English subtitles for clip: File:Stephen Hawking discusses the origin of the universe, UC Berkeley, 2007.webm
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1 00:00:10,214 --> 00:00:12,794 (audience chatters) 2 00:00:12,790 --> 00:00:15,220 - [Presenter] Good evening, ladies and gentlemen. 3 00:00:15,220 --> 00:00:17,860 Welcome to Cal Performances. 4 00:00:17,860 --> 00:00:20,300 Tonight's performance is brought to you in part 5 00:00:20,300 --> 00:00:23,840 by our season sponsor, Wells Fargo Bank. 6 00:00:23,840 --> 00:00:26,530 Please take a moment to turn off your cell phones, 7 00:00:26,530 --> 00:00:29,870 and as a reminder, the use of recording devices and cameras 8 00:00:29,870 --> 00:00:32,770 of any kind is not permitted in the theater. 9 00:00:32,770 --> 00:00:34,650 Thank you and enjoy the performance. 10 00:00:43,940 --> 00:00:44,890 - Good evening. 11 00:00:46,727 --> 00:00:49,727 (audience applauds) 12 00:00:55,200 --> 00:00:56,390 For those of you who don't know me, 13 00:00:56,390 --> 00:00:59,890 I'm Robert Birgeneau, Chancellor of UC Berkeley, 14 00:00:59,890 --> 00:01:02,940 but for tonight's event, more importantly, 15 00:01:02,940 --> 00:01:04,230 professor of physics. 16 00:01:05,430 --> 00:01:08,610 It's my great pleasure to welcome you 17 00:01:08,610 --> 00:01:12,910 to the J. Robert Oppenheimer Lecture in Physics. 18 00:01:14,530 --> 00:01:16,850 Berkeley has a long tradition 19 00:01:16,850 --> 00:01:20,330 of being a world-leading center of scholarly activity 20 00:01:20,330 --> 00:01:23,680 and of bringing to campus the very finest minds 21 00:01:23,680 --> 00:01:26,740 to address us in a public forum 22 00:01:26,740 --> 00:01:29,040 on great intellectual challenges. 23 00:01:30,890 --> 00:01:32,940 It is this Berkeley tradition 24 00:01:32,940 --> 00:01:35,370 of great learning and public service 25 00:01:35,370 --> 00:01:37,490 that the Department of Physics 26 00:01:37,490 --> 00:01:39,330 has arranged for tonight's lecture 27 00:01:39,330 --> 00:01:43,770 to be given by world-renowned scholar Stephen Hawking. 28 00:01:45,760 --> 00:01:47,540 Professor Hawking has extracted, 29 00:01:47,540 --> 00:01:50,250 has, pardon me, attracted, not, 30 00:01:50,250 --> 00:01:52,760 he's also extracted great physics, but he's, 31 00:01:52,762 --> 00:01:53,592 (audience laughs) 32 00:01:53,595 --> 00:01:57,275 attracted extraordinary interest from around the world 33 00:01:57,270 --> 00:02:00,560 for his work on quantum theories of the cosmos. 34 00:02:02,720 --> 00:02:05,200 We here at Berkeley are no exception 35 00:02:05,200 --> 00:02:08,690 to the world's fascination with this extraordinary scholar 36 00:02:09,530 --> 00:02:13,930 as witnessed not only by the complete sellout 37 00:02:13,930 --> 00:02:15,780 of Zellerbach Hall, 38 00:02:15,780 --> 00:02:18,540 but also by the fact that Wheeler Hall, 39 00:02:18,540 --> 00:02:20,470 where this event is simulcast, 40 00:02:20,470 --> 00:02:24,090 is also completely sold out, just extraordinary. 41 00:02:24,091 --> 00:02:27,091 (audience applauds) 42 00:02:31,610 --> 00:02:33,680 It is with deepest pleasure that I, 43 00:02:33,680 --> 00:02:38,680 on behalf of the entire campus and surrounding community, 44 00:02:38,890 --> 00:02:42,220 welcome Professor Stephen Hawking to Berkeley. 45 00:02:42,216 --> 00:02:45,216 (audience applauds) 46 00:02:52,843 --> 00:02:54,623 As many of you will know, 47 00:02:54,620 --> 00:02:57,640 this year, the College of Letters & Science 48 00:02:57,640 --> 00:03:00,330 introduced On the Same Page, 49 00:03:01,260 --> 00:03:05,290 a program asking all of our freshmen to read a common book. 50 00:03:06,590 --> 00:03:10,530 That book was Stephen Hawking's and Leonard Mlodinow's 51 00:03:10,530 --> 00:03:12,700 A Briefer History of Time. 52 00:03:14,650 --> 00:03:18,450 Faculty and students from many different disciplines 53 00:03:18,450 --> 00:03:21,430 took part in discussing this book. 54 00:03:22,840 --> 00:03:27,160 In fact, even the chancellor, namely myself, 55 00:03:27,160 --> 00:03:29,260 was invited to participate, 56 00:03:29,260 --> 00:03:33,750 and last Thursday, I held a small discussion group 57 00:03:33,750 --> 00:03:36,060 with a number of our freshmen, 58 00:03:36,060 --> 00:03:39,430 embarrassingly one of whom at the age of 18 59 00:03:39,430 --> 00:03:41,740 turned out to understand quantum gravity 60 00:03:41,740 --> 00:03:43,250 much better than I did. 61 00:03:43,249 --> 00:03:45,469 (audience laughs) 62 00:03:45,470 --> 00:03:48,660 I'd now like to invite professor Mark Richards, 63 00:03:48,660 --> 00:03:51,910 the executive dean of the College of Letters & Sciences 64 00:03:51,910 --> 00:03:55,160 and dean of physical sciences to come forward 65 00:03:55,160 --> 00:03:58,100 and tell you more about this wonderful project 66 00:03:58,100 --> 00:04:01,880 and how Berkeley is a leader in educating students 67 00:04:01,880 --> 00:04:03,640 through unique opportunities 68 00:04:03,640 --> 00:04:07,000 such as the Oppenheimer Lecture, Mark. 69 00:04:07,004 --> 00:04:10,004 (audience applauds) 70 00:04:15,926 --> 00:04:17,396 - Thank you very much, Chancellor Birgeneau. 71 00:04:17,400 --> 00:04:19,760 I can assure you that Chancellor Birgeneau is here tonight 72 00:04:19,760 --> 00:04:21,270 mainly for the physics. 73 00:04:23,040 --> 00:04:25,070 I'm here as representative 74 00:04:25,070 --> 00:04:27,450 of the College of Letters & Science, 75 00:04:27,450 --> 00:04:30,240 and this is a very special occasion 76 00:04:30,240 --> 00:04:32,560 on which we're inaugurating a new program, 77 00:04:32,560 --> 00:04:35,720 as the chancellor said, called On the Same Page. 78 00:04:35,720 --> 00:04:37,350 And I want to take just a few minutes 79 00:04:37,350 --> 00:04:39,970 to describe this program 80 00:04:39,970 --> 00:04:43,840 because it's very relevant to the events tonight. 81 00:04:43,840 --> 00:04:46,080 Now the College of Letters & Science 82 00:04:46,080 --> 00:04:49,250 is actually most of the University of California, Berkeley. 83 00:04:49,250 --> 00:04:51,860 That is, most of the faculty, most of the students, 84 00:04:51,860 --> 00:04:53,450 most of the departments you think of 85 00:04:53,450 --> 00:04:56,790 like physics and math and biology and economics, 86 00:04:56,790 --> 00:05:00,410 anthropology, history, music, literature. 87 00:05:00,410 --> 00:05:03,050 We teach 58 languages here 88 00:05:03,050 --> 00:05:05,260 and we have 38 departments in L&S. 89 00:05:06,610 --> 00:05:08,330 It's a very big place. 90 00:05:08,330 --> 00:05:11,310 As you might imagine, for an entering freshman, 91 00:05:11,310 --> 00:05:14,320 can be somewhat of an intimidating experience. 92 00:05:14,320 --> 00:05:16,560 And we've been working very hard 93 00:05:16,560 --> 00:05:18,480 in the College of Letters & Science 94 00:05:18,480 --> 00:05:22,170 to make it feel a bit smaller and a little bit more friendly 95 00:05:22,170 --> 00:05:23,730 for the entering freshmen. 96 00:05:24,630 --> 00:05:27,150 There are a number of programs that we're very proud of, 97 00:05:27,150 --> 00:05:29,680 for example, the Freshman Seminar series, 98 00:05:29,680 --> 00:05:32,940 where we strive to create a seat for every entering freshman 99 00:05:32,940 --> 00:05:36,690 to have a close experience with faculty 100 00:05:36,690 --> 00:05:39,920 in classes of size 15 to 20 101 00:05:39,920 --> 00:05:42,340 on whimsical subjects sometimes. 102 00:05:44,160 --> 00:05:45,980 Also the Discovery courses 103 00:05:45,980 --> 00:05:48,310 which are our flagship breadth courses 104 00:05:48,310 --> 00:05:52,730 taught by our very finest instructors for entering freshmen. 105 00:05:52,730 --> 00:05:55,460 And also undergraduate research programs 106 00:05:55,460 --> 00:05:59,200 to complement this more intimate experience 107 00:05:59,200 --> 00:06:01,940 with the faculty, the great faculty of UC Berkeley, 108 00:06:01,940 --> 00:06:04,260 and our goal is also for all undergraduates 109 00:06:04,260 --> 00:06:05,960 to have this research experience. 110 00:06:06,920 --> 00:06:09,520 On the Same Page is a new program in this direction. 111 00:06:09,520 --> 00:06:12,090 The idea has actually been around for some time, 112 00:06:12,090 --> 00:06:14,980 bouncing around among the L&S deans. 