1 00:00:00,060 --> 00:00:02,430 The following content is provided under a Creative 2 00:00:02,430 --> 00:00:03,820 Commons license. 3 00:00:03,820 --> 00:00:06,030 Your support will help MIT OpenCourseWare 4 00:00:06,030 --> 00:00:10,120 continue to offer high quality educational resources for free. 5 00:00:10,120 --> 00:00:12,660 To make a donation or to view additional materials 6 00:00:12,660 --> 00:00:16,620 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:16,620 --> 00:00:20,062 at ocw.mit.edu. 8 00:00:20,062 --> 00:00:23,930 NICHOLAS DIBELLA: So welcome to the big questions. 9 00:00:23,930 --> 00:00:26,345 My name is Nicholas. 10 00:00:30,780 --> 00:00:33,300 You can call me Nicholas if he want, or you 11 00:00:33,300 --> 00:00:42,830 can call me Nick, or sir, or whatever you feel like. 12 00:00:42,830 --> 00:00:45,560 I am I'm a physics major here. 13 00:00:45,560 --> 00:00:48,170 I'll be a senior next year. 14 00:00:48,170 --> 00:00:53,810 I like physics, philosophy, math, pizza. 15 00:00:53,810 --> 00:00:56,900 Pizza, did I mention pizza? 16 00:00:56,900 --> 00:00:58,630 I guess I'm addicted to pizza. 17 00:00:58,630 --> 00:01:01,270 And that's all you need to know about me. 18 00:01:01,270 --> 00:01:03,560 OK so this class, The Big Questions, we'll 19 00:01:03,560 --> 00:01:06,137 be looking at questions that are big, 20 00:01:06,137 --> 00:01:07,970 questions like what's the beginning of time. 21 00:01:07,970 --> 00:01:09,680 Will there be an end? 22 00:01:09,680 --> 00:01:12,000 Do aliens exist is time travel possible? 23 00:01:12,000 --> 00:01:13,750 Is the universe a computer simulation? 24 00:01:13,750 --> 00:01:15,890 Is he really heading outside the door 25 00:01:15,890 --> 00:01:18,380 to someplace far more interesting than here? 26 00:01:18,380 --> 00:01:20,690 Because that seems quite unimaginable and inconceivable 27 00:01:20,690 --> 00:01:22,610 to me. 28 00:01:22,610 --> 00:01:25,500 Questions like that, there's a whole bunch of them 29 00:01:25,500 --> 00:01:26,762 on the syllabus. 30 00:01:30,520 --> 00:01:33,610 Yeah so these are big questions. 31 00:01:33,610 --> 00:01:37,820 Due to the bigness of them, they're kind of hard questions. 32 00:01:37,820 --> 00:01:40,920 And people have been asking them for thousands of years, 33 00:01:40,920 --> 00:01:46,580 2000 maybe 5,000, some number of thousands of years. 34 00:01:46,580 --> 00:01:49,630 And they haven't really made a whole lot of progress, 35 00:01:49,630 --> 00:01:54,360 historically, even though they were very, very smart. 36 00:01:54,360 --> 00:01:57,027 And I aim in this class to make a lot of prog-- 37 00:01:57,027 --> 00:01:59,110 I aim to show you how we've made a lot of progress 38 00:01:59,110 --> 00:02:00,385 on these questions. 39 00:02:00,385 --> 00:02:01,760 I'm not going to claim that we're 40 00:02:01,760 --> 00:02:04,093 smarter than the people that already thought about them, 41 00:02:04,093 --> 00:02:06,290 but we're finally able to make a lot more progress 42 00:02:06,290 --> 00:02:08,449 on these questions because we know a lot more. 43 00:02:08,449 --> 00:02:10,610 We just know a whole lot more than people 44 00:02:10,610 --> 00:02:14,150 knew 1,000 years ago, or 100 years ago. 45 00:02:14,150 --> 00:02:16,820 In fact, probably the last 100 years 46 00:02:16,820 --> 00:02:19,610 have seen the greatest accumulation 47 00:02:19,610 --> 00:02:23,060 of new transformative human knowledge out of any 100 year 48 00:02:23,060 --> 00:02:24,300 period. 