1 00:00:04,440 --> 00:00:10,440 Speaker 1: Welcome to tech Stuff, a production from iHeartRadio. 2 00:00:11,840 --> 00:00:12,680 Speaker 2: Hey there, and. 3 00:00:12,600 --> 00:00:16,480 Speaker 1: Welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm 4 00:00:16,520 --> 00:00:20,159 Speaker 1: an executive producer with iHeartRadio, and how the tech are you? 5 00:00:20,760 --> 00:00:23,680 Speaker 1: It is time for a tech Stuff classic episode. This 6 00:00:23,720 --> 00:00:27,960 Speaker 1: one is called How Magnetic Storage Works. It originally published 7 00:00:28,280 --> 00:00:34,680 Speaker 1: on January twenty fifth, two thousand and seventeen. So how 8 00:00:34,680 --> 00:00:38,440 Speaker 1: do you preserve information so that you can access it 9 00:00:38,479 --> 00:00:41,320 Speaker 1: again later? Cause in the old days, and I'm talking 10 00:00:41,440 --> 00:00:44,920 Speaker 1: like tens of thousands of years ago, verbal communication was 11 00:00:44,920 --> 00:00:47,760 Speaker 1: where it was at. You stored all that information up 12 00:00:47,760 --> 00:00:50,519 Speaker 1: in your head. Someone would tell you something important and 13 00:00:50,560 --> 00:00:52,879 Speaker 1: you had to remember it. Perhaps they would tell you 14 00:00:52,920 --> 00:00:57,520 Speaker 1: within the context of a story. And then eventually, if 15 00:00:57,560 --> 00:00:59,880 Speaker 1: you were trying to preserve information, you would tell that 16 00:01:00,040 --> 00:01:03,520 Speaker 1: same information to someone else and pass it along this way. 17 00:01:03,720 --> 00:01:09,640 Speaker 1: This is essentially folklore. That's how knowledge was maintained for centuries. 18 00:01:10,400 --> 00:01:11,880 Speaker 2: And then way back in the day. 19 00:01:11,760 --> 00:01:15,039 Speaker 1: Someone said, hey, what if we made up some symbols 20 00:01:15,080 --> 00:01:18,800 Speaker 1: to represent these sounds we're making to communicate with each other, 21 00:01:19,080 --> 00:01:21,000 Speaker 1: and then we put those symbols into some sort of 22 00:01:21,480 --> 00:01:26,560 Speaker 1: fixed format, like in a clay tablet, and that way, 23 00:01:26,800 --> 00:01:30,600 Speaker 1: we can preserve the information a lot longer. And if Bob, 24 00:01:30,840 --> 00:01:34,600 Speaker 1: who's really good at making fires, can explain how to 25 00:01:34,640 --> 00:01:37,920 Speaker 1: make fires, and we put it down in this format, 26 00:01:38,200 --> 00:01:40,560 Speaker 1: we'll be able to make fires even if Bob does 27 00:01:40,600 --> 00:01:43,880 Speaker 1: something stupid like walks off the edge of a cliff 28 00:01:43,959 --> 00:01:48,480 Speaker 1: or something. And writing was born. It probably went a 29 00:01:48,520 --> 00:01:50,520 Speaker 1: little differently from the way I explained it, but I 30 00:01:50,560 --> 00:01:53,400 Speaker 1: think I got the gist of it. Not everyone, however, 31 00:01:53,560 --> 00:01:56,120 Speaker 1: was a fan of this development. Believe it or not, 32 00:01:56,240 --> 00:01:59,640 Speaker 1: there were people who were against the whole idea of 33 00:01:59,720 --> 00:02:04,440 Speaker 1: right stuff down. Socrates was actually a critic of writing 34 00:02:04,440 --> 00:02:07,240 Speaker 1: stuff down, or at least that's what we hear, because 35 00:02:07,400 --> 00:02:12,080 Speaker 1: Socrates didn't write anything down, his students did. He said 36 00:02:12,120 --> 00:02:15,280 Speaker 1: that the written word is fixed, and therefore it can't 37 00:02:15,320 --> 00:02:19,680 Speaker 1: defend itself or any arguments it makes, so it's inherently flawed. 38 00:02:20,240 --> 00:02:23,680 Speaker 1: If someone writes down an argument and your access to 39 00:02:23,720 --> 00:02:27,120 Speaker 1: the argument is in that written format, and you have 40 00:02:27,280 --> 00:02:31,480 Speaker 1: questions or you have attacks on that argument, it can't 41 00:02:31,480 --> 00:02:34,360 Speaker 1: defend itself. The person who wrote it could if they 42 00:02:34,440 --> 00:02:37,440 Speaker 1: were there, but if they're not there, then the argument 43 00:02:37,480 --> 00:02:40,079 Speaker 1: has to stand on its own, and therefore it has 44 00:02:40,160 --> 00:02:46,080 Speaker 1: to be less effective, let's say, than an actual human being. 45 00:02:46,200 --> 00:02:48,040 Speaker 1: He also said that if you write stuff down, you 46 00:02:48,080 --> 00:02:50,440 Speaker 1: don't have to remember it yourself, and that makes you 47 00:02:50,520 --> 00:02:55,000 Speaker 1: less intelligent, because if you're not actually committing something to memory, 48 00:02:55,560 --> 00:03:00,560 Speaker 1: you're getting super dumb. This might sound a lot like 49 00:03:00,639 --> 00:03:02,880 Speaker 1: some of the arguments people have made about Google and 50 00:03:02,960 --> 00:03:07,160 Speaker 1: the Internet, and it's absolutely correct. Every single time we 51 00:03:07,280 --> 00:03:11,840 Speaker 1: have created a new way to permanently store data in 52 00:03:11,880 --> 00:03:16,520 Speaker 1: some form or another, people have brought up this idea 53 00:03:16,560 --> 00:03:20,399 Speaker 1: that it's making us more dumb. Like they might say, hey, 54 00:03:20,440 --> 00:03:22,400 Speaker 1: back in the day, you'd have to remember all your 55 00:03:22,440 --> 00:03:24,880 Speaker 1: phone numbers, like all the numbers of the friends and 56 00:03:24,919 --> 00:03:26,960 Speaker 1: family that you'd be calling on a regular basis. But 57 00:03:27,000 --> 00:03:28,720 Speaker 1: now it's all on your phone, so you don't remember it. 58 00:03:29,360 --> 00:03:31,880 Speaker 1: You may not be able to rattle off more than 59 00:03:31,919 --> 00:03:34,720 Speaker 1: two or three phone numbers today because of that, therefore 60 00:03:34,760 --> 00:03:38,040 Speaker 1: you are more dumb. I don't subscribe to that particular argument. 61 00:03:38,120 --> 00:03:42,720 Speaker 1: I think having the accessibility of information outweighs the fact 62 00:03:42,760 --> 00:03:45,160 Speaker 1: that we are no longer able to remember it necessarily. 63 00:03:46,160 --> 00:03:49,040 Speaker 1: The point I would make is that comprehension is always 64 00:03:49,080 --> 00:03:53,320 Speaker 1: more important than being able to recall something You might 65 00:03:53,360 --> 00:03:55,280 Speaker 1: be able to recall some information, but if you don't 66 00:03:55,280 --> 00:03:58,640 Speaker 1: truly comprehend it, it's of no use to you. So 67 00:03:59,320 --> 00:04:02,320 Speaker 1: I don't think it's necessarily a measure of intelligence. It's 68 00:04:02,320 --> 00:04:05,160 Speaker 1: certainly perhaps more of a statement about our memories than 69 00:04:05,160 --> 00:04:08,440 Speaker 1: anything else. But I'm getting off on a tangent here, 70 00:04:09,320 --> 00:04:13,480 Speaker 1: So I think the developments we've had have been phenomenal. 71 00:04:13,560 --> 00:04:14,560 Speaker 2: We wouldn't be where. 