1 00:00:14,720 --> 00:00:19,200 "The Universe was created in the beginning. 2 00:00:20,240 --> 00:00:27,500 It angered many, and was generally considered a bad move. "- Douglas Adams 3 00:00:39,460 --> 00:00:42,460 Good evening, I'm Robert the Queen. 4 00:00:43,140 --> 00:00:48,560 No, I'm Brian Green, and I'll make an overture for some of the ideas in the Infinite Worlds program 5 00:00:48,640 --> 00:00:51,100 which we will discuss here tonight. 6 00:00:51,100 --> 00:00:55,920 One way to frame the discussion is to recognize the fact 7 00:00:55,920 --> 00:01:00,940 that over the last few centuries, our understanding of the universe has been seriously increased 8 00:01:00,940 --> 00:01:03,160 and in huge jumps. 9 00:01:03,180 --> 00:01:08,100 The program of the festival has covered a miniature part of a huge amount of knowledge in the last few days 10 00:01:08,100 --> 00:01:10,680 which we were fortunate to achieve. 11 00:01:10,680 --> 00:01:17,060 But there is one unexpected implication of knowledge that we have achieved 12 00:01:17,060 --> 00:01:20,760 which is that we are subject to some kind of setback. 13 00:01:20,760 --> 00:01:26,600 Our species has in some ways consequently gone through a series of regrets through the various types of our discoveries. 14 00:01:26,600 --> 00:01:31,580 Think about it: a long time ago we thought Earth was the center of the universe. 15 00:01:31,700 --> 00:01:36,680 and then people like Copernicus or Galileo came forward and they recognized 16 00:01:36,780 --> 00:01:41,540 that the Earth revolves around the Sun, and then we thought the Sun was the center of the universe 17 00:01:41,540 --> 00:01:45,940 and then we realized that the sun was one of hundreds of billions of stars in our galaxy. 18 00:01:45,940 --> 00:01:49,100 Then, Hubble and others appeared, and realized that it was even our galaxy 19 00:01:49,260 --> 00:01:53,760 just one of many, many galaxies. 20 00:01:53,940 --> 00:01:56,920 What we're going to talk about tonight 21 00:01:57,100 --> 00:02:01,980 is perhaps another step in the process of backtracking from the idea that we are at the center. 22 00:02:02,120 --> 00:02:06,740 And this is the idea that our universe may not be the only universe. 23 00:02:06,840 --> 00:02:10,860 There may be many universes, and we are just one of them. 24 00:02:11,360 --> 00:02:15,720 The picture we could imagine is that the universe is a huge cosmic bubble bath 25 00:02:15,720 --> 00:02:18,580 whereby all bubbles are different universes. 26 00:02:18,580 --> 00:02:22,040 Our universe is then a bubble in that whole. 27 00:02:22,040 --> 00:02:26,240 What I want to do in the next few minutes of this preamble 28 00:02:26,360 --> 00:02:32,220 is to give you a sense of the basic ideas that lead to that play 29 00:02:32,220 --> 00:02:37,320 and then we will move on to a discussion where we explore these ideas in more detail. 30 00:02:37,320 --> 00:02:44,020 The key physics behind all this is gravity physics. 31 00:02:44,020 --> 00:02:46,020 Let's start from there. 32 00:02:46,020 --> 00:02:50,060 Gravity we all know - Newton introduced us 33 00:02:50,060 --> 00:02:53,760 the way we should think about it back in the 17th century. 34 00:02:53,760 --> 00:02:57,440 Basically, he made an interesting formula, Eq 35 00:02:57,440 --> 00:03:03,140 which tells us that any body in the universe is attracted to any other body by force, by the force of gravity 36 00:03:03,140 --> 00:03:08,980 which depends on two things: the size, the mass of the body and the distance between them in space. 37 00:03:09,080 --> 00:03:12,760 A very simple equation that we still teach high school students today 38 00:03:12,900 --> 00:03:16,540 hundreds of years later, and we still use that same equation 39 00:03:16,540 --> 00:03:20,380 when we try to launch spacecraft to land on the moon 40 00:03:20,380 --> 00:03:23,340 or encountered other astrophysical bodies. 41 00:03:23,340 --> 00:03:27,520 So it's a very powerful method of thinking about gravity. 42 00:03:27,520 --> 00:03:33,880 Still, Albert Einstein realized in the early 20th century that something essential was missing 43 00:03:33,880 --> 00:03:36,900 in Newton's vision of gravity. 44 00:03:36,900 --> 00:03:43,920 And that is Newton wrote a formula that describes the force of attraction between two bodies, 45 00:03:43,920 --> 00:03:49,900 but he never explained the way those bodies exert this force of attraction, 46 00:03:49,900 --> 00:03:54,480 how they exert that mutual gravitational pull. 47 00:03:54,480 --> 00:04:01,340 And Einstein deeply wanted to understand the mechanism by which gravity works. 48 00:04:01,340 --> 00:04:08,620 And according to the famous story, he embarked on the path of discovering this mechanism underlying the force of gravity 49 00:04:08,620 --> 00:04:12,700 by turning to Newton's Principia - a book that has all the results of mathematics and physics 50 00:04:12,700 --> 00:04:19,960 that Newton discovered for life, and which you should read for tonight's discussion, you know what it is. 51 00:04:19,960 --> 00:04:26,840 In fact, I was a little surprised to read in the booklet that the book should have been read in the original Latin. 52 00:04:26,840 --> 00:04:30,360 I never did, but you are all one step ahead of me. 53 00:04:30,360 --> 00:04:35,500 So Einstein opens the book, looks under the letter G, finds "The Law of Gravity", 54 00:04:35,500 --> 00:04:42,180 search for a little more, look for the subtitle under the letter M - "The mechanism by which gravity acts". 55 00:04:42,180 --> 00:04:48,380 And he finds something surprising there, because Newton basically says, "I don't know how gravity works." 56 00:04:48,380 --> 00:04:52,500 "I can write an equation that describes her strength, but how she performs it - I don't know." 57 00:04:52,500 --> 00:05:03,340 In fact, his words were; "The answer to that important question - the mechanisms by which gravity works - I leave to the reader for consideration." 58 00:05:03,340 --> 00:05:07,860 Most readers will read this and continue reading. 59 00:05:07,860 --> 00:05:13,940 Einstein was different, and he spent ten long years trying to understand how gravity works. 60 00:05:13,940 --> 00:05:20,100 And finally, by 1915 he came up with an answer in a theory called general relativity. 61 00:05:20,100 --> 00:05:25,220 And the answer is subtle and beautiful. There is a quick way to understand what he has discovered, 62 00:05:25,220 --> 00:05:27,220 and this is just this: 63 00:05:27,220 --> 00:05:32,740 Einstein said that if the sun is here and the earth there and in between is essentially empty space, 64 00:05:32,740 --> 00:05:37,100 the force of gravity must then be mediated in some way by empty space. 65 00:05:37,100 --> 00:05:43,100 Space itself must somehow be that mechanism by which gravity exerts its influence. 66 00:05:43,100 --> 00:05:49,260 And the way to think about it first, I'll show you the visualization in a minute, is to forget about gravity for a second, 67 00:05:49,260 --> 00:05:51,840 use the analogy that physicists adore. 68 00:05:51,840 --> 00:05:57,360 Imagine having a rubber sock tightened in front of you. You take the clicker and roll it over the surface. 69 00:05:57,360 --> 00:06:00,140 It will go in the right line - it's easy to imagine. 70 00:06:00,140 --> 00:06:04,080 If I now take a heavy object and put it in the middle of the stocking, the stocking will distort. 71 00:06:04,080 --> 00:06:09,560 If I roll the clicker now, it won't go in the right line, but it will roll in the wrong trajectory, 72 00:06:09,560 --> 00:06:13,780 rolling on the curved surface of the rubber sheet. 73 00:06:13,780 --> 00:06:19,640 Einstein said, "Apply that simple idea to the universe." Instead of a rubber sheet - on the fabric of the room. 74 00:06:19,640 --> 00:06:22,740 More specifically, the fabric of space and time all around us. 75 00:06:22,740 --> 00:06:29,380 And he also said that when the body is in space, it makes the space bend and thus affect the movement of other bodies, 76 00:06:29,380 --> 00:06:33,620 in a similar way that a distorted rubber sheet affects the movement of the clicker. 77 00:06:33,620 --> 00:06:37,120 In order to get a picture of what this would look like, 78 00:06:38,940 --> 00:06:47,380 Let’s imagine the fabric of space as a lattice area. This is now a three-dimensional space, making it harder to work visually 79 00:06:47,580 --> 00:06:51,860 and so we will move on to a two-dimensional analog showing all ideas. 80 00:06:51,860 --> 00:06:54,260 And you see, space is flat when empty 81 00:06:54,260 --> 00:06:56,920 but when the sun comes up, the fabric curves. 82 00:06:56,940 --> 00:07:01,660 Similarly, if you look at space near Earth, the fabric curves around it. 83 00:07:01,660 --> 00:07:05,420 Pay attention to the moon as this is the main point. 84 00:07:05,420 --> 00:07:13,900 The moon is kept in orbit as it rolls across the valley in the distorted middle that Earth creates. 85 00:07:13,900 --> 00:07:20,320 It is a means of communication of gravity, it is a mechanism of action of gravitational force. 86 00:07:20,320 --> 00:07:26,560 If we move away, we will see that the Earth is also in orbit as it also rolls on the distorted part of the fabric of space 87 00:07:26,740 --> 00:07:28,740 that creates the Sun. 88 00:07:28,740 --> 00:07:35,300 This, according to Einstein, is how gravity works. 89 00:07:35,300 --> 00:07:38,000 He wrote this theory between 1915 and 1916. 90 00:07:38,000 --> 00:07:46,140 Shortly thereafter, people around the world began to think deeply about this general theory of relativity and these ideas, 91 00:07:46,140 --> 00:07:52,300 and in particular, this interesting physicist, a Belgian priest - a priest who is also a physicist, 92 00:07:52,300 --> 00:07:59,940 who came to Einstein's work and decided to apply his ideas not to the sun and earth, 93 00:08:00,080 --> 00:08:02,080 but to the whole universe. 94 00:08:02,080 --> 00:08:06,940 And when he applied Einstein's ideas to the entire universe, he came across something very interesting. 95 00:08:06,940 --> 00:08:14,860 He found that the fabric of space should either expand or narrow. It is not possible for it to be static. 96 00:08:14,860 --> 00:08:21,240 So he predicted that one solution might be that the universe may be growing over time, expanding. 97 00:08:21,240 --> 00:08:26,620 He presented his idea to Einstein, and Einstein told him: 98 00:08:26,620 --> 00:08:31,780 "Math is fine for you, but your physics is abominable." 99 00:08:32,700 --> 00:08:39,820 And what he wasted on was thinking he was already through it. There was an earlier physicist, Alexander Friedman 100 00:08:39,820 --> 00:08:46,340 which looks a lot like my accountant before tax. 101 00:08:48,540 --> 00:08:55,440 Friedman had already discovered this idea of ​​an expanding universe and told Einstein, 102 00:08:55,440 --> 00:09:01,000 Einstein first thought that Friedman had made a mathematical mistake, even stated it in public. 103 00:09:01,000 --> 00:09:05,660 Friedman convinced him there were no mathematical errors. 104 00:09:05,660 --> 00:09:08,760 So when Lemetre introduced the same idea, Einstein said: 105 00:09:08,760 --> 00:09:14,140 "Yes, yes, the math is correct, but your interpretation that the universe is expanding is simply pointless. 106 00:09:14,140 --> 00:09:18,360 Look at the sky, the universe is obviously not expanding. " 107 00:09:18,360 --> 00:09:24,900 So in Einstein's mind it was clear how the universe should behave. 108 00:09:24,900 --> 00:09:31,720 In fact, he was so sure, that he returned to the math of general relativity and adjusted it to get rid of the possibilities 109 00:09:31,720 --> 00:09:35,180 that the universe is expanding. 110 00:09:35,180 --> 00:09:43,860 What followed was wonderful: in 1929, this gentleman, Edwin Hubble, an American-born astronomer, educated at Oxford, 111 00:09:43,860 --> 00:09:54,380 studied the motion of various bodies, galaxies, using this 250cm telescope in an observatory on Mount Wilson, 112 00:09:54,380 --> 00:09:58,780 and discovered that distant galaxies were actually moving away. 113 00:09:58,780 --> 00:10:04,600 And to move away by a certain pattern that is consistent with the textile of the expanding space. 114 00:10:04,600 --> 00:10:10,880 It is as if galaxies are sewn onto the fabric of space, and as the fabric expands, 115 00:10:10,880 --> 00:10:16,660 galaxies are moving away from each other, the universe is expanding. 116 00:10:16,660 --> 00:10:21,340 This has contributed to the development of what we call the Big Bang. 117 00:10:21,360 --> 00:10:26,520 Ideas that the universe began as small and then magnified. 118 00:10:26,520 --> 00:10:33,240 Picture it like this: imagine that the universe started out as a very small, thick, hot lump, 119 00:10:33,260 --> 00:10:42,180 and then it spreads. The space expands, and as the space expands, the hot primordial plasma cools. 120 00:10:42,180 --> 00:10:47,660 As things spread, they cooled, and as cooling began, structures could begin to come together, 121 00:10:47,660 --> 00:10:54,940 structures that will finally create galaxies and stars within galaxies, and that will create things that you can see 122 00:10:55,020 --> 00:10:58,660 in a beautiful, dark, clear night sky. 123 00:10:58,660 --> 00:11:08,020 So this is an image that has finally grown out of this way of thinking about gravity and how the universe evolves over time. 124 00:11:08,020 --> 00:11:14,880 I do not want to give the impression that everyone immediately believed in this way of seeing the universe. 125 00:11:14,880 --> 00:11:20,660 There was definitely a need to find other experiments, other discoveries that would convince people 126 00:11:20,660 --> 00:11:27,420 that this is the right way to think about the origin and evolution of the universe. 127 00:11:27,420 --> 00:11:33,480 And one man, George Gamow, played a particularly important role in this. 128 00:11:33,480 --> 00:11:39,340 George Gamow was an interesting character. 190cm tall, charismatic Russian physicist 129 00:11:39,340 --> 00:11:43,880 who was fast-paced and loved as much fun as he was worth. 130 00:11:45,460 --> 00:11:51,740 He and his wife tried to escape from the Soviet Union in a very interesting way. 131 00:11:51,820 --> 00:12:00,860 They filled the kayak with only brandy and fine chocolate and set out on a journey across the Black Sea. 132 00:12:00,860 --> 00:12:07,140 36 hours after they set off, they were found by authorities floating in a kayak. 