0 00:00:28,995 --> 00:00:30,792 In the last hundred years, 1 00:00:31,031 --> 00:00:35,559 our understanding of the universe has advanced far further 2 00:00:35,702 --> 00:00:37,932 than in previous centuries. 3 00:00:39,572 --> 00:00:41,870 We have discovered that the universe 4 00:00:42,008 --> 00:00:46,809 and time itself had a beginning fifteen billion years ago. 5 00:00:47,881 --> 00:00:52,614 There was a cosmic explosion of energy, called the big bang. 6 00:00:55,188 --> 00:00:58,157 The energy produced all of the matter in the universe, 7 00:00:58,324 --> 00:01:01,953 from stars and galaxies to our own planet, 8 00:01:02,162 --> 00:01:03,823 and even ourselves. 9 00:01:04,531 --> 00:01:10,367 Yet one guestion still needs an answers: How did the big bang begin? 10 00:01:12,005 --> 00:01:16,305 We need to know the laws that held at the moment of creation, 11 00:01:16,443 --> 00:01:19,412 when the universe sprang into existence. 12 00:01:19,913 --> 00:01:23,371 Are these initial laws over and above the laws 13 00:01:23,483 --> 00:01:26,247 that tell us how the universe evolves? 14 00:01:26,786 --> 00:01:31,883 Or is there a theory of everything that governs the universe at all times 15 00:01:32,058 --> 00:01:34,925 and determines how it begins and develops? 16 00:01:54,914 --> 00:01:58,179 Atlantic City is a giant playground. 17 00:01:58,852 --> 00:01:59,784 But for many, 18 00:01:59,886 --> 00:02:03,617 the fading attractions of old Atlantic City are less fascinating 19 00:02:03,723 --> 00:02:07,318 than the uncertainties of its modern casinos. 20 00:02:17,470 --> 00:02:20,803 Sidney Coleman knows it's the same with physics 21 00:02:22,775 --> 00:02:26,267 Physics starts out by trying to explain the sort of phenomena 22 00:02:26,379 --> 00:02:29,644 that occur in everyday life - balls bouncing 23 00:02:29,749 --> 00:02:32,616 and planets grounding around the sun, and all that stuff. 24 00:02:33,620 --> 00:02:36,555 And that's also pretty much the sort of stuff that, 25 00:02:36,656 --> 00:02:39,284 er, you encounter in everyday life, 26 00:02:39,392 --> 00:02:42,384 and your tacit assumptions about those things 27 00:02:42,562 --> 00:02:47,090 and how they behave are deeply embedded in the language of everyday speech. 28 00:02:47,333 --> 00:02:50,268 That's how the language of everyday speech developed. 29 00:03:04,751 --> 00:03:08,778 But physics has now probed beyond the familiar. 30 00:03:10,390 --> 00:03:13,257 Theorists like Sidney Coleman spend their days 31 00:03:13,359 --> 00:03:17,386 making long imaginary journeys into strange worlds, 32 00:03:17,630 --> 00:03:20,098 far removed from everyday life. 33 00:03:30,710 --> 00:03:34,476 As physics develops and physicists want to find out more and more, 34 00:03:34,647 --> 00:03:37,878 they try and understand physics which reveals itself 35 00:03:37,984 --> 00:03:42,045 only under extreme conditions on the inside of an atom, 36 00:03:42,355 --> 00:03:44,482 in a high-energy accelerator, 37 00:03:44,657 --> 00:03:48,525 in a guasar, at the, during the beginning of the universe 38 00:03:49,128 --> 00:03:51,323 Now it would be really remarkable 39 00:03:51,431 --> 00:03:54,628 if the concepts of everyday speech continued to be valid 40 00:03:54,767 --> 00:03:58,362 when we extend the universe of study so enormously. 41 00:03:58,738 --> 00:04:00,467 It's only natural that, 42 00:04:00,573 --> 00:04:03,736 as we get farther and farther from everyday experience, 43 00:04:03,943 --> 00:04:06,810 the theories we have to describe all this new stuff, 44 00:04:06,913 --> 00:04:08,676 in addition to everyday experience, 45 00:04:08,848 --> 00:04:10,782 should look less and less intuitive. 46 00:04:10,883 --> 00:04:14,580 Why should your intuitions have developed to be good inside a guasar? 47 00:04:14,687 --> 00:04:17,850 Your ancestors did not spend any time inside guasars. 48 00:04:19,659 --> 00:04:21,126 So, things seem to get, 49 00:04:21,227 --> 00:04:22,285 from our viewpoint, 50 00:04:22,395 --> 00:04:25,831 our earth-bound viewpoint, stranger and stranger. 51 00:04:28,768 --> 00:04:33,102 One thing we now accept is that the universe is expanding. 52 00:04:33,773 --> 00:04:35,832 But if it is getting bigger with time, 53 00:04:36,242 --> 00:04:39,075 then it must once have been very small. 54 00:04:40,680 --> 00:04:44,377 When you trace the evolution of the universe backwards in time, 55 00:04:44,584 --> 00:04:50,147 you inevitably find yourself being pushed towards the physics of the very small. 56 00:04:56,763 --> 00:05:00,529 This small world has its own strange language. 57 00:05:04,070 --> 00:05:05,560 And it's at this scale, 58 00:05:05,738 --> 00:05:08,536 millions of times smaller than a single atom, 59 00:05:08,775 --> 00:05:11,209 that the universe must have begun. 60 00:05:13,346 --> 00:05:19,216 The study of these subatomic particles is called guantum mechanics. 61 00:05:35,201 --> 00:05:36,862 Two foundation stones, 62 00:05:36,969 --> 00:05:40,666 really, on which we've built the current modern picture of the universe 63 00:05:40,773 --> 00:05:46,234 and the matter in it are guantum mechanics and general relativity. 64 00:05:49,082 --> 00:05:52,313 Einstein was instrumental in both of those theories, 65 00:05:52,418 --> 00:05:57,515 he was a founder of guantum theory and the sole inventor of general relativity, 66 00:05:58,024 --> 00:06:00,857 and the picture that they give us of the universe is, 67 00:06:01,060 --> 00:06:01,992 is a very good one, 68 00:06:02,095 --> 00:06:05,121 in the sense we can make a lot of predictions 69 00:06:05,331 --> 00:06:07,094 and explain a lot of phenomena, 70 00:06:07,333 --> 00:06:10,769 er, but the picture is really only partial in many ways, 71 00:06:11,037 --> 00:06:13,801 and one of the problems is that the two theories, 72 00:06:13,906 --> 00:06:15,737 in fact, don't fit together. 73 00:06:16,442 --> 00:06:18,842 Einstein's theory of general relativity 74 00:06:18,945 --> 00:06:22,244 describes the large-scale universe we see today. 75 00:06:22,815 --> 00:06:27,275 Quantum mechanics describes the behaviour of things smaller than atoms. 76 00:06:27,487 --> 00:06:31,048 As small as the universe was when it first formed. 77 00:06:31,557 --> 00:06:35,721 A complete description of the universe has to embrace everything, 78 00:06:35,962 --> 00:06:39,363 from the tiniest particle to the largest galaxy. 79 00:06:39,565 --> 00:06:42,125 The two theories have to match up. 80 00:06:43,403 --> 00:06:46,634 Einstein believed that he could find a way to make them fit, 81 00:06:46,739 --> 00:06:51,608 Because the methods that he had applied to problems in physics 82 00:06:51,711 --> 00:06:53,303 before had always worked, 83 00:06:53,413 --> 00:06:56,814 he'd been very successful in unifying things, 84 00:06:56,916 --> 00:06:58,577 he trusted his instincts, 85 00:06:58,718 --> 00:07:01,983 so his instinct was that there should be a theory 86 00:07:02,088 --> 00:07:04,784 which described the two theories together. 87 00:07:06,426 --> 00:07:07,393 At the time, 88 00:07:07,493 --> 00:07:12,123 Einstein was the only one thinking that the two theories could be unified. 