1 00:00:00,040 --> 00:00:02,460 The following content is provided under a Creative 2 00:00:02,460 --> 00:00:03,980 Commons license. 3 00:00:03,980 --> 00:00:06,910 Your support will help MIT OpenCourseWare continue to 4 00:00:06,910 --> 00:00:10,660 offer high-quality educational resources for free. 5 00:00:10,660 --> 00:00:13,460 To make a donation or view additional materials from 6 00:00:13,460 --> 00:00:17,390 hundreds of MIT courses, visit MIT OpenCourseWare at 7 00:00:17,390 --> 00:00:18,640 ocw.mit.edu. 8 00:00:22,250 --> 00:00:22,620 PROFESSOR: OK. 9 00:00:22,620 --> 00:00:27,080 Welcome back, everyone, and me too. 10 00:00:27,080 --> 00:00:32,399 I just came back from Boulder where I gave eight talks. 11 00:00:32,399 --> 00:00:36,180 I was on seven panels and gave one separate 12 00:00:36,180 --> 00:00:39,230 talk, most on education. 13 00:00:39,230 --> 00:00:42,740 And one of the talks was on teaching how to 14 00:00:42,740 --> 00:00:44,100 think or what to think. 15 00:00:44,100 --> 00:00:47,900 So there were three panelists, one professor from Berkeley in 16 00:00:47,900 --> 00:00:51,640 the astronomy department, who is also a renowned teacher, 17 00:00:51,640 --> 00:00:54,540 and then an investigative journalist, and then I spoke. 18 00:00:54,540 --> 00:00:57,590 And we all said something for about 10 minutes. 19 00:00:57,590 --> 00:01:00,710 I talked about the history of education and why it's 20 00:01:00,710 --> 00:01:03,310 difficult to change educational institutions and 21 00:01:03,310 --> 00:01:07,630 educational practices and what the original purposes of the 22 00:01:07,630 --> 00:01:11,480 schools were, so some of this material that I'll talk about 23 00:01:11,480 --> 00:01:14,110 in the second to last lecture on political barriers to 24 00:01:14,110 --> 00:01:17,120 educational change. 25 00:01:17,120 --> 00:01:24,600 And I then also, before this whole session, I described to 26 00:01:24,600 --> 00:01:27,940 the reporter for the Daily Camera, which is the paper in 27 00:01:27,940 --> 00:01:31,190 Boulder, a bit about what I was going to say. 28 00:01:31,190 --> 00:01:33,790 And I talked about some of the material I've told you already 29 00:01:33,790 --> 00:01:35,580 about multiplication table. 30 00:01:35,580 --> 00:01:39,050 So if you remember, the multiplication table, when 31 00:01:39,050 --> 00:01:43,710 people get brain damage in the arithmetic area, they can't do 32 00:01:43,710 --> 00:01:45,430 addition anymore, but they can still do the 33 00:01:45,430 --> 00:01:47,810 multiplication table. 34 00:01:47,810 --> 00:01:51,210 And when people get brain damage in the language area, 35 00:01:51,210 --> 00:01:54,090 they can still do addition, but they can't do 36 00:01:54,090 --> 00:01:55,480 multiplication anymore. 37 00:01:55,480 --> 00:01:57,660 And that's because multiplication, generally, is 38 00:01:57,660 --> 00:01:58,910 learned as-- 39 00:02:06,940 --> 00:02:09,550 So when you see it, you think of symbols and math, but 40 00:02:09,550 --> 00:02:12,640 actually the way most people learn it is 6 times 9 is 54. 41 00:02:12,640 --> 00:02:19,270 Then you have to memorize yet another fact. 42 00:02:19,270 --> 00:02:20,670 9 times 6 is 54. 43 00:02:20,670 --> 00:02:21,740 Oh. 44 00:02:21,740 --> 00:02:24,810 And then you have to learn yet a new fact, that these two 45 00:02:24,810 --> 00:02:27,390 facts are related, when, actually, if you understood 46 00:02:27,390 --> 00:02:29,860 the meaning, there would be just one fact. 47 00:02:29,860 --> 00:02:31,020 So now you have to memorize all 48 00:02:31,020 --> 00:02:32,160 these linguistic sentences. 49 00:02:32,160 --> 00:02:35,220 And no surprise, when you get damage in the linguistic area, 50 00:02:35,220 --> 00:02:37,580 that kind of multiplication table goes away. 51 00:02:37,580 --> 00:02:39,510 So I said to the reporter, yeah, what we really need to 52 00:02:39,510 --> 00:02:44,720 do is teach multiplication and math in a whole different way. 53 00:02:44,720 --> 00:02:47,560 So the reporter, she understood everything and 54 00:02:47,560 --> 00:02:48,670 said, oh, that's really interesting. 55 00:02:48,670 --> 00:02:50,110 I'm actually studying education 56 00:02:50,110 --> 00:02:52,580 myself, and I have children. 57 00:02:52,580 --> 00:02:55,670 And I'll try to apply that with my children and in the 58 00:02:55,670 --> 00:02:56,760 teaching that I do. 59 00:02:56,760 --> 00:02:58,570 I said, oh, great. 60 00:02:58,570 --> 00:03:02,150 So then, I gave my talk, and then the moderator asked 61 00:03:02,150 --> 00:03:04,570 everybody, well, does anyone on the panel want to say 62 00:03:04,570 --> 00:03:06,280 anything to anybody else? 63 00:03:06,280 --> 00:03:09,460 And so Alex Filippenko from Berkeley, he stood up and he 64 00:03:09,460 --> 00:03:13,340 said, well, I agreed with everything that Sanjoy said, 65 00:03:13,340 --> 00:03:16,330 except he was quoted in the paper this morning as saying 66 00:03:16,330 --> 00:03:19,930 we shouldn't teach the multiplication table. 67 00:03:19,930 --> 00:03:23,640 So that whole discussion, which seemed to be completely 68 00:03:23,640 --> 00:03:29,140 understood, just got condensed into one sentence. 69 00:03:29,140 --> 00:03:32,200 So now I didn't actually have to say very much in response, 70 00:03:32,200 --> 00:03:34,320 because the second panelist, as I mentioned, was an 71 00:03:34,320 --> 00:03:35,690 investigative journalist. 72 00:03:35,690 --> 00:03:37,900 And what she was talking about is how you have to be very 73 00:03:37,900 --> 00:03:39,320 skeptical of what's in the media. 74 00:03:39,320 --> 00:03:42,140 So all I had to do was look at her for a bit, and then 75 00:03:42,140 --> 00:03:44,910 everybody started laughing because the point was clear. 76 00:03:44,910 --> 00:03:46,920 But then I explained to everybody else what I'd 77 00:03:46,920 --> 00:03:50,650 explain to the reporter. 78 00:03:50,650 --> 00:03:54,560 That's by way of saying that education is a complicated 79 00:03:54,560 --> 00:03:58,830 subject, but the audience understands a lot more than 80 00:03:58,830 --> 00:04:01,820 the media does, which is one of the barriers to political 81 00:04:01,820 --> 00:04:04,970 change is that there's people who understand lots of 82 00:04:04,970 --> 00:04:07,490 individual points, but how do you assemble it into a 83 00:04:07,490 --> 00:04:09,890 coherent plan for change? 84 00:04:09,890 --> 00:04:12,200 Well, you need forums for discussion. 85 00:04:12,200 --> 00:04:14,940 And if the reports in the media are, oh, don't teach the 86 00:04:14,940 --> 00:04:17,970 multiplication table, or do teach it but do it with lots 87 00:04:17,970 --> 00:04:20,709 of drill, well, it's hard to get in a discussion of, well, 88 00:04:20,709 --> 00:04:23,280 actually you'd like to teach it in a different way, where 89 00:04:23,280 --> 00:04:29,990 instead of memorizing this you say, well, 6 times 9 is like 6 90 00:04:29,990 --> 00:04:34,630 times 10, which is 60, minus 6, which is 54. 91 00:04:34,630 --> 00:04:38,090 So there's no space for putting things like that into 92 00:04:38,090 --> 00:04:39,270 public discussion. 93 00:04:39,270 --> 00:04:41,510 And one of the purposes of classes like 94 00:04:41,510 --> 00:04:45,140 this is to do that. 95 00:04:45,140 --> 00:04:45,710 OK. 96 00:04:45,710 --> 00:04:48,720 Today, we're going to talk about lecture planning and 97 00:04:48,720 --> 00:04:50,320 performing. 98 00:04:50,320 --> 00:04:54,900 What we've done so far is the flow of the ideas in this 99 00:04:54,900 --> 00:04:56,185 class has gone as follows. 100 00:04:58,960 --> 00:05:00,340 So this is a logical flow. 101 00:05:00,340 --> 00:05:02,860 We did it slightly out of order, because it's the 102 00:05:02,860 --> 00:05:04,460 preparation flow, slightly different 103 00:05:04,460 --> 00:05:05,710 than the logical flow. 104 00:05:08,470 --> 00:05:10,710 You work out your course goals, or even 105 00:05:10,710 --> 00:05:11,960 your curriculum goals. 106 00:05:18,590 --> 00:05:21,380 And then you decide, how are you going to tell whether 107 00:05:21,380 --> 00:05:22,630 you've reached those goals? 108 00:05:22,630 --> 00:05:24,813 Let me just write the goal a little clearer. 109 00:05:28,890 --> 00:05:30,910 And with problems, tests, that's the way you 110 00:05:30,910 --> 00:05:34,860 operationalize your goals. 111 00:05:34,860 --> 00:05:37,320 And then given that you have those kind of problems, well, 112 00:05:37,320 --> 00:05:40,610 now you have a pretty concrete idea of what it is you're 113 00:05:40,610 --> 00:05:43,650 trying for, because you have concrete examples of it. 114 00:05:43,650 --> 00:05:51,550 Well, lectures, recitations, so I'll put et cetera here. 115 00:05:51,550 --> 00:05:55,750 What do you do with your contact time? 116 00:05:55,750 --> 00:05:57,750 This is the overall structure. 117 00:05:57,750 --> 00:06:00,840 This is at the level where it makes concrete sense. 118 00:06:00,840 --> 00:06:03,730 And this is, what do you do when the rubber hits the road, 119 00:06:03,730 --> 00:06:05,330 what do you do in lecture? 120 00:06:05,330 --> 00:06:06,890 Last time, what we did is we talked 121 00:06:06,890 --> 00:06:08,510 about interactive teaching. 122 00:06:08,510 --> 00:06:12,240 And there was, basically, several time scales over which 123 00:06:12,240 --> 00:06:14,530 you can make the class interactive. 124 00:06:14,530 --> 00:06:17,770 The longest time scale was the wood blocked example, and I'll 125 00:06:17,770 --> 00:06:20,980 answer a question about that in just a moment. 126 00:06:20,980 --> 00:06:24,450 So now, continuing the theme of where the rubber hits the 127 00:06:24,450 --> 00:06:25,840 road, today-- 128 00:06:40,050 --> 00:06:43,230 Now that you have some techniques, how do you 129 00:06:43,230 --> 00:06:44,870 assemble it into a lecture? 130 00:06:44,870 --> 00:06:47,910 And I use both words advisedly and deliberately. 131 00:06:47,910 --> 00:06:50,010 So plan, it's essential to plan. 132 00:06:50,010 --> 00:06:52,160 And performance is essential. 133 00:06:52,160 --> 00:06:53,660 People forget that. 134 00:06:53,660 --> 00:06:59,360 They forget that lecturing and teaching is a public act, and 135 00:06:59,360 --> 00:07:02,080 when they forget that, the lectures are flat. 136 00:07:02,080 --> 00:07:05,160 We're going to talk about the techniques for doing that, 137 00:07:05,160 --> 00:07:08,110 starting with the Walter Lewin lecture that 138 00:07:08,110 --> 00:07:09,890 you watched for today. 139 00:07:09,890 --> 00:07:12,720 Because he actually has many, many examples, I think mostly 140 00:07:12,720 --> 00:07:15,470 good, of performance, and some that I think he 141 00:07:15,470 --> 00:07:17,060 could improve on. 142 00:07:17,060 --> 00:07:19,770 And we'll discuss that and work out and induce general 143 00:07:19,770 --> 00:07:22,230 principles that you can use. 144 00:07:22,230 --> 00:07:23,170 OK. 145 00:07:23,170 --> 00:07:24,530 Those are the questions from last time. 146 00:07:24,530 --> 00:07:27,450 There was a slight review of interactive teaching as well 147 00:07:27,450 --> 00:07:28,790 and things like this. 148 00:07:28,790 --> 00:07:30,920 Now the question is, what do you do in lecture? 149 00:07:30,920 --> 00:07:33,030 How do you plan, and how do you perform? 150 00:07:33,030 --> 00:07:35,490 And a good way to start discussing that was actually 151 00:07:35,490 --> 00:07:40,980 to look at a master of the art and see what they do. 152 00:07:40,980 --> 00:07:42,940 Now no master is perfect. 153 00:07:42,940 --> 00:07:45,580 But I think Walter Lewin did so many things well it's 154 00:07:45,580 --> 00:07:48,570 really worth understanding what he did and looking at it. 155 00:07:48,570 --> 00:07:52,530 So what did you notice from your homework problem? 156 00:07:52,530 --> 00:07:54,690 Basically, what did you notice that he did? 157 00:07:54,690 --> 00:07:57,220 And I have a bunch of things as well. 158 00:07:57,220 --> 00:07:58,810 And we'll just write them down. 159 00:07:58,810 --> 00:08:01,110 Because what we'll do, as before-- 160 00:08:01,110 --> 00:08:04,370 we've done this several times now-- by looking at examples, 161 00:08:04,370 --> 00:08:07,900 we can induce general principles. 162 00:08:07,900 --> 00:08:09,420 Actually, I'll leave this here, and 163 00:08:09,420 --> 00:08:10,670 I'll erase these guys. 164 00:08:17,690 --> 00:08:21,730 While I'm erasing, just pull out your homework and the 165 00:08:21,730 --> 00:08:23,600 things you've noted down. 166 00:08:23,600 --> 00:08:27,830 And actually, take a minute and check in with your 167 00:08:27,830 --> 00:08:31,320 neighbor and see if your lists overlap. 168 00:08:31,320 --> 00:08:33,740 And sort of vet your lists with each other. 169 00:08:33,740 --> 00:08:35,940 And if you didn't think about anything that could be 170 00:08:35,940 --> 00:08:37,799 improved, see if you can remember anything that you 171 00:08:37,799 --> 00:08:39,580 would have done differently. 172 00:08:39,580 --> 00:08:43,010 So let's share all the points. 173 00:08:43,010 --> 00:08:46,090 So I can see that you've come up with a lot of examples, and 174 00:08:46,090 --> 00:08:48,720 I actually had a bunch too, because 175 00:08:48,720 --> 00:08:50,070 it's such a rich lecture. 176 00:08:50,070 --> 00:08:56,460 So let's see what things that were done and what was either 177 00:08:56,460 --> 00:08:58,460 that you would keep or you would change. 178 00:08:58,460 --> 00:09:02,130 And I'll put them in one or the other side, according to 179 00:09:02,130 --> 00:09:04,500 how you categorize them. 180 00:09:04,500 --> 00:09:05,750 Any one example? 181 00:09:07,930 --> 00:09:08,835 Yeah, Wendy. 182 00:09:08,835 --> 00:09:11,174 AUDIENCE: He awards students when something might not be 183 00:09:11,174 --> 00:09:12,662 intuitive for them or something. 184 00:09:12,662 --> 00:09:16,878 So when he was doing analysis of error under the square 185 00:09:16,878 --> 00:09:19,936 root, and he was saying, OK, this might not be something 186 00:09:19,936 --> 00:09:21,094 you would know right now. 187 00:09:21,094 --> 00:09:23,078 I might not hold you responsible, but it's 188 00:09:23,078 --> 00:09:24,580 interesting [INAUDIBLE]. 189 00:09:24,580 --> 00:09:24,910 PROFESSOR: OK. 190 00:09:24,910 --> 00:09:28,030 So he tell students, look, this is 191 00:09:28,030 --> 00:09:29,720 harder or not intuitive. 192 00:09:29,720 --> 00:09:32,420 He gives them a gauge and tells them, look, you're don't 193 00:09:32,420 --> 00:09:34,200 have to worry about it before he says something. 194 00:09:38,356 --> 00:09:41,580 He gives the difficulty of something. 195 00:09:48,320 --> 00:09:48,860 OK. 196 00:09:48,860 --> 00:09:50,110 Why is that helpful? 197 00:09:52,720 --> 00:09:54,540 What does that do for students? 198 00:09:54,540 --> 00:09:54,960 Yeah. 199 00:09:54,960 --> 00:09:58,080 AUDIENCE: It sort of removes the tension of thinking, oh, 200 00:09:58,080 --> 00:10:00,125 man, I don't know this while they're trying to pay 201 00:10:00,125 --> 00:10:03,250 attention to the other [INAUDIBLE]. 202 00:10:03,250 --> 00:10:04,380 PROFESSOR: Right. 203 00:10:04,380 --> 00:10:04,590 Right. 204 00:10:04,590 --> 00:10:06,180 So it differentiates the lecture. 205 00:10:06,180 --> 00:10:09,500 So I'll put in other color the reasons. 206 00:10:09,500 --> 00:10:10,570 Yeah, so it gives some kind of 207 00:10:10,570 --> 00:10:12,060 differentiation to the lecture. 208 00:10:12,060 --> 00:10:13,295 It gives a structure to it. 209 00:10:13,295 --> 00:10:17,850 It gives you a way of evaluating so you know what 210 00:10:17,850 --> 00:10:19,430 are you supposed to be doing here and trying 211 00:10:19,430 --> 00:10:20,130 to learn from it. 212 00:10:20,130 --> 00:10:23,930 You don't all of a sudden trigger your reflex fear. 213 00:10:23,930 --> 00:10:25,260 So it minimizes fear. 214 00:10:30,090 --> 00:10:31,900 And it gives a clear expectation. 215 00:10:31,900 --> 00:10:36,250 So in the particular lecture, he didn't say anything was you 216 00:10:36,250 --> 00:10:38,440 absolutely have to know this. 217 00:10:38,440 --> 00:10:40,930 So there wasn't a flip example. 218 00:10:40,930 --> 00:10:43,850 But if it had been a flip example, it would have the 219 00:10:43,850 --> 00:10:44,730 same benefit. 220 00:10:44,730 --> 00:10:46,990 If he said, oh, this is really fundamental. 221 00:10:46,990 --> 00:10:49,500 You really, really, really, really need to know this, 222 00:10:49,500 --> 00:10:51,640 well, that also punctuate the lecture. 223 00:10:51,640 --> 00:10:54,765 So it minimize fear and sets expectations. 224 00:11:03,640 --> 00:11:07,010 To expand on this point, which is really fundamental, think 225 00:11:07,010 --> 00:11:09,980 about the difference between the way a novice perceives 226 00:11:09,980 --> 00:11:13,880 something and the way an expert perceives something. 227 00:11:13,880 --> 00:11:16,060 If you want to know how a novice perceives something, 228 00:11:16,060 --> 00:11:18,450 try to remember from the days when you were not a chess 229 00:11:18,450 --> 00:11:19,840 Grandmaster. 230 00:11:19,840 --> 00:11:21,530 That shouldn't be too hard for most of us, certainly 231 00:11:21,530 --> 00:11:23,310 not hard for me. 232 00:11:23,310 --> 00:11:25,550 You look at a chessboard, all the moves 233 00:11:25,550 --> 00:11:28,630 look kind of similar. 234 00:11:28,630 --> 00:11:30,120 Oh, I could move that pawn. 235 00:11:30,120 --> 00:11:31,370 You think about that for a bit. 236 00:11:31,370 --> 00:11:32,440 You analyze some moves. 237 00:11:32,440 --> 00:11:34,670 He takes, I take, he takes, I take. 238 00:11:34,670 --> 00:11:36,040 Hmm, OK, let me think about-- 239 00:11:36,040 --> 00:11:36,643 I could move the rook. 240 00:11:36,643 --> 00:11:37,450 I could castle. 241 00:11:37,450 --> 00:11:39,460 He takes, I take, or I'll move the bishop. 