113 00:06:14,980 --> 00:06:19,260 But last May, when Professor Cohen was successful 114 00:06:19,260 --> 00:06:23,330 in inviting Stephen Hawking to be the Oppenheimer lecturer, 115 00:06:23,330 --> 00:06:26,550 it was just too good an opportunity to pass up. 116 00:06:26,550 --> 00:06:28,100 You're all probably familiar 117 00:06:28,100 --> 00:06:31,480 with Professor Hawking's famous popular book 118 00:06:31,480 --> 00:06:33,790 called A Brief History of Time. 119 00:06:33,790 --> 00:06:35,110 Very widely purchased, 120 00:06:35,110 --> 00:06:38,000 perhaps not as widely read or understood 121 00:06:38,000 --> 00:06:41,220 in its initial formulation. (audience laughs) 122 00:06:41,220 --> 00:06:43,410 There's a new version of this book, 123 00:06:43,410 --> 00:06:45,260 I happen to have a copy here, 124 00:06:45,260 --> 00:06:48,600 called A Briefer History of Time, 125 00:06:48,600 --> 00:06:51,300 in which Professor Hawking has teamed up 126 00:06:51,300 --> 00:06:54,810 with Leonard Mlodinow, who among other things 127 00:06:54,810 --> 00:06:57,910 is writer of the Star Trek, The Next Generation 128 00:06:57,910 --> 00:06:59,700 and Feynman's Rainbow 129 00:06:59,700 --> 00:07:02,390 and also happens to be a Berkeley PhD in physics 130 00:07:02,387 --> 00:07:04,827 and a resident science writer at Caltech. 131 00:07:06,840 --> 00:07:08,610 Also at this time, when we were thinking 132 00:07:08,610 --> 00:07:11,100 that this might be a good book and a good way 133 00:07:11,100 --> 00:07:13,480 to start the Freshman Seminar program, 134 00:07:13,480 --> 00:07:14,710 one of the closest friends 135 00:07:14,710 --> 00:07:17,920 of the College of Letters & Science stepped up to the plate 136 00:07:17,920 --> 00:07:21,240 as a donor and offered to buy a copy of this book 137 00:07:21,240 --> 00:07:24,050 for every freshman and entering transfer student 138 00:07:24,050 --> 00:07:25,710 at UC Berkeley this year, 139 00:07:25,710 --> 00:07:27,450 and they all received this, thank you. 140 00:07:27,452 --> 00:07:30,452 (audience applauds) 141 00:07:34,860 --> 00:07:36,620 So this November, all of our freshmen 142 00:07:36,620 --> 00:07:40,070 received a copy of this wonderful book in their mailboxes 143 00:07:40,070 --> 00:07:44,230 for light reading over their holidays. 144 00:07:45,550 --> 00:07:47,320 Now On the Same Page has meanings 145 00:07:47,320 --> 00:07:48,980 on at least three different levels, 146 00:07:48,980 --> 00:07:53,130 the obvious meanings being on the same page with the author, 147 00:07:53,130 --> 00:07:56,430 being on the same page with your fellow students 148 00:07:56,430 --> 00:07:58,400 and your faculty colleagues, 149 00:07:58,400 --> 00:08:01,710 but also on the same metaphorical page 150 00:08:01,710 --> 00:08:04,030 because in future years we might well have 151 00:08:04,030 --> 00:08:06,630 playwrights or composers or filmmakers 152 00:08:06,630 --> 00:08:09,000 instead of just plain old book authors 153 00:08:09,000 --> 00:08:11,190 to be the the feature of this program. 154 00:08:12,430 --> 00:08:14,170 Now I want you all to think about 155 00:08:14,170 --> 00:08:17,260 the last time you read a really great book 156 00:08:18,570 --> 00:08:20,880 and then imagine that all of your friends 157 00:08:20,880 --> 00:08:24,780 had just read the same book and then imagine 158 00:08:24,780 --> 00:08:27,460 that you could freely attend discussion sessions 159 00:08:27,460 --> 00:08:29,280 with world-renowned experts 160 00:08:29,280 --> 00:08:31,940 on every conceivable aspect of that book 161 00:08:32,800 --> 00:08:35,760 and then imagine that you also would have the opportunity 162 00:08:35,760 --> 00:08:38,720 to hear the author lecture and to meet the author. 163 00:08:39,880 --> 00:08:42,060 This is the experience that we hope to create 164 00:08:42,060 --> 00:08:45,510 for all the L&S students, beginning with their freshman year 165 00:08:45,510 --> 00:08:48,300 and continuing each year until their graduation. 166 00:08:49,510 --> 00:08:51,630 And the message is very clear. 167 00:08:51,630 --> 00:08:55,410 Welcome to Berkeley, a place of challenging ideas, 168 00:08:55,410 --> 00:08:59,160 a forum for diverse ways of interpreting 169 00:08:59,160 --> 00:09:01,510 and experiencing the world around us, 170 00:09:01,510 --> 00:09:04,520 and also an arena in which great universal themes 171 00:09:04,520 --> 00:09:06,560 are explored and questioned. 172 00:09:07,640 --> 00:09:11,060 Certainly this year's author and subject 173 00:09:11,060 --> 00:09:14,280 make for a fitting beginning for On the Same Page. 174 00:09:14,280 --> 00:09:16,240 It's not too hard to be interested 175 00:09:16,240 --> 00:09:18,460 in things like the origin of the universe 176 00:09:18,460 --> 00:09:21,090 and the fundamental nature of time. 177 00:09:21,090 --> 00:09:23,350 So I want to thank Professor Hawking 178 00:09:23,350 --> 00:09:25,970 for helping us make this a very special year 179 00:09:25,970 --> 00:09:28,330 in the College of Letters & Science at Cal. 180 00:09:29,470 --> 00:09:31,600 I'm also very happy to announce 181 00:09:31,600 --> 00:09:35,160 that the L&S deans have already selected next year's book. 182 00:09:37,090 --> 00:09:38,160 Are you waiting? 183 00:09:38,158 --> 00:09:39,288 (audience laughs) 184 00:09:39,290 --> 00:09:43,570 It's Lincoln at Gettysburg by author Garry Wills, 185 00:09:43,570 --> 00:09:45,580 his brilliant political, historical, 186 00:09:45,580 --> 00:09:48,900 and literary analysis of Lincoln's famous speech 187 00:09:48,900 --> 00:09:52,230 that recast the struggle for freedom and human dignity 188 00:09:52,230 --> 00:09:54,560 at a critical moment in our nation's history. 189 00:09:55,510 --> 00:09:57,280 All of our freshmen, all of our faculty, 190 00:09:57,280 --> 00:09:59,430 and hopefully our students and our colleagues 191 00:09:59,430 --> 00:10:02,190 and our friends in the community will be on the same page 192 00:10:02,190 --> 00:10:05,780 with Lincoln and Garry Wills next September. 193 00:10:05,780 --> 00:10:07,640 And this will be also co-sponsored 194 00:10:07,640 --> 00:10:11,810 as an event with Cal Performances and Zellerbach Auditorium. 195 00:10:11,810 --> 00:10:14,970 So I want to close by thanking you all, 196 00:10:14,970 --> 00:10:16,650 everyone here in Zellerbach, 197 00:10:16,650 --> 00:10:18,410 everyone out there in Wheeler Auditorium 198 00:10:18,410 --> 00:10:21,430 that is also sold out with closed-circuit broadcast, 199 00:10:21,430 --> 00:10:23,740 and everyone out there on the webcast, 200 00:10:23,740 --> 00:10:27,940 for helping us inaugurate On the Same Page this evening. 201 00:10:27,940 --> 00:10:29,460 I want to thank Robert Cole, 202 00:10:29,460 --> 00:10:30,820 the director of Cal Performances, 203 00:10:30,820 --> 00:10:33,830 for being our partner this year and in future years, 204 00:10:33,830 --> 00:10:36,110 Marjorie Shapiro, the chair of the physics department 205 00:10:36,110 --> 00:10:38,090 and her colleagues, for sharing Stephen Hawking 206 00:10:38,087 --> 00:10:41,007 and the Oppenheimer lecturer with us this evening, 207 00:10:41,010 --> 00:10:42,430 and also special thanks 208 00:10:42,430 --> 00:10:45,730 to staff members Alex Schwartz and Mary Olmstead 209 00:10:45,730 --> 00:10:49,120 who helped to make this event possible this evening. 210 00:10:49,120 --> 00:10:52,510 So without further ado, let me introduce Marvin Cohen. 211 00:10:52,510 --> 00:10:54,410 Marvin Cohen is a highly distinguished 212 00:10:54,410 --> 00:10:56,500 theoretical physicist himself, 213 00:10:56,500 --> 00:10:59,470 holder of the very prestigious position 214 00:10:59,470 --> 00:11:01,960 of University Professor in our physics department here, 215 00:11:01,960 --> 00:11:05,000 and he will introduce Professor Hawking, thank you. 216 00:11:04,998 --> 00:11:07,998 (audience applauds) 217 00:11:14,260 --> 00:11:15,250 - Thank you, Mark. 218 00:11:16,650 --> 00:11:18,380 It has been a great pleasure 219 00:11:18,380 --> 00:11:21,170 for me to serve on the Oppenheimer Lecture Committee. 220 00:11:21,170 --> 00:11:26,090 Since its inception in 1988, 1998, 221 00:11:26,090 --> 00:11:29,380 we've been privileged to have outstanding theorists 222 00:11:29,380 --> 00:11:31,290 speaking in the series. 223 00:11:31,290 --> 00:11:35,200 It started with our first speaker who was Murray Gell-Mann. 224 00:11:35,203 --> 00:11:39,843 Then we had Kip Thorne, Freeman Dyson, Frank Yang, 225 00:11:39,840 --> 00:11:44,840 Michael Fisher, our own Bruno Zumino, Robert Laughlin, 226 00:11:45,910 --> 00:11:49,630 and tonight our 10th lecturer is Stephen Hawking. 227 00:11:50,830 --> 00:11:53,920 In the early lectures, before introducing the speaker, 228 00:11:53,920 --> 00:11:56,300 I would say something about Oppenheimer 229 00:11:56,300 --> 00:11:59,050 and the history of his involvement with our department. 230 00:12:00,160 --> 00:12:01,440 However in recent years, 231 00:12:01,440 --> 00:12:03,460 I've just described the current events 232 00:12:03,460 --> 00:12:05,470 related to Oppenheimer. 