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These are the user uploaded subtitles that are being translated: 1 00:00:00,000 --> 00:00:01,000 SUBTITLED BY ANDROMEDA 2 00:00:01,030 --> 00:00:02,200 Now, on NOVA, 3 00:00:02,300 --> 00:00:06,300 take a thrill ride into a world|stranger than science fiction, 4 00:00:07,230 --> 00:00:08,810 where you play the game, 5 00:00:08,850 --> 00:00:10,360 by breaking some rules, 6 00:00:10,400 --> 00:00:12,860 where a new view of the universe, 7 00:00:12,900 --> 00:00:16,300 pushes you beyond the limits|of your wildest imagination. 8 00:00:16,330 --> 00:00:19,660 This is the world of string theory, 9 00:00:19,700 --> 00:00:23,700 a way of describing every force and|all matter from an atom to earth, 10 00:00:25,830 --> 00:00:27,760 to the end of the galaxies 11 00:00:27,800 --> 00:00:31,500 �from the birth of|time to its final tick� 12 00:00:31,530 --> 00:00:34,060 in a single theory, 13 00:00:34,100 --> 00:00:36,560 a theory of everything. 14 00:00:36,600 --> 00:00:40,600 Our guide to this brave|new world is Brian Greene, 15 00:00:42,030 --> 00:00:44,400 the bestselling author and physicist. 16 00:00:44,500 --> 00:00:46,200 And no matter how|many times I come here, 17 00:00:46,300 --> 00:00:47,960 I never seem to get used to it. 18 00:00:48,000 --> 00:00:52,000 Can he help us solve the|greatest puzzle of modern physics 19 00:00:53,000 --> 00:00:57,000 �that our understanding of the|universe is based on two sets of laws, 20 00:00:59,430 --> 00:01:00,960 that don't agree? 21 00:01:01,000 --> 00:01:05,000 Resolving that contradiction eluded even|Einstein, who made it his final quest. 22 00:01:08,930 --> 00:01:12,930 After decades, we may finally be|on the verge of a breakthrough. 23 00:01:14,730 --> 00:01:18,730 The solution is strings, 24 00:01:21,100 --> 00:01:25,100 tiny bits of energy vibrating|like the strings on a cello, 25 00:01:25,700 --> 00:01:29,700 a cosmic symphony at|the heart of all reality. 26 00:01:29,830 --> 00:01:33,660 But it comes at a price: 27 00:01:33,700 --> 00:01:37,500 parallel universes and 11 dimensions, 28 00:01:37,600 --> 00:01:39,800 most of which you've never seen. 29 00:01:39,900 --> 00:01:43,900 We really may live in a universe with|more dimensions than meet the eye. 30 00:01:44,730 --> 00:01:47,400 People who have said that there|were extra dimensions of space 31 00:01:47,500 --> 00:01:50,500 have been labeled crackpots,or|people who are bananas. 32 00:01:50,600 --> 00:01:54,600 A mirage of science and mathematics|or the ultimate theory of everything? 33 00:01:56,130 --> 00:02:00,130 If string theory fails to|provide a testable prediction, 34 00:02:00,530 --> 00:02:03,400 then nobody should believe it. 35 00:02:03,500 --> 00:02:04,800 Is that a theory of physics, 36 00:02:04,900 --> 00:02:06,460 or a philosophy? 37 00:02:06,500 --> 00:02:10,500 One thing that is certain is that|string theory is already showing us 38 00:02:10,830 --> 00:02:13,000 that the universe may be a lot stranger 39 00:02:13,030 --> 00:02:15,600 than any of us ever imagined. 40 00:02:15,630 --> 00:02:17,660 Coming up tonight... 41 00:02:17,700 --> 00:02:20,800 it all started with an apple. 42 00:02:20,900 --> 00:02:24,900 The triumph of Newton's|equations come from the quest 43 00:02:25,900 --> 00:02:28,300 to understand the planets and the stars. 44 00:02:28,330 --> 00:02:30,660 And we've come a long way since. 45 00:02:30,700 --> 00:02:32,800 Einstein gave the world a new picture 46 00:02:32,900 --> 00:02:35,300 for what the force of|gravity actually is. 47 00:02:35,400 --> 00:02:39,400 Where he left off, string|theorists now dare to go. 48 00:02:39,780 --> 00:02:43,780 But how close are they to|fulfilling Einstein's dream? 49 00:02:44,130 --> 00:02:47,900 Watch The Elegant Universe right now. 50 00:05:01,900 --> 00:05:03,160 50 years ago, 51 00:05:03,200 --> 00:05:04,500 this house was the scene 52 00:05:04,600 --> 00:05:06,400 of one of the greatest mysteries 53 00:05:06,430 --> 00:05:07,960 of modern science- 54 00:05:08,000 --> 00:05:09,500 a mystery so profound 55 00:05:09,530 --> 00:05:10,860 that today 56 00:05:10,900 --> 00:05:12,060 thousands of scientists 57 00:05:12,100 --> 00:05:13,850 on the cutting edge of physics 58 00:05:13,880 --> 00:05:15,600 are still trying to solve it. 59 00:05:15,630 --> 00:05:17,410 Albert Einstein spent 60 00:05:17,450 --> 00:05:19,020 his last two decades 61 00:05:19,060 --> 00:05:20,560 in this modest home 62 00:05:20,600 --> 00:05:22,860 in Princeton, New Jersey. 63 00:05:22,900 --> 00:05:26,100 And in his second floor study, 64 00:05:26,200 --> 00:05:28,300 Einstein relentlessly 65 00:05:28,400 --> 00:05:29,760 sought a single theory 66 00:05:29,800 --> 00:05:33,300 so powerful it would describe 67 00:05:33,330 --> 00:05:34,610 all the workings 68 00:05:34,650 --> 00:05:37,270 of the universe. 69 00:05:37,310 --> 00:05:39,050 Even as he neared 70 00:05:39,090 --> 00:05:40,940 the end of his life, 71 00:05:40,980 --> 00:05:42,800 Einstein kept a notepad 72 00:05:42,830 --> 00:05:43,960 close at hand, 73 00:05:44,000 --> 00:05:46,500 furiously trying to come up 74 00:05:46,530 --> 00:05:47,400 with the equations 75 00:05:47,500 --> 00:05:49,300 for what would come to be known 76 00:05:49,330 --> 00:05:51,100 as the "theory of everything. " 77 00:05:51,200 --> 00:05:54,400 Convinced he was on the verge 78 00:05:54,500 --> 00:05:56,000 of the most important discovery 79 00:05:56,030 --> 00:05:58,210 in the history of science, 80 00:05:58,250 --> 00:06:00,400 Einstein ran out of time, 81 00:06:00,500 --> 00:06:03,100 his dream unfulfilled. 82 00:06:03,130 --> 00:06:07,130 Now, almost 83 00:06:07,200 --> 00:06:08,400 a half-century later, 84 00:06:08,500 --> 00:06:11,000 Einstein's goal of unification- 85 00:06:11,030 --> 00:06:12,900 combining all the laws 86 00:06:12,930 --> 00:06:13,590 of the universe 87 00:06:13,600 --> 00:06:15,900 in one all-encompassing theory- 88 00:06:15,930 --> 00:06:18,000 has become the holy grail 89 00:06:18,100 --> 00:06:19,200 of modern physics, 90 00:06:19,300 --> 00:06:22,300 and we think we may at last 91 00:06:22,400 --> 00:06:24,450 achieve Einstein's dream 92 00:06:24,480 --> 00:06:26,740 with a new and radical set 93 00:06:26,770 --> 00:06:29,330 of ideas called string theory. 94 00:06:29,370 --> 00:06:31,900 But if this revolutionary theory 95 00:06:32,000 --> 00:06:32,690 is right, 96 00:06:32,700 --> 00:06:35,850 we're in for quite a shock. 97 00:06:35,880 --> 00:06:39,000 String theory says we may be 98 00:06:39,030 --> 00:06:40,000 living in a universe 99 00:06:40,100 --> 00:06:41,100 where reality 100 00:06:41,200 --> 00:06:44,200 meets science fiction... 101 00:06:44,230 --> 00:06:47,260 a universe of 11 dimensions 102 00:06:47,300 --> 00:06:50,300 with parallel universes 103 00:06:50,330 --> 00:06:53,210 right next door. 104 00:06:53,250 --> 00:06:56,100 An elegant universe, 105 00:06:56,200 --> 00:06:57,660 composed entirely 106 00:06:57,700 --> 00:06:59,900 of the music of strings. 107 00:07:00,000 --> 00:07:04,000 But for all its ambition, 108 00:07:05,800 --> 00:07:08,700 the basic idea of string theory 109 00:07:08,730 --> 00:07:10,760 is surprisingly simple. 110 00:07:10,800 --> 00:07:12,800 It says that everything 111 00:07:12,830 --> 00:07:13,590 in the universe, 112 00:07:13,600 --> 00:07:15,400 from the tiniest particle 113 00:07:15,500 --> 00:07:17,500 to the most distant star, 114 00:07:17,530 --> 00:07:19,500 is made from one kind 115 00:07:19,530 --> 00:07:20,290 of ingredient: 116 00:07:20,300 --> 00:07:22,400 unimaginably small, 117 00:07:22,500 --> 00:07:25,300 vibrating strands of energy 118 00:07:25,330 --> 00:07:26,660 called strings. 119 00:07:26,700 --> 00:07:30,700 Just as the strings of a cello 120 00:07:33,730 --> 00:07:34,960 can give rise 121 00:07:35,000 --> 00:07:36,000 to a rich variety 122 00:07:36,030 --> 00:07:37,000 of musical notes... 123 00:07:37,100 --> 00:07:41,100 the tiny strings 124 00:07:41,600 --> 00:07:43,500 in string theory vibrate 125 00:07:43,530 --> 00:07:44,360 in a multitude 126 00:07:44,400 --> 00:07:45,200 of different ways, 127 00:07:45,300 --> 00:07:47,700 making up all the constituents 128 00:07:47,800 --> 00:07:48,390 of nature. 