242 00:11:39,460 --> 00:11:41,770 And you sort of say, OK, I'll move the bishop. 243 00:11:41,770 --> 00:11:44,610 That's how the novice or medium chess player thinks, 244 00:11:44,610 --> 00:11:46,530 speaking from personal experience. 245 00:11:46,530 --> 00:11:48,400 The way the master or the Grandmaster looks at the 246 00:11:48,400 --> 00:11:51,290 chessboard, the chessboard has meaning. 247 00:11:51,290 --> 00:11:52,810 All the different pieces of it are kind of 248 00:11:52,810 --> 00:11:54,410 talking to each other. 249 00:11:54,410 --> 00:11:57,710 Hmm, that pawn structures is really full of holes. 250 00:11:57,710 --> 00:11:59,590 You really want to do something about that. 251 00:11:59,590 --> 00:12:05,170 So the undifferentiated mass of pieces that the notice sees 252 00:12:05,170 --> 00:12:07,410 is completely different from what the expert sees, which is 253 00:12:07,410 --> 00:12:09,610 why the expert can remember the chessboard 254 00:12:09,610 --> 00:12:13,060 and the novice can't. 255 00:12:13,060 --> 00:12:15,800 I noticed this exact same thing happened 256 00:12:15,800 --> 00:12:16,770 in my freshman year. 257 00:12:16,770 --> 00:12:19,230 I learned to play bridge I'd never played bridge before, 258 00:12:19,230 --> 00:12:23,540 and all my friends, who I don't know if they did me a 259 00:12:23,540 --> 00:12:25,440 favor or not, taught me to play bridge so I could play 260 00:12:25,440 --> 00:12:26,940 bridge with them. 261 00:12:26,940 --> 00:12:30,360 When I first was playing with them, at the end of the hand, 262 00:12:30,360 --> 00:12:31,760 everyone does the post mortem. 263 00:12:31,760 --> 00:12:34,600 You have four people, you play all the tricks, and everyone 264 00:12:34,600 --> 00:12:36,660 talks about what happened and it didn't happen. 265 00:12:36,660 --> 00:12:40,850 And they would say, Oh, yeah, why didn't you 266 00:12:40,850 --> 00:12:43,260 play the queen then? 267 00:12:43,260 --> 00:12:44,960 I was like queen of what? 268 00:12:44,960 --> 00:12:45,325 What queen? 269 00:12:45,325 --> 00:12:46,450 Did I have a queen? 270 00:12:46,450 --> 00:12:48,260 I didn't even remember the cards I had. 271 00:12:48,260 --> 00:12:49,440 I didn't even remember how many cards 272 00:12:49,440 --> 00:12:50,390 I had of each thing. 273 00:12:50,390 --> 00:12:52,810 I just sort of remembered the last card, maybe. 274 00:12:52,810 --> 00:12:55,560 Or more like, oh, phew, the hand's over. 275 00:12:55,560 --> 00:12:55,630 OK. 276 00:12:55,630 --> 00:12:58,650 I can't make anymore mistakes. 277 00:12:58,650 --> 00:13:00,350 That's how I would see it compared to how 278 00:13:00,350 --> 00:13:01,110 they would see it. 279 00:13:01,110 --> 00:13:03,120 And I was like, how could they ever even remember who had the 280 00:13:03,120 --> 00:13:03,890 queen of what? 281 00:13:03,890 --> 00:13:07,450 And by the end of, I don't know, six months, I would say, 282 00:13:07,450 --> 00:13:10,370 uh, why didn't you play the five then? 283 00:13:10,370 --> 00:13:12,490 Because all of a sudden, now I was doing 284 00:13:12,490 --> 00:13:13,520 exactly the same thing. 285 00:13:13,520 --> 00:13:14,480 The hands had meaning. 286 00:13:14,480 --> 00:13:15,900 The cards had meaning. 287 00:13:15,900 --> 00:13:22,240 So by doing this, by giving clues to the difficulty or 288 00:13:22,240 --> 00:13:24,250 ease of things, you're actually giving meaning. 289 00:13:24,250 --> 00:13:26,320 You're transferring some of that knowledge that you have 290 00:13:26,320 --> 00:13:30,590 as the expert to the student, who otherwise wouldn't know. 291 00:13:30,590 --> 00:13:34,510 There was another example of that in the lecture where he 292 00:13:34,510 --> 00:13:37,730 said, this is the most important 293 00:13:37,730 --> 00:13:39,155 equation in all of physics. 294 00:13:46,210 --> 00:13:50,780 He wrote that, and he boxed it, and he said, that's 295 00:13:50,780 --> 00:13:52,760 probably the most important equation in all of physics. 296 00:13:52,760 --> 00:13:54,490 So again, he's giving something 297 00:13:54,490 --> 00:13:55,910 that the expert knows. 298 00:13:55,910 --> 00:13:58,230 Because the expert knows, oh, yeah, when you see this, 299 00:13:58,230 --> 00:14:01,320 you're home free, and you know you can model so many physical 300 00:14:01,320 --> 00:14:02,310 systems with this. 301 00:14:02,310 --> 00:14:05,050 Let's tell the students how important it is so they have 302 00:14:05,050 --> 00:14:07,610 some way of thinking about it. 303 00:14:07,610 --> 00:14:10,230 OK So that's really fundamental. 304 00:14:10,230 --> 00:14:10,820 Others? 305 00:14:10,820 --> 00:14:12,430 Other points? 306 00:14:12,430 --> 00:14:13,010 Yes. 307 00:14:13,010 --> 00:14:17,312 AUDIENCE: He uses big ideas and terms for them, like 308 00:14:17,312 --> 00:14:21,630 uncertainty and restoring [INAUDIBLE]. 309 00:14:21,630 --> 00:14:21,990 PROFESSOR: OK. 310 00:14:21,990 --> 00:14:34,800 So he uses clear terms for big ideas, and he uses the same 311 00:14:34,800 --> 00:14:35,950 term each time. 312 00:14:35,950 --> 00:14:37,170 He's careful to do that, so you don't 313 00:14:37,170 --> 00:14:38,420 wonder why it changed. 314 00:14:38,420 --> 00:14:45,870 How does that help students, to give things names and 315 00:14:45,870 --> 00:14:46,830 repeatable names? 316 00:14:46,830 --> 00:14:47,313 Yeah. 317 00:14:47,313 --> 00:14:51,660 AUDIENCE: Gives them fewer facts to [INAUDIBLE]. 318 00:14:51,660 --> 00:14:52,380 PROFESSOR: Yeah. 319 00:14:52,380 --> 00:14:53,880 It gives a structure to everything. 320 00:14:56,560 --> 00:14:57,300 It's gone now. 321 00:14:57,300 --> 00:15:00,620 But it gives a structure, repeatable abstractions that 322 00:15:00,620 --> 00:15:04,050 you can reuse over and over again. 323 00:15:04,050 --> 00:15:05,300 Structures. 324 00:15:08,150 --> 00:15:09,670 In fact, it's another example of this. 325 00:15:09,670 --> 00:15:10,920 It structures the knowledge. 326 00:15:15,170 --> 00:15:16,770 So it's structured in his mind. 327 00:15:16,770 --> 00:15:17,680 He's the expert. 328 00:15:17,680 --> 00:15:21,770 He has a really good, sound flexible structure. 329 00:15:21,770 --> 00:15:24,820 And part of the job of really good teaching is to help the 330 00:15:24,820 --> 00:15:28,555 students build that structure. 331 00:15:28,555 --> 00:15:29,513 Yes. 332 00:15:29,513 --> 00:15:31,429 AUDIENCE: When he's characterizing visions, he 333 00:15:31,429 --> 00:15:34,400 really emphasizes building intuition for why the vision 334 00:15:34,400 --> 00:15:38,910 is the way it is and why it's [INAUDIBLE]. 335 00:15:38,910 --> 00:15:39,410 PROFESSOR: OK. 336 00:15:39,410 --> 00:15:43,070 So he emphasizes the why of the equation. 337 00:15:43,070 --> 00:15:46,390 So why is it plausible that it, for example, has-- 338 00:15:46,390 --> 00:15:47,850 Can you give an example of that? 339 00:15:47,850 --> 00:15:50,350 AUDIENCE: He talked a bit about why [INAUDIBLE]. 340 00:15:54,850 --> 00:15:55,380 PROFESSOR: OK. 341 00:15:55,380 --> 00:15:55,600 Yeah. 342 00:15:55,600 --> 00:15:59,560 There was an example where the frequency was derived, so 343 00:15:59,560 --> 00:16:01,610 emphasizes the physical meaning and 344 00:16:01,610 --> 00:16:02,860 interpretations also. 345 00:16:11,640 --> 00:16:12,750 And interpretation. 346 00:16:12,750 --> 00:16:18,650 So the example he gave, which I think is a good one, is in a 347 00:16:18,650 --> 00:16:24,650 pendulum, why is the period independent of the mass? 348 00:16:24,650 --> 00:16:25,900 For a pendulum-- 349 00:16:39,610 --> 00:16:39,850 OK. 350 00:16:39,850 --> 00:16:43,880 And the argument for that was, oh, well, if you double the 351 00:16:43,880 --> 00:16:47,710 mass, you double the force, but you double the mass, so 352 00:16:47,710 --> 00:16:48,945 you haven't changed the acceleration. 353 00:16:48,945 --> 00:16:50,850 So everything stays the same. 354 00:16:50,850 --> 00:16:54,340 And he contrasted that. 355 00:16:54,340 --> 00:16:56,030 He didn't just do this one. 356 00:16:56,030 --> 00:16:59,700 He contrasted that with what happens in a spring. 357 00:16:59,700 --> 00:16:59,850 OK. 358 00:16:59,850 --> 00:17:02,390 So how does this help the students? 359 00:17:02,390 --> 00:17:03,557 What's the benefit? 360 00:17:03,557 --> 00:17:06,717 AUDIENCE: I think it helps them because it makes them 361 00:17:06,717 --> 00:17:08,194 feel like they could potentially derive it 362 00:17:08,194 --> 00:17:11,030 themselves and then afterwards check their answer. 363 00:17:11,030 --> 00:17:12,089 PROFESSOR: OK. 364 00:17:12,089 --> 00:17:12,460 Right. 365 00:17:12,460 --> 00:17:14,700 He's modeling, actually, what you would do. 366 00:17:14,700 --> 00:17:19,339 You, yourself, as a physicist, and hopefully as a student, 367 00:17:19,339 --> 00:17:21,310 you want to be able to check your answer by 368 00:17:21,310 --> 00:17:22,560 making sense of it. 369 00:17:31,840 --> 00:17:34,740 It promotes sense-making is a shorthand for it. 370 00:17:34,740 --> 00:17:37,674 Let me just push the other board up. 371 00:17:37,674 --> 00:17:39,630 AUDIENCE: Well, and it's also [INAUDIBLE]. 372 00:17:42,330 --> 00:17:43,360 PROFESSOR: Oh, sorry. 373 00:17:43,360 --> 00:17:44,818 AUDIENCE: --which is probably the most 374 00:17:44,818 --> 00:17:47,020 difficult thing to teach. 375 00:17:47,020 --> 00:17:49,314 I thought that was the best part of the lecture. 376 00:17:52,646 --> 00:17:56,454 One thing is to give a list of facts so you learn and then 377 00:17:56,454 --> 00:17:57,610 you can use. 378 00:17:57,610 --> 00:17:58,590 PROFESSOR: Right. 379 00:17:58,590 --> 00:18:01,548 AUDIENCE: That seems to be the closest to teaching how to 380 00:18:01,548 --> 00:18:03,273 think, which is the most difficult thing 381 00:18:03,273 --> 00:18:04,510 you can ever teach. 382 00:18:04,510 --> 00:18:05,760 PROFESSOR: OK. 383 00:18:07,980 --> 00:18:09,370 It teaches how to think, because it's a 384 00:18:09,370 --> 00:18:10,620 transferable skill. 385 00:18:16,130 --> 00:18:19,340 You may never have to analyze a pendulum again as a student 386 00:18:19,340 --> 00:18:20,540 outside of the class. 387 00:18:20,540 --> 00:18:24,570 But whatever formula you get, you can use that same method 388 00:18:24,570 --> 00:18:28,060 to say, does the formula make sense? 389 00:18:28,060 --> 00:18:30,750 So that's teaching a way of thinking. 390 00:18:30,750 --> 00:18:32,060 It's a transferable skill. 391 00:18:35,259 --> 00:18:37,097 Yeah, Adrian. 392 00:18:37,097 --> 00:18:40,280 AUDIENCE: He's very, very explicit about his notation. 393 00:18:40,280 --> 00:18:40,670 PROFESSOR: OK. 394 00:18:40,670 --> 00:18:41,920 Explicit about notation. 395 00:18:44,430 --> 00:18:45,340 Can you give an example? 396 00:18:45,340 --> 00:18:48,707 AUDIENCE: Well, even when [INAUDIBLE] 397 00:18:51,593 --> 00:18:53,757 method of a string, he says, this is 398 00:18:53,757 --> 00:18:54,855 the method of a string. 399 00:18:54,855 --> 00:19:00,946 And he'll label an equation with the whole, writes it out. 400 00:19:00,946 --> 00:19:02,180 In [INAUDIBLE] terms. 401 00:19:02,180 --> 00:19:02,460 PROFESSOR: Right. 402 00:19:02,460 --> 00:19:03,720 He'll write everything out. 403 00:19:03,720 --> 00:19:05,600 So he's very explicit about notation. 404 00:19:05,600 --> 00:19:06,850 How does that help the students? 405 00:19:10,474 --> 00:19:11,610 What does that do for them? 406 00:19:11,610 --> 00:19:11,966 Yes. 407 00:19:11,966 --> 00:19:14,552 AUDIENCE: It makes it clearer and it makes 408 00:19:14,552 --> 00:19:16,740 mistakes hard to make. 409 00:19:16,740 --> 00:19:16,970 PROFESSOR: Right. 410 00:19:16,970 --> 00:19:19,010 It makes it hard to make mistakes. 411 00:19:19,010 --> 00:19:24,534 Again, so this is hard to make mistakes. 412 00:19:24,534 --> 00:19:25,784 Harder-- 413 00:19:32,230 --> 00:19:32,570 OK. 414 00:19:32,570 --> 00:19:36,950 And what makes it harder, and why is this so important? 415 00:19:36,950 --> 00:19:40,550 Because, as Adrian said, yeah, it may be intuitively obvious 416 00:19:40,550 --> 00:19:42,990 to the expert physicist that, of course, L is the length. 417 00:19:42,990 --> 00:19:46,230 That's why you chose L, because length begins with L. 418 00:19:46,230 --> 00:19:50,090 But for the student, everything is new. 419 00:19:50,090 --> 00:19:52,860 The chess example, the knocking down the chessboard 420 00:19:52,860 --> 00:19:55,490 problem and seeing how well you can reconstruct it, 421 00:19:55,490 --> 00:19:57,860 explains so much. 422 00:19:57,860 --> 00:20:00,480 The novice, they can't reconstruct the chessboard. 423 00:20:00,480 --> 00:20:03,140 That's because each piece on the chessboard is not 424 00:20:03,140 --> 00:20:04,480 intuitively obvious. 425 00:20:04,480 --> 00:20:06,650 Whereas, for the chess master, it's so easy to reconstruct 426 00:20:06,650 --> 00:20:09,170 the board, because, to them, it is intuitively obvious 427 00:20:09,170 --> 00:20:10,735 that, of course, you have three pawns in 428 00:20:10,735 --> 00:20:11,680 front of your king. 429 00:20:11,680 --> 00:20:14,100 Unless you have some really crazy opening, of course 430 00:20:14,100 --> 00:20:15,990 you've castled your kind and you have three pawns sitting 431 00:20:15,990 --> 00:20:18,136 in front of it protecting it. 432 00:20:18,136 --> 00:20:21,890 And it's just obvious from the configuration of the pawns 433 00:20:21,890 --> 00:20:24,080 that, of course, with that pawn configuration you did 434 00:20:24,080 --> 00:20:24,670 this opening. 435 00:20:24,670 --> 00:20:27,620 And of course, the king is defended in this way. 436 00:20:27,620 --> 00:20:31,610 So what's obvious to the expert is completely obscure 437 00:20:31,610 --> 00:20:32,860 to the non-expert. 438 00:20:35,446 --> 00:20:39,090 You want them to not have to worry and fill up their 439 00:20:39,090 --> 00:20:41,500 short-term memory slots with things that really are 440 00:20:41,500 --> 00:20:44,380 obvious, so you put that right on the diagram. 441 00:20:46,980 --> 00:20:49,240 He wrote M, I think, and then there was an L there. 442 00:20:49,240 --> 00:20:51,120 So right away, you just look at the diagram. 443 00:20:51,120 --> 00:20:54,540 You know what L is. 444 00:20:54,540 --> 00:20:55,040 OK. 445 00:20:55,040 --> 00:20:57,030 Other things that were done? 446 00:20:57,030 --> 00:20:58,280 There are so many. 447 00:21:01,530 --> 00:21:03,986 AUDIENCE: He asked the students to help [INAUDIBLE] 448 00:21:09,552 --> 00:21:10,470 passively but actively. 449 00:21:10,470 --> 00:21:11,020 PROFESSOR: OK. 450 00:21:11,020 --> 00:21:12,270 He asked for help. 451 00:21:17,660 --> 00:21:19,430 That increased participation. 452 00:21:26,780 --> 00:21:27,970 How did he ask for help? 453 00:21:27,970 --> 00:21:29,920 What were some examples of that? 454 00:21:29,920 --> 00:21:30,840 AUDIENCE: [INAUDIBLE] 455 00:21:30,840 --> 00:21:33,780 the gun spray toward the [INAUDIBLE] 456 00:21:33,780 --> 00:21:36,606 of the harmonic motion, he asked a student for help 457 00:21:36,606 --> 00:21:38,490 holding the end of the paper. 458 00:21:38,490 --> 00:21:38,890 PROFESSOR: Right. 459 00:21:38,890 --> 00:21:39,880 AUDIENCE: And then, when he drew the big 460 00:21:39,880 --> 00:21:40,780 pendulum where he-- 461 00:21:40,780 --> 00:21:43,070 PROFESSOR: Oh, the final pendulum. 462 00:21:43,070 --> 00:21:43,510 Right. 463 00:21:43,510 --> 00:21:45,980 Several times, actually-- 464 00:21:45,980 --> 00:21:46,770 let's see. 465 00:21:46,770 --> 00:21:48,020 I think I have it here-- 466 00:21:51,270 --> 00:21:55,800 Lewin says, I want to hear you loud, because 467 00:21:55,800 --> 00:21:56,450 he didn't hear them. 468 00:21:56,450 --> 00:21:59,090 He wanted people to really participate, and then they 469 00:21:59,090 --> 00:22:00,910 really started counting. 470 00:22:00,910 --> 00:22:04,270 So they were really involved in what's going to happen by 471 00:22:04,270 --> 00:22:06,580 the end of 10 swings. 472 00:22:06,580 --> 00:22:09,050 It involved them, so it's a form of interactive teaching. 473 00:22:09,050 --> 00:22:10,500 He's getting people more involved. 474 00:22:10,500 --> 00:22:11,228 Yes, Adrian. 475 00:22:11,228 --> 00:22:15,360 AUDIENCE: On the other hand, I thought he pretty much never 476 00:22:15,360 --> 00:22:16,580 asked questions. 477 00:22:16,580 --> 00:22:17,910 PROFESSOR: OK. 478 00:22:17,910 --> 00:22:19,910 He didn't ask them questions. 479 00:22:19,910 --> 00:22:21,710 Right. 480 00:22:21,710 --> 00:22:24,290 Yeah, it's good that he asked for help, and that is one way 481 00:22:24,290 --> 00:22:25,670 of involving them. 482 00:22:25,670 --> 00:22:28,076 So it made them interested, but it didn't necessarily-- 483 00:22:30,590 --> 00:22:33,170 It increased their motivation to learn about the subject, 484 00:22:33,170 --> 00:22:35,910 but it didn't necessarily actually help them learn right 485 00:22:35,910 --> 00:22:38,130 then about something. 486 00:22:38,130 --> 00:22:39,570 So he would change. 487 00:22:48,150 --> 00:22:49,070 OK. 488 00:22:49,070 --> 00:22:51,530 Can anyone else think the spots where he could have 489 00:22:51,530 --> 00:22:52,320 asked questions? 490 00:22:52,320 --> 00:22:53,708 Yeah. 491 00:22:53,708 --> 00:22:56,585 AUDIENCE: I think there were natural pauses, natural breaks 492 00:22:56,585 --> 00:22:57,710 [INAUDIBLE]. 493 00:22:57,710 --> 00:23:01,231 For instance, when the air tracks through the pendulum, 494 00:23:01,231 --> 00:23:02,662 he didn't stop there. 495 00:23:02,662 --> 00:23:06,955 He never stopped to let students think about what they 496 00:23:06,955 --> 00:23:07,432 [INAUDIBLE]. 497 00:23:07,432 --> 00:23:10,310 PROFESSOR: OK. 498 00:23:10,310 --> 00:23:12,460 He didn't pause at the natural break points. 499 00:23:12,460 --> 00:23:13,904 AUDIENCE: He didn't pause at the natural-- 500 00:23:13,904 --> 00:23:14,396 PROFESSOR: Yeah. 501 00:23:14,396 --> 00:23:15,646 AUDIENCE: [INAUDIBLE]. 502 00:23:24,240 --> 00:23:24,630 PROFESSOR: Right. 