89 00:07:13,566 --> 00:07:17,468 Isolated by the scientific community, he worked on. 90 00:07:18,371 --> 00:07:19,804 He spent decades on this work. 91 00:07:19,906 --> 00:07:21,999 He worked, basically, alone, 92 00:07:22,175 --> 00:07:25,804 I think that no-one else shared his view, 93 00:07:26,012 --> 00:07:29,539 er, that this was the way to go, in unification. 94 00:07:30,349 --> 00:07:31,714 So he was very solitary, 95 00:07:31,918 --> 00:07:36,150 and he was working by himself up until the day he died. 96 00:07:39,392 --> 00:07:42,054 When Einstein died, in 1955, 97 00:07:42,328 --> 00:07:48,062 half-finished notes describing a theory of unification were discovered by his bed 98 00:07:49,101 --> 00:07:51,695 He had failed to achieve his dream. 99 00:07:58,077 --> 00:08:00,045 But Einstein was ahead of his time. 100 00:08:01,848 --> 00:08:02,712 Forty years later, 101 00:08:02,815 --> 00:08:06,683 the importance of his lone guest has become recognised. 102 00:08:12,091 --> 00:08:15,993 Now, theorists everywhere are searching for a single eguation 103 00:08:16,162 --> 00:08:19,825 to describe the workings of the entire universe 104 00:08:22,435 --> 00:08:25,598 What they want is a theory of everything. 105 00:08:31,410 --> 00:08:35,278 At the beginning, the universe is a central point. 106 00:08:36,749 --> 00:08:39,616 The next instant, it is enormous. 107 00:08:41,754 --> 00:08:43,654 To understand this properly, 108 00:08:43,856 --> 00:08:45,756 we need a theory of everything, 109 00:08:45,925 --> 00:08:48,894 which is still just beyond our grasp. 110 00:08:51,397 --> 00:08:54,366 However, we already have some ideas 111 00:08:54,534 --> 00:08:59,938 why the expansion of the early universe was precisely what it was. 112 00:09:08,814 --> 00:09:11,874 There are already a number of mathematical eguations 113 00:09:12,051 --> 00:09:15,782 which begin to describe how the universe must have grown. 114 00:09:18,724 --> 00:09:22,558 They have been carefully built up from the evidence we've now glimpsed 115 00:09:22,695 --> 00:09:26,688 Of what conditions in the early universe must have been like. 116 00:09:27,934 --> 00:09:31,370 It is only by constantly matching theory and observation 117 00:09:31,537 --> 00:09:33,937 that a clearer picture can emerge. 118 00:09:35,641 --> 00:09:37,108 Giant particle accelerators, 119 00:09:37,209 --> 00:09:41,737 such as SLAC, in California, smash atoms into each other. 120 00:09:42,782 --> 00:09:45,910 These explosive collisions create energies, temperatures, 121 00:09:46,018 --> 00:09:48,213 and pressures which can be measured. 122 00:09:49,021 --> 00:09:53,720 The same measurable conditions must have existed in the early universe. 123 00:09:53,859 --> 00:09:54,985 In the 1970s, 124 00:09:55,161 --> 00:09:59,291 scientists began to tackle the unbelievable mathematical balance 125 00:09:59,398 --> 00:10:02,265 necessary for our universe to exist. 126 00:10:04,203 --> 00:10:07,400 What was always needed, and nobody had really pointed this out, 127 00:10:07,640 --> 00:10:10,165 was that you had to assume that the expansion rate of the early universe 128 00:10:10,276 --> 00:10:12,608 was tuned almost exactly right. 129 00:10:12,845 --> 00:10:15,279 That is, almost exactly the right expansion rate 130 00:10:15,381 --> 00:10:18,077 so that the universe would be just on the verge 131 00:10:18,250 --> 00:10:21,413 of eternal expansion versus eventual collapse, 132 00:10:21,587 --> 00:10:24,181 er, if one talks about the universe at a time 133 00:10:24,290 --> 00:10:26,315 of about one second after the big bang, 134 00:10:26,492 --> 00:10:27,618 er, this tuning, 135 00:10:27,727 --> 00:10:31,788 this precise fixing of the expansion rate had to be done to an accuracy 136 00:10:31,897 --> 00:10:33,797 of about fifteen decimal places. 137 00:10:33,933 --> 00:10:37,334 If the universe just expanded one part in the fifteenth decimal place 138 00:10:37,436 --> 00:10:38,869 faster than we thought it had, 139 00:10:38,971 --> 00:10:42,304 it would fly apart without galaxies ever having a chance to form, 140 00:10:42,541 --> 00:10:45,237 er, if the universe at one second after the big bang were. 141 00:10:45,344 --> 00:10:48,541 Expanding with one number less in the fifteenth decimal place 142 00:10:48,748 --> 00:10:49,840 than what we thought, 143 00:10:49,949 --> 00:10:51,109 then the universe would collapse 144 00:10:51,217 --> 00:10:53,777 before galaxies had ever had a chance to form. 145 00:10:53,919 --> 00:10:55,181 To make the universe work, 146 00:10:55,321 --> 00:10:58,119 the universe had to be perched just on this borderline 147 00:11:03,896 --> 00:11:06,888 Guth was puzzled that our universe should be the product 148 00:11:06,999 --> 00:11:09,365 of such a magical eguilibrium, 149 00:11:09,669 --> 00:11:12,797 slowly growing in perfectly balanced expansion 150 00:11:12,938 --> 00:11:16,897 for the last fifteen thousand million years. 151 00:11:20,312 --> 00:11:24,942 Alan Guth had managed to grapple with mathematics of extraordinary complexity. 152 00:11:25,484 --> 00:11:26,610 Yet, in many ways, 153 00:11:26,752 --> 00:11:29,084 what he was really doing was responding 154 00:11:29,188 --> 00:11:32,817 to the simple intuitive guestions of a child. 155 00:11:45,905 --> 00:11:47,236 When I was still a kid, 156 00:11:47,373 --> 00:11:48,772 I asked myself the guestion, 157 00:11:48,974 --> 00:11:50,669 well, how would it happen 158 00:11:50,810 --> 00:11:56,248 that in different parts of the universe expansion started simultaneously? 159 00:11:56,449 --> 00:11:58,110 Who gave the signal? 160 00:11:58,217 --> 00:11:59,582 How can I understand it? 161 00:11:59,719 --> 00:12:03,348 And then I thought that maybe when I will grow older I will open the books 162 00:12:03,456 --> 00:12:07,392 which are written by clever professors and I will find out the answer. 163 00:12:09,261 --> 00:12:10,057 When I grew older, 164 00:12:10,162 --> 00:12:13,393 I found that people did not know that the guestion exists. 165 00:12:14,800 --> 00:12:16,290 Unknown to Alan Guth, 166 00:12:16,502 --> 00:12:20,336 a Russian called Andrei Linde was also tackling the problem 167 00:12:20,439 --> 00:12:23,033 of expansion in the early universe 168 00:12:25,511 --> 00:12:30,039 During the last fifteen years we've learned the guestion can be answered. 169 00:12:33,219 --> 00:12:35,380 Linde now lives in California. 170 00:12:35,688 --> 00:12:36,950 But in the 1970s, 171 00:12:37,123 --> 00:12:40,286 he and Guth were working on opposite sides of the world, 172 00:12:40,493 --> 00:12:44,293 on an idea that came to be known as 'inflation'. 173 00:12:46,398 --> 00:12:48,730 So, would you give me a glass of water. 174 00:12:49,401 --> 00:12:54,395 Inflation suggested a way for the right kind of expansion. 175 00:12:58,010 --> 00:13:00,877 Lf, somehow, energy could be trapped in a vacuum, 176 00:13:01,213 --> 00:13:04,444 it would naturally expand like a number of bubbles being, 177 00:13:04,550 --> 00:13:06,450 released all at once. 178 00:13:09,121 --> 00:13:11,646 Perhaps these bubbles could join up together 179 00:13:11,791 --> 00:13:14,726 and rapidly expand as one vast bubble, 180 00:13:14,894 --> 00:13:18,762 producing all the symmetry needed for our universe to grow smoothly 181 00:13:18,864 --> 00:13:23,995 and guickly expanding evenly in all directions. 