72 00:04:14,360 --> 00:04:17,400 Speaker 1: We are today if we were still depending upon just 73 00:04:17,520 --> 00:04:20,760 Speaker 1: telling each other the important stuff and hoping that they 74 00:04:20,760 --> 00:04:24,440 Speaker 1: would be able to then tell other people the important 75 00:04:24,440 --> 00:04:26,560 Speaker 1: stuff we just told them and in a way that 76 00:04:26,720 --> 00:04:31,160 Speaker 1: was accurate and effective. We clearly wouldn't be where we 77 00:04:31,200 --> 00:04:33,719 Speaker 1: are today if we still depended upon that. And I 78 00:04:33,760 --> 00:04:35,920 Speaker 1: don't have to travel all the way across the world 79 00:04:36,000 --> 00:04:38,599 Speaker 1: to find a specific guru to learn how to perform 80 00:04:38,680 --> 00:04:42,200 Speaker 1: a particular skill. I can just go onto YouTube and 81 00:04:42,640 --> 00:04:45,040 Speaker 1: watch like thirty or forty videos until I find one 82 00:04:45,040 --> 00:04:51,280 Speaker 1: that actually makes sense. So AD's progress take that, Socrates. Now, 83 00:04:51,279 --> 00:04:53,600 Speaker 1: throughout history, we saw many advances in the way we 84 00:04:53,640 --> 00:04:57,680 Speaker 1: store information, and as we developed more advanced technology, it 85 00:04:57,760 --> 00:05:00,560 Speaker 1: became clear that a compatible method of star scoring data 86 00:05:00,640 --> 00:05:04,359 Speaker 1: would be really handy. So imagine what computers would be 87 00:05:04,400 --> 00:05:07,560 Speaker 1: if they could not save information. They'd be practically useless. 88 00:05:07,600 --> 00:05:10,679 Speaker 1: You need to have a way of storing data somehow, 89 00:05:10,720 --> 00:05:14,680 Speaker 1: whether it's in magnetic storage, optical, solid state punch cards, whatever. 90 00:05:14,720 --> 00:05:19,520 Speaker 1: You need something that can record that information, otherwise it's 91 00:05:19,600 --> 00:05:22,239 Speaker 1: only good for a moment. And a lot of folks 92 00:05:22,279 --> 00:05:25,000 Speaker 1: worked on this problem, and as is the case with 93 00:05:25,120 --> 00:05:28,440 Speaker 1: many technological developments, some of that work had nothing to 94 00:05:28,480 --> 00:05:32,279 Speaker 1: do with computers, but more with researching fundamental scientific questions 95 00:05:32,760 --> 00:05:36,640 Speaker 1: and finding answers to questions led other people being able 96 00:05:36,720 --> 00:05:39,919 Speaker 1: to use that information in practical ways that we didn't anticipate. 97 00:05:40,560 --> 00:05:43,160 Speaker 1: And this is kind of another soapbox I like to 98 00:05:43,200 --> 00:05:46,839 Speaker 1: get up on to argue for the importance of exploratory science. 99 00:05:47,760 --> 00:05:50,360 Speaker 1: Applied science is really interesting. Applied science is when you're 100 00:05:50,360 --> 00:05:53,719 Speaker 1: trying to find a particular solution that will work for 101 00:05:53,839 --> 00:05:57,559 Speaker 1: some sort of problem. Right you might be researching whether 102 00:05:57,640 --> 00:06:00,800 Speaker 1: or not a specific material would be great rate to 103 00:06:01,040 --> 00:06:06,400 Speaker 1: use for a particular purpose, like bulletproof material something like that. 104 00:06:06,800 --> 00:06:11,200 Speaker 1: But exploratory science, when you're not necessarily looking for applications, 105 00:06:11,320 --> 00:06:15,039 Speaker 1: is also important because we expand our knowledge about how 106 00:06:15,080 --> 00:06:18,919 Speaker 1: the universe works. And it can open up opportunities to 107 00:06:19,040 --> 00:06:22,200 Speaker 1: leverage that knowledge in ways we could not have anticipated 108 00:06:22,240 --> 00:06:24,680 Speaker 1: when we first started looking into the issue in the 109 00:06:24,680 --> 00:06:29,599 Speaker 1: first place. It's important stuff, so I argue that exploratory 110 00:06:29,600 --> 00:06:34,600 Speaker 1: science needs to continue to be supported. Now acknowledge all this, 111 00:06:34,720 --> 00:06:36,320 Speaker 1: take a deep breath, and get ready to jump into 112 00:06:36,360 --> 00:06:42,120 Speaker 1: the strange world of magnetism. So first, magnetism, or more specifically, 113 00:06:42,240 --> 00:06:47,240 Speaker 1: electro magnetism, is one of four fundamental forces that govern 114 00:06:47,839 --> 00:06:52,000 Speaker 1: the atomic behavior in our universe. So the other three, 115 00:06:52,040 --> 00:06:55,480 Speaker 1: if you're keeping track, are the strong nuclear force, the 116 00:06:55,520 --> 00:06:58,640 Speaker 1: weak nuclear force, and gravity. And if you want to 117 00:06:58,720 --> 00:07:02,919 Speaker 1: rank those from the weakest to the strongest, you'd start 118 00:07:02,960 --> 00:07:07,719 Speaker 1: with gravity. Gravity is negligible at the atomic scale. It's there, 119 00:07:07,760 --> 00:07:11,360 Speaker 1: but it's so faint as to be almost absent. And 120 00:07:11,440 --> 00:07:14,920 Speaker 1: this is largely because gravity is dependent upon mass. So 121 00:07:15,000 --> 00:07:18,600 Speaker 1: at the atomic scale, masses are so small there's barely 122 00:07:18,640 --> 00:07:22,640 Speaker 1: any gravitational attraction between particles. But gravity is kind of 123 00:07:22,720 --> 00:07:26,760 Speaker 1: nifty because while it's weak, it is there, and in fact, 124 00:07:27,000 --> 00:07:30,160 Speaker 1: there's a gravitational pull on every bit of matter from 125 00:07:30,360 --> 00:07:34,240 Speaker 1: every other bit of matter in our universe. So you 126 00:07:35,000 --> 00:07:37,720 Speaker 1: that is you listening to me, right Now you are 127 00:07:38,320 --> 00:07:42,720 Speaker 1: exerting a gravitational pull on the Sun, and on Alpha Centauri, 128 00:07:43,480 --> 00:07:47,640 Speaker 1: and on the Andromeda galaxy. You are exerting a gravitational 129 00:07:47,640 --> 00:07:52,120 Speaker 1: pull on everything else that is matter in our universe. 130 00:07:53,040 --> 00:07:56,400 Speaker 1: It's just that that gravitational pull is so weak as 131 00:07:56,440 --> 00:08:00,520 Speaker 1: to be practically nothing, but it is there. So since 132 00:08:00,520 --> 00:08:03,880 Speaker 1: gravity is something we ourselves can and do experience in 133 00:08:03,920 --> 00:08:08,240 Speaker 1: our daily lives, we categorize it as one of the 134 00:08:08,400 --> 00:08:14,840 Speaker 1: familiar forces. Now, next in the rank from weakest to 135 00:08:14,960 --> 00:08:19,080 Speaker 1: strongest is the weak force. Now that's responsible for nuclear 136 00:08:19,120 --> 00:08:22,480 Speaker 1: beta decay and some other decay processes. And this one's 137 00:08:22,480 --> 00:08:25,000 Speaker 1: pretty difficult to explain, and since I'm already going to 138 00:08:25,080 --> 00:08:28,720 Speaker 1: have to explain magnetism, I'm gonna call for a pass 139 00:08:28,760 --> 00:08:29,320 Speaker 1: on this one. 140 00:08:29,520 --> 00:08:30,400 Speaker 2: Let's mulligan it. 141 00:08:31,160 --> 00:08:34,360 Speaker 1: But this is a force that we do not experience 142 00:08:34,400 --> 00:08:37,000 Speaker 1: firsthand in our daily lives, So this one actually falls 143 00:08:37,040 --> 00:08:42,040 Speaker 1: into the category of unfamiliar forces. Now, next in strength, 144 00:08:42,320 --> 00:08:47,760 Speaker 1: so second strongest, if you prefer, is the electromagnetic force, 145 