503 00:23:24,630 --> 00:23:27,920 One example that I remember of that, because I was also 504 00:23:27,920 --> 00:23:33,910 watching for that, was he wanted to show Hooke's law and 505 00:23:33,910 --> 00:23:36,270 he plotted out-- 506 00:23:36,270 --> 00:23:37,520 I'll draw an example here. 507 00:23:46,000 --> 00:23:48,720 He plotted force verses extension for a bunch of 508 00:23:48,720 --> 00:23:49,340 extensions. 509 00:23:49,340 --> 00:23:51,050 And forces was the weight of those springs. 510 00:23:51,050 --> 00:23:53,060 And he got a bunch of points here, and he drew this. 511 00:23:53,060 --> 00:23:56,140 Then he pulled one of the springs, and he stretched the 512 00:23:56,140 --> 00:23:58,180 hell out of it. 513 00:23:58,180 --> 00:24:00,780 And then he let go of it, and it came back much longer than 514 00:24:00,780 --> 00:24:02,160 it started. 515 00:24:02,160 --> 00:24:05,750 And then he drew what happened on the graph. 516 00:24:05,750 --> 00:24:09,910 So one thing he could have done, rather than drawing it 517 00:24:09,910 --> 00:24:11,590 straight, is the following. 518 00:24:15,040 --> 00:24:18,370 You say, OK, how do we describe what happened to that 519 00:24:18,370 --> 00:24:19,933 spring as I stretched it? 520 00:24:19,933 --> 00:24:25,180 Was it this curve, that curve, or that curve? 521 00:24:25,180 --> 00:24:28,900 A, B, C. You don't have to spend long on it, just 10 522 00:24:28,900 --> 00:24:32,050 seconds, or even 30 seconds. 523 00:24:32,050 --> 00:24:34,340 But instead, he just told them which it was. 524 00:24:34,340 --> 00:24:37,350 So actually, which was it, A, B, or C. 525 00:24:37,350 --> 00:24:38,280 AUDIENCE: C. 526 00:24:38,280 --> 00:24:38,950 PROFESSOR: C. Right. 527 00:24:38,950 --> 00:24:43,990 It was C. And just the act of thinking about that forces you 528 00:24:43,990 --> 00:24:48,560 to connect the physics and the mathematics once again, even 529 00:24:48,560 --> 00:24:49,330 this small amount. 530 00:24:49,330 --> 00:24:50,260 Yes, Lat. 531 00:24:50,260 --> 00:24:51,220 AUDIENCE: Wouldn't the same apply to you? 532 00:24:51,220 --> 00:24:54,100 I've never thought about asking a question. 533 00:24:54,100 --> 00:24:55,540 Maybe you answered it immediately. 534 00:24:55,540 --> 00:24:57,950 [INAUDIBLE]. 535 00:24:57,950 --> 00:24:58,240 PROFESSOR: Right. 536 00:24:58,240 --> 00:24:59,690 OK. 537 00:24:59,690 --> 00:25:01,430 He didn't pause at natural break points, and he 538 00:25:01,430 --> 00:25:02,795 didn't pause at-- 539 00:25:02,795 --> 00:25:03,730 AUDIENCE: [INAUDIBLE] smaller time scale? 540 00:25:03,730 --> 00:25:04,330 PROFESSOR: Yes. 541 00:25:04,330 --> 00:25:05,716 Not the smaller time scale. 542 00:25:05,716 --> 00:25:06,966 Right. 543 00:25:08,760 --> 00:25:10,650 No five-second pause. 544 00:25:16,020 --> 00:25:17,620 So the questions are almost rhetorical. 545 00:25:29,810 --> 00:25:32,680 I would say it's one of the dangers of being such a good 546 00:25:32,680 --> 00:25:36,160 performer, which he is. 547 00:25:36,160 --> 00:25:38,080 He's fantastic, I think. 548 00:25:38,080 --> 00:25:41,320 And one of the things he does so well in his performance is 549 00:25:41,320 --> 00:25:42,030 connecting-- 550 00:25:42,030 --> 00:25:45,890 which you mentioned over here-- 551 00:25:45,890 --> 00:25:49,020 the physics and the mathematics, explaining the 552 00:25:49,020 --> 00:25:51,740 physical meaning and interpretation, that top item. 553 00:25:51,740 --> 00:25:53,210 He does that so well. 554 00:25:53,210 --> 00:25:55,970 But one of the dangers of being such a good performer is 555 00:25:55,970 --> 00:26:01,080 that you just steamroller over the students, and you become, 556 00:26:01,080 --> 00:26:02,920 in some ways, more important than the students. 557 00:26:05,670 --> 00:26:08,040 Yeah. 558 00:26:08,040 --> 00:26:10,780 You'd be able to do less in lecture, but the five-second 559 00:26:10,780 --> 00:26:14,030 pause is really important to have everyone tracking and 560 00:26:14,030 --> 00:26:15,600 following with you. 561 00:26:15,600 --> 00:26:18,390 Other items? 562 00:26:18,390 --> 00:26:18,700 Let's see. 563 00:26:18,700 --> 00:26:18,910 Someone I haven't-- 564 00:26:18,910 --> 00:26:21,430 Yeah, Tsu. 565 00:26:21,430 --> 00:26:24,860 AUDIENCE: Sometimes, when he says, this is totally 566 00:26:24,860 --> 00:26:28,290 non-intuitive, he kind of just accepted that. 567 00:26:28,290 --> 00:26:33,190 And I think it would have been nice if he had given a reason 568 00:26:33,190 --> 00:26:37,920 for why this had to be, instead of just saying-- 569 00:26:37,920 --> 00:26:38,930 PROFESSOR: Yeah. 570 00:26:38,930 --> 00:26:40,040 OK. 571 00:26:40,040 --> 00:26:42,050 When he said things were non-intuitive, he sometimes 572 00:26:42,050 --> 00:26:44,440 didn't explain why it was non-intuitive. 573 00:26:44,440 --> 00:26:48,920 So the one I'm thinking of is he said, no matter what the 574 00:26:48,920 --> 00:26:51,700 amplitude is, the period is the same. 575 00:26:51,700 --> 00:26:53,420 And he said it isn't intuitive. 576 00:26:53,420 --> 00:26:57,910 So that was good, in that he did tell people-- 577 00:26:57,910 --> 00:26:59,160 Where was that? 578 00:27:03,070 --> 00:27:05,820 Yeah, it's here. 579 00:27:05,820 --> 00:27:06,930 He gives a difficulty. 580 00:27:06,930 --> 00:27:08,710 He says, for example, this isn't intuitive. 581 00:27:08,710 --> 00:27:11,440 You should be surprised that the period is independent of 582 00:27:11,440 --> 00:27:12,620 the amplitude. 583 00:27:12,620 --> 00:27:16,450 But he doesn't give them another way of seeing 584 00:27:16,450 --> 00:27:17,320 why it should be. 585 00:27:17,320 --> 00:27:19,400 They do the derivation, and you find that it is 586 00:27:19,400 --> 00:27:20,340 independent of the amplitude. 587 00:27:20,340 --> 00:27:21,590 But why? 588 00:27:36,830 --> 00:27:39,440 And you can explain that sort of 589 00:27:39,440 --> 00:27:42,100 intuitively just by saying-- 590 00:27:45,680 --> 00:27:47,590 I'll give you a quick explanation of that. 591 00:27:47,590 --> 00:27:50,360 So it is, actually, an amazing fact. 592 00:27:50,360 --> 00:27:53,300 I'll give you a quick explanation of the unintuitive 593 00:27:53,300 --> 00:27:56,140 fact that the period is independent of the amplitude. 594 00:27:56,140 --> 00:27:57,390 OK? 595 00:28:00,940 --> 00:28:04,820 This is a scaling argument. 596 00:28:04,820 --> 00:28:10,830 E, G. OK. 597 00:28:10,830 --> 00:28:14,160 Let's estimate how long it takes a mass to move a 598 00:28:14,160 --> 00:28:23,140 distance, A. Well, it has some acceleration, a, small a. 599 00:28:23,140 --> 00:28:25,430 This is the amplitude, and that's the period. 600 00:28:25,430 --> 00:28:28,130 So the mass has some acceleration, little a. 601 00:28:30,950 --> 00:28:35,675 And in some time, t, the period, or some fraction of 602 00:28:35,675 --> 00:28:39,020 the period, let's say a quarter of the period, it goes 603 00:28:39,020 --> 00:28:45,490 this distance, give or take factors of 2 and whatnot. 604 00:28:45,490 --> 00:28:50,780 So this is roughly the amplitude. 605 00:28:50,780 --> 00:28:55,210 Now we want to figure out, what is this A here? 606 00:28:55,210 --> 00:29:05,180 Well, A is the force over the mass. 607 00:29:07,770 --> 00:29:10,830 And the typical force, that's coming from the spring. 608 00:29:10,830 --> 00:29:14,280 So it's a spring constant times the extension. 609 00:29:14,280 --> 00:29:16,235 The typical extension is the amplitude. 610 00:29:19,620 --> 00:29:21,100 OK? 611 00:29:21,100 --> 00:29:23,570 k times A is your force, divided by m, so we'll put 612 00:29:23,570 --> 00:29:25,150 that in there. 613 00:29:25,150 --> 00:29:26,400 OK. 614 00:29:30,310 --> 00:29:33,260 Oh, look at that. 615 00:29:33,260 --> 00:29:34,510 Hmm. 616 00:29:36,990 --> 00:29:39,960 And in fact, there you have t is proportional to 617 00:29:39,960 --> 00:29:41,800 square root of m/k. 618 00:29:41,800 --> 00:29:44,550 So you've got not only that it's independent of the 619 00:29:44,550 --> 00:29:54,450 amplitude, but you've got the whole story, 620 00:29:54,450 --> 00:29:55,650 except for the 2 pi. 621 00:29:55,650 --> 00:29:59,060 So intuitively, what it's saying is that, yeah, if you 622 00:29:59,060 --> 00:30:02,800 move yourself farther out, you have father to go. 623 00:30:02,800 --> 00:30:05,770 But you're pulled harder by just enough to make 624 00:30:05,770 --> 00:30:07,770 the time the same. 625 00:30:07,770 --> 00:30:09,990 And so not only is it an intuitive 626 00:30:09,990 --> 00:30:11,450 argument, it's very plausible. 627 00:30:11,450 --> 00:30:14,700 And Galileo extended it to the pendulum, and he thought he 628 00:30:14,700 --> 00:30:17,870 found a proof to show that the pendulum actually has a period 629 00:30:17,870 --> 00:30:20,190 independent of amplitude. 630 00:30:20,190 --> 00:30:23,780 In the pendulum, the amplitude is related to the restoring 631 00:30:23,780 --> 00:30:27,600 force, so he thought the period of the pendulum was 632 00:30:27,600 --> 00:30:30,160 independent of amplitude, not just for a regular spring. 633 00:30:30,160 --> 00:30:33,000 And that proof turned out to have a slight error in it. 634 00:30:33,000 --> 00:30:36,760 But as Walter Lewin pointed out, that's only true at large 635 00:30:36,760 --> 00:30:39,620 angles, and at small angles, you can't tell the difference. 636 00:30:39,620 --> 00:30:42,570 So you can actually explain these non-intuitive pieces in 637 00:30:42,570 --> 00:30:45,270 short ways that don't require doing a full calculation. 638 00:30:45,270 --> 00:30:48,020 And that is important to do, I think. 639 00:30:48,020 --> 00:30:48,320 OK. 640 00:30:48,320 --> 00:30:49,430 So why don't we take a 10-minute 641 00:30:49,430 --> 00:30:50,530 break, and then we'll-- 642 00:30:50,530 --> 00:30:52,790 Oh, do you have a quick comment? 643 00:30:52,790 --> 00:30:53,190 Go ahead. 644 00:30:53,190 --> 00:30:55,660 AUDIENCE: One other thing that I thought he should have done. 645 00:30:55,660 --> 00:30:56,154 PROFESSOR: Yeah? 646 00:30:56,154 --> 00:30:57,142 AUDIENCE: Which is actually motivate 647 00:30:57,142 --> 00:30:59,612 why this is so important. 648 00:30:59,612 --> 00:31:03,070 He mentioned [INAUDIBLE], as you said, that it's the most 649 00:31:03,070 --> 00:31:04,058 important thing in physics. 650 00:31:04,058 --> 00:31:06,362 But actually, I thought it would have been nice to give 651 00:31:06,362 --> 00:31:08,010 some real examples of how [INAUDIBLE]. 652 00:31:12,490 --> 00:31:13,200 PROFESSOR: OK. 653 00:31:13,200 --> 00:31:13,670 Yeah. 654 00:31:13,670 --> 00:31:15,350 Answer the "Who cares?" question. 655 00:31:21,970 --> 00:31:22,230 Right. 656 00:31:22,230 --> 00:31:24,030 And that's a good point. 657 00:31:24,030 --> 00:31:28,520 I teach physics myself, so actually that one slipped me. 658 00:31:28,520 --> 00:31:31,700 Because this is, again, the expert blind spot. 659 00:31:31,700 --> 00:31:35,750 So he put that equation there, and I was so glad he said, 660 00:31:35,750 --> 00:31:37,510 most important equation in physics. 661 00:31:37,510 --> 00:31:40,920 And to myself, I thought, yeah, right on. 662 00:31:40,920 --> 00:31:42,450 You use it in electromagnetism. 663 00:31:42,450 --> 00:31:44,840 The whole theory of quantum electrodynamics depends on it. 664 00:31:44,840 --> 00:31:46,590 You use it in modeling materials. 665 00:31:46,590 --> 00:31:47,620 It's everywhere. 666 00:31:47,620 --> 00:31:50,240 So all those thoughts went through my mind right away. 667 00:31:50,240 --> 00:31:53,135 And I thought, wow, that's equivalent to him saying it. 668 00:31:53,135 --> 00:31:55,660 But actually, it's not, because the students, of 669 00:31:55,660 --> 00:31:56,900 course, have none of those thoughts. 670 00:31:56,900 --> 00:32:01,000 And you really do need to say all that. 671 00:32:01,000 --> 00:32:02,250 Why? 672 00:32:07,980 --> 00:32:09,090 OK. 673 00:32:09,090 --> 00:32:11,350 We'll continue after our 10-minute break. 674 00:32:11,350 --> 00:32:15,430 And then we'll induce our lessons for lecture planning 675 00:32:15,430 --> 00:32:17,820 and performance, and I'll give you a structure that you can 676 00:32:17,820 --> 00:32:20,420 use when you plan and perform your own lectures. 677 00:32:20,420 --> 00:32:20,970 OK? 678 00:32:20,970 --> 00:32:22,760 There's several more points to come out. 679 00:32:22,760 --> 00:32:26,640 So we'll take some more points about Lewin's lecture at-- 680 00:32:26,640 --> 00:32:28,270 It's 10:05 by that clock. 681 00:32:28,270 --> 00:32:29,920 --10:15 by that clock. 682 00:32:29,920 --> 00:32:33,930 And if you didn't get a comment sheet, just grab one 683 00:32:33,930 --> 00:32:36,580 on your way in or on your way out. 684 00:32:36,580 --> 00:32:37,720 And I'll be here if people have any 685 00:32:37,720 --> 00:32:38,970 questions during the break. 686 00:32:43,770 --> 00:32:47,410 So a few other points. 687 00:32:47,410 --> 00:32:50,820 Let me give you one point from Lewin that I noticed and take 688 00:32:50,820 --> 00:32:54,320 some more points from you too. 689 00:32:54,320 --> 00:32:57,600 One I thought was very interesting, and which is not 690 00:32:57,600 --> 00:33:02,880 normally done in most physics lectures on springs. 691 00:33:02,880 --> 00:33:07,420 The way it's normally done in the physics class, you would 692 00:33:07,420 --> 00:33:11,320 do simple harmonic motion, you'd study a whole bunch 693 00:33:11,320 --> 00:33:14,590 about the spring, and then maybe a few lectures later, 694 00:33:14,590 --> 00:33:16,460 you might get to the pendulum. 695 00:33:16,460 --> 00:33:19,780 But Lewin actually did both in the same lecture, which I 696 00:33:19,780 --> 00:33:22,130 thought was very interesting and a really excellent choice. 697 00:33:45,410 --> 00:33:48,990 It had some negative effects, which is that there's less 698 00:33:48,990 --> 00:33:52,010 time to talk about things like this. 699 00:33:52,010 --> 00:33:55,040 And maybe it feels like there's more pressure to not 700 00:33:55,040 --> 00:33:56,210 wait five seconds. 701 00:33:56,210 --> 00:33:58,080 So it has maybe subtle pressures in the wrong 702 00:33:58,080 --> 00:34:02,000 direction, which maybe could be mitigated by planning. 703 00:34:02,000 --> 00:34:05,570 But it had a really great advantage, which is that it's 704 00:34:05,570 --> 00:34:06,820 this figure. 705 00:34:11,760 --> 00:34:14,170 So if there's some idea you want to teach, and the idea 706 00:34:14,170 --> 00:34:16,239 you wanted to teach is simple harmonic motion. 707 00:34:16,239 --> 00:34:21,560 He called it Simple Harmonic Oscillation, SHM is the 708 00:34:21,560 --> 00:34:24,760 standard jargon in most of the physics books. 709 00:34:24,760 --> 00:34:27,100 If you want to teach that idea, just showing it in one 710 00:34:27,100 --> 00:34:36,050 example is not good enough for the students, because they 711 00:34:36,050 --> 00:34:38,530 can't separate the example from the idea. 712 00:34:38,530 --> 00:34:40,719 It's just one big morass, and they can't draw 713 00:34:40,719 --> 00:34:42,000 this dividing line. 714 00:34:42,000 --> 00:34:43,840 So you have to give them another example. 715 00:34:43,840 --> 00:34:49,469 But if you give them a second spring example, then it's 716 00:34:49,469 --> 00:34:50,540 still too hard. 717 00:34:50,540 --> 00:34:54,560 Suppose you do this and yet another spring example. 718 00:34:54,560 --> 00:35:00,790 Well, the problem is it still the overlap here is too big. 719 00:35:00,790 --> 00:35:03,840 So you need an example that illustrates the core idea but 720 00:35:03,840 --> 00:35:05,200 is quite different. 721 00:35:05,200 --> 00:35:07,460 And the pendulum falls into that pretty well. 722 00:35:20,240 --> 00:35:23,180 It's different, in that-- 723 00:35:23,180 --> 00:35:26,320 and the order was correct too-- he first did the spring, 724 00:35:26,320 --> 00:35:29,360 because the spring really is pure simple harmonic motion. 725 00:35:29,360 --> 00:35:31,030 The pendulum isn't, but you have to 726 00:35:31,030 --> 00:35:33,410 approximate to get it there. 727 00:35:33,410 --> 00:35:37,010 So it shows how you get to simple harmonic motion, 728 00:35:37,010 --> 00:35:38,130 because you've seen it now. 729 00:35:38,130 --> 00:35:40,940 And so the piece you're getting to is the common thing 730 00:35:40,940 --> 00:35:42,790 between the two examples. 731 00:35:42,790 --> 00:35:46,080 And furthermore, it's different enough that you can 732 00:35:46,080 --> 00:35:47,980 see what's common and what's not. 733 00:35:47,980 --> 00:35:50,350 What's common is the structure of the equation. 734 00:35:50,350 --> 00:35:51,690 The structure of the equation is-- 735 00:35:59,480 --> 00:36:01,020 So that's common. 736 00:36:01,020 --> 00:36:05,240 And so you have a really particular example here of 737 00:36:05,240 --> 00:36:09,080 inducing the core idea, which is if you just did simple 738 00:36:09,080 --> 00:36:12,450 harmonic motion with the example of a spring, students 739 00:36:12,450 --> 00:36:14,555 may think simple harmonic motion is this. 740 00:36:17,940 --> 00:36:20,160 They think whenever you have k/m you have 741 00:36:20,160 --> 00:36:21,270 simple harmonic motion. 742 00:36:21,270 --> 00:36:23,050 Whenever you don't have k/m, you don't have 743 00:36:23,050 --> 00:36:24,200 simple harmonic motion. 744 00:36:24,200 --> 00:36:26,130 They may think that actually it depends on 745 00:36:26,130 --> 00:36:27,450 exactly what's here. 746 00:36:27,450 --> 00:36:29,980 But because the second example has something completely 747 00:36:29,980 --> 00:36:30,590 different-- 748 00:36:30,590 --> 00:36:38,550 The second example, the pendulum had g/l after 749 00:36:38,550 --> 00:36:39,780 approximating it. 750 00:36:39,780 --> 00:36:43,210 You get the same structure of the equation, but a new 751 00:36:43,210 --> 00:36:44,500 physical phenomena. 