49 00:02:24,300 --> 00:02:26,170 So in the early 1900s-- 50 00:02:26,170 --> 00:02:28,040 like about 100 years ago, Einstein 51 00:02:28,040 --> 00:02:30,440 proposed his theory of relativity, special 52 00:02:30,440 --> 00:02:33,770 and general, which showed us that mass and energy curves 53 00:02:33,770 --> 00:02:35,930 space and time. 54 00:02:35,930 --> 00:02:37,240 I'll just let you be-- 55 00:02:37,240 --> 00:02:39,767 I'll just like you wonder about that mystery for now. 56 00:02:39,767 --> 00:02:41,600 And quantum mechanics showed us that there's 57 00:02:41,600 --> 00:02:45,380 an intrinsic randomness in nature, 58 00:02:45,380 --> 00:02:50,450 very, very non-obvious very, very profound and paradigm 59 00:02:50,450 --> 00:02:52,012 shifting. 60 00:02:52,012 --> 00:02:54,470 Don't worry about relativity and quantum mechanics for now. 61 00:02:54,470 --> 00:02:56,480 I'll get to those eventually. 62 00:02:56,480 --> 00:03:00,300 I just want to emphasize that really over the past 100 years, 63 00:03:00,300 --> 00:03:04,850 we've gained so much new more knowledge, more new knowledge, 64 00:03:04,850 --> 00:03:07,280 and we're finally able to make headway in these questions 65 00:03:07,280 --> 00:03:11,570 that people just had a hard time catching a grip of. 66 00:03:11,570 --> 00:03:15,380 We know a lot more, mostly because of physics, 67 00:03:15,380 --> 00:03:23,530 and also because of some new ideas and philosophy as well. 68 00:03:23,530 --> 00:03:26,030 So the types of questions in this class 69 00:03:26,030 --> 00:03:28,340 will be kind of physics-y. 70 00:03:28,340 --> 00:03:30,912 I mean I'll be talking about the universe. 71 00:03:30,912 --> 00:03:32,870 I mean you don't usually hear a chemist talking 72 00:03:32,870 --> 00:03:35,570 about the universe, or an economist talking 73 00:03:35,570 --> 00:03:38,212 about universe. 74 00:03:38,212 --> 00:03:40,670 I suppose they could, I mean I don't say that they can't, I 75 00:03:40,670 --> 00:03:42,170 mean they just don't. 76 00:03:42,170 --> 00:03:45,800 So the question sound physics-y. 77 00:03:45,800 --> 00:03:51,292 and maybe me a little metaphysics-y. 78 00:03:51,292 --> 00:03:53,500 So even though the course is called The Big Question, 79 00:03:53,500 --> 00:03:56,840 that won't really be looking at not physics-y big questions, 80 00:03:56,840 --> 00:03:59,000 like they're big questions and ethics, for example, 81 00:03:59,000 --> 00:04:00,620 or religion, or so forth. 82 00:04:00,620 --> 00:04:02,359 Like what should a person do. 83 00:04:02,359 --> 00:04:04,400 I won't really be looking at questions like that. 84 00:04:04,400 --> 00:04:09,610 I be looking at more physicsy type questions. 85 00:04:09,610 --> 00:04:15,170 Now the physicsy questions I want to analyze 86 00:04:15,170 --> 00:04:16,910 completely conceptually. 87 00:04:16,910 --> 00:04:20,269 So my plan for the class is to have 88 00:04:20,269 --> 00:04:24,410 a minimum of equations uttered, written, 89 00:04:24,410 --> 00:04:26,900 thought about, et cetera. 90 00:04:26,900 --> 00:04:30,050 So if you see me, you see I'm on the board going crazy writing 91 00:04:30,050 --> 00:04:31,640 down equations, please stop me. 92 00:04:31,640 --> 00:04:35,090 I mean I might just forget what I'm doing, 93 00:04:35,090 --> 00:04:37,550 and accidentally just become a mathematical menace 94 00:04:37,550 --> 00:04:38,220 or something. 95 00:04:38,220 --> 00:04:40,789 So stop me if that happens. 96 00:04:40,789 --> 00:04:43,080 You should also feel free to ask questions at any time, 97 00:04:43,080 --> 00:04:48,890 or stop me if I'm mumbling, or if I'm being unclear, 98 00:04:48,890 --> 00:04:50,750 if I fall asleep, or something like that. 99 00:04:50,750 --> 00:04:55,230 You should feel free to stop me and ask questions. 100 00:04:55,230 --> 00:04:56,910 Oh yeah. 101 00:04:56,910 --> 00:04:58,640 So all of these questions are also 102 00:04:58,640 --> 00:05:01,130 kind of philosophical sounding. 