00:08:47,800 --> 00:08:50,880 Speaker 1: the one we'll be focusing on today. Now, this is 146 00:08:50,920 --> 00:08:53,679 Speaker 1: a force that exists between all particles that have an 147 00:08:53,720 --> 00:08:57,440 Speaker 1: electric charge, so electrons, for example, we'll bind to a 148 00:08:57,520 --> 00:09:01,679 Speaker 1: nucleus because electrons have a nextative charge, and a nucleus 149 00:09:01,760 --> 00:09:06,320 Speaker 1: which only contains positively charged protons and neutral neutrons is 150 00:09:06,400 --> 00:09:11,440 Speaker 1: net positive. And you know that opposites attract, so we 151 00:09:11,600 --> 00:09:16,480 Speaker 1: have the negative electrons attracted to the positive nucleus. We 152 00:09:16,720 --> 00:09:20,520 Speaker 1: can and do experience electromagnetic forces on a daily basis, 153 00:09:20,520 --> 00:09:24,079 Speaker 1: so this one is one of the familiar forces. And 154 00:09:24,480 --> 00:09:27,360 Speaker 1: then we have the strongest of them all, the strong 155 00:09:27,760 --> 00:09:31,800 Speaker 1: nuclear force. This is the force that holds a nucleus together. 156 00:09:32,440 --> 00:09:35,600 Speaker 1: It's a dominant force in various chemical reactions, and it 157 00:09:35,679 --> 00:09:38,079 Speaker 1: has to be strong because it's. 158 00:09:37,920 --> 00:09:39,920 Speaker 2: Doing something that's really difficult to do. 159 00:09:40,040 --> 00:09:45,439 Speaker 1: It's holding together similarly charged particles. Remember, a nucleus is 160 00:09:45,480 --> 00:09:49,120 Speaker 1: a bunch of protons and neutrons. The protons all have 161 00:09:49,240 --> 00:09:52,720 Speaker 1: a positive charge. They don't want to be and when 162 00:09:52,720 --> 00:09:55,680 Speaker 1: I say want, I don't actually mean they have motivations, 163 00:09:55,679 --> 00:09:58,720 Speaker 1: but they don't want to be next to each other. 164 00:10:00,240 --> 00:10:03,959 Speaker 1: Those similar charges are repelling one another. So the strong 165 00:10:04,040 --> 00:10:07,600 Speaker 1: nuclear force has to be stronger than the electromagnetic force 166 00:10:07,640 --> 00:10:10,360 Speaker 1: in order to hold protons together in a nucleus with 167 00:10:10,400 --> 00:10:15,520 Speaker 1: a bunch of neutral charge particles. It does have a 168 00:10:15,600 --> 00:10:19,839 Speaker 1: very short range, however, so while it's stronger than the 169 00:10:19,920 --> 00:10:24,760 Speaker 1: electromagnetic force, the range does not reach very far outside 170 00:10:24,760 --> 00:10:27,200 Speaker 1: of a nucleus, so we don't directly observe it in 171 00:10:27,200 --> 00:10:30,720 Speaker 1: our daily lives, and therefore it is an unfamiliar force. 172 00:10:31,080 --> 00:10:34,880 Speaker 1: So gravity and electromagnetism are familiar forces. The strong and 173 00:10:34,920 --> 00:10:42,000 Speaker 1: weak nuclear forces are unfamiliar forces. So what makes electromagnetism 174 00:10:42,040 --> 00:10:44,840 Speaker 1: tick and how did we even figure out how to 175 00:10:44,920 --> 00:10:45,920 Speaker 1: make good use of it? 176 00:10:46,440 --> 00:10:47,760 Speaker 2: Well, let's start. 177 00:10:47,400 --> 00:10:50,320 Speaker 1: By imagining a bar magnet. A lot of this is 178 00:10:50,360 --> 00:10:52,840 Speaker 1: going to go back to stuff that you probably learned 179 00:10:52,880 --> 00:10:56,240 Speaker 1: in elementary school, middle school, high school, those physics courses, 180 00:10:56,280 --> 00:10:59,040 Speaker 1: that kind of stuff, basic science. So you've got your 181 00:10:59,080 --> 00:11:02,559 Speaker 1: bar magnet. Let's just say it's a rectang. It's rectangular 182 00:11:02,600 --> 00:11:06,760 Speaker 1: in shape, so you know you've got your north pole 183 00:11:06,920 --> 00:11:11,040 Speaker 1: and your south pole on the magnet. This These represent 184 00:11:11,440 --> 00:11:15,240 Speaker 1: the various charges magnetic charges of the magnet. 185 00:11:15,360 --> 00:11:16,360 Speaker 2: Opposites tracked. 186 00:11:17,000 --> 00:11:20,040 Speaker 1: So if we were to bring this bar magnet close 187 00:11:20,080 --> 00:11:23,360 Speaker 1: to another bar magnet, the north end of our bar 188 00:11:23,480 --> 00:11:26,560 Speaker 1: magnet would start to exert a pole on the south 189 00:11:26,800 --> 00:11:29,959 Speaker 1: end of the other bar magnet. Or if we were 190 00:11:29,960 --> 00:11:32,800 Speaker 1: to try and bring the north pole of our magnet 191 00:11:32,840 --> 00:11:35,240 Speaker 1: close to the north pole of the second magnet, it 192 00:11:35,280 --> 00:11:38,640 Speaker 1: would push against each other, just like I was mentioning 193 00:11:38,679 --> 00:11:41,960 Speaker 1: a second ago. Now, magnets produce a field around them 194 00:11:42,080 --> 00:11:46,600 Speaker 1: that we can represent as lines of force, and those 195 00:11:46,640 --> 00:11:50,720 Speaker 1: lines exit from the north pole, loop around the magnet, 196 00:11:51,000 --> 00:11:54,439 Speaker 1: and enter the south pole. A permanent magnet is always 197 00:11:54,520 --> 00:11:59,640 Speaker 1: producing the sort of magnetic field. It's consistent, it doesn't waiver. 198 00:12:00,600 --> 00:12:04,079 Speaker 1: You may hear about things like electromagnetism. I'll talk a 199 00:12:04,080 --> 00:12:07,240 Speaker 1: little bit more about in a bit where you have 200 00:12:07,320 --> 00:12:10,439 Speaker 1: to move a coil through a varying magnetic field. Well, 201 00:12:10,480 --> 00:12:15,280 Speaker 1: a permanent magnet creates a consistent magnetic field unless you 202 00:12:15,360 --> 00:12:17,800 Speaker 1: start doing things like moving it around, in which case 203 00:12:17,840 --> 00:12:20,280 Speaker 1: you're really just moving where the magnetic field is. You're 204 00:12:20,320 --> 00:12:26,680 Speaker 1: not actually fluctuating the field itself. Now, inside a magnet 205 00:12:26,760 --> 00:12:33,120 Speaker 1: a permanent magnet are microscopic regions called magnetic domains, and 206 00:12:33,240 --> 00:12:36,920 Speaker 1: each of these domains is essentially a tiny magnet with 207 00:12:36,960 --> 00:12:40,760 Speaker 1: its own north and south pole. Only by aligning the 208 00:12:40,800 --> 00:12:45,760 Speaker 1: poles of all of these magnetic domains in a similar direction, 209 00:12:46,000 --> 00:12:48,840 Speaker 1: like north south, will you get a permanent magnet. 210 00:12:49,280 --> 00:12:52,240 Speaker 2: So if you could just zoom in on. 211 00:12:52,200 --> 00:12:55,359 Speaker 1: A permanent magnet, you would see all these tiny regions 212 00:12:55,880 --> 00:12:58,880 Speaker 1: that are essentially magnets that are all aligned the same 213 00:12:58,960 --> 00:13:04,480 Speaker 1: way south. If you didn't do that, if the alignment 214 00:13:04,800 --> 00:13:07,160 Speaker 1: was mixed up so that you had, you know, an 215 00:13:07,200 --> 00:13:11,120 Speaker 1: equal mixture of north south and south north, they would 216 00:13:11,160 --> 00:13:13,480 Speaker 1: cancel each other out and you wouldn't have a magnet. 