129 00:07:48,400 --> 00:07:52,400 In other words, the universe 130 00:07:53,300 --> 00:07:56,000 is like a grand cosmic symphony, 131 00:07:56,030 --> 00:07:57,600 resonating with all 132 00:07:57,700 --> 00:07:59,060 the various notes 133 00:07:59,100 --> 00:08:01,400 these tiny, vibrating strands 134 00:08:01,430 --> 00:08:05,210 of energy can play. 135 00:08:05,250 --> 00:08:09,000 String theory is still 136 00:08:09,030 --> 00:08:09,960 in its infancy, 137 00:08:10,000 --> 00:08:11,700 but it's already revealing 138 00:08:11,800 --> 00:08:13,500 a radically new picture 139 00:08:13,530 --> 00:08:14,190 of the universe, 140 00:08:14,200 --> 00:08:16,700 one that is both strange 141 00:08:16,730 --> 00:08:18,360 and beautiful. 142 00:08:18,400 --> 00:08:21,800 But what makes us think 143 00:08:21,830 --> 00:08:23,210 we can understand 144 00:08:23,250 --> 00:08:24,270 all the complexity 145 00:08:24,310 --> 00:08:25,300 of the universe, 146 00:08:25,400 --> 00:08:26,860 let alone reduce it to 147 00:08:26,900 --> 00:08:28,900 a single theory of everything? 148 00:08:28,930 --> 00:08:31,760 We have R mu nu minus 149 00:08:31,800 --> 00:08:34,560 a half g mu nu R- 150 00:08:34,600 --> 00:08:36,800 you remember how this goes- 151 00:08:36,830 --> 00:08:39,000 equals eight pi g T mu nu. 152 00:08:39,100 --> 00:08:40,160 Comes from varying 153 00:08:40,200 --> 00:08:41,200 the Einstein-Hilbert Action, 154 00:08:41,300 --> 00:08:42,600 and we get the field equations 155 00:08:42,630 --> 00:08:43,910 and this term. 156 00:08:43,950 --> 00:08:45,160 You remember 157 00:08:45,200 --> 00:08:46,260 what this is called. 158 00:08:46,300 --> 00:08:50,300 No, that's the scalar curvature. 159 00:08:51,430 --> 00:08:53,600 This is the Ricci Tensor. 160 00:08:53,630 --> 00:08:56,900 Have you been 161 00:08:57,000 --> 00:08:57,860 studying this at all? 162 00:08:57,900 --> 00:09:01,900 No matter how hard you try, 163 00:09:02,000 --> 00:09:04,400 you can't teach physics 164 00:09:04,430 --> 00:09:05,460 to a dog. 165 00:09:05,500 --> 00:09:08,400 Their brains just aren't wired 166 00:09:08,430 --> 00:09:09,360 to grasp it. 167 00:09:09,400 --> 00:09:13,000 But what about us? 168 00:09:13,100 --> 00:09:15,300 How do we know that we're wired 169 00:09:15,330 --> 00:09:17,500 to comprehend the deepest laws 170 00:09:17,530 --> 00:09:18,330 of the universe? 171 00:09:18,400 --> 00:09:21,200 Well, physicists today 172 00:09:21,230 --> 00:09:24,000 are confident that we are, 173 00:09:24,030 --> 00:09:26,300 and we're picking up 174 00:09:26,400 --> 00:09:27,860 where Einstein left off 175 00:09:27,900 --> 00:09:30,800 in his quest for unification. 176 00:09:30,830 --> 00:09:34,830 Unification would be 177 00:09:35,500 --> 00:09:37,900 the formulation of a law 178 00:09:37,930 --> 00:09:40,300 that describes perhaps 179 00:09:40,400 --> 00:09:41,900 everything in the known universe 180 00:09:42,000 --> 00:09:43,700 from one single idea, 181 00:09:43,800 --> 00:09:45,300 one master equation. 182 00:09:45,400 --> 00:09:47,200 And we think that there might 183 00:09:47,230 --> 00:09:48,560 be this master equation 184 00:09:48,600 --> 00:09:50,200 because throughout the course 185 00:09:50,300 --> 00:09:52,700 of the last 200 years or so, 186 00:09:52,730 --> 00:09:53,660 our understanding 187 00:09:53,700 --> 00:09:54,560 of the universe 188 00:09:54,600 --> 00:09:55,800 has given us a variety 189 00:09:55,830 --> 00:09:56,590 of explanations 190 00:09:56,600 --> 00:09:57,800 that are all pointing 191 00:09:57,830 --> 00:09:59,000 towards one spot. 192 00:09:59,100 --> 00:10:00,500 They seem to all be converging 193 00:10:00,530 --> 00:10:02,600 on one nugget of an idea 194 00:10:02,700 --> 00:10:05,650 that we're still trying to find. 195 00:10:05,680 --> 00:10:08,600 Unification is where it's at. 196 00:10:08,700 --> 00:10:12,700 Unification is what we're trying 197 00:10:12,730 --> 00:10:13,500 to accomplish. 198 00:10:13,500 --> 00:10:14,190 The whole aim 199 00:10:14,200 --> 00:10:16,600 of fundamental physics 200 00:10:16,630 --> 00:10:19,000 is to see more and more 201 00:10:19,100 --> 00:10:20,560 of the world's phenomena 202 00:10:20,600 --> 00:10:22,400 in terms of fewer and fewer and 203 00:10:22,430 --> 00:10:24,200 simpler and simpler principles. 204 00:10:24,230 --> 00:10:27,300 We feel, as physicists, 205 00:10:27,400 --> 00:10:29,000 that if we can explain 206 00:10:29,030 --> 00:10:30,710 a wide number of phenomena 207 00:10:30,750 --> 00:10:32,360 in a very simple manner, 208 00:10:32,400 --> 00:10:34,300 that that's somehow progress. 209 00:10:34,400 --> 00:10:36,100 There is almost 210 00:10:36,130 --> 00:10:37,910 an emotional aspect 211 00:10:37,950 --> 00:10:39,660 to the way in which 212 00:10:39,700 --> 00:10:42,750 the great theories in physics 213 00:10:42,780 --> 00:10:45,800 sort of encompass a wide variety 214 00:10:45,830 --> 00:10:46,960 of apparently different 215 00:10:47,000 --> 00:10:48,350 physical phenomena. 216 00:10:48,380 --> 00:10:49,440 So this idea that 217 00:10:49,470 --> 00:10:50,460 we should be aiming 218 00:10:50,500 --> 00:10:52,100 to unify our understanding 219 00:10:52,130 --> 00:10:53,410 is inherent, essentially, 220 00:10:53,450 --> 00:10:54,700 to the whole way in which 221 00:10:54,800 --> 00:10:56,800 this kind of science progresses. 222 00:10:56,830 --> 00:11:00,830 And long before Einstein, 223 00:11:02,600 --> 00:11:04,950 the quest for unification began 224 00:11:04,980 --> 00:11:07,300 with the most famous accident 225 00:11:07,400 --> 00:11:09,060 in the history of science. 226 00:11:09,100 --> 00:11:12,500 As the story goes, one day in 1665, 227 00:11:13,100 --> 00:11:15,600 a young man was sitting under|a tree, when all of a sudden, 228 00:11:16,000 --> 00:11:17,900 he saw an apple fall from above. 229 00:11:18,700 --> 00:11:20,100 And with the fall of that apple, 230 00:11:20,600 --> 00:11:23,000 Isaac Newton revolutionized|our picture of the universe. 231 00:11:24,400 --> 00:11:26,900 In an audacious proposal for his time, 232 00:11:27,700 --> 00:11:31,000 Newton proclaimed that the force|pulling apples to the ground... 233 00:11:33,200 --> 00:11:36,200 and the force keeping the|moon in orbit around the earth 234 00:11:36,300 --> 00:11:39,700 were actually one and the same. 235 00:11:39,730 --> 00:11:42,100 In one fell swoop, 236 00:11:42,200 --> 00:11:46,200 Newton unified the heavens and the earth 237 00:11:47,030 --> 00:11:51,030 in a single theory he called gravity. 238 00:11:51,800 --> 00:11:55,800 The unification of the|celestial with the terrestrial- 239 00:11:56,300 --> 00:12:00,250 that the same laws that govern|the planets in their motions 240 00:12:00,280 --> 00:12:04,280 govern the tides and the|falling of fruit here on Earth. 241 00:12:04,970 --> 00:12:08,970 It was a fantastic unification|of our picture of nature. 242 00:12:09,630 --> 00:12:12,760 Gravity was the first force 243 00:12:12,800 --> 00:12:14,460 to be understood scientifically, 244 00:12:14,500 --> 00:12:16,560 though three morewould|eventually follow. 245 00:12:16,600 --> 00:12:19,400 And although Newton|discovered his law of gravity 246 00:12:19,430 --> 00:12:21,360 more than 300 years ago, 247 00:12:21,400 --> 00:12:23,500 his equations describing this force 248 00:12:23,600 --> 00:12:24,960 make such accurate predictions 249 00:12:25,000 --> 00:12:26,900 that we still make use of them today. 250 00:12:26,930 --> 00:12:29,360 In fact, scientists needed 251 00:12:29,400 --> 00:12:31,560 nothing more than Newton's equations 252 00:12:31,600 --> 00:12:35,600 to plot the course of a rocket|that landed men on the moon. 253 00:12:35,930 --> 00:12:37,860 Eleven, this is Houston. 254 00:12:37,900 --> 00:12:39,760 Yet, there was a problem. 255 00:12:39,800 --> 00:12:43,800 While his laws described|the strength of gravity 256 00:12:44,100 --> 00:12:45,260 with great accuracy, 257 00:12:45,300 --> 00:12:49,300 Newton was harboring|an embarrassing secret: 258 00:12:49,930 --> 00:12:53,930 He had no idea how|gravity actually works. 259 00:12:54,600 --> 00:12:58,600 For nearly 250 years, 260 00:13:03,800 --> 00:13:06,600 scientists were content|to look the other way 261 00:13:06,630 --> 00:13:08,800 when confronted with this mystery. 262 00:13:08,830 --> 00:13:12,830 But in the early 1900s, 263 00:13:13,500 --> 00:13:17,200 an unknown clerk working|in the Swiss patent office 264 00:13:17,230 --> 00:13:18,660 would change all that. 265 00:13:18,700 --> 00:13:22,160 While reviewing patent applications, 266 00:13:22,200 --> 00:13:26,200 Albert Einstein was also|pondering the behavior of light. 