133 00:12:07,140 --> 00:12:11,240 They were lucky to bring only alcohol and chocolate 134 00:12:11,240 --> 00:12:17,220 because that supported the story that they just went out for an afternoon paddle, not that they were actually trying to avoid it. 135 00:12:17,220 --> 00:12:24,220 However, a few years later, Gamov succeeded and, having passed under the Iron Curtain, came to America, 136 00:12:24,220 --> 00:12:30,560 and started thinking about cosmology and Einstein's ideas, and came up with the following simple idea: 137 00:12:30,560 --> 00:12:37,120 if the universe started out as very small and hot and then expanded - when things expand, they cool. 138 00:12:37,820 --> 00:12:45,880 This means that there should be some residual heat today in the space all around us that is left over from the Big Bang. 139 00:12:45,880 --> 00:12:53,320 And he said we should look into space and find that residual heat and those residual photons because that would support the image 140 00:12:53,340 --> 00:12:57,240 that the universe began as small and hot. 141 00:12:57,240 --> 00:13:06,800 That work is wonderful, he betrayed it, but he couldn't convince anyone to actually look for that radiation, the heat left behind after the Big Bang. 142 00:13:06,800 --> 00:13:11,400 One of the reasons is that the scientists were mostly focused on quantum mechanics 143 00:13:11,400 --> 00:13:14,760 and other aspects of physics rather than cosmology at that point. 144 00:13:14,760 --> 00:13:23,240 And the other reason why people didn't jump to study this is partly because Gamov had a reputation as a prankster. 145 00:13:24,800 --> 00:13:30,760 He once wrote a work with his student that played a vital role in recognition 146 00:13:30,760 --> 00:13:34,340 that there should be heat left behind by the Big Bang. 147 00:13:34,340 --> 00:13:36,340 The student's name was Ralf Alfer. 148 00:13:36,340 --> 00:13:47,180 And Gamov then persuaded this man on the left of the picture, Hans Bete, to put his name to work 149 00:13:47,180 --> 00:13:52,260 only for the authors to be Alfer-Bete-Gamov. 150 00:13:54,960 --> 00:14:02,900 It can actually pass for a physical joke as the standards are not too high. 151 00:14:04,900 --> 00:14:11,380 But it made an impression on people that he should not be taken as seriously as his work deserves. 152 00:14:11,380 --> 00:14:17,360 And that's why the work he wrote with Alfer and Robert Hermon essentially died. 153 00:14:17,420 --> 00:14:19,420 No one followed him. 154 00:14:20,140 --> 00:14:25,820 A few years later, because in physics, great ideas will eventually be rediscovered 155 00:14:25,820 --> 00:14:29,200 if no one continues at the time they were created, 156 00:14:29,200 --> 00:14:34,860 these two, Robert Dicky at Princeton and Jim Peebles, came up with the same idea - 157 00:14:34,860 --> 00:14:39,880 - that there should be residual heat from the Big Bang. They went through a similar calculation. 158 00:14:39,880 --> 00:14:43,720 They were an interesting couple because Dicky was a great experimentalist. 159 00:14:43,720 --> 00:14:48,700 They started making equipment to try and find that heat left over from the Big Bang. 160 00:14:48,700 --> 00:14:55,920 In the midst of their work, they got a phone call from these guys, Arn Penzias and Robert Wilson, 161 00:14:55,920 --> 00:15:01,580 a phone call that may be the most famous call in the history of cosmology. 162 00:15:02,380 --> 00:15:09,540 I guess it's not that impressive either. It's a bit like you're the cutest kid in fat training, or something. 163 00:15:10,760 --> 00:15:17,560 But this was an incredibly important moment, because these two who were about 30 miles away from Princeton 164 00:15:17,560 --> 00:15:22,460 working at Bel Labs and using that antenna you see behind them in the photo, 165 00:15:22,460 --> 00:15:30,000 they picked up sound, hiss, which they tried to get rid of by all means, cleaned the equipment and failed to get rid of it. 166 00:15:30,000 --> 00:15:37,600 At last they concluded that this hiss must be heat, the radiation lagging behind the Big Bang. 167 00:15:37,660 --> 00:15:43,180 So they called Dickie and told him what they had found. Dickie hung up and said, "They crossed us." 168 00:15:43,180 --> 00:15:47,940 These guys found it and really, they won a Nobel Prize for this discovery. 169 00:15:47,940 --> 00:15:53,000 So this endorsement of the Big Bang idea was a spectacular moment, 170 00:15:53,000 --> 00:16:02,080 but it was also a turning point, for that was the moment when cosmology entered the field of quantitative science. 171 00:16:02,080 --> 00:16:07,660 Because their observations as those of others after them, and the second Nobel Prize awarded 172 00:16:07,660 --> 00:16:12,700 To Mathers and Smut for these observations, they initiated a way to test these ideas. 173 00:16:12,700 --> 00:16:19,840 What I want to do now is show you a graph, a theoretical curve. It doesn't matter if you don't understand exactly what she means. 174 00:16:19,880 --> 00:16:24,080 It shows us the amount of heat at each individual frequency, 175 00:16:24,080 --> 00:16:29,740 the number of photons at each frequency, which should be all around us, lagged behind the Big Bang. 176 00:16:29,740 --> 00:16:32,280 And then I'll show you the measurement data. 177 00:16:32,280 --> 00:16:39,140 If you look at the chart, the curve will go from left to top and right. This is the theory, this is the Big Bang theory. 178 00:16:39,140 --> 00:16:45,540 And now we will see what the experimental observations say. It will be shown in red dots. 179 00:16:45,560 --> 00:16:52,280 You will notice that the red dots are placed exactly along the curve line. 180 00:16:52,280 --> 00:16:58,500 The very impressive overlap between theory and experiment allows people to believe that this is 181 00:16:58,640 --> 00:17:01,060 the right way of seeing the universe. 182 00:17:01,060 --> 00:17:04,920 This is great, but there are still some unresolved issues. 183 00:17:04,920 --> 00:17:09,080 And we will talk about some of these issues at the moment when the discussion begins, 184 00:17:09,080 --> 00:17:15,720 but when people look closely at the Big Bang theory, they see that it explains the way the universe evolved 185 00:17:15,720 --> 00:17:19,340 after it started to expand outside, 186 00:17:19,340 --> 00:17:21,340 but it does not say what triggered the expansion. 187 00:17:21,340 --> 00:17:24,440 She, by the way, omits the bang itself. 188 00:17:24,440 --> 00:17:28,460 That raises the question of what a bang in the Big Bang is, and it's hard to say what it could be. 189 00:17:28,460 --> 00:17:32,380 Usually gravity pulls things inwards, and what then would be pushing them outwards 190 00:17:32,380 --> 00:17:35,160 that would propel the universe toward expansion. 191 00:17:37,040 --> 00:17:43,420 There are many ideas about this, some more convincing than others. 192 00:17:45,400 --> 00:17:53,000 But there are these two guys: Alan Gut and Andre Linde, also Paul Steinhart at Princeton and Adreas Albrecht, 193 00:17:53,260 --> 00:18:00,240 who actually found the answer that we believe today is probably what happened. 194 00:18:00,240 --> 00:18:02,920 And you'll meet these two guys in no time. 195 00:18:02,920 --> 00:18:08,180 But what I want you to conclude from this slide, and the impression is amplified by the introduction of Friedman into it, 196 00:18:08,180 --> 00:18:13,480 is that modern cosmologists are really happy! 197 00:18:17,880 --> 00:18:21,520 But what did these guys find? They discovered the following: 198 00:18:21,520 --> 00:18:24,680 when we come back to Einstein, and that really comes to mind, 199 00:18:24,680 --> 00:18:29,140 gravity, according to Einstein, is not just an attractive force. 200 00:18:29,140 --> 00:18:33,240 Newton thought it was just an attractive force pulling things toward him. 201 00:18:33,240 --> 00:18:39,200 These guys think, reinforcing Einstein's observation, that if there is some kind of energy that permeates the space, 202 00:18:39,200 --> 00:18:41,960 the word field may appear later in the conversation, 203 00:18:41,960 --> 00:18:45,280 so if there is some energy, a field that pervades space, 204 00:18:45,280 --> 00:18:48,500 it can create repulsive gravity. 205 00:18:48,500 --> 00:18:53,920 Gravity that pushes out, which can make the universe, in a sense, shatter 206 00:18:53,920 --> 00:18:57,880 to disassemble, to give a burst to the Big Bang. 207 00:18:57,880 --> 00:19:04,380 The picture you get in a field called inflationary cosmology, which we will discuss for a moment, 208 00:19:04,380 --> 00:19:09,780 is that there is a tiny lump, this is this little shiny area on the left, 209 00:19:09,840 --> 00:19:16,820 a tiny lump of space becomes full of energy, triggering an incredible outburst, 210 00:19:16,820 --> 00:19:23,280 which causes the universe to expand and continue to expand, which we are witnessing today. 211 00:19:23,280 --> 00:19:25,280 This is inflationary cosmology. 212 00:19:25,280 --> 00:19:31,260 What I want to summon here is because the key thing I hope you will bring home with you tonight 213 00:19:31,260 --> 00:19:36,160 is that cosmology is not a bunch of theoretical ideas that people simply put forward 214 00:19:36,160 --> 00:19:38,160 so they hope they are true or false. 215 00:19:38,160 --> 00:19:40,160 It has become a quantitative science. 216 00:19:40,160 --> 00:19:48,120 The most quantitative way to understand, to convince ourselves that this is true, comes from understanding 217 00:19:48,120 --> 00:19:51,560 the heat remaining from the Big Bang, in the following sense: 218 00:19:51,560 --> 00:19:57,900 when the universe is very tiny, there is one feature of quantum physics - you don't have to know much about quantum physics, 219 00:19:57,900 --> 00:20:03,700 but quantum physics says there is always a certain amount of indeterminacy, a certain amount of fluctuating behavior that happens, 220 00:20:03,700 --> 00:20:07,420 and here it happens on the far left of the image when the universe is very small. 221 00:20:07,420 --> 00:20:13,400 But as the universe expands, the tremors of quantum mechanics expand. 222 00:20:13,400 --> 00:20:20,040 And when they do spread, they cause hot spots and cold spots in the sky. 223 00:20:20,040 --> 00:20:25,280 Tiny temperature differences, not large, in the thousandth part, for example, 224 00:20:25,280 --> 00:20:29,580 but these tiny differences in temperature can in principle be measured. 225 00:20:29,580 --> 00:20:34,500 And if you look at the green and yellow parts, they indicate temperature differences. 226 00:20:34,500 --> 00:20:37,720 Here it is shown in blue and red, but it is the same thing. 227 00:20:37,720 --> 00:20:43,360 These are hot spots and cold spots, generated by quantum fluctuations in the early universe. 228 00:20:43,360 --> 00:20:51,660 And the idea is that if you have a device, like this satellite on the right, it can measure hot and cold spots, 229 00:20:51,660 --> 00:20:58,800 because light travels to the satellite, then you will find what I will show you in the last convincing piece of information. 230 00:20:58,800 --> 00:21:04,920 This is a theoretical curve, created in quantum physics and inflationary cosmology. 231 00:21:04,920 --> 00:21:10,080 And this is the data. And I'll step back and let them go. 232 00:21:15,420 --> 00:21:19,020 Eh .. now. This is the data 233 00:21:19,020 --> 00:21:23,380 which were set 13.5 billion years ago. 234 00:21:23,380 --> 00:21:29,460 This curve was generated by us, human beings, 13.5 billion years later 235 00:21:29,460 --> 00:21:34,380 both the data and the curve match to fantastic precision. 236 00:21:34,380 --> 00:21:41,560 If you were to ask me what is the most beautiful image our civilization has created, 237 00:21:41,560 --> 00:21:46,160 yes, some things come to mind such as "Starry Sky", "Mona Lisa". 238 00:21:46,160 --> 00:21:50,240 For me, this would qualify among them. 239 00:21:50,240 --> 00:21:56,880 This picture is so spectacular, this agreement between theory and experiment. 240 00:21:56,880 --> 00:22:02,460 The last thing I want to point out before I finish, which is merging with this program, is this: 241 00:22:02,460 --> 00:22:11,000 the inventors of this inflationary cosmology realized something very interesting a few years after the first discovery. 242 00:22:11,000 --> 00:22:16,680 This kind of inflationary bang is very likely not a unique event. 243 00:22:16,680 --> 00:22:19,700 There can be many such inflationary explosions. 244 00:22:19,700 --> 00:22:25,960 In fact, the picture I like to have in my head is like a big piece of Swiss cheese. 245 00:22:25,960 --> 00:22:32,920 And if Swiss cheese is that cheesy piece of cheese, the energy that permeates the space, 246 00:22:32,920 --> 00:22:38,760 the idea is that the cheese is spreading, but in different places energy is dissipated and creates small openings, 247 00:22:38,760 --> 00:22:47,460 small bubbles that grow over time, and all bubbles in cheese are different universes. 248 00:22:47,460 --> 00:22:51,420 And our universe is one of those bubbles. 249 00:22:51,420 --> 00:22:57,220 This is how so many universes emerge from inflationary cosmology. 250 00:22:57,220 --> 00:23:01,300 I'll show you what it looks like. The last visualization. 251 00:23:01,300 --> 00:23:13,100 You will see a foggy gas-like entity appear, which will be like the cheese I described. 252 00:23:13,100 --> 00:23:17,160 It is this energy, the field that pervades space. And here it comes into view. 253 00:23:17,160 --> 00:23:22,340 The universe is expanding, creating a repulsive gravity that pushes everything apart. 254 00:23:22,340 --> 00:23:28,480 But in different places pockets are opened, regions where energy is weakened 255 00:23:28,480 --> 00:23:33,140 and is converted into more ordinary particles of matter and radiation. 256 00:23:33,140 --> 00:23:40,920 And all these openings in the picture would be different universes created in this huge expanding body. 257 00:23:40,920 --> 00:23:43,420 We call this the multiverse. 258 00:23:43,420 --> 00:23:51,400 Going into one of these would make it look like we had penetrated an ordinary universe like ours. 259 00:23:51,440 --> 00:23:56,100 And here is our universe. Just one of the bubbles in the cheese. 260 00:23:56,100 --> 00:24:02,780 The fact that it's a bubble makes it small on the outside, but it's not huge on the inside either - something we can talk about in a panel discussion. 261 00:24:02,780 --> 00:24:07,740 As you can see, we have galaxies on all sides and this can be our universe. 262 00:24:07,740 --> 00:24:14,360 And if we go out to see what's in another bubble, let's curl around and focus on one, 263 00:24:14,360 --> 00:24:19,520 if we go to another bubble, the world and physics can be a little different. 264 00:24:19,520 --> 00:24:22,840 His features do not have to be identical to ours. 265 00:24:22,840 --> 00:24:31,540 So all these worlds, all these different universes would be out there, embedded in this fast-paced, gaseous empire 266 00:24:31,540 --> 00:24:37,480 and our universe is just one bubble among many. 267 00:24:37,480 --> 00:24:46,420 If this picture of the universe is true and we can see the multiverse from the widest point, 268 00:24:46,420 --> 00:24:53,340 the idea is that we could see a huge assortment of worlds where different lumps of reality take place 269 00:24:53,340 --> 00:25:02,040 world by world as they evolve and change, as they go back and forth, they increase. 