752 00:36:44,500 --> 00:36:46,720 And it shares the common feature of 753 00:36:46,720 --> 00:36:47,760 simple harmonic motion. 754 00:36:47,760 --> 00:36:52,640 So it's a really excellent way of bringing out this idea and 755 00:36:52,640 --> 00:36:55,310 borrowing most of the derivation that he did before. 756 00:36:55,310 --> 00:36:59,740 For example, he didn't have to do resolve this equation with 757 00:36:59,740 --> 00:37:00,980 these new parameters. 758 00:37:00,980 --> 00:37:04,170 Once he'd solved this equation, all he had to do is 759 00:37:04,170 --> 00:37:06,220 substitute this into the solution and get the new 760 00:37:06,220 --> 00:37:07,470 solution instantly. 761 00:37:09,990 --> 00:37:10,840 OK? 762 00:37:10,840 --> 00:37:12,640 Yes. 763 00:37:12,640 --> 00:37:14,890 AUDIENCE: He created emphasis by using both gestures and 764 00:37:14,890 --> 00:37:17,570 also modulating his pace and pitch. 765 00:37:17,570 --> 00:37:20,070 PROFESSOR: OK. 766 00:37:20,070 --> 00:37:21,880 I'll try to squeeze it in here. 767 00:37:21,880 --> 00:37:24,460 So he modulated his pace and pitch, and his 768 00:37:24,460 --> 00:37:27,350 gestures were very bold. 769 00:37:27,350 --> 00:37:28,410 He talked about the spring. 770 00:37:28,410 --> 00:37:29,245 He stretched the spring. 771 00:37:29,245 --> 00:37:32,880 He actually almost broke the spring. 772 00:37:32,880 --> 00:37:36,750 Whenever he was describing something, you could feel him 773 00:37:36,750 --> 00:37:38,450 feeling it in his own body. 774 00:37:45,760 --> 00:37:48,145 His gestures were bold, and his pace was varied. 775 00:37:55,080 --> 00:37:55,340 OK. 776 00:37:55,340 --> 00:37:56,590 How does that help? 777 00:37:59,320 --> 00:38:01,215 Yeah. 778 00:38:01,215 --> 00:38:02,700 AUDIENCE: Conveys enthusiasm. 779 00:38:02,700 --> 00:38:02,940 PROFESSOR: Yeah. 780 00:38:02,940 --> 00:38:03,600 It's exciting. 781 00:38:03,600 --> 00:38:05,280 It conveys enthusiasm. 782 00:38:05,280 --> 00:38:07,750 It punctuates. 783 00:38:07,750 --> 00:38:09,150 There are several languages, I think, which 784 00:38:09,150 --> 00:38:11,500 have no vowels and-- 785 00:38:11,500 --> 00:38:12,690 Not no spaces. 786 00:38:12,690 --> 00:38:14,380 Well, German approximately has no spaces. 787 00:38:14,380 --> 00:38:15,480 That's not quite true. 788 00:38:15,480 --> 00:38:19,250 But that don't have vowels or punctuation. 789 00:38:19,250 --> 00:38:21,070 In the old days, for example, there was no punctuation. 790 00:38:21,070 --> 00:38:23,450 People just ran all the words one after another. 791 00:38:23,450 --> 00:38:25,780 You didn't put a period at the end of sentences. 792 00:38:25,780 --> 00:38:29,320 Without punctuation, you have to work really hard to figure 793 00:38:29,320 --> 00:38:32,200 out what are the units of thought. 794 00:38:32,200 --> 00:38:37,010 So by varying your pace and pitch, you convey enthusiasm. 795 00:38:42,750 --> 00:38:44,455 You convey enthusiasm and structure. 796 00:38:48,450 --> 00:38:53,790 So the pieces that are more important get more importance, 797 00:38:53,790 --> 00:38:55,490 because they're emphasized accordingly. 798 00:38:59,070 --> 00:39:01,390 That's actually fundamentally important in writing. 799 00:39:01,390 --> 00:39:04,770 I don't know if you know the following recipe, but this is 800 00:39:04,770 --> 00:39:09,130 the first-order term in good clear writing. 801 00:39:09,130 --> 00:39:12,770 Let's call it not fiction writing but expository writing 802 00:39:12,770 --> 00:39:14,000 is the right word. 803 00:39:14,000 --> 00:39:17,960 The first-order term in punctuating writing and giving 804 00:39:17,960 --> 00:39:19,590 structured to your writing is this. 805 00:39:28,910 --> 00:39:32,850 A sentence starts with old information that links to 806 00:39:32,850 --> 00:39:35,430 something before. 807 00:39:35,430 --> 00:39:37,280 It continues to-- 808 00:39:47,940 --> 00:39:49,940 This is how the sentence ends. 809 00:39:49,940 --> 00:39:54,520 Whatever you put at the end of the sentence, readers expect 810 00:39:54,520 --> 00:39:57,140 that to be the thing that you want to emphasize. 811 00:39:57,140 --> 00:39:58,500 That's the new information. 812 00:39:58,500 --> 00:40:00,910 There's maybe a fair amount of new information in the 813 00:40:00,910 --> 00:40:03,680 sentence, but this is the new interesting information. 814 00:40:03,680 --> 00:40:06,500 This is what readers assume has emphasis. 815 00:40:06,500 --> 00:40:09,050 And in the beginning of a sentence, they look for things 816 00:40:09,050 --> 00:40:10,890 that connect to what has already happened. 817 00:40:10,890 --> 00:40:13,700 It could connect to the last emphasized thing in the last 818 00:40:13,700 --> 00:40:16,660 sentence, the subject of the last sentence, the thing that 819 00:40:16,660 --> 00:40:18,850 was the topic, or the topic of the paragraph. 820 00:40:18,850 --> 00:40:21,630 It somehow links to stuff before, and then you're going 821 00:40:21,630 --> 00:40:23,530 to say something new about it. 822 00:40:23,530 --> 00:40:27,260 So if you don't use that order, it gets very confusing 823 00:40:27,260 --> 00:40:30,150 for readers, because they expect this to be emphasized, 824 00:40:30,150 --> 00:40:32,190 but you're mentally emphasizing something else, 825 00:40:32,190 --> 00:40:34,630 and then they have to redo their expectations each time. 826 00:40:34,630 --> 00:40:37,790 So punctuation, the period actually is a way of saying, 827 00:40:37,790 --> 00:40:39,830 here came the most important information. 828 00:40:39,830 --> 00:40:42,400 And if you follow that structure, you'll tap into 829 00:40:42,400 --> 00:40:45,450 much better how your readers understand. 830 00:40:45,450 --> 00:40:49,290 If you want to know more about that, I'll put some references 831 00:40:49,290 --> 00:40:50,540 on the website. 832 00:40:57,600 --> 00:41:01,475 This was partly developed by Joseph Williams, a linguistic 833 00:41:01,475 --> 00:41:04,790 at the University of Chicago and George Gopen, who's an 834 00:41:04,790 --> 00:41:08,400 English professor and law professor at Duke. 835 00:41:08,400 --> 00:41:11,170 And he's written a really interesting article called, 836 00:41:11,170 --> 00:41:12,460 him and Judith Swan-- it's called "The 837 00:41:12,460 --> 00:41:13,820 Science of Science Writing"-- 838 00:41:13,820 --> 00:41:16,930 where he gives a whole bunch of examples of restructuring 839 00:41:16,930 --> 00:41:19,680 prose along these lines and how much clearer it becomes. 840 00:41:19,680 --> 00:41:25,560 And he's written two books, actually, one on teaching this 841 00:41:25,560 --> 00:41:28,990 approach to writing and one on doing it yourself. 842 00:41:28,990 --> 00:41:31,760 It's a textbook for such a class. 843 00:41:31,760 --> 00:41:33,290 One's called The Sense of Structure. 844 00:41:33,290 --> 00:41:36,580 I forget whether that's the teaching book or the textbook. 845 00:41:36,580 --> 00:41:39,670 But I'll put both titles on the website So I highly 846 00:41:39,670 --> 00:41:40,690 recommend that. 847 00:41:40,690 --> 00:41:44,360 And what you'll see from this is the huge importance of 848 00:41:44,360 --> 00:41:45,610 punctuation. 849 00:41:48,080 --> 00:41:50,070 And here, it's the same thing. 850 00:41:50,070 --> 00:41:53,340 By varying the pitch, by giving periods, semicolons, 851 00:41:53,340 --> 00:41:57,080 and commas in the lecture, even though you can't say, OK, 852 00:41:57,080 --> 00:41:58,390 here's the period. 853 00:41:58,390 --> 00:42:01,600 You don't say that, but you do it by varying your pitch and 854 00:42:01,600 --> 00:42:03,040 your volume and your tone. 855 00:42:03,040 --> 00:42:04,110 You give structure. 856 00:42:04,110 --> 00:42:07,450 And fundamentally important, you also convey enthusiasm. 857 00:42:07,450 --> 00:42:07,760 Yes. 858 00:42:07,760 --> 00:42:10,410 AUDIENCE: On the other hand, I think in that lecture he 859 00:42:10,410 --> 00:42:12,020 offered [INAUDIBLE] 860 00:42:12,020 --> 00:42:12,200 [LOUDLY] 861 00:42:12,200 --> 00:42:14,980 he always speaks like this, [NORMAL VOLUME] 862 00:42:14,980 --> 00:42:16,570 which intimidated students a bit. 863 00:42:16,570 --> 00:42:17,750 PROFESSOR: Yeah. 864 00:42:17,750 --> 00:42:18,470 Yeah. 865 00:42:18,470 --> 00:42:20,380 He maybe does it too much. 866 00:42:20,380 --> 00:42:23,240 In fact, he doesn't vary enough. 867 00:42:23,240 --> 00:42:27,720 It's sort of like the radio in Spinal Tap. 868 00:42:27,720 --> 00:42:31,410 It goes to 11, and it starts at 10. 869 00:42:31,410 --> 00:42:32,910 Because it's always loud. 870 00:42:32,910 --> 00:42:35,040 The amplifier's always loud. 871 00:42:35,040 --> 00:42:36,620 Yeah, I think he could actually have 872 00:42:36,620 --> 00:42:38,690 more dynamic range. 873 00:42:38,690 --> 00:42:40,250 So let's see. 874 00:42:40,250 --> 00:42:41,500 More-- 875 00:42:48,400 --> 00:42:49,350 In his defense-- 876 00:42:49,350 --> 00:42:50,630 Oh, yes. 877 00:42:50,630 --> 00:42:51,086 Go ahead. 878 00:42:51,086 --> 00:42:52,130 AUDIENCE: Finish your thought. 879 00:42:52,130 --> 00:42:53,000 PROFESSOR: OK. 880 00:42:53,000 --> 00:42:57,680 In his defense, you could say, well, when do you want to be 881 00:42:57,680 --> 00:42:58,690 really quiet? 882 00:42:58,690 --> 00:42:59,520 Well, that's when you're doing 883 00:42:59,520 --> 00:43:01,280 something that's less important. 884 00:43:01,280 --> 00:43:03,730 And he's actually such a good lecturer that he planned the 885 00:43:03,730 --> 00:43:04,860 lecture, I would say, quite well. 886 00:43:04,860 --> 00:43:07,890 He took out all the stuff that normally you would find in a 887 00:43:07,890 --> 00:43:09,980 lecture on this that's kind of dull. 888 00:43:09,980 --> 00:43:13,090 For example, one thing that people do that's really kind 889 00:43:13,090 --> 00:43:17,710 of dull is they may derive the sinusoid as a solution. 890 00:43:17,710 --> 00:43:18,960 And how did he derive the sinusoid? 891 00:43:23,400 --> 00:43:26,180 Spray paint. 892 00:43:26,180 --> 00:43:28,200 They did an experiment. 893 00:43:28,200 --> 00:43:29,170 He made it visible. 894 00:43:29,170 --> 00:43:33,170 He had a spring oscillating up and down with spray paint, so 895 00:43:33,170 --> 00:43:35,340 it was spraying on a big piece of paper. 896 00:43:35,340 --> 00:43:38,300 And then he pulled the piece of paper that way. 897 00:43:38,300 --> 00:43:41,450 So as the spring oscillated up and down and sprayed on the 898 00:43:41,450 --> 00:43:44,700 sheet of paper, it made a track, which you could see 899 00:43:44,700 --> 00:43:45,500 developing. 900 00:43:45,500 --> 00:43:46,850 And then he just showed the class. 901 00:43:46,850 --> 00:43:47,860 He said, what does this look like? 902 00:43:47,860 --> 00:43:49,310 And they said, oh, it looks like a sinusoid. 903 00:43:49,310 --> 00:43:50,450 There you go. 904 00:43:50,450 --> 00:43:55,890 Now you skipped a whole bunch of painful math, otherwise, to 905 00:43:55,890 --> 00:43:57,030 make the guess. 906 00:43:57,030 --> 00:44:01,520 And so either you guess it, or you do a bunch of derivation. 907 00:44:01,520 --> 00:44:03,670 He avoided both of those problems by actually just 908 00:44:03,670 --> 00:44:05,690 having the students see for themselves. 909 00:44:05,690 --> 00:44:07,452 In fact, he used the word see. 910 00:44:07,452 --> 00:44:09,390 I want to make you see what it is. 911 00:44:09,390 --> 00:44:10,600 So he got that. 912 00:44:10,600 --> 00:44:14,560 He's taken out a lot of stuff where you would normally just 913 00:44:14,560 --> 00:44:15,900 try to pretend you weren't doing and 914 00:44:15,900 --> 00:44:17,380 speak really quietly. 915 00:44:17,380 --> 00:44:19,390 So that's maybe one explanation for why his 916 00:44:19,390 --> 00:44:22,510 dynamic range wasn't as big as it should be. 917 00:44:22,510 --> 00:44:26,960 But yeah, I think, generally, the point is right that he's 918 00:44:26,960 --> 00:44:31,410 so forceful and loud that it would be better if he just had 919 00:44:31,410 --> 00:44:32,720 a twice as much range. 920 00:44:32,720 --> 00:44:33,980 AUDIENCE: Just an extra comment. 921 00:44:33,980 --> 00:44:34,467 PROFESSOR: Yeah. 922 00:44:34,467 --> 00:44:36,415 AUDIENCE: And this maybe be necessary in the old days when 923 00:44:36,415 --> 00:44:37,876 you don't have microphones in lectures. 924 00:44:37,876 --> 00:44:40,554 But when you have microphones, you can speak colloquially but 925 00:44:40,554 --> 00:44:43,240 still very clear to the students. 926 00:44:43,240 --> 00:44:43,500 PROFESSOR: That's true. 927 00:44:43,500 --> 00:44:44,275 You have amplification. 928 00:44:44,275 --> 00:44:44,580 Yeah. 929 00:44:44,580 --> 00:44:49,410 And he did have a microphone, because he was being taped. 930 00:44:49,410 --> 00:44:50,300 But you're right. 931 00:44:50,300 --> 00:44:53,010 The habits of thought in presentation come from when we 932 00:44:53,010 --> 00:44:54,450 didn't have microphones. 933 00:44:54,450 --> 00:44:56,282 Yes. 934 00:44:56,282 --> 00:44:58,999 AUDIENCE: The one thing I would change is at the very 935 00:44:58,999 --> 00:45:00,728 beginning he was talking about the test results. 936 00:45:00,728 --> 00:45:01,222 PROFESSOR: Yeah. 937 00:45:01,222 --> 00:45:04,680 AUDIENCE: And he said the test results were better, on 938 00:45:04,680 --> 00:45:06,656 average, than in previous years. 939 00:45:06,656 --> 00:45:10,361 And he said, oh, you're either a smart class or the 940 00:45:10,361 --> 00:45:13,078 test was too easy. 941 00:45:13,078 --> 00:45:16,900 Just generally, calling the students smart seems pretty 942 00:45:16,900 --> 00:45:19,214 alienating for the students who did poorly. 943 00:45:19,214 --> 00:45:21,410 And then even the kids who did well, there's pretty good 944 00:45:21,410 --> 00:45:23,290 evidence that saying "you're smart" rather than "you're 945 00:45:23,290 --> 00:45:27,530 working hard", the latter's much more effective. 946 00:45:27,530 --> 00:45:27,670 PROFESSOR: Right. 947 00:45:27,670 --> 00:45:29,690 That's a really good point. 948 00:45:29,690 --> 00:45:33,560 Yeah, the test results discussion at the beginning. 949 00:45:33,560 --> 00:45:39,470 I always knew this lecture was a classic one, and this is the 950 00:45:39,470 --> 00:45:41,780 first time I watched it straight through, rather than 951 00:45:41,780 --> 00:45:43,930 just watching the sort of demonstration parts and the 952 00:45:43,930 --> 00:45:45,500 famous parts. 953 00:45:45,500 --> 00:45:48,950 And so it started off with this discussion about test 954 00:45:48,950 --> 00:45:56,730 results where he says all kinds of interesting things. 955 00:45:56,730 --> 00:45:59,280 "You did very well on your first exam." That's word one 956 00:45:59,280 --> 00:46:00,770 in the lecture. 957 00:46:00,770 --> 00:46:05,830 "I was hoping for an average of about 75." So hoping, 958 00:46:05,830 --> 00:46:08,420 that's not a word I would have used. 959 00:46:08,420 --> 00:46:10,070 I would hope for an average of 100. 960 00:46:10,070 --> 00:46:10,990 That's my hope. 961 00:46:10,990 --> 00:46:14,240 Maybe not what I expect, but my hope is 100. 962 00:46:14,240 --> 00:46:17,590 So by saying hope, he's saying, actually, it would be 963 00:46:17,590 --> 00:46:20,880 good if people got a lot of stuff wrong, like I'm hoping 964 00:46:20,880 --> 00:46:22,890 that people get 25% wrong. 965 00:46:22,890 --> 00:46:25,170 That could be interpreted as hoping that the 966 00:46:25,170 --> 00:46:26,900 students don't do great. 967 00:46:26,900 --> 00:46:29,020 But then, on the other hand, the class average was 89. 968 00:46:29,020 --> 00:46:29,230 OK. 969 00:46:29,230 --> 00:46:30,640 So that's good news. 970 00:46:30,640 --> 00:46:34,300 Now, as you say, he says, "either you are very smart, 971 00:46:34,300 --> 00:46:37,655 this is an exceptional class, or the exam was too easy." And 972 00:46:37,655 --> 00:46:40,140 he eventually concludes, no, the exam was taken by the 973 00:46:40,140 --> 00:46:42,110 instructor, so you guys are smart class. 974 00:46:42,110 --> 00:46:47,510 But even that he takes away by saying, "but time will tell 975 00:46:47,510 --> 00:46:49,590 whether you are indeed exceptionally smart or whether 976 00:46:49,590 --> 00:46:51,300 the exam was too easy." 977 00:46:51,300 --> 00:46:53,970 So even the good news is tempered and 978 00:46:53,970 --> 00:46:55,190 taken partly back. 979 00:46:55,190 --> 00:46:57,440 And then even the good news itself, as you point out 980 00:46:57,440 --> 00:47:00,430 correctly, is not necessarily good for helping 981 00:47:00,430 --> 00:47:01,890 the students learn. 982 00:47:01,890 --> 00:47:04,530 So there's very interesting studies-- 983 00:47:04,530 --> 00:47:05,700 I wish I could remember the name. 984 00:47:05,700 --> 00:47:08,900 She's a psychology professor at Stanford, and she's done 985 00:47:08,900 --> 00:47:13,190 studies with kids. 986 00:47:13,190 --> 00:47:20,000 What you do is you have the kids do a problem, and then 987 00:47:20,000 --> 00:47:24,510 you tell them either that they worked hard at it or that they 988 00:47:24,510 --> 00:47:25,850 were very smart. 989 00:47:25,850 --> 00:47:28,650 That's why they solved it. 990 00:47:28,650 --> 00:47:32,480 You tell Group A that, oh, yeah, you worked 991 00:47:32,480 --> 00:47:33,640 really hard at it. 992 00:47:33,640 --> 00:47:34,430 That's why you solved it. 993 00:47:34,430 --> 00:47:36,315 Group B, you say, oh, yeah, you solved it. 994 00:47:36,315 --> 00:47:37,650 You must be really smart. 995 00:47:37,650 --> 00:47:39,930 And then you see what kind of problems they try later. 996 00:47:44,930 --> 00:47:47,640 Let's do Group B first, who are told you did it because 997 00:47:47,640 --> 00:47:49,710 you were smart. 998 00:47:49,710 --> 00:47:50,490 Later-- 999 00:47:50,490 --> 00:47:53,220 this is making an extreme of it, but this is the trend-- 1000 00:47:53,220 --> 00:47:55,850 they don't want to solve hard problems. 