1 00:00:00,060 --> 00:00:02,430 The following content is provided under a Creative 2 00:00:02,430 --> 00:00:03,820 Commons license. 3 00:00:03,820 --> 00:00:06,030 Your support will help MIT OpenCourseWare 4 00:00:06,030 --> 00:00:10,120 continue to offer high quality educational resources for free. 5 00:00:10,120 --> 00:00:12,660 To make a donation or to view additional materials 6 00:00:12,660 --> 00:00:16,620 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:16,620 --> 00:00:17,650 at ocw.mit.edu. 8 00:00:20,290 --> 00:00:22,580 AUDIENCE: The light comes from the bulb. 9 00:00:22,580 --> 00:00:26,490 And it goes into the mirror, and it bounces over to the paper. 10 00:00:26,490 --> 00:00:29,460 So that's how you can see the reflection of the words 11 00:00:29,460 --> 00:00:30,937 on the paper. 12 00:00:30,937 --> 00:00:31,520 PROFESSOR: OK. 13 00:00:31,520 --> 00:00:32,780 Very nice. 14 00:00:32,780 --> 00:00:36,650 So in astronomy, whenever we're dealing with something 15 00:00:36,650 --> 00:00:38,810 making images, which we're going to use 16 00:00:38,810 --> 00:00:40,130 telescopes to make images. 17 00:00:40,130 --> 00:00:42,320 We're also going to use cameras to make images, 18 00:00:42,320 --> 00:00:44,790 there's always three important parts. 19 00:00:44,790 --> 00:00:47,540 One is the source of light, whether that's 20 00:00:47,540 --> 00:00:50,870 a star or a planet or a light bulb or something that 21 00:00:50,870 --> 00:00:52,130 produces light. 22 00:00:52,130 --> 00:00:54,620 You also have to have a reflector, 23 00:00:54,620 --> 00:00:57,740 or a mirror, that takes that light, 24 00:00:57,740 --> 00:01:00,020 reflects it, but also focuses the light, 25 00:01:00,020 --> 00:01:02,090 kind of pulls it together. 26 00:01:02,090 --> 00:01:05,720 And then that is the light bounces off the reflector 27 00:01:05,720 --> 00:01:07,900 and then goes to the detector. 28 00:01:07,900 --> 00:01:10,340 So I'm going to hold this up for you. 29 00:01:10,340 --> 00:01:13,070 This is your detector, right? 30 00:01:13,070 --> 00:01:15,950 And the reason that we put all these little squares on it 31 00:01:15,950 --> 00:01:20,480 is because real detectors, which we call CCDs or charge coupled 32 00:01:20,480 --> 00:01:25,130 devices, are really little pieces of silicon 33 00:01:25,130 --> 00:01:28,100 which have a bunch of these little squares 34 00:01:28,100 --> 00:01:29,600 kind of drawn on them. 35 00:01:29,600 --> 00:01:32,780 Silicon is an element, and it's particularly 36 00:01:32,780 --> 00:01:34,460 sensitive to light. 37 00:01:34,460 --> 00:01:37,010 And so we're going to see that in a real telescope 38 00:01:37,010 --> 00:01:41,090 when light hits a particular place on this detector, 39 00:01:41,090 --> 00:01:43,524 the detector records where the light came in. 40 00:01:43,524 --> 00:01:44,690 Just like what you did here. 41 00:01:44,690 --> 00:01:47,720 You made the image project over here. 42 00:01:47,720 --> 00:01:50,630 So everybody kind of gathers around. 43 00:01:50,630 --> 00:01:52,850 I do have-- and Peter if you could pull up 44 00:01:52,850 --> 00:01:55,174 the close up image of the detector. 45 00:01:55,174 --> 00:01:56,090 Maybe put it up there. 46 00:01:56,090 --> 00:01:58,520 I want everybody to come over here to table three, 47 00:01:58,520 --> 00:01:59,180 or table four. 48 00:01:59,180 --> 00:02:00,640 Four, I'm sorry. 49 00:02:00,640 --> 00:02:04,160 And I have an actual CCD that was 50 00:02:04,160 --> 00:02:06,080 on the back of some of the telescopes, 51 00:02:06,080 --> 00:02:08,014 and I'll let you guys just take it. 52 00:02:08,014 --> 00:02:10,454 Can we turn the lights up? 53 00:02:10,454 --> 00:02:12,620 This is actually one of the CCDs from the telescopes 54 00:02:12,620 --> 00:02:13,530 that we're going to use. 55 00:02:13,530 --> 00:02:15,571 We're going to use some visible light telescopes. 56 00:02:15,571 --> 00:02:17,450 If you look really closely, can you 57 00:02:17,450 --> 00:02:20,390 see the little tiny squares? 58 00:02:20,390 --> 00:02:22,430 What do you think? 59 00:02:22,430 --> 00:02:23,959 They're pretty small, right? 