217 00:13:13,520 --> 00:13:18,800 Speaker 1: It would just be inert magnetically speaking. So that is 218 00:13:18,840 --> 00:13:21,840 Speaker 1: something that's interesting because you can actually do that to 219 00:13:22,000 --> 00:13:24,480 Speaker 1: magnets in a couple of different ways. I'll talk about 220 00:13:24,480 --> 00:13:29,720 Speaker 1: that in a second. So all of that is changeable, 221 00:13:30,679 --> 00:13:35,320 Speaker 1: bomb bomb bomb. I wrote that in my notes. Actually 222 00:13:35,480 --> 00:13:37,920 Speaker 1: I had to say it. I could show Dylan, but 223 00:13:37,920 --> 00:13:40,760 Speaker 1: he's working on something else. By the way, when all 224 00:13:40,760 --> 00:13:44,440 Speaker 1: those magnetic domains are aligned north south, what happens if 225 00:13:44,480 --> 00:13:46,800 Speaker 1: you were to cut the magnet in half right between 226 00:13:46,840 --> 00:13:49,400 Speaker 1: the north and south pole. So imagine you've got this 227 00:13:49,480 --> 00:13:51,120 Speaker 1: rectangular bar magnet. 228 00:13:50,760 --> 00:13:52,120 Speaker 2: You've got you've labeled one. 229 00:13:52,040 --> 00:13:53,960 Speaker 1: End the north pole, the other end of the south pole. 230 00:13:54,280 --> 00:13:58,959 Speaker 1: You cut the magnet in half horizontally across, well, you 231 00:13:59,000 --> 00:14:02,840 Speaker 1: would end up with two magnet. The middle of that 232 00:14:02,880 --> 00:14:05,880 Speaker 1: magnet would become the south pole for the north end 233 00:14:05,960 --> 00:14:08,160 Speaker 1: and the north pole for the south end. That's because 234 00:14:08,320 --> 00:14:11,960 Speaker 1: those magnetic domains I was talking about, those tiny regions 235 00:14:12,000 --> 00:14:16,120 Speaker 1: inside the magnet themselves itself, those are all aligned north south. 236 00:14:16,240 --> 00:14:18,600 Speaker 1: So if you cut the magnet across, you still have 237 00:14:18,679 --> 00:14:22,960 Speaker 1: those magnetic domains lined up north south, so the overall 238 00:14:23,040 --> 00:14:26,040 Speaker 1: magnetism is preserved. You get two magnets for the price 239 00:14:26,080 --> 00:14:29,920 Speaker 1: of one. But don't cut into magnets. Magnets, they tend 240 00:14:29,960 --> 00:14:32,280 Speaker 1: to be, at least the ones that we typically use 241 00:14:32,440 --> 00:14:34,920 Speaker 1: for things like our fridges and stuff are ceramic magnets, 242 00:14:34,960 --> 00:14:36,640 Speaker 1: and they don't cut so well unless you have like 243 00:14:36,680 --> 00:14:41,800 Speaker 1: a diamond saw, which some of you probably do. And 244 00:14:42,200 --> 00:14:45,480 Speaker 1: if you cut magnets normally, then disregard my warning. I'm 245 00:14:45,480 --> 00:14:47,800 Speaker 1: talking about people who don't typically do that sort of thing. 246 00:14:48,040 --> 00:14:49,760 Speaker 1: If you are going to do it, where eye protection 247 00:14:49,840 --> 00:14:56,160 Speaker 1: because that stuff can shatter anyway. If you do that 248 00:14:56,320 --> 00:15:00,040 Speaker 1: with a magnet. Essentially, each magnet has approximately half the 249 00:15:00,080 --> 00:15:04,160 Speaker 1: magnetic domains of the old magnet, so they're not particularly 250 00:15:04,240 --> 00:15:06,880 Speaker 1: you know, the individual magnets aren't as strong as they 251 00:15:06,880 --> 00:15:10,400 Speaker 1: were when they were a single magnet. Because your yournet, 252 00:15:10,640 --> 00:15:15,320 Speaker 1: your overall magnet strength is dependent upon the accumulative effect 253 00:15:15,480 --> 00:15:19,480 Speaker 1: of the magnetic domains within it, all right, So each 254 00:15:19,640 --> 00:15:24,320 Speaker 1: of those magnetic domains are tiny magnets. There are three 255 00:15:24,360 --> 00:15:26,800 Speaker 1: ways to get them to line up so that the 256 00:15:26,880 --> 00:15:30,560 Speaker 1: overall material becomes a magnet itself. Like how you get 257 00:15:30,560 --> 00:15:33,320 Speaker 1: them all to line up? Like north south? So way 258 00:15:33,440 --> 00:15:36,200 Speaker 1: number one is to whack on it with something heavy, 259 00:15:36,960 --> 00:15:39,200 Speaker 1: which isn't a joke. If you hold the material in 260 00:15:39,240 --> 00:15:41,480 Speaker 1: a north south direction and strike it with a hammer, 261 00:15:41,960 --> 00:15:45,760 Speaker 1: you physically realign the magnetic domains and you can knock 262 00:15:45,840 --> 00:15:50,360 Speaker 1: the material into a weak magnet. There's a bit more 263 00:15:50,400 --> 00:15:52,280 Speaker 1: to it than that, but that's the basic idea, and 264 00:15:52,320 --> 00:15:54,160 Speaker 1: that that does mean that you're not going to get 265 00:15:54,160 --> 00:15:56,440 Speaker 1: a very strong magnet as a result, but you can 266 00:15:56,720 --> 00:16:01,800 Speaker 1: physically force those magnetic domains to be in the same 267 00:16:01,880 --> 00:16:06,160 Speaker 1: direction and create a magnet that way. Way number two 268 00:16:06,680 --> 00:16:09,680 Speaker 1: is that you can place the material inside a strong 269 00:16:09,760 --> 00:16:12,160 Speaker 1: magnetic field and make sure the material is in a 270 00:16:12,240 --> 00:16:15,920 Speaker 1: north south alignment and you just leave it there, and 271 00:16:16,320 --> 00:16:18,720 Speaker 1: if it's a strong magnetic field, it will start to 272 00:16:18,960 --> 00:16:23,800 Speaker 1: realign the magnetic domains within your target material so that 273 00:16:23,920 --> 00:16:28,800 Speaker 1: they gradually line up with the magnetic fields direction, so 274 00:16:28,840 --> 00:16:30,280 Speaker 1: you just have to have a strong enough one to 275 00:16:30,320 --> 00:16:33,040 Speaker 1: affect the magnetic domains in your target material and then 276 00:16:33,080 --> 00:16:36,360 Speaker 1: eventually you end up with a magnet So that's kind 277 00:16:36,360 --> 00:16:39,200 Speaker 1: of cool. And way number three is ya zap it 278 00:16:39,360 --> 00:16:43,760 Speaker 1: with electric current. So one hypothesis is that this is 279 00:16:43,800 --> 00:16:47,480 Speaker 1: how loadstone, which is a naturally magnetic material you can 280 00:16:47,520 --> 00:16:51,000 Speaker 1: find here on Earth, was originally formed. The idea is 281 00:16:51,040 --> 00:16:54,560 Speaker 1: that loadstone, which is made up of the stuff called magnetite, 282 00:16:55,920 --> 00:16:59,960 Speaker 1: some of it was struck by lightning over the millennium 283 00:17:00,440 --> 00:17:04,399 Speaker 1: that Earth was forming, So you have magnetite on the surface. 284 00:17:04,040 --> 00:17:04,600 Speaker 2: Of the planet. 285 00:17:04,680 --> 00:17:07,919 Speaker 1: Occasionally lightning strikes and hit some of this magnetite and 286 00:17:07,960 --> 00:17:13,720 Speaker 1: then magnetizes it. That's one hypothesis, but there's another one 287 00:17:13,760 --> 00:17:17,199 Speaker 1: which suggests that magnetite gained its magnetic properties during the 288 00:17:17,200 --> 00:17:19,560 Speaker 1: time when Earth was forming, and it was through more 289 00:17:19,600 --> 00:17:23,920 Speaker 1: of just a physical the physical process of cooling where 290 00:17:23,960 --> 00:17:25,840 Speaker 1: these magnetic domains aligned in. 291 00:17:25,760 --> 00:17:26,520 Speaker 2: The proper way. 292 00:17:27,160 --> 00:17:30,360 Speaker 1: Here's the thing, we don't really know how it all 293 00:17:30,400 --> 00:17:31,160 Speaker 1: got started. 