270 00:25:02,040 --> 00:25:11,820 The universe would in some sense be a huge assortment of bubbles where our universe is just one melodic beat 271 00:25:12,000 --> 00:25:16,800 in rich cosmic score. 272 00:30:28,960 --> 00:30:36,940 Claire Chase on the flute, Rebecca Heller on the bassoon, Eric Leyman on the flute and Joshua Ruben on clarinet. Thank you. 273 00:30:41,940 --> 00:30:47,900 I'm Robert the Queen, mentioned above, and I want to re-set the stage first, 274 00:30:47,900 --> 00:30:54,180 because when Brian does such things, he does them so well that you are all in the loop: "Oh, yes!". 275 00:30:54,180 --> 00:31:00,920 But I want to be careful here. Because until recently, many of you sitting here, like me, thought 276 00:31:00,920 --> 00:31:07,120 that the universe means everything that exists, everything you can imagine. 277 00:31:07,120 --> 00:31:11,640 And since the universe is everything, then there must be only one thing. 278 00:31:11,640 --> 00:31:15,940 And that's why most of us were perfectly happy with the idea that there was only one universe. 279 00:31:15,940 --> 00:31:20,100 And then this guy comes up with your pictures and all that, and other people you'll meet. 280 00:31:20,100 --> 00:31:25,120 Very very smart people, I must say, will sit on this stage, who believe that there is not one, 281 00:31:25,120 --> 00:31:30,220 but, as you have heard, many universes, and therefore their universe is multiplied, 282 00:31:30,220 --> 00:31:34,380 which is a bit strange, isn't it. 283 00:31:34,380 --> 00:31:46,380 And even more meaningless, these people insist, or suggest, or skillfully describe, many, many, many, many, perhaps infinitely many universes. 284 00:31:46,380 --> 00:31:52,800 And they don't mean the idea in their head or the mathematical equation or abstraction or logic ... 285 00:31:52,800 --> 00:32:00,320 No, they say, as you saw recently, it's real, we suggest that there are real physical universes 286 00:32:00,320 --> 00:32:04,480 with energy and matter and maybe atoms and stars and gases and you know - real things 287 00:32:04,480 --> 00:32:10,580 who are really out there in the vast, perhaps infinite multitude, and collectively call them the multiverse. 288 00:32:10,580 --> 00:32:12,580 That's the theme tonight. 289 00:32:12,580 --> 00:32:17,620 But instead of insisting that this is true, I will reset here, because ... 290 00:32:18,120 --> 00:32:19,500 You will see. 291 00:32:19,500 --> 00:32:24,180 The first thing you need to know is that not everyone agrees. 292 00:32:24,180 --> 00:32:28,780 Nobel Prize winner, physicist from the University of California, Santa Barbara, a highly respected man 293 00:32:28,780 --> 00:32:33,980 he thinks it is, and these are his words: "An inelegant, unprovable and unlikely idea." 294 00:32:33,980 --> 00:32:38,820 And there is a man, perhaps reading about him in Scientifique Ameriken, the mathematician Martin Gardener 295 00:32:38,820 --> 00:32:42,560 calling her "a frivolous fantasy, intellectually bankrupt." 296 00:32:42,560 --> 00:32:48,280 Paul Steinhart, mentioned by Brian, Professor Albert Einstein at Princeton, says: 297 00:32:48,280 --> 00:32:53,400 "This is a dangerous idea that I simply don't have the will to take into consideration." 298 00:32:53,400 --> 00:32:59,340 So what we are going to talk about tonight is not a general agreement object, it is even very debatable. 299 00:32:59,340 --> 00:33:04,780 But because it's a very rich, important, and I must admit, very intriguing idea, 300 00:33:04,780 --> 00:33:12,260 we have fitted the cards by bringing the pluralists of the universe, we call them "i-people" because the word universe is spelled with -i. 301 00:33:12,260 --> 00:33:18,460 I must admit immediately that I am not a scientist, nor am I particularly taught in these matters. 302 00:33:18,460 --> 00:33:24,600 I am here to support many of you who will be asking "What?" if they don't understand some of it 303 00:33:24,600 --> 00:33:30,160 because it is my job to tell these people: What does that mean? What are you talking about? How do you know that? Why do you say that? 304 00:33:30,160 --> 00:33:36,820 This is a science festival not for scientists but for curious people who want to spend an hour or two on spring evenings wondering: 305 00:33:36,820 --> 00:33:43,440 What is and what can be learned about our universe, or our universes? 306 00:33:44,520 --> 00:33:48,980 We'll get to the point. I sit in the most extreme place. 307 00:33:50,280 --> 00:33:53,140 And elsewhere there will be: 308 00:33:53,200 --> 00:33:58,440 Nick Bostrom who is ... I guess it's best for them to go out in the crowd. 309 00:33:58,440 --> 00:34:02,280 They will smile, as Brian predicted. 310 00:34:05,200 --> 00:34:08,820 I don't know, they'll show up already, and I'll tell you who they are. 311 00:34:08,820 --> 00:34:12,080 And here they are! Hi Hello. 312 00:34:25,900 --> 00:34:31,140 This is Nick Bostrom. He is a philosopher who thinks that there may not just be multiple universes, 313 00:34:31,140 --> 00:34:35,900 but many of them can be computer simulations, so everything you see around you right now, 314 00:34:35,900 --> 00:34:42,660 touch your foot if you like, feel the material and texture. That's not really ... 315 00:34:42,660 --> 00:34:47,760 Nick Bostrom is also the director of Oxford University's Institute for the Future of Humanity 316 00:34:47,760 --> 00:34:50,740 what you need to worry about. 317 00:34:50,740 --> 00:34:56,940 Alan Gut is a professor of physics at the Massachusetts Institute of Technology (MIT), world-renowned for his theory of inflationary cosmology. 318 00:34:56,940 --> 00:35:06,600 The story we tell about the universe has changed, in large part, because of the things he discovered and thinks. 319 00:35:06,600 --> 00:35:15,180 Then Brian. Brian is a professor of physics and mathematics at Columbia University. Author of "The Fabric of the Cosmos" and "The Elegant Universe." 320 00:35:15,180 --> 00:35:19,640 He has made important discoveries in his field, and that is the theory of superstring. 321 00:35:19,640 --> 00:35:26,840 And his skill in explaining insanely complicated things like this irritates me, but so many love him. 322 00:35:26,840 --> 00:35:37,260 And Andrew Lind is a cosmologist and professor of physics at Stanford, who believes that the universe is infinitely and eternally multiplying in more and more and more universes. 323 00:35:37,260 --> 00:35:40,860 If you want to blame someone for this, blame him. 324 00:35:41,000 --> 00:35:45,940 Let's start by going back to a few places from Brian's story. 325 00:35:46,440 --> 00:35:51,540 Big Bang: I want us to go back to that. 326 00:35:51,960 --> 00:36:00,500 You said, and I was intrigued, that you could find evidence of microwave radiation and all that. 327 00:36:02,360 --> 00:36:09,660 You also said that the universe is expanding. How do we know then ... if you can describe what happened there. 328 00:36:11,880 --> 00:36:16,200 Why do they call it the Big Bang? 329 00:36:16,200 --> 00:36:23,560 - It was actually a derogatory term. Correct me, but I think Fred Hoyle was the one who didn't believe in that way of thinking. 330 00:36:23,580 --> 00:36:28,900 I think in a radio interview he said, "These guys are constantly talking about some big bang!" 331 00:36:29,020 --> 00:36:34,860 The idea is simply that if you think of something small as it increases and try to compare it to something you see in the world around you, 332 00:36:34,860 --> 00:36:39,880 when things explode, they increase, so it's like a cosmic explosion. 333 00:36:39,880 --> 00:36:50,340 But that kind of thinking is actually cumbersome, because it sounds almost as if there was a universe around where that burst happened 334 00:36:50,340 --> 00:36:57,340 and that's not the typical way we think about it, though when we start to think of the multiverse, it gets a little hazier. 335 00:36:57,340 --> 00:37:00,120 But let's forget about the multiverse for a second and start simple. 336 00:37:00,120 --> 00:37:05,740 Traditional Big Bang theory predicts that everything is in that small lump that started it all. 337 00:37:05,740 --> 00:37:07,700 There is no space outside. 338 00:37:07,700 --> 00:37:11,480 And as it grows, it creates the space that is around us. 339 00:37:11,480 --> 00:37:16,780 - And since space and time, Einstein says, are the same thing, if I ask you, as many would ask 340 00:37:16,780 --> 00:37:21,420 what happened just before the Big Bang, how would he respond? 341 00:37:22,680 --> 00:37:28,400 - There are a lot of issues in cosmology that are very tricky. And that is certainly one of them. 342 00:37:28,400 --> 00:37:31,200 And there is no single answer to it. 343 00:37:31,200 --> 00:37:36,100 When you go to the multiverse image, the question changes. But let's start again from the simple. 344 00:37:36,100 --> 00:37:41,760 In the traditional Big Bang, one way of thinking is that there was no time before the Big Bang 345 00:37:41,760 --> 00:37:47,100 because space and time started their existence with this event. 346 00:37:47,100 --> 00:37:51,380 It's like asking you how to go north of the North Pole. 347 00:37:51,380 --> 00:37:56,840 That question means nothing, does it? Because the north ends there and it starts there. 348 00:37:56,840 --> 00:38:02,500 And so if you ask me what came before the Big Bang, I say, "That question has no meaning." 349 00:38:02,500 --> 00:38:09,080 Admittedly, there are other approaches to this topic and we'll talk about them tonight, where the Big Bang is an interesting event, 350 00:38:09,080 --> 00:38:14,620 but it is not the only creation event, and it is possible that there were events before it. 351 00:38:14,620 --> 00:38:21,300 - Do you all just bypass the issue of events before the Big Bang and move on? 352 00:38:21,300 --> 00:38:27,280 In fact, there is one part from the Calvin and Hobbes comic about this, where Calvin tells Hobbes, 353 00:38:27,280 --> 00:38:32,140 otherwise these are comic book characters, as you know, about a boy and his tiger doll, 354 00:38:32,140 --> 00:38:37,780 and the boy says to his tiger, "Why did they come up with such a name?" Do we have a picture ...? 355 00:38:42,200 --> 00:38:46,080 On the right you will see an alternative name: 356 00:38:46,080 --> 00:38:50,720 A HORRIBLE SPACE KA-BOOM! 357 00:38:51,020 --> 00:38:55,140 Maybe that would be a better name ... But let's move on. 358 00:38:57,680 --> 00:39:08,080 In the beginning, when we have that moment in the beginning, we have a thick soup of things, very hot, and then ... 359 00:39:08,180 --> 00:39:12,240 Alan, I want to ask you, there are problems. 360 00:39:12,240 --> 00:39:19,060 That hot soupy thing that is at the very beginning of time then becomes lumpy 361 00:39:19,060 --> 00:39:23,000 and then it crosses into clouds and galaxies and as Brian's film has shown. 362 00:39:23,000 --> 00:39:30,280 The universe then expands outward but does not turn into a circle, so it seems to turn into some kind of plane to expand. 363 00:39:30,280 --> 00:39:37,020 And if you look around in all directions, like those radio people did, it looks the same wherever you look. 364 00:39:37,020 --> 00:39:45,000 How did you Alan explain the universe's early initial flattery, lumpiness and uniformity 365 00:39:45,000 --> 00:39:53,040 and why did you write in your lab notebook "This idea I just had is a spectacular moment of comprehension"? 366 00:39:53,660 --> 00:39:59,940 - It happened one night when I put together a few things I've been working on for the past six months, 367 00:39:59,940 --> 00:40:06,120 but the key idea is the idea of ​​inflation, inflation, which really ended in one night. 368 00:40:06,120 --> 00:40:08,120 And I realized ... 369 00:40:08,620 --> 00:40:10,440 - In one night? 370 00:40:10,440 --> 00:40:14,200 - One night I put together what was six months of prelude. 371 00:40:14,200 --> 00:40:19,360 I was lucky that a lot of important information fell into my lap during that period. 372 00:40:19,360 --> 00:40:25,260 I was lucky in that knowledge, but I think someone else would have found out sooner. 373 00:40:25,260 --> 00:40:32,900 But the key idea was that I was observing a phase transition that we thought happened in the early universe, 374 00:40:32,900 --> 00:40:39,920 and I considered the idea that the phase transition might have been subjected to a significant amount of supercooling, 375 00:40:39,920 --> 00:40:44,760 motivated by studying something called magnetic monopolies, but I won't go into it now. 376 00:40:44,760 --> 00:40:50,800 - Don't! - No I will not. I never intended. 377 00:40:50,800 --> 00:40:58,600 Anyway, going through some calculations, I realized that supercooling would produce that particular field 378 00:40:58,600 --> 00:41:03,960 which Brian had just targeted, which would have a repulsive gravitational effect. 379 00:41:03,960 --> 00:41:08,500 And that would have huge consequences on the expansive history of the universe. 380 00:41:08,500 --> 00:41:15,640 - Huge consequences? If the universe is extremely tiny, like a proton, 381 00:41:15,640 --> 00:41:19,740 how much did it grow and in what time? 382 00:41:19,740 --> 00:41:28,100 - The weather we're talking about here - we still don't know exactly, but the time we talked about back then still seems convincing, 383 00:41:28,100 --> 00:41:33,000 is 10 at -35 seconds or so silly. 384 00:41:33,060 --> 00:41:35,520 - So much faster than PK! 385 00:41:35,520 --> 00:41:40,280 - Much faster than that. You can't do that. You can try, but you will not succeed. 386 00:41:40,280 --> 00:41:43,040 - I won't even try. 387 00:41:43,040 --> 00:41:48,420 - And during that time the expansion climbed by a factor of 10 to 25 or something. 388 00:41:48,420 --> 00:41:49,940 - So 10 with 25 zeros. 389 00:41:49,940 --> 00:41:51,700 - One with 25 zeros. 390 00:41:51,700 --> 00:41:54,080 - What size is it then? 391 00:41:54,080 --> 00:42:02,620 - Starts at a size more than a billion times smaller than a proton, eventually increasing to about the size of a clicker. 392 00:42:02,620 --> 00:42:04,380 Still very small. 393 00:42:04,380 --> 00:42:05,500 - Clicker? 394 00:42:05,500 --> 00:42:10,060 - Clicker. The whole universe - this way. 395 00:42:10,060 --> 00:42:12,060 - That's mysterious! 396 00:42:12,060 --> 00:42:16,880 - He continued to expand after that, but not to accelerate. It's just an expansion. 397 00:42:16,880 --> 00:42:20,860 - Why it's repulsive PFF! care about? 398 00:42:20,860 --> 00:42:27,320 - It stopped because that thing that pushed him, that field, was unstable. 399 00:42:27,320 --> 00:42:33,160 As radioactive substances, it decomposes into other types of materials, which we consider more normal 400 00:42:33,160 --> 00:42:35,740 and which produce attractive gravity. 