:34,260 heard the announcement on 16 00:00:34,260 --> 00:00:36,660 February 11 through you read about it 17 00:00:37,360 --> 00:00:39,300 The first direct detection 18 00:00:39,300 --> 00:00:41,220 of gravitational waves. 19 00:00:41,400 --> 00:00:42,260 amazing, amazing discovery. 20 00:00:42,260 --> 00:00:44,260 [clapping] 21 00:00:44,260 --> 00:00:47,220 [clapping] 22 00:00:47,220 --> 00:00:49,300 and we have here tonight 23 00:00:49,300 --> 00:00:53,980 a group of very individuals who made this discovery 24 00:00:54,300 --> 00:00:55,120 possible 25 00:00:55,120 --> 00:00:56,260 And I'm gonna bring amount just a little bit, 26 00:00:56,320 --> 00:00:59,020 but just a few words at the outset 27 00:00:59,560 --> 00:01:04,120 You know this discovery - to put it in context, 28 00:01:04,120 --> 00:01:10,080 it's a kind of achievement that happens maybe a few times a century 29 00:01:10,080 --> 00:01:11,580 in fundamental science 30 00:01:11,580 --> 00:01:16,700 I mean we were thrilled some years ago for the discovery of the Higgs boson 31 00:01:16,700 --> 00:01:22,960 something that was searched for - for very long period of time and finally was definitively discovered at CERN 32 00:01:22,960 --> 00:01:24,520 Great discovery. 33 00:01:24,520 --> 00:01:32,400 This ranks on par with that kind of experimental observational achievement 34 00:01:32,400 --> 00:01:38,220 and the other side of the story that will come out in the conversation here tonight is that 35 00:01:38,220 --> 00:01:47,200 we're as for the Higgs boson just about everybody was convinced that the experiments would succeed. 36 00:01:48,140 --> 00:01:53,220 mean most people who are following closely the search for the Higgs boson 37 00:01:53,220 --> 00:01:56,780 were saying well if it's not found that's the craziness 38 00:01:56,780 --> 00:01:58,900 means that is got to work out 39 00:01:59,320 --> 00:02:02,800 the theory said that all of the circumstantial evidence 40 00:02:02,800 --> 00:02:06,540 suggests that the particle is out there and indeed it was found 41 00:02:07,080 --> 00:02:09,280 Now with gravitational waves as we'll see 42 00:02:09,280 --> 00:02:12,240 there was never really any doubt 43 00:02:12,240 --> 00:02:16,180 after ... I don't know call it 1950-1960 44 00:02:16,480 --> 00:02:24,340 that these ripple and the fabric of space were a real feature of Einstein's general theory of relativity 45 00:02:24,340 --> 00:02:24,840 46 00:02:24,840 --> 00:02:29,500 but there definitely was controversy as to whether we would ever have the capacity 47 00:02:30,440 --> 00:02:32,820 to catch one of these waves and 48 00:02:32,820 --> 00:02:39,080 we'll hear about why in just a moment, but what it means is 49 00:02:39,080 --> 00:02:43,200 it takes a certain kind of internal fortitude 50 00:02:43,620 --> 00:02:45,420 it takes a certain kind of vision, 51 00:02:45,900 --> 00:02:48,980 it takes a certain kind of stubbornness 52 00:02:49,280 --> 00:02:52,360 it takes a certain kind of independent spirit 53 00:02:53,520 --> 00:02:56,620 to devote your life to this kind of project 54 00:02:56,620 --> 00:03:01,400 and our hats are off to individuals - they now number roughly 55 00:03:01,680 --> 00:03:06,080 a thousand - who made this discovery possible 56 00:03:07,040 --> 00:03:11,080 OK, a little bit of a background before I bring 57 00:03:11,640 --> 00:03:17,840 the panels on stage just to set the stage scientifically, right so 58 00:03:18,800 --> 00:03:25,920 we're all more or less familiar by this stage of the game that Albert Einstein gave us a new theory of gravity 59 00:03:26,140 --> 00:03:30,040 in 1915 the general theory of relativity 60 00:03:30,400 --> 00:03:37,000 The Newtonian picture that we all learned in high school simply spoke about objects pulling on each other 61 00:03:37,220 --> 00:03:38,680 through space 62 00:03:38,900 --> 00:03:40,360 with some sort of 63 00:03:40,800 --> 00:03:48,980 force that was described mathematically but whose mechanism of exerting its influence was 64 00:03:49,640 --> 00:03:51,240 not articulated 65 00:03:51,700 --> 00:03:56,220 Albert Einstein comes along and articulates a way that this force 66 00:03:56,620 --> 00:03:59,920 is communicative and just to give a picture of it, we can bring up 67 00:04:00,380 --> 00:04:02,000 the first little clip here 68 00:04:02,980 --> 00:04:04,020 It goes like this 69 00:04:04,360 --> 00:04:06,620 objects within bring like some free will 70 00:04:06,980 --> 