267 00:13:26,680 --> 00:13:30,680 And little did Einstein know|that his musings on light 268 00:13:31,100 --> 00:13:35,100 would lead him to solve Newton's|mystery of what gravity is. 269 00:13:35,230 --> 00:13:39,230 At the age of 26, Einstein|made a startling discovery- 270 00:13:41,900 --> 00:13:45,900 that the velocity of light is|a kind of cosmic speed limit, 271 00:13:48,230 --> 00:13:51,900 a speed that nothing in|the universe can exceed. 272 00:13:52,000 --> 00:13:55,900 But no sooner had the young|Einstein published this idea 273 00:13:56,000 --> 00:14:00,000 than he found himself squaring|off with the father of gravity. 274 00:14:01,700 --> 00:14:05,700 The trouble was 275 00:14:07,100 --> 00:14:11,000 the idea that nothing can go|faster than the speed of light 276 00:14:11,030 --> 00:14:14,860 flew in the face of|Newton's picture of gravity. 277 00:14:14,900 --> 00:14:18,900 To understand this conflict, we|have to run a few experiments. 278 00:14:22,030 --> 00:14:26,030 And to begin with, let's|create a cosmic catastrophe. 279 00:14:27,300 --> 00:14:31,300 Imagine that all of a sudden|and without any warning, 280 00:14:32,600 --> 00:14:35,700 the sun vaporizes and|completely disappears. 281 00:14:35,730 --> 00:14:39,730 Now let's replaythat catastrophe 282 00:14:41,400 --> 00:14:43,500 and see what effect it|would have on the planets 283 00:14:43,530 --> 00:14:45,260 according to Newton. 284 00:14:45,300 --> 00:14:49,300 Newton's theory predicts that|with the destruction of the sun, 285 00:14:49,830 --> 00:14:53,830 the planets would immediately|fly out of their orbits, 286 00:14:55,730 --> 00:14:58,260 careening off into space. 287 00:14:58,300 --> 00:15:02,300 In other words, Newton thought|that gravity was a force 288 00:15:07,000 --> 00:15:10,000 that acts instantaneously|across any distance, 289 00:15:10,100 --> 00:15:12,900 and so we would|immediately feel the effect 290 00:15:12,930 --> 00:15:14,260 of the sun's destruction. 291 00:15:14,300 --> 00:15:18,300 But Einstein saw a big|problem with Newton's theory- 292 00:15:18,400 --> 00:15:22,400 a problem that arose|from his work with light. 293 00:15:22,900 --> 00:15:26,900 Einstein knew light doesn't|travel instantaneously. 294 00:15:27,880 --> 00:15:31,880 In fact, it takes eight|minutes for the sun's rays 295 00:15:32,900 --> 00:15:36,560 to travel the 93 million|miles to the earth. 296 00:15:36,600 --> 00:15:40,600 And since he had shown that|nothing, not even gravity, 297 00:15:41,230 --> 00:15:43,260 can travel faster than light, 298 00:15:43,300 --> 00:15:47,300 how could the earth|be released from orbit 299 00:15:48,200 --> 00:15:52,200 before the darkness resulting|from the sun's disappearance 300 00:15:52,430 --> 00:15:55,700 reached our eyes? 301 00:15:55,800 --> 00:15:59,800 To the young upstart from|the Swiss patent office, 302 00:16:04,800 --> 00:16:08,360 anything outrunning|light was impossible, 303 00:16:08,400 --> 00:16:12,400 and that meant the 250-year-old|Newtonian picture of gravity 304 00:16:13,830 --> 00:16:15,300 was wrong. 305 00:16:15,400 --> 00:16:19,400 If Newton is wrong, then|why do the planets stay up? 306 00:16:20,080 --> 00:16:24,080 Because remember, the|triumph of Newton's equations 307 00:16:24,800 --> 00:16:28,300 come from the quest to understand 308 00:16:28,400 --> 00:16:31,150 the planets and the stars,|and particularly the problem 309 00:16:31,180 --> 00:16:33,900 of why do the planets have|the orbits that they do. 310 00:16:33,930 --> 00:16:36,960 And with Newton's equations, 311 00:16:37,000 --> 00:16:39,400 you can calculate the way|that the planets will move. 312 00:16:39,430 --> 00:16:43,430 Einstein's got to resolve this dilemma. 313 00:16:43,750 --> 00:16:47,750 In his late 20s, Einstein had to come up 314 00:16:48,100 --> 00:16:49,860 with a new picture of the universe 315 00:16:49,900 --> 00:16:53,800 in which gravity does not|exceed the cosmic speed limit. 316 00:16:53,830 --> 00:16:56,960 Still working his day|job in the patent office, 317 00:16:57,000 --> 00:17:01,000 Einstein embarked on a solitary|quest to solve this mystery. 318 00:17:01,530 --> 00:17:05,530 After nearly ten years|of wracking his brain, 319 00:17:07,050 --> 00:17:11,050 he found the answer in a|new kind of unification. 320 00:17:16,100 --> 00:17:20,100 Einstein came to think of|the three dimensions of space 321 00:17:20,600 --> 00:17:22,160 and the single dimension of time 322 00:17:22,200 --> 00:17:26,200 as bound together in a|single fabric of space-time. 323 00:17:33,000 --> 00:17:35,560 It was his hope that by understanding 324 00:17:35,600 --> 00:17:39,600 the geometry of this|four-dimensional fabric of space-time 325 00:17:40,180 --> 00:17:44,180 that he could simply talk about|things moving along surfaces 326 00:17:44,900 --> 00:17:47,100 in this space-time fabric. 327 00:17:49,400 --> 00:17:50,700 Like the surface of a trampoline, 328 00:17:50,800 --> 00:17:54,200 this unified fabric|is warped and stretched 329 00:17:54,300 --> 00:17:57,300 by heavy objects like planets and stars. 330 00:17:57,400 --> 00:18:01,400 And it's this warping,|or curving, of space-time 331 00:18:03,130 --> 00:18:06,610 that creates what we feel as gravity. 332 00:18:06,650 --> 00:18:10,100 A planet like the earth is kept in orbit 333 00:18:10,130 --> 00:18:11,800 not because the sun reaches out 334 00:18:11,900 --> 00:18:15,550 and instantaneously grabs hold|of it as in Newton's theory, 335 00:18:15,580 --> 00:18:19,200 but simply because it follows|curves in the spatial fabric 336 00:18:19,300 --> 00:18:21,160 caused by the sun's presence. 337 00:18:21,200 --> 00:18:23,800 So, with this new|understanding of gravity, 338 00:18:23,830 --> 00:18:26,300 let's rerun the cosmic catastrophe. 339 00:18:26,400 --> 00:18:29,300 Let's see what happens|now if the sun disappears. 340 00:18:29,330 --> 00:18:33,330 The gravitational|disturbance that results 341 00:18:34,600 --> 00:18:38,500 will form a wave that travels|across the spatial fabric 342 00:18:38,530 --> 00:18:42,210 in much the same way that|a pebble dropped into a pond 343 00:18:42,250 --> 00:18:45,900 makes ripples that travel|across the surface of the water. 344 00:18:46,000 --> 00:18:49,900 So we wouldn't feel a change|in our orbit around the sun 345 00:18:49,930 --> 00:18:53,460 until this wave reached the earth. 346 00:18:53,500 --> 00:18:57,500 What's more, Einstein calculated|that these ripples of gravity 347 00:18:59,930 --> 00:19:03,700 travel at exactly the speed of light. 348 00:19:03,730 --> 00:19:07,700 And so, with this new approach, 349 00:19:07,800 --> 00:19:10,500 Einstein resolved the|conflict with Newton 350 00:19:10,530 --> 00:19:12,760 over how fast gravity travels. 351 00:19:12,800 --> 00:19:16,700 And more than that, Einstein|gave the world a new picture 352 00:19:16,730 --> 00:19:19,060 for what the force of|gravity actually is: 353 00:19:19,100 --> 00:19:23,100 it's warps and curves in|the fabric of space and time. 354 00:19:24,300 --> 00:19:28,300 Einstein called this new picture|of gravity "general relativity," 355 00:19:30,130 --> 00:19:32,500 and within a few short years, 356 00:19:32,600 --> 00:19:36,000 Albert Einstein became a household name. 357 00:19:36,030 --> 00:19:39,400 Einstein was like a|rock star in his day. 358 00:19:39,430 --> 00:19:41,760 He was one of the most widely known 359 00:19:41,800 --> 00:19:44,060 and recognizable figures alive. 360 00:19:44,100 --> 00:19:47,400 He and perhaps Charlie|Chaplin were the reigning kings 361 00:19:47,430 --> 00:19:48,500 of the popular media. 362 00:19:48,600 --> 00:19:51,200 People followed his work. 363 00:19:51,300 --> 00:19:55,300 And they were anticipating,|because of this wonderful thing 364 00:19:55,730 --> 00:19:57,500 he had done with general relativity- 365 00:19:57,600 --> 00:20:01,600 this recasting the laws of|gravity out of his head- 366 00:20:03,330 --> 00:20:05,860 there was the thought|he could do it again 367 00:20:05,900 --> 00:20:08,000 and they... you know,|people want to be in on that. 368 00:20:08,100 --> 00:20:11,100 Despite all that he had achieved, 369 00:20:11,130 --> 00:20:13,700 Einstein wasn't satisfied. 370 00:20:13,800 --> 00:20:17,300 He immediately set his sights|on an even grander goal: 371 00:20:17,330 --> 00:20:19,760 the unification of his|new picture of gravity 372 00:20:19,800 --> 00:20:23,600 with the only other force known|at the time, electromagnetism. 373 00:20:23,700 --> 00:20:27,700 Now, electromagnetism is a force|that had itself been unified 374 00:20:29,230 --> 00:20:31,160 only a few decades earlier. 375 00:20:31,200 --> 00:20:35,200 In the mid-1800s,|electricity and magnetism 376 00:20:36,830 --> 00:20:39,860 were sparking scientists' interest. 