401 00:42:35,740 --> 00:42:43,500 - So the opposite of gravity is that the elbow is "bent" instead of being "approached" by a kind of force, 402 00:42:43,500 --> 00:42:52,180 if this repulsive thing creates a table tennis ball-sized universe, 403 00:42:52,180 --> 00:42:55,240 then how does it solve the problems I just mentioned? 404 00:42:55,240 --> 00:43:00,060 How does it make the universe seem flat in order to expand? 405 00:43:00,060 --> 00:43:04,600 How does it create the possibility of lumpy matter so that there are stars? 406 00:43:04,600 --> 00:43:07,820 How does this create the impression of universal uniformity? 407 00:43:07,820 --> 00:43:14,340 - I'll start with the problem in the opposite order. Let's start with uniformity, it's the easiest to understand. 408 00:43:14,340 --> 00:43:17,840 In conventional cosmology, as it existed before inflation was added, 409 00:43:17,840 --> 00:43:25,340 the whole universe was expanding so fast that there was not enough time for the various parts to communicate with each other 410 00:43:25,340 --> 00:43:28,640 even if they could send each other signals at the speed of light. 411 00:43:28,640 --> 00:43:32,920 Therefore, it was concluded that the universe could have started as perfectly uniform, 412 00:43:32,920 --> 00:43:35,640 we don't know exactly how the universe started, 413 00:43:35,640 --> 00:43:43,060 but unless it emerged as perfectly uniform, there was never enough time in conventional cosmology to unify it. 414 00:43:43,060 --> 00:43:46,580 So it stayed lumpy, it started out as lumpy. 415 00:43:46,580 --> 00:43:57,120 In fact, the early universe was very smooth. Nonuniformity is crucially important, but it was only one part in 100,000. 416 00:43:57,120 --> 00:43:59,260 The early universe was simply slick. 417 00:43:59,260 --> 00:44:06,480 Inflation can explain this. Because with that PFF bump! expansion, that means it’s before PFF! rush, 418 00:44:06,480 --> 00:44:11,960 the birth universe was drastically smaller than it would have been under any previous theory. 419 00:44:11,960 --> 00:44:17,180 And while he was drastically smaller, he had plenty of time to get uniformed 420 00:44:17,180 --> 00:44:24,120 in the same way that the air in the room equalizes so we do not have high and low pressure pockets. 421 00:44:24,120 --> 00:44:29,220 But it takes some time for that to happen. And there was enough time on such a small scale. 422 00:44:29,220 --> 00:44:37,440 Then this tiny speck, more than a billion times smaller than protons, believe it or not, we talk about such things and think we believe in them, 423 00:44:37,440 --> 00:44:43,380 it expanded, stretched from inflation itself and increased enough to become a clicker 424 00:44:43,380 --> 00:44:47,540 which then grows enough to include literally everything we see today. 425 00:44:47,540 --> 00:44:54,760 - That the clicker becomes literally everything we see today - is it because there is so much energy in that clicker, 426 00:44:54,760 --> 00:44:59,420 I mean, the energy gradually cools down to become matter, and then you get more space and more time, 427 00:44:59,440 --> 00:45:02,240 and more space and more time ... and then to us. 428 00:45:02,240 --> 00:45:06,000 - That's right. That later part after just sails. 429 00:45:06,000 --> 00:45:10,300 - Then do you solve the problem of clotting in the same way? 430 00:45:10,300 --> 00:45:16,540 - That's a serious problem. The clot problem comes from the smallest quantum fluctuations, 431 00:45:16,540 --> 00:45:22,340 even in this room, we think if we measured things the size of an atom, we would see large fluctuations 432 00:45:22,340 --> 00:45:26,040 in electric, magnetic field, energy, density - everything. 433 00:45:26,040 --> 00:45:34,640 And inflation takes small-scale fluctuations and stretches them. They grow large enough to become the galaxies we see today. 434 00:45:34,640 --> 00:45:40,020 - So tiny groups become galaxies or huge galaxy fields. 435 00:45:40,020 --> 00:45:41,360 - That's right. 436 00:45:41,480 --> 00:45:43,940 - What was the third problem? 437 00:45:44,020 --> 00:45:47,880 - It's flatness. Flatness is a little harder to understand. 438 00:45:47,880 --> 00:45:52,260 We don't know what shape the universe was when it started. 439 00:45:52,260 --> 00:45:58,660 But the picture that is easy to imagine and that can be true is that the universe began as a circular, 440 00:45:58,660 --> 00:46:07,540 what we call a closed universe, which is a three-dimensional analog of the sphere, of what I illustrate with my hands. 441 00:46:07,540 --> 00:46:10,240 - Yeah, you're doing it right. 442 00:46:10,240 --> 00:46:15,200 It is a two-dimensional surface but in a three-dimensional space. 443 00:46:15,200 --> 00:46:23,580 So, the universe started out as such, and then inflation made it drastically higher and in the end looks flat 444 00:46:23,580 --> 00:46:28,400 for the same reason that the Earth's surface acts flat on us, even though the Earth is actually circular. 445 00:46:28,400 --> 00:46:33,280 If you take something that is round and stretch it drastically, it will work straight. 446 00:46:33,280 --> 00:46:38,160 - Andrew, let's move on to the next step. So we have this thing that grows into a bigger thing. 447 00:46:38,160 --> 00:46:43,680 This clarifies some early problems and makes the universe seem a little more familiar to us. 448 00:46:43,680 --> 00:46:47,920 But my next question is called the graceful exit problem. 449 00:46:47,920 --> 00:46:53,460 This indecent form of upside-down gravity pushes itself away. 450 00:46:53,460 --> 00:46:57,680 You said that the universe somehow stopped growing. 451 00:46:57,680 --> 00:47:02,480 But it doesn't seem to stop growing on some kind of tralala-TRAS! the way. 452 00:47:02,480 --> 00:47:06,440 It just keeps disturbing the universe. 453 00:47:06,440 --> 00:47:14,720 And from that flux of repulsive gravity a more interesting question arises. Andrej, the question is for you: 454 00:47:14,720 --> 00:47:24,100 How does one get from one universe to more than one universe if you continue from where Alan left off. 455 00:47:24,100 --> 00:47:27,900 - First, let's try to understand how to get one. 456 00:47:27,900 --> 00:47:35,900 Because Alan suggested the idea of ​​making the universe big, everything in it, etc. 457 00:47:35,900 --> 00:47:44,260 But when the bubbles in his universe ... when the universe starts to vacuum, the energy states start to fall apart, 458 00:47:44,260 --> 00:47:48,100 it produces bubbles, which then collide ... 459 00:47:48,100 --> 00:47:53,000 - Wait. So there is energy. And she pushes everyone outside. 460 00:47:53,000 --> 00:47:59,880 And in Brian's film, energy seems to sigh occasionally. 461 00:47:59,880 --> 00:48:05,380 So the energy level is down, but not up, here and then ... 462 00:48:05,380 --> 00:48:10,280 And every time this repulsive energy makes sense or gives up some space, is that where the universe gets? 463 00:48:10,280 --> 00:48:15,140 - Yes, well, that's how you get the interior of the universe. 464 00:48:15,140 --> 00:48:22,140 You see, in Alan's picture you have a universe similar to Swiss cheese, and bubbles are created which then collide. 465 00:48:22,140 --> 00:48:29,680 Even after they collide, they may somehow disappear, but the universe after that, unfortunately, became inhomogeneous. 466 00:48:29,680 --> 00:48:34,180 And then I had my own night as Alan's, 467 00:48:34,180 --> 00:48:41,080 except it was the night I brought my phone to the toilet 468 00:48:41,080 --> 00:48:47,380 because it was the only place in the house where I would not wake my son. 469 00:48:47,380 --> 00:48:53,540 I called some colleagues and told them I had an idea and asked them if it was stupid. 470 00:48:53,540 --> 00:49:00,240 - Wait, so you got your inspiration, rushed to the toilet, hid your phone? 471 00:49:01,080 --> 00:49:03,080 This is a good story! 472 00:49:03,080 --> 00:49:11,200 - I got my inspiration a little earlier. But it is important that I did not lose it after I went to the toilet. 473 00:49:11,200 --> 00:49:17,020 And I went to the toilet not for the reasons you doubt me, 474 00:49:17,020 --> 00:49:23,880 but because I had to call a colleague to check if I was thinking stupid or not. 475 00:49:23,880 --> 00:49:29,940 And he said he didn't think it was stupid. And then I woke up one- 476 00:49:29,940 --> 00:49:36,240 - Check check. Did you have to say something mathematical or did you say, "I'll tell you something, and you'll think I'm crazy." 477 00:49:36,240 --> 00:49:42,140 - It was pretty mathematical. As much as he can over the phone. 478 00:49:46,020 --> 00:49:54,800 Eventually I woke up and said to the woman, "Look, I think I know how the universe was created." 479 00:49:58,860 --> 00:50:02,520 - It was a big trip to the bathroom! 480 00:50:04,080 --> 00:50:08,600 - I guess we'll all try the same a little later. 481 00:50:10,180 --> 00:50:13,960 But maybe not so successfully this time ... 482 00:50:15,260 --> 00:50:18,840 So the idea was this: you have many bubbles. 483 00:50:18,840 --> 00:50:24,740 But then the blisters can begin to expand continuously internally. 484 00:50:24,740 --> 00:50:35,980 And when the energy goes down, they keep expanding. And the result is that you don’t see all the pieces. 485 00:50:35,980 --> 00:50:41,140 You don't see the opposite walls of the bubble colliding with each other. 486 00:50:41,140 --> 00:50:45,960 Because the interior has grown so much that you don't see disaster. 487 00:50:45,960 --> 00:50:49,760 You only get the benefits of expanding the inner part. 488 00:50:49,760 --> 00:50:58,460 So you get a smooth end to inflation, that slow rolling, inside one bubble. 489 00:51:00,520 --> 00:51:05,420 - Excuse me, I have to translate you into my own language, because it's hard for me to understand. 490 00:51:05,420 --> 00:51:12,300 So in my universe, there is some logic. Things are spreading around me and they seem to be infinitely expanding 491 00:51:12,300 --> 00:51:16,160 and there is some kind of uniformity of creation in my universe. 492 00:51:16,160 --> 00:51:20,580 But if my universe is here and the next universe is there, 493 00:51:20,580 --> 00:51:29,380 the space between us - between my bladder and his bladder - the space between us is increasing rapidly. 494 00:51:29,380 --> 00:51:34,360 So our universes are moving away. Mine is fine, his is fine, 495 00:51:34,360 --> 00:51:38,880 but look! We're moving away. Is that what you want to say? 496 00:51:38,880 --> 00:51:47,500 - This is not a complete story, because if that were the case in the first version of inflationary theory, then your universe would be empty. 497 00:51:47,500 --> 00:51:57,720 So it's not just the case that both of your universes are in order. But because of that smooth decline in energy and the spread of yourself, 498 00:51:57,720 --> 00:52:03,180 not just the distance between your universe and Nick's, but everything that happens around you, 499 00:52:03,180 --> 00:52:06,920 then you are left with a large part of the universe that you can inhabit on your own. 500 00:52:06,920 --> 00:52:14,540 It's like peaceful coexistence. Like when I was in Russia, Alan in the US. Okay, it was a bit of a problem. 501 00:52:14,540 --> 00:52:26,960 But what if Russia and the US are expanding exponentially and not hurting each other at the border, 502 00:52:26,960 --> 00:52:35,680 already expanding from their own resources. That's what we suggest the universe does - expand peacefully, without collision. 503 00:52:35,680 --> 00:52:46,500 - I still don't understand how you start with one universe and then you get another, then another, and another. 504 00:52:46,500 --> 00:52:49,280 Some logic is missing here. 505 00:52:49,280 --> 00:53:00,140 - Maybe I'd better show you. We'll come back to this picture later, but can we see the golden universe? 506 00:53:02,420 --> 00:53:10,160 These are computer simulations. Because when you want high-tech cheating, turn to computers. 507 00:53:10,160 --> 00:53:17,000 On the left is the X-axis, across is the Y-axis. And this is a laser weapon. 508 00:53:17,000 --> 00:53:24,980 And the longitudinal axis shows the energy density level in the universe, 509 00:53:24,980 --> 00:53:31,860 or the value or size of the field - whatever you call it. This is what is responsible for the expansion of the universe. 510 00:53:31,860 --> 00:53:35,620 The higher the spike, the faster the universe expands. 511 00:53:35,620 --> 00:53:39,560 We started the simulation with an almost homogeneous universe, 512 00:53:39,560 --> 00:53:42,760 and then he began to expand at an exponential rate. 513 00:53:42,760 --> 00:53:50,920 A computer cannot expand at an exponential rate, and therefore every new frame displays an exponentially larger part of the universe, 514 00:53:50,920 --> 00:53:53,100 but the computer shrinks it again. 515 00:53:53,100 --> 00:54:00,920 Then these little waves, you see quantum fluctuations in homogeneity here, they freeze at each other 516 00:54:00,920 --> 00:54:08,160 then the universe continues to expand, then new quantum fluctuations freeze over each other, and the universe continues to expand. 517 00:54:08,160 --> 00:54:14,840 And in some places the energy level goes down on average, 518 00:54:14,840 --> 00:54:21,120 and we live somewhere here in this lower left corner where the fluctuations are small. 519 00:54:21,120 --> 00:54:28,660 And when they're small, we launch satellites, watch what's going on, and get interesting curves 520 00:54:28,660 --> 00:54:32,300 and we come across agreement with experiment data. 521 00:54:32,300 --> 00:54:39,480 But there are also parts where these fluctuations accumulate with each new leap, grow and grow 522 00:54:39,480 --> 00:54:47,100 and they use other parts of the universe that are so dense that they expand much faster than the original part of the universe. 523 00:54:47,100 --> 00:54:50,900 And this is where new parts of the universe are created. 524 00:54:50,900 --> 00:54:57,160 So it started from the smallest part of the space, and then, according to the classical theory we all love, it went down 525 00:54:57,160 --> 00:55:03,240 and it could all end there, but due to quantum fluctuations in some regions 526 00:55:03,240 --> 00:55:05,700 the spread continues forever. 527 00:55:05,700 --> 00:55:13,300 By the way, this part that shows low fluctuations is the part that has been experimentally tested 528 00:55:13,320 --> 00:55:16,020 and which will be experimentally tested. 529 00:55:16,020 --> 00:55:20,900 Can we see a movie with Plank's satellite? 530 00:55:20,900 --> 00:55:27,560 This movie shows the recent launch of Planck's satellite, May 14, 2009, 531 00:55:27,560 --> 00:55:38,080 which will generate data in about three years, and will show these little colored dots in the sky 532 00:55:38,080 --> 00:55:43,420 which are the result of small, small scale fluctuations. 