182 00:13:37,116 --> 00:13:38,344 Linde, in Moscow, 183 00:13:38,517 --> 00:13:43,284 and Guth in California guite separately had the same inspiration. 184 00:13:43,856 --> 00:13:48,520 They needed to do detailed calculations to see if the idea worked out. 185 00:13:58,704 --> 00:14:01,400 In 1979, on a December evening, 186 00:14:01,607 --> 00:14:05,270 Guth opened a notebook and started to write. 187 00:14:05,878 --> 00:14:08,972 I had not yet calculated everything through that night, 188 00:14:09,114 --> 00:14:12,049 enough to convince myself that it was fascinating idea 189 00:14:12,151 --> 00:14:13,641 and that it would probably work. 190 00:14:13,886 --> 00:14:15,649 The next morning I raced back to SLAC, 191 00:14:15,754 --> 00:14:18,848 and actually I kept track of my personal biking records to SLAC, 192 00:14:18,958 --> 00:14:20,516 and I set a new record that morning, 193 00:14:20,659 --> 00:14:21,717 er, once I got there 194 00:14:21,827 --> 00:14:24,625 I whipped out my notebook and started continuing the calculations, 195 00:14:25,231 --> 00:14:26,493 and by, I guess, the end of the morning, 196 00:14:26,599 --> 00:14:28,658 I convinced myself that it did fit together. 197 00:14:33,706 --> 00:14:37,665 Andrei Linde had also started his own calculations. 198 00:14:40,646 --> 00:14:42,341 But as he worked through the detail, 199 00:14:42,548 --> 00:14:47,178 it seemed as though inflation theory couldn't actually work in practice. 200 00:14:48,354 --> 00:14:52,120 In California, Guth encountered the same problem. 201 00:14:53,192 --> 00:14:54,682 As I continued to work on inflation, 202 00:14:54,793 --> 00:14:57,785 I did however discover that there was a serious problem in the way 203 00:14:57,897 --> 00:14:59,797 that inflation finally ended. 204 00:15:02,668 --> 00:15:04,795 It happened just like water boils, 205 00:15:05,137 --> 00:15:06,229 a bubble would form here, 206 00:15:06,338 --> 00:15:07,566 a bubble would form there, 207 00:15:07,773 --> 00:15:09,570 the bubbles would grow and collide, 208 00:15:09,842 --> 00:15:15,405 and form an incredible morass of matter with tremendous non-uniformities in it. 209 00:15:16,649 --> 00:15:17,308 We look at, 210 00:15:17,416 --> 00:15:20,180 in fact, nothing whatever like our universe looks like. 211 00:15:21,420 --> 00:15:24,548 This was a serious problem that clearly reguired modification. 212 00:15:29,561 --> 00:15:30,152 Thank you. 213 00:15:30,262 --> 00:15:31,251 You're welcome, Sir. 214 00:15:31,363 --> 00:15:34,662 But Guth went ahead and published his theory. 215 00:15:35,067 --> 00:15:39,003 Even with its flaws, inflation caused a sensation. 216 00:15:47,980 --> 00:15:50,471 But Linde was worried when he read Guth's paper. 217 00:15:50,983 --> 00:15:54,578 He felt he had to find a solution to the theory's imperfections, 218 00:15:54,787 --> 00:15:57,153 to give inflation respectability. 219 00:16:02,828 --> 00:16:04,455 I don't know whether you know or not, 220 00:16:04,563 --> 00:16:05,962 but I had an ulcer, 221 00:16:06,198 --> 00:16:08,598 which was induced by the work, 222 00:16:08,767 --> 00:16:13,534 in some sense, because when I heard about all these ideas, 223 00:16:13,639 --> 00:16:16,369 er, and I, I was really literally thinking in these terms 224 00:16:16,475 --> 00:16:22,812 that God could not be so stupid to lose this opportunity to make the world, 225 00:16:22,948 --> 00:16:24,916 er, in such a economical way, 226 00:16:25,117 --> 00:16:28,678 and when I found a solution, the ulcer has gone. 227 00:16:30,656 --> 00:16:34,114 Well, er, so sometimes physics help. 228 00:16:35,861 --> 00:16:38,022 Linde's new idea was simple. 229 00:16:38,764 --> 00:16:44,725 What if just one bubble of energy inflated all by itself into our universe? 230 00:16:46,271 --> 00:16:47,863 It was about eleven at night, 231 00:16:48,040 --> 00:16:50,372 and I could not keep myself from, 232 00:16:50,476 --> 00:16:56,108 well, this feeling of happiness and I came to my wife and eventually awake her 233 00:16:56,215 --> 00:16:56,977 and I told her, 234 00:16:57,082 --> 00:17:00,210 look, it seems that I know how our universe could have emerged. 235 00:17:01,954 --> 00:17:03,251 I first announced it, 236 00:17:03,489 --> 00:17:05,354 new inflationist scenario, 237 00:17:05,591 --> 00:17:08,856 at, in the meeting of guantum gravity in Moscow, 238 00:17:09,061 --> 00:17:13,225 which occurred in October '81, and at that time, 239 00:17:13,465 --> 00:17:16,628 many very good physicist in Moscow, 240 00:17:16,902 --> 00:17:20,838 and the star of the meeting was Steve Hawking. 241 00:17:21,673 --> 00:17:24,904 I gave a seminar with Andrei translating. 242 00:17:25,744 --> 00:17:30,772 When I said there was a difficulty with Guth's idea of bubbles in collision, 243 00:17:31,050 --> 00:17:35,180 Andrei said that the whole universe could be a single bubble. 244 00:17:36,388 --> 00:17:40,415 I objected, because the bubble would have been bigger 245 00:17:40,526 --> 00:17:42,289 than the universe at the time. 246 00:17:44,096 --> 00:17:45,427 In the middle of his talk, 247 00:17:45,564 --> 00:17:46,929 he told that, well, 248 00:17:47,032 --> 00:17:50,195 there was a very interesting idea of Andrei Linde recently 249 00:17:50,302 --> 00:17:52,964 this was just my talk the previous day, 250 00:17:53,205 --> 00:17:55,173 and I was all my head in it's translating it, 251 00:17:55,274 --> 00:17:58,437 and then he says but but this model, 252 00:17:58,544 --> 00:18:01,775 this idea does not work, and let me explain why. 253 00:18:01,947 --> 00:18:03,915 And he start talking and talking 254 00:18:04,083 --> 00:18:06,108 and I'm translating it, 255 00:18:06,251 --> 00:18:07,809 and for a half an hour, 256 00:18:07,920 --> 00:18:10,787 in the face of all the institute, 257 00:18:10,889 --> 00:18:14,723 I was explaining them why new inflation just simply cannot work. 258 00:18:14,960 --> 00:18:16,587 In front of his Russian peers, 259 00:18:16,795 --> 00:18:19,229 Linde's new theory had been demolished. 260 00:18:19,631 --> 00:18:21,929 But he was determined to continue the debate. 261 00:18:22,634 --> 00:18:23,532 And then I asked him, 262 00:18:23,635 --> 00:18:26,627 would you like to actually to understand the details of this, 263 00:18:26,738 --> 00:18:28,069 and he told me, sure, 264 00:18:28,240 --> 00:18:30,208 and then we disappeared for two hours, 265 00:18:30,309 --> 00:18:32,869 all the institute was trying to catch Steve everywhere, 266 00:18:33,011 --> 00:18:34,410 and the famous physicist disappeared, 267 00:18:34,513 --> 00:18:36,378 the whole institute was in panic. 268 00:18:38,383 --> 00:18:41,910 Linde and Guth had given us an important idea. 269 00:18:42,387 --> 00:18:47,450 Inflation accounts so neatly for the way the universe has to expand. 270 00:18:47,593 --> 00:18:50,960 I'm sure it must be part of the final picture. 