233 00:12:05,470 --> 00:12:07,310 For those of you who are interested 234 00:12:07,310 --> 00:12:09,660 in learning more about Oppenheimer 235 00:12:09,660 --> 00:12:11,530 and the connection to Berkeley, 236 00:12:11,530 --> 00:12:14,250 there is considerable information on the web 237 00:12:14,250 --> 00:12:16,600 and there are a number of books on Oppenheimer. 238 00:12:17,920 --> 00:12:22,080 In 2005, we celebrated the World Year of Physics. 239 00:12:22,080 --> 00:12:25,580 The idea was to get everybody into physics. 240 00:12:25,580 --> 00:12:28,830 And it was the 100th anniversary 241 00:12:28,830 --> 00:12:33,830 of the Einstein marvelous year of 1905, 242 00:12:35,060 --> 00:12:39,750 and in that year Einstein did extraordinary work 243 00:12:39,750 --> 00:12:44,200 on the sizes of molecules, that was his thesis, 244 00:12:44,200 --> 00:12:47,250 on Brownian motion, on relativity, 245 00:12:47,250 --> 00:12:48,570 and that's when he wrote down 246 00:12:48,570 --> 00:12:52,450 that little e equals mc squared thing. 247 00:12:52,454 --> 00:12:54,514 (audience laughs) 248 00:12:54,518 --> 00:12:57,058 You see it all over Telegraph on t-shirts. 249 00:12:57,055 --> 00:12:59,265 (audience laughs) 250 00:12:59,260 --> 00:13:02,670 And he also did his research on the photoelectric effect, 251 00:13:02,670 --> 00:13:05,110 for which he later won the Nobel Prize. 252 00:13:06,520 --> 00:13:08,250 The physics community around the world 253 00:13:08,250 --> 00:13:10,410 participated in many projects 254 00:13:10,410 --> 00:13:13,570 particularly to try to interest high school students 255 00:13:13,570 --> 00:13:17,310 and to reach the public, so it was a year of outreach. 256 00:13:17,310 --> 00:13:21,610 And many projects were repeated again last year in 2006, 257 00:13:21,610 --> 00:13:24,270 and they've continued to 2007. 258 00:13:26,310 --> 00:13:29,680 And there's been a considerable effort worldwide 259 00:13:29,680 --> 00:13:32,630 to try to maintain this level of excitement 260 00:13:32,630 --> 00:13:35,720 to see whether or not we can get people to realize 261 00:13:35,720 --> 00:13:38,530 that physicists are people too 262 00:13:38,530 --> 00:13:41,100 and that it's a wonderful field to work in, 263 00:13:41,100 --> 00:13:43,390 and I view the Oppenheimer Lecture series 264 00:13:43,390 --> 00:13:44,600 as part of this effort. 265 00:13:45,970 --> 00:13:47,970 Now activities related to Oppenheimer 266 00:13:47,970 --> 00:13:51,660 intensified during this period and in the past few years, 267 00:13:51,660 --> 00:13:54,590 and several new books appeared about his life 268 00:13:54,590 --> 00:13:56,200 and about the Manhattan Project. 269 00:13:57,260 --> 00:14:00,010 A recording of a speech by Oppenheimer 270 00:14:00,010 --> 00:14:03,320 just months after the first atomic bomb test 271 00:14:03,320 --> 00:14:06,370 was found by the American Philosophical Society 272 00:14:06,370 --> 00:14:07,600 in their archives, 273 00:14:07,600 --> 00:14:10,030 and we had the opportunity here in Berkeley 274 00:14:10,030 --> 00:14:12,440 to hear this speech. 275 00:14:12,440 --> 00:14:15,940 The San Francisco Opera presented the first performance 276 00:14:15,940 --> 00:14:17,880 of the opera Doctor Atomic 277 00:14:17,880 --> 00:14:22,690 about Oppenheimer and the first atomic bomb tests. 278 00:14:22,690 --> 00:14:25,860 There were discussions about Oppenheimer on campus, 279 00:14:25,860 --> 00:14:29,770 about ethics and science and about physics. 280 00:14:29,770 --> 00:14:34,290 I participated in some of these, and I was very impressed 281 00:14:34,290 --> 00:14:36,890 by the large interest of our community. 282 00:14:38,040 --> 00:14:39,590 Now one area of physics 283 00:14:41,289 --> 00:14:44,069 in which Oppenheimer made seminal contributions 284 00:14:44,070 --> 00:14:47,980 is associated with objects that later became called, 285 00:14:47,980 --> 00:14:50,380 later were called black holes. 286 00:14:50,380 --> 00:14:52,470 Stephen Hawking is also known 287 00:14:52,470 --> 00:14:55,370 for his seminal work in this area, 288 00:14:55,370 --> 00:14:57,990 and like Oppenheimer, he is widely known 289 00:14:57,990 --> 00:15:00,370 by the public at large. 290 00:15:00,370 --> 00:15:03,730 And the mention of his name is also a catalyst 291 00:15:03,730 --> 00:15:08,170 for initiating intellectual and stimulating discussions. 292 00:15:09,430 --> 00:15:13,590 As I indicated, we have tried to make the series of lectures 293 00:15:15,090 --> 00:15:17,210 exciting and accessible 294 00:15:17,210 --> 00:15:20,690 despite the technical nature of the lectures. 295 00:15:20,690 --> 00:15:23,850 There were talks on quarks and quasiparticles, 296 00:15:23,850 --> 00:15:28,260 symmetries and supersymmetries, galaxies and strings, 297 00:15:28,260 --> 00:15:31,180 and these were given by gifted lecturers, 298 00:15:31,180 --> 00:15:35,350 using pictures and equations and logical arguments 299 00:15:35,350 --> 00:15:39,170 in an attempt to convince us all, you and us, 300 00:15:39,170 --> 00:15:42,270 that we can understand much of what nature is about 301 00:15:42,270 --> 00:15:44,020 using these tools. 302 00:15:44,940 --> 00:15:47,810 Tonight, we are very fortunate to have the opportunity 303 00:15:47,810 --> 00:15:50,850 to continue our physics outreach program 304 00:15:50,850 --> 00:15:52,240 with an Oppenheimer lecture 305 00:15:52,240 --> 00:15:55,650 presented by Professor Stephen Hawking, 306 00:15:55,650 --> 00:15:58,030 who is at Cambridge University 307 00:15:58,030 --> 00:16:00,670 where he joined the department of applied mathematics 308 00:16:00,670 --> 00:16:04,130 and theoretical physics in 1973. 309 00:16:04,130 --> 00:16:06,890 Since 1979, he has held the post 310 00:16:06,890 --> 00:16:09,450 of Lucasian Professor of Mathematics. 311 00:16:09,450 --> 00:16:12,320 This chair was once held by Isaac Newton. 312 00:16:13,700 --> 00:16:16,260 Professor Hawking has visited Berkeley before 313 00:16:16,260 --> 00:16:18,780 and he's lectured here in the past. 314 00:16:18,780 --> 00:16:21,160 I first met him in 1988 315 00:16:21,160 --> 00:16:24,860 when he spent time here as a Hitchcock lecturer. 316 00:16:24,860 --> 00:16:27,960 He gave talks and interacted with many of us, 317 00:16:27,960 --> 00:16:31,020 both scientifically and socially. 318 00:16:31,020 --> 00:16:32,460 His technical lectures 319 00:16:32,460 --> 00:16:35,340 for members of our faculty and students 320 00:16:35,340 --> 00:16:39,370 on cosmology and astrophysics were usually focused 321 00:16:39,370 --> 00:16:41,760 on subjects he was currently working on 322 00:16:41,760 --> 00:16:43,860 such as black holes. 323 00:16:43,860 --> 00:16:45,400 In addition, we were fortunate 324 00:16:45,400 --> 00:16:48,060 to have him give general public lectures 325 00:16:48,060 --> 00:16:51,140 on slightly broader subjects like tonight's lecture, 326 00:16:51,140 --> 00:16:52,940 which is on a fairly broad subject, 327 00:16:52,940 --> 00:16:54,320 the origin of the universe. 328 00:16:54,322 --> 00:16:57,842 (audience laughs) 329 00:16:57,840 --> 00:16:59,290 It's not easy for me 330 00:16:59,290 --> 00:17:01,230 as Chair of the Oppenheimer Lecture series 331 00:17:01,230 --> 00:17:03,490 to come up with a stimulating speaker 332 00:17:03,490 --> 00:17:07,410 who can excite both an academic and public audience. 333 00:17:07,410 --> 00:17:09,360 For this reason, I was particularly happy 334 00:17:09,360 --> 00:17:11,660 when Stephen agreed to come. 335 00:17:11,660 --> 00:17:13,270 This was about four years ago 336 00:17:13,270 --> 00:17:16,400 when we met at London's Heathrow Airport. 337 00:17:16,400 --> 00:17:20,950 I was coming from Edinburgh and he was going to China. 338 00:17:20,950 --> 00:17:22,840 I was complaining about being tired 339 00:17:22,840 --> 00:17:25,200 from my short flight from Edinburgh, 340 00:17:25,200 --> 00:17:27,540 while he was calmly eating lunch 341 00:17:27,540 --> 00:17:30,350 with the look of someone enjoying the anticipation 342 00:17:30,350 --> 00:17:33,120 of another adventure, and I felt guilty. 343 00:17:34,380 --> 00:17:36,410 I was reminded of this again recently 344 00:17:36,410 --> 00:17:39,940 when I read an article about Stephen's current plans. 345 00:17:39,940 --> 00:17:44,710 When I turned 65, I thought that maybe I should retire 346 00:17:44,710 --> 00:17:49,310 and play checkers in the sun and things of this kind. 347 00:17:49,310 --> 00:17:53,280 In contrast, Stephen turned 65 this year, 348 00:17:53,280 --> 00:17:56,670 and he has decided to take a zero gravity ride 349 00:17:56,670 --> 00:17:58,230 out of Cape Canaveral 350 00:17:58,228 --> 00:18:00,348 (audience laughs) 351 00:18:00,350 --> 00:18:02,490 in a so-called vomit comet. 