00:04:08,660 like the sun or the planet 71 00:04:09,020 --> 00:04:11,060 They warp the environment 72 00:04:11,060 --> 00:04:13,100 of space and time 73 00:04:13,100 --> 00:04:15,860 and it is warps encurves the space 74 00:04:15,860 --> 00:04:19,220 that are able to cause other objects to move along 75 00:04:19,280 --> 00:04:22,920 peculiar trajectory if you weren't aware of this picture 76 00:04:23,240 --> 00:04:26,960 the metaphor that we love to use, it's imperfect to be sure 77 00:04:27,120 --> 00:04:31,440 but if you think about space and time as sort of like a trampoline 78 00:04:31,880 --> 00:04:34,620 you put some heavy objects in the middle of it it warps 79 00:04:34,620 --> 00:04:38,760 the surface and then if you roll a marble, a marble goes into orbit 80 00:04:38,760 --> 00:04:40,520 much like a planet would 81 00:04:40,900 --> 00:04:46,480 much the same way the sun warps the environment and then the planets go into the 82 00:04:46,480 --> 00:04:49,100 orbital trajectory that we are familiar with 83 00:04:49,280 --> 00:04:54,520 OK, so Einstein give this very beautiful new description 84 00:04:54,520 --> 00:04:59,200 of gravity in 1915 and then the question of course is 85 00:04:59,320 --> 00:05:06,260 "Is it correct?" and indeed they were very quickly to pieces of evidence that seal the deal 86 00:05:06,260 --> 00:05:12,380 The first was an explanation of a puzzle have to do the motion of the planet Mercury 87 00:05:12,660 --> 00:05:17,980 according to Newtonian gravity the planet should just trace out the same orbit 88 00:05:17,980 --> 00:05:20,340 year after year after year 89 00:05:20,600 --> 00:05:24,020 but observation shows the orbit's actually shifting a little bit 90 00:05:24,360 --> 00:05:27,600 Nobody could get a good explanation of this 91 00:05:27,600 --> 00:05:34,200 Einstein comes along and uses his new approach, the new picture of gravity, uses the equation of general relativity 92 00:05:34,200 --> 00:05:37,020 and is able to spot on predict 93 00:05:37,220 --> 00:05:42,360 this sort of procession of perihelion of Mercury 94 00:05:42,360 --> 00:05:47,720 now that was kind of a post diction explaining a puzzle that was already known observationally 95 00:05:48,260 --> 00:05:52,360 But then he was able to go further and make a prediction 96 00:05:52,360 --> 00:05:54,220 for something that has not yet been seen 97 00:05:54,500 --> 00:06:00,340 and indeed that had to do with the bending of light by the sun so 98 00:06:00,340 --> 00:06:06,040 if you have a distant star, it sends like toward the earth going in night trajectory of the sort 99 00:06:06,340 --> 00:06:12,960 but then later on if the earth is on the other side of the sun and you now consider that starlike 100 00:06:12,960 --> 00:06:20,800 according to Einstein new picture it's going to go in a curve trajectory as it goes to the curve environment surrounding the sun 101 00:06:21,200 --> 00:06:26,660 and that has the affect of making the position of the star in the sky shift 102 00:06:27,820 --> 00:06:31,760 Einstein was able to use the equation of general relativity to calculate the angle 103 00:06:32,200 --> 00:06:39,140 and it was just a few years later that team of astronomers went out and measured 104 00:06:39,140 --> 00:06:43,220 the angle between those two positions, taking photographic place during a solar eclipse 105 00:06:43,400 --> 00:06:48,520 so you could see the distant star compared with photographic place taken 6 months earlier 106 00:06:48,600 --> 00:06:50,320 and indeed the data 107 00:06:50,320 --> 00:06:51,820 with a little bit of 108 00:06:51,820 --> 00:06:58,280 massaging, little bit of force, a little bit of knowing answer in this particular case 109 00:06:58,460 --> 00:07:01,600 seem to show that Einstein ideas were correct. 110 00:07:01,600 --> 00:07:04,320 Now since then these experiments have been done 111 00:07:04,320 --> 00:07:05,260 over and over. 112 00:07:05,260 --> 00:07:09,680 There's no doubt any longer that Einstein's theory is correct. 