1001 00:47:55,850 --> 00:47:58,220 Because the only thing you can get out of solving a hard 1002 00:47:58,220 --> 00:48:00,280 problem is you don't solve it, which then proves that you're 1003 00:48:00,280 --> 00:48:02,490 actually not as smart as people though. 1004 00:48:02,490 --> 00:48:04,560 So they want to solve easy problems. 1005 00:48:04,560 --> 00:48:07,100 The group that was told, oh, yeah, you did that because you 1006 00:48:07,100 --> 00:48:10,420 worked really hard, they enjoy solving the problems. 1007 00:48:10,420 --> 00:48:13,010 And they want to solve hard problems that they can't 1008 00:48:13,010 --> 00:48:14,720 necessarily solve, because they can work on them. 1009 00:48:14,720 --> 00:48:17,720 And some of them even say things like, oh, I love it 1010 00:48:17,720 --> 00:48:21,060 when a problem's hard, which is a completely different 1011 00:48:21,060 --> 00:48:23,130 attitude than the attitude of the people who are like, oh, I 1012 00:48:23,130 --> 00:48:23,980 don't want to try anything. 1013 00:48:23,980 --> 00:48:26,440 Because I might fail, and then the truth about 1014 00:48:26,440 --> 00:48:28,560 me will come out. 1015 00:48:28,560 --> 00:48:31,240 By making comments about people's intrinsic 1016 00:48:31,240 --> 00:48:33,390 characteristics-- 1017 00:48:33,390 --> 00:48:35,880 I made distinction earlier between intrinsic motivation 1018 00:48:35,880 --> 00:48:38,800 and extrinsic motivation and how you really want to use 1019 00:48:38,800 --> 00:48:40,580 intrinsic motivation. 1020 00:48:40,580 --> 00:48:44,320 But there's the flip one, which is you don't want to 1021 00:48:44,320 --> 00:48:47,470 make intrinsic comments about people, because that's very 1022 00:48:47,470 --> 00:48:50,140 hard to change and very fixed. 1023 00:48:50,140 --> 00:48:52,330 And that's what people are doing way too much of. 1024 00:48:52,330 --> 00:48:54,670 So whenever people can't solve things, it's because you 1025 00:48:54,670 --> 00:48:57,185 didn't work hard enough, the conditions weren't right, you 1026 00:48:57,185 --> 00:48:59,300 can call it making excuses, but it isn't. 1027 00:48:59,300 --> 00:49:01,630 It's an optimistic way of looking at the world. 1028 00:49:01,630 --> 00:49:04,910 And it's that optimism that people learn when they have 1029 00:49:04,910 --> 00:49:07,420 control over the things that lead to problem-solving 1030 00:49:07,420 --> 00:49:09,360 successfully or not. 1031 00:49:09,360 --> 00:49:12,660 Yeah, I thought the opening was actually very bad in terms 1032 00:49:12,660 --> 00:49:17,050 of that and actually set a kind of competitive, 1033 00:49:17,050 --> 00:49:22,220 hierarchical tone, which I would have definitely avoided. 1034 00:49:22,220 --> 00:49:23,330 Other comments? 1035 00:49:23,330 --> 00:49:26,780 Other things you noticed? 1036 00:49:26,780 --> 00:49:27,262 Yeah. 1037 00:49:27,262 --> 00:49:29,190 AUDIENCE: He kind of oozed with 1038 00:49:29,190 --> 00:49:31,118 passion about the subject. 1039 00:49:31,118 --> 00:49:34,492 Usually, [INAUDIBLE] 1040 00:49:34,492 --> 00:49:37,880 5,000, he still seemed amazed that they worked. 1041 00:49:37,880 --> 00:49:39,580 PROFESSOR: Right. 1042 00:49:39,580 --> 00:49:40,710 Right. 1043 00:49:40,710 --> 00:49:44,280 Let me erase this guy. 1044 00:49:44,280 --> 00:49:45,820 Right. 1045 00:49:45,820 --> 00:49:47,150 He's shedding passion. 1046 00:49:47,150 --> 00:49:48,400 He's oozing passion. 1047 00:49:53,800 --> 00:49:56,880 I'm sure he's done the demo many, many times for every 1048 00:49:56,880 --> 00:49:59,320 semester, no doubt. 1049 00:49:59,320 --> 00:50:01,880 Yet he was still so excited. 1050 00:50:01,880 --> 00:50:04,040 For example, the ending, what did he say? 1051 00:50:08,870 --> 00:50:11,480 They did 10 oscillations with Walter Lewin as 1052 00:50:11,480 --> 00:50:13,330 the pendulum bob. 1053 00:50:13,330 --> 00:50:15,200 And then they counted up to 10. 1054 00:50:15,200 --> 00:50:19,870 So then he got to 10t with Walter Lewin, 45.6, plus or 1055 00:50:19,870 --> 00:50:21,090 minus 0.1 seconds. 1056 00:50:21,090 --> 00:50:24,940 And the prediction was 45.7, plus or minus 0.1, so it was 1057 00:50:24,940 --> 00:50:25,680 right on the nose. 1058 00:50:25,680 --> 00:50:28,010 He said, "Physics works, I'm telling you. 1059 00:50:28,010 --> 00:50:32,820 See you Monday." So he ends with enthusiasm. 1060 00:50:32,820 --> 00:50:36,170 He is enthusiasm throughout, all the way through. 1061 00:50:36,170 --> 00:50:38,020 Yeah, it is contagious. 1062 00:50:38,020 --> 00:50:39,880 People did applaud, and I'm sure it wasn't just because it 1063 00:50:39,880 --> 00:50:40,680 was being taped. 1064 00:50:40,680 --> 00:50:46,210 They really were very pleased and amazed at the close 1065 00:50:46,210 --> 00:50:49,360 agreement, even when he changed the pendulum bob from 1066 00:50:49,360 --> 00:50:52,260 just the regular pendulum bob of a few kilograms to Walter 1067 00:50:52,260 --> 00:50:54,320 Lewin of 70 kilograms or-- 1068 00:50:54,320 --> 00:50:56,190 he's probably more-- 1069 00:50:56,190 --> 00:50:58,720 probably 80 kilograms. 1070 00:50:58,720 --> 00:51:03,530 And throughout as well, doing the demonstrations, he was 1071 00:51:03,530 --> 00:51:04,700 also very enthusiastic. 1072 00:51:04,700 --> 00:51:07,820 And even sometimes he got lucky, and he even said so. 1073 00:51:07,820 --> 00:51:11,600 But he said, fantastic agreement between theory and 1074 00:51:11,600 --> 00:51:12,720 experiment. 1075 00:51:12,720 --> 00:51:16,240 Yeah, so the enthusiasm, it transfers. 1076 00:51:16,240 --> 00:51:21,760 And in fact, our system, our brain is actually much better 1077 00:51:21,760 --> 00:51:24,930 at picking up this kind of stuff than it is at picking up 1078 00:51:24,930 --> 00:51:27,560 the Navier-Stokes equation and things like that. 1079 00:51:31,540 --> 00:51:34,062 Let's call it an emotional highway. 1080 00:51:34,062 --> 00:51:35,440 It goes in the emotional highway. 1081 00:51:40,860 --> 00:51:43,390 So I mentioned the experiment that you can do to test this. 1082 00:51:43,390 --> 00:51:46,600 The experiment you do is you just go somewhere and you just 1083 00:51:46,600 --> 00:51:47,850 smile at people. 1084 00:51:50,230 --> 00:51:55,070 And now 30%, 40%, 50% of the class is smiling back already. 1085 00:51:55,070 --> 00:51:56,270 You can't help it. 1086 00:51:56,270 --> 00:51:57,740 Even though you know and I'm telling you 1087 00:51:57,740 --> 00:51:58,450 I'm just doing this-- 1088 00:51:58,450 --> 00:52:00,550 There's nothing actually funny that just happened right now. 1089 00:52:00,550 --> 00:52:02,930 I'm just smiling, just because I'm a nice guy and I'm 1090 00:52:02,930 --> 00:52:05,610 smiling, and I just wanted you to see if the experiment 1091 00:52:05,610 --> 00:52:07,830 works-- you can't help it. 1092 00:52:07,830 --> 00:52:11,290 So that tells you how powerful that emotional highway is. 1093 00:52:11,290 --> 00:52:12,740 It's not just for smiling. 1094 00:52:12,740 --> 00:52:16,600 It's the oozing passion. 1095 00:52:16,600 --> 00:52:19,990 Neurobiologically, that mechanism is starting to be 1096 00:52:19,990 --> 00:52:22,700 understood. 1097 00:52:22,700 --> 00:52:24,000 I'll write the mechanism down. 1098 00:52:32,320 --> 00:52:35,240 We have what are called mirror neurons. 1099 00:52:35,240 --> 00:52:41,240 What mirror neurons do is they recreate the state of mind of 1100 00:52:41,240 --> 00:52:44,140 other people in us. 1101 00:52:44,140 --> 00:52:45,970 So that's why they're called mirror neurons. 1102 00:52:45,970 --> 00:52:47,200 And they're innate. 1103 00:52:47,200 --> 00:52:48,810 It seems that monkeys have them. 1104 00:52:48,810 --> 00:52:49,520 We have them. 1105 00:52:49,520 --> 00:52:50,840 There's nothing you can do about them. 1106 00:52:50,840 --> 00:52:53,850 And they are actually probably the mechanism by which we 1107 00:52:53,850 --> 00:52:55,850 become social creatures and which 1108 00:52:55,850 --> 00:52:57,760 makes us social creatures. 1109 00:52:57,760 --> 00:53:00,360 So if people around us are unhappy, we feel unhappy. 1110 00:53:00,360 --> 00:53:03,200 If people around us are happy, we feel happy. 1111 00:53:03,200 --> 00:53:06,060 And these mirror neurons, their firing tendencies are 1112 00:53:06,060 --> 00:53:09,480 partly set in young childhood. 1113 00:53:09,480 --> 00:53:12,430 So if the people around you are happy in childhood, you'll 1114 00:53:12,430 --> 00:53:14,240 have a much easier time just 1115 00:53:14,240 --> 00:53:15,670 automatically being happy later. 1116 00:53:15,670 --> 00:53:17,960 And if the people around you in childhood are really 1117 00:53:17,960 --> 00:53:20,660 unhappy and your childhood's unhappy, you have to work much 1118 00:53:20,660 --> 00:53:22,610 harder later to overcome that. 1119 00:53:22,610 --> 00:53:26,080 So that's the importance of childhood and child 1120 00:53:26,080 --> 00:53:26,870 upbringing. 1121 00:53:26,870 --> 00:53:30,620 But now these are there, and your students all have them, 1122 00:53:30,620 --> 00:53:31,470 being people. 1123 00:53:31,470 --> 00:53:36,170 So how you act and how you perform is going to affect 1124 00:53:36,170 --> 00:53:40,920 them much more strongly than any equation you say. 1125 00:53:40,920 --> 00:53:43,820 It's fundamentally important, again. 1126 00:53:43,820 --> 00:53:44,160 OK. 1127 00:53:44,160 --> 00:53:45,410 Any other points? 1128 00:53:48,440 --> 00:53:48,920 Yes. 1129 00:53:48,920 --> 00:53:49,400 AUDIENCE: Yeah. 1130 00:53:49,400 --> 00:53:53,482 I was thinking about the use of the spray-- 1131 00:53:53,482 --> 00:53:54,650 PROFESSOR: The spray paint can? 1132 00:53:54,650 --> 00:53:54,920 Yeah. 1133 00:53:54,920 --> 00:53:56,327 AUDIENCE: Yes. 1134 00:53:56,327 --> 00:53:58,203 And it wasn't until now that I actually 1135 00:53:58,203 --> 00:53:59,610 understood why he did that. 1136 00:53:59,610 --> 00:54:04,746 Because when I saw it, I was sort of thinking, why is he 1137 00:54:04,746 --> 00:54:05,698 doing that? 1138 00:54:05,698 --> 00:54:08,078 Or if he pulled the lever faster, it's 1139 00:54:08,078 --> 00:54:11,410 going to look the same. 1140 00:54:11,410 --> 00:54:12,990 I didn't get it at all. 1141 00:54:12,990 --> 00:54:16,802 And now I see it was to guess the solution [INAUDIBLE]. 1142 00:54:16,802 --> 00:54:23,185 And then I'm thinking, when I was taught the harmonic 1143 00:54:23,185 --> 00:54:26,622 oscillator for the first time, that's an opportunity the 1144 00:54:26,622 --> 00:54:29,904 professor used to actually teach how to solve, OK, this 1145 00:54:29,904 --> 00:54:32,162 is the differential equation, and this is the 1146 00:54:32,162 --> 00:54:32,808 solution for it. 1147 00:54:32,808 --> 00:54:34,750 And now you know for the rest of your life. 1148 00:54:34,750 --> 00:54:38,810 Because solving a differential equation by [INAUDIBLE], 1149 00:54:38,810 --> 00:54:41,640 you're not always going to have an experiment to solve-- 1150 00:54:41,640 --> 00:54:42,280 PROFESSOR: To show it. 1151 00:54:42,280 --> 00:54:44,730 AUDIENCE: Right. 1152 00:54:44,730 --> 00:54:45,730 It's kind of cool. 1153 00:54:45,730 --> 00:54:48,730 But I'm not quite sure what's the purpose. 1154 00:54:48,730 --> 00:54:49,070 PROFESSOR: OK. 1155 00:54:49,070 --> 00:54:51,900 So what's the purpose? 1156 00:54:51,900 --> 00:54:57,510 It could go here or here, the spray paint example. 1157 00:54:57,510 --> 00:55:02,250 The normal way it's done is that you either just guess it 1158 00:55:02,250 --> 00:55:05,640 outright, you say, well, we've seen that equation before-- 1159 00:55:05,640 --> 00:55:08,220 we being the royal we-- the instructor's seen the equation 1160 00:55:08,220 --> 00:55:11,180 before and says, use the sinusoid. 1161 00:55:11,180 --> 00:55:12,790 The students have never seen it before and just have to 1162 00:55:12,790 --> 00:55:14,350 take it on faith. 1163 00:55:14,350 --> 00:55:16,710 Then you put in the sinusoid, and then you show that it 1164 00:55:16,710 --> 00:55:18,640 solves the equation. 1165 00:55:18,640 --> 00:55:22,370 The other way you do it is you separate the equation. 1166 00:55:22,370 --> 00:55:24,270 There's many techniques for solving that equation. 1167 00:55:24,270 --> 00:55:29,330 One is you write it in terms of operators and factor the 1168 00:55:29,330 --> 00:55:33,180 operators, but the freshman aren't really ready for that. 1169 00:55:33,180 --> 00:55:34,200 So you can't really do that. 1170 00:55:34,200 --> 00:55:37,440 You're basically reduced to guessing, at least in the 1171 00:55:37,440 --> 00:55:39,060 American curriculum. 1172 00:55:39,060 --> 00:55:41,960 Now what he's done is he's done an improvement on that. 1173 00:55:41,960 --> 00:55:45,950 Instead of saying just by bold assertion, just outright 1174 00:55:45,950 --> 00:55:49,470 authority saying, please guess this, he's saying, look, this 1175 00:55:49,470 --> 00:55:50,210 is what it did. 1176 00:55:50,210 --> 00:55:51,690 What do you think it is? 1177 00:55:51,690 --> 00:55:53,450 And then the students say, oh, it's a sinusoid. 1178 00:55:53,450 --> 00:55:54,740 He says, OK, good. 1179 00:55:54,740 --> 00:55:56,810 That justifies the guess, basically, that I was going to 1180 00:55:56,810 --> 00:55:57,950 make anyway. 1181 00:55:57,950 --> 00:56:00,980 So it improves on the standard method of guessing and just 1182 00:56:00,980 --> 00:56:01,680 plugging in. 1183 00:56:01,680 --> 00:56:02,610 But you're right. 1184 00:56:02,610 --> 00:56:04,130 Not always can you do that. 1185 00:56:04,130 --> 00:56:07,080 So maybe the thing I would have done is, if I were him, I 1186 00:56:07,080 --> 00:56:10,630 would have said, ah, this is going to avoid us just either 1187 00:56:10,630 --> 00:56:14,200 guessing the solution or doing a whole big, long calculation. 1188 00:56:14,200 --> 00:56:20,390 And he does say that elsewhere when he talks about the zoo, 1189 00:56:20,390 --> 00:56:22,620 when he wrote down the differential equations for the 1190 00:56:22,620 --> 00:56:24,850 x motion and the y motion. 1191 00:56:24,850 --> 00:56:27,990 He said, oh, that has a coupled nonlinear equation. 1192 00:56:27,990 --> 00:56:28,395 It's hopeless. 1193 00:56:28,395 --> 00:56:32,000 It looks like a zoo, and it is a zoo. 1194 00:56:32,000 --> 00:56:33,930 So then he approximated it. 1195 00:56:33,930 --> 00:56:36,310 He was quite good at saying, look, there's some things you 1196 00:56:36,310 --> 00:56:37,660 just don't want to do. 1197 00:56:37,660 --> 00:56:38,920 And this would have been, I think, 1198 00:56:38,920 --> 00:56:40,130 another spot to do that. 1199 00:56:40,130 --> 00:56:42,600 He could have explained why he was going to do the 1200 00:56:42,600 --> 00:56:43,850 experiment. 1201 00:56:54,640 --> 00:56:55,080 OK. 1202 00:56:55,080 --> 00:57:00,820 Just one other point, I think, that wasn't mentioned so far. 1203 00:57:00,820 --> 00:57:02,880 Oh, yeah. 1204 00:57:02,880 --> 00:57:07,850 Yeah, he never erases what he's using. 1205 00:57:07,850 --> 00:57:10,560 We'll talk about that more the next time when we talk about 1206 00:57:10,560 --> 00:57:12,190 using chalk and slides. 1207 00:57:12,190 --> 00:57:15,360 If you notice, he never erased anything he needed. 1208 00:57:15,360 --> 00:57:17,930 Now you could just call that chance. 1209 00:57:17,930 --> 00:57:19,990 So an example of when he had stuff that 1210 00:57:19,990 --> 00:57:21,890 he was using before. 1211 00:57:21,890 --> 00:57:35,420 He had the differential equation, and then that was 1212 00:57:35,420 --> 00:57:36,850 way up on some board. 1213 00:57:36,850 --> 00:57:39,600 And then later, after doing the experiment with the spray 1214 00:57:39,600 --> 00:57:41,912 paint, he came to x equals-- 1215 00:57:48,300 --> 00:57:52,850 So now he had to calculate x and x dot, the derivative, and 1216 00:57:52,850 --> 00:57:54,840 x double dot and then put it in. 1217 00:57:54,840 --> 00:57:57,380 Well, as he was doing that, fortunately this equation was 1218 00:57:57,380 --> 00:57:58,660 still there the whole time. 1219 00:57:58,660 --> 00:57:59,940 It was just high up. 1220 00:57:59,940 --> 00:58:02,560 So he never erased anything he needed later. 1221 00:58:02,560 --> 00:58:03,960 And I was watching pretty carefully 1222 00:58:03,960 --> 00:58:05,040 through the whole lecture. 1223 00:58:05,040 --> 00:58:07,490 I think there was no time when that had happened. 1224 00:58:07,490 --> 00:58:10,100 And you could call that chance. 1225 00:58:10,100 --> 00:58:12,130 Maybe if it happened once it would just be chance. 1226 00:58:12,130 --> 00:58:14,270 But it's actually preparation. 1227 00:58:14,270 --> 00:58:16,230 So that's part of lecture preparation. 1228 00:58:16,230 --> 00:58:17,460 What am I going to need? 1229 00:58:17,460 --> 00:58:22,350 And how do I make sure that it's still visible? 1230 00:58:22,350 --> 00:58:23,370 Or you can write it again. 1231 00:58:23,370 --> 00:58:24,330 That's also fine. 1232 00:58:24,330 --> 00:58:26,445 But how do I make it so that students don't have to 1233 00:58:26,445 --> 00:58:28,030 remember it, flip back in their notes? 1234 00:58:28,030 --> 00:58:30,220 Because to them, this is a new equation. 1235 00:58:30,220 --> 00:58:33,580 It's not just the equivalent of one pawn, one chunk. 1236 00:58:33,580 --> 00:58:35,660 It's six or seven chunks. 1237 00:58:35,660 --> 00:58:37,430 So you don't want to fill up their short-term memory trying 1238 00:58:37,430 --> 00:58:38,260 to remember that. 1239 00:58:38,260 --> 00:58:39,890 You want it visible somewhere. 1240 00:58:39,890 --> 00:58:41,625 And that was also planning. 1241 00:58:45,850 --> 00:58:46,105 Yes. 1242 00:58:46,105 --> 00:58:49,120 AUDIENCE: He calls tension a force. 1243 00:58:49,120 --> 00:58:50,710 PROFESSOR: Yeah, he did call tension a force. 