352 00:18:02,493 --> 00:18:05,323 (audience laughs) 353 00:18:06,250 --> 00:18:08,460 During his flight, he will experience 354 00:18:08,460 --> 00:18:10,600 the feeling of being weightless 355 00:18:10,600 --> 00:18:13,080 and also the feeling of being very very heavy. 356 00:18:14,050 --> 00:18:17,610 I understand this event is planned for next month. 357 00:18:18,920 --> 00:18:22,690 And if that isn't enough, in 2009, 358 00:18:22,690 --> 00:18:26,210 Stephen plans a longer and higher flight 359 00:18:26,210 --> 00:18:28,800 in a space plane being developed now 360 00:18:28,800 --> 00:18:31,790 to reach an altitude of 75 miles. 361 00:18:33,440 --> 00:18:35,820 When he's not on a space mission, 362 00:18:35,820 --> 00:18:38,120 Stephen Hawking does research, 363 00:18:38,120 --> 00:18:40,670 he lectures to broad audiences, 364 00:18:40,670 --> 00:18:44,280 and he writes very popular books. 365 00:18:44,280 --> 00:18:46,440 He's an inspiration to those 366 00:18:46,440 --> 00:18:51,440 who feel they are challenged and limited in some way, 367 00:18:51,850 --> 00:18:53,920 and that includes all of us. 368 00:18:54,990 --> 00:18:57,920 Right now, I feel more challenged than anyone here 369 00:18:57,920 --> 00:19:01,560 because I have to think of next year's Oppenheimer Lecture. 370 00:19:01,563 --> 00:19:02,393 (audience laughs) 371 00:19:02,396 --> 00:19:06,026 And this is going to be a very hard act to follow. 372 00:19:06,030 --> 00:19:09,950 So please join me in welcoming Stephen Hawking. 373 00:19:09,946 --> 00:19:12,946 (audience applauds) 374 00:20:04,128 --> 00:20:04,958 (machine beeps) 375 00:20:04,961 --> 00:20:06,881 - [Aide] Any questions? 376 00:20:57,333 --> 00:20:59,543 - [Stephen] Can you hear me? 377 00:20:59,544 --> 00:21:00,964 - [Audience] Yes. 378 00:21:03,959 --> 00:21:06,789 (audience laughs) 379 00:21:10,090 --> 00:21:12,240 - [Stephen] According to the Boshongo people 380 00:21:12,240 --> 00:21:13,760 of Central Africa, 381 00:21:13,760 --> 00:21:16,670 in the beginning, there was only darkness, 382 00:21:16,670 --> 00:21:18,290 water, and the great god Bumba. 383 00:21:23,197 --> 00:21:26,667 One day, Bumba, in pain from a stomach ache, 384 00:21:26,670 --> 00:21:28,020 vomited up the sun. 385 00:21:29,264 --> 00:21:32,804 The sun dried up some of the water, leaving land. 386 00:21:37,720 --> 00:21:40,960 Still in pain, Bumba vomited up the moon, 387 00:21:40,960 --> 00:21:44,730 the stars, and then some animals, 388 00:21:44,730 --> 00:21:47,590 the leopard, the crocodile, the turtle, 389 00:21:47,590 --> 00:21:50,180 and finally man. 390 00:21:58,290 --> 00:22:01,350 This creation myth, like many others, 391 00:22:01,350 --> 00:22:05,360 tries to answer the questions we all ask. 392 00:22:05,360 --> 00:22:07,600 Why are we here? 393 00:22:07,600 --> 00:22:09,390 Where did we come from? 394 00:22:12,790 --> 00:22:14,370 The answer generally given 395 00:22:14,370 --> 00:22:18,890 was that humans were of comparatively recent origin 396 00:22:18,890 --> 00:22:23,020 because it must have been obvious even at early times 397 00:22:23,020 --> 00:22:25,330 that the human race was improving 398 00:22:25,330 --> 00:22:27,160 in knowledge and technology. 399 00:22:28,190 --> 00:22:31,000 So it can't have been around that long 400 00:22:31,000 --> 00:22:33,300 or it would have progressed even more. 401 00:22:40,740 --> 00:22:44,240 For example, according to Bishop Usher, 402 00:22:44,240 --> 00:22:47,140 the book of Genesis placed the creation of the world 403 00:22:47,140 --> 00:22:48,870 at nine in the morning 404 00:22:48,870 --> 00:22:53,550 on October the 27th, 4004 BC. 405 00:22:53,553 --> 00:22:56,383 (audience laughs) 406 00:23:04,190 --> 00:23:07,840 On the other hand, the physical surroundings, 407 00:23:07,840 --> 00:23:09,730 like mountains and rivers, 408 00:23:09,730 --> 00:23:12,650 change very little in a human lifetime. 409 00:23:13,700 --> 00:23:17,170 They were therefore thought to be a constant background 410 00:23:17,170 --> 00:23:21,150 and either to have existed forever as an empty landscape 411 00:23:21,150 --> 00:23:24,820 or to have been created at the same time as the humans. 412 00:23:38,340 --> 00:23:41,680 Not everyone, however, was happy with the idea 413 00:23:41,680 --> 00:23:43,910 that the universe had a beginning. 414 00:23:45,000 --> 00:23:47,290 For example, Aristotle, 415 00:23:47,290 --> 00:23:50,320 the most famous of the Greek philosophers, 416 00:23:50,320 --> 00:23:54,180 believed the universe had existed forever. 417 00:23:54,180 --> 00:23:58,520 Something eternal is more perfect than something created. 418 00:24:01,880 --> 00:24:04,960 He suggested the reason we see progress 419 00:24:04,960 --> 00:24:08,710 was that floods or other natural disasters 420 00:24:08,710 --> 00:24:12,820 had repeatedly set civilization back to the beginning. 421 00:24:20,160 --> 00:24:23,840 The motivation for believing in an eternal universe 422 00:24:23,837 --> 00:24:27,597 was the desire to avoid invoking divine intervention 423 00:24:27,600 --> 00:24:30,680 to create the universe and set it going. 424 00:24:36,030 --> 00:24:40,230 Conversely, those who believed the universe had a beginning 425 00:24:40,230 --> 00:24:43,680 used it as an argument for the existence of God 426 00:24:43,680 --> 00:24:47,810 as the first cause or prime mover of the universe. 427 00:24:53,020 --> 00:24:56,460 If one believed that the universe had a beginning, 428 00:24:56,460 --> 00:25:01,460 the obvious question was what happened before the beginning? 429 00:25:01,760 --> 00:25:04,780 What was God doing before he made the world? 430 00:25:05,810 --> 00:25:09,790 Was he preparing hell for people who asked such questions? 431 00:25:09,793 --> 00:25:12,623 (audience laughs) 432 00:25:24,480 --> 00:25:28,330 The problem of whether or not the universe had a beginning 433 00:25:28,330 --> 00:25:29,700 was a great concern 434 00:25:29,700 --> 00:25:33,120 to the German philosopher Immanuel Kant. 435 00:25:37,040 --> 00:25:40,330 He felt there were logical contradictions 436 00:25:40,330 --> 00:25:43,130 or antimonies either way. 437 00:25:49,756 --> 00:25:51,866 If the universe had a beginning, 438 00:25:51,870 --> 00:25:55,250 why did it wait an infinite time before it began? 439 00:25:56,250 --> 00:25:58,340 He called that the thesis. 440 00:26:01,840 --> 00:26:05,980 On the other hand, if the universe had existed forever, 441 00:26:05,977 --> 00:26:10,327 why did it take an infinite time to reach the present stage? 442 00:26:11,340 --> 00:26:13,800 He called that the antithesis. 443 00:26:18,560 --> 00:26:20,640 Both the thesis and the antithesis 444 00:26:21,510 --> 00:26:23,830 depended on Kant's assumption, 445 00:26:23,830 --> 00:26:28,470 along with almost everyone else, that time was absolute. 446 00:26:29,530 --> 00:26:33,400 That is to say, it went from the infinite past 447 00:26:33,400 --> 00:26:37,350 to the infinite future independently of any universe 448 00:26:37,350 --> 00:26:40,390 that might or might not exist in this background. 449 00:26:46,770 --> 00:26:48,320 This is still the picture 450 00:26:48,320 --> 00:26:51,600 in the mind of many scientists today. 451 00:26:51,603 --> 00:26:55,543 However in 1915, Einstein introduced 452 00:26:55,540 --> 00:26:59,090 his revolutionary general theory of relativity. 453 00:27:03,659 --> 00:27:07,519 In this, space and time were no longer absolute, 454 00:27:07,520 --> 00:27:10,480 no longer a fixed background to events. 455 00:27:11,490 --> 00:27:15,290 Instead, they were dynamical quantities that were shaped 456 00:27:15,290 --> 00:27:18,000 by the matter and energy in the universe. 457 00:27:21,840 --> 00:27:24,690 They were defined only within the universe, 458 00:27:24,690 --> 00:27:26,520 so it made no sense 459 00:27:26,520 --> 00:27:29,730 to talk of a time before the universe began. 460 00:27:30,750 --> 00:27:35,040 It would be like asking for a point south of the South Pole. 461 00:27:35,933 --> 00:27:37,313 It is not defined. 462 00:27:43,970 --> 00:27:47,720 If the universe was essentially unchanging in time, 463 00:27:47,720 --> 00:27:51,770 as was generally assumed before the 1920s, 464 00:27:51,770 --> 00:27:53,680 there would be no reason 465 00:27:53,680 --> 00:27:57,870 that time should not be defined arbitrarily far back. 466 00:28:02,060 --> 00:28:06,520 Any so-called beginning of the universe would be artificial 467 00:28:06,520 --> 00:28:09,130 in the sense that one could extend the history 468 00:28:09,130 --> 00:28:11,040 back to earlier times. 