103 00:05:01,130 --> 00:05:04,010 I mean where is the nature of reality, 104 00:05:04,010 --> 00:05:05,660 kind of philosophical sounding. 105 00:05:05,660 --> 00:05:07,810 You have a question? 106 00:05:07,810 --> 00:05:11,390 Oh, you're just doing the old lean 107 00:05:11,390 --> 00:05:14,860 on the hand when it looks like you're asking a question trick. 108 00:05:14,860 --> 00:05:16,530 No, he doesn't have a question. 109 00:05:16,530 --> 00:05:19,326 So a lot of the question a philosophical sounding 110 00:05:19,326 --> 00:05:21,200 but there are a lot of questions historically 111 00:05:21,200 --> 00:05:23,480 that have started out as philosophical sounding 112 00:05:23,480 --> 00:05:26,250 questions and have eventually become physics questions. 113 00:05:26,250 --> 00:05:28,300 Questions like what's the beginning of time. 114 00:05:28,300 --> 00:05:31,880 And if you ask this question 100 years ago or 110 years ago 115 00:05:31,880 --> 00:05:34,460 or something, no one would have-- 116 00:05:34,460 --> 00:05:37,820 people have ridiculed you if you said it was a science question. 117 00:05:37,820 --> 00:05:39,770 But when the Big Bang Theory was eventually, 118 00:05:39,770 --> 00:05:42,560 it was eventually thought of, it became a very legitimate 119 00:05:42,560 --> 00:05:43,530 question. 120 00:05:43,530 --> 00:05:45,530 And particular according to the Big Bang Theory, 121 00:05:45,530 --> 00:05:47,060 yes there was the beginning of time 122 00:05:47,060 --> 00:05:49,970 and we call that beginning of time the big bang. 123 00:05:49,970 --> 00:05:53,130 And it has a very physical basis to it. 124 00:05:53,130 --> 00:05:54,800 But there are still some questions, 125 00:05:54,800 --> 00:05:59,212 I mean there are so many questions that are big and are 126 00:05:59,212 --> 00:06:00,170 philosophical sounding. 127 00:06:00,170 --> 00:06:01,795 And they're still philosophy right now, 128 00:06:01,795 --> 00:06:04,090 but maybe eventually there'll be physicsy. 129 00:06:04,090 --> 00:06:06,840 We'll see. 130 00:06:06,840 --> 00:06:11,337 OK, so my plan for the class is to talk, 131 00:06:11,337 --> 00:06:13,670 to analyze these questions from a physics point of view, 132 00:06:13,670 --> 00:06:16,494 or from a philosophical point of view. 133 00:06:16,494 --> 00:06:18,410 In particular, I don't want to invoke religion 134 00:06:18,410 --> 00:06:21,440 at all, so there should be a minimum of-- 135 00:06:21,440 --> 00:06:26,442 I mean there should be no religious talk. 136 00:06:26,442 --> 00:06:28,900 I mean you feel free to talk, ask me questions after class, 137 00:06:28,900 --> 00:06:30,930 or send me an email or something. 138 00:06:30,930 --> 00:06:34,490 But the goal for the course is to look at these questions 139 00:06:34,490 --> 00:06:39,080 from a science or philosophical point of view. 140 00:06:39,080 --> 00:06:42,880 OK, so the way the class will work 141 00:06:42,880 --> 00:06:47,450 will all convene here in this cozy room. 142 00:06:47,450 --> 00:06:53,540 Sundays 1:35 to 2:55 PM, except for today, which is 143 00:06:53,540 --> 00:06:57,170 2:05 to 2:55 PM, actually 2:10. 144 00:06:57,170 --> 00:06:59,150 I guess we started-- 145 00:06:59,150 --> 00:07:01,460 And so I'll just I'll just talk. 146 00:07:01,460 --> 00:07:03,650 I'll just talk to you guys. 147 00:07:03,650 --> 00:07:05,420 There won't be any homework. 148 00:07:05,420 --> 00:07:06,950 There won't be any tests. 149 00:07:06,950 --> 00:07:11,360 You'd be crazy to want that over the summer, my opinion. 150 00:07:11,360 --> 00:07:13,880 But I will post notes on the website, 151 00:07:13,880 --> 00:07:16,250 if I can figure how to use the website. 