294 00:17:31,400 --> 00:17:32,520 Speaker 2: We don't have that information. 295 00:17:32,640 --> 00:17:34,840 Speaker 1: No one was around back then to write it down 296 00:17:35,160 --> 00:17:38,200 Speaker 1: or put it in magnetic storage. So it's still a 297 00:17:38,200 --> 00:17:40,640 Speaker 1: bit of a mystery, but we do know that those 298 00:17:40,640 --> 00:17:43,320 Speaker 1: are two possible ways that this could have come about. 299 00:17:44,280 --> 00:17:45,439 Speaker 2: And you can. 300 00:17:45,359 --> 00:17:50,080 Speaker 1: Also render magnets inert by changing the alignment of the 301 00:17:50,080 --> 00:17:53,520 Speaker 1: magnetic domains within it. If you heat a magnet up 302 00:17:53,560 --> 00:17:58,160 Speaker 1: beyond its Curey point, which is different for different magnetic materials, 303 00:17:58,520 --> 00:18:02,119 Speaker 1: it loses its magnetism. The heat warps the material and 304 00:18:02,200 --> 00:18:05,679 Speaker 1: makes the magnetic domains fall out of alignment. So what 305 00:18:05,960 --> 00:18:08,880 Speaker 1: used to be magnetic will no longer be so something 306 00:18:08,920 --> 00:18:11,320 Speaker 1: that would stick to your fringe no problem, will just 307 00:18:11,359 --> 00:18:14,960 Speaker 1: slide off and hit the floor, and everyone will be sad, 308 00:18:15,640 --> 00:18:17,919 Speaker 1: unless you just did it as a scientific experiment, in 309 00:18:17,920 --> 00:18:19,399 Speaker 1: which case you might be happy that you got the 310 00:18:19,440 --> 00:18:25,360 Speaker 1: result you expected. Now we can experience magnetism because of electrons. 311 00:18:25,560 --> 00:18:29,359 Speaker 1: Those tiny, negatively charged sub atomic particles hold the key 312 00:18:29,520 --> 00:18:33,520 Speaker 1: to whether material is affected by magnets or isn't. You 313 00:18:33,680 --> 00:18:36,320 Speaker 1: might wonder, like, why are some things magnetic and some 314 00:18:36,400 --> 00:18:39,239 Speaker 1: things art? Why do magnets stick to some materials but 315 00:18:39,359 --> 00:18:42,840 Speaker 1: slide right off of other materials? And ultimately the answer 316 00:18:42,880 --> 00:18:50,480 Speaker 1: of falls with electrons. Now, electrons orbit the nucleus right 317 00:18:50,680 --> 00:18:53,960 Speaker 1: in atoms, You remember your basic description of an atom 318 00:18:53,960 --> 00:18:56,320 Speaker 1: where you have a nucleus at the center and electrons 319 00:18:56,400 --> 00:19:02,000 Speaker 1: orbiting at different orbital shells around the electrons. Typically electrons 320 00:19:02,000 --> 00:19:05,919 Speaker 1: will pair up with other electrons. You'll get pairs of electrons. 321 00:19:05,960 --> 00:19:10,120 Speaker 1: They have a state that's called spin, and each electron 322 00:19:10,160 --> 00:19:12,760 Speaker 1: in a pair has the opposite spin of its partner, 323 00:19:13,240 --> 00:19:16,359 Speaker 1: So we can describe spin as up or down. For example, 324 00:19:16,840 --> 00:19:20,080 Speaker 1: if one electron is spinning up, the other one by necessity, 325 00:19:20,200 --> 00:19:23,879 Speaker 1: has to be spinning down. You cannot get both electrons 326 00:19:23,920 --> 00:19:26,960 Speaker 1: in a pair to spin in the same direction in 327 00:19:27,000 --> 00:19:30,120 Speaker 1: the same orbital That just that ain't cricket. It's part 328 00:19:30,119 --> 00:19:34,080 Speaker 1: of a quantum mechanical principle we call the poly exclusion principle. 329 00:19:34,840 --> 00:19:36,880 Speaker 1: And until I did research for the show, I could 330 00:19:36,920 --> 00:19:39,200 Speaker 1: have sworn that referred to the practice of not inviting 331 00:19:39,240 --> 00:19:42,000 Speaker 1: poly shore to your parties. So I guess you learned 332 00:19:42,040 --> 00:19:45,280 Speaker 1: something new every day. That got a smirk from Dylan. 333 00:19:46,040 --> 00:19:48,919 Speaker 1: It's maybe he'll laugh when he listens to it the 334 00:19:48,960 --> 00:19:53,239 Speaker 1: second time. Some elements have an unpaired electron in an 335 00:19:53,320 --> 00:19:55,760 Speaker 1: orbital just because that's just how it works out. So 336 00:19:56,720 --> 00:20:01,760 Speaker 1: those unpaired spinning electrons generate a very tiny magnetic field, 337 00:20:02,200 --> 00:20:05,800 Speaker 1: and we call it an orbital magnetic moment, which sounds 338 00:20:05,840 --> 00:20:09,440 Speaker 1: like something you'd expect in a romantic science fiction film. Iron, 339 00:20:09,800 --> 00:20:14,639 Speaker 1: for example, has four unpaired electrons that all have the 340 00:20:14,720 --> 00:20:20,119 Speaker 1: same spin. Those four unpaired electrons have an orbital magnetic moment. 341 00:20:20,400 --> 00:20:23,840 Speaker 1: So magnetic moment has a magnitude and a direction, which 342 00:20:23,880 --> 00:20:27,280 Speaker 1: means it is a vector. The bottom line is this 343 00:20:27,400 --> 00:20:30,280 Speaker 1: vector refers to the strength of the magnetic field and 344 00:20:30,320 --> 00:20:34,520 Speaker 1: the torque it can exert. So a permanent magnets magnetic 345 00:20:34,560 --> 00:20:37,600 Speaker 1: moments are composed of all the moments of its atoms. 346 00:20:38,160 --> 00:20:42,240 Speaker 1: In other words, we've got all these atoms that represent 347 00:20:42,359 --> 00:20:45,240 Speaker 1: an orbital magnetic moment because of the spin of the 348 00:20:45,320 --> 00:20:47,359 Speaker 1: electrons of the unpaired electrons. 349 00:20:47,359 --> 00:20:48,600 Speaker 2: If you've got enough of them. 350 00:20:48,440 --> 00:20:51,440 Speaker 1: And they're aligned the right way, that determines the permanent 351 00:20:51,480 --> 00:20:56,640 Speaker 1: magnets magnetic moments. So iron and several other magnetic elements 352 00:20:56,680 --> 00:21:00,880 Speaker 1: have a crystalline structure, right, So think of it like scaffolding. 353 00:21:01,440 --> 00:21:05,120 Speaker 1: It makes this very ordered kind of structure as opposed 354 00:21:05,200 --> 00:21:08,679 Speaker 1: to something that looks much more chaotic. So as iron 355 00:21:08,800 --> 00:21:12,639 Speaker 1: cools from a molten state, atoms line up into this 356 00:21:12,760 --> 00:21:16,600 Speaker 1: crystalline arrangement. And groups of atoms that have a parallel 357 00:21:16,720 --> 00:21:20,120 Speaker 1: orbital spin will line up within the crystal, and those 358 00:21:20,200 --> 00:21:24,040 Speaker 1: form those magnetic domains I mentioned earlier. The qualities that 359 00:21:24,080 --> 00:21:26,919 Speaker 1: make good magnets are also the same ones as the 360 00:21:26,960 --> 00:21:29,879 Speaker 1: qualities that make materials attracted to magnets. 361 00:21:30,000 --> 00:21:30,840 Speaker 2: So a strong. 