469 00:28:21,180 --> 00:28:25,080 Thus, it might be that the universe was created last year, 470 00:28:25,080 --> 00:28:28,280 but with all the memories and physical evidence 471 00:28:28,280 --> 00:28:30,490 to look like it was much older. 472 00:28:35,610 --> 00:28:38,400 This raises deep philosophical questions 473 00:28:38,400 --> 00:28:40,560 about the meaning of existence. 474 00:28:41,560 --> 00:28:42,760 I shall deal with these 475 00:28:42,760 --> 00:28:46,270 by adopting what is called the positivist approach. 476 00:28:51,013 --> 00:28:54,493 In this, the idea is that we interpret the input 477 00:28:54,490 --> 00:28:58,970 from our senses in terms of the model we make of the world. 478 00:29:00,220 --> 00:29:03,790 One cannot ask whether the model represents reality, 479 00:29:03,790 --> 00:29:05,620 only whether it works. 480 00:29:11,690 --> 00:29:13,580 A model is a good model 481 00:29:13,580 --> 00:29:17,370 if first it interprets a wide range of observations 482 00:29:17,370 --> 00:29:19,720 in terms of a simple and elegant model, 483 00:29:21,070 --> 00:29:24,650 and second, if the model makes definite predictions 484 00:29:24,650 --> 00:29:29,650 that can be tested and possibly falsified by observation. 485 00:29:38,300 --> 00:29:40,930 In terms of the positivist approach, 486 00:29:40,930 --> 00:29:45,010 one can compare two models of the universe, 487 00:29:45,007 --> 00:29:48,347 one in which the universe was created last year 488 00:29:48,350 --> 00:29:51,190 and one in which the universe existed much longer. 489 00:30:02,320 --> 00:30:04,660 The model in which the universe existed 490 00:30:04,660 --> 00:30:06,450 for longer than a year 491 00:30:06,450 --> 00:30:09,540 can explain things like identical twins 492 00:30:09,540 --> 00:30:12,990 that have a common cause more than a year ago. 493 00:30:18,240 --> 00:30:19,810 On the other hand, 494 00:30:19,810 --> 00:30:23,340 the model in which the universe was created last year 495 00:30:23,340 --> 00:30:25,620 cannot explain such events. 496 00:30:26,630 --> 00:30:29,720 So the first model is better. 497 00:30:29,720 --> 00:30:32,990 One cannot ask whether the universe really existed 498 00:30:32,990 --> 00:30:36,180 before a year ago or just appeared to. 499 00:30:37,334 --> 00:30:40,104 In the positivist approach, they are the same. 500 00:30:56,348 --> 00:30:58,238 In an unchanging universe, 501 00:30:58,240 --> 00:31:00,910 there would be no natural starting point. 502 00:31:02,410 --> 00:31:05,400 The situation changed radically however 503 00:31:05,400 --> 00:31:07,970 when Edwin Hubble began to make observations 504 00:31:07,970 --> 00:31:12,970 with the 100-inch telescope on Mount Wilson in the 1920s. 505 00:31:19,200 --> 00:31:20,730 Hubble found that stars 506 00:31:20,730 --> 00:31:24,050 are not uniformly distributed throughout space, 507 00:31:24,050 --> 00:31:25,400 but are gathered together 508 00:31:25,400 --> 00:31:28,390 in vast collections called galaxies. 509 00:31:33,940 --> 00:31:37,200 By measuring the light from galaxies, 510 00:31:37,200 --> 00:31:39,630 Hubble could determine their velocities. 511 00:31:40,670 --> 00:31:43,140 He was expecting that as many galaxies 512 00:31:43,140 --> 00:31:47,320 would be moving towards us as were moving away. 513 00:31:48,170 --> 00:31:50,850 This is what one would have in a universe 514 00:31:50,850 --> 00:31:53,130 that was unchanging with time. 515 00:31:58,370 --> 00:32:01,000 But to his surprise, Hubble found 516 00:32:01,000 --> 00:32:04,710 that nearly all the galaxies were moving away from us. 517 00:32:05,730 --> 00:32:09,200 Moreover, the further galaxies were from us, 518 00:32:09,200 --> 00:32:11,630 the faster they were moving away. 519 00:32:17,260 --> 00:32:20,350 The universe was not unchanging with time 520 00:32:20,350 --> 00:32:22,860 as everyone had thought previously. 521 00:32:23,890 --> 00:32:25,000 It was expanding. 522 00:32:26,460 --> 00:32:29,310 The distance between distant galaxies 523 00:32:29,310 --> 00:32:31,050 was increasing with time. 524 00:32:40,290 --> 00:32:42,320 The expansion of the universe 525 00:32:42,320 --> 00:32:46,330 was one of the most important intellectual discoveries 526 00:32:46,330 --> 00:32:49,760 of the 20th century or of any century. 527 00:32:54,130 --> 00:32:55,680 It transformed the debate 528 00:32:55,680 --> 00:32:58,470 about whether the universe had a beginning. 529 00:32:59,510 --> 00:33:02,260 If galaxies are moving apart now, 530 00:33:02,260 --> 00:33:05,480 they must have been closer together in the past. 531 00:33:06,540 --> 00:33:08,880 If their speed had been constant, 532 00:33:08,880 --> 00:33:11,930 they would all have been on top of one another 533 00:33:11,930 --> 00:33:15,610 about 15 billion years ago. 534 00:33:15,610 --> 00:33:18,750 Was this the beginning of the universe? 535 00:33:25,600 --> 00:33:27,870 Many scientists were still unhappy 536 00:33:27,870 --> 00:33:30,660 with the universe having a beginning 537 00:33:30,661 --> 00:33:34,341 because it seemed to imply that physics broke down. 538 00:33:39,280 --> 00:33:42,360 One would have to invoke an outside agency, 539 00:33:42,360 --> 00:33:45,840 which for convenience one can call God, 540 00:33:45,840 --> 00:33:47,950 to determine how the universe began. 541 00:33:57,970 --> 00:33:59,860 They therefore advanced theories 542 00:33:59,860 --> 00:34:04,150 in which the universe was expanding at the present time 543 00:34:04,150 --> 00:34:06,170 but didn't have a beginning. 544 00:34:11,525 --> 00:34:13,855 One was the steady state theory 545 00:34:13,850 --> 00:34:18,600 proposed by Bondi, Gold, and Hoyle in 1948. 546 00:34:24,455 --> 00:34:28,525 In the steady state theory, as galaxies moved apart, 547 00:34:28,520 --> 00:34:31,890 the idea was that new galaxies would form from matter 548 00:34:31,890 --> 00:34:35,160 that was supposed to be continually being created 549 00:34:35,160 --> 00:34:36,460 throughout space. 550 00:34:44,030 --> 00:34:46,820 The universe would have existed forever 551 00:34:46,820 --> 00:34:49,600 and would have looked the same at all times. 552 00:34:55,700 --> 00:34:58,700 This last property had the great virtue, 553 00:34:58,700 --> 00:35:01,320 from a positivist point of view, 554 00:35:01,320 --> 00:35:03,570 of being a definite prediction 555 00:35:03,570 --> 00:35:06,170 that could be tested by observation. 556 00:35:16,030 --> 00:35:20,430 The Cambridge Radio Astronomy Group, under Martin Ryle, 557 00:35:20,430 --> 00:35:25,110 did a survey of weak radio sources in the early 1960s. 558 00:35:32,840 --> 00:35:36,740 These were distributed fairly uniformly across the sky, 559 00:35:36,740 --> 00:35:41,500 indicating that most of the sources lay outside our galaxy. 560 00:35:42,540 --> 00:35:46,420 The weaker sources would be further away on average. 561 00:35:55,210 --> 00:35:57,740 The steady state theory predicted the shape 562 00:35:57,740 --> 00:36:00,410 of the graph of the number of sources 563 00:36:00,410 --> 00:36:02,150 against source strength. 564 00:36:07,510 --> 00:36:09,280 But the observations showed 565 00:36:09,280 --> 00:36:11,820 more faint sources than predicted, 566 00:36:11,820 --> 00:36:15,840 indicating that the density sources was higher in the past. 567 00:36:16,890 --> 00:36:19,690 This was contrary to the basic assumption 568 00:36:19,690 --> 00:36:21,600 of the steady state theory, 569 00:36:21,600 --> 00:36:24,140 that everything was constant in time. 570 00:36:31,250 --> 00:36:33,860 For this and other reasons, 571 00:36:33,860 --> 00:36:36,520 the steady state theory was abandoned. 572 00:36:44,550 --> 00:36:48,560 Another attempt to avoid the universe having a beginning 573 00:36:48,561 --> 00:36:49,671 was the suggestion 574 00:36:49,670 --> 00:36:52,890 that there was a previous contracting phase, 575 00:36:52,890 --> 00:36:56,660 but because of rotation and local irregularities, 576 00:36:56,660 --> 00:36:59,540 the matter would not all fall to the same point. 577 00:37:09,270 --> 00:37:11,880 Instead, different parts of the matter 578 00:37:11,880 --> 00:37:13,490 would miss each other, 579 00:37:13,492 --> 00:37:15,742 and the universe would expand again 580 00:37:15,740 --> 00:37:18,240 with the density remaining finite. 581 00:37:24,270 --> 00:37:27,530 Two Russians, Lifshitz and Khalatnikov, 582 00:37:27,530 --> 00:37:29,510 actually claimed to have proved 583 00:37:29,510 --> 00:37:33,030 that a general contraction without exact symmetry 584 00:37:33,030 --> 00:37:35,160 would always lead to a bounce 585 00:37:35,160 --> 00:37:37,670 with the density remaining finite. 