152 00:07:16,250 --> 00:07:19,230 And I will post some things for you to think about if you want. 153 00:07:19,230 --> 00:07:23,000 But I mean you can just treat this whole class 154 00:07:23,000 --> 00:07:26,360 as a series of entertainment like yours if you want. 155 00:07:26,360 --> 00:07:27,680 I just want to entertain you. 156 00:07:27,680 --> 00:07:29,680 I just want to show you that these questions are 157 00:07:29,680 --> 00:07:31,340 really interesting and they make you 158 00:07:31,340 --> 00:07:34,140 feel good to think about them. 159 00:07:34,140 --> 00:07:37,040 That's all I want to do. 160 00:07:37,040 --> 00:07:39,862 I mean you can take the whole course much further if you 161 00:07:39,862 --> 00:07:41,570 want, but I mean you don't have to I mean 162 00:07:41,570 --> 00:07:42,819 I'm not going give any grades. 163 00:07:45,920 --> 00:07:47,000 Is that it? 164 00:07:47,000 --> 00:07:50,000 OK, I think that's it in terms of course organization and all 165 00:07:50,000 --> 00:07:50,612 that. 166 00:07:50,612 --> 00:07:51,820 Does anybody have a question? 167 00:07:54,700 --> 00:07:55,610 Cool. 168 00:07:55,610 --> 00:07:57,026 I'm going to just close this door. 169 00:08:04,104 --> 00:08:05,020 Almost close the door. 170 00:08:08,400 --> 00:08:11,590 OK, so where do we start? 171 00:08:11,590 --> 00:08:13,720 Big questions. 172 00:08:13,720 --> 00:08:16,390 I have a lot of big questions on that sheet. 173 00:08:16,390 --> 00:08:18,430 So do we start the biggest question? 174 00:08:18,430 --> 00:08:21,352 Maybe we start with a big question, but not the biggest, 175 00:08:21,352 --> 00:08:22,810 and then progressively move farther 176 00:08:22,810 --> 00:08:25,220 to bigger and bigger questions. 177 00:08:25,220 --> 00:08:27,010 I don't know the best way to start is. 178 00:08:27,010 --> 00:08:30,850 So I figure let's just start at the beginning, 179 00:08:30,850 --> 00:08:33,100 and by beginning, I mean beginning of time, 180 00:08:33,100 --> 00:08:35,049 if there was a beginning of time. 181 00:08:35,049 --> 00:08:36,970 OK, sound good? 182 00:08:36,970 --> 00:08:38,495 So we'll start at the beginning. 183 00:08:44,210 --> 00:08:48,280 So the modern approach to understanding the beginning 184 00:08:48,280 --> 00:08:51,040 of time, if there was the beginning of time, 185 00:08:51,040 --> 00:08:53,590 to understanding the origin of the universe 186 00:08:53,590 --> 00:08:55,570 from a science point of view, really 187 00:08:55,570 --> 00:08:58,060 started in the 20th century. 188 00:08:58,060 --> 00:09:06,030 And our first experimental or observational evidence 189 00:09:06,030 --> 00:09:10,450 that allowed us to say things about the early universe, 190 00:09:10,450 --> 00:09:13,210 about the history of the universe, came in the 1930s 191 00:09:13,210 --> 00:09:15,370 with Edwin Hubble. 192 00:09:15,370 --> 00:09:16,870 So write down Hubble. 193 00:09:25,660 --> 00:09:30,970 And he looked at the sky when it was dark. 194 00:09:30,970 --> 00:09:35,750 And he was able to conclude that, in fact, 195 00:09:35,750 --> 00:09:38,740 if you look at the galaxies, most of them 196 00:09:38,740 --> 00:09:41,420 are moving away from us. 197 00:09:41,420 --> 00:09:44,742 That that's why he was able to conclude. 198 00:09:44,742 --> 00:09:46,450 I won't tell you exactly how he did that. 199 00:09:46,450 --> 00:09:49,400 He used something called redshift. 200 00:09:49,400 --> 00:09:53,550 But you do just trust me for now that he observed the night sky 201 00:09:53,550 --> 00:09:55,960 and he was able to conclude that most of the galaxies 202 00:09:55,960 --> 00:09:56,782 are moving away. 203 00:09:56,782 --> 00:09:57,990 So I'll just write that down. 204 00:09:57,990 --> 00:09:58,540 So most-- 205 00:10:09,570 --> 00:10:12,040 So if you're Hubble, you see this. 206 00:10:12,040 --> 00:10:14,120 Most of the galaxies are moving away. 207 00:10:14,120 --> 00:10:16,760 If you have the slightest bit of curiosity. 