377 00:20:39,900 --> 00:20:43,900 These two forces seemed to|share a curious relationship 378 00:20:44,480 --> 00:20:48,480 that inventors like Samuel|Morse were taking advantage of 379 00:20:49,030 --> 00:20:51,900 in newfangled devices|such as the telegraph. 380 00:20:52,000 --> 00:20:56,000 An electrical pulse, sent|through a telegraph wire 381 00:20:58,030 --> 00:21:00,200 to a magnet thousands of miles away, 382 00:21:00,300 --> 00:21:04,300 produced the familiar dots|and dashes of Morse code 383 00:21:04,600 --> 00:21:08,000 that allowed messages to be|transmitted across the continent 384 00:21:08,030 --> 00:21:10,260 in a fraction of a second. 385 00:21:10,300 --> 00:21:14,100 Although the telegraph was a sensation, 386 00:21:14,130 --> 00:21:16,810 the fundamental science driving it 387 00:21:16,850 --> 00:21:19,460 remained something of a mystery. 388 00:21:19,500 --> 00:21:23,500 But to a Scottish scientist|named James Clerk Maxwell, 389 00:21:27,700 --> 00:21:31,700 the relationship between|electricity and magnetism 390 00:21:32,700 --> 00:21:36,700 was so obvious in nature|that it demanded unification. 391 00:21:39,500 --> 00:21:43,500 If you've ever been on top of a|mountain during a thunderstorm, 392 00:21:45,530 --> 00:21:49,500 you'll get the idea of how|electricity and magnetism 393 00:21:49,530 --> 00:21:51,300 are closely related. 394 00:21:51,400 --> 00:21:54,750 When a stream of electrically|charged particles flows, 395 00:21:54,780 --> 00:21:58,100 like in a bolt of lightning,|it creates a magnetic field, 396 00:21:58,130 --> 00:22:00,700 and you can see evidence|of this on a compass. 397 00:22:00,730 --> 00:22:04,730 Obsessed with this relationship, 398 00:22:11,800 --> 00:22:15,200 the Scot was determined|to explain the connection 399 00:22:15,230 --> 00:22:17,810 between electricity and magnetism 400 00:22:17,850 --> 00:22:20,870 in the language of mathematics. 401 00:22:20,910 --> 00:22:23,900 Casting new light on the subject, 402 00:22:24,000 --> 00:22:25,960 Maxwell devised a set 403 00:22:26,000 --> 00:22:29,100 of four elegant|mathematical equations... 404 00:22:29,200 --> 00:22:33,200 that unified electricity and magnetism 405 00:22:35,480 --> 00:22:39,480 in a single force|called electromagnetism. 406 00:22:41,730 --> 00:22:45,730 And like Isaac Newton before him, 407 00:22:45,900 --> 00:22:49,600 Maxwell's unification|took science a step closer 408 00:22:49,630 --> 00:22:52,200 to cracking the code of the universe. 409 00:22:52,300 --> 00:22:55,600 That was really the remarkable thing 410 00:22:55,700 --> 00:22:56,700 that these different phenomena 411 00:22:56,800 --> 00:22:59,160 were really connected in this way. 412 00:22:59,200 --> 00:23:03,200 And it's another example|of diverse phenomena 413 00:23:03,600 --> 00:23:07,100 coming from a single|underlying building block 414 00:23:07,200 --> 00:23:08,260 or a single underlying principle. 415 00:23:08,300 --> 00:23:12,100 Imagine that everything|that you can think of 416 00:23:12,130 --> 00:23:15,900 which has to do with|electricity and magnetism 417 00:23:16,000 --> 00:23:20,000 can all be written in|four very simple equations. 418 00:23:21,130 --> 00:23:23,800 Isn't that incredible? 419 00:23:23,900 --> 00:23:25,800 Isn't that amazing? 420 00:23:25,830 --> 00:23:27,700 I call that elegant. 421 00:23:27,800 --> 00:23:30,560 Einstein thought that this 422 00:23:30,600 --> 00:23:33,600 was one of the triumphant|moments of all of physics 423 00:23:33,630 --> 00:23:36,600 and admired Maxwell hugely|for what he had done. 424 00:23:36,630 --> 00:23:39,560 About 50 years 425 00:23:39,600 --> 00:23:42,800 after Maxwell unified|electricity and magnetism, 426 00:23:42,830 --> 00:23:45,960 Einstein was confident|that if he could unify 427 00:23:46,000 --> 00:23:49,400 his new theory of gravity with|Maxwell's electromagnetism, 428 00:23:49,500 --> 00:23:52,500 he'd be able to formulate|a master equation 429 00:23:52,600 --> 00:23:56,100 that could describe|everything, the entire universe. 430 00:23:56,130 --> 00:24:00,130 Einstein clearly believes|that the universe has 431 00:24:02,030 --> 00:24:05,600 an overall grand and beautiful pattern 432 00:24:05,630 --> 00:24:06,660 to the way that it works. 433 00:24:06,700 --> 00:24:08,760 And so to answer the question, 434 00:24:08,800 --> 00:24:10,700 why was he looking for the unification? 435 00:24:10,730 --> 00:24:12,160 I think the answer is simply 436 00:24:12,200 --> 00:24:15,400 that Einstein is one of those physicists 437 00:24:15,430 --> 00:24:18,600 who really wants to|know the mind of God, 438 00:24:18,630 --> 00:24:21,600 which means the entire picture. 439 00:24:25,400 --> 00:24:29,400 Today this is the|goal of string theory- 440 00:24:29,830 --> 00:24:33,830 to unify our understanding of everything 441 00:24:34,300 --> 00:24:37,150 from the birth of the universe 442 00:24:37,180 --> 00:24:40,000 to the majestic swirl of galaxies 443 00:24:40,100 --> 00:24:44,100 in just one set of principles-|one master equation. 444 00:24:45,930 --> 00:24:49,930 Newton had unified the|heavens and the earth 445 00:24:51,930 --> 00:24:53,760 in the theory of gravity. 446 00:24:53,800 --> 00:24:57,800 Maxwell had unified|electricity and magnetism. 447 00:24:59,000 --> 00:25:02,450 Einstein reasoned all that remained 448 00:25:02,480 --> 00:25:05,390 to build a theory of everything- 449 00:25:05,420 --> 00:25:08,300 a single theory that could encompass 450 00:25:08,330 --> 00:25:09,760 all the laws of the universe- 451 00:25:09,800 --> 00:25:13,800 was to merge his new picture of|gravity with electromagnetism. 452 00:25:14,400 --> 00:25:16,760 He certainly had motivation. 453 00:25:16,800 --> 00:25:19,400 Probably one of them|might have been aesthetics, 454 00:25:19,430 --> 00:25:21,260 or this quest to simplify. 455 00:25:21,300 --> 00:25:23,900 Another one might have|been just the physical fact 456 00:25:23,930 --> 00:25:25,900 that it seems like the speed of gravity 457 00:25:25,930 --> 00:25:27,300 is equal to the speed of light. 458 00:25:27,400 --> 00:25:30,860 So if they both go at the same speed, 459 00:25:30,900 --> 00:25:34,000 then maybe that's an indication|of some underlying symmetry. 460 00:25:34,100 --> 00:25:38,060 But as Einstein began trying 461 00:25:38,100 --> 00:25:40,300 to unite gravity and electromagnetism, 462 00:25:40,400 --> 00:25:43,160 he would find that the|difference in strength 463 00:25:43,200 --> 00:25:47,000 between these two forces would|outweigh their similarities. 464 00:25:47,100 --> 00:25:49,560 Let me show you what I mean. 465 00:25:49,600 --> 00:25:53,600 We tend to think that|gravity is a powerful force. 466 00:25:54,300 --> 00:25:57,200 After all, it's the force 467 00:25:57,300 --> 00:26:00,200 that right now is|anchoring me to this ledge. 468 00:26:00,230 --> 00:26:04,230 But compared to electromagnetism, 469 00:26:05,800 --> 00:26:07,260 it's actually terribly feeble. 470 00:26:07,300 --> 00:26:10,260 In fact, there's a simple|little test to show this. 471 00:26:10,300 --> 00:26:14,000 Imagine that I was to leap|from this rather tall building. 472 00:26:14,100 --> 00:26:17,000 Actually, let's not just imagine it. 473 00:26:17,030 --> 00:26:17,960 Let's do it. 474 00:26:18,000 --> 00:26:19,000 You'll see what I mean. 475 00:26:19,100 --> 00:26:23,100 Now, of course, I really|should have been flattened. 476 00:26:42,000 --> 00:26:43,260 But the important question is: 477 00:26:43,300 --> 00:26:45,800 what kept me from crashing|through the sidewalk 478 00:26:45,900 --> 00:26:48,200 and hurtling right down|to the center of the earth? 479 00:26:48,300 --> 00:26:52,300 Well, strange as it sounds,the|answer is electromagnetism. 480 00:26:56,200 --> 00:27:00,200 Everything we can see from|you and me to the sidewalk 481 00:27:01,030 --> 00:27:04,500 is made of tiny bits|of matter called atoms. 482 00:27:04,530 --> 00:27:07,660 And the outer shell of every atom 483 00:27:07,700 --> 00:27:10,500 contains a negative electrical charge. 484 00:27:10,600 --> 00:27:14,600 So when my atoms collide|with the atoms in the cement, 485 00:27:15,000 --> 00:27:19,000 these electrical charges repel|each other with such strength 486 00:27:19,300 --> 00:27:21,800 that just a little piece of sidewalk 487 00:27:21,830 --> 00:27:24,300 can resist the entire Earth's gravity 488 00:27:24,330 --> 00:27:26,060 and stop me from falling. 489 00:27:26,100 --> 00:27:29,200 In fact, the electromagnetic force 490 00:27:29,300 --> 00:27:33,300 is billions and billions of|times stronger than gravity. 