362 00:21:30,600 --> 00:21:33,320 Speaker 1: Magnet will attract iron and other elements that have these 363 00:21:33,480 --> 00:21:38,200 Speaker 1: orbital magnetic moments in alignment. Now, not all permanent magnets 364 00:21:38,359 --> 00:21:41,399 Speaker 1: are equal. The ceramic magnets you may have on your 365 00:21:41,400 --> 00:21:44,480 Speaker 1: fringe door are pretty weak all things considered. They're made 366 00:21:44,480 --> 00:21:47,960 Speaker 1: of a mixture of iron oxide and a ceramic composite. 367 00:21:48,160 --> 00:21:51,439 Speaker 1: These are feric magnets. That's what we call them, feric 368 00:21:51,520 --> 00:21:53,720 Speaker 1: for the iron that's in them. But on the other 369 00:21:53,840 --> 00:21:57,600 Speaker 1: end of the scale are neodymium magnets, a rare earth 370 00:21:57,640 --> 00:22:01,359 Speaker 1: element magnet does much much, much stronger than the feric 371 00:22:01,400 --> 00:22:04,600 Speaker 1: magnets we tend to use, and they typically contain a 372 00:22:04,640 --> 00:22:09,440 Speaker 1: mixture of neodymium, iron and boron. They could be really 373 00:22:09,480 --> 00:22:13,720 Speaker 1: strong too. I have played with some where if they 374 00:22:13,800 --> 00:22:16,760 Speaker 1: get into contact with something like a metal table, it 375 00:22:16,800 --> 00:22:20,159 Speaker 1: can be really hard to remove them. We had some 376 00:22:20,320 --> 00:22:24,679 Speaker 1: here at How Stuff Works that were potentially causing injuries. 377 00:22:25,800 --> 00:22:28,240 Speaker 1: One person slipped one in their pocket and then found 378 00:22:28,280 --> 00:22:30,680 Speaker 1: themselves stuck to a filing cabinet for a little bit. 379 00:22:31,400 --> 00:22:33,080 Speaker 2: This was way back in the day, but. 380 00:22:34,080 --> 00:22:35,280 Speaker 1: It was one of those things where a lot of 381 00:22:35,359 --> 00:22:36,919 Speaker 1: us didn't have a whole lot of experience with it 382 00:22:36,920 --> 00:22:40,240 Speaker 1: because at the time they were fairly uncommon. Today you 383 00:22:40,280 --> 00:22:45,080 Speaker 1: can order neodymium and other rare earth magnets online without 384 00:22:45,119 --> 00:22:49,119 Speaker 1: much trouble. But when I started, first of all, how 385 00:22:49,160 --> 00:22:51,560 Speaker 1: stuff works was easy because there were only three things, 386 00:22:51,840 --> 00:22:54,400 Speaker 1: so it was easy to explain how stuff works. Once 387 00:22:54,400 --> 00:22:55,959 Speaker 1: you wrote the three articles, you were done. 388 00:22:56,480 --> 00:22:58,160 Speaker 2: But over time more stuff. 389 00:22:57,920 --> 00:23:01,199 Speaker 1: Was made and we had more work to do, and 390 00:23:01,440 --> 00:23:03,880 Speaker 1: at that point it was more. 391 00:23:04,119 --> 00:23:04,880 Speaker 2: It was more. 392 00:23:07,400 --> 00:23:10,400 Speaker 1: Well, it was easier to get hold of neodymium magnets 393 00:23:10,400 --> 00:23:14,280 Speaker 1: at that point. Now some materials are called temporary or 394 00:23:14,320 --> 00:23:17,399 Speaker 1: soft magnets, and those will produce a magnetic field in 395 00:23:17,440 --> 00:23:20,240 Speaker 1: the presence of another magnetic field and retain some of 396 00:23:20,240 --> 00:23:24,560 Speaker 1: that magnetism for a while after they leave the field itself, 397 00:23:24,880 --> 00:23:27,680 Speaker 1: so they're very easy to influence. So imagine that you've 398 00:23:27,680 --> 00:23:30,439 Speaker 1: got something like a paper clip and you put it 399 00:23:30,480 --> 00:23:33,240 Speaker 1: within the range of a magnetic field for a while 400 00:23:33,800 --> 00:23:39,960 Speaker 1: and it starts to have its magnetic domains aligned according 401 00:23:40,000 --> 00:23:42,720 Speaker 1: to this magnetic field. You remove it and you find 402 00:23:42,760 --> 00:23:44,600 Speaker 1: you can pick up other paper clips with it, but 403 00:23:44,680 --> 00:23:45,960 Speaker 1: only for a little while, and. 404 00:23:45,880 --> 00:23:46,919 Speaker 2: Then it stops working. 405 00:23:48,000 --> 00:23:54,080 Speaker 1: That's very typical with soft or temporary magnets. They very 406 00:23:54,160 --> 00:23:56,960 Speaker 1: quickly will change, but then they will overtime change back 407 00:23:57,000 --> 00:24:00,600 Speaker 1: to being, let you know, not magnetic, but they're also 408 00:24:01,200 --> 00:24:06,679 Speaker 1: hard magnetic materials. These it's harder to change them, but 409 00:24:06,800 --> 00:24:10,959 Speaker 1: then they will stay changed for longer. So stuff like iron, 410 00:24:11,040 --> 00:24:15,159 Speaker 1: if you're able to really realign those magnetic domains and 411 00:24:15,240 --> 00:24:19,960 Speaker 1: iron magnet will hold that magnetic ability much much longer. 412 00:24:20,160 --> 00:24:22,280 Speaker 1: And that's how you can end up with permanent magnets 413 00:24:22,320 --> 00:24:25,040 Speaker 1: as opposed to some that will just temporarily be magnetic. 414 00:24:26,440 --> 00:24:27,320 Speaker 2: It's kind of interesting. 415 00:24:28,080 --> 00:24:31,520 Speaker 1: So then you've got electromagnets and this will only produce 416 00:24:31,560 --> 00:24:35,200 Speaker 1: the magnetic field in the presence of electricity. And I'm 417 00:24:35,240 --> 00:24:39,399 Speaker 1: sure everyone listening to this has done some variation on 418 00:24:39,720 --> 00:24:44,080 Speaker 1: the experiment where you take an iron nail and you 419 00:24:44,160 --> 00:24:48,080 Speaker 1: coil some wire around it, usually some insulated copper wire 420 00:24:48,400 --> 00:24:51,840 Speaker 1: around the nail several times, and then you run an 421 00:24:51,880 --> 00:24:55,040 Speaker 1: electric current through the wire and you create an electromagnet. 422 00:24:55,359 --> 00:24:59,000 Speaker 1: The nail becomes magnetic and you can pick up all sorts. 423 00:24:58,760 --> 00:24:59,400 Speaker 2: Of stuff with it. 424 00:25:00,000 --> 00:25:03,280 Speaker 1: The strength of the magnetic field is dependent upon the 425 00:25:03,359 --> 00:25:08,080 Speaker 1: number of coils around the nail, as well as some 426 00:25:08,119 --> 00:25:11,840 Speaker 1: other factors, but that's the primary one. And you know, 427 00:25:11,960 --> 00:25:14,879 Speaker 1: it's a cool, little basic science experiment you can run, 428 00:25:15,160 --> 00:25:19,280 Speaker 1: but it's also the basis of a ton of the 429 00:25:19,680 --> 00:25:25,639 Speaker 1: work done in electrical fields, including general electronics, computers, storage. 430 00:25:26,400 --> 00:25:34,800 Speaker 1: It is an important fundamental piece of technology, and the 431 00:25:35,240 --> 00:25:39,359 Speaker 1: very simple applications of this you can find in stuff 432 00:25:39,440 --> 00:25:45,560 Speaker 1: like electric transformers or electric motors and dynamos. Like transformer, 433 00:25:45,760 --> 00:25:50,399 Speaker 1: you can have two different coils of wire, one that 434 00:25:50,680 --> 00:25:53,560 Speaker 1: is got a lot more coils to it, like maybe 435 00:25:53,640 --> 00:25:56,879 Speaker 1: twice as many as the second one, and when you 436 00:25:57,040 --> 00:26:01,679 Speaker 1: run a current through the larger number of coils, the 437 00:26:01,800 --> 00:26:05,679 Speaker 1: magnetic field it generates induces electricity to flow through the 438 00:26:05,840 --> 00:26:09,440 Speaker 1: second set of coils, but it steps down the voltage 439 00:26:09,960 --> 00:26:14,200 Speaker 1: because you have half as many coils around a core 440 00:26:14,359 --> 00:26:17,000 Speaker 1: as you do with the first one. That's how you 441 00:26:17,040 --> 00:26:20,160 Speaker 1: can step down or step up voltage, and that's why 442 00:26:20,320 --> 00:26:24,959 Speaker 1: alternating current ends up being much more effective for distributing 443 00:26:25,000 --> 00:26:29,040 Speaker 1: electricity across long distances than direct current, because. 