271 00:18:51,897 --> 00:18:56,857 But inflation by itself does not explain the start of the universe 272 00:18:57,903 --> 00:19:00,929 We still need a theory of everything for that. 273 00:19:02,207 --> 00:19:05,574 But in applying the theory to the beginning of the universe 274 00:19:05,744 --> 00:19:09,441 would be difficult, because my own work had shown 275 00:19:09,615 --> 00:19:13,176 that the eguations would break down at the big bang. 276 00:19:15,387 --> 00:19:18,948 You can take Einstein's eguations and run them backwards in time, 277 00:19:19,291 --> 00:19:20,622 not for a real universe, 278 00:19:20,726 --> 00:19:21,988 which is awful complicated, 279 00:19:22,094 --> 00:19:23,652 full of lumps and irregularities, 280 00:19:23,762 --> 00:19:25,855 but for a simplified model of the universe, 281 00:19:26,064 --> 00:19:26,723 where matter is, 282 00:19:26,832 --> 00:19:30,427 distributed smoothly and uniformly throughout the universe, 283 00:19:30,969 --> 00:19:34,063 and when you did run it backwards in time, you found, 284 00:19:34,339 --> 00:19:39,208 eventually, there was a point in which everything came together at a single point 285 00:19:39,745 --> 00:19:42,578 where gravitational fields became infinitely strong, 286 00:19:42,681 --> 00:19:45,309 energy densities became infinitely high, 287 00:19:45,517 --> 00:19:47,678 technically we call it a singularity. 288 00:19:51,423 --> 00:19:56,588 The universe at its birth needed to have some fluctuations in density 289 00:19:56,695 --> 00:20:00,290 and velocity to enable particles to be formed. 290 00:20:02,501 --> 00:20:07,666 But the maths of the singularity won't predict any such fluctuations. 291 00:20:08,340 --> 00:20:10,740 In fact, they won't predict anything at all. 292 00:20:11,743 --> 00:20:17,147 What happens at a point of singularity becomes a matter of pure speculation. 293 00:20:18,850 --> 00:20:20,681 Physicists like to solve eguations, 294 00:20:20,786 --> 00:20:23,653 they like to say, if this is the way things are now, 295 00:20:23,822 --> 00:20:25,847 this is the way they'll be a year from now. 296 00:20:27,859 --> 00:20:29,087 Once you hit a singularity, 297 00:20:29,194 --> 00:20:30,058 you can't do that, 298 00:20:30,162 --> 00:20:32,892 the eguations blow up and you don't know what to do with them. 299 00:20:34,866 --> 00:20:38,324 This is disturbing, people don't like singularities. 300 00:20:41,039 --> 00:20:45,703 The best bet for solving the problem looked like being guantum mechanics. 301 00:20:46,812 --> 00:20:49,940 Quantum mechanics is probably the strangest thing human minds 302 00:20:50,048 --> 00:20:51,379 have ever thought up. 303 00:20:53,852 --> 00:20:58,016 I think if a thousand philosophers were to work for a thousand years, 304 00:20:58,223 --> 00:21:01,056 trying to think of something of maximum strangeness, 305 00:21:01,326 --> 00:21:05,319 they wouldn't have thought up anything as strange as guantum mechanics. 306 00:21:07,532 --> 00:21:11,764 At the heart of guantum mechanics is the idea of chance. 307 00:21:12,271 --> 00:21:15,104 It's called the uncertainty principle. 308 00:21:17,576 --> 00:21:19,942 If a subatomic particle isn't moving, 309 00:21:20,178 --> 00:21:21,975 it's too small to detect. 310 00:21:22,781 --> 00:21:26,615 But there are ways to trace the path of a moving particle. 311 00:21:28,387 --> 00:21:33,086 You can never find out with precision where anything so small really is, 312 00:21:33,558 --> 00:21:37,119 but you can have a very good idea of its probable position. 313 00:21:38,497 --> 00:21:39,691 This probability, 314 00:21:39,865 --> 00:21:41,662 the principle of uncertainty, 315 00:21:41,800 --> 00:21:43,597 does seem to work. 316 00:21:44,569 --> 00:21:45,593 Strange as it is, 317 00:21:45,704 --> 00:21:47,934 it is apparently the way the universe works, 318 00:21:48,240 --> 00:21:50,174 that enables us to make predictions 319 00:21:50,275 --> 00:21:54,939 about all sorts of processes involving atoms or elementary particles colliding, 320 00:21:55,113 --> 00:21:59,948 that are verified by experiment to amazing degrees of accuracy. 321 00:22:03,922 --> 00:22:07,722 The problem is that these laws of uncertainty only seem to make sense 322 00:22:07,826 --> 00:22:10,693 of the universe at its moment of creation. 323 00:22:12,197 --> 00:22:15,894 They can't be applied to the big universe we now experience, 324 00:22:16,201 --> 00:22:18,999 a universe described with incredible accuracy 325 00:22:19,137 --> 00:22:22,231 by Einstein's theory of general relativity. 326 00:22:23,608 --> 00:22:26,702 A lot of people have been trying to combine guantum mechanics 327 00:22:26,812 --> 00:22:28,871 with gravity over the years, 328 00:22:29,114 --> 00:22:33,141 a guantum mechanical replacement or Einstein's general relativity. 329 00:22:37,522 --> 00:22:41,322 I wanted to resolve the problem of the singularity. 330 00:22:41,727 --> 00:22:47,290 After all, I was largely responsible for raising it in the first place. 331 00:22:48,233 --> 00:22:51,100 Maybe one could choose a path around it. 332 00:22:52,904 --> 00:22:55,896 Hawking saw that the uncertainty that came 333 00:22:56,007 --> 00:22:58,032 when you tried to combine guantum mechanics 334 00:22:58,143 --> 00:23:01,203 and gravity was in fact as escape route, 335 00:23:01,313 --> 00:23:04,009 and can be used to get away from the, 336 00:23:04,116 --> 00:23:06,084 avoid the singularity problem, 337 00:23:06,184 --> 00:23:08,812 which he himself had done so much to raise. 338 00:23:09,287 --> 00:23:10,982 In a remarkable paper, 339 00:23:11,156 --> 00:23:13,624 done in collaboration with James Hartle, 340 00:23:13,992 --> 00:23:17,553 er, Hawking was able to solve a very, 341 00:23:17,662 --> 00:23:20,756 very simplified model of the universe 342 00:23:22,200 --> 00:23:25,761 Jim Hartle and I showed how a universe like our own 343 00:23:25,937 --> 00:23:29,464 could be born without the troublesome singularity. 344 00:23:31,209 --> 00:23:35,543 It involved the use of what is called imaginary time. 345 00:23:36,915 --> 00:23:39,406 This may sound like science fiction, 346 00:23:39,551 --> 00:23:45,581 but it is a well-defined scientific concept that science fiction borrowed. 347 00:23:47,692 --> 00:23:50,217 The idea was that in imaginary time, 348 00:23:50,495 --> 00:23:52,690 the universe has no boundary, 349 00:23:53,198 --> 00:23:54,859 no beginning or end, 350 00:23:55,934 --> 00:24:00,633 it just curls round on itself like the surface of the earth. 351 00:24:03,475 --> 00:24:07,673 It was a complete guantum mechanical description of everything 352 00:24:07,779 --> 00:24:13,581 that could be said about this simplified model of the universe, 353 00:24:14,786 --> 00:24:17,220 and it had no singularities. 354 00:24:19,090 --> 00:24:21,684 It's possible that guantum mechanics is the answer 355 00:24:21,793 --> 00:24:23,260 to the problem of the singularity. 356 00:24:30,669 --> 00:24:34,298 I have to make it clear that the no-boundary universe 357 00:24:34,473 --> 00:24:40,309 is just a proposal, but it has some interesting implications. 358 00:24:41,379 --> 00:24:46,681 Without boundaries, the universe has no beginning and no end. 359 00:24:47,486 --> 00:24:50,478 We don't have to explain its creation. 360 00:24:50,789 --> 00:24:57,888 The universe simply exists, but the conseguences of the no-boundary proposal 361 00:24:58,029 --> 00:25:03,399 cannot be worked out fully without a complete guantum theory of gravity 362 00:25:03,568 --> 00:25:08,267 that will unite general relativity and guantum mechanics. 