491 00:27:34,300 --> 00:27:35,960 That seems a little strange 492 00:27:36,000 --> 00:27:37,800 because gravity keeps|our feet to the ground, 493 00:27:37,900 --> 00:27:39,200 it keeps the earth going around the sun. 494 00:27:39,300 --> 00:27:42,500 But in actual fact,|it manages to do that 495 00:27:42,530 --> 00:27:43,660 only because it acts 496 00:27:43,700 --> 00:27:46,600 on huge, enormous|conglomerates of matter- 497 00:27:46,700 --> 00:27:48,760 you know, you, me, the earth, the sun. 498 00:27:48,800 --> 00:27:51,660 But really at the level|of individual atoms, 499 00:27:51,700 --> 00:27:54,900 gravity is a really|incredibly feeble, tiny force. 500 00:27:54,930 --> 00:27:58,930 It would be an uphill|battle for Einstein 501 00:28:02,000 --> 00:28:05,900 to unify these two forces of|wildly different strengths. 502 00:28:05,930 --> 00:28:09,930 And to make matters|worse, barely had he begun 503 00:28:10,500 --> 00:28:13,800 before sweeping changes|in the world of physics 504 00:28:13,830 --> 00:28:15,460 would leave him behind. 505 00:28:15,500 --> 00:28:19,050 Einstein had achieved so much 506 00:28:19,080 --> 00:28:22,560 in the years up to about 1920 507 00:28:22,600 --> 00:28:26,500 that he naturally expected|that he could go on 508 00:28:26,530 --> 00:28:29,260 by playing the same theoretical games 509 00:28:29,300 --> 00:28:32,000 and go on achieving great things. 510 00:28:32,030 --> 00:28:33,360 And he couldn't. 511 00:28:33,400 --> 00:28:37,400 Nature revealed itself in other|ways in the 1920s and 1930s, 512 00:28:42,030 --> 00:28:44,510 and the particular tricks and tools 513 00:28:44,550 --> 00:28:47,000 that Einstein had at his disposal 514 00:28:47,100 --> 00:28:49,200 that had been so fabulously successful 515 00:28:49,230 --> 00:28:52,560 just weren't applicable anymore. 516 00:28:52,600 --> 00:28:56,600 You see, in the 1920s,a|group of young scientists 517 00:29:02,230 --> 00:29:04,360 stole the spotlight from Einstein 518 00:29:04,400 --> 00:29:07,200 when they came upwith|an outlandish new way 519 00:29:07,230 --> 00:29:08,500 of thinking about physics. 520 00:29:08,600 --> 00:29:12,600 Their vision of the|universewas so strange 521 00:29:15,030 --> 00:29:17,760 it makes science fiction look tame, 522 00:29:17,800 --> 00:29:21,800 and it turned Einstein's quest|for unification on its head. 523 00:29:22,100 --> 00:29:24,560 Unification, unification. 524 00:29:24,600 --> 00:29:28,600 Led by Danish physicist Niels Bohr, 525 00:29:28,630 --> 00:29:32,600 these scientists were uncovering 526 00:29:32,700 --> 00:29:35,600 an entirely new realm of the universe. 527 00:29:35,630 --> 00:29:39,100 Atoms- long thought to be 528 00:29:39,200 --> 00:29:41,360 the smallest constituentsof nature- 529 00:29:41,400 --> 00:29:45,400 were found to consist of|even smaller particles, 530 00:29:45,430 --> 00:29:49,400 the now familiar nucleus|of protons and neutrons 531 00:29:49,500 --> 00:29:51,560 orbited by electrons. 532 00:29:51,600 --> 00:29:54,700 And the theoriesof Einstein and Maxwell 533 00:29:54,800 --> 00:29:57,060 were useless at explaining 534 00:29:57,100 --> 00:29:59,750 the bizarre way these|tiny bits of matter 535 00:29:59,780 --> 00:30:02,400 interact with each|other inside the atom. 536 00:30:02,430 --> 00:30:05,900 There was a tremendous mystery 537 00:30:06,000 --> 00:30:08,160 about how to account for all this- 538 00:30:08,200 --> 00:30:11,800 how to account for what|was happening to the nucleus 539 00:30:11,830 --> 00:30:15,400 as the atom began to be|pried apart in different ways. 540 00:30:15,500 --> 00:30:19,500 And the old theories|were totally inadequate 541 00:30:20,100 --> 00:30:21,560 to the task of explaining them. 542 00:30:21,600 --> 00:30:24,360 Gravity was irrelevant-it|was far too weak- 543 00:30:24,400 --> 00:30:28,400 and electricity and|magnetism was not sufficient. 544 00:30:29,830 --> 00:30:33,830 Without a theory to explain|this strange new world, 545 00:30:35,200 --> 00:30:39,200 these scientists were lost in|an unfamiliar atomic territory 546 00:30:41,130 --> 00:30:45,130 looking forany recognizable landmarks. 547 00:30:54,050 --> 00:30:58,050 Then in the late|1920s, all that changed. 548 00:31:07,000 --> 00:31:08,360 During those years, 549 00:31:08,400 --> 00:31:12,100 physicists developed a new|theory called quantum mechanics, 550 00:31:12,200 --> 00:31:14,160 and it was able to describe 551 00:31:14,200 --> 00:31:16,900 the microscopic realm|with great success. 552 00:31:16,930 --> 00:31:18,700 But here's the thing: 553 00:31:18,800 --> 00:31:22,100 quantum mechanics was|so radical a theory 554 00:31:22,200 --> 00:31:23,900 that it completely shattered 555 00:31:24,000 --> 00:31:26,000 all previous ways of|looking at the universe. 556 00:31:26,030 --> 00:31:29,460 Einstein's theories demand 557 00:31:29,500 --> 00:31:32,600 that the universe is|orderly and predictable. 558 00:31:32,630 --> 00:31:36,630 But Niels Bohr disagreed. 559 00:31:37,200 --> 00:31:39,600 He and his colleagues proclaimed 560 00:31:39,700 --> 00:31:41,800 that at the scale of|atoms and particles, 561 00:31:41,830 --> 00:31:44,860 the world is a game of chance. 562 00:31:44,900 --> 00:31:48,900 At the atomic or quantum|level,uncertainty rules. 563 00:31:49,880 --> 00:31:53,880 The best you can do according|to quantum mechanics 564 00:31:54,900 --> 00:31:58,100 is predict the chance, or probability, 565 00:31:58,130 --> 00:32:01,660 of one outcome or another. 566 00:32:01,700 --> 00:32:05,200 And this strange idea... 567 00:32:05,300 --> 00:32:06,160 Thanks. 568 00:32:06,200 --> 00:32:10,200 opened the door to an unsettling|new picture of reality. 569 00:32:10,700 --> 00:32:14,700 It was so unsettling 570 00:32:19,600 --> 00:32:22,700 that if the bizarre|features of quantum mechanics 571 00:32:22,800 --> 00:32:24,950 were noticeablein our everyday world, 572 00:32:24,980 --> 00:32:27,690 like they are here in the Quantum Caf�, 573 00:32:27,720 --> 00:32:30,400 you might think you'd lost your mind. 574 00:32:30,430 --> 00:32:32,360 The laws in the quantum world 575 00:32:32,400 --> 00:32:35,800 are very different from the|laws that we are used to. 576 00:32:35,900 --> 00:32:39,560 Our daily experiences|are totally different 577 00:32:39,600 --> 00:32:42,200 from anything that you would|see in the quantum world. 578 00:32:42,300 --> 00:32:44,000 The quantum world is crazy. 579 00:32:44,100 --> 00:32:45,700 It's probably the best way to put it. 580 00:32:45,730 --> 00:32:46,800 It's a crazy world. 581 00:32:47,000 --> 00:32:49,460 For nearly 80 years, 582 00:32:49,500 --> 00:32:51,500 quantum mechanics has|successfully claimed 583 00:32:51,600 --> 00:32:54,000 that the strange and bizarre are typical 584 00:32:54,100 --> 00:32:56,200 of how our universeactually behaves 585 00:32:56,300 --> 00:32:57,560 on extremely small scales. 586 00:32:57,600 --> 00:33:01,600 At the scale of everyday|life,we don't directly experience 587 00:33:03,900 --> 00:33:05,700 the weirdness of quantum mechanics. 588 00:33:05,730 --> 00:33:09,100 But here in the Quantum Caf�, 589 00:33:09,200 --> 00:33:11,650 big, everyday things sometimes behave 590 00:33:11,680 --> 00:33:14,240 as if they were microscopically tiny. 591 00:33:14,270 --> 00:33:16,800 And no matter how many times I come here, 592 00:33:16,830 --> 00:33:19,260 I never seem to get used to it. 593 00:33:19,300 --> 00:33:21,700 I'll have an orange juice, please. 594 00:33:21,730 --> 00:33:23,700 I'll try. 595 00:33:23,800 --> 00:33:25,660 "I'll try," she says. 596 00:33:25,700 --> 00:33:29,700 You see, they're not used to people 597 00:33:31,300 --> 00:33:34,100 placing definite orders|here in the Quantum Caf� 598 00:33:34,130 --> 00:33:36,600 because here,everything|is ruled by chance. 599 00:33:36,630 --> 00:33:38,460 While I'd like an orange juice, 600 00:33:38,500 --> 00:33:40,500 there's only a particular probability 601 00:33:40,600 --> 00:33:41,900 that I'll actually get one. 602 00:33:42,000 --> 00:33:46,000 And there's no reason to be disappointed 603 00:33:47,230 --> 00:33:50,660 with one particular outcome or another 604 00:33:50,700 --> 00:33:54,100 because quantum mechanics suggests 605 00:33:54,200 --> 00:33:55,560 that each of the possibilities- 606 00:33:55,600 --> 00:33:58,800 like getting a yellow|juice or a red juice- 607 00:33:58,830 --> 00:34:00,260 may actually happen. 