586 00:37:45,100 --> 00:37:47,180 This result was very convenient 587 00:37:47,180 --> 00:37:50,990 for Marxist Leninist dialectical materialism 588 00:37:50,990 --> 00:37:53,200 because it avoided awkward questions 589 00:37:53,200 --> 00:37:55,740 about the creation of the universe. 590 00:37:56,710 --> 00:37:58,870 It therefore became an article of faith 591 00:37:58,870 --> 00:38:00,960 for Soviet scientists. 592 00:38:05,890 --> 00:38:09,300 When Lifshitz and Khalatnikov published their claim, 593 00:38:09,300 --> 00:38:12,760 I was a 21-year-old research student 594 00:38:12,760 --> 00:38:17,030 looking for something to complete my PhD thesis. 595 00:38:25,900 --> 00:38:28,780 I didn't believe their so-called proof 596 00:38:28,780 --> 00:38:30,700 and set out with Roger Penrose 597 00:38:30,700 --> 00:38:33,120 to develop new mathematical techniques 598 00:38:33,120 --> 00:38:34,660 to study the question. 599 00:38:39,370 --> 00:38:42,250 We showed that the universe couldn't bounce. 600 00:38:43,270 --> 00:38:47,270 If Einstein's general theory of relativity is correct, 601 00:38:47,270 --> 00:38:48,670 there will be a singularity, 602 00:38:49,580 --> 00:38:53,250 a point of infinite density and spacetime curvature 603 00:38:53,250 --> 00:38:55,300 where time has a beginning. 604 00:39:00,520 --> 00:39:03,800 Observational evidence to confirm the idea 605 00:39:03,800 --> 00:39:06,900 that the universe had a very dense beginning 606 00:39:06,900 --> 00:39:10,110 came in October 1965, 607 00:39:10,110 --> 00:39:14,140 a few months after my first singularity result 608 00:39:14,140 --> 00:39:16,580 with the discovery of a faint background 609 00:39:16,580 --> 00:39:18,920 of microwaves throughout space. 610 00:39:26,660 --> 00:39:28,550 These microwaves are the same 611 00:39:28,550 --> 00:39:31,120 as those in your microwave oven, 612 00:39:31,120 --> 00:39:32,860 but very much less powerful. 613 00:39:34,200 --> 00:39:36,170 They would heat your pizza only 614 00:39:36,170 --> 00:39:40,440 to minus 271.3 degrees centigrade, 615 00:39:40,440 --> 00:39:43,350 not much good for defrosting the pizza, 616 00:39:43,350 --> 00:39:45,420 let alone cooking it. 617 00:39:45,415 --> 00:39:48,245 (audience laughs) 618 00:39:52,810 --> 00:39:56,510 You can actually observe these microwaves yourself. 619 00:39:57,510 --> 00:40:00,420 Set your television to an empty channel. 620 00:40:01,440 --> 00:40:04,660 A few percent of the snow you see on the screen 621 00:40:04,660 --> 00:40:08,120 will be caused by this background of microwaves. 622 00:40:18,970 --> 00:40:22,600 The only reasonable interpretation of the background 623 00:40:22,600 --> 00:40:24,830 is that it is radiation left over 624 00:40:24,830 --> 00:40:27,520 from an early very hot and dense state. 625 00:40:28,610 --> 00:40:32,560 As the universe expanded, the radiation would have cooled 626 00:40:32,560 --> 00:40:36,290 until it is just the faint remnant we observe today. 627 00:40:43,010 --> 00:40:47,290 Although the singularity theorems of Penrose and myself 628 00:40:47,290 --> 00:40:50,170 predicted that the universe had a beginning, 629 00:40:50,170 --> 00:40:52,180 they didn't say how it had begun. 630 00:40:56,450 --> 00:40:58,940 The equations of general relativity 631 00:40:58,940 --> 00:41:01,460 would break down at the singularity. 632 00:41:02,500 --> 00:41:05,160 Thus, Einstein's theory cannot predict 633 00:41:05,160 --> 00:41:07,200 how the universe will begin, 634 00:41:07,200 --> 00:41:09,860 but only how it will evolve once it has begun. 635 00:41:17,500 --> 00:41:20,120 There are two attitudes one can take 636 00:41:20,120 --> 00:41:22,970 to the results of Penrose and myself. 637 00:41:23,980 --> 00:41:27,490 One is to that God chose how the universe began 638 00:41:27,490 --> 00:41:30,100 for reasons we could not understand. 639 00:41:35,890 --> 00:41:38,910 This was the view of Pope John Paul. 640 00:41:41,580 --> 00:41:44,920 At a conference on cosmology in the Vatican, 641 00:41:44,920 --> 00:41:47,950 the pope told the delegates that it was okay 642 00:41:47,950 --> 00:41:51,350 to study the universe after it began, 643 00:41:51,354 --> 00:41:54,184 (audience laughs) 644 00:41:55,330 --> 00:41:58,910 but they should not inquire into the beginning itself 645 00:41:58,910 --> 00:42:01,440 because that was the moment of creation 646 00:42:01,440 --> 00:42:02,810 and the work of God. 647 00:42:06,800 --> 00:42:08,890 I was glad he didn't realize 648 00:42:08,890 --> 00:42:12,050 I had presented a paper at the conference 649 00:42:12,050 --> 00:42:14,700 suggesting how the universe began. 650 00:42:15,750 --> 00:42:18,840 I didn't fancy the thought of being handed over 651 00:42:18,840 --> 00:42:22,050 to the Inquisition like Galileo. 652 00:42:22,047 --> 00:42:25,047 (audience applauds) 653 00:42:46,520 --> 00:42:49,730 The other interpretation of our results, 654 00:42:49,730 --> 00:42:52,500 which is favored by most scientists, 655 00:42:52,500 --> 00:42:56,350 is that it indicates that the general theory of relativity 656 00:42:56,350 --> 00:42:59,800 breaks down in the very strong gravitational fields 657 00:42:59,800 --> 00:43:01,440 in the early universe. 658 00:43:05,380 --> 00:43:08,620 It has to be replaced by a more complete theory. 659 00:43:17,550 --> 00:43:19,530 One would expect this anyway 660 00:43:19,530 --> 00:43:22,790 because general relativity does not take account 661 00:43:22,790 --> 00:43:25,380 of the small-scale structure of matter, 662 00:43:25,380 --> 00:43:27,780 which is governed by quantum theory. 663 00:43:39,750 --> 00:43:41,920 This does not matter normally 664 00:43:41,920 --> 00:43:44,900 because the scale of the universe is enormous 665 00:43:44,900 --> 00:43:48,740 compared to the microscopic scales of quantum theory. 666 00:43:49,830 --> 00:43:52,820 But when the universe is the Planck size, 667 00:43:52,820 --> 00:43:55,980 a billion trillion trillionth of a centimeter, 668 00:43:55,980 --> 00:43:57,880 the two scales are the same 669 00:43:57,880 --> 00:44:01,260 and quantum theory has to be taken into account. 670 00:44:15,810 --> 00:44:19,320 In order to understand the origin of the universe, 671 00:44:19,319 --> 00:44:22,869 we need to combine the general theory of relativity 672 00:44:22,870 --> 00:44:24,340 with quantum theory. 673 00:44:27,950 --> 00:44:30,840 The best way of doing so seems to be 674 00:44:30,840 --> 00:44:34,420 to use Feynman's idea of a sum over histories. 675 00:44:43,340 --> 00:44:46,550 Richard Feynman was a colorful character 676 00:44:46,550 --> 00:44:50,640 who played the bongo drums in a strip joint in Pasadena 677 00:44:50,640 --> 00:44:52,460 and was a brilliant physicist 678 00:44:52,460 --> 00:44:55,450 at the California Institute of Technology. 679 00:45:00,440 --> 00:45:05,220 He proposed that a system got from a state A to a state B 680 00:45:05,220 --> 00:45:07,830 by every possible path or history. 681 00:45:13,470 --> 00:45:18,060 Each path or history has a certain amplitude or intensity, 682 00:45:18,060 --> 00:45:21,800 and the probability of the system going from A to B 683 00:45:21,800 --> 00:45:25,340 is given by adding up the amplitudes for each path. 684 00:45:31,580 --> 00:45:33,030 There will be a history 685 00:45:33,030 --> 00:45:36,000 in which the moon is made of blue cheese, 686 00:45:36,000 --> 00:45:40,020 but the amplitude is low, which is bad news for mice. 687 00:45:40,020 --> 00:45:42,850 (audience laughs) 688 00:45:54,050 --> 00:45:56,930 The probability for a state of the universe 689 00:45:56,930 --> 00:46:00,850 at the present time is given by adding up the amplitudes 690 00:46:00,850 --> 00:46:03,720 for all the histories that end with that state. 691 00:46:11,160 --> 00:46:13,150 But how did the histories start? 692 00:46:14,310 --> 00:46:17,020 This is the origin question in another guise. 693 00:46:21,060 --> 00:46:25,000 Does it require a creator to decree how the universe began, 694 00:46:26,010 --> 00:46:28,590 or is the initial state of the universe 695 00:46:28,590 --> 00:46:31,020 determined by a law of science? 696 00:46:44,930 --> 00:46:47,500 In fact, this question would arise 697 00:46:47,504 --> 00:46:50,024 even if the histories of the universe 698 00:46:50,020 --> 00:46:52,120 went back to the infinite past, 699 00:46:53,240 --> 00:46:54,410 but it is more immediate 700 00:46:54,410 --> 00:46:58,500 if the universe began only 15 billion years ago. 701 00:47:07,000 --> 00:47:10,590 The problem of what happens at the beginning of time 702 00:47:10,590 --> 00:47:13,120 is a bit like the question of what happened 703 00:47:13,120 --> 00:47:14,870 at the edge of the world 704 00:47:14,870 --> 00:47:17,740 when people thought the world was flat. 705 00:47:25,300 --> 00:47:27,420 Is the world a flat plate 706 00:47:27,420 --> 00:47:29,970 with the sea pouring over the edge? 707 00:47:31,010 --> 00:47:32,870 I have tested this experimentally. 