363 00:25:09,074 --> 00:25:12,703 We are back to the search for a theory of everything 364 00:25:23,622 --> 00:25:26,420 In 1985, a new theory emerged, 365 00:25:26,558 --> 00:25:29,891 which raised hopes that the search might soon be over. 366 00:25:31,229 --> 00:25:33,959 You're tuned to WBAI, 99.5 FM, 367 00:25:34,065 --> 00:25:34,929 on your dial, 368 00:25:35,033 --> 00:25:38,594 coming up next - Explorations with Dr Michio Kaku. 369 00:25:39,037 --> 00:25:42,200 Welcome. This is Exploration. 370 00:25:42,474 --> 00:25:45,602 This is Dr Michio Kaku, Professor of Theoretical Physics, 371 00:25:45,710 --> 00:25:47,871 and this is a programme devoted to science 372 00:25:47,979 --> 00:25:51,574 and the fantastic discoveries as we explore the universe Now, 373 00:25:51,683 --> 00:25:52,342 of course, 374 00:25:52,450 --> 00:25:53,712 superstring theory, 375 00:25:53,919 --> 00:25:57,912 the theory that will perhaps give us an explanation for the entire universe. 376 00:26:00,992 --> 00:26:03,153 Some people say the instant of the big bang, 377 00:26:03,261 --> 00:26:04,785 the universe was a dot. 378 00:26:11,603 --> 00:26:14,697 The new picture is that it's like a bowl of noodles, 379 00:26:14,973 --> 00:26:18,670 a bowl of noodles where we have thousands and millions of little strings, 380 00:26:18,777 --> 00:26:20,335 vibrating at the instant of time, 381 00:26:20,445 --> 00:26:21,969 that exploded, 382 00:26:22,914 --> 00:26:27,715 creating the enormous diversity of matter and energy that we see around us. 383 00:26:29,020 --> 00:26:31,818 Superstring theory is so bizarre, 384 00:26:31,923 --> 00:26:32,947 so strange, 385 00:26:33,058 --> 00:26:37,392 that we were not destined to see this theory in the twentieth century. 386 00:26:39,731 --> 00:26:43,098 Many of us believe that it's really twenty-first-century physics 387 00:26:43,201 --> 00:26:47,331 that fell accidentally into the twentieth century. 388 00:26:47,439 --> 00:26:48,997 It was discovered by accident, 389 00:26:49,107 --> 00:26:50,301 a fluke. 390 00:26:51,476 --> 00:26:54,070 A mathematician was reading up on topology when, 391 00:26:54,179 --> 00:26:55,271 guite by chance, 392 00:26:55,380 --> 00:26:59,111 he noticed an eguation which described the behaviour of a particle. 393 00:26:59,551 --> 00:27:01,985 Then he found another, describing gravity. 394 00:27:02,687 --> 00:27:07,715 Could this branch of maths contain within it the theory of everything? 395 00:27:09,260 --> 00:27:11,751 So we have two great theories of physics, 396 00:27:11,863 --> 00:27:13,296 the theory of the very big, 397 00:27:13,431 --> 00:27:15,194 Einstein's theory of relativity, 398 00:27:15,367 --> 00:27:17,733 and the theory of the very small, the guantum theory. 399 00:27:18,637 --> 00:27:20,400 And these two theories don't like each other, 400 00:27:20,505 --> 00:27:24,271 they are incompatible, one is smooth, beautiful, like marble, 401 00:27:24,442 --> 00:27:27,138 and the other one is coarse and grainy, like wood. 402 00:27:27,345 --> 00:27:28,744 And to get them to, 403 00:27:28,847 --> 00:27:33,045 to meet together has been the object of the last fifty years 404 00:27:33,151 --> 00:27:35,119 of intense investigation. 405 00:27:35,487 --> 00:27:37,045 Today, we think we have it. 406 00:27:37,222 --> 00:27:39,782 We think we have the superstring theory, 407 00:27:39,991 --> 00:27:42,459 which is perhaps the most fantastic, 408 00:27:42,727 --> 00:27:46,857 the most marvellous theory ever proposed in the history of science. 409 00:27:50,135 --> 00:27:53,866 After years trying to connect two incompatible theories, 410 00:27:54,072 --> 00:27:56,597 now there was a radical new candidate, 411 00:27:56,775 --> 00:27:59,676 based on tiny magical strings. 412 00:28:03,848 --> 00:28:05,645 Strings are extremely tiny, 413 00:28:05,817 --> 00:28:08,945 like a hundred billion billion times smaller than a proton, 414 00:28:09,087 --> 00:28:09,951 so let me explain. 415 00:28:10,355 --> 00:28:13,847 Take a atom, and expand it to the size of the solar system. 416 00:28:14,159 --> 00:28:16,525 If the atom were the size of. Our solar system, 417 00:28:16,695 --> 00:28:22,395 then a string is much smaller than that, a string is the size of an atom. 418 00:28:22,901 --> 00:28:25,802 That is how incredibly tiny this all is. 419 00:28:26,204 --> 00:28:31,574 We also think that once upon a time the universe was the size of a string 420 00:28:37,949 --> 00:28:40,543 When stings move, they vibrate. 421 00:28:40,719 --> 00:28:44,849 They force the space around it to curl up, to bend, 422 00:28:44,956 --> 00:28:47,720 exactly as Einstein had predicted. 423 00:28:58,269 --> 00:29:00,897 Now the guestion that scientists had grappled with 424 00:29:01,005 --> 00:29:04,805 since Einstein seemed as if it was about to be answered. 425 00:29:05,577 --> 00:29:06,703 With string theory, 426 00:29:06,845 --> 00:29:09,245 it looked like there was no difference between the worlds 427 00:29:09,347 --> 00:29:11,508 of the big and the small. 428 00:29:12,217 --> 00:29:15,311 We physicists have been puzzled by the fact that we have matter, 429 00:29:15,453 --> 00:29:17,614 like atoms, and we have forces, 430 00:29:17,722 --> 00:29:19,280 like, er, like gravity, 431 00:29:19,424 --> 00:29:20,789 that, that attract atoms. 432 00:29:20,992 --> 00:29:24,155 Now we realise that this dichotomy between force 433 00:29:24,262 --> 00:29:27,254 and matter is really not a dichotomy at all. 434 00:29:27,365 --> 00:29:30,266 These are nothing but vibrations of the same string. 435 00:29:30,435 --> 00:29:33,233 One string that vibrates could be a guark, 436 00:29:33,438 --> 00:29:35,565 another string that vibrates could be an electron. 437 00:29:35,774 --> 00:29:39,904 But yet another string that vibrates that vibrates could be light, a photon, 438 00:29:40,011 --> 00:29:42,343 or Einstein's theory of gravity. 439 00:29:44,916 --> 00:29:48,044 But the full potential of string theory is still unknown. 440 00:29:48,419 --> 00:29:50,319 It seems to offer answers, 441 00:29:50,855 --> 00:29:54,484 but the eguations also create a new set of guestions 442 00:29:54,959 --> 00:29:58,122 guestions that at the moment we can't answer. 443 00:30:00,665 --> 00:30:02,155 These eguations are well defined, 444 00:30:02,267 --> 00:30:03,199 they're well known, 445 00:30:03,301 --> 00:30:04,563 but some people think that perhaps 446 00:30:04,669 --> 00:30:07,263 we humans are not smart enough to solve them. 447 00:30:07,438 --> 00:30:09,872 Think of a duck, or, or, 448 00:30:10,041 --> 00:30:13,135 er, a monkey, why should a duck or a monkey understand 449 00:30:13,344 --> 00:30:17,075 calculus, or electric fields, or black holes? 450 00:30:17,248 --> 00:30:21,514 And why is it that we have the power to understand the big bang 451 00:30:21,619 --> 00:30:22,881 and the black holes? 452 00:30:23,054 --> 00:30:23,952 And then the guestion is, 453 00:30:24,055 --> 00:30:27,252 are we smart enough to understand the theory of everything? 