208 00:10:16,760 --> 00:10:20,860 You might wonder why. 209 00:10:20,860 --> 00:10:23,000 Why are the galaxies moving away? 210 00:10:23,000 --> 00:10:24,950 Why isn't it that half and moving away, 211 00:10:24,950 --> 00:10:29,832 half way towards us, or why we are moving toward, 212 00:10:29,832 --> 00:10:31,290 why are they all moving towards us. 213 00:10:31,290 --> 00:10:33,860 I mean after all attracts. 214 00:10:33,860 --> 00:10:36,570 Why isn't that the case? 215 00:10:36,570 --> 00:10:39,950 So he concluded that most of the galaxies 216 00:10:39,950 --> 00:10:43,040 are moving away from us. 217 00:10:43,040 --> 00:10:47,880 And so you'd wonder why is that true. 218 00:10:47,880 --> 00:10:50,941 Does anybody have an answer what they might think it's due to? 219 00:10:50,941 --> 00:10:51,440 Sure. 220 00:10:51,440 --> 00:10:54,344 AUDIENCE: [INAUDIBLE] scared of us? 221 00:10:54,344 --> 00:10:56,510 NICHOLAS DIBELLA: So it's possible the galaxies-- is 222 00:10:56,510 --> 00:10:58,634 it possible that galaxies are in fact scared of us? 223 00:11:01,430 --> 00:11:04,010 I guess that's, maybe back then that might 224 00:11:04,010 --> 00:11:06,517 have been a legitimate scientific hypothesis. 225 00:11:06,517 --> 00:11:08,100 But we don't really know a whole lot-- 226 00:11:08,100 --> 00:11:10,926 we didn't know a whole lot about the nature of consciousness. 227 00:11:10,926 --> 00:11:12,800 Well, even-- I mean we don't know a whole lot 228 00:11:12,800 --> 00:11:13,535 about the nature of consciousness, 229 00:11:13,535 --> 00:11:15,310 if galaxies have a conscious. 230 00:11:15,310 --> 00:11:21,800 And most people who think about this sort of thing 231 00:11:21,800 --> 00:11:24,770 would think that that's a funny answer, but probably not 232 00:11:24,770 --> 00:11:25,830 the right one. 233 00:11:25,830 --> 00:11:26,826 Yes? 234 00:11:26,826 --> 00:11:29,610 AUDIENCE: Maybe like why do galaxy in this place, 235 00:11:29,610 --> 00:11:32,230 they don't have like enough gravity? 236 00:11:32,230 --> 00:11:33,230 NICHOLAS DIBELLA: Maybe. 237 00:11:33,230 --> 00:11:35,429 Maybe the galaxies don't have enough gravity 238 00:11:35,429 --> 00:11:36,720 so they're moving away from us. 239 00:11:36,720 --> 00:11:40,160 We don't have enough gravity to pull them all towards us. 240 00:11:40,160 --> 00:11:42,282 Maybe? 241 00:11:42,282 --> 00:11:45,650 Yeah, that's possible. 242 00:11:45,650 --> 00:11:50,090 In fact, you're on the right direction. 243 00:11:50,090 --> 00:11:52,802 But you might still wonder why don't they have enough gravity. 244 00:11:52,802 --> 00:11:54,260 Why don't they have enough gravity? 245 00:11:54,260 --> 00:11:57,157 We still need an answer to that question. 246 00:11:57,157 --> 00:11:57,740 Another guess? 247 00:11:57,740 --> 00:12:00,650 AUDIENCE: There's something else that started [INAUDIBLE] 248 00:12:00,650 --> 00:12:01,900 NICHOLAS DIBELLA: What's that? 249 00:12:01,900 --> 00:12:04,294 AUDIENCE: Something else that's driving [INAUDIBLE] 250 00:12:04,294 --> 00:12:06,585 NICHOLAS DIBELLA: Something else, sorry, that started-- 251 00:12:06,585 --> 00:12:08,044 AUDIENCE: That has started gravity. 252 00:12:08,044 --> 00:12:10,459 NICHOLAS DIBELLA: Something else that has started gravity. 253 00:12:10,459 --> 00:12:13,070 Like so maybe there's something far away from us 254 00:12:13,070 --> 00:12:15,480 that in fact, pulling-- 255 00:12:15,480 --> 00:12:18,290 I mean where we're sitting-- 256 00:12:18,290 --> 00:12:20,100 we're living right here. 257 00:12:20,100 --> 00:12:22,130 And we see that this is us. 258 00:12:22,130 --> 00:12:24,240 And we see all-- 259 00:12:24,240 --> 00:12:26,520 you see a whole bunch of galaxies. 