1244 00:58:50,710 --> 00:58:53,680 I was most upset about that. 1245 00:58:53,680 --> 00:59:03,540 That is the standard way it's done, and all the physics 1246 00:59:03,540 --> 00:59:04,510 courses I took as an undergraduate 1247 00:59:04,510 --> 00:59:05,560 did the same thing. 1248 00:59:05,560 --> 00:59:08,350 And I'm sure that's how I got confused about it. 1249 00:59:08,350 --> 00:59:09,820 I'm sure most people are confused about 1250 00:59:09,820 --> 00:59:10,930 it because of that. 1251 00:59:10,930 --> 00:59:13,920 And until they do a few thought experiments or have to 1252 00:59:13,920 --> 00:59:16,360 teach it and really sort through it, they won't figure 1253 00:59:16,360 --> 00:59:17,790 out that it's actually not a force. 1254 00:59:17,790 --> 00:59:20,820 Now I'm sure Walter Lewin doesn't internally think of it 1255 00:59:20,820 --> 00:59:21,190 as a force. 1256 00:59:21,190 --> 00:59:22,740 He knows it behaves differently. 1257 00:59:22,740 --> 00:59:27,070 But it's so easy to use this shorthand, and then the 1258 00:59:27,070 --> 00:59:29,740 students, they don't have any other structure for it. 1259 00:59:29,740 --> 00:59:31,250 They'll just think it does act like a force. 1260 00:59:31,250 --> 00:59:34,090 It add vectors, but it doesn't. 1261 00:59:34,090 --> 00:59:34,400 Yeah. 1262 00:59:34,400 --> 00:59:37,000 So that was, I thought, a dubious point. 1263 00:59:37,000 --> 00:59:40,170 But it's standard, unfortunately. 1264 00:59:40,170 --> 00:59:41,985 It's a good lesson that just because something's standard 1265 00:59:41,985 --> 00:59:45,735 doesn't mean it's a good thing to do. 1266 00:59:45,735 --> 00:59:46,685 Yep. 1267 00:59:46,685 --> 00:59:49,070 AUDIENCE: He used the big chalk and colors. 1268 00:59:49,070 --> 00:59:50,660 PROFESSOR: Yeah, big yeah. 1269 00:59:50,660 --> 00:59:53,180 Right. 1270 00:59:53,180 --> 00:59:55,350 Actually, if you need to order this chalk, it's called 1271 00:59:55,350 --> 00:59:56,600 railroad crayon. 1272 01:00:07,690 --> 01:00:10,150 You want to be careful to get railroad crayon, because there 1273 01:00:10,150 --> 01:00:14,200 is actually big chalk you can buy from, I don't know, 1274 01:00:14,200 --> 01:00:16,040 variety stores. 1275 01:00:16,040 --> 01:00:19,560 And that's for, for example, writing messages on sidewalks. 1276 01:00:19,560 --> 01:00:22,770 And the problem with that is that has wax in it so that it 1277 01:00:22,770 --> 01:00:25,160 stays against the rain. 1278 01:00:25,160 --> 01:00:28,000 But that's not so good for the blackboard. 1279 01:00:28,000 --> 01:00:29,390 It's much harder to get off. 1280 01:00:29,390 --> 01:00:32,910 Railroad crayon is designed to be removed easily. 1281 01:00:32,910 --> 01:00:35,450 If you order railroad crayon, unfortunately it seems to come 1282 01:00:35,450 --> 01:00:39,150 in boxes of 144. 1283 01:00:39,150 --> 01:00:41,140 Maybe you can get a box of 72. 1284 01:00:41,140 --> 01:00:43,220 So share it around. 1285 01:00:43,220 --> 01:00:45,680 If you find a source with smaller amounts, let me know. 1286 01:00:45,680 --> 01:00:49,660 But the ones we found were 144, a gross, one dozen dozen. 1287 01:00:49,660 --> 01:00:52,450 But yeah, he used railroad crayon, so it was very easy to 1288 01:00:52,450 --> 01:00:53,790 see what he was doing. 1289 01:00:53,790 --> 01:00:55,150 And he used colors. 1290 01:00:55,150 --> 01:00:57,360 For example, forces were always read. 1291 01:00:57,360 --> 01:01:00,590 And he used a consistent naming convention for that, so 1292 01:01:00,590 --> 01:01:02,530 he wasn't throwing noise onto the system. 1293 01:01:02,530 --> 01:01:02,720 Yeah. 1294 01:01:02,720 --> 01:01:04,970 AUDIENCE: This was mentioned before, but I think one 1295 01:01:04,970 --> 01:01:06,827 important thing he did is that he created 1296 01:01:06,827 --> 01:01:09,234 suspense by taking a risk. 1297 01:01:09,234 --> 01:01:11,210 Because he repeated the full experiment in class. 1298 01:01:11,210 --> 01:01:12,692 Because [INAUDIBLE]. 1299 01:01:18,230 --> 01:01:21,810 PROFESSOR: He created suspense by taking a risk. 1300 01:01:21,810 --> 01:01:26,420 So there was actually tension, not this kind of tension, but 1301 01:01:26,420 --> 01:01:29,350 the good kind attention where people were involved in 1302 01:01:29,350 --> 01:01:30,070 interested. 1303 01:01:30,070 --> 01:01:32,720 Because he redid the experiment, and it could have 1304 01:01:32,720 --> 01:01:34,910 come out not quite right. 1305 01:01:34,910 --> 01:01:37,090 And amazingly, it did come out right. 1306 01:01:37,090 --> 01:01:39,670 And when it does, then the point he's trying to make it 1307 01:01:39,670 --> 01:01:43,700 even more strongly reinforced about physics works. 1308 01:01:43,700 --> 01:01:44,720 And that was his goal. 1309 01:01:44,720 --> 01:01:47,900 That was one of his overall goals for the implicit. 1310 01:01:47,900 --> 01:01:50,690 I don't know if he ever stated it, but one of his implicit 1311 01:01:50,690 --> 01:01:53,030 goals, you can see, is to convince people 1312 01:01:53,030 --> 01:01:54,240 that physics works. 1313 01:01:54,240 --> 01:01:56,170 It's a way of understanding the world. 1314 01:01:56,170 --> 01:01:59,040 And if you really believe that, well, you should be 1315 01:01:59,040 --> 01:02:00,370 willing to put your money where your mouth 1316 01:02:00,370 --> 01:02:02,750 is and do it yourself. 1317 01:02:02,750 --> 01:02:04,640 There's an another famous experiment-- 1318 01:02:04,640 --> 01:02:08,380 I don't know if it's in Lewin's lectures-- 1319 01:02:08,380 --> 01:02:12,510 where you want to show that energy is conserved. 1320 01:02:12,510 --> 01:02:17,680 And the way you measure energy conservation is how far a 1321 01:02:17,680 --> 01:02:19,300 pendulum swings. 1322 01:02:19,300 --> 01:02:21,260 So now the way you do the experiment, you have some 1323 01:02:21,260 --> 01:02:23,680 giant pendulum with a bowling ball or a cannon ball at the 1324 01:02:23,680 --> 01:02:26,140 end hanging from the top of the physics lecture hall, 1325 01:02:26,140 --> 01:02:27,510 which is about this high. 1326 01:02:27,510 --> 01:02:29,520 And you release it from your nose, and 1327 01:02:29,520 --> 01:02:31,240 you just stand there. 1328 01:02:31,240 --> 01:02:34,070 So if energy's really conserved, it's going to come 1329 01:02:34,070 --> 01:02:38,100 just to where you released it and no farther, which is good 1330 01:02:38,100 --> 01:02:39,180 because your nose is right there. 1331 01:02:39,180 --> 01:02:40,490 A little farther would hurt. 1332 01:02:40,490 --> 01:02:42,350 The problem-- 1333 01:02:42,350 --> 01:02:44,100 this still doesn't show physics doesn't work, but it 1334 01:02:44,100 --> 01:02:44,960 looks like it-- 1335 01:02:44,960 --> 01:02:48,380 is that it's so tempting to give it a little push when you 1336 01:02:48,380 --> 01:02:50,370 release it. 1337 01:02:50,370 --> 01:02:54,060 And it's just hard not to do, because whenever you let go of 1338 01:02:54,060 --> 01:02:55,800 things, you push a ball, you throw something 1339 01:02:55,800 --> 01:02:56,590 in the laundry basket. 1340 01:02:56,590 --> 01:02:58,110 So now you give it a little bit of 1341 01:02:58,110 --> 01:02:59,910 push, and physics works. 1342 01:02:59,910 --> 01:03:03,940 So it comes back with exactly the same push, which wouldn't 1343 01:03:03,940 --> 01:03:06,350 be a problem if it was a wiffleball or a tennis ball. 1344 01:03:06,350 --> 01:03:08,340 But because it's a giant cannon ball and at the other 1345 01:03:08,340 --> 01:03:11,040 end of it's your nose, it gives you a nice 1346 01:03:11,040 --> 01:03:12,610 crunch right there. 1347 01:03:15,690 --> 01:03:17,940 I would only do that expect if I'd practiced it and make sure 1348 01:03:17,940 --> 01:03:18,890 I didn't push it. 1349 01:03:18,890 --> 01:03:24,110 But even if you do push it, it too shows physics works. 1350 01:03:24,110 --> 01:03:28,000 But yeah, he created suspense. 1351 01:03:28,000 --> 01:03:28,840 Yes. 1352 01:03:28,840 --> 01:03:31,108 AUDIENCE: So how can people do this in other disciplines? 1353 01:03:31,108 --> 01:03:33,418 In physics, you have weights and swinging 1354 01:03:33,418 --> 01:03:36,140 pendulums and blocks. 1355 01:03:36,140 --> 01:03:37,790 PROFESSOR: How can you do it in other fields? 1356 01:03:37,790 --> 01:03:39,990 Yeah, it's a good question. 1357 01:03:39,990 --> 01:03:41,720 If you remember, the wood blocks-- 1358 01:03:41,720 --> 01:03:43,770 this is physics, mechanical engineering-- 1359 01:03:43,770 --> 01:03:46,080 there was also suspense. 1360 01:03:46,080 --> 01:03:54,140 Because when I tap this one, and then everyone was dead 1361 01:03:54,140 --> 01:03:58,030 silent before we tapped this one-- 1362 01:03:58,030 --> 01:04:01,030 just for review-- 1363 01:04:01,030 --> 01:04:02,270 because everyone wanted to know. 1364 01:04:02,270 --> 01:04:04,850 So suspense was created. 1365 01:04:04,850 --> 01:04:08,600 And it's just like any sort of magic trick or performance. 1366 01:04:11,170 --> 01:04:12,730 You have to prepare it. 1367 01:04:12,730 --> 01:04:15,518 So it doesn't have to be that you bring something in. 1368 01:04:18,020 --> 01:04:18,860 It helps. 1369 01:04:18,860 --> 01:04:22,940 But, let's see, what else could you do it in? 1370 01:04:22,940 --> 01:04:24,620 Chemistry. 1371 01:04:24,620 --> 01:04:25,950 In chemistry-- 1372 01:04:25,950 --> 01:04:27,440 it helps to bring stuff in, no question-- you 1373 01:04:27,440 --> 01:04:28,450 could bring in chemicals. 1374 01:04:28,450 --> 01:04:30,850 What do you think is going to happen when I mix these two? 1375 01:04:30,850 --> 01:04:31,970 Well, what do we know about this? 1376 01:04:31,970 --> 01:04:33,490 What do we know about this? 1377 01:04:33,490 --> 01:04:36,354 What's going to happen when I drop a ball through this? 1378 01:04:36,354 --> 01:04:37,740 Is this viscous? 1379 01:04:37,740 --> 01:04:38,360 Is it not? 1380 01:04:38,360 --> 01:04:39,920 What clues did you have? 1381 01:04:39,920 --> 01:04:40,980 OK. 1382 01:04:40,980 --> 01:04:42,320 Let's see if now that's consistent with 1383 01:04:42,320 --> 01:04:43,360 how the thing behaves. 1384 01:04:43,360 --> 01:04:45,350 So it doesn't have to be pure physics. 1385 01:04:45,350 --> 01:04:48,470 Though it does help to bring things in, and so you do want 1386 01:04:48,470 --> 01:04:55,520 to make everything you have as visceral and as visualizable 1387 01:04:55,520 --> 01:04:56,590 as possible. 1388 01:04:56,590 --> 01:05:00,640 So that is a general transferable principal. 1389 01:05:00,640 --> 01:05:07,490 Let me write down four general principles that you can use in 1390 01:05:07,490 --> 01:05:11,180 all lecture performance, which is basically 1391 01:05:11,180 --> 01:05:12,670 everything you said here. 1392 01:05:32,020 --> 01:05:34,580 The first one I'm going to write down is very neglected, 1393 01:05:34,580 --> 01:05:36,290 but you've just mentioned it, which is the 1394 01:05:36,290 --> 01:05:37,540 suspense and the timing. 1395 01:05:41,540 --> 01:05:45,280 If you want evidence that timing really matters, just go 1396 01:05:45,280 --> 01:05:49,550 watch Romeo and Juliet again, or read Romeo and Juliet. 1397 01:05:49,550 --> 01:05:51,830 Just because they were slightly off in their timing, 1398 01:05:51,830 --> 01:05:53,190 they all committed suicide, basically. 1399 01:05:58,090 --> 01:06:00,490 That's probably the very, very, very, very CliffsNotes 1400 01:06:00,490 --> 01:06:01,740 plot summary. 1401 01:06:05,380 --> 01:06:08,090 And another part about timing, if you want more evidence that 1402 01:06:08,090 --> 01:06:12,170 timing really matters, try telling a joke and tell the 1403 01:06:12,170 --> 01:06:15,130 punchline first. 1404 01:06:15,130 --> 01:06:16,970 See how well that does. 1405 01:06:16,970 --> 01:06:20,260 And even a small example of that, for stories too. 1406 01:06:20,260 --> 01:06:23,500 Stories, you want to tell the important part later, and you 1407 01:06:23,500 --> 01:06:25,540 want to give the introduction first. 1408 01:06:25,540 --> 01:06:29,060 Again, remember the sentence structure here, which is that 1409 01:06:29,060 --> 01:06:32,770 the thing with emphasis comes right at the end. 1410 01:06:32,770 --> 01:06:34,940 If the thing you want to emphasize happened at the 1411 01:06:34,940 --> 01:06:37,790 beginning, then your timing is off, and 1412 01:06:37,790 --> 01:06:38,850 things will fall flat. 1413 01:06:38,850 --> 01:06:39,220 Yes. 1414 01:06:39,220 --> 01:06:39,671 AUDIENCE: OK. 1415 01:06:39,671 --> 01:06:42,830 But that's exactly contradictory to the way some 1416 01:06:42,830 --> 01:06:48,760 people want their information laid out, which is tell me the 1417 01:06:48,760 --> 01:06:51,700 most important thing, and then back up with all the details. 1418 01:06:51,700 --> 01:06:53,900 PROFESSOR: Yeah. 1419 01:06:53,900 --> 01:06:54,120 OK. 1420 01:06:54,120 --> 01:06:56,940 So that's a good comment, which is that it's opposite of 1421 01:06:56,940 --> 01:06:58,190 how people say they want things. 1422 01:06:58,190 --> 01:06:59,860 They want the most important stuff first 1423 01:06:59,860 --> 01:07:01,800 and then the details. 1424 01:07:01,800 --> 01:07:06,670 The way I square that circle is I don't want to give away 1425 01:07:06,670 --> 01:07:07,920 punchlines. 1426 01:07:09,950 --> 01:07:10,770 Oh, those are gone. 1427 01:07:10,770 --> 01:07:13,400 So suppose I'm starting a new unit, and we're going to do a 1428 01:07:13,400 --> 01:07:16,120 unit on extreme cases. 1429 01:07:16,120 --> 01:07:19,150 I don't want to give away the punchline, which is, oh, this 1430 01:07:19,150 --> 01:07:21,780 problem is hard until you use extreme cases. 1431 01:07:21,780 --> 01:07:24,665 So I say, forget the organization of the course 1432 01:07:24,665 --> 01:07:27,150 that I told you about before, and we're just going to do an 1433 01:07:27,150 --> 01:07:28,550 example and discuss it. 1434 01:07:28,550 --> 01:07:31,020 Then we're going to look at what makes it really easy, and 1435 01:07:31,020 --> 01:07:34,180 then the punchline is extreme cases. 1436 01:07:34,180 --> 01:07:34,640 OK. 1437 01:07:34,640 --> 01:07:37,630 Now that we know the punchline, because we've done 1438 01:07:37,630 --> 01:07:40,750 the example, now I'm very happy to say extreme cases. 1439 01:07:40,750 --> 01:07:42,280 Let's use extreme cases here. 1440 01:07:42,280 --> 01:07:45,310 And this whole unit is going to be about extreme cases. 1441 01:07:45,310 --> 01:07:47,380 So now people still have the structure, but the very 1442 01:07:47,380 --> 01:07:49,650 beginning of it, they're a little confused. 1443 01:07:49,650 --> 01:07:51,470 And I like the confusion. 1444 01:07:51,470 --> 01:07:54,870 So that's part of this. 1445 01:07:54,870 --> 01:07:58,050 In a play or in a movie, or you go to a movie, you're not 1446 01:07:58,050 --> 01:07:59,920 even sure who are the main characters and 1447 01:07:59,920 --> 01:08:00,900 what are they up to. 1448 01:08:00,900 --> 01:08:04,080 And then it comes into focus soon but not right away. 1449 01:08:04,080 --> 01:08:05,410 And part of that is to draw you in. 1450 01:08:08,330 --> 01:08:09,040 Yeah. 1451 01:08:09,040 --> 01:08:11,950 I wouldn't begin a lecture by telling people everything that 1452 01:08:11,950 --> 01:08:16,680 they need to know, because that's spoiling the timing. 1453 01:08:16,680 --> 01:08:19,569 The beginning of the lecture is this kind of sacred moment 1454 01:08:19,569 --> 01:08:22,430 when you want to draw everybody into the lecture. 1455 01:08:25,540 --> 01:08:28,590 And the beginning of a course is doubly that much. 1456 01:08:28,590 --> 01:08:32,689 You want to draw people in, not tell them, oh, yeah, here 1457 01:08:32,689 --> 01:08:35,520 are the rules on homework collaboration and blah, blah, 1458 01:08:35,520 --> 01:08:37,210 blah, blah. 1459 01:08:37,210 --> 01:08:39,425 You want to emphasize the important things first, and 1460 01:08:39,425 --> 01:08:42,380 you want to use this to pull people in so that you can come 1461 01:08:42,380 --> 01:08:43,340 to a punchline. 1462 01:08:43,340 --> 01:08:45,100 The punchline doesn't have to be way at the end of the 1463 01:08:45,100 --> 01:08:46,460 lecture or the end of the course. 1464 01:08:46,460 --> 01:08:49,029 It can be soon, and you can have a lot of soon punchlines. 1465 01:08:49,029 --> 01:08:51,300 But for each one, you need to build to it. 1466 01:08:51,300 --> 01:08:51,649 Yes. 1467 01:08:51,649 --> 01:08:53,050 AUDIENCE: [INAUDIBLE]. 1468 01:08:53,050 --> 01:08:56,786 When I did my referencing thing, the first slide had a 1469 01:08:56,786 --> 01:08:59,110 list of goals that I wanted to make, because I thought that 1470 01:08:59,110 --> 01:09:01,420 that was what we should be talking about in [INAUDIBLE] 1471 01:09:01,420 --> 01:09:01,649 teaching. 1472 01:09:01,649 --> 01:09:03,790 And then you asked, would you have included those when you 1473 01:09:03,790 --> 01:09:04,380 started the real lecture? 1474 01:09:04,380 --> 01:09:04,740 PROFESSOR: Right. 1475 01:09:04,740 --> 01:09:05,767 AUDIENCE: And I said, I wouldn't. 1476 01:09:05,767 --> 01:09:07,621 I would just plunge right into the material, because I was 1477 01:09:07,621 --> 01:09:09,490 thinking along the line of what you're saying now. 1478 01:09:09,490 --> 01:09:11,436 And then you said, no, I think it's actually good for the 1479 01:09:11,436 --> 01:09:13,325 students to see it outlined what they're going to learn. 1480 01:09:13,325 --> 01:09:15,750 And so that's actually [INAUDIBLE]. 1481 01:09:15,750 --> 01:09:16,200 PROFESSOR: Yeah. 1482 01:09:16,200 --> 01:09:16,600 That's right. 1483 01:09:16,600 --> 01:09:18,574 I think what I would do is I would show them that goals-- 1484 01:09:21,600 --> 01:09:24,660 Goals are OK, as long as you don't begin the lecture by 1485 01:09:24,660 --> 01:09:27,880 saying, here are my goals, because that's that secret 1486 01:09:27,880 --> 01:09:29,109 time you're taking away from. 1487 01:09:29,109 --> 01:09:31,880 I would put the goals, say, on a side board, so they can see 1488 01:09:31,880 --> 01:09:34,460 them all the time, or write the, just after you've done 1489 01:09:34,460 --> 01:09:35,729 your punchline. 