454 00:30:27,659 --> 00:30:29,388 At the present time - no. 455 00:30:30,762 --> 00:30:32,559 By the end of the eighties, 456 00:30:32,697 --> 00:30:36,633 I and a number of other physicists were beginning to wonder 457 00:30:36,768 --> 00:30:41,535 if string theory really was the ultimate theory of the universe 458 00:30:42,173 --> 00:30:47,440 One problem was that there were five different string theories. 459 00:30:48,980 --> 00:30:51,881 So much for a single theory of everything. 460 00:30:58,156 --> 00:31:03,389 The American cosmologist Lee Smolin took a lonely step back from physics. 461 00:31:05,263 --> 00:31:08,289 He wondered if we were looking for the wrong thing. 462 00:31:08,766 --> 00:31:13,669 Why should the answer to the universe be contained in a mathematical eguation? 463 00:31:16,274 --> 00:31:21,234 The hope behind string theory originally was that there would be one simple law 464 00:31:21,412 --> 00:31:25,007 which would have a unigue solution, 465 00:31:25,116 --> 00:31:28,176 which would explain how the, universe is, 466 00:31:28,386 --> 00:31:30,445 the history of the universe, and so forth, 467 00:31:30,788 --> 00:31:35,521 and that hope that all the guestions would be answered 468 00:31:35,693 --> 00:31:40,096 in a single law is what has not happened in string theory. 469 00:31:44,202 --> 00:31:45,863 It was thinking about this, 470 00:31:46,137 --> 00:31:48,970 at the same time I was reading about biology, 471 00:31:49,340 --> 00:31:52,571 er, that led me to begin to wonder 472 00:31:52,744 --> 00:31:55,542 whether the answers to some of the guestions 473 00:31:56,114 --> 00:32:00,676 in elementary particle physics did not rest in a single unigue theory, 474 00:32:00,785 --> 00:32:04,687 but maybe would be a result of historical accident, 475 00:32:04,789 --> 00:32:08,953 and maybe there could be a process by which, 476 00:32:09,093 --> 00:32:12,256 through a series of developments in the early history of the universe, 477 00:32:12,797 --> 00:32:16,164 somehow the universe chose what its parameters were. 478 00:32:17,936 --> 00:32:20,837 The wonderful thing about the biological world is 479 00:32:20,939 --> 00:32:22,372 that it's so complicated. 480 00:32:23,041 --> 00:32:24,906 There are so many different species, 481 00:32:25,276 --> 00:32:28,404 they're so beautiful in so many different ways, 482 00:32:29,314 --> 00:32:32,681 and one would think that one could not possibly explain this, 483 00:32:32,784 --> 00:32:35,344 which is of course what people thought before Darwin. 484 00:32:37,488 --> 00:32:42,425 What Darwin discovered is that there is a rational way to understand 485 00:32:42,593 --> 00:32:46,859 how such enormous variety and complexity can come to be in the natural world, 486 00:32:47,031 --> 00:32:48,760 without being put there in the first place, 487 00:32:48,866 --> 00:32:54,463 and the basic idea is that you have some population, 488 00:32:54,639 --> 00:32:56,163 which can reproduce itself, 489 00:32:56,541 --> 00:32:58,406 that when it does so, 490 00:32:58,609 --> 00:33:03,103 there are small random changes in the characteristics, 491 00:33:03,348 --> 00:33:07,910 and that these characteristics lead to differences 492 00:33:08,052 --> 00:33:10,179 in how well the creatures survive. 493 00:33:12,924 --> 00:33:18,419 Could Darwin's idea of natural selection somehow be applied to our universe? 494 00:33:25,636 --> 00:33:28,002 If one studies astronomy on scales much, 495 00:33:28,106 --> 00:33:29,937 much larger than the earth, 496 00:33:30,041 --> 00:33:32,339 for example, the disk of a spiral galaxy, 497 00:33:32,543 --> 00:33:36,035 one discovers it's a complex self-organised system, 498 00:33:36,681 --> 00:33:39,946 somewhat akin to biology on a much simpler level. 499 00:33:45,123 --> 00:33:47,387 It turns out that The new possibility 500 00:33:47,492 --> 00:33:51,326 which Darwin gave us is that a system can have all the beauty 501 00:33:51,429 --> 00:33:53,420 and variety and complexity of our world. 502 00:33:53,564 --> 00:33:55,896 And be assembled from itself, 503 00:33:56,000 --> 00:33:58,400 that it can organise itself over time. 504 00:34:02,006 --> 00:34:07,103 What twentieth-century science is leading to is, 505 00:34:07,345 --> 00:34:09,813 in my view, I mean, of course could be wrong, 506 00:34:10,048 --> 00:34:13,108 the culmination of this view of the universe 507 00:34:13,217 --> 00:34:17,347 as something which does create itself and assemble itself. 508 00:34:21,292 --> 00:34:23,522 In Russia, Andrei Linde was also. 509 00:34:23,628 --> 00:34:25,562 Thinking about evolution. 510 00:34:26,297 --> 00:34:28,595 But his thinking stayed rooted in physics, 511 00:34:28,800 --> 00:34:34,136 as he tried to perfect the inflation theory It wasn't proving easy. 512 00:34:34,305 --> 00:34:37,763 Russian politics were affecting his health and his work. 513 00:34:38,242 --> 00:34:40,938 85 was the first year of perestroika, 514 00:34:41,479 --> 00:34:43,276 so the first year of perestroika Gorbachev 515 00:34:43,381 --> 00:34:48,910 just came to power and they started reconstructing everything, 516 00:34:49,053 --> 00:34:51,248 which is a translation of the Russian perestroika, 517 00:34:51,456 --> 00:34:55,017 the reconstruction, and as a first step, 518 00:34:55,359 --> 00:34:59,090 they completely forbidden us to send our papers abroad, 519 00:34:59,964 --> 00:35:03,661 so I have a feeling that I am living with my mouth shut, 520 00:35:03,835 --> 00:35:09,000 I cannot tell others what I am doing, and this was pretty depressing. 521 00:35:11,375 --> 00:35:15,812 So it became so much depressing the actually I became simply ill, 522 00:35:16,147 --> 00:35:19,310 and now I was lying in the bed for about a month and a half, 523 00:35:19,484 --> 00:35:20,576 and then, all of a sudden, 524 00:35:20,685 --> 00:35:22,414 there was a call from Academy of Sciences, 525 00:35:22,620 --> 00:35:25,316 and they told me that I must go to Italy 526 00:35:25,456 --> 00:35:27,890 to give some popular lectures on astronomy, 527 00:35:27,992 --> 00:35:30,893 and I told them, I am ill, I cannot go. 528 00:35:33,998 --> 00:35:35,522 After years of repression, 529 00:35:35,666 --> 00:35:38,464 suddenly Linde was free to say what he liked. 530 00:35:38,870 --> 00:35:41,998 But he only had twenty-four hours to think of a new idea. 531 00:35:45,576 --> 00:35:48,977 After this year with the mouth shut, 532 00:35:49,380 --> 00:35:52,747 they are suggesting me that if I do something, 533 00:35:53,050 --> 00:35:55,314 then tomorrow it will be sent there 534 00:35:55,419 --> 00:35:58,286 by diplomatic mail without any approvement, 535 00:35:58,422 --> 00:36:02,017 without any signatures, without any of these bureaucratic work, 536 00:36:02,126 --> 00:36:03,889 tomorrow it will be in Italy. 537 00:36:04,328 --> 00:36:06,091 On the other hand, it can, 538 00:36:06,264 --> 00:36:10,724 it must be done just immediately, and, and I am really sick, 539 00:36:10,868 --> 00:36:15,498 I just cannot think, I, I took my head like that and I started, 540 00:36:15,606 --> 00:36:18,234 what can I invent within half an hour 541 00:36:18,442 --> 00:36:20,239 or so I will write it today in the evening 542 00:36:20,344 --> 00:36:22,005 and tomorrow I'll sent it to Italy, 543 00:36:22,213 --> 00:36:24,147 what can I do within half an hour? 544 00:36:25,316 --> 00:36:27,113 And within half an hour, 545 00:36:27,251 --> 00:36:30,015 I have got a theory of self-reproducing universe. 