260 00:12:26,520 --> 00:12:27,530 They're all moving away. 261 00:12:31,010 --> 00:12:33,080 And you're suggesting maybe something 262 00:12:33,080 --> 00:12:35,570 out there that's pulling them towards it, 263 00:12:35,570 --> 00:12:38,210 like some really big thing. 264 00:12:38,210 --> 00:12:39,450 Who knows what it is? 265 00:12:39,450 --> 00:12:40,250 Right. 266 00:12:40,250 --> 00:12:43,460 Is that your suggestion? 267 00:12:43,460 --> 00:12:44,950 I suppose it's possible. 268 00:12:44,950 --> 00:12:47,420 Well-- so the fact-- 269 00:12:47,420 --> 00:12:50,240 So Hubble actually observed everything, regardless 270 00:12:50,240 --> 00:12:53,330 of the direction, every galaxy, well almost every galaxy, 271 00:12:53,330 --> 00:12:56,210 regardless of the direction you looked is moving away from us. 272 00:12:56,210 --> 00:13:00,710 So if this is us, and these guys are moving in that direction, 273 00:13:00,710 --> 00:13:02,660 then it's a legitimate hypothesis 274 00:13:02,660 --> 00:13:04,035 to think that maybe they're being 275 00:13:04,035 --> 00:13:05,799 attracted to this huge mass. 276 00:13:05,799 --> 00:13:07,340 But what about what about these guys? 277 00:13:11,190 --> 00:13:14,392 I guess it's possible that maybe all the galaxies 278 00:13:14,392 --> 00:13:16,850 the Hubble observed, all the galaxies that Hubble observed, 279 00:13:16,850 --> 00:13:20,150 he's sitting, Hubble is sitting. 280 00:13:20,150 --> 00:13:23,110 He's sitting in his room, or whatever, 281 00:13:23,110 --> 00:13:27,020 and there's some kind of a big shell, a really massive shell, 282 00:13:27,020 --> 00:13:29,245 surrounding all the galaxies that he observed. 283 00:13:29,245 --> 00:13:30,620 And maybe we're the center of it. 284 00:13:30,620 --> 00:13:31,980 We're just somewhere inside the shell. 285 00:13:31,980 --> 00:13:33,688 And this shell is really massive and it's 286 00:13:33,688 --> 00:13:35,300 pulling everything towards it. 287 00:13:35,300 --> 00:13:36,830 Is that your suggestion basically? 288 00:13:36,830 --> 00:13:37,662 AUDIENCE: Yeah. 289 00:13:37,662 --> 00:13:38,690 NICHOLAS DIBELLA: OK. 290 00:13:38,690 --> 00:13:42,710 That's another-- that's a valid hypothesis. 291 00:13:42,710 --> 00:13:43,210 Yes? 292 00:13:43,210 --> 00:13:44,710 AUDIENCE: The universe Is expanding. 293 00:13:44,710 --> 00:13:47,280 NICHOLAS DIBELLA: The universe is expanding. 294 00:13:47,280 --> 00:13:50,231 Why would that imply that the galaxies are-- which galaxies 295 00:13:50,231 --> 00:13:51,230 are moving away from us? 296 00:13:51,230 --> 00:13:53,530 AUDIENCE: The space between them is running out. 297 00:13:53,530 --> 00:13:58,130 NICHOLAS DIBELLA: The space between them is running out. 298 00:13:58,130 --> 00:13:59,510 That's actually the right answer. 299 00:13:59,510 --> 00:14:02,120 That's actually the right answer. 300 00:14:02,120 --> 00:14:03,620 And I'll talk a little more about it 301 00:14:03,620 --> 00:14:04,760 in just a couple minutes. 302 00:14:04,760 --> 00:14:06,660 I'm just curious, I'm just curious of other, 303 00:14:06,660 --> 00:14:08,990 I'm just curious of other guesses 304 00:14:08,990 --> 00:14:10,460 that you guys might have. 305 00:14:10,460 --> 00:14:12,590 I mean, I already said that's the right answer, 306 00:14:12,590 --> 00:14:15,230 but what might be another conceivable answer? 307 00:14:15,230 --> 00:14:16,741 Any other conceivable answers? 308 00:14:16,741 --> 00:14:17,240 Yes? 309 00:14:17,240 --> 00:14:19,826 AUDIENCE: Maybe because it's just moving away. 310 00:14:19,826 --> 00:14:22,520 NICHOLAS DIBELLA: Maybe because it's just moving away. 311 00:14:22,520 --> 00:14:25,940 Well me I'm asking why is it moving away. 312 00:14:25,940 --> 00:14:28,400 Or do you accept that as a fundamental postulate 313 00:14:28,400 --> 00:14:30,170 of reality? 