1 00:00:16,300 --> 00:00:17,801 OK, let's do a why this matters. 2 00:00:17,801 --> 00:00:20,971 Let's do a why this matters. 3 00:00:20,971 --> 00:00:21,839 Why does this matter? 4 00:00:21,839 --> 00:00:25,409 Well, because, see, these guys were 5 00:00:25,409 --> 00:00:28,479 trying to figure out what was inside of an atom. 6 00:00:28,479 --> 00:00:31,181 But other people, like John Baird, 7 00:00:31,181 --> 00:00:32,249 said, well, wait a second. 8 00:00:32,249 --> 00:00:34,418 You just gave me a paintbrush. 9 00:00:34,418 --> 00:00:35,986 You gave me a paintbrush. 10 00:00:35,986 --> 00:00:36,920 Look at this. 11 00:00:36,920 --> 00:00:40,991 That's a paintbrush, painting with a magnet. 12 00:00:40,991 --> 00:00:41,692 It really is. 13 00:00:41,692 --> 00:00:43,927 And the screen would light up over here. 14 00:00:43,927 --> 00:00:46,730 And so he said, well, I can paint. 15 00:00:46,730 --> 00:00:48,532 I can paint pictures. 16 00:00:48,532 --> 00:00:51,268 And this really is the first television screen. 17 00:00:51,268 --> 00:00:54,338 This was the first TV screen, and all they 18 00:00:54,338 --> 00:00:55,506 needed to do, there-- 19 00:00:55,506 --> 00:00:58,475 OK, right? 20 00:00:58,475 --> 00:00:59,243 There it is. 21 00:00:59,243 --> 00:00:59,743 Look! 22 00:00:59,743 --> 00:01:02,413 That's a cathode ray tube. 23 00:01:02,413 --> 00:01:07,618 Maybe that's one of Thomson's students who won a Nobel Prize. 24 00:01:07,618 --> 00:01:10,187 And but now, you put this down, and you put 25 00:01:10,187 --> 00:01:11,488 these sort of things around it. 26 00:01:11,488 --> 00:01:12,589 What are those things? 27 00:01:12,589 --> 00:01:14,892 Magnetic fields, that's all it is. 28 00:01:14,892 --> 00:01:16,026 It's just magnetic fields. 29 00:01:16,026 --> 00:01:18,262 It's Thomson's experiments, right? 30 00:01:18,262 --> 00:01:23,734 But now they're using it to zip the beam around 31 00:01:23,734 --> 00:01:26,437 faster than you're [INAUDIBLE] keep up with so 32 00:01:26,437 --> 00:01:27,670 that it looks like a picture. 33 00:01:27,670 --> 00:01:31,275 Now, electron painting had never been done before, 34 00:01:31,275 --> 00:01:35,212 because we didn't know that we had these electrons. 35 00:01:35,212 --> 00:01:37,481 But as soon as we knew, boy, did that 36 00:01:37,481 --> 00:01:42,386 launch a completely new era of screens. 37 00:01:42,386 --> 00:01:42,886 Right? 38 00:01:42,886 --> 00:01:44,588 The era of screens. 39 00:01:44,588 --> 00:01:46,523 We don't use cathode ray tubes. 40 00:01:46,523 --> 00:01:48,292 I was going to say, ask your grandparents. 41 00:01:48,292 --> 00:01:50,094 They'll tell you about the cathode ray tube 42 00:01:50,094 --> 00:01:54,031 TVs, which they all had. 43 00:01:54,031 --> 00:01:57,501 But you know, we don't use cathode ray tubes 44 00:01:57,501 --> 00:02:00,504 to paint with electrons today in that way, 45 00:02:00,504 --> 00:02:03,540 but we still paint with electrons today. 46 00:02:03,540 --> 00:02:04,208 Right? 47 00:02:04,208 --> 00:02:07,544 Youre OLED screen is still simply 48 00:02:07,544 --> 00:02:12,182 an electron-based painting tool, right? 