708 00:47:34,630 --> 00:47:38,220 I have been round the world and I have not fallen off. 709 00:47:50,150 --> 00:47:51,600 As we all know, 710 00:47:51,600 --> 00:47:55,110 the problem of what happens at the edge of the world 711 00:47:55,110 --> 00:47:57,190 was solved when people realized 712 00:47:57,190 --> 00:48:01,650 that the world was not a flat plate, but a curved surface. 713 00:48:05,520 --> 00:48:08,330 Time, however, seemed to be different. 714 00:48:09,460 --> 00:48:12,280 It appeared to be separate from space 715 00:48:12,280 --> 00:48:14,780 and to be like a model railway track. 716 00:48:15,820 --> 00:48:19,180 If it had a beginning, there would have to be someone 717 00:48:19,180 --> 00:48:20,990 to set the trains going. 718 00:48:28,940 --> 00:48:31,970 Einstein's general theory of relativity 719 00:48:31,970 --> 00:48:34,920 unified time and space as spacetime, 720 00:48:34,920 --> 00:48:37,820 but time was still different from space 721 00:48:37,820 --> 00:48:39,640 and was like a corridor, 722 00:48:39,640 --> 00:48:43,730 which either had a beginning and end or went on forever. 723 00:48:49,320 --> 00:48:52,810 However, when one combines general relativity 724 00:48:52,810 --> 00:48:56,510 with quantum theory, Jim Hartle and I realized 725 00:48:56,510 --> 00:48:59,930 that time can behave like another direction in space 726 00:48:59,930 --> 00:49:01,850 under extreme conditions. 727 00:49:11,080 --> 00:49:13,750 This means one can get rid of the problem 728 00:49:13,750 --> 00:49:16,850 of time having a beginning in a similar way 729 00:49:16,850 --> 00:49:19,670 in which we got rid of the edge of the world. 730 00:49:24,430 --> 00:49:27,040 Suppose the beginning of the universe 731 00:49:27,040 --> 00:49:29,620 was like the South Pole of the Earth 732 00:49:29,620 --> 00:49:33,460 with degrees of latitude playing the role of time. 733 00:49:41,720 --> 00:49:46,410 The universe would start as a point at the South Pole. 734 00:49:46,410 --> 00:49:50,740 As one moves north, the circles of constant latitude, 735 00:49:50,740 --> 00:49:54,680 representing the size of the universe, would expand. 736 00:49:57,700 --> 00:50:01,400 To ask what happened before the beginning of the universe 737 00:50:01,400 --> 00:50:03,760 would become a meaningless question 738 00:50:03,760 --> 00:50:07,270 because there is nothing south of the South Pole. 739 00:50:15,010 --> 00:50:18,320 Time, as measured in degrees of latitude, 740 00:50:18,320 --> 00:50:21,100 would have a beginning at the South Pole, 741 00:50:21,100 --> 00:50:24,640 but the South Pole is much like any other point, 742 00:50:24,640 --> 00:50:27,080 at least so I have been told. 743 00:50:27,940 --> 00:50:32,160 I have been to Antarctica, but not to the South Pole. 744 00:50:38,120 --> 00:50:41,710 The same laws of nature hold at the South Pole 745 00:50:41,710 --> 00:50:43,590 as in other places. 746 00:50:44,610 --> 00:50:47,140 This would remove the age-old objection 747 00:50:47,140 --> 00:50:49,720 to the universe having a beginning, 748 00:50:49,720 --> 00:50:53,320 that it would be a place where the normal laws broke down. 749 00:50:54,508 --> 00:50:56,438 The beginning of the universe 750 00:50:56,440 --> 00:50:59,450 would be governed by the laws of science. 751 00:51:05,480 --> 00:51:08,460 The picture Jim Hartle and I developed 752 00:51:08,460 --> 00:51:11,980 of the spontaneous quantum creation of the universe 753 00:51:11,980 --> 00:51:15,130 would be a bit like the formation of bubbles of steam 754 00:51:15,130 --> 00:51:16,810 in boiling water. 755 00:51:26,620 --> 00:51:29,240 The idea is that the most probable histories 756 00:51:29,240 --> 00:51:33,470 of the universe would be like the surfaces of the bubbles. 757 00:51:38,320 --> 00:51:42,470 Many small bubbles would appear and then disappear again. 758 00:51:43,430 --> 00:51:47,410 These would correspond to mini universes that would expand, 759 00:51:47,410 --> 00:51:51,400 but would collapse again while still of microscopic size. 760 00:51:58,010 --> 00:52:01,020 They are possible alternative universes, 761 00:52:01,020 --> 00:52:03,080 but they are not of much interest 762 00:52:03,080 --> 00:52:05,260 since they do not last long enough 763 00:52:05,260 --> 00:52:09,740 to develop galaxies and stars, let alone intelligent life. 764 00:52:19,110 --> 00:52:21,910 A few of the little bubbles, however, 765 00:52:21,910 --> 00:52:23,770 with grow to a certain size 766 00:52:23,770 --> 00:52:26,370 at which they are safe from recollapse. 767 00:52:27,400 --> 00:52:31,390 They will continue to expand at an ever-increasing rate 768 00:52:31,390 --> 00:52:33,680 and will form the bubbles we see. 769 00:52:40,030 --> 00:52:41,920 They will correspond to universes 770 00:52:41,923 --> 00:52:45,913 that would start off expanding at an ever-increasing rate. 771 00:52:46,950 --> 00:52:48,980 This is called inflation, 772 00:52:48,980 --> 00:52:52,150 like the way prices go up every year. 773 00:52:53,849 --> 00:52:56,679 (audience laughs) 774 00:53:13,920 --> 00:53:16,110 The world record for inflation 775 00:53:16,110 --> 00:53:19,600 was in Germany after the first world war. 776 00:53:20,530 --> 00:53:23,490 Prices rose by a factor of 10 million 777 00:53:23,490 --> 00:53:25,760 in a period of 18 months, 778 00:53:26,840 --> 00:53:29,430 but that was nothing compared to inflation 779 00:53:29,430 --> 00:53:31,220 in the early universe. 780 00:53:32,090 --> 00:53:33,610 The universe expanded 781 00:53:33,610 --> 00:53:36,350 by a factor of million trillion trillion 782 00:53:36,350 --> 00:53:38,360 in a tiny fraction of a second. 783 00:53:49,771 --> 00:53:52,211 Unlike inflation in prices, 784 00:53:52,210 --> 00:53:55,960 inflation in the early universe was a very good thing. 785 00:53:56,970 --> 00:54:00,760 It produced a very large and uniform universe, 786 00:54:00,760 --> 00:54:02,450 just as we observe. 787 00:54:07,790 --> 00:54:11,120 However, it would not be completely uniform. 788 00:54:12,140 --> 00:54:14,380 In the sum over histories, 789 00:54:14,380 --> 00:54:17,260 histories that are very slightly irregular 790 00:54:17,260 --> 00:54:20,080 will have almost as high probabilities 791 00:54:20,080 --> 00:54:23,260 as the completely uniform and regular history. 792 00:54:33,970 --> 00:54:37,390 The theory therefore predicts that the early universe 793 00:54:37,390 --> 00:54:40,470 is likely to be slightly non-uniform. 794 00:54:41,490 --> 00:54:45,090 These irregularities would produce small variations 795 00:54:45,090 --> 00:54:47,860 in the intensity of the microwave background 796 00:54:47,860 --> 00:54:49,710 from different directions. 797 00:54:56,480 --> 00:54:59,140 The microwave background has been observed 798 00:54:59,140 --> 00:55:02,870 by the map satellite and was found to have exactly 799 00:55:02,870 --> 00:55:05,470 the kind of variations predicted. 800 00:55:06,490 --> 00:55:08,740 So we know we are on the right lines. 801 00:55:21,780 --> 00:55:24,730 The irregularities in the early universe 802 00:55:24,730 --> 00:55:26,430 will mean that some regions 803 00:55:26,430 --> 00:55:29,390 will have slightly higher density than others. 804 00:55:35,360 --> 00:55:39,020 The gravitational attraction of the extra density 805 00:55:39,020 --> 00:55:41,830 will slow the expansion of the region 806 00:55:41,830 --> 00:55:44,730 and can eventually cause the region to collapse 807 00:55:44,730 --> 00:55:47,060 to form galaxies and stars. 808 00:55:52,430 --> 00:55:55,340 So look well at the map of the microwave sky. 809 00:55:56,710 --> 00:56:00,520 It is the blueprint for all the structure in the universe. 810 00:56:09,250 --> 00:56:12,130 We are the product of quantum fluctuations 811 00:56:12,130 --> 00:56:14,300 in the very early universe. 812 00:56:15,150 --> 00:56:17,450 God really does play dice. 813 00:56:28,410 --> 00:56:31,320 We have made tremendous progress in cosmology 814 00:56:31,320 --> 00:56:33,340 in the last 100 years. 815 00:56:34,380 --> 00:56:36,920 The general theory of relativity 816 00:56:36,920 --> 00:56:40,370 and the discovery of the expansion of the universe 817 00:56:40,370 --> 00:56:43,410 shattered the old picture of an ever-existing 818 00:56:43,410 --> 00:56:44,870 and everlasting universe. 