546 00:36:33,124 --> 00:36:34,716 In Linde's new theory, 547 00:36:34,892 --> 00:36:37,793 inflation does not take place in a bubble at all. 548 00:36:38,629 --> 00:36:40,221 Instead of one universe growing, 549 00:36:40,331 --> 00:36:43,198 his eguations predict that there have to be many. 550 00:36:44,001 --> 00:36:48,233 All will be different, and all will have their own big bang. 551 00:36:49,273 --> 00:36:51,639 In time, they will seed other universes, 552 00:36:51,776 --> 00:36:53,937 so the process goes on for ever. 553 00:36:55,279 --> 00:36:57,144 It's a purely theoretical proposal, 554 00:36:57,315 --> 00:37:00,910 build from Linde's earlier imperfect ideas of inflation 555 00:37:01,452 --> 00:37:04,580 Out of depression had come inspiration. 556 00:37:07,091 --> 00:37:11,551 And since that time I did not have such a depression, 557 00:37:12,063 --> 00:37:15,226 which in a certain sense may be unfortunate. 558 00:37:20,171 --> 00:37:25,541 Smolin and Linde's evolutionary theories have failed to catch on. 559 00:37:26,244 --> 00:37:28,974 Most cosmologists, like me, 560 00:37:29,146 --> 00:37:33,549 still want to find a single explanation of a single universe 561 00:37:36,454 --> 00:37:39,719 It was this ambition to explain a single universe 562 00:37:39,857 --> 00:37:42,052 which kept hopes for string theory alive, 563 00:37:42,426 --> 00:37:44,951 even when it seemed to be going nowhere. 564 00:37:49,267 --> 00:37:50,234 In the last several years, 565 00:37:50,334 --> 00:37:51,562 we've been in the wilderness, 566 00:37:51,669 --> 00:37:55,230 the mathematics has proven too difficult to solve superstring theory, 567 00:37:55,339 --> 00:37:57,398 the theory is smarter than we are. 568 00:37:58,109 --> 00:38:03,012 The creative engine behind superstring theory is Ed Witten, at Princeton. 569 00:38:03,180 --> 00:38:03,646 In fact, 570 00:38:03,748 --> 00:38:05,841 Scientific American once said that Ed Witten is, 571 00:38:05,950 --> 00:38:08,475 guote, the smartest man on earth, 572 00:38:08,586 --> 00:38:13,546 unguote, and if anyone is smart enough to solve superstring theory, 573 00:38:13,658 --> 00:38:15,922 it's probably going to be Ed Witten. 574 00:38:21,799 --> 00:38:25,792 It seemed pretty clear that if there was a chance to go way 575 00:38:25,903 --> 00:38:28,531 beyond familiar understanding of physics, 576 00:38:29,040 --> 00:38:32,100 string theory was the most ambitious prospect. 577 00:38:32,310 --> 00:38:34,471 It also was clear then, as it is now, 578 00:38:34,779 --> 00:38:36,940 that it was a very long-term proposition. 579 00:38:38,449 --> 00:38:41,509 Witten turned away from more concrete aspects of physics, 580 00:38:41,652 --> 00:38:45,645 to tackle the highly theoretical mathematics of string theory. 581 00:38:46,624 --> 00:38:49,684 I wasn't originally interested in maths, 582 00:38:49,860 --> 00:38:51,794 I was interested in doing physics, 583 00:38:52,730 --> 00:38:56,723 and I remember very well having some reticence for guite some time 584 00:38:57,001 --> 00:39:00,835 about making the one hundred per cent commitment, 585 00:39:00,938 --> 00:39:04,135 of really deciding that was going to be my life. 586 00:39:09,847 --> 00:39:12,645 However bizarre its claims, string theory, 587 00:39:12,817 --> 00:39:14,808 like all scientific ideas, 588 00:39:14,985 --> 00:39:20,855 has to survive a basic test: Can it describe the world we know? 589 00:39:30,901 --> 00:39:33,563 String theory, as it had developed by the mid-eighties, 590 00:39:33,738 --> 00:39:37,401 was characterised by the fact that there were five theories we knew about, 591 00:39:39,310 --> 00:39:41,107 and that raised the rather curious guestion 592 00:39:41,212 --> 00:39:42,907 that was always a little bit embarrassing. 593 00:39:44,115 --> 00:39:46,106 If one of those theories describes our universe, 594 00:39:46,450 --> 00:39:48,645 then who lives in other four universes? 595 00:39:52,056 --> 00:39:54,286 We've come to understand that those five theories 596 00:39:54,392 --> 00:39:57,884 we've been studying are all limiting cases of one big picture. 597 00:39:59,697 --> 00:40:02,632 To make an analogy with the blind man and the elephants, 598 00:40:02,733 --> 00:40:04,530 there is the guy who discovered the trunk 599 00:40:04,635 --> 00:40:06,330 and there's the guy who discovered the tail, 600 00:40:06,570 --> 00:40:08,231 and there's the guy who discovered the ear, 601 00:40:08,406 --> 00:40:09,703 and in the past we thought there 602 00:40:09,807 --> 00:40:10,831 were five different things, 603 00:40:10,941 --> 00:40:12,101 now we know there is one elephant, 604 00:40:12,276 --> 00:40:14,301 we still don't understand that elephant too well. 605 00:40:17,481 --> 00:40:21,713 Witten remains convinced that string theory can make sense. 606 00:40:22,186 --> 00:40:23,710 But it's lonely work. 607 00:40:24,255 --> 00:40:26,985 He lives in a strange, abstract world, 608 00:40:27,324 --> 00:40:31,818 where many dimensions exist rather than the four we experience on earth. 609 00:40:32,430 --> 00:40:36,025 Even other physicists, used to working in abstract spaces, 610 00:40:36,233 --> 00:40:39,134 find it difficult to share his convictions. 611 00:40:41,605 --> 00:40:43,573 A lot of people, even professional physicists, 612 00:40:43,674 --> 00:40:44,868 in my opinion, 613 00:40:45,009 --> 00:40:49,139 don't fully grasp the scope and richness of the structure involved. 614 00:40:49,380 --> 00:40:53,817 People may tend to be too impatient for guick results in. Some cases. 615 00:40:55,286 --> 00:40:57,754 I think that there are a lot of reasons to think 616 00:40:57,855 --> 00:41:00,153 that a structure which is so rich 617 00:41:00,291 --> 00:41:03,556 and so physical and which has been the source, 618 00:41:03,694 --> 00:41:05,787 the continued source of so many beautiful discoveries 619 00:41:05,963 --> 00:41:07,328 must be on the right track 620 00:41:10,901 --> 00:41:12,562 Like Einstein before him, 621 00:41:12,837 --> 00:41:15,203 Witten's instincts drive him on. 622 00:41:15,973 --> 00:41:19,136 But a solution is painfully elusive. 623 00:41:21,345 --> 00:41:22,835 When you are doing a calculation, 624 00:41:23,047 --> 00:41:25,481 it's usually on some very specific detail, 625 00:41:25,616 --> 00:41:27,811 it's a tiny, tiny part of the big picture, 626 00:41:27,985 --> 00:41:31,250 and you're hoping that that piece with shed light on the big picture, 627 00:41:31,422 --> 00:41:33,686 sometimes it does but usually it doesn't. 628 00:41:37,228 --> 00:41:39,059 Oftentimes you come home at the end of the day 629 00:41:39,230 --> 00:41:41,698 and you know exactly the amount you knew at the beginning of the day. 630 00:41:42,800 --> 00:41:44,597 But sometimes, you know a little bit more. 631 00:41:47,371 --> 00:41:50,738 I think that this investigation is the richest thing 632 00:41:50,841 --> 00:41:54,834 that physicists can tackle, and how far we'll get in our lifetimes, 633 00:41:54,945 --> 00:41:56,071 there's no way to know, 634 00:41:56,180 --> 00:41:58,205 and we might get the answers we dream of getting, 635 00:41:58,682 --> 00:42:00,047 we might fall a little short, 636 00:42:00,518 --> 00:42:02,679 But I think we can accomplish more in the future, 637 00:42:02,887 --> 00:42:07,153 and getting as far as we can is the best we can do. 638 00:42:16,567 --> 00:42:21,197 Twenty years ago, I said there was a fifty-fifty chance 639 00:42:21,305 --> 00:42:26,675 we would have a complete picture of the universe in the next twenty years. 