533 00:55:43,420 --> 00:55:53,340 And after he finishes and maps all this and, hopefully, agrees with the theory we currently have, 534 00:55:53,340 --> 00:55:58,760 we'll get pictures like the one I want to show you now 535 00:55:58,760 --> 00:56:01,700 and that is the universe of color. 536 00:56:01,700 --> 00:56:11,480 This is a universe similar to the first image with X and Y axes. And here is the density (along), but in different colors. 537 00:56:11,480 --> 00:56:18,720 Different colors indicate that in some parts of the universe there is a space with some kind of properties, 538 00:56:18,720 --> 00:56:20,720 let's call them red, 539 00:56:20,720 --> 00:56:25,280 and in other parts there are different qualities which we shall call green. 540 00:56:25,280 --> 00:56:31,460 And for historical reasons, being from Russia, I started the simulation with a red square. 541 00:56:31,460 --> 00:56:41,000 And as you can see, it all ends with a universe that is multifaceted. But what does that mean? 542 00:56:41,000 --> 00:56:50,280 Let's get some water. So the water can be in solid form, liquid or gaseous. 543 00:56:50,280 --> 00:56:57,700 It's the same water, with the same chemistry and physics in it. This can also be applied to theory. 544 00:56:57,700 --> 00:57:03,780 You can have one fundamental theory for everything, but it can represent different parts of the universe 545 00:57:03,780 --> 00:57:06,160 which have different properties. 546 00:57:06,160 --> 00:57:11,560 You can still have the red universe, or green here, blue here. 547 00:57:11,560 --> 00:57:19,680 But because of the exponential expansion of the universe, the distance between red and blue will be exponentially large. 548 00:57:19,680 --> 00:57:26,620 And if you decide to cross the border, simply start moving from the red universe to the blue. 549 00:57:26,620 --> 00:57:33,500 But you will come to the border, like a wall. A cop is not necessary as it is very very difficult to cross. 550 00:57:33,500 --> 00:57:41,420 But if you are stupid enough, young and brave, and cross the border, you will most likely die instantly. Because... 551 00:57:41,420 --> 00:57:43,680 - Just a moment! 552 00:57:43,680 --> 00:57:47,800 I do not want you to die here in your presentation! 553 00:57:50,380 --> 00:57:55,420 Can I interrupt you for a moment? It looks like we have a carnival in this picture ... 554 00:57:55,420 --> 00:58:01,180 All of us in this panel discussion are very talented, but I would say that you went one chapter further than I would like at this point. 555 00:58:01,180 --> 00:58:05,900 But you Brian have one picture like this, don't you? I don't know if you brought it. 556 00:58:07,260 --> 00:58:12,480 I need a different version of building a universe. Do you have one? 557 00:58:12,480 --> 00:58:21,520 - Do not have. This picture you see is the more scientific version of the visualization I presented at the end of my introduction. 558 00:58:21,520 --> 00:58:26,200 Where each of these colors is actually a separate universe, a separate bubble 559 00:58:26,200 --> 00:58:31,140 in that huge, growing base that holds all the bubbles. 560 00:58:31,140 --> 00:58:39,720 This is a more technical way of pointing out that there can be many different types of universes within different bubbles. 561 00:58:39,720 --> 00:58:43,600 - But I want to go back to the basic idea. 562 00:58:43,600 --> 00:58:50,000 The basic idea is that there is some hesitant, fluctuating thing at the bottom of existence. 563 00:58:50,000 --> 00:58:58,220 And the fluctuating thing is either a robust "get off me!" Or a relaxed, smaller version of it. 564 00:58:58,220 --> 00:59:05,500 And then in some places, robustness breaks out and creates separation of the universe. 565 00:59:05,500 --> 00:59:10,620 You get a lot of distance as the universes move very fast from one another. 566 00:59:10,620 --> 00:59:16,680 And then the universes themselves jump out of this carrying repulsive energy that is always there, 567 00:59:16,680 --> 00:59:21,120 sometimes more, sometimes less, sometimes up, sometimes down ... Is that a general idea? 568 00:59:21,120 --> 00:59:24,680 Do you know how strange and strange this is? 569 00:59:24,680 --> 00:59:28,280 I mean, couldn't you think of something simpler? 570 00:59:28,280 --> 00:59:33,720 - I think it is important to keep in mind that these ideas, when communicated in ordinary language 571 00:59:33,720 --> 00:59:37,440 they really sound complicated and weird, they are unknown. 572 00:59:37,440 --> 00:59:43,900 But if you look at the math behind the versions of these theories that these two gentlemen came up with, 573 00:59:43,900 --> 00:59:49,280 it is actually the simplest mathematics encountered in many physics theories of this kind. 574 00:59:49,280 --> 00:59:53,100 She is really very direct, and really implies. When you look at math, 575 00:59:53,100 --> 00:59:59,300 then really, if these theories are true that we lie in a huge expanding substrate, 576 00:59:59,300 --> 01:00:04,840 and that these openings can happen in what we consider to be a unique universe, which it really is 577 01:00:04,840 --> 01:00:08,880 one opening out of the many possible openings in that huge growing base. 578 01:00:08,880 --> 01:00:11,840 And the features can vary from opening to opening. 579 01:00:11,840 --> 01:00:17,220 - So every universe is one side of that flow, the flux, 580 01:00:17,220 --> 01:00:21,060 and everything in between is a robust separation. 581 01:00:21,100 --> 01:00:25,720 Doesn't that mean that the universe ... Between Nick's universe and my universe 582 01:00:25,720 --> 01:00:29,400 is the distance between us increasing? And is it growing fast? 583 01:00:29,400 --> 01:00:31,260 - Very fast! 584 01:00:31,260 --> 01:00:36,600 - So the universes, his universe and mine, are moving at a speed greater than the speed of light? 585 01:00:36,600 --> 01:00:39,880 - If they were far enough away, they would be faster than the speed of light, yes. 586 01:00:39,880 --> 01:00:42,840 - I thought nothing could move faster than light. 587 01:00:42,840 --> 01:00:46,240 - Einstein told us that nothing can move through space faster than the speed of light. 588 01:00:46,240 --> 01:00:51,600 He said nothing about bodies being pulled away from one another by the expansion of space itself. 589 01:00:51,600 --> 01:00:56,680 So if they are sufficiently far from each other and the space between them expands, then they will move one relative to the other 590 01:00:56,680 --> 01:00:59,280 be in some sense faster than the speed of light. 591 01:00:59,280 --> 01:01:04,600 Which means it will be permanently beyond your ability to talk, communicate with them. 592 01:01:04,600 --> 01:01:09,840 So they are out there somewhere, but permanently beyond your ability to see them or to see you. 593 01:01:09,840 --> 01:01:16,660 - Before we get to that ... You just magnified what I used to call the universe, 594 01:01:16,660 --> 01:01:23,120 you just magnified it enormously. You doubled the speed ... That's ... Uh. 595 01:01:23,120 --> 01:01:28,240 - When these two appeared on the scene, the picture of the vastness of the universe changed dramatically. 596 01:01:28,240 --> 01:01:32,200 It used to be: the universe is 14 billion years old, roughly the transverse distance was 597 01:01:32,200 --> 01:01:35,560 14 billion light-years, more or less, if you insert a factor of three here and there. 598 01:01:35,560 --> 01:01:38,860 But these guys increased it by a factor of about ten to one hundred. 599 01:01:38,860 --> 01:01:40,860 - Or infinite. - Yes, or infinite! 600 01:01:40,860 --> 01:01:46,480 - It should be added that this is not an accurate ... more precisely, the complete picture we are talking about. 601 01:01:46,480 --> 01:01:49,140 Sometimes universes can collide with one another. 602 01:01:49,140 --> 01:01:51,140 - Please, sometimes I can do what? 603 01:01:51,140 --> 01:01:59,840 - Sometimes the main wall comes towards you and hits you, but you don't see it because it moves at a speed approaching the speed of light. 604 01:01:59,840 --> 01:02:05,980 But the moment he collides with you, you stop seeing him, and then ... There you go. 605 01:02:05,980 --> 01:02:07,980 - Andrew, can I just ... 606 01:02:07,980 --> 01:02:09,580 - That's his whole problem! 607 01:02:09,580 --> 01:02:18,000 - Why do you think it will ... You have raised the idea that the universe will go, and go, and go, and go. 608 01:02:18,000 --> 01:02:24,980 So, do you think that there is a beginning of a multiverse, and that it ends? 609 01:02:24,980 --> 01:02:30,840 As in any of these universes, I think you can exhaust yourself and die, and the universe would collapse. 610 01:02:30,840 --> 01:02:31,940 - Yes. 611 01:02:31,940 --> 01:02:37,140 - But it doesn't look like this big thing can collapse. 612 01:02:37,140 --> 01:02:40,500 So, is that what you suggest the eternal universe? 613 01:02:40,500 --> 01:02:45,260 - If we can see the image of that bubble universe again? 614 01:02:45,260 --> 01:02:50,720 As for the beginning, as Alan and several other people have shown, 615 01:02:50,720 --> 01:02:55,760 we still need this bubble below that can't be seen well from the chairs, 616 01:02:55,760 --> 01:03:02,680 this first bubble that appears below. The problem must be something that triggered the tree to grow. 617 01:03:02,680 --> 01:03:07,920 Perhaps, however, growth has not begun simultaneously in the entire universe. 618 01:03:07,920 --> 01:03:13,440 What happens is that once this process of production begins, even more new universes, 619 01:03:13,440 --> 01:03:17,700 the process never ends. So the universe is infinite in the future. 620 01:03:17,700 --> 01:03:22,580 And what does that mean for us? Well, a few things. E.g: 621 01:03:22,580 --> 01:03:28,280 We used to think that this bubble is partially visible from the chairs, 622 01:03:28,280 --> 01:03:30,280 that first bubble is the whole story. 623 01:03:30,280 --> 01:03:33,580 What we and cosmology wanted to explain was: 624 01:03:33,580 --> 01:03:39,460 We see this universe around us, and it is more or less homogeneous, more or less uniform in all directions. 625 01:03:39,460 --> 01:03:45,540 In fact, Albert Einstein believed that the universe must be uniform and homogeneous. 626 01:03:45,540 --> 01:03:50,200 He and some have called it the cosmological principle. 627 01:03:50,200 --> 01:03:56,720 We continue to see this in books on astrophysics. A perfect cosmological principle means 628 01:03:56,720 --> 01:04:03,020 that the universe must be uniform. Even if this is a yellow balloon below - it is a yellow balloon. 629 01:04:03,020 --> 01:04:09,180 I used to joke that people who don't have good ideas have principles. 630 01:04:11,420 --> 01:04:18,180 But I stopped that joke after learning that this cosmological principle was set by Einstein. 631 01:04:20,260 --> 01:04:25,880 Here's what happens: The Greeks had the idea of ​​the universe as a perfect sphere. 632 01:04:25,880 --> 01:04:31,480 We wanted to have a mechanism that made our universe a perfect sphere. 633 01:04:31,480 --> 01:04:39,360 And then inflation came on the scene, and she explained why our universe locally looks like the perfect sphere. 634 01:04:39,360 --> 01:04:45,280 But inflation has claimed that the universe looks fractal globally. 635 01:04:45,280 --> 01:04:47,880 Eternally growing fractal. 636 01:04:47,880 --> 01:04:51,960 So the guiding idea was the perfect sphere for the Greeks. 637 01:04:51,960 --> 01:04:56,140 The concept of beauty in the twentieth century is fractal. 638 01:04:56,140 --> 01:05:01,420 And that is exactly what inflation theory has brought about - the multiverse as a fractal. 639 01:05:01,420 --> 01:05:05,160 And fractal gives all possible colors ... 640 01:05:05,160 --> 01:05:07,160 - But why won't it stop? 641 01:05:07,160 --> 01:05:12,460 - Can not. If it continues to grow, producing more and more as ... 642 01:05:12,460 --> 01:05:15,380 - But is it because ... Why? 643 01:05:15,380 --> 01:05:20,600 - I'll try to show a little better. One way you can look at it is 644 01:05:20,600 --> 01:05:26,700 that, as we said, when we have that energy whose level falls, then that part is not subject to inflation. 645 01:05:26,700 --> 01:05:33,540 But we have two opposing effects - one whose energy drops and one where it does not happen, and that part continues to grow. 646 01:05:33,540 --> 01:05:39,100 So we have a growing effect, more and more of those things that are pushing outside that are being created at all times 647 01:05:39,100 --> 01:05:44,040 and only parts of it experience a decline in energy. So somewhere the energy drops and some parts increase 648 01:05:44,040 --> 01:05:48,240 and the number of those that increase is always, in those models, greater than the number of those where energy has fallen. 649 01:05:48,240 --> 01:05:53,140 And that is why you always have a place out there filled with this repulsive thing that is pushing out. 650 01:05:53,140 --> 01:06:02,100 - If I live in this universe, let's just say it's ours and it has our physics 651 01:06:02,100 --> 01:06:08,380 so it has gravity, atoms and forces, and then if I think of this universe, 652 01:06:08,380 --> 01:06:14,320 then does that universe have the same gravity and atoms as ours? Do you know, do you have a theory? 653 01:06:14,320 --> 01:06:18,200 - No, that's why it's blue. 654 01:06:20,380 --> 01:06:21,700 - Ah! 655 01:06:28,340 --> 01:06:31,020 You're an evil man! 656 01:06:32,320 --> 01:06:39,920 So, there are not only many many universes, but many many types of universes? 657 01:06:39,920 --> 01:06:42,880 - Yes. And do you know how much? 658 01:06:42,880 --> 01:06:50,920 Think like this. 1986 or 1987 659 01:06:50,920 --> 01:06:55,140 people who worked on string theory speculated on how many there were 660 01:06:55,140 --> 01:06:59,860 and concluded that there are probably about 10 in the 1000th degree of different universes. 661 01:06:59,860 --> 01:07:01,860 - Different types of universe? 662 01:07:01,860 --> 01:07:13,120 - Yeah, but nobody took them seriously, because they didn't have any guy that probably exists that would be stable. 663 01:07:13,120 --> 01:07:19,940 String theory is based on the idea that our space is essentially ten-dimensional, 664 01:07:19,940 --> 01:07:24,240 and that six of these ten dimensions are squeezed into something very small, 665 01:07:24,240 --> 01:07:28,660 and that there are four large dimensions remaining - three spatial and one temporal. 666 01:07:28,660 --> 01:07:36,220 But no one managed to prevent those six dimensions from expanding. The universe wanted to be ten-dimensional. 667 01:07:36,220 --> 01:07:43,880 And in 2003 it happened that a few people at Stanford, I was a cosmology consultant at the time, 668 01:07:43,880 --> 01:07:51,880 Kachru, Kalosh and Treveli proposed a mechanism for stabilizing these six dimensions. 