314 00:14:30,170 --> 00:14:33,297 Galaxies have the property that they move away from us, 315 00:14:33,297 --> 00:14:34,380 people that live on Earth. 316 00:14:34,380 --> 00:14:35,040 Is that what you're suggesting? 317 00:14:35,040 --> 00:14:35,688 AUDIENCE: No. 318 00:14:35,688 --> 00:14:36,684 NICHOLAS DIBELLA: Oh. 319 00:14:36,684 --> 00:14:46,146 AUDIENCE: [INAUDIBLE] 320 00:14:46,146 --> 00:14:48,610 NICHOLAS DIBELLA: So maybe they're 321 00:14:48,610 --> 00:14:53,537 just all for some reason they're just all moving and that-- 322 00:14:53,537 --> 00:14:54,370 they're just moving. 323 00:14:54,370 --> 00:14:56,920 Well, I mean they're not all moving in the same direction. 324 00:14:56,920 --> 00:15:01,372 AUDIENCE: They're just moving in whatever direction [INAUDIBLE] 325 00:15:01,372 --> 00:15:02,830 NICHOLAS DIBELLA: Oh and so, I mean 326 00:15:02,830 --> 00:15:04,954 they're like basically moving in random directions, 327 00:15:04,954 --> 00:15:08,270 but it just turns out that most of them moving away from us. 328 00:15:08,270 --> 00:15:10,020 Well I mean I can ask why and most of them 329 00:15:10,020 --> 00:15:11,020 moving away from us. 330 00:15:13,600 --> 00:15:15,640 I'll take one more guess. 331 00:15:15,640 --> 00:15:16,310 It's fun. 332 00:15:16,310 --> 00:15:17,230 I mean I said that's the right answer, 333 00:15:17,230 --> 00:15:19,990 but it's fun to think about what alternative hypotheses might 334 00:15:19,990 --> 00:15:23,140 be because people back then, they got the data, 335 00:15:23,140 --> 00:15:25,580 and they had to try to understand it somehow. 336 00:15:25,580 --> 00:15:29,710 They actually had a little help because earlier people 337 00:15:29,710 --> 00:15:32,770 made suggestions about whether the universe would be expanding 338 00:15:32,770 --> 00:15:33,400 or not. 339 00:15:33,400 --> 00:15:34,410 And so they had a little help. 340 00:15:34,410 --> 00:15:35,909 But for someone who's just starting, 341 00:15:35,909 --> 00:15:37,030 he's just observing them. 342 00:15:37,030 --> 00:15:39,340 It's really-- I think it's important, as a scientist, 343 00:15:39,340 --> 00:15:42,250 to wonder what does the data tell us. 344 00:15:42,250 --> 00:15:42,985 Yes? 345 00:15:42,985 --> 00:15:45,520 AUDIENCE: Well, it's sort of far fetched, 346 00:15:45,520 --> 00:15:50,200 but have you heard about diffusion where in the liquid 347 00:15:50,200 --> 00:15:54,420 [INAUDIBLE] would spread throughout it evenly? 348 00:15:54,420 --> 00:15:57,150 NICHOLAS DIBELLA: Sure, yes. 349 00:15:57,150 --> 00:16:03,070 OK, so the fusion is just when the molecules 350 00:16:03,070 --> 00:16:08,070 pass through small-- 351 00:16:08,070 --> 00:16:09,460 Do you know what diffusion is? 352 00:16:09,460 --> 00:16:12,060 I mean things diffuse. 353 00:16:12,060 --> 00:16:13,810 I don't want to waste too much time on it. 354 00:16:13,810 --> 00:16:16,290 OK so, what about diffusion? 355 00:16:16,290 --> 00:16:19,330 AUDIENCE: Maybe this is gonna sound far fetched, 356 00:16:19,330 --> 00:16:21,465 but maybe that's why. 357 00:16:21,465 --> 00:16:23,590 NICHOLAS DIBELLA: Maybe the galaxies are diffusing. 358 00:16:27,950 --> 00:16:30,850 Is there some kind of fluid presence? 359 00:16:30,850 --> 00:16:33,460 Maybe space is a fluid? 360 00:16:33,460 --> 00:16:35,440 Actually that's not as far out as it sounds, 361 00:16:35,440 --> 00:16:37,750 because it actually turns out to be 362 00:16:37,750 --> 00:16:40,690 useful to think of space as a fluid in some context. 363 00:16:40,690 --> 00:16:43,787 I read about it once. 364 00:16:43,787 --> 00:16:44,620 I'll stop with that. 365 00:16:44,620 --> 00:16:46,820 I mean you said the right answer. 