113 00:07:10,360 --> 00:07:17,640 Now, Einstein then went further and as we'll discuss here tonight 114 00:07:17,960 --> 00:07:23,680 He wrote a paper in 1916 in which he basically said 115 00:07:23,960 --> 00:07:26,200 he didn't use quite this language 116 00:07:26,460 --> 00:07:33,200 basically said mathematically that if space is sort of like a trampoline and it can warp and curve 117 00:07:34,820 --> 00:07:41,820 well if you start to tap the trampoline, disturb the trampoline you'll send ripple going along the trampoline 118 00:07:43,300 --> 00:07:51,120 Those ripples, taking away the metaphor, were the ripples in the fabric of space and that's what gravitational waves are 119 00:07:51,120 --> 00:07:56,640 Now the very interesting story that we get into a little bit in just a moment with our panels is 120 00:07:57,660 --> 00:08:02,980 Einstein himself he writes his paper 1916 actually made a little mistake 121 00:08:03,160 --> 00:08:09,640 and maybe it's kind of weird concept - Einstein making a mistake in doing calculation of relativity. 122 00:08:10,620 --> 00:08:13,420 But relativity is hard 123 00:08:13,680 --> 00:08:19,060 and Einstein was the first one who's actually working on this calculation 124 00:08:19,200 --> 00:08:22,720 so he was making what we now call mistakes of a beginner 125 00:08:23,100 --> 00:08:24,480 Novice mistakes. 126 00:08:24,480 --> 00:08:27,060 But he was the guy who plays in the trail, 127 00:08:27,060 --> 00:08:30,360 so it makes perfect sense that he might have make those kind of errors. 128 00:08:30,360 --> 00:08:38,380 Anyway, he corrects the error in 1918 but then he continues to have a really interesting relationship with this idea 129 00:08:39,960 --> 00:08:44,860 thinks it's not quite right, writes a later paper that suggests that's not right. 130 00:08:45,000 --> 00:08:51,500 Bottom line is others come along develop a very beautiful systematic framework for avoiding the pitfall 131 00:08:52,460 --> 00:08:57,220 that Einstein fell into and people absolutely certain that these things are real 132 00:08:57,220 --> 00:09:02,680 What would that mean? It means that if you disturb the fabric of space you should get the gravitational waves, the ripples. 133 00:09:04,180 --> 00:09:07,460 and typical example might be something like this 134 00:09:07,460 --> 00:09:13,260 rapidly orbiting neutron stars or black hole sending out this march of gravitational waves 135 00:09:14,480 --> 00:09:20,400 and as we discuss here tonight what would that mean for somebody in the wake of these waves 136 00:09:20,400 --> 00:09:25,120 the object would be stretched or squeezed according to the map. I just wanna emphasize one thing 137 00:09:26,060 --> 00:09:27,500 This is not true scale 138 00:09:28,200 --> 00:09:29,260 [laugh] 139 00:09:30,820 --> 00:09:32,180 and that is a big deal 140 00:09:33,440 --> 00:09:40,640 because when you actually do this calculation out, you will discover that the stretching and squeezing is so small that it is enormous challenge 141 00:09:43,760 --> 00:09:47,840 to detect this gravitational wave and that the Ligo team has done 142 00:09:48,960 --> 00:09:52,320 Alright now, lets get into the actual discussion 143 00:09:52,520 --> 00:09:54,780 I gonna bring in our panelist on 144 00:09:56,320 --> 00:10:00,660 and let us begin with Rai Weiss of MIT 145 00:10:00,900 --> 00:10:09,560 is one of the creator of LIGO. He first proposed large scale interferometer back in 1972 and he has been scientific and engineering leader ever since 146 00:10:17,260 --> 00:10:26,140 Alright next Barry Barish, many people say that Barry Barish of Caltech saved LIGO at the time it transition into big science 147 00:10:26,700 --> 00:10:29,960 and built the two huge detectors in Louisiana Washington state 148 00:10:30,140 --> 00:10:32,700 He joined LIGO in 1994 149 00:10:32,880 --> 00:10:37,620 and was director for 1997 to 2005. Welcome 150 00:10:39,060 --> 00:10:42,120 Next up, Nergis Mavalvala 151 00:10:42,840 --> 00:10:44,840 I got it. I'm so proud of myself 152 00:10:45,460 --> 00:10:50,980 of MIT, is an astrophysicist who was called a genius award winner for work on LIGO in 2010 153 00:10:52,380 --> 00:10:57,840 She got a PhD from MIT in 1997, post-doctoral Caltech from 97 to 2002 154 00:10:58,120 --> 00:11:01,460 and then joined the faculty of MIT. Welcome. 155 00:11:01,500 --> 00:11:06,780 Next up, Frans Pretorius , who is professor of physics at Princeton University 156 00:11:06,780 --> 00:11:13,820 His primary field of research is general relativity specializing in numerical solution through Einstein's equation 157 00:11:14,780 --> 00:11:17,900 and now we'll see a vital part of this discovery 158 00:11:18,300 --> 00:11:25,020 Finally, David Schoemaker, who is director of the MIT LIGO lab and was the team leader of advanced LIGO 159 00:11:25,100 --> 00:11:28,200 He spent many years upgrading the technology of the observatory