60 00:02:23,959 --> 00:02:25,250 They're actually-- what's that? 61 00:02:25,250 --> 00:02:26,960 AUDIENCE: Is that nanotechnology? 62 00:02:26,960 --> 00:02:28,010 PROFESSOR: Not quite. 63 00:02:28,010 --> 00:02:32,085 So these squares are a couple of micro-- not micrometers. 64 00:02:32,085 --> 00:02:32,960 Are they micrometers? 65 00:02:32,960 --> 00:02:34,610 I think they are a couple of microns. 66 00:02:34,610 --> 00:02:38,404 So they are a couple of millionths of an inch across. 67 00:02:38,404 --> 00:02:39,570 So they're very, very small. 68 00:02:39,570 --> 00:02:40,890 So you can't really see that. 69 00:02:40,890 --> 00:02:44,540 But if you look up on the board, yeah 70 00:02:44,540 --> 00:02:46,860 I guess you have to go kind of closer to the screen. 71 00:02:46,860 --> 00:02:48,110 Take a look at the screen. 72 00:02:48,110 --> 00:02:51,530 On the bottom half, this is the edge of one of those detectors. 73 00:02:51,530 --> 00:02:54,882 On the top half, that's the actual detector part. 74 00:02:54,882 --> 00:02:56,340 So what happened with this detector 75 00:02:56,340 --> 00:02:58,190 was the bottom part kind of short circuited, 76 00:02:58,190 --> 00:03:01,430 and it blew out, which is why you see the weird kind of stuff 77 00:03:01,430 --> 00:03:02,070 there. 78 00:03:02,070 --> 00:03:04,700 But if you look right up here, what 79 00:03:04,700 --> 00:03:07,310 do you see if we've zoomed in a lot? 80 00:03:07,310 --> 00:03:08,980 [INTERPOSING VOICES] 81 00:03:08,980 --> 00:03:12,340 Some yellow stuff, what shape? 82 00:03:12,340 --> 00:03:13,960 They look like little squares. 83 00:03:13,960 --> 00:03:15,710 So on that little tiny thing that's, like, 84 00:03:15,710 --> 00:03:17,510 a few millimeters by a few millimeters, 85 00:03:17,510 --> 00:03:19,430 instead of having a big detector like you had, 86 00:03:19,430 --> 00:03:24,050 like 8 1/2 by 11 inches, most astronomical telescopes focus 87 00:03:24,050 --> 00:03:26,600 their light down onto a tiny little chip. 88 00:03:26,600 --> 00:03:29,570 And each one of those squares is sensitive to light. 89 00:03:29,570 --> 00:03:32,595 And that's how we detect light and we make it into an image. 90 00:03:32,595 --> 00:03:34,970 We're going to talk a little bit more about this process, 91 00:03:34,970 --> 00:03:37,340 but I just wanted you to be a little bit familiar 92 00:03:37,340 --> 00:03:39,620 with the idea of projecting an image 93 00:03:39,620 --> 00:03:42,230 and then projecting it to a certain place in space, 94 00:03:42,230 --> 00:03:46,452 like we're going to project onto that small piece of silicon. 95 00:03:46,452 --> 00:03:48,410 So what we're going to do now is we're actually 96 00:03:48,410 --> 00:03:54,125 going to use some images to learn about sizes. 97 00:03:54,125 --> 00:03:56,470 So we need you to take your notes, 98 00:03:56,470 --> 00:04:00,260 and I want you to head back over to your computer table. 99 00:04:00,260 --> 00:04:03,260 What did we decide were the important quantities that 100 00:04:03,260 --> 00:04:07,220 helped us decide what size or what width something looked 101 00:04:07,220 --> 00:04:08,420 in the image? 102 00:04:08,420 --> 00:04:11,750 What can we change when we take pictures of something 103 00:04:11,750 --> 00:04:17,570 to make to make Mars or to make the guy in the tire 104 00:04:17,570 --> 00:04:19,860 look a different size? 105 00:04:19,860 --> 00:04:21,200 What are important quantities? 106 00:04:21,200 --> 00:04:22,507 Go ahead Bianca. 107 00:04:22,507 --> 00:04:23,090 Nice and loud. 108 00:04:23,090 --> 00:04:24,080 AUDIENCE: Perspective. 109 00:04:24,080 --> 00:04:25,040 PROFESSOR: Perspective. 110 00:04:25,040 --> 00:04:25,540 OK. 111 00:04:25,540 --> 00:04:27,410 What does that have to do with? 112 00:04:27,410 --> 00:04:29,270 AUDIENCE: Where you're taking the picture. 113 00:04:29,270 --> 00:04:31,061 PROFESSOR: Where you're taking the picture. 114 00:04:31,061 --> 00:04:31,680 So David? 115 00:04:31,680 --> 00:04:33,940 AUDIENCE: [INAUDIBLE] 116 00:04:33,940 --> 00:04:35,294 PROFESSOR: OK, go ahead. 117 00:04:35,294 --> 00:04:36,500 AUDIENCE: Magnification. 