669 01:07:51,880 --> 01:07:54,860 Can we see the picture? 670 01:07:57,940 --> 01:08:04,700 This is a picture created by a mathematician, and represents how that six-dimensional space looks. 671 01:08:04,700 --> 01:08:11,880 A six-dimensional space is compressed into five dimensions, but can be compressed in so many different ways, 672 01:08:11,880 --> 01:08:17,940 and there are so many different holes, and since there is so much combinatorial freedom, 673 01:08:17,940 --> 01:08:23,080 the total number of ways it can be compressed is exponentially large. 674 01:08:23,080 --> 01:08:29,620 And for each type of this method, there are different characteristics of our universe that live there, 675 01:08:29,620 --> 01:08:36,740 different laws of particle physics, different energy of empty space, different everything. 676 01:08:36,780 --> 01:08:44,660 And when they calculated the number of these stable compacts, they came to number 10 in the 500th degree. 677 01:08:45,700 --> 01:08:48,040 - Ten to five hundred? 678 01:08:48,040 --> 01:08:55,980 - It's a unit with five hundred zeros behind it. Approximately. 679 01:08:55,980 --> 01:08:57,840 - Oh no! 680 01:08:57,900 --> 01:09:00,900 - Plus or minus something. 681 01:09:00,900 --> 01:09:08,500 At some point they started talking about having infinitely many, but then they reduced it to 682 01:09:08,500 --> 01:09:13,060 - Okay, hold on a second. I have to stop breathing when you speak! 683 01:09:13,060 --> 01:09:16,480 Nick, I haven't asked you anything yet. 684 01:09:16,480 --> 01:09:27,600 Is it a little difficult for you to hear the theory of everything that is open to all possibilities? 685 01:09:27,600 --> 01:09:35,100 I mean, wouldn't a theory be a good theory if ... Just a second, I have a text here ... A good theory ... 686 01:09:35,100 --> 01:09:36,860 - It would be good if the text was good. 687 01:09:36,860 --> 01:09:38,860 - I hope so. 688 01:09:39,960 --> 01:09:42,640 I don't remember where he is. 689 01:09:42,640 --> 01:09:45,580 - You see, you still have nothing against her. 690 01:09:45,580 --> 01:09:50,980 - It seems to me that the theory explaining that anything is possible doesn't really explain anything. 691 01:09:50,980 --> 01:09:57,660 Good theory says why something is, but this guy just said, and these others nodded, 692 01:09:57,660 --> 01:10:05,160 that this multiverse contains every thing of a strange shape imaginable, like what we saw just before, 693 01:10:05,160 --> 01:10:07,880 every way of organizing matter imaginable, 694 01:10:07,880 --> 01:10:09,880 any amount of dimensions imaginable, 695 01:10:09,880 --> 01:10:11,880 every possibility imaginable. 696 01:10:11,880 --> 01:10:18,500 But I say, OK, if that's your idea of ​​science, then go to the toilet and think again, because this is not ... 697 01:10:18,500 --> 01:10:20,380 It's too much! 698 01:10:20,380 --> 01:10:23,580 But I'm just interested in your opinion, Nick. 699 01:10:26,400 --> 01:10:31,540 - You get a similar problem when you only have one universe, if it's big enough. 700 01:10:31,540 --> 01:10:36,400 Let's say it's infinite. Then you will have all kinds of observers that exist somewhere, 701 01:10:36,400 --> 01:10:40,020 and all kinds of illusions. 702 01:10:40,020 --> 01:10:46,280 So whatever measurement you make even in that one infinite universe, you have one observer 703 01:10:46,280 --> 01:10:49,660 somewhere, who imagines making that same measurement. 704 01:10:49,660 --> 01:10:55,120 Then the question is how to test the theories if all the theories you compare predict that 705 01:10:55,120 --> 01:11:00,220 for every possible observation you make, there is an observer who makes that same observation. 706 01:11:00,220 --> 01:11:03,960 Theories seem to support every possible observation. 707 01:11:03,960 --> 01:11:11,140 So this is a problem. And the solution must be to consider not just what the theory says 708 01:11:11,140 --> 01:11:14,880 that certain observations will be made, 709 01:11:14,880 --> 01:11:20,480 but what does the theory say about the frequency of making those observations. 710 01:11:20,480 --> 01:11:27,300 So you have to think this way: if there are all possible observer guns 711 01:11:27,300 --> 01:11:31,640 who make all kinds of observations is interesting 712 01:11:31,640 --> 01:11:36,580 what most observers will see in a given type of universe. 713 01:11:36,580 --> 01:11:42,500 So you mean the faction of observers that will make a certain type of observation. 714 01:11:42,500 --> 01:11:45,240 - Can I ask this question in a different way to you, in fact to all of you? 715 01:11:45,240 --> 01:11:51,320 This universe we are in seems to have a very sensitive set of circumstances. 716 01:11:51,320 --> 01:11:57,000 Gravity is just as it is, the forces that connect atoms are just as they are, 717 01:11:57,000 --> 01:12:02,520 and if you change any of those variables, I think there are six or ten that are very important, 718 01:12:02,520 --> 01:12:07,560 then the universe as we know it would collapse, and we wouldn't be here. 719 01:12:07,560 --> 01:12:11,580 People sometimes ask, like you did a while ago, 720 01:12:11,580 --> 01:12:18,380 how many universes of them all are like ours - where life and intelligent life are possible. 721 01:12:18,380 --> 01:12:21,600 And how come we are in ours? 722 01:12:21,600 --> 01:12:26,920 Are we simply the end result of a set of circumstances, 723 01:12:26,920 --> 01:12:31,320 or are we there because our universe somehow expected us? 724 01:12:32,160 --> 01:12:35,940 - One way to think about it, and what comes from those pictures, 725 01:12:35,940 --> 01:12:39,700 if you have a picture of Andrew with universes of different colors, 726 01:12:40,200 --> 01:12:43,100 if we can only exist in the red universe, 727 01:12:43,100 --> 01:12:46,280 then if you are wondering why we are in the red universe 728 01:12:46,280 --> 01:12:48,560 we are here because we can live here. 729 01:12:48,560 --> 01:12:51,140 We accept this reasoning in other situations as well. 730 01:12:51,140 --> 01:12:57,960 If I ask you why we live on the planet's surface, why we don't live in interstellar space, 731 01:12:57,960 --> 01:13:01,460 the answer is quite clear - we would not be able to survive in interstellar space. 732 01:13:01,460 --> 01:13:05,980 We are on a planet where conditions are receptive to life as we know it, and that is why we are here. 733 01:13:05,980 --> 01:13:11,760 Similarly: why are we in this universe? Simply because we could not exist in others. 734 01:13:11,760 --> 01:13:17,580 And maybe this seems kind of circular, tautological, but what gives it strength 735 01:13:17,580 --> 01:13:23,060 is when you really start to realize that if that picture is true, and there are really huge universes out there, 736 01:13:23,060 --> 01:13:28,480 that it is not just mathematics but reality, then of course we will be in the one in which we can live. 737 01:13:28,480 --> 01:13:33,220 And that's a reasonable explanation if this picture is really true. 738 01:13:33,220 --> 01:13:37,680 - How do you guys know that Andrei is probably right? 739 01:13:37,680 --> 01:13:40,760 Nick, how do you know the answer to your own question? 740 01:13:40,760 --> 01:13:46,920 As you know ... We can't see them, they are moving ever faster than the speed of light. 741 01:13:46,920 --> 01:13:52,200 So how do we answer the question? There is no purpose that can fly over that whole thing. 742 01:13:52,200 --> 01:13:57,220 - I think it would be too much to say that we can know at this point that Andrei is right, 743 01:13:57,220 --> 01:14:02,840 but one of the reasons we take this type of model seriously is just the problem you mentioned - 744 01:14:02,840 --> 01:14:04,840 - fine tuning problem. 745 01:14:04,840 --> 01:14:11,740 So we see that there is some amount of physical constants that seem finely tuned for life. 746 01:14:11,740 --> 01:14:19,560 That's mysterious. Why would they have exactly those values ​​that allow for the emergence of human beings or any complex chemistry. 747 01:14:19,560 --> 01:14:25,860 - And I wasn't even ... I should have told that story much more dramatically, because it's a very specific value. 748 01:14:25,860 --> 01:14:31,640 - There are four different approaches to this topic. It can only be a coincidence, 749 01:14:31,640 --> 01:14:37,000 but by definition it would be highly unlikely that the values ​​would fall out just as they should by mere coincidence. 750 01:14:37,000 --> 01:14:41,760 Of course, if you are religious you may think that God designed it to be as it is 751 01:14:41,760 --> 01:14:46,260 but this explanation creates various kinds of further problems that are well known. 752 01:14:47,440 --> 01:14:51,320 You could be looking for some simple idea basically- 753 01:14:51,320 --> 01:14:53,320 - You may be struck by lightning. 754 01:14:53,960 --> 01:14:59,960 - You could look for some simpler theory that no one came up with, some simple equation 755 01:14:59,960 --> 01:15:06,020 which is simple in itself but from which all these concrete values ​​of persistence would simply jump out. 756 01:15:06,020 --> 01:15:09,580 The problem is, no one has an idea what a simple theory that would be, 757 01:15:09,580 --> 01:15:14,320 and for the fourth time, the one Lind and Gut are exploring, 758 01:15:14,320 --> 01:15:18,680 which is that there is a large ensemble of the universe, 759 01:15:18,680 --> 01:15:23,080 and the values ​​of the constants in these universes vary randomly 760 01:15:23,080 --> 01:15:29,100 and so we get that all or almost all of the possible constellations are values ​​of these constants 761 01:15:29,100 --> 01:15:32,740 implemented or represented in some universes. 762 01:15:32,740 --> 01:15:37,400 But most of these possible universes will not have observers. 763 01:15:37,400 --> 01:15:45,740 Observers will only live in universes where values ​​are conducive to the evolution and existence of life, 764 01:15:45,740 --> 01:15:47,460 complex chemistry. 765 01:15:47,460 --> 01:15:54,320 And that is why all observers will find themselves in universes whose values ​​seem to be finely tuned 766 01:15:54,320 --> 01:15:58,860 because they only see universes that are finely tuned. Everyone else is without observers. 767 01:15:58,860 --> 01:16:02,280 Or at least they have far fewer observers than others. 768 01:16:02,280 --> 01:16:07,880 And that would then explain the impression of fine dining, and the fact that you can explain it through multiverse theory 769 01:16:07,880 --> 01:16:12,900 is one of the reasons behind this theory to be taken seriously. 770 01:16:12,900 --> 01:16:18,240 - You just created a huge array of different types of universes, conveniently getting rid of god 771 01:16:18,240 --> 01:16:23,980 and that can only be a random absurdity. But you have not got rid of the mysterious fact 772 01:16:23,980 --> 01:16:30,060 which you all stick to. And that is, at the heart of this whole system is still that flux, 773 01:16:30,060 --> 01:16:35,980 that gravity that is repulsive and pushes out, sighs and pushes out. 774 01:16:35,980 --> 01:16:40,400 That gravity has a universal presence. Much universal presence. 775 01:16:40,400 --> 01:16:45,120 Why do you all think that this should be taken for granted? 776 01:16:45,120 --> 01:16:49,100 It is an assumption like any other assumption. And you stick to it. 777 01:16:49,100 --> 01:16:56,220 - The thing we bring up here is just the simplest model, and that's why gravity is key. 778 01:16:56,220 --> 01:17:03,860 Of course we can do a lot better, but we'll have to save that for the next reunion, I guess. 779 01:17:03,860 --> 01:17:08,180 Now we are trying to do the simplest job. What we have presented to you 780 01:17:08,180 --> 01:17:14,340 all the time assuming some fundamental law of physics including gravity, 781 01:17:14,340 --> 01:17:19,620 and you already have 10 in the 500th degree of different options. So, that's just the simplest scenario. 782 01:17:19,620 --> 01:17:26,040 "So you're not worried about having to assume there is some basic but universal set of gravitational and physics laws?" 783 01:17:26,040 --> 01:17:32,020 - No, it's a self-limiting rule. 784 01:17:33,400 --> 01:17:37,900 I should probably say something psychological here. 785 01:17:39,160 --> 01:17:47,420 When I lived in Russia, there was one specific rule, and we knew that the right and the only thing was possible. 786 01:17:47,420 --> 01:17:51,160 We will expand that later. 787 01:17:51,160 --> 01:17:58,080 And if we were free from 10 to 500 options, we would be overjoyed. 788 01:17:58,080 --> 01:18:07,360 And then I came to a country that has freedom, and all of a sudden I feel like there is too much freedom, 10 to 500. We need one rule. 789 01:18:07,360 --> 01:18:10,220 I thought: God, what's going on. 790 01:18:11,280 --> 01:18:14,820 - So he likes freedom. What about you Brian? 791 01:18:14,820 --> 01:18:19,900 - The criticism you make, I think can always be addressed. 792 01:18:19,900 --> 01:18:25,860 When you are a theorist, you come up with theories, and even if they are successful you can ask why these ideas. 793 01:18:25,860 --> 01:18:30,480 I think that's a question that can always be asked, and I don't think we can really answer it. 794 01:18:30,480 --> 01:18:35,200 But speaking from my own perspective as a string theorist, I will say why I find these ideas irresistible. 795 01:18:35,200 --> 01:18:40,080 And that's really what Andrew was describing. These guys have developed very interesting cosmological theories, 796 01:18:40,080 --> 01:18:43,400 where all those bubble universes would be out there, 797 01:18:43,400 --> 01:18:47,500 and it is a very interesting cosmology. But let's put that aside for a moment. 798 01:18:47,500 --> 01:18:52,180 We've been working on string theory all these years, and there really is this feature in string theory 799 01:18:52,180 --> 01:18:56,820 where we have more than three dimensions of space. Six, maybe seven other dimensions of space 800 01:18:56,820 --> 01:19:01,980 which, as Andrew said and we saw the pictures, can be curled up into tiny spaces. 801 01:19:01,980 --> 01:19:07,100 And in the eighties, we hoped there was one particular shape for extra dimensions. 802 01:19:07,100 --> 01:19:12,820 And if we get to know him, we will be able to explain all the observed features of the world around us. 803 01:19:12,820 --> 01:19:18,280 Because it turns out that the size and shape of those extra dimensions determine things like the mass of electrons, 804 01:19:18,280 --> 01:19:21,920 or the mass of the quarks, or the force of the forces. 805 01:19:21,920 --> 01:19:27,160 So we had the picture that one day, when we figure out what the shape is for the extra dimensions, 806 01:19:27,160 --> 01:19:30,180 that we will calculate everything, we all agree and finish. 