1490 01:09:35,729 --> 01:09:36,779 Then put them all up. 1491 01:09:36,779 --> 01:09:38,710 AUDIENCE: So it's the second or third slide. 1492 01:09:38,710 --> 01:09:39,109 PROFESSOR: Yeah. 1493 01:09:39,109 --> 01:09:39,990 That's right. 1494 01:09:39,990 --> 01:09:41,240 Yeah. 1495 01:09:42,930 --> 01:09:45,810 The very first slide is something interesting that 1496 01:09:45,810 --> 01:09:48,069 doesn't necessarily seem like it's related to the class. 1497 01:09:48,069 --> 01:09:50,250 And that's already a punchline. 1498 01:09:50,250 --> 01:09:50,939 Oh, wow, this? 1499 01:09:50,939 --> 01:09:52,790 We can understand this from the stuff in class? 1500 01:09:52,790 --> 01:09:54,600 I want to know. 1501 01:09:54,600 --> 01:09:55,860 That's a drawing in. 1502 01:09:55,860 --> 01:09:57,100 And then you get to the punchline, which 1503 01:09:57,100 --> 01:09:58,210 is, yes, you can. 1504 01:09:58,210 --> 01:10:01,410 And the goals are to see this all over and see these three 1505 01:10:01,410 --> 01:10:04,095 principles that we just used and really understand them. 1506 01:10:07,010 --> 01:10:11,470 OK Another one be bold, so bold gestures. 1507 01:10:17,350 --> 01:10:20,410 Bold gestures, voice, you'll see that all 1508 01:10:20,410 --> 01:10:21,660 throughout Walter Lewin. 1509 01:10:24,160 --> 01:10:27,320 Another one, we've actually done, I would say, a lot more 1510 01:10:27,320 --> 01:10:30,082 with it than you saw in the lecture, which is-- 1511 01:10:36,270 --> 01:10:40,000 And the third one is you want to involve the audience by 1512 01:10:40,000 --> 01:10:42,590 asking them questions, making your whole lecture 1513 01:10:42,590 --> 01:10:43,200 interactive. 1514 01:10:43,200 --> 01:10:45,580 So we've discussed, actually, many ways where the Lewin 1515 01:10:45,580 --> 01:10:49,170 lecture could be improved in that direction. 1516 01:10:49,170 --> 01:10:53,030 And perhaps underlying everything, none of this 1517 01:10:53,030 --> 01:11:00,050 really works unless there's principal four, which is that 1518 01:11:00,050 --> 01:11:01,630 you have to care. 1519 01:11:01,630 --> 01:11:03,660 You have to really, really love what you're doing and 1520 01:11:03,660 --> 01:11:05,660 transmit that to the students. 1521 01:11:05,660 --> 01:11:08,730 And then, all of these things become so much 1522 01:11:08,730 --> 01:11:10,760 easier when you care. 1523 01:11:10,760 --> 01:11:15,660 So those are the fundamental principles of lecture 1524 01:11:15,660 --> 01:11:17,510 performing and, basically, planning 1525 01:11:17,510 --> 01:11:18,980 around things like that. 1526 01:11:18,980 --> 01:11:22,200 And if I just had written those down in the beginning, 1527 01:11:22,200 --> 01:11:23,340 it wouldn't have made sense. 1528 01:11:23,340 --> 01:11:26,470 But now you've seen many, many, many examples, and we've 1529 01:11:26,470 --> 01:11:31,240 had many discussions about it that I wish you success in 1530 01:11:31,240 --> 01:11:35,180 applying good timing, good bold gestures, strong 1531 01:11:35,180 --> 01:11:39,290 gestures, and involving the audience, not just emotionally 1532 01:11:39,290 --> 01:11:44,490 or cognitively but both, so that you provide long-lasting 1533 01:11:44,490 --> 01:11:47,930 learning and interest in the subject that you love. 1534 01:11:47,930 --> 01:11:49,010 OK. 1535 01:11:49,010 --> 01:11:52,510 If you could fill out the sheets for just one minute. 1536 01:11:52,510 --> 01:11:56,110 And then we will have office hours. 1537 01:11:56,110 --> 01:11:58,530 Actually, what we'll do is we'll meet right outside the 1538 01:11:58,530 --> 01:12:03,010 door, and then we'll just go sit in the cafe area. 1539 01:12:03,010 --> 01:12:05,850 And anyone who wants to get a bagel can also get a bagel, if 1540 01:12:05,850 --> 01:12:08,090 you're interested. 1541 01:12:08,090 --> 01:12:10,310 Answers from Lecture 8 to questions 1542 01:12:10,310 --> 01:12:11,675 generated in Lecture 7. 1543 01:12:16,540 --> 01:12:20,990 PROFESSOR: So first question was, a while ago I mentioned 1544 01:12:20,990 --> 01:12:24,560 there was research saying that if you pay people for things 1545 01:12:24,560 --> 01:12:29,530 they like doing then they start enjoying it less. 1546 01:12:29,530 --> 01:12:31,500 Can I give you a reference for that? 1547 01:12:31,500 --> 01:12:35,750 The reference for that is I actually put on the readings 1548 01:12:35,750 --> 01:12:38,830 for next week, which is the political barriers to 1549 01:12:38,830 --> 01:12:42,150 educational change session, one of the five readings-- 1550 01:12:42,150 --> 01:12:43,990 they're all basically short-- 1551 01:12:43,990 --> 01:12:47,540 is by Alfie Kohn, and it's about competition. 1552 01:12:47,540 --> 01:12:50,130 And that's one of the areas he researches a lot. 1553 01:12:54,930 --> 01:12:57,370 I gave you one of the short articles by him to read. 1554 01:12:57,370 --> 01:13:02,330 But his whole website as lots of different articles and 1555 01:13:02,330 --> 01:13:04,360 references. 1556 01:13:04,360 --> 01:13:05,930 He has a whole book on the whole 1557 01:13:05,930 --> 01:13:12,550 subject called No Contest. 1558 01:13:12,550 --> 01:13:15,250 I think the subtitle is The Case Against Competition. 1559 01:13:15,250 --> 01:13:19,190 So he goes through, I don't know, 100 or 200 studies about 1560 01:13:19,190 --> 01:13:21,400 the effects of rewards on people's 1561 01:13:21,400 --> 01:13:23,820 performance and interests. 1562 01:13:23,820 --> 01:13:26,110 It's a totally fascinating book. 1563 01:13:26,110 --> 01:13:28,485 And I think it just came out, or recently it 1564 01:13:28,485 --> 01:13:29,350 has the second edition. 1565 01:13:29,350 --> 01:13:31,660 But both editions are completely fine, so whichever 1566 01:13:31,660 --> 01:13:33,030 one you can find, use that. 1567 01:13:33,030 --> 01:13:36,200 And on his website, you'll find many articles on that 1568 01:13:36,200 --> 01:13:40,560 theme, and I've given you one to read for next week. 1569 01:13:40,560 --> 01:13:42,630 OK. 1570 01:13:42,630 --> 01:13:44,190 What is the Berkeley Physics Course? 1571 01:13:44,190 --> 01:13:46,730 The Berkeley Physics Course-- 1572 01:13:46,730 --> 01:13:49,860 This is interesting, because in the '60s there was a whole 1573 01:13:49,860 --> 01:13:51,930 bunch of change. 1574 01:13:51,930 --> 01:13:56,110 It was change in political systems and protests and legal 1575 01:13:56,110 --> 01:13:58,730 systems, the Civil Rights Act. 1576 01:13:58,730 --> 01:14:00,620 And there was also change in education. 1577 01:14:00,620 --> 01:14:04,660 And that's probably not coincidence, that both changes 1578 01:14:04,660 --> 01:14:06,710 were coupled or happened together. 1579 01:14:06,710 --> 01:14:08,550 There was the rise of the Free School Movement. 1580 01:14:08,550 --> 01:14:11,230 There was also, in the university level, lots of 1581 01:14:11,230 --> 01:14:13,270 different new curricula started. 1582 01:14:13,270 --> 01:14:16,340 The Feynman Lectures on physics are a famous one that 1583 01:14:16,340 --> 01:14:18,870 happened way over on the other side of 1584 01:14:18,870 --> 01:14:20,560 the country and Caltech. 1585 01:14:20,560 --> 01:14:23,780 And the Berkeley Physics Course happened also on the 1586 01:14:23,780 --> 01:14:26,540 other side of the country. 1587 01:14:26,540 --> 01:14:27,710 There are several volumes in it. 1588 01:14:27,710 --> 01:14:30,220 Probably the best known is Ed Purcell's 1589 01:14:30,220 --> 01:14:32,250 Electricity and Magnetism. 1590 01:14:32,250 --> 01:14:34,510 That's one of the classics of the Berkeley Physics Course. 1591 01:14:34,510 --> 01:14:37,320 There's a less well-known volume, which is, I think, 1592 01:14:37,320 --> 01:14:39,265 even better, which is by Frank Crawford, 1593 01:14:39,265 --> 01:14:41,670 and it's called Waves. 1594 01:14:41,670 --> 01:14:44,980 The edition I have came in the back with a whole bunch of 1595 01:14:44,980 --> 01:14:48,500 polarizers and toys you could use to actually do home 1596 01:14:48,500 --> 01:14:49,100 experiments. 1597 01:14:49,100 --> 01:14:50,790 And at the end of every chapter, there are home 1598 01:14:50,790 --> 01:14:51,350 experiments. 1599 01:14:51,350 --> 01:14:54,430 I think they're called "Kitchen Sink Experiments, and 1600 01:14:54,430 --> 01:14:57,630 there were toys in the back in the little pocket that you 1601 01:14:57,630 --> 01:14:58,500 could use for it. 1602 01:14:58,500 --> 01:15:01,330 So if you find a used copy, those toys might not be there, 1603 01:15:01,330 --> 01:15:03,130 but the book is still wonderful. 1604 01:15:03,130 --> 01:15:05,930 So those were two pieces of the Berkeley Physics Course, 1605 01:15:05,930 --> 01:15:07,340 and they were about six volumes. 1606 01:15:07,340 --> 01:15:09,640 And MIT had a whole set of books as well, I 1607 01:15:09,640 --> 01:15:11,150 think by Tony French. 1608 01:15:11,150 --> 01:15:14,160 So it was a whole time of ferment, and lots of changes 1609 01:15:14,160 --> 01:15:17,120 happened, many of them good. 1610 01:15:17,120 --> 01:15:20,080 OK. 1611 01:15:20,080 --> 01:15:22,570 How can you apply these lecture techniques that we 1612 01:15:22,570 --> 01:15:23,795 talked about last time to laboratory 1613 01:15:23,795 --> 01:15:25,130 or practical courses? 1614 01:15:25,130 --> 01:15:27,030 This is actually an important topic, because many 1615 01:15:27,030 --> 01:15:29,150 of us will do that? 1616 01:15:29,150 --> 01:15:31,850 What's the right balance between teaching and lecturing 1617 01:15:31,850 --> 01:15:34,920 and allowing students to solve the lab problems on their own, 1618 01:15:34,920 --> 01:15:36,540 in other words, giving them enough rope to hang 1619 01:15:36,540 --> 01:15:38,000 themselves? 1620 01:15:38,000 --> 01:15:39,110 Yeah. 1621 01:15:39,110 --> 01:15:40,060 You do want to do that. 1622 01:15:40,060 --> 01:15:43,240 You want to give people enough rope, but you also want to 1623 01:15:43,240 --> 01:15:45,890 guide them, because you do know more than them. 1624 01:15:45,890 --> 01:15:49,300 So I don't look at laboratory teaching, practical teaching 1625 01:15:49,300 --> 01:15:51,100 as that different than lecture teaching. 1626 01:15:51,100 --> 01:15:53,680 In some ways, it's easier, because one of the goals in 1627 01:15:53,680 --> 01:15:56,890 lecture teaching is to show people that all the theory 1628 01:15:56,890 --> 01:15:59,830 you're talking about actually has any relevance at all. 1629 01:15:59,830 --> 01:16:02,570 And you have to try to work hard to bring stuff into the 1630 01:16:02,570 --> 01:16:04,640 classroom and really show, yeah, look this really means 1631 01:16:04,640 --> 01:16:08,770 something, the way Walter Lewin stood on the pendulum or 1632 01:16:08,770 --> 01:16:11,540 sat on the pendulum himself and was the pendulum to really 1633 01:16:11,540 --> 01:16:14,480 show, yes, this applies here. 1634 01:16:14,480 --> 01:16:17,600 In a laboratory practical class, if the practicals are 1635 01:16:17,600 --> 01:16:22,210 at all interesting, that's automatically done for you. 1636 01:16:22,210 --> 01:16:26,310 The last practical class I taught was the electronics 1637 01:16:26,310 --> 01:16:29,180 practical for physics majors. 1638 01:16:29,180 --> 01:16:32,750 At the end, they built an AM radio, a crystal radio. 1639 01:16:32,750 --> 01:16:36,440 So that actually had a nice finale, and experiments before 1640 01:16:36,440 --> 01:16:39,150 that built up to it. 1641 01:16:39,150 --> 01:16:42,440 The relevance was already done for me, but the problems the 1642 01:16:42,440 --> 01:16:45,390 students had were the same as in regular lecture. 1643 01:16:45,390 --> 01:16:46,830 They didn't understand the concepts. 1644 01:16:46,830 --> 01:16:49,230 For example, what does a capacitor do? 1645 01:16:49,230 --> 01:16:50,330 What does an inductor do? 1646 01:16:50,330 --> 01:16:51,320 How do they work together? 1647 01:16:51,320 --> 01:16:52,440 What is resonance? 1648 01:16:52,440 --> 01:16:54,900 So what I did for them is I gave them short little 1649 01:16:54,900 --> 01:16:58,410 mini-lectures, two minutes three minutes on a conceptual 1650 01:16:58,410 --> 01:17:00,535 question, and then sent them off working. 1651 01:17:03,780 --> 01:17:05,730 Some of the other problems they had were, for example, 1652 01:17:05,730 --> 01:17:08,950 they were really scared of oscilloscopes. 1653 01:17:08,950 --> 01:17:09,960 They just got to the oscilloscope, and they 1654 01:17:09,960 --> 01:17:12,070 thought, what the hell do I do with this thing? 1655 01:17:12,070 --> 01:17:15,200 So do I used an exercise that was done to me when I took the 1656 01:17:15,200 --> 01:17:17,830 same class as an undergraduate, which was in 1657 01:17:17,830 --> 01:17:23,050 your laboratory pair one person turns around and the 1658 01:17:23,050 --> 01:17:26,380 other person randomizes the oscilloscope settings. 1659 01:17:26,380 --> 01:17:29,595 They just turn all of dials to some random setting, and then 1660 01:17:29,595 --> 01:17:32,020 the first person has to turn back and try to get some 1661 01:17:32,020 --> 01:17:33,450 signal on the screen. 1662 01:17:33,450 --> 01:17:36,500 So they have to figure out, OK, this voltage setting is 1663 01:17:36,500 --> 01:17:38,930 crazy and get it back to a setting. 1664 01:17:38,930 --> 01:17:41,030 And once you do that, you're no longer afraid of the 1665 01:17:41,030 --> 01:17:41,910 oscilloscope. 1666 01:17:41,910 --> 01:17:45,290 Again, you can do in class problems that 1667 01:17:45,290 --> 01:17:46,700 people work on together. 1668 01:17:46,700 --> 01:17:49,260 You can give short little conceptual questions. 1669 01:17:49,260 --> 01:17:52,240 So in a way, laboratory teaching isn't that different, 1670 01:17:52,240 --> 01:17:56,220 provided that the laboratory isn't just a cookbook in the 1671 01:17:56,220 --> 01:17:58,780 sense that, OK, do this, now measure that, now measure 1672 01:17:58,780 --> 01:18:00,690 that, now measure that, now measure that. 1673 01:18:00,690 --> 01:18:03,080 OK, write it all in your report. 1674 01:18:03,080 --> 01:18:06,290 That's like lecturing just by saying now copy this down, now 1675 01:18:06,290 --> 01:18:07,960 copy that down, now copy that down. 1676 01:18:07,960 --> 01:18:10,230 So if you get away from that in lecturing and that in 1677 01:18:10,230 --> 01:18:13,810 practical, then you get to the similarities between the two, 1678 01:18:13,810 --> 01:18:16,730 and you can apply pretty much every lesson from here. 1679 01:18:19,510 --> 01:18:20,760 OK. 1680 01:18:22,800 --> 01:18:23,305 Oh, yeah. 1681 01:18:23,305 --> 01:18:24,500 Many of you pointed this out. 1682 01:18:24,500 --> 01:18:27,300 The distillation of examples into principles that we did. 1683 01:18:27,300 --> 01:18:30,500 So we looked at Walter Lewin's lecture number 10, and then we 1684 01:18:30,500 --> 01:18:33,620 distilled from our discussion various principles of 1685 01:18:33,620 --> 01:18:35,390 lecturing and performing. 1686 01:18:35,390 --> 01:18:36,490 And many of you said, oh, yeah, that 1687 01:18:36,490 --> 01:18:38,360 should have gone longer. 1688 01:18:38,360 --> 01:18:40,480 You liked the principles, but we should have done that for 1689 01:18:40,480 --> 01:18:42,150 longer, which I think is a great sign. 1690 01:18:42,150 --> 01:18:44,260 I think it's good that you guys are figuring out what 1691 01:18:44,260 --> 01:18:44,960 could be improved. 1692 01:18:44,960 --> 01:18:46,030 And I agree with you. 1693 01:18:46,030 --> 01:18:49,210 I just got so carried away with all the interesting 1694 01:18:49,210 --> 01:18:52,200 things you were finding that I didn't allocate enough time 1695 01:18:52,200 --> 01:18:53,210 for the principles. 1696 01:18:53,210 --> 01:18:57,180 So in my next life. 1697 01:18:57,180 --> 01:19:00,740 But also, the point is everyone did appreciate having 1698 01:19:00,740 --> 01:19:03,610 principles, so that's something to transfer for your 1699 01:19:03,610 --> 01:19:05,650 own teaching. 1700 01:19:05,650 --> 01:19:06,290 OK. 1701 01:19:06,290 --> 01:19:09,290 Let's see. 1702 01:19:09,290 --> 01:19:11,870 What kind of interactive examples and demos can you do 1703 01:19:11,870 --> 01:19:13,120 for a math class? 1704 01:19:15,710 --> 01:19:18,249 I brought an example. 1705 01:19:18,249 --> 01:19:20,790 They're in here. 1706 01:19:20,790 --> 01:19:24,000 This was actually an example I did last week in my 1707 01:19:24,000 --> 01:19:25,310 approximation class. 1708 01:19:25,310 --> 01:19:28,000 And I enjoyed it so much I thought I'd 1709 01:19:28,000 --> 01:19:29,250 show it to you too. 1710 01:19:35,350 --> 01:19:43,680 The principal I was teaching was the principle of easy 1711 01:19:43,680 --> 01:19:46,480 cases, also known as extreme cases often. 1712 01:19:46,480 --> 01:19:48,690 But I like this name better. 1713 01:19:48,690 --> 01:19:52,220 And then I wanted to show that this principle applies across 1714 01:19:52,220 --> 01:19:52,950 all kinds of areas. 1715 01:19:52,950 --> 01:19:53,810 You can use it in math. 1716 01:19:53,810 --> 01:19:54,590 You can use it in physics. 1717 01:19:54,590 --> 01:19:56,580 You can use it in engineering. 1718 01:19:56,580 --> 01:19:58,840 And what we were trying to derive is 1719 01:19:58,840 --> 01:20:00,948 the volume of a pyramid. 1720 01:20:00,948 --> 01:20:02,990 So the original problem was this. 1721 01:20:06,480 --> 01:20:10,290 You take a pyramid with a square base, and then you lop 1722 01:20:10,290 --> 01:20:12,860 off some piece of the top. 1723 01:20:12,860 --> 01:20:22,140 So the pyramid is B by B on the base and A by A square on 1724 01:20:22,140 --> 01:20:23,950 the top, and it has height h. 1725 01:20:26,480 --> 01:20:29,070 So what's the volume of that thing? 