366 00:16:46,820 --> 00:16:48,070 I just want to give one more-- 367 00:16:48,070 --> 00:16:51,560 I want to give one more possible-- 368 00:16:51,560 --> 00:16:56,440 I want to have one more possible explanation. 369 00:16:56,440 --> 00:16:59,170 So I'll give-- so there'll be two hypotheses. 370 00:17:02,620 --> 00:17:05,740 So we've got we've got the observation. 371 00:17:05,740 --> 00:17:11,510 Most galaxies move away. 372 00:17:15,359 --> 00:17:16,260 And I'm asking why. 373 00:17:20,160 --> 00:17:26,290 One explanation is that, well it's not really an explanation. 374 00:17:26,290 --> 00:17:29,160 So if most of them as most of them are moving away now, 375 00:17:29,160 --> 00:17:33,320 then that means that in the past they were closer to us, right. 376 00:17:33,320 --> 00:17:35,490 They're closer to us yesterday than they were today. 377 00:17:35,490 --> 00:17:36,630 And they were closer to us two days ago 378 00:17:36,630 --> 00:17:37,990 than they were yesterday. 379 00:17:37,990 --> 00:17:39,420 And so on and so forth. 380 00:17:39,420 --> 00:17:42,820 And so if you extrapolate very far back. 381 00:17:42,820 --> 00:17:48,270 If you very far back, rewind time to very far back in time, 382 00:17:48,270 --> 00:17:50,875 then everything will be very, very close to each other. 383 00:17:50,875 --> 00:17:53,250 And in fact, maybe everything is concentrated at a point. 384 00:17:55,980 --> 00:17:58,470 So this is the situation now. 385 00:17:58,470 --> 00:18:06,750 There's us, there's us here and there are galaxies moving away. 386 00:18:11,920 --> 00:18:12,470 That's now. 387 00:18:17,090 --> 00:18:20,580 What about-- a long time ago. 388 00:18:20,580 --> 00:18:24,030 So a long time ago, everything would be very concentrated. 389 00:18:24,030 --> 00:18:27,750 Everything is at a single point. 390 00:18:27,750 --> 00:18:31,090 And if you look at things from this perspective, 391 00:18:31,090 --> 00:18:32,130 say a long time ago. 392 00:18:37,797 --> 00:18:39,630 If you look at things from this perspective, 393 00:18:39,630 --> 00:18:43,020 it would seem that perhaps some kind of explosion 394 00:18:43,020 --> 00:18:45,750 occurred that's centered at us. 395 00:18:45,750 --> 00:18:49,560 And this explosion just caused everything, 396 00:18:49,560 --> 00:18:54,600 all the galaxies to explode away symmetrically 397 00:18:54,600 --> 00:18:56,610 in all directions. 398 00:18:56,610 --> 00:18:59,940 And we won't ask what the explosion actually was, 399 00:18:59,940 --> 00:19:03,990 but it's conceivable that there was some kind of a bang, 400 00:19:03,990 --> 00:19:08,190 one might call it a big bang that was centered right at us. 401 00:19:08,190 --> 00:19:10,060 And so the Big Bang happened. 402 00:19:10,060 --> 00:19:13,500 So here space and everything. 403 00:19:13,500 --> 00:19:14,910 There's nothing there. 404 00:19:14,910 --> 00:19:16,790 Everything is there. 405 00:19:16,790 --> 00:19:18,360 Near where we are right now. 406 00:19:18,360 --> 00:19:21,210 And some kind of explosion occurred, everything went out. 407 00:19:21,210 --> 00:19:23,280 That's another legitimate hypothesis. 408 00:19:26,090 --> 00:19:29,250 It would explain why are these moving away. 409 00:19:29,250 --> 00:19:32,250 But you might have a problem with it in the sense 410 00:19:32,250 --> 00:19:37,680 that it's kind of arrogant in the sense that why 411 00:19:37,680 --> 00:19:39,640 should we be special. 412 00:19:39,640 --> 00:19:41,850 Why is everything moving away from us? 413 00:19:41,850 --> 00:19:48,180 Why not the Andromeda Galaxy or something? 414 00:19:48,180 --> 00:19:51,290 Why should we be special? 415 00:19:51,290 --> 00:19:54,390 But nonetheless, it's a legitimate hypothesis 416 00:19:54,390 --> 00:19:56,880 and it would explain why everything's moving away.