807 01:19:30,180 --> 01:19:34,720 But as we went on, we found more and more shapes for extra dimensions, 808 01:19:34,720 --> 01:19:39,940 we had a catalog of several hundred in the eighties, which grew to several thousand in the nineties, 809 01:19:39,940 --> 01:19:45,340 which then blossomed into, as Andrew put it, 10 in 500 possible different shapes for extra dimensions. 810 01:19:45,340 --> 01:19:50,740 And we were surprised because it turned out not to be the path we thought was going. 811 01:19:50,740 --> 01:19:54,900 But when coupled with a cosmological picture, it becomes very interesting. 812 01:19:54,900 --> 01:19:59,740 You have these 10 in 500 possible shapes, they are realized in all these different bubbles, 813 01:19:59,740 --> 01:20:05,280 and when you have that picture, then the explanation for why things are what they are becomes much simpler: 814 01:20:05,280 --> 01:20:09,720 we see things as they are because we can exist in that particular bubble 815 01:20:09,720 --> 01:20:14,620 with that shape for extra dimensions that is compatible with our biology and chemistry. 816 01:20:14,620 --> 01:20:17,640 - But you didn't describe the biggest bribe we gave you. 817 01:20:17,640 --> 01:20:19,640 - The biggest thing? 818 01:20:19,640 --> 01:20:20,680 - A bribe. 819 01:20:20,680 --> 01:20:22,240 - When was it? 820 01:20:24,000 --> 01:20:33,220 - Here's what happened. In 1998, cosmologists discovered that there was energy in a vacuum. 821 01:20:33,220 --> 01:20:38,620 Empty space is not completely empty, there is something called dark energy, a cosmological constant, 822 01:20:38,620 --> 01:20:41,100 vacuum energy - therefore not empty. 823 01:20:41,100 --> 01:20:44,880 And this is evident in the exponential expansion of the universe at this time. 824 01:20:44,880 --> 01:20:48,780 Five billion years ago, the universe began to expand exponentially. 825 01:20:48,780 --> 01:20:54,320 But exponential expansion is very very slow, don't worry, we have time to finish the discussion. 826 01:20:54,320 --> 01:20:59,920 But the fact is that when string theorists learned about it, they wrote to the director- 827 01:21:02,180 --> 01:21:07,180 No, the director of string theory can't ... OK, one of the main ones ... 828 01:21:07,180 --> 01:21:11,080 - A very, very respected man. 829 01:21:11,080 --> 01:21:16,560 - OK, he mentioned one of the main leaders of string theory in his speech in India 830 01:21:16,560 --> 01:21:23,100 not to know how string theory can account for this exponential expansion of the universe. 831 01:21:23,100 --> 01:21:28,120 And having said that, people were surprised, because Ed doesn't know! 832 01:21:28,120 --> 01:21:35,200 And they were scared, because nobody knows. What's happening? String theory cannot describe our universe. 833 01:21:35,200 --> 01:21:41,120 So everyone got nervous, and went to check how to describe the universe. 834 01:21:41,120 --> 01:21:44,760 And finally we found a way to describe it. 835 01:21:44,760 --> 01:21:49,340 And then we discovered those 10 in 500 different ways to describe it. 836 01:21:49,340 --> 01:21:56,520 But then it turned out to be the value of the vacuum energy that people found through experiments 837 01:21:56,520 --> 01:22:06,560 was absolutely incredibly miniature. It was 10 at minus 120 expected value. 838 01:22:07,400 --> 01:22:13,480 You see, the theorists who count it think this way: if not zero, what is the next number? 839 01:22:13,480 --> 01:22:20,740 The next number was huge, but the experiments came up with something like 10 on -120 of that number. 840 01:22:20,740 --> 01:22:27,560 Which means zero, comma and then 120 zero and then unit. 841 01:22:27,560 --> 01:22:31,460 That seemed absolutely ridiculous. 842 01:22:31,460 --> 01:22:36,320 Still, we now have these 10 in 500 states. Now look at me. 843 01:22:36,320 --> 01:22:39,740 Up here is the theoretically expected value. 844 01:22:39,740 --> 01:22:42,600 It's zero here. 845 01:22:42,600 --> 01:22:46,460 And here is the second, negative theoretically expected value. 846 01:22:46,460 --> 01:22:51,560 Now we will cut 10 into 500 different slits. 847 01:22:51,560 --> 01:22:57,720 And now we are approaching zero. We get to where 10 is at -120. 848 01:22:57,720 --> 01:23:10,140 But we keep cutting, and in this small part, 10 at -120, we have the remaining 10 at 380 slices. 849 01:23:10,140 --> 01:23:17,180 Different types of universes with a cosmological constant, which only stores experimental data. 850 01:23:17,180 --> 01:23:21,720 - I don't know what you said, but it worked out in the end, didn't it? 851 01:23:23,500 --> 01:23:31,520 - String theory allows one to describe the universe using this small vacuum energy value. 852 01:23:31,520 --> 01:23:41,180 And then comes the next step: if the vacuum energy was only a hundred times higher, or even negative - a hundred times higher but negative 853 01:23:41,180 --> 01:23:45,200 in which case we would not be able to live there. This is what the principles of entropy tell us. 854 01:23:45,200 --> 01:23:49,640 Because if the value were up here, the galaxies would have erupted. 855 01:23:49,640 --> 01:23:56,160 If the value were down here, then the universe would have fallen apart before this discussion. 856 01:23:56,160 --> 01:24:05,400 So, we realized that string theory allows one to explain this value of vacuum energy. 857 01:24:05,400 --> 01:24:10,640 So far no other explanation has been proposed. 858 01:24:10,640 --> 01:24:12,180 - Ah, here we are! 859 01:24:12,180 --> 01:24:18,680 So your final defense is that the only explanation that can possibly cover the situation is this explanation 860 01:24:18,680 --> 01:24:24,600 which we cannot test, but which may survive because right near the middle is- 861 01:24:24,600 --> 01:24:31,360 - String theory plus inflation theory together give you the only explanation for the experiment 862 01:24:31,360 --> 01:24:36,860 which was performed ten years ago. So far no one has suggested anything better. 863 01:24:36,860 --> 01:24:41,880 - But if that's your defense - let's have the best explanation ... 864 01:24:41,880 --> 01:24:47,280 Here's an overview of that explanation by Bryce DeWitt. Do you know who he is? He is important I guess. 865 01:24:47,280 --> 01:24:51,920 Bryce DeVit. I'm going where I need to get these quotes. 866 01:24:51,920 --> 01:24:54,460 Although I don't know who I'm quoting. 867 01:24:54,460 --> 01:25:00,380 "I still clearly remember the shock I experienced when I first encountered the concept of multiverse. 868 01:25:00,380 --> 01:25:04,960 The idea of ​​more than 10 in 100 slightly imperfect copies of yourself 869 01:25:04,960 --> 01:25:09,520 which are being shared with even more copies, this idea is not easy to reconcile with common sense. " 870 01:25:09,520 --> 01:25:13,200 "This is schizophrenia with a vengeance," says Brian Stewart. 871 01:25:13,200 --> 01:25:19,020 Martin Gardener, mathematician: "In my layman's view, these are frivolous fantasies. 872 01:25:19,020 --> 01:25:25,200 Certainly the hypothesis is that there is one universe with one creator easier to believe, 873 01:25:25,200 --> 01:25:29,540 but that there are countless billions of billions of worlds whose number is constantly increasing 874 01:25:29,540 --> 01:25:31,880 and which no one has created. " 875 01:25:31,880 --> 01:25:35,660 John Wheeler, Number One whom we all adore in all likelihood, says: 876 01:25:35,660 --> 01:25:39,880 "I don't know. I'm inclined to turn against it. It contains too much physical luggage." 877 01:25:39,880 --> 01:25:44,740 John S. Bell, a physicist from Ireland, says: "It's plain and simply silly." 878 01:25:44,740 --> 01:25:49,860 - Excuse me, if I can break in. One thing we didn't stress too much tonight 879 01:25:49,860 --> 01:25:52,560 is that there are many aromas of parallel universes. 880 01:25:52,560 --> 01:25:55,600 We focused on one that comes from inflationary cosmology. 881 01:25:55,600 --> 01:26:03,060 Most of the comments you make refer to the multiple-world version that comes from quantum mechanics. 882 01:26:03,060 --> 01:26:07,720 The quantum mechanical version of interpreting the idea of ​​multiple worlds is another aroma 883 01:26:07,720 --> 01:26:13,620 the ways in which parallel universes can be obtained, but quite different from the one discussed here. 884 01:26:13,620 --> 01:26:15,900 - In that case, I may not have been fair. 885 01:26:15,900 --> 01:26:20,820 - But there is a criticism that can certainly be addressed. It certainly sounds uneconomical 886 01:26:20,820 --> 01:26:25,020 when you hear that there are all these other universes, but I have to agree with Andrei. 887 01:26:25,020 --> 01:26:29,640 I certainly had the impression in the 1980s and 1990s that there was a universe, 888 01:26:29,640 --> 01:26:33,420 that we will understand his laws, come up with unique predictions, and end it. 889 01:26:33,420 --> 01:26:35,740 This is how it looked to me. 890 01:26:35,740 --> 01:26:40,020 And when that 1998 experiment that Andrey talked about, 891 01:26:40,020 --> 01:26:44,920 who discovered that the universe is accelerating expansion, which means that it is still there today 892 01:26:44,920 --> 01:26:50,780 has those things that push it away, and the amount of that dark energy, as we call it, is so fantastically small, 893 01:26:50,780 --> 01:26:56,820 around 10 to minus 120, we asked ourselves: can we predict ourselves calculating something 894 01:26:56,820 --> 01:27:03,920 starting with some interesting equations that have pi, E, root of 2 - things that appear in natural calculation, 895 01:27:03,920 --> 01:27:10,600 and that at the end of the calculation there appears a zero comma zero zero zero ... 120 zeroes and units. 896 01:27:10,600 --> 01:27:15,180 None of us can ever imagine that we will ever build a computation whose solution is this. 897 01:27:15,180 --> 01:27:18,480 So we're looking for other ways to get that result. 898 01:27:18,480 --> 01:27:23,160 And one of the other ways is that if there are many other universes where the amount of that dark energy 899 01:27:23,160 --> 01:27:28,140 varies from one to the other, then there will be at least one, provided there are enough universes out there, 900 01:27:28,140 --> 01:27:30,820 which has the low value we see. 901 01:27:30,820 --> 01:27:35,440 It's like taking a deck of cards and randomly picking one and throwing out a few, 902 01:27:35,440 --> 01:27:39,380 it's unlikely that anyone will get an ace if I just throw a few cards. 903 01:27:39,380 --> 01:27:43,540 But if there are about 900 people in this room, and even if I had 900 tickets, it means a lot of decks, 904 01:27:43,540 --> 01:27:47,160 and I throw them all out in the audience, I'm sure someone will get an ace pic. 905 01:27:47,160 --> 01:27:50,780 In fact, there are more picks if we have 900 tickets. 906 01:27:50,780 --> 01:27:55,840 - You just explained to us, the reason we're here. If only we were one of those many cards. 907 01:27:55,840 --> 01:28:02,040 - We're just an ace point somewhere. And it's hard for us to imagine calculus in a "unique" universe 908 01:28:02,040 --> 01:28:05,640 in which we get such a crazy small number that is measured. 909 01:28:05,640 --> 01:28:08,560 - But you should be scientists! 910 01:28:08,560 --> 01:28:13,700 Shouldn't you as a scientist try to find some way to test your theory? 911 01:28:13,700 --> 01:28:20,200 If the universe you want to measure ours is moving faster than the speed of light in another direction, 912 01:28:20,200 --> 01:28:22,200 how will you ever know then? 913 01:28:22,200 --> 01:28:25,040 - That's a great question, but another thing to emphasize is- 914 01:28:25,040 --> 01:28:28,020 - Whenever you say the question is great, you never think it. 915 01:28:28,020 --> 01:28:30,480 - No, no, I really mean that. 916 01:28:30,480 --> 01:28:34,460 We described different universes moving away from each other extremely fast, 917 01:28:34,460 --> 01:28:36,720 and this is in some ways a generic case. 918 01:28:36,720 --> 01:28:41,320 But if the two bubbles were very close to each other when they were created, they could shake each other. 919 01:28:41,320 --> 01:28:46,660 And if that happens, it can leave little wrinkles in the radiation we talked about, 920 01:28:46,660 --> 01:28:51,240 on microwave background radiation. And that's why people are looking for these fighters 921 01:28:51,240 --> 01:28:55,840 and that could prove that we were colliding with one of those bubble universes. 922 01:28:55,840 --> 01:28:59,320 So it is not the case that we are completely beyond the ability to test these ideas. 923 01:28:59,320 --> 01:29:01,500 - I'd like to introduce another idea. 924 01:29:01,500 --> 01:29:04,740 People are kind of used to the idea that there should be only one universe. 925 01:29:04,740 --> 01:29:07,440 When we talk about a lot of them, we seem imaginative. 926 01:29:07,440 --> 01:29:12,960 But let's think about it. Let's take all nouns in English, all nouns in the dictionary. 927 01:29:12,960 --> 01:29:18,980 How many are just one? How many are expected to have only one copy of the term? 928 01:29:18,980 --> 01:29:23,940 I know of only two nouns to be found here: "god" and "universe". 929 01:29:23,940 --> 01:29:26,300 So if you have a scientific concept- 930 01:29:26,300 --> 01:29:30,000 - Oh how I wish I could remember another noun. 931 01:29:30,000 --> 01:29:37,780 - If you have the scientific concept of the universe, do you want to put it in the same category as it, or in the same category as "planet", "galaxy" ... 932 01:29:37,780 --> 01:29:42,960 - If you want to get upset, then move on to Mr. Quiet, to Nick. 933 01:29:42,960 --> 01:29:48,920 Because his idea is the most bizarre here. And I don't know how comfortable you will feel after that. 934 01:29:48,920 --> 01:29:54,180 - I'm not sure I want to hold that honorary title. 935 01:29:54,180 --> 01:30:00,160 - That thing is called a problem ... It's called a simulation argument. 936 01:30:00,160 --> 01:30:03,940 I'll summarize and you explain. 937 01:30:03,940 --> 01:30:11,180 You believe it would be possible for the universe to be a stunningly successful computer 938 01:30:11,180 --> 01:30:19,320 who imagines the universe in such a perfect way that everyone in the simulation would 939 01:30:19,320 --> 01:30:28,420 as characters from The Matrix in that little brain, experienced an experience that seems completely real. 940 01:30:28,420 --> 01:30:35,360 I could touch you, and I could feel the texture under my skin. 941 01:30:35,360 --> 01:30:42,600 It would all be a computer simulation. Are you suggesting that a civilization could build such a machine? 942 01:30:42,600 --> 01:30:48,240 - Many have already suggested it. That's one of the options. 943 01:30:48,240 --> 01:30:55,120 The premise of "The Matrix" and the like is that, as we can do simple virtual realities today, 944 01:30:55,120 --> 01:30:58,540 with simple simulated creatures living in them, 945 01:30:58,540 --> 01:31:03,800 in the future, we may be able to build more complex virtual realities on far more powerful computers 946 01:31:03,800 --> 01:31:07,140 with more complex simulated creatures. 