640 00:42:27,244 --> 00:42:29,303 That is still my estimate today, 641 00:42:29,446 --> 00:42:31,937 but the twenty years starts now. 642 00:42:32,850 --> 00:42:34,909 It's very hard to build a cons-, 643 00:42:35,019 --> 00:42:37,852 a fully consistent guantum theory of gravity. 644 00:42:38,522 --> 00:42:41,355 The string. Theorists think they have one, 645 00:42:41,825 --> 00:42:43,349 they may well not be right, 646 00:42:43,460 --> 00:42:45,985 they haven't yet pushed their theory far enough 647 00:42:46,096 --> 00:42:50,032 so you can compare the conseguences of string theory to experiment, 648 00:42:50,301 --> 00:42:52,064 and that's what you ultimately need 649 00:42:55,406 --> 00:42:57,772 But perhaps, for the first time, 650 00:42:57,975 --> 00:43:00,876 an experimental group could be closer to hand. 651 00:43:02,513 --> 00:43:05,812 Neil Turok is getting ready to journey into the unknown. 652 00:43:07,718 --> 00:43:11,176 Like any explorer, he needs to know where he's going. 653 00:43:11,622 --> 00:43:15,080 But our current map of the early universe isn't good enough. 654 00:43:16,927 --> 00:43:20,658 Imagine you were trying to navigate across a continent, 655 00:43:20,831 --> 00:43:24,790 and you had a map which only showed features 656 00:43:24,935 --> 00:43:27,165 greater than a hundred miles across, 657 00:43:27,404 --> 00:43:30,430 er, it wouldn't be much use in finding your way, 658 00:43:30,641 --> 00:43:33,371 er, along a particular route, 659 00:43:33,944 --> 00:43:37,402 but if you had a map that has a resolution of a mile, 660 00:43:37,548 --> 00:43:39,675 then that becomes much more useful. 661 00:43:40,851 --> 00:43:44,343 In the vast clean rooms of the European Space Agency, 662 00:43:44,455 --> 00:43:48,721 Turok is involved with a project to make the map of all maps, 663 00:43:48,892 --> 00:43:51,918 with a satellite called the Planck Explorer. 664 00:43:54,498 --> 00:43:57,023 What we'll do is look out, 665 00:43:57,167 --> 00:44:00,830 map the whole sky at a very high resolution. 666 00:44:14,385 --> 00:44:18,116 Basically, this is eguivalent to making a map of the earth 667 00:44:18,222 --> 00:44:21,089 where you show all the rivers and the mountains 668 00:44:21,191 --> 00:44:23,659 and the valleys in exguisite detail, 669 00:44:24,094 --> 00:44:28,155 and this map will contain a vast amount of information, 670 00:44:29,333 --> 00:44:32,063 it will give us the best picture we have of the universe 671 00:44:33,404 --> 00:44:37,636 The Planck Explorer will look billions of years back in time, 672 00:44:38,208 --> 00:44:40,335 to when the very first signs of the structure 673 00:44:40,444 --> 00:44:42,309 of the universe are visible. 674 00:44:43,213 --> 00:44:48,617 Turok's map is not the universe as it is, but as it was. 675 00:44:48,819 --> 00:44:51,652 It is a map of the universe of very early times, 676 00:44:52,256 --> 00:44:53,985 we're not sure guite when, 677 00:44:54,224 --> 00:44:59,127 er, the radiation from the big bang was emitted from the, 678 00:44:59,229 --> 00:45:01,857 er, plasma in the early universe, 679 00:45:02,099 --> 00:45:04,897 but, er, when we look out and we see the sky, 680 00:45:05,502 --> 00:45:09,598 we're looking directly at different patches of hot plasma 681 00:45:09,773 --> 00:45:12,071 and there are going to be of slightly different temperature, 682 00:45:12,276 --> 00:45:16,508 and so this will be a map of the temperature variations on the sky. 683 00:45:36,533 --> 00:45:39,661 The hope is that soon we may be able to see the heat 684 00:45:39,770 --> 00:45:43,797 of the early universe in enough detail to answer our guestions 685 00:45:43,907 --> 00:45:45,772 about how it was formed. 686 00:45:47,778 --> 00:45:49,871 If the data is detailed enough, 687 00:45:50,047 --> 00:45:55,849 it could offer observational evidence which may clarify how everything began. 688 00:45:58,355 --> 00:45:59,151 I think, er, 689 00:45:59,256 --> 00:46:02,419 people are usually excessively confident about the theories, 690 00:46:02,626 --> 00:46:06,926 because there has been an absence of data, 691 00:46:07,030 --> 00:46:09,863 and that's allowed people to be confident about the theories, 692 00:46:10,000 --> 00:46:14,562 er, the current theories there are all based on very clever ideas, 693 00:46:14,738 --> 00:46:17,104 er, and very imaginative ideas, 694 00:46:18,876 --> 00:46:20,673 but what's really good about them is 695 00:46:20,778 --> 00:46:23,975 they do give you a well-defined framework within 696 00:46:24,081 --> 00:46:26,049 which you can make predictions. 697 00:46:27,384 --> 00:46:30,217 Turok has turned the maths of theories like superstrings 698 00:46:30,320 --> 00:46:32,550 and inflation into pictures, 699 00:46:32,990 --> 00:46:35,356 which illustrate the subtle temperature variations 700 00:46:35,459 --> 00:46:37,950 that must exist in the early universe 701 00:46:38,962 --> 00:46:41,157 Each theory predicts a different picture. 702 00:46:41,265 --> 00:46:45,702 The Planck Explorer will see if any of them could be right. 703 00:46:48,071 --> 00:46:50,096 We're in the wonderful situation now where, 704 00:46:50,207 --> 00:46:51,970 over the next five or ten years, 705 00:46:52,176 --> 00:46:54,667 the theory is going to be beaten to death, 706 00:46:54,845 --> 00:46:58,542 or theories that we have will be beaten to death in terms of making predictions, 707 00:46:58,749 --> 00:47:01,843 that will all be settled and we'll, 708 00:47:01,952 --> 00:47:03,010 they'll all, 709 00:47:03,120 --> 00:47:06,954 er, say exactly what they expect to find in the sky, 710 00:47:07,191 --> 00:47:12,356 and then this satellite will fly and will map the sky to a very high precision, 711 00:47:12,529 --> 00:47:14,963 and, er, we'll see what happens. 712 00:47:18,302 --> 00:47:20,270 It's a very exciting time to be involved, 713 00:47:20,437 --> 00:47:23,270 it's a unigue opportunity in science where you, 714 00:47:23,373 --> 00:47:24,067 you're told, 715 00:47:24,174 --> 00:47:26,699 within ten years we're going to have the data 716 00:47:27,010 --> 00:47:31,470 that will prove or disprove any theory of how structure formed in the universe, 717 00:47:33,817 --> 00:47:35,148 and you've got ten years, 718 00:47:36,253 --> 00:47:38,483 so we'll see if anyone gets it right. 719 00:47:42,159 --> 00:47:46,528 It could be that in a few years we will have a complete theory 720 00:47:46,630 --> 00:47:49,224 that is confirmed by experiment. 721 00:47:50,234 --> 00:47:52,464 It would be a remarkable achievement, 722 00:47:52,603 --> 00:47:55,663 perhaps the ultimate triumph of science. 723 00:47:57,674 --> 00:48:03,010 But knowing how the universe works is not enough to tell us why it exists. 724 00:48:05,315 --> 00:48:10,116 To find the answer to that guestion would be to know the mind of God.