49 00:02:12,182 --> 00:02:13,817 OK, we're just pumping the electrons 50 00:02:13,817 --> 00:02:16,887 into the phosphor in a different way, 51 00:02:16,887 --> 00:02:19,089 and we'll be talking about that as we 52 00:02:19,089 --> 00:02:21,158 go through the rest of this week and we understand 53 00:02:21,158 --> 00:02:23,861 how electrons interact with light 54 00:02:23,861 --> 00:02:26,563 coming in and out of an atom. 55 00:02:26,563 --> 00:02:29,299 OK, so that's my why this matters. 56 00:02:29,299 --> 00:02:31,034 And by the way, a side note here is 57 00:02:31,034 --> 00:02:36,906 that when TVs first came along, green was pretty easy. 58 00:02:36,906 --> 00:02:40,577 There were a lot of chemistries that were used for this screen. 59 00:02:40,577 --> 00:02:42,179 You put a different chemistry here, 60 00:02:42,179 --> 00:02:45,649 and it lights up differently when electrons hit it. 61 00:02:45,649 --> 00:02:46,283 Why? 62 00:02:46,283 --> 00:02:49,219 Wait until Wednesday. 63 00:02:49,219 --> 00:02:50,353 Green was easy. 64 00:02:50,353 --> 00:02:51,054 Yellow was easy. 65 00:02:51,054 --> 00:02:52,222 Red was hard. 66 00:02:52,222 --> 00:02:53,524 Red was hard. 67 00:02:53,524 --> 00:02:55,225 They couldn't get a good red. 68 00:02:55,225 --> 00:03:00,330 And of course, that's essentially the reason 69 00:03:00,330 --> 00:03:04,735 there were no color TVs until the '60s, right? 70 00:03:04,735 --> 00:03:07,104 And the answer, of course, was here. 71 00:03:07,104 --> 00:03:10,607 The answer was that there was a phosphor that worked, 72 00:03:10,607 --> 00:03:14,912 but it was yttrium orthovanadate with a little bit of europium 73 00:03:14,912 --> 00:03:16,747 added to it. 74 00:03:16,747 --> 00:03:17,981 Just a little bit of europium. 75 00:03:17,981 --> 00:03:18,849 Why did that work? 76 00:03:18,849 --> 00:03:21,685 Again, we need to understand how electrons interact with matter, 77 00:03:21,685 --> 00:03:23,921 which is where we're going. 78 00:03:23,921 --> 00:03:28,025 And speaking of yttrium, speaking of yttrium, 79 00:03:28,025 --> 00:03:30,928 this is also a side story, but it's kind of worth noting. 80 00:03:30,928 --> 00:03:33,764 You know, elements are named often-- well, 81 00:03:33,764 --> 00:03:36,333 elements can be named after many things, right? 82 00:03:36,333 --> 00:03:40,003 In this case, it was named after Ytterby, Sweden. 83 00:03:40,003 --> 00:03:42,272 Ytterby, Sweden, is a pretty cool place. 84 00:03:42,272 --> 00:03:44,274 They had this one cave. 85 00:03:44,274 --> 00:03:45,509 You got to go to it. 86 00:03:45,509 --> 00:03:49,046 It's really cool, because four elements of the periodic table 87 00:03:49,046 --> 00:03:51,515 were all discovered from Ytterby, Sweden, 88 00:03:51,515 --> 00:03:53,684 in this one cave. 89 00:03:53,684 --> 00:03:54,518 Four! 90 00:03:54,518 --> 00:03:56,720 And I keep thinking, where is that cave in Cambridge? 91 00:03:56,720 --> 00:03:58,255 [LAUGHTER] 92 00:03:58,255 --> 00:03:59,856 Hm? 93 00:03:59,856 --> 00:04:01,725 They cannot discover any more elements, 94 00:04:01,725 --> 00:04:05,062 because there's no other way to mess with the name Ytterby. 95 00:04:05,062 --> 00:04:06,997 [LAUGHTER] 96 00:04:06,997 --> 00:04:09,967 That's pretty cool. 97 00:04:09,967 --> 00:04:10,767 That's pretty cool. 98 00:04:10,767 --> 00:04:12,669 That's a cool cave. 99 00:04:12,669 --> 00:04:13,971 That's worth visiting.