608 00:34:00,300 --> 00:34:02,260 They just happen to happen 609 00:34:02,300 --> 00:34:04,360 in universes that are parallel to ours- 610 00:34:04,400 --> 00:34:07,200 universes that seem as|real to their inhabitants 611 00:34:07,230 --> 00:34:09,660 as our universe seems to us. 612 00:34:09,700 --> 00:34:13,160 If there are a thousand possibilities 613 00:34:13,200 --> 00:34:15,500 and quantum mechanics|cannot with certainty say 614 00:34:15,530 --> 00:34:17,510 which of the thousand it will be, 615 00:34:17,550 --> 00:34:19,500 then all thousand will happen. 616 00:34:19,530 --> 00:34:22,100 Yeah, you can laugh at it 617 00:34:22,200 --> 00:34:23,760 and say,"Well, that has to be wrong. " 618 00:34:23,800 --> 00:34:27,400 But there are so many|other things in physics 619 00:34:27,600 --> 00:34:29,300 which at the time that|people came up with 620 00:34:29,330 --> 00:34:30,600 had to be wrong, but it wasn't. 621 00:34:30,800 --> 00:34:33,250 You have to be a|little careful, I think, 622 00:34:33,280 --> 00:34:35,700 before you say this is clearly wrong. 623 00:34:35,800 --> 00:34:39,800 And even in our own universe, 624 00:34:41,600 --> 00:34:44,160 quantum mechanics says there's a chance 625 00:34:44,200 --> 00:34:48,200 that things we'd ordinarily|think of as impossible 626 00:34:48,230 --> 00:34:50,460 can actually happen. 627 00:34:50,500 --> 00:34:54,250 For example, there's|a chance that particles 628 00:34:54,280 --> 00:34:57,790 can pass right through walls or barriers 629 00:34:57,820 --> 00:35:01,300 that seem impenetrable to you or me. 630 00:35:01,400 --> 00:35:03,060 There's even a chance 631 00:35:03,100 --> 00:35:06,000 that I could pass through|something solid, like a wall. 632 00:35:06,100 --> 00:35:09,000 Now, quantum calculations do show 633 00:35:09,100 --> 00:35:11,900 that the probability for this|to happen in the everyday world 634 00:35:12,000 --> 00:35:14,360 is so small that I'd need to continue 635 00:35:14,400 --> 00:35:16,900 walking into the wall|for nearly an eternity 636 00:35:16,930 --> 00:35:19,400 before having a reasonable|chance of succeeding. 637 00:35:19,500 --> 00:35:23,500 But here, these kind of|things happen all the time. 638 00:35:26,830 --> 00:35:28,260 You have to learn 639 00:35:28,300 --> 00:35:31,700 to abandon those assumptions that|you have about the world 640 00:35:31,800 --> 00:35:34,000 in order to understand|quantum mechanics. 641 00:35:34,100 --> 00:35:38,100 In my gut, in my belly,do|I feel like I have 642 00:35:38,400 --> 00:35:41,400 a deep, intuitive understanding|of quantum mechanics? 643 00:35:41,430 --> 00:35:41,990 No. 644 00:35:42,000 --> 00:35:46,000 And neither did Einstein. 645 00:35:46,100 --> 00:35:50,100 He never lost faith that|the universe behaves 646 00:35:51,200 --> 00:35:53,560 in a certainand predictable way. 647 00:35:53,600 --> 00:35:57,600 The idea that all we can|do is calculate the odds 648 00:35:58,300 --> 00:36:01,650 that things will turn|outone way or another 649 00:36:01,680 --> 00:36:04,960 was something Einstein deeply resisted. 650 00:36:05,000 --> 00:36:09,000 Quantum mechanics says that|you can't know for certain 651 00:36:09,130 --> 00:36:11,160 the outcome of any experiment. 652 00:36:11,200 --> 00:36:14,100 You can only assign|a certain probability 653 00:36:14,130 --> 00:36:16,410 to the outcome of any experiment. 654 00:36:16,450 --> 00:36:19,020 And this Einstein disliked intensely. 655 00:36:19,060 --> 00:36:21,600 He used to say,"God|does not throw dice. " 656 00:36:21,630 --> 00:36:25,630 Yet experiment after experiment 657 00:36:27,300 --> 00:36:29,960 showed Einstein was wrong 658 00:36:30,000 --> 00:36:33,150 and that quantum mechanics|really does describe 659 00:36:33,180 --> 00:36:36,300 how the world works at|the subatomic level. 660 00:36:36,330 --> 00:36:38,960 So quantum mechanics is not a luxury- 661 00:36:39,000 --> 00:36:41,600 something that you can do without. 662 00:36:41,630 --> 00:36:44,160 I mean, why is water the way it is? 663 00:36:44,200 --> 00:36:46,400 Why does light go|straight through water? 664 00:36:46,430 --> 00:36:47,360 Why is it transparent? 665 00:36:47,400 --> 00:36:48,600 Why are other things not transparent? 666 00:36:48,630 --> 00:36:50,360 How do molecules form? 667 00:36:50,400 --> 00:36:53,100 Why are they reacting|the way they react? 668 00:36:53,200 --> 00:36:56,800 The moment that you want|to understand anything 669 00:36:56,900 --> 00:37:00,900 at an atomic level-as|nonintuitive as it is- 670 00:37:01,800 --> 00:37:05,500 at that moment you can only make|progress with quantum mechanics. 671 00:37:05,530 --> 00:37:08,600 Quantum mechanics is|fantastically accurate. 672 00:37:08,700 --> 00:37:12,700 There has never been a|prediction of quantum mechanics 673 00:37:13,430 --> 00:37:17,430 that has contradicted|an observation- never. 674 00:37:17,730 --> 00:37:21,730 By the 1930s, 675 00:37:22,700 --> 00:37:26,400 Einstein's quest for|unification was floundering 676 00:37:26,430 --> 00:37:29,700 while quantum mechanics was unlocking 677 00:37:29,800 --> 00:37:31,500 the secrets of the atom. 678 00:37:31,600 --> 00:37:35,600 Scientists found that|gravity and electromagnetism 679 00:37:36,300 --> 00:37:39,700 are not the only forces|ruling the universe. 680 00:37:39,730 --> 00:37:42,810 Probing the structure of the atom, 681 00:37:42,850 --> 00:37:45,860 they discovered two more forces. 682 00:37:45,900 --> 00:37:49,900 One, dubbed the strong nuclear force, 683 00:37:51,030 --> 00:37:53,060 acts like a super-glue, 684 00:37:53,100 --> 00:37:56,100 holding the nucleus|of every atom together, 685 00:37:56,130 --> 00:37:58,560 binding protons to neutrons. 686 00:37:58,600 --> 00:38:02,600 And the other, called|the weak nuclear force, 687 00:38:03,800 --> 00:38:06,800 allows neutrons to turn into protons, 688 00:38:06,830 --> 00:38:09,800 giving off radiation in the process. 689 00:38:09,830 --> 00:38:12,000 At the quantum level, 690 00:38:12,100 --> 00:38:15,400 the force we're|most familiar with- gravity- 691 00:38:15,430 --> 00:38:18,700 was completely overshadowed by|electromagnetism 692 00:38:18,730 --> 00:38:21,260 and these two new forces. 693 00:38:21,300 --> 00:38:25,300 Now, the strong and weak|forces may seem obscure, 694 00:38:26,100 --> 00:38:27,660 but in one sense at least, 695 00:38:27,700 --> 00:38:31,250 we're all very much|aware of their power. 696 00:38:31,280 --> 00:38:34,800 At 5:29 on the morning of July 16, 1945, 697 00:38:34,900 --> 00:38:37,360 that power was revealed by an act 698 00:38:37,400 --> 00:38:39,200 that would change the course of history. 699 00:38:39,300 --> 00:38:42,600 In the middle of the|desert in New Mexico, 700 00:38:42,700 --> 00:38:44,860 at the top of a steel tower 701 00:38:44,900 --> 00:38:48,900 about a hundred feet above|the top of this monument, 702 00:38:48,930 --> 00:38:51,610 the first atomic bomb was detonated. 703 00:38:51,650 --> 00:38:54,300 It was only about five feet across, 704 00:38:54,400 --> 00:38:57,160 but that bomb packed a punch 705 00:38:57,200 --> 00:39:01,200 equivalent to about 20,000 tons of TNT. 706 00:39:01,630 --> 00:39:05,630 With that powerful explosion, 707 00:39:10,300 --> 00:39:14,300 scientists unleashed the|strong nuclear force- 708 00:39:14,430 --> 00:39:17,260 the force that keeps|neutrons and protons 709 00:39:17,300 --> 00:39:20,800 tightly glued together|inside the nucleus of an atom. 710 00:39:20,830 --> 00:39:23,010 By breaking the bonds of that glue 711 00:39:23,050 --> 00:39:25,200 and splitting the atom apart... 712 00:39:25,300 --> 00:39:29,150 vast, truly unbelievable amounts 713 00:39:29,180 --> 00:39:33,000 of destructive energy were released. 714 00:39:33,100 --> 00:39:37,100 We can still detect|remnants of that explosion 715 00:39:41,700 --> 00:39:44,800 through the other nuclear force-|the weak nuclear force- 716 00:39:44,830 --> 00:39:47,600 because it's responsible|for radioactivity. 717 00:39:47,630 --> 00:39:50,600 And today, more than 50 years later, 718 00:39:50,700 --> 00:39:52,800 the radiation levels|around here are still 719 00:39:52,900 --> 00:39:55,900 about ten times higher than normal. 720 00:39:56,000 --> 00:40:00,000 So although in comparison to|electromagnetism and gravity 721 00:40:01,730 --> 00:40:04,860 the nuclear forces act|over very small scales, 722 00:40:04,900 --> 00:40:08,800 their impact on everyday|life is every bit as profound. 723 00:40:08,900 --> 00:40:12,900 But what about gravity-Einstein's|general relativity? 724 00:40:17,030 --> 00:40:20,500 Where does that fit|in at the quantum level? 