947 01:31:07,140 --> 01:31:13,700 Perhaps these creatures would be complex enough to have brains like ours, simulated to such details 948 01:31:13,700 --> 01:31:19,920 such as single neurons and synapses, to make the inhabitants of such simulations aware. 949 01:31:19,920 --> 01:31:25,180 But the simulation argument adds to that 950 01:31:26,640 --> 01:31:32,780 instead of dwelling on the question of how to prove with certainty that we ourselves are not in the simulation, 951 01:31:32,780 --> 01:31:38,740 the simulation argument tries to place a limit on what we can believe in. 952 01:31:38,740 --> 01:31:44,600 And he tries to show that one of the three options is true, but he doesn't tell us which one. 953 01:31:45,320 --> 01:31:51,700 In a sense, this sounds more radical than even some of the multiverse theories we've heard here, 954 01:31:51,700 --> 01:31:56,580 but in another sense it is less radical, for it assumes no unknown physics. 955 01:31:56,580 --> 01:32:02,580 Because we just assume that computers that are much more powerful could be built in the future. 956 01:32:02,580 --> 01:32:06,600 - I think they could be very powerful, because yes I think I'm in a computer simulation 957 01:32:06,600 --> 01:32:12,400 I would look at your face very carefully, because maybe one frame would occasionally skip and then I would notice. 958 01:32:13,060 --> 01:32:19,060 - We can go back to that. People often write to me about such things ... 959 01:32:20,520 --> 01:32:26,360 But never mind. What the simulation argument tries to show is that one of the three possibilities is true. 960 01:32:26,360 --> 01:32:36,700 The first is that almost all civilizations at the stage of our technological development are extinct before they become technologically mature. 961 01:32:36,700 --> 01:32:42,500 Technologically mature in the sense that they have developed all the technologies that we can presently prove to be physically possible 962 01:32:42,500 --> 01:32:45,940 using only physics that can be acquired in a non-controversial way. 963 01:32:45,940 --> 01:32:47,940 - So they make radios, rocket ships, bombs ... 964 01:32:47,940 --> 01:32:51,660 - Yes, we could make big computers the size of a planet and the like, 965 01:32:51,660 --> 01:32:53,660 we could calculate what kind of performance they would have. 966 01:32:53,660 --> 01:32:57,620 We can't make them now, but in maybe a thousand years people will do it. 967 01:32:57,620 --> 01:33:04,260 So, the first possibility is that people at our level simply fail to reach that level of technological maturity. 968 01:33:04,260 --> 01:33:07,180 Maybe they destroy themselves on the way to that. 969 01:33:07,180 --> 01:33:12,860 Alternatively, almost all civilizations that reach technological maturity 970 01:33:12,860 --> 01:33:17,600 they lose interest in creating that kind of ancestral simulation, as I call them. 971 01:33:17,600 --> 01:33:23,820 These would be detailed computer simulations of people like their historical ancestors. 972 01:33:23,820 --> 01:33:28,600 So, they have these powerful computers and the ability to program them, 973 01:33:28,600 --> 01:33:32,380 but they have smarter things to do with their computers and time. 974 01:33:32,380 --> 01:33:34,040 - And here's the third one. 975 01:33:34,040 --> 01:33:38,800 - And the third possibility is that we almost certainly live in computer simulation. 976 01:33:39,340 --> 01:33:43,540 In its full version, this argument requires some theory of probability, 977 01:33:43,540 --> 01:33:47,900 but its essence can be captured very simply and intuitively. 978 01:33:47,900 --> 01:33:52,020 Imagine the first two possibilities are incorrect. 979 01:33:52,020 --> 01:33:59,480 This means that some insignificant factions of civilization at our stage are reaching technological maturity, 980 01:33:59,480 --> 01:34:06,520 and that some negligible factions are interested in creating ancestral simulations, 981 01:34:06,520 --> 01:34:10,120 and devote some nontrivial part of the resources to that end, 982 01:34:10,120 --> 01:34:15,540 in which case you could show that there would be many more simulations of the ancestors, 983 01:34:15,540 --> 01:34:19,320 more than there would have been original streams of history. 984 01:34:19,320 --> 01:34:27,820 Because if you calculate the computing power that technologically mature civilizations would have, 985 01:34:27,820 --> 01:34:32,980 and the computational power necessary to simulate all human brains, 986 01:34:32,980 --> 01:34:37,460 it turns out that these other quantities are a small fraction of the former. 987 01:34:37,460 --> 01:34:42,800 In other words, by allocating a tiny fraction of its computing resources for these purposes, 988 01:34:42,800 --> 01:34:46,460 could create astronomical numbers, billions and billions ... 989 01:34:46,460 --> 01:34:52,320 - So you're saying that if teacher MacGattie gives a school assignment on planet Zentar in another universe: 990 01:34:52,320 --> 01:34:58,900 "Build a universe with extreme precision and make a billion people 991 01:34:58,900 --> 01:35:02,600 with each neuron in its place so that they think they are alive. Start." 992 01:35:02,600 --> 01:35:08,980 And then Perica answered, "Can I use real matter? Can I use energy and math?" 993 01:35:08,980 --> 01:35:14,100 "No, Perice, that would require 50 tons of stuff. We only need to do this bits and bytes." 994 01:35:14,100 --> 01:35:20,040 And then everyone does it in class using bits and bytes, and then next year people just push the "repeat" button? 995 01:35:20,040 --> 01:35:26,480 And then the cost of creating a fictional universe is infinitely less than the cost of building a real one? 996 01:35:26,480 --> 01:35:31,940 - Maybe not infinite, but much smaller. I would go over the question that if you have the ability to use 997 01:35:31,940 --> 01:35:37,660 some advanced form of nanotechnology to transform the planets into computer systems, 998 01:35:37,660 --> 01:35:44,120 using only one planetary computer and only a millionth of its computing power in a tiny fraction of a second, 999 01:35:44,120 --> 01:35:48,060 you could keep many many simulations of human history running. 1000 01:35:48,060 --> 01:35:55,340 - So if Perica goes to push a button like this, does that create a high probability that we are in one of such universes? 1001 01:35:55,340 --> 01:36:02,780 - Perica may be working on one, but other people will repeat it millions of years later. There would be other simulations over time. 1002 01:36:02,780 --> 01:36:05,500 - How do you wake up in the morning? 1003 01:36:08,600 --> 01:36:16,680 - To conclude this arc of argument: Assuming the first two assumptions are incorrect 1004 01:36:16,680 --> 01:36:24,340 then we come to the conclusion that there are many more simulations than the original. 1005 01:36:25,380 --> 01:36:33,680 And if almost all people with our types of experiences are simulated rather than implemented in reality, 1006 01:36:33,680 --> 01:36:38,040 we should think of ourselves as being probably typical, simulated people 1007 01:36:38,040 --> 01:36:43,520 rather than exceptional people who were part of the original history. 1008 01:36:44,560 --> 01:36:50,520 - When you came up with this idea and thought you were more likely to be simulated- 1009 01:36:50,520 --> 01:36:52,880 - Except I don't believe it to be true. 1010 01:36:52,880 --> 01:36:54,520 - Not? Good. 1011 01:36:54,520 --> 01:37:00,160 - I believe the simulation argument will show us that one of these three is true, but it does not tell us which one. 1012 01:37:00,160 --> 01:37:05,460 So I think we need to spread our trust across all three options. 1013 01:37:05,460 --> 01:37:09,400 We just don't have enough evidence to choose one. 1014 01:37:14,900 --> 01:37:20,800 Assuming the discussion works, the third possibility, the simulation hypothesis, is the correct one, 1015 01:37:20,800 --> 01:37:25,860 then the reaction of many people is that then we can just go crazy because everything is possible, 1016 01:37:25,860 --> 01:37:31,480 but if we think about it, we realize that even if we are in simulation, 1017 01:37:31,480 --> 01:37:36,240 the best way to predict what’s going to happen next, to decide what we’re going to do, 1018 01:37:36,240 --> 01:37:40,540 that these are still the methods we would use anyway, to observe patterns 1019 01:37:40,540 --> 01:37:45,500 in our simulated reality, we derive values ​​from them, and act accordingly. 1020 01:37:45,500 --> 01:37:50,740 So the implications are not as radical as they may seem at first glance. 1021 01:37:50,740 --> 01:37:54,500 - How much time do we have left? 1022 01:37:59,660 --> 01:38:03,160 I don't see anyone stopping us. So good. 1023 01:38:06,840 --> 01:38:13,780 Do you guys, collectively, consider the concept of multiverse in which this range of possibilities exists, 1024 01:38:13,780 --> 01:38:17,100 including Nick's rather bleak possibility, 1025 01:38:17,100 --> 01:38:22,100 that if you think of the universe or more of the universe this way, 1026 01:38:22,100 --> 01:38:28,180 do you feel like it's beautiful, or, 1027 01:38:29,300 --> 01:38:35,400 to use the Copernican principle of motion, or make us much smaller, 1028 01:38:35,400 --> 01:38:37,400 maybe not even real. 1029 01:38:37,860 --> 01:38:40,180 - Eh now, I mean, wait ... 1030 01:38:40,180 --> 01:38:45,960 - You left us in a rather diminished state, I think, with this idea of ​​so much ... 1031 01:38:45,960 --> 01:38:51,480 I liked it more when there was only one, because we were more important in that concept. 1032 01:38:52,180 --> 01:38:57,200 - There are many ways to look at it, but I've always felt like every time we downsize 1033 01:38:57,200 --> 01:38:59,680 the universe becomes more beautiful. 1034 01:38:59,680 --> 01:39:06,960 I mean, it's spectacular for me that we, little beings who are not special to the universe, 1035 01:39:06,960 --> 01:39:12,360 we are not in the middle of the universe, we may even be just a simulation, and yet we manage to understand so much. 1036 01:39:12,360 --> 01:39:17,020 So to me, this disparity between what we are and the grandeur of what exists, 1037 01:39:17,020 --> 01:39:21,780 the greater the distance between the two, the more spectacular our understanding becomes. 1038 01:39:21,780 --> 01:39:26,740 I don't feel diminished by it, but it gives me energy. 1039 01:39:26,740 --> 01:39:33,800 I also think our aesthetic is evolving and progressing in line with what we learn to be true. 1040 01:39:33,800 --> 01:39:39,160 There are many ideas today that, when you asked people 500 years ago what they thought of them, 1041 01:39:39,160 --> 01:39:42,980 they would consider them strange, strange and repulsive, 1042 01:39:42,980 --> 01:39:49,440 but now we are used to them and our aesthetics have aligned with them, and we now consider those theories beautiful. 1043 01:39:49,440 --> 01:39:53,300 Overall, I think we should wait to see if there is evidence for this 1044 01:39:53,300 --> 01:39:59,400 or whether we can come up with a better explanation for things that currently have an explanation only within these ideas. 1045 01:39:59,400 --> 01:40:01,400 - I'm going to ask this question the other way around. 1046 01:40:01,400 --> 01:40:05,920 Sometimes people from Manhattan go to Shanghai and experience it as so big, lush and powerful 1047 01:40:05,920 --> 01:40:09,120 that when they go back to Times Square, it seems tiny to them. 1048 01:40:09,120 --> 01:40:11,700 They feel like New York has kind of come together. 1049 01:40:11,700 --> 01:40:17,800 Let's do it with the universe. Since you all envisioned the multiverse so grandiose and Shanghai-like, 1050 01:40:17,800 --> 01:40:21,760 Does the universe you live in seem a little tiny? 1051 01:40:24,280 --> 01:40:30,340 We're nearing the end of the program, so I'm just throwing out what comes to mind. 1052 01:40:31,580 --> 01:40:37,440 - Even if you have a single universe, if it is infinite then you already have more vastness 1053 01:40:37,440 --> 01:40:39,640 than you would ever hope it could be. 1054 01:40:39,640 --> 01:40:44,760 Adding other universes to this can have interesting observational consequences. 1055 01:40:44,760 --> 01:40:50,120 But if you're only interested in size, you've already got it with standard Big Bang cosmology 1056 01:40:50,120 --> 01:40:53,520 where you have an open universe. 1057 01:40:53,520 --> 01:40:55,520 - Oh God. 1058 01:40:56,140 --> 01:40:59,660 I didn't think I'd get to this. 1059 01:41:00,620 --> 01:41:02,420 Do you... 1060 01:41:02,420 --> 01:41:04,060 Not! 1061 01:41:05,740 --> 01:41:07,740 Bhagavad Gita ... 1062 01:41:07,740 --> 01:41:09,700 I'm sorry. 1063 01:41:09,700 --> 01:41:14,840 In one of the famous books of the Mahabharata, the Bhagavad Gita, 1064 01:41:14,840 --> 01:41:25,000 there is a story about the famous warrior Arjuna. 1065 01:41:25,000 --> 01:41:34,760 He addressed Krishna, and asked him, "Can you show me your universal form?" 1066 01:41:35,300 --> 01:41:40,780 Krishna refused. But the warrior continued to pray to show him his universal form. 1067 01:41:40,780 --> 01:41:47,400 In the end, Krishna consented and showed him his universal form, 1068 01:41:47,400 --> 01:41:53,140 and this is the god who devours all, and destroys all, and gives all, 1069 01:41:53,140 --> 01:41:57,760 and he is also a lion, and a tiger, and an elephant ... 1070 01:41:57,760 --> 01:41:59,760 And he's everything! 1071 01:42:00,440 --> 01:42:07,420 And then Arjuna asked him, "Oh no. Please show your normal face!" 1072 01:42:08,060 --> 01:42:10,900 And that's the current situation. 1073 01:42:10,900 --> 01:42:17,440 Nature is much richer than previously thought. 1074 01:42:17,440 --> 01:42:23,140 But with each subsequent step of our realization, she becomes more and more beautiful. 1075 01:42:23,140 --> 01:42:27,720 It's actually absolutely exciting and thrilling when you're trying to figure it all out. 1076 01:42:27,720 --> 01:42:35,760 And, yes, when you look at it, it somehow seems dangerous. You look at her face and you don't understand what it is. 1077 01:42:35,760 --> 01:42:38,980 You might think it's better to do something else. 1078 01:42:38,980 --> 01:42:42,520 And that's why a lot of people go into finance. 1079 01:42:50,320 --> 01:42:52,320 - But that didn't work. 1080 01:42:52,940 --> 01:43:00,260 - See, that's why inflation is better in our theory! 1081 01:43:05,840 --> 01:43:10,120 - I can't think of a better way to end the discussion than to stop right here. 1082 01:43:10,120 --> 01:43:12,980 I want to thank all of you for your participation. 1083 01:43:12,980 --> 01:43:16,600 If you have the final word - feel free, but I think this one was quite good. 1084 01:43:16,600 --> 01:43:19,560 Thank you all for coming.