444 00:26:28,760 --> 00:26:29,880 Speaker 2: You can't do that with direct current. 445 00:26:29,920 --> 00:26:33,560 Speaker 1: You need that alternating electric current in order to create 446 00:26:33,600 --> 00:26:37,160 Speaker 1: the magnetic field that will induce electricity to flow through 447 00:26:37,200 --> 00:26:40,679 Speaker 1: a separate set of coils. Just like you need a 448 00:26:40,800 --> 00:26:45,480 Speaker 1: varying magnetic field to induce electricity, you need that varying 449 00:26:45,520 --> 00:26:51,760 Speaker 1: electricity to produce a varying magnetic field. It's this interesting relationship, 450 00:26:51,920 --> 00:26:56,200 Speaker 1: a fundamental relationship in our universe, between electricity and magnetism. 451 00:26:56,840 --> 00:26:59,240 Speaker 1: And that's why I was saying before. If you have 452 00:26:59,280 --> 00:27:01,359 Speaker 1: a permanent magnet and you just put it next to 453 00:27:01,520 --> 00:27:05,600 Speaker 1: a coil of wire, it's not going to induce electricity 454 00:27:05,600 --> 00:27:08,640 Speaker 1: to flow apart from when you first introduce the magnetic 455 00:27:08,640 --> 00:27:11,719 Speaker 1: field to the coil, because it's not varying. You'd have 456 00:27:11,760 --> 00:27:18,240 Speaker 1: to spin the permanent magnet, which would you know, effectively, 457 00:27:18,280 --> 00:27:22,560 Speaker 1: according to the coil's perspective, change the alignment of that 458 00:27:22,600 --> 00:27:26,919 Speaker 1: magnetic field that would induce electricity to flow through the wire. 459 00:27:27,520 --> 00:27:31,520 Speaker 1: But just having a standard magnet staying perfectly still next 460 00:27:31,520 --> 00:27:34,080 Speaker 1: to wire, you don't get the electricity to flow that way. 461 00:27:35,240 --> 00:27:39,480 Speaker 1: And that is a very important aspect to memory storage 462 00:27:39,520 --> 00:27:42,560 Speaker 1: as well. And that's our lesson on the physics of 463 00:27:42,560 --> 00:27:46,240 Speaker 1: magnets without diving too deeply into quantum mechanics. I think 464 00:27:46,280 --> 00:27:49,320 Speaker 1: we're ready to talk about our use of magnets with electronics, 465 00:27:49,320 --> 00:27:53,560 Speaker 1: but first let's take a quick break to thank our sponsor. 466 00:28:02,119 --> 00:28:05,000 Speaker 1: All Right, we're back, and we just learned how magnets 467 00:28:05,040 --> 00:28:07,520 Speaker 1: work in general, But when did we figure out they 468 00:28:07,520 --> 00:28:10,879 Speaker 1: could be useful for storing information? So I'm going to 469 00:28:10,920 --> 00:28:14,080 Speaker 1: skip over all the historic uses of magnets leading up 470 00:28:14,119 --> 00:28:17,720 Speaker 1: to data storage because I cannot spend another hour talking 471 00:28:17,720 --> 00:28:21,600 Speaker 1: about compasses, or ironically, i'll lose Dylan here in the studio. 472 00:28:22,080 --> 00:28:25,280 Speaker 1: So in the late nineteenth century we saw a boom 473 00:28:25,560 --> 00:28:29,480 Speaker 1: in innovation that was mid to late nineteenth century was 474 00:28:29,560 --> 00:28:34,639 Speaker 1: a crazy time in the world really for inventors discovering 475 00:28:35,119 --> 00:28:38,719 Speaker 1: not just fundamental principles of science, but how to apply 476 00:28:38,920 --> 00:28:42,200 Speaker 1: them in technology. I'm talking about stuff like Samuel Moore 477 00:28:42,280 --> 00:28:46,160 Speaker 1: successfully sending an electrical signal that could be decoded into communication, 478 00:28:46,800 --> 00:28:49,360 Speaker 1: all the way up to Alexander Graham Bell showing that 479 00:28:49,400 --> 00:28:52,880 Speaker 1: electricity could also be used to carry audio signals and 480 00:28:52,920 --> 00:28:57,160 Speaker 1: then be converted from electricity back into audio signals. That 481 00:28:57,200 --> 00:29:00,960 Speaker 1: really got things moving. And over at Thomas Edison's Menlo Park, 482 00:29:01,720 --> 00:29:05,120 Speaker 1: a guy named Oberlin Smith got a gander at a 483 00:29:05,120 --> 00:29:09,760 Speaker 1: cylinder phonograph and got some interesting ideas. So first let's 484 00:29:09,760 --> 00:29:14,280 Speaker 1: talk about this cylinder phonograph. It would record sound by 485 00:29:14,360 --> 00:29:19,080 Speaker 1: transforming audio waves into electrical signals. That would then cause 486 00:29:19,160 --> 00:29:23,360 Speaker 1: a needle to etch grooves into a wax cylinder. So 487 00:29:23,400 --> 00:29:26,840 Speaker 1: you've got this wax cylinder. It would slowly spin and 488 00:29:26,920 --> 00:29:29,240 Speaker 1: a needle would be dragged across it, and as sound 489 00:29:29,280 --> 00:29:32,120 Speaker 1: came in, it would cause the needle to wiggle around, 490 00:29:32,200 --> 00:29:36,080 Speaker 1: and that caused variations in the etching on the wax 491 00:29:36,120 --> 00:29:36,960 Speaker 1: cylinder itself. 492 00:29:37,920 --> 00:29:39,720 Speaker 2: Now, when you took that cylinder. 493 00:29:39,320 --> 00:29:42,040 Speaker 1: Out and you put it in another phonograph and you 494 00:29:42,120 --> 00:29:45,760 Speaker 1: placed a needle on it within the groove, and he 495 00:29:45,880 --> 00:29:49,680 Speaker 1: started to earn the cylinder, the needle would start to 496 00:29:49,720 --> 00:29:52,680 Speaker 1: shake because it's following the groove that was made by 497 00:29:52,760 --> 00:29:56,760 Speaker 1: the previous recording. Essentially, that whole process would be reversed. 498 00:29:57,080 --> 00:30:00,960 Speaker 1: The shaky needle would generate an electrical s which would 499 00:30:01,000 --> 00:30:05,239 Speaker 1: then go to a essentially a speaker a diaphragm and 500 00:30:05,280 --> 00:30:08,400 Speaker 1: cause it to vibrate and that would generate the sound, 501 00:30:08,560 --> 00:30:10,480 Speaker 1: so you would get a replica of the sound you 502 00:30:10,560 --> 00:30:15,600 Speaker 1: made when you were speaking into the wax cylinder phonograph. Now, 503 00:30:15,680 --> 00:30:18,000 Speaker 1: Oberlin Smith wondered if he might be able to do 504 00:30:18,040 --> 00:30:21,760 Speaker 1: the same thing, only instead of using a wax cylinder, 505 00:30:22,400 --> 00:30:27,440 Speaker 1: he would record sound onto magnetic wire, not tape, not 506 00:30:27,560 --> 00:30:33,280 Speaker 1: a disc, but an actual length of wire using magnetism. Now, 507 00:30:33,880 --> 00:30:38,000 Speaker 1: he was not successful in this attempt, but he published 508 00:30:38,080 --> 00:30:42,480 Speaker 1: his ideas in a journal called Electrical World in eighteen 509 00:30:42,600 --> 00:30:47,320 Speaker 1: eighty