725 00:40:20,600 --> 00:40:24,460 Quantum mechanics tells us 726 00:40:24,500 --> 00:40:28,000 how all of nature's forces|work in the microscopic realm 727 00:40:28,030 --> 00:40:30,060 except for the force of gravity. 728 00:40:30,100 --> 00:40:33,900 Absolutely no one could|figure out how gravity operates 729 00:40:34,000 --> 00:40:37,900 when you get down to the size|of atoms and subatomic particles. 730 00:40:37,930 --> 00:40:40,360 That is, no one could figure out 731 00:40:40,400 --> 00:40:43,800 how to put general relativity and quantum mechanics 732 00:40:43,830 --> 00:40:46,060 together into one package. 733 00:40:46,100 --> 00:40:50,100 For decades, every attempt to|describe the force of gravity 734 00:40:54,930 --> 00:40:57,200 in the same languageas|the other forces- 735 00:40:57,230 --> 00:40:59,100 the language of quantum mechanics- 736 00:40:59,200 --> 00:41:01,560 has met with disaster. 737 00:41:01,600 --> 00:41:04,400 You try to put those two|pieces of mathematics together, 738 00:41:04,430 --> 00:41:07,760 they do not coexist peacefully. 739 00:41:07,800 --> 00:41:11,100 You get answers that the probabilities 740 00:41:11,200 --> 00:41:13,100 of the event you're|looking atare infinite. 741 00:41:13,200 --> 00:41:14,360 Nonsense. 742 00:41:14,400 --> 00:41:16,500 It's not profound, it's just nonsense. 743 00:41:16,600 --> 00:41:17,400 It's very ironic, 744 00:41:17,500 --> 00:41:19,400 because it was the first|force to actually be understood 745 00:41:19,430 --> 00:41:22,510 in some decent,quantitative way, 746 00:41:22,550 --> 00:41:25,560 but it still remains split off 747 00:41:25,600 --> 00:41:28,100 and very different from the other ones. 748 00:41:28,200 --> 00:41:31,350 The laws of nature are supposed|to apply everywhere. 749 00:41:31,380 --> 00:41:34,500 So if Einstein's laws are|supposed to apply everywhere 750 00:41:34,600 --> 00:41:36,500 and the laws of quantum mechanics 751 00:41:36,600 --> 00:41:37,760 are supposed to apply everywhere, 752 00:41:37,800 --> 00:41:40,900 well, you can't have|two separate everywheres. 753 00:41:40,930 --> 00:41:44,930 In 1933, after fleeing Nazi Germany, 754 00:41:50,700 --> 00:41:53,400 Einstein settled in|Princeton, New Jersey. 755 00:41:53,500 --> 00:41:55,960 Working in solitude, 756 00:41:56,000 --> 00:41:58,560 he stubbornly continued the quest 757 00:41:58,600 --> 00:42:01,500 he had begun more than a decade earlier 758 00:42:01,530 --> 00:42:05,260 to unite gravity and electromagnetism. 759 00:42:05,300 --> 00:42:08,960 Every few years,headlines appeared 760 00:42:09,000 --> 00:42:11,900 proclaiming Einstein was|on the verge of success. 761 00:42:12,000 --> 00:42:16,000 But most of his colleagues|believed his quest was misguided 762 00:42:16,130 --> 00:42:19,400 and that his best days|were already behind him. 763 00:42:19,500 --> 00:42:21,960 Einstein in his later years 764 00:42:22,000 --> 00:42:26,000 got rather detached from the|work of physics in general 765 00:42:26,300 --> 00:42:28,400 and stopped reading people's papers. 766 00:42:28,430 --> 00:42:30,160 I don't even think he knew 767 00:42:30,200 --> 00:42:32,300 there was such a thing|as the weak nuclear force. 768 00:42:32,330 --> 00:42:34,100 He didn't pay attention to those things. 769 00:42:34,130 --> 00:42:36,460 He kept working on the same problem 770 00:42:36,500 --> 00:42:38,700 that he had started|working on as a younger man. 771 00:42:38,800 --> 00:42:42,800 When the community of|theoretical physicists 772 00:42:43,630 --> 00:42:44,760 begin to probe the atom, 773 00:42:44,800 --> 00:42:48,800 Einstein very definitely|gets left out of the picture. 774 00:42:49,400 --> 00:42:53,400 He in some sense chooses not|to look at the physics 775 00:42:54,700 --> 00:42:55,760 coming from these experiments. 776 00:42:55,800 --> 00:42:59,800 Uh, that means that the|laws of quantum mechanics 777 00:43:00,330 --> 00:43:04,330 play no role in his sort|of further investigations. 778 00:43:04,830 --> 00:43:07,460 He's thought to be 779 00:43:07,500 --> 00:43:10,560 this doddering, sympathetic, old figure 780 00:43:10,600 --> 00:43:14,600 who led an earlier revolution|but somehow fell out of it. 781 00:43:16,030 --> 00:43:20,030 It is as if a general who|was a master of horse cavalry, 782 00:43:21,430 --> 00:43:23,760 who has achieved great|things as a commander 783 00:43:23,800 --> 00:43:26,100 at the beginning of the First World War, 784 00:43:26,200 --> 00:43:30,200 would try to bring|mounted cavalry into play 785 00:43:31,100 --> 00:43:34,800 against the barbed wire,|trenches and machine guns 786 00:43:34,900 --> 00:43:36,760 of the other side. 787 00:43:36,800 --> 00:43:40,800 Albert Einstein died on April 18, 1955. 788 00:43:43,800 --> 00:43:47,800 And for many years it|seemed that Einstein's dream 789 00:43:48,130 --> 00:43:51,000 of unifying the forces in a single theory 790 00:43:51,030 --> 00:43:52,800 died with him. 791 00:43:52,900 --> 00:43:56,200 So the quest for unification 792 00:43:56,230 --> 00:43:59,460 becomes a backwater of physics. 793 00:43:59,500 --> 00:44:03,300 By the time of Einstein's|death in the '50s, 794 00:44:03,330 --> 00:44:07,330 almost no serious physicists 795 00:44:09,600 --> 00:44:12,100 are engaged in this|quest for unification. 796 00:44:12,130 --> 00:44:16,130 In the years since, 797 00:44:20,300 --> 00:44:23,560 physics split into two separate camps: 798 00:44:23,600 --> 00:44:27,600 one that uses general relativity to|study big and heavy objects, 799 00:44:28,030 --> 00:44:31,500 things like stars, galaxies|and the universe as a whole... 800 00:44:31,530 --> 00:44:35,100 And another that uses quantum mechanics 801 00:44:35,130 --> 00:44:37,000 to study the tiniest of objects 802 00:44:37,030 --> 00:44:38,860 like atoms and particles. 803 00:44:38,900 --> 00:44:42,360 This has kind of been|like having two families 804 00:44:42,400 --> 00:44:45,200 that just cannot get along|and never talk to each other... 805 00:44:45,300 --> 00:44:48,150 living under the same roof. 806 00:44:48,180 --> 00:44:50,640 There just seemed to be no way 807 00:44:50,670 --> 00:44:53,100 to combine quantum mechanics... 808 00:44:53,130 --> 00:44:54,960 and general relativity 809 00:44:55,000 --> 00:44:57,300 in a single theory that could describe 810 00:44:57,400 --> 00:44:59,200 the universe on all scales. 811 00:44:59,230 --> 00:45:03,230 Now, in spite of this, 812 00:45:06,200 --> 00:45:09,800 we've made tremendous progress|in understanding the universe. 813 00:45:09,830 --> 00:45:12,960 But there's a catch. 814 00:45:13,000 --> 00:45:16,450 There are strange realms of the cosmos 815 00:45:16,480 --> 00:45:19,690 that will never be fully understood 816 00:45:19,720 --> 00:45:22,760 until we find a unified theory. 817 00:45:22,790 --> 00:45:26,440 And nowhere is this more evident... 818 00:45:26,480 --> 00:45:30,060 than in the depths of a black hole. 819 00:45:30,100 --> 00:45:34,100 A German astronomer|named Karl Schwarzschild 820 00:45:35,500 --> 00:45:39,500 first proposed what we now|call "black holes" in 1916... 821 00:45:40,430 --> 00:45:44,430 while stationed on the|front lines in World War I. 822 00:45:47,100 --> 00:45:51,100 He solved the equations of|Einstein's general relativity 823 00:45:53,730 --> 00:45:57,000 in a new and puzzling way. 824 00:45:57,100 --> 00:46:01,100 Between calculations of|artillery trajectories, 825 00:46:01,500 --> 00:46:05,500 Schwarzschild figured out that|an enormous amount of mass, 826 00:46:06,600 --> 00:46:10,600 like that of a very dense|star concentrated in a small area, 827 00:46:11,630 --> 00:46:15,400 would warp the fabricof|space-time so severely... 828 00:46:15,430 --> 00:46:19,430 that nothing, not even light, 829 00:46:20,200 --> 00:46:24,200 could escape its gravitational pull. 830 00:46:24,280 --> 00:46:28,280 For decades, physicists were skeptical 831 00:46:28,330 --> 00:46:30,360 that Schwarzschild's calculations 832 00:46:30,400 --> 00:46:32,400 were anything more than theory. 833 00:46:32,500 --> 00:46:36,500 But today, satellite telescopes|probing deep into space 834 00:46:38,580 --> 00:46:42,580 are discovering regions with|enormous gravitational pull 835 00:46:44,700 --> 00:46:48,700 that most scientists|believe are black holes. 836 00:46:49,530 --> 00:46:53,530 Schwarzschild's theory now|seems to be reality. 837 00:46:54,330 --> 00:46:57,500 So here's the question. 