819 00:56:49,840 --> 00:56:54,030 Instead, general relativity predicted that the universe 820 00:56:54,027 --> 00:56:57,667 and time itself would begin in the Big Bang. 821 00:56:58,720 --> 00:56:59,960 It also predicted 822 00:56:59,960 --> 00:57:03,070 that time would come to an end in black holes. 823 00:57:18,340 --> 00:57:21,520 The discovery of the cosmic microwave background 824 00:57:21,520 --> 00:57:26,520 and observations of black holes support these conclusions. 825 00:57:27,560 --> 00:57:31,510 This is a profound change in our picture of the universe 826 00:57:31,510 --> 00:57:33,300 and of reality itself. 827 00:57:40,350 --> 00:57:43,360 Although the general theory of relativity 828 00:57:43,360 --> 00:57:45,810 predicted that the universe must have come 829 00:57:45,810 --> 00:57:49,060 from a period of high curvature in the past, 830 00:57:49,060 --> 00:57:51,350 it could not predict how the universe 831 00:57:51,350 --> 00:57:53,420 would emerge from the Big Bang. 832 00:57:54,480 --> 00:57:57,190 Thus, general relativity on its own 833 00:57:57,194 --> 00:58:00,784 cannot answer the central question in cosmology, 834 00:58:00,780 --> 00:58:03,600 why is the universe the way it is? 835 00:58:09,630 --> 00:58:12,130 However, if general relativity 836 00:58:12,130 --> 00:58:14,400 is combined with quantum theory, 837 00:58:14,400 --> 00:58:18,390 it may be possible to predict how the universe would start. 838 00:58:19,440 --> 00:58:22,960 It would initially expand at an ever-increasing rate. 839 00:58:28,510 --> 00:58:32,090 During this so-called inflationary period, 840 00:58:32,090 --> 00:58:34,270 the marriage of the two theories predicted 841 00:58:34,270 --> 00:58:37,360 that small fluctuations would develop 842 00:58:37,363 --> 00:58:41,043 and lead to the formation of galaxies, stars, 843 00:58:41,042 --> 00:58:44,712 and all the other structure in the universe. 844 00:58:51,305 --> 00:58:55,795 This is confirmed by observations of small non-uniformities 845 00:58:55,793 --> 00:58:58,473 in the cosmic microwave background 846 00:58:58,470 --> 00:59:01,540 with exactly the predicted properties. 847 00:59:02,570 --> 00:59:04,910 So it seems we are on our way 848 00:59:04,910 --> 00:59:07,970 to understanding the origin of the universe, 849 00:59:07,970 --> 00:59:10,380 though much more work will be needed. 850 00:59:14,920 --> 00:59:17,740 A new window on the very early universe 851 00:59:17,740 --> 00:59:21,420 will be opened when we can detect gravitational waves 852 00:59:21,420 --> 00:59:25,450 by accurately measuring the distances between spacecraft. 853 00:59:30,760 --> 00:59:33,890 Gravitational waves propagate freely to us 854 00:59:33,890 --> 00:59:38,890 from earliest times, unimpeded by any intervening material. 855 00:59:39,660 --> 00:59:42,930 By contrast, light is scattered many times 856 00:59:42,930 --> 00:59:44,580 by free electrons. 857 00:59:45,630 --> 00:59:49,730 The scattering goes on until the electrons freeze out 858 00:59:49,730 --> 00:59:53,410 when the universe is 300,000 years old. 859 01:00:01,290 --> 01:00:04,940 Despite having had some great successes, 860 01:00:04,940 --> 01:00:06,560 not everything is solved. 861 01:00:07,610 --> 01:00:11,340 We do not yet have a good theoretical understanding 862 01:00:11,340 --> 01:00:15,090 of the observations that the expansion of the universe 863 01:00:15,090 --> 01:00:19,950 is accelerating again after a long period of slowing down. 864 01:00:24,140 --> 01:00:26,710 Without such an understanding, 865 01:00:26,710 --> 01:00:30,210 we cannot be sure of the future of the universe. 866 01:00:31,190 --> 01:00:34,840 Will it continue to expand forever? 867 01:00:34,840 --> 01:00:38,160 Is inflation a law of nature, 868 01:00:38,160 --> 01:00:41,500 or will the universe eventually collapse again? 869 01:00:47,970 --> 01:00:52,500 New observational results and theoretical advances 870 01:00:52,500 --> 01:00:54,170 are coming in rapidly. 871 01:00:55,360 --> 01:00:59,060 Cosmology is a very exciting and active subject. 872 01:01:00,100 --> 01:01:04,020 We are getting close to answering the age-old questions. 873 01:01:06,640 --> 01:01:08,930 Why are we here? 874 01:01:08,930 --> 01:01:10,360 Where did we come from? 875 01:01:16,350 --> 01:01:18,450 Thank you for listening to me. 876 01:01:20,694 --> 01:01:23,694 (audience applauds) 877 01:01:40,785 --> 01:01:43,785 (audience applauds) 878 01:01:56,940 --> 01:02:01,220 - Professor Hawking has agreed to answer some questions, 879 01:02:01,220 --> 01:02:06,220 and so we gathered a few of the most popular questions 880 01:02:07,280 --> 01:02:09,400 and there were five. 881 01:02:09,400 --> 01:02:13,240 And my job is to read all five questions, 882 01:02:13,240 --> 01:02:16,130 and he will answer all five questions 883 01:02:16,130 --> 01:02:18,680 with one extended answer. 884 01:02:20,230 --> 01:02:24,890 Some of these questions bear on things he's already said, 885 01:02:24,890 --> 01:02:25,770 but you have to realize 886 01:02:25,770 --> 01:02:28,170 the questions were made in advance of his talk. 887 01:02:28,170 --> 01:02:33,170 Question one, do we know for certain how the universe began? 888 01:02:35,130 --> 01:02:37,660 Question two, the problem for most people 889 01:02:37,660 --> 01:02:39,520 in trying to grasp all this 890 01:02:39,520 --> 01:02:42,020 is if the Big Bang began at all, 891 01:02:43,610 --> 01:02:45,390 what was before the Big Bang? 892 01:02:47,080 --> 01:02:49,000 I'm afraid I'm gonna end up in hell. 893 01:02:48,998 --> 01:02:52,368 (audience laughs) 894 01:02:52,370 --> 01:02:57,370 Question three is how will the universe end and when? 895 01:02:59,650 --> 01:03:03,830 Question four, you say your goal is simple, 896 01:03:03,830 --> 01:03:06,630 a complete understanding of the universe, 897 01:03:06,627 --> 01:03:08,317 and the question goes on to say 898 01:03:08,320 --> 01:03:13,320 why is it as it is and why does it exist at all? 899 01:03:13,790 --> 01:03:17,520 How close are we and can science ever answer, 900 01:03:17,520 --> 01:03:19,350 and this is in big letters, 901 01:03:19,350 --> 01:03:22,570 why it exists in the first place? 902 01:03:23,680 --> 01:03:26,740 And question five is a very good one. 903 01:03:26,740 --> 01:03:30,360 What are the pressing big questions that are left? 904 01:03:31,560 --> 01:03:32,760 Professor Hawking. 905 01:03:36,634 --> 01:03:39,304 (machine beeps) 906 01:04:33,230 --> 01:04:35,670 - [Stephen] We are thoroughly sure the universe began 907 01:04:35,670 --> 01:04:38,670 with a period of accelerating expansion. 908 01:04:46,300 --> 01:04:48,390 This is called inflation 909 01:04:48,390 --> 01:04:51,150 because the size of the universe grows 910 01:04:51,150 --> 01:04:54,430 in the way prices go up in some countries. 911 01:05:01,440 --> 01:05:04,120 The inflation in the early universe 912 01:05:04,120 --> 01:05:07,440 is much more rapid than our financial inflation. 913 01:05:08,480 --> 01:05:10,020 The universe expanded 914 01:05:10,020 --> 01:05:13,000 by a factor of a million trillion trillion 915 01:05:13,000 --> 01:05:15,450 in a tiny fraction of a second. 916 01:05:20,180 --> 01:05:24,370 Inflation in the size of the universe is a good thing, 917 01:05:24,370 --> 01:05:27,020 unlike inflation in prices. 918 01:05:33,350 --> 01:05:37,010 It would produce a very large and very smooth universe 919 01:05:37,010 --> 01:05:39,800 with just the right amount of irregularity 920 01:05:39,800 --> 01:05:43,920 to account for the formation of galaxies, stars, 921 01:05:43,920 --> 01:05:46,460 and ultimately, human beings. 922 01:05:49,230 --> 01:05:51,460 How did this inflation start? 923 01:05:54,410 --> 01:05:58,280 How can one describe the universe at the beginning of time? 924 01:06:02,270 --> 01:06:05,170 I now think I can show how the universe 925 01:06:05,170 --> 01:06:08,180 was spontaneously created out of nothing 926 01:06:08,180 --> 01:06:10,620 according to the laws of science. 927 01:06:13,570 --> 01:06:17,430 The universe exists because general relativity 928 01:06:17,427 --> 01:06:20,517 and quantum theory allow and require it to exist. 929 01:06:23,500 --> 01:06:27,210 If I'm right, the universe is self-contained 930 01:06:27,210 --> 01:06:29,310 and governed by science alone. 931 01:06:32,120 --> 01:06:36,080 In time, we can hope to understand it completely. 932 01:06:38,660 --> 01:06:43,320 We have long enough as the universe should last forever. 933 01:06:43,324 --> 01:06:46,154 (audience laughs) 934 01:06:48,440 --> 01:06:51,000 Eternity is a very long time, 935 01:06:51,000 --> 01:06:54,540 especially towards the end, as Woody Allen said. 936 01:06:55,398 --> 01:06:58,228 (audience laughs) 937 01:07:00,498 --> 01:07:01,328 Thank you. 938 01:07:02,786 --> 01:07:05,786 (audience applauds)