118 00:04:36,500 --> 00:04:37,190 PROFESSOR: OK. 119 00:04:37,190 --> 00:04:39,170 So magnification. 120 00:04:39,170 --> 00:04:41,087 We're not going to use the zoom on our camera, 121 00:04:41,087 --> 00:04:43,586 so we're actually not going to deal with that for right now. 122 00:04:43,586 --> 00:04:45,240 We're just taking the picture. 123 00:04:45,240 --> 00:04:46,860 So as [INAUDIBLE] said, perspective. 124 00:04:46,860 --> 00:04:48,822 What does that mean? 125 00:04:48,822 --> 00:04:50,280 AUDIENCE: Different angles. 126 00:04:50,280 --> 00:04:51,110 PROFESSOR: OK. 127 00:04:51,110 --> 00:04:53,190 Different angles. 128 00:04:53,190 --> 00:04:55,910 So we could take a picture from the side or from the front. 129 00:04:55,910 --> 00:04:57,393 [? Lauren, ?] you had your hand up? 130 00:04:57,393 --> 00:05:01,340 AUDIENCE: I was gonna say distance is important. 131 00:05:01,340 --> 00:05:02,460 PROFESSOR: OK. 132 00:05:02,460 --> 00:05:04,780 Is distance important? 133 00:05:04,780 --> 00:05:05,280 OK. 134 00:05:05,280 --> 00:05:08,982 What does distance have to do with perspective? 135 00:05:08,982 --> 00:05:12,000 AUDIENCE: Closer you-- the closer you are, 136 00:05:12,000 --> 00:05:13,650 the larger something appears. 137 00:05:13,650 --> 00:05:14,350 PROFESSOR: OK. 138 00:05:14,350 --> 00:05:16,720 So the distance from your detector 139 00:05:16,720 --> 00:05:18,910 or your camera to the object. 140 00:05:18,910 --> 00:05:23,080 Here, we said the tire is closer to the camera. 141 00:05:23,080 --> 00:05:25,900 There, you said the car is closer to the camera. 142 00:05:25,900 --> 00:05:28,660 Here, we said the-- 143 00:05:28,660 --> 00:05:31,160 well there, we said the sun is bigger than it really is, 144 00:05:31,160 --> 00:05:31,660 right? 145 00:05:31,660 --> 00:05:33,880 So you've got the distance to the object, 146 00:05:33,880 --> 00:05:35,890 but what is something else that affects how 147 00:05:35,890 --> 00:05:37,090 something looks in an image? 148 00:05:40,260 --> 00:05:40,930 Go ahead, Nikki. 149 00:05:40,930 --> 00:05:43,030 AUDIENCE: The right position that you're 150 00:05:43,030 --> 00:05:45,597 in, I guess it matters. 151 00:05:45,597 --> 00:05:46,180 PROFESSOR: OK. 152 00:05:46,180 --> 00:05:50,170 The position of the object or the relative position 153 00:05:50,170 --> 00:05:51,640 between the two objects. 154 00:05:51,640 --> 00:05:52,390 Yeah. 155 00:05:52,390 --> 00:05:54,766 So it matters, in this case, if we're 156 00:05:54,766 --> 00:05:56,140 looking at two different objects, 157 00:05:56,140 --> 00:05:58,015 it's the distance to both of the objects that 158 00:05:58,015 --> 00:05:59,200 makes a difference. 159 00:05:59,200 --> 00:06:00,760 We're actually going to just have you look at the distance 160 00:06:00,760 --> 00:06:02,259 to one object here in a minute, just 161 00:06:02,259 --> 00:06:04,760 to make it a little bit simpler, right? 162 00:06:04,760 --> 00:06:06,304 But what else is important? 163 00:06:09,090 --> 00:06:11,630 Did you have your hand up, [INAUDIBLE]?? 164 00:06:11,630 --> 00:06:12,498 Go ahead, Chris. 165 00:06:12,498 --> 00:06:14,330 AUDIENCE: The actual size of something? 166 00:06:14,330 --> 00:06:14,913 PROFESSOR: OK. 167 00:06:14,913 --> 00:06:16,340 The actual size of something. 168 00:06:16,340 --> 00:06:21,140 We said if we put the toy car that has a small actual size-- 169 00:06:21,140 --> 00:06:23,910 or let's just say actual length of the car. 170 00:06:23,910 --> 00:06:26,750 If we put the toy car close, it looks 171 00:06:26,750 --> 00:06:32,220 like it's the same length as the car that's farther away. 172 00:06:32,220 --> 00:06:34,130 So those two things are really important. 173 00:06:34,130 --> 00:06:36,860 How far away something is, the distance to the object, 174 00:06:36,860 --> 00:06:39,080 And the actual width of the object 175 00:06:39,080 --> 00:06:41,580 or the actual height of the object. 176 00:06:41,580 --> 00:06:44,360 You have to match those up to make sure 177 00:06:44,360 --> 00:06:47,440 that you're getting things to look the same. 178 00:06:47,440 --> 00:06:48,990 So.