838 00:46:57,600 --> 00:47:00,060 If you're trying to figure out 839 00:47:00,100 --> 00:47:03,650 what happens in the|depths of a black hole, 840 00:47:03,680 --> 00:47:07,200 where an entire staris|crushed to a tiny speck, 841 00:47:07,230 --> 00:47:10,060 do you use general relativity- 842 00:47:10,100 --> 00:47:12,100 because the staris incredibly heavy- 843 00:47:12,200 --> 00:47:16,200 or quantum mechanics,because|it's incredibly tiny? 844 00:47:16,930 --> 00:47:20,160 Well, that's the problem. 845 00:47:20,200 --> 00:47:24,200 Since the center of a black|hole is both tiny and heavy, 846 00:47:24,580 --> 00:47:28,580 you can't avoid using both|theories at the same time. 847 00:47:28,930 --> 00:47:32,500 And when we try to put the|two theories together 848 00:47:32,530 --> 00:47:33,700 in the realm of black holes... 849 00:47:33,800 --> 00:47:35,900 they conflict, it breaks down. 850 00:47:35,930 --> 00:47:38,160 They give nonsensical predictions, 851 00:47:38,200 --> 00:47:40,400 and the universe is not nonsensical. 852 00:47:40,430 --> 00:47:41,300 It's got to make sense. 853 00:47:41,400 --> 00:47:44,400 Quantum mechanics works|really well for small things, 854 00:47:44,430 --> 00:47:46,800 and general relativity works really well 855 00:47:46,900 --> 00:47:47,700 for stars and galaxies. 856 00:47:47,700 --> 00:47:50,600 But the atoms- the small|things- and the galaxies, 857 00:47:50,630 --> 00:47:52,200 they're part of the same universe, 858 00:47:52,300 --> 00:47:55,000 so there has to be some description 859 00:47:55,030 --> 00:47:55,960 that applies to everything. 860 00:47:56,000 --> 00:47:59,200 So we can't have one description|for atoms and one for stars. 861 00:47:59,230 --> 00:48:03,230 Now, with string theory,we|think we may have found a way 862 00:48:04,250 --> 00:48:08,250 to unite our theory of the|large and our theory of the small 863 00:48:09,310 --> 00:48:13,310 and make sense of the universe at|all scales and all places. 864 00:48:14,330 --> 00:48:18,330 Instead of a multitude of tiny particles, 865 00:48:19,400 --> 00:48:23,400 string theory proclaims|that everything in the universe- 866 00:48:23,930 --> 00:48:25,960 all forces and all matter- 867 00:48:26,000 --> 00:48:29,000 is made of one single ingredient: 868 00:48:29,100 --> 00:48:33,100 tiny vibrating strands of|energy known as strings. 869 00:48:34,230 --> 00:48:37,200 A string can wiggle|in many different ways, 870 00:48:37,230 --> 00:48:39,060 whereas, of course, a point can't. 871 00:48:39,100 --> 00:48:41,900 And the different ways in|which the string wiggles 872 00:48:42,000 --> 00:48:45,200 represent the different|kinds of elementary particles. 873 00:48:45,230 --> 00:48:47,100 It's like a violin string 874 00:48:47,200 --> 00:48:51,200 and it can vibrate just like|violin strings can vibrate. 875 00:48:51,230 --> 00:48:55,200 Each note, if you like,|describes a different particle. 876 00:48:55,230 --> 00:48:58,700 So it has incredible unification power. 877 00:48:58,730 --> 00:49:00,000 It unifies our understanding 878 00:49:00,100 --> 00:49:01,760 of all these different|kinds of particles. 879 00:49:01,800 --> 00:49:05,400 So, unity of the different|forces and particles 880 00:49:05,430 --> 00:49:06,960 is achieved because they all come 881 00:49:07,000 --> 00:49:08,500 from different kinds of vibrations 882 00:49:08,600 --> 00:49:09,760 of the same basic string. 883 00:49:09,800 --> 00:49:13,800 It's a simple idea with|far-reaching consequences. 884 00:49:14,530 --> 00:49:18,530 What string theory does|is it holds out the promise 885 00:49:19,230 --> 00:49:22,300 that, look, we can really|understand questions 886 00:49:22,330 --> 00:49:24,600 that you might not even have thought 887 00:49:24,630 --> 00:49:25,760 were scientific questions, 888 00:49:25,800 --> 00:49:28,700 questions about how the universe began, 889 00:49:28,730 --> 00:49:30,760 why the universe is the way it is 890 00:49:30,800 --> 00:49:32,800 at the most fundamental level. 891 00:49:32,900 --> 00:49:36,000 The idea that a scientific theory 892 00:49:36,100 --> 00:49:38,100 that we already have in our hands 893 00:49:38,130 --> 00:49:40,100 could answer the most basic questions 894 00:49:40,200 --> 00:49:41,760 is extremely seductive. 895 00:49:41,800 --> 00:49:45,800 But this seductive new|theory is also controversial. 896 00:49:48,100 --> 00:49:52,100 Strings- if they exist-are so small 897 00:49:53,300 --> 00:49:56,500 there's little hope of ever seeing one. 898 00:49:56,530 --> 00:49:59,000 String theory and string theorists 899 00:49:59,100 --> 00:49:59,900 do have a real problem. 900 00:50:00,000 --> 00:50:02,060 How do you actually test string theory? 901 00:50:02,100 --> 00:50:05,600 If you can't test it in the way|that we test normal theories, 902 00:50:05,630 --> 00:50:08,100 it's not science, it's philosophy, 903 00:50:08,130 --> 00:50:09,360 and that's a real problem. 904 00:50:09,400 --> 00:50:13,400 If string theory fails to|provide a testable prediction, 905 00:50:14,030 --> 00:50:16,800 then nobody should believe it. 906 00:50:16,830 --> 00:50:19,460 On the other hand, 907 00:50:19,500 --> 00:50:22,700 there's a kind of|elegance to these things, 908 00:50:22,800 --> 00:50:24,360 and given the history 909 00:50:24,400 --> 00:50:27,800 of how theoretical physics|has evolved thus far, 910 00:50:27,900 --> 00:50:31,900 it is totally conceivable that some, 911 00:50:32,600 --> 00:50:36,000 if not all, of these ideas will|turn out to be correct. 912 00:50:36,030 --> 00:50:38,500 I think a hundred years from now, 913 00:50:38,530 --> 00:50:40,400 this particular period, 914 00:50:40,500 --> 00:50:43,760 when most of the brightest|young theoretical physicists 915 00:50:43,800 --> 00:50:47,800 worked on string theory, will|be remembered as a heroic age, 916 00:50:48,530 --> 00:50:52,360 when theorists tried and succeeded 917 00:50:52,400 --> 00:50:56,150 to develop a unified theory|of all the phenomena of nature. 918 00:50:56,180 --> 00:50:59,900 On the other hand, it may be|remembered as a tragic failure. 919 00:51:00,000 --> 00:51:02,800 My guess is that it will|be something like the former 920 00:51:02,830 --> 00:51:03,900 rather than the latter. 921 00:51:04,000 --> 00:51:07,600 Uh... but ask me a hundred years|from now, then I can tell you. 922 00:51:07,630 --> 00:51:11,630 Our understanding of|the universe has come 923 00:51:18,900 --> 00:51:22,400 an enormously long way during|the last three centuries. 924 00:51:22,430 --> 00:51:26,430 Just consider this. 925 00:51:26,900 --> 00:51:30,160 Isaac Newton, who was perhaps 926 00:51:30,200 --> 00:51:32,500 the greatest scientist of all time, 927 00:51:32,600 --> 00:51:36,600 once said, "I have been like|a boy playing on the seashore, 928 00:51:37,000 --> 00:51:39,760 "diverting myself in,|now and then, finding 929 00:51:39,800 --> 00:51:42,860 "a smoother pebbleor a|prettier shell than usual, 930 00:51:42,900 --> 00:51:46,900 while the great ocean of truth|lay before me all undiscovered. " 931 00:51:48,400 --> 00:51:52,400 And yet, 250 years later, 932 00:51:54,200 --> 00:51:57,600 Albert Einstein, who was|Newton's true successor, 933 00:51:57,700 --> 00:52:01,600 was able to seriously|suggest that this vast ocean, 934 00:52:01,630 --> 00:52:04,700 all the laws of nature, might be reduced 935 00:52:04,800 --> 00:52:06,660 to a few fundamental ideas 936 00:52:06,700 --> 00:52:10,600 expressed by a handful|of mathematical symbols. 937 00:52:10,700 --> 00:52:14,700 And today, a half-century|after Einstein's death, 938 00:52:18,430 --> 00:52:20,760 we may at last be on the verge 939 00:52:20,800 --> 00:52:24,800 of fulfilling his dream of|unification with string theory. 940 00:52:35,530 --> 00:52:39,530 But where did this daring and|strange new theory come from? 941 00:52:45,300 --> 00:52:49,300 How does string theory achieve|the ultimate unification 942 00:52:50,900 --> 00:52:53,700 of the laws of the large|and the laws of the small? 943 00:52:52,730 --> 00:52:56,460 And how will we know|if it's right or wrong? 944 00:52:55,500 --> 00:52:59,200 No experiment can ever|check up what's going on 945 00:52:59,230 --> 00:53:01,600 at the distances that are being studied. 946 00:53:01,630 --> 00:53:03,800 The theory is permanently safe. 947 00:53:03,900 --> 00:53:07,800 Is that a theory of|physics or a philosophy? 948 00:53:07,830 --> 00:53:09,410 It isn't written in the stars 949 00:53:09,450 --> 00:53:11,000 that we're going to succeed, 950 00:53:11,100 --> 00:53:13,600 but in the end, we hope we will have 951 00:53:13,630 --> 00:53:16,100 a single theory that governs everything. 952 00:53:17,400 --> 00:53:21,400 SUBTITLED BY ANDROMEDA 69304

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