1726 01:20:29,070 --> 01:20:32,990 Well, you can guess a lot of it from easy cases. 1727 01:20:32,990 --> 01:20:34,140 I won't go through all of that. 1728 01:20:34,140 --> 01:20:36,970 But at some point, you need to work out in part of this guess 1729 01:20:36,970 --> 01:20:40,180 the easy cases, use the easy case that A equals 0. 1730 01:20:40,180 --> 01:20:43,070 In other words, you just have a regular square pyramid, like 1731 01:20:43,070 --> 01:20:45,725 one of the Egyptian pyramids of Gaza. 1732 01:20:45,725 --> 01:20:46,010 Giza? 1733 01:20:46,010 --> 01:20:47,900 Giza, maybe. 1734 01:20:47,900 --> 01:20:49,150 So then what's the volume? 1735 01:21:01,980 --> 01:21:02,310 OK. 1736 01:21:02,310 --> 01:21:07,830 Well, volume's going to be proportional to the height. 1737 01:21:07,830 --> 01:21:11,815 And then, it's got to have two more lengths here, so it's got 1738 01:21:11,815 --> 01:21:12,830 to have B squared here. 1739 01:21:12,830 --> 01:21:13,830 There's no A left. 1740 01:21:13,830 --> 01:21:15,080 But then what goes here? 1741 01:21:19,200 --> 01:21:20,630 What's the constant? 1742 01:21:20,630 --> 01:21:23,180 Well, this is actually where you can, yet 1743 01:21:23,180 --> 01:21:26,060 again, use easy cases. 1744 01:21:26,060 --> 01:21:32,970 So if you could find a special pyramid that could be combined 1745 01:21:32,970 --> 01:21:36,300 into a shape whose volume you know, then you could actually 1746 01:21:36,300 --> 01:21:37,770 figure out this constant. 1747 01:21:37,770 --> 01:21:39,590 Because you don't know the volume of one pyramid, but if 1748 01:21:39,590 --> 01:21:42,590 you could replicate it and then assemble them into a nice 1749 01:21:42,590 --> 01:21:45,610 shape, you're home free. 1750 01:21:45,610 --> 01:21:48,580 What nice shape could make this into? 1751 01:21:48,580 --> 01:21:52,520 And what pyramid shape do you need to be able to do that? 1752 01:21:52,520 --> 01:21:54,140 So take a minute and think about that. 1753 01:21:57,260 --> 01:21:59,480 Anyone have an idea? 1754 01:21:59,480 --> 01:22:01,410 What shape would you like to make? 1755 01:22:01,410 --> 01:22:04,290 AUDIENCE: Could you first make a rectangular cube and then 1756 01:22:04,290 --> 01:22:06,220 cut it into six pieces? 1757 01:22:06,220 --> 01:22:06,420 PROFESSOR: OK. 1758 01:22:06,420 --> 01:22:09,460 So you want to make a cube. 1759 01:22:09,460 --> 01:22:11,170 Let's talk about how you're going to make this cube. 1760 01:22:11,170 --> 01:22:13,720 You'd like to make the cube. 1761 01:22:13,720 --> 01:22:17,000 Now what part of the pyramid is going to become 1762 01:22:17,000 --> 01:22:17,990 the face of the cube? 1763 01:22:17,990 --> 01:22:20,230 Well, you have a square base, right? 1764 01:22:20,230 --> 01:22:23,220 So it seems reasonable to expect that each pyramid's 1765 01:22:23,220 --> 01:22:25,260 going to provide one face the cube. 1766 01:22:25,260 --> 01:22:28,300 So you need six pyramids to make this cube. 1767 01:22:28,300 --> 01:22:31,020 Well, what shape should the pyramid have so that you can 1768 01:22:31,020 --> 01:22:32,666 fit them into a cube? 1769 01:22:32,666 --> 01:22:33,916 Hmm. 1770 01:22:38,940 --> 01:22:40,550 How about that shape? 1771 01:22:40,550 --> 01:22:43,410 So what's special about that shape? 1772 01:22:43,410 --> 01:22:46,440 I'll put one here, and here's another one of them. 1773 01:22:49,800 --> 01:22:51,240 Put that there. 1774 01:22:55,100 --> 01:22:56,350 And here's another one. 1775 01:23:08,330 --> 01:23:09,100 OK. 1776 01:23:09,100 --> 01:23:10,170 So here we go. 1777 01:23:10,170 --> 01:23:12,910 Here's a cube with six of those pyramids. 1778 01:23:12,910 --> 01:23:16,431 So what's special about the shape of the pyramid? 1779 01:23:16,431 --> 01:23:18,350 What do you have to set in it? 1780 01:23:18,350 --> 01:23:18,750 Yeah. 1781 01:23:18,750 --> 01:23:21,940 AUDIENCE: The height is half of the base line. 1782 01:23:21,940 --> 01:23:22,210 PROFESSOR: OK. 1783 01:23:22,210 --> 01:23:23,220 The height is half the base. 1784 01:23:23,220 --> 01:23:23,870 How do you know that? 1785 01:23:23,870 --> 01:23:28,400 AUDIENCE: Because the tips of the pyramids are [INAUDIBLE]. 1786 01:23:28,400 --> 01:23:28,750 PROFESSOR: Right. 1787 01:23:28,750 --> 01:23:30,440 So the tips touch like this. 1788 01:23:30,440 --> 01:23:35,550 And this width has to equal either side of the square. 1789 01:23:35,550 --> 01:23:48,520 That means, let's say, if h equals 1 and B equals 2, six 1790 01:23:48,520 --> 01:23:50,395 times the volume is equal to the volume of the 1791 01:23:50,395 --> 01:23:52,240 cube, which is 8. 1792 01:23:52,240 --> 01:23:56,370 So the volume of one pyramid is 8/6 or 4/3. 1793 01:23:56,370 --> 01:24:02,020 h times b squared is 4, so you have to divide it by 3, and 1794 01:24:02,020 --> 01:24:03,220 you're home free. 1795 01:24:03,220 --> 01:24:06,550 So there's an example of a demonstration in math class 1796 01:24:06,550 --> 01:24:08,410 that you can use. 1797 01:24:08,410 --> 01:24:14,340 Now the point of it is that it's possible to imagine it in 1798 01:24:14,340 --> 01:24:17,230 your head, but it is actually useful to see these things 1799 01:24:17,230 --> 01:24:20,620 built into a cube. 1800 01:24:20,620 --> 01:24:23,140 So even in math class you can do demonstrations. 1801 01:24:30,220 --> 01:24:32,350 What's my blackboard philosophy? 1802 01:24:32,350 --> 01:24:35,130 I write big and sometimes place things fairly randomly. 1803 01:24:35,130 --> 01:24:37,050 Is there a specific reason for this? 1804 01:24:37,050 --> 01:24:39,760 But I like what you write down. 1805 01:24:39,760 --> 01:24:40,030 Yeah. 1806 01:24:40,030 --> 01:24:42,470 My blackboard philosophy is not ideal, 1807 01:24:42,470 --> 01:24:44,880 because of exactly that. 1808 01:24:44,880 --> 01:24:47,870 I write large, which is good, but I do place things kind of 1809 01:24:47,870 --> 01:24:48,990 randomly sometimes. 1810 01:24:48,990 --> 01:24:53,870 And that's not ideal, so I try to improve that. 1811 01:24:53,870 --> 01:24:57,330 I don't necessarily have a reason for that. 1812 01:24:57,330 --> 01:25:00,700 Don't actually copy that part of my blackboard style. 1813 01:25:00,700 --> 01:25:02,650 But it's good that you're observing that and trying to 1814 01:25:02,650 --> 01:25:04,710 criticize it. 1815 01:25:04,710 --> 01:25:05,550 OK. 1816 01:25:05,550 --> 01:25:06,750 Let's see. 1817 01:25:06,750 --> 01:25:08,840 How to practice blackboard work. 1818 01:25:08,840 --> 01:25:10,240 We'll talk about that more today. 1819 01:25:10,240 --> 01:25:13,990 But the basic simplest way that I've found is at the end 1820 01:25:13,990 --> 01:25:17,080 of your session you just go to the back of the room and look 1821 01:25:17,080 --> 01:25:21,310 at the blackboard and you just see was it organized, did it 1822 01:25:21,310 --> 01:25:24,110 make sense, did I write a bunch of stuff in between, and 1823 01:25:24,110 --> 01:25:26,520 just take a few notes down on that. 1824 01:25:26,520 --> 01:25:28,650 And then you'll automatically be getting feedback that you 1825 01:25:28,650 --> 01:25:30,490 can use to improve your blackboard work. 1826 01:25:35,530 --> 01:25:36,110 Oh, yeah. 1827 01:25:36,110 --> 01:25:39,010 Several people pointed out they watched a different 1828 01:25:39,010 --> 01:25:41,410 lecture than Walter Lewin's Lecture 10, because I said, 1829 01:25:41,410 --> 01:25:43,190 oh, watch that one or another one. 1830 01:25:43,190 --> 01:25:45,470 So next year, I actually am going to ask everyone to watch 1831 01:25:45,470 --> 01:25:47,420 the same lecture, Lecture 10. 1832 01:25:47,420 --> 01:25:48,670 That's a good suggestion. 1833 01:25:51,090 --> 01:25:53,330 OK. 1834 01:25:53,330 --> 01:25:55,090 We talked about that. 1835 01:25:59,350 --> 01:26:02,260 Oh, yeah, if you're an excellent lecturer and you are 1836 01:26:02,260 --> 01:26:04,960 aware of the common problems, because you've taught the 1837 01:26:04,960 --> 01:26:07,430 course many times before, and you try to address all the 1838 01:26:07,430 --> 01:26:12,280 confusing parts, can you get away with not allowing 1839 01:26:12,280 --> 01:26:15,360 students to ask questions in class and not asking students 1840 01:26:15,360 --> 01:26:17,000 questions yourself? 1841 01:26:17,000 --> 01:26:19,030 That's a very interesting question. 1842 01:26:19,030 --> 01:26:21,620 Basically, can you move away from the interactive model 1843 01:26:21,620 --> 01:26:24,310 I've been describing and recommending once you've done 1844 01:26:24,310 --> 01:26:25,620 it enough and you know where the students' 1845 01:26:25,620 --> 01:26:27,470 misconceptions are. 1846 01:26:27,470 --> 01:26:29,590 I thought about that, and the answer is really no. 1847 01:26:29,590 --> 01:26:35,860 Because then you're reverting back to telling. 1848 01:26:35,860 --> 01:26:38,300 Now you're telling them things they really do need to know. 1849 01:26:38,300 --> 01:26:40,640 So instead of telling them a big long song and dance about 1850 01:26:40,640 --> 01:26:43,680 the Atwood machine, which they don't really need to know, 1851 01:26:43,680 --> 01:26:45,440 you're telling them about their misconceptions 1852 01:26:45,440 --> 01:26:46,890 about F equals ma. 1853 01:26:46,890 --> 01:26:50,200 But the problem is just telling them that F equals ma, 1854 01:26:50,200 --> 01:26:52,990 F equals mv, doesn't help them realize that. 1855 01:26:52,990 --> 01:26:55,720 They really have to have some kind of cognitive conflict and 1856 01:26:55,720 --> 01:26:56,820 struggle with it. 1857 01:26:56,820 --> 01:27:02,210 So questioning, either you question them or them asking 1858 01:27:02,210 --> 01:27:04,980 questions of you and formulating questions, is 1859 01:27:04,980 --> 01:27:07,390 really about the only way to get them to struggle with it. 1860 01:27:07,390 --> 01:27:09,770 Even then, you still have to do it. 1861 01:27:09,770 --> 01:27:12,230 And the experience you have from teaching it many times 1862 01:27:12,230 --> 01:27:14,700 means you'll be doing questions about useful, 1863 01:27:14,700 --> 01:27:16,390 important material. 1864 01:27:16,390 --> 01:27:20,255 That was quite an interesting question. 1865 01:27:20,255 --> 01:27:21,505 OK. 1866 01:27:27,340 --> 01:27:29,820 What do I think of group assignments, balancing the 1867 01:27:29,820 --> 01:27:34,030 advantages of collaboration with the fact that each 1868 01:27:34,030 --> 01:27:36,280 individual may not encounter all the topics? 1869 01:27:36,280 --> 01:27:38,900 I generally don't like them that much. 1870 01:27:38,900 --> 01:27:42,380 I think if you design a course and you think there's a 1871 01:27:42,380 --> 01:27:45,580 coherent set of material, everyone really should try to 1872 01:27:45,580 --> 01:27:48,740 master that coherent set of material and not palm off half 1873 01:27:48,740 --> 01:27:50,320 of it on one person in the group and the other 1874 01:27:50,320 --> 01:27:51,330 person in the group. 1875 01:27:51,330 --> 01:27:55,010 The extreme of this kind is the graduate seminar where 1876 01:27:55,010 --> 01:27:58,280 each graduate student gives a talk on one topic. 1877 01:27:58,280 --> 01:28:00,250 And then they really learn that one topic, but they don't 1878 01:28:00,250 --> 01:28:03,110 necessarily learn the other topics very well. 1879 01:28:03,110 --> 01:28:04,840 So I don't like that very much. 1880 01:28:04,840 --> 01:28:07,460 I think it's better to allow people to collaborate, but 1881 01:28:07,460 --> 01:28:09,862 make sure everyone does their own assignment. 1882 01:28:09,862 --> 01:28:12,720 And yeah, collaborate in groups, by all means, but 1883 01:28:12,720 --> 01:28:14,410 please write up your own work as well. 1884 01:28:22,490 --> 01:28:25,420 What's the use of experiments in Walter Lewin's lecture? 1885 01:28:25,420 --> 01:28:28,070 Was it to show the predictive power physics or its 1886 01:28:28,070 --> 01:28:29,180 experimental character? 1887 01:28:29,180 --> 01:28:29,770 It's not clear. 1888 01:28:29,770 --> 01:28:31,930 And in that case, wouldn't it be better if the students 1889 01:28:31,930 --> 01:28:35,090 performed the experiments on their own or in a lab class? 1890 01:28:35,090 --> 01:28:37,130 Aren't these demonstrations a waste of time that could be 1891 01:28:37,130 --> 01:28:38,710 used to teach more theory? 1892 01:28:38,710 --> 01:28:40,470 And aren't shows more appropriate for high school 1893 01:28:40,470 --> 01:28:42,500 classes than for physics at MIT? 1894 01:28:42,500 --> 01:28:46,460 Well, I think, at the time, this was 1999, there was no 1895 01:28:46,460 --> 01:28:50,820 laboratory with the introductory physics course. 1896 01:28:50,820 --> 01:28:52,760 I need to get my history right, but I'm pretty sure 1897 01:28:52,760 --> 01:28:54,160 that's right. 1898 01:28:54,160 --> 01:28:56,650 There was no other way the students would ever see any 1899 01:28:56,650 --> 01:28:57,720 application. 1900 01:28:57,720 --> 01:29:00,150 But the other main point of it is that it showed that the 1901 01:29:00,150 --> 01:29:01,850 physics is real. 1902 01:29:01,850 --> 01:29:04,340 Now I think it could be improved, as you suggested, by 1903 01:29:04,340 --> 01:29:06,270 Lewin asking students questions about the 1904 01:29:06,270 --> 01:29:09,670 experiments, trying to predict what would happen beforehand, 1905 01:29:09,670 --> 01:29:10,480 for example. 1906 01:29:10,480 --> 01:29:14,190 But the idea of bringing in objects is really a sound one. 1907 01:29:14,190 --> 01:29:17,110 I had a teacher at Caltech. 1908 01:29:17,110 --> 01:29:21,480 He taught the waves and the nonlinear waves course. 1909 01:29:21,480 --> 01:29:26,620 He always used to bring in a wave guide, which is, 1910 01:29:26,620 --> 01:29:30,400 basically, a piece of metal in a tube-like shape. 1911 01:29:30,400 --> 01:29:32,800 and he said he always did that because, otherwise, the 1912 01:29:32,800 --> 01:29:35,560 mathematicians would think it's just a vessel function, 1913 01:29:35,560 --> 01:29:37,640 because that's how it is in all the problems. 1914 01:29:37,640 --> 01:29:40,650 You see wave guide, you just start solving Laplace's 1915 01:29:40,650 --> 01:29:42,250 equation with all these boundary conditions, you get 1916 01:29:42,250 --> 01:29:43,190 Bessel function. 1917 01:29:43,190 --> 01:29:46,320 And wave guide is just trigger for do Laplace's equation, get 1918 01:29:46,320 --> 01:29:46,870 Bessel function. 1919 01:29:46,870 --> 01:29:48,390 It has no physical meaning. 1920 01:29:48,390 --> 01:29:50,515 So he would always bring in the wave guide so that you 1921 01:29:50,515 --> 01:29:52,740 knew that it was a real object that you were analyzing. 1922 01:29:52,740 --> 01:29:55,400 And so in that way, Lewin, using the pendulum, showing 1923 01:29:55,400 --> 01:29:59,350 that these things actually exist, avoids the trap that 1924 01:29:59,350 --> 01:30:02,490 many students fall into, which is that symbols just have no 1925 01:30:02,490 --> 01:30:03,580 meaning on their own. 1926 01:30:03,580 --> 01:30:06,180 They're just stuff that goes on on the screen. 1927 01:30:06,180 --> 01:30:10,350 So I think is really important that he does that. 1928 01:30:10,350 --> 01:30:13,120 OK. 1929 01:30:13,120 --> 01:30:14,590 Working hard versus smart. 1930 01:30:14,590 --> 01:30:16,660 How do you respond to people who tell you that they worked 1931 01:30:16,660 --> 01:30:18,190 really hard but they still did poorly? 1932 01:30:21,400 --> 01:30:22,700 I think, basically, the reason is that 1933 01:30:22,700 --> 01:30:26,100 they didn't work smart. 1934 01:30:26,100 --> 01:30:28,360 So what do students think working hard means? 1935 01:30:28,360 --> 01:30:30,690 They generally think it means reading the book over and over 1936 01:30:30,690 --> 01:30:34,500 again or trying really hard to do the problems but not 1937 01:30:34,500 --> 01:30:37,005 reflecting. 1938 01:30:37,005 --> 01:30:39,430 The equivalent in playing chess is working hard at 1939 01:30:39,430 --> 01:30:41,420 chess, people think, oh, that just means playing lots of 1940 01:30:41,420 --> 01:30:41,970 chess games. 1941 01:30:41,970 --> 01:30:44,620 But actually, that doesn't improve your chess ability. 1942 01:30:44,620 --> 01:30:47,250 You have to analyze your chess games, reflect on them. 1943 01:30:47,250 --> 01:30:49,730 And that's what we need to teach students how to do. 1944 01:30:49,730 --> 01:30:51,440 So whenever they do say that, I say, OK, well, 1945 01:30:51,440 --> 01:30:52,620 what are you doing? 1946 01:30:52,620 --> 01:30:54,245 Let's look at what you're doing and see if there are 1947 01:30:54,245 --> 01:30:57,530 ways we can make it more reflective and less just going 1948 01:30:57,530 --> 01:30:59,070 through the same stuff over and over again. 1949 01:31:03,850 --> 01:31:05,540 And then, final comment-- 1950 01:31:05,540 --> 01:31:06,750 there are some more questions, but I'll leave 1951 01:31:06,750 --> 01:31:07,650 it there for now-- 1952 01:31:07,650 --> 01:31:10,820 while watching the 801 Walter Lewin lecture, I was surprised 1953 01:31:10,820 --> 01:31:13,680 how much I was able to find wrong with it, even though 1954 01:31:13,680 --> 01:31:14,510 he's a great lecturer. 1955 01:31:14,510 --> 01:31:16,590 That goes to show how much we've learned so far in this 1956 01:31:16,590 --> 01:31:20,070 class, which I thought was a very nice comment. 1957 01:31:20,070 --> 01:31:21,150 I'm glad. 1958 01:31:21,150 --> 01:31:23,860 And I hope people did draw that conclusion. 1959 01:31:23,860 --> 01:31:27,190 From all this stuff that you found to improve that lecture 1960 01:31:27,190 --> 01:31:29,500 means you have actually learned a lot, either in this 1961 01:31:29,500 --> 01:31:31,960 class or elsewhere, and you could actually make really 1962 01:31:31,960 --> 01:31:35,310 excellent lecturers, really powerful, constructive 1963 01:31:35,310 --> 01:31:36,560 lecturers yourself.