eight, and ten years later a Dutch inventor inventor 510 00:30:47,400 --> 00:30:52,480 Speaker 1: named Valdemar Pulsen gave it another go. He began a 511 00:30:53,240 --> 00:30:56,440 Speaker 1: working magnet recorder. He started building it. He called it 512 00:30:56,480 --> 00:31:00,320 Speaker 1: the telegraphone Pulson, and he filed the patent for this 513 00:31:00,360 --> 00:31:03,400 Speaker 1: invention in eighteen ninety nine. So one year after he 514 00:31:03,440 --> 00:31:06,520 Speaker 1: started working on it, he showed it off at the 515 00:31:06,880 --> 00:31:11,200 Speaker 1: nineteen hundred Paris Exhibition. So how did it work? What 516 00:31:11,520 --> 00:31:15,400 Speaker 1: exactly was it doing? How was it preserving this audio 517 00:31:15,440 --> 00:31:18,200 Speaker 1: information in a magnetic format so that it could be 518 00:31:18,200 --> 00:31:18,840 Speaker 1: played back? 519 00:31:19,680 --> 00:31:20,840 Speaker 2: Well, Poulson knew. 520 00:31:20,640 --> 00:31:24,000 Speaker 1: That he needed a magnetically hard material. If you remember 521 00:31:24,040 --> 00:31:26,120 Speaker 1: what I was talking about, before the break. That's a 522 00:31:26,160 --> 00:31:30,480 Speaker 1: material that will retain its magnetic moment indefinitely. It may 523 00:31:30,600 --> 00:31:35,720 Speaker 1: very gradually revert back to its original status, but it'll 524 00:31:35,720 --> 00:31:38,360 Speaker 1: hold it over a great deal of time. And if 525 00:31:38,400 --> 00:31:41,240 Speaker 1: you want to record data for later retrieval, obviously you 526 00:31:41,320 --> 00:31:45,360 Speaker 1: want to make sure that that data remains intact. Otherwise 527 00:31:45,480 --> 00:31:48,000 Speaker 1: you have a self destructing or at least a self 528 00:31:48,040 --> 00:31:52,240 Speaker 1: erasing message on your hands. So Paulson had to experiment 529 00:31:52,280 --> 00:31:55,440 Speaker 1: with various factors to make certain he could record anything 530 00:31:55,640 --> 00:31:58,440 Speaker 1: to the medium. To begin with, if the medium has 531 00:31:58,480 --> 00:32:02,160 Speaker 1: a coercivity factor that's very high, that means you have 532 00:32:02,200 --> 00:32:04,920 Speaker 1: to use stronger magnetic fields. 533 00:32:04,760 --> 00:32:05,479 Speaker 2: To affect it. 534 00:32:06,520 --> 00:32:08,680 Speaker 1: I'll al ways talk about magnetic fields now. I'm thinking 535 00:32:08,680 --> 00:32:11,160 Speaker 1: about the Book of Love, this great song by a 536 00:32:11,160 --> 00:32:12,400 Speaker 1: group called the Magnetic Fields. 537 00:32:12,640 --> 00:32:13,360 Speaker 2: Back to this. 538 00:32:13,440 --> 00:32:16,240 Speaker 1: So you have to have a really strong magnetic field 539 00:32:16,280 --> 00:32:21,360 Speaker 1: in order to affect that material, and that can be difficult. 540 00:32:21,360 --> 00:32:23,520 Speaker 1: It can start to eat in on your efficiency. And 541 00:32:23,560 --> 00:32:25,960 Speaker 1: you need the magnetic information to be distinct enough so 542 00:32:26,000 --> 00:32:29,560 Speaker 1: that you could get a good replay signal. And you know, 543 00:32:29,680 --> 00:32:31,800 Speaker 1: when you're reading the material back later, you want to 544 00:32:31,800 --> 00:32:34,040 Speaker 1: make sure you can actually hear what was recorded and 545 00:32:34,120 --> 00:32:39,640 Speaker 1: not just get some sort of muffled, you know, simulation. 546 00:32:39,400 --> 00:32:41,120 Speaker 2: Of the sounds you made. 547 00:32:41,320 --> 00:32:45,400 Speaker 1: So to record information onto a wire, you first need 548 00:32:45,480 --> 00:32:48,680 Speaker 1: a recording head. You need something that's going to generate 549 00:32:49,080 --> 00:32:52,400 Speaker 1: a magnetic flux that can affect. 550 00:32:52,200 --> 00:32:54,680 Speaker 2: The medium you're using, the wire in this case. 551 00:32:55,560 --> 00:32:58,040 Speaker 1: This, by the way, is also true for other methods 552 00:32:58,080 --> 00:33:01,960 Speaker 1: of magnetic storage, including cassette tape, VHS tapes, floppy disks, 553 00:33:02,040 --> 00:33:04,840 Speaker 1: and some hard drives. When I say some hard drives, 554 00:33:04,840 --> 00:33:06,320 Speaker 1: I mean magnetic hard drives. 555 00:33:06,360 --> 00:33:07,400 Speaker 2: Obviously, there are. 556 00:33:07,560 --> 00:33:10,440 Speaker 1: Solid state hard drives that are not affected in this way. 557 00:33:10,480 --> 00:33:13,920 Speaker 1: They don't use that technology. They are not part of 558 00:33:14,000 --> 00:33:19,920 Speaker 1: this discussion. So the recording head is a transducer, and 559 00:33:20,040 --> 00:33:24,560 Speaker 1: basically a transducer is something that converts some physical quantity 560 00:33:24,720 --> 00:33:28,520 Speaker 1: into an electrical signal, or does the reverse. So you 561 00:33:28,640 --> 00:33:31,960 Speaker 1: might have a transducer that can measure pressure, like air 562 00:33:32,000 --> 00:33:36,120 Speaker 1: pressure and change that into an electrical signal. That's a transducer. 563 00:33:36,760 --> 00:33:38,640 Speaker 1: But in this case we're talking about things like a 564 00:33:38,720 --> 00:33:42,840 Speaker 1: microphone a transducer, and a microphone converts pressure from sound 565 00:33:42,880 --> 00:33:47,400 Speaker 1: waves into electrical signals. With recording devices, you can use 566 00:33:47,480 --> 00:33:51,080 Speaker 1: one transducer to pull double duty one of them. It 567 00:33:51,080 --> 00:33:54,320 Speaker 1: can act as both a recording head when recording, so 568 00:33:54,560 --> 00:33:58,040 Speaker 1: it's actually writing something to the storage medium, or it 569 00:33:58,040 --> 00:34:01,040 Speaker 1: could be a read head when playing a signal back 570 00:34:01,080 --> 00:34:03,760 Speaker 1: it's reading the signal and then converting it back into 571 00:34:03,760 --> 00:34:07,360 Speaker 1: whatever it was originally before it was stored in that format. 572 00:34:07,960 --> 00:34:11,520 Speaker 1: Now these days, most recording devices still use that are 573 00:34:11,520 --> 00:34:15,920 Speaker 1: still using magnetic storage have a dedicated recording head and 574 00:34:16,000 --> 00:34:19,520 Speaker 1: a dedicated read head so that each transducer can be 575 00:34:19,560 --> 00:34:21,200 Speaker 1: optimized for its respective role. 576 00:34:21,320 --> 00:34:22,120 Speaker 2: You don't see a. 577 00:34:22,000 --> 00:34:26,080 Speaker 1: Whole lot of them where it's doing both things. Some 578 00:34:26,280 --> 00:34:29,360 Speaker 1: very cheap electronics, probably because then you don't have to 579 00:34:29,400 --> 00:34:32,120 Speaker 1: have as many components in it makes it less expensive 580 00:34:32,160 --> 00:34:36,160 Speaker 1: to produce. Now, the right head's job, or the recording 581 00:34:36,200 --> 00:34:39,600 Speaker 1: head if you prefer, is to convert electric current into 582 00:34:39,719 --> 00:34:43,520 Speaker 1: a magnetic field. But you remember what we said about electromagnets, 583 00:34:43,560 --> 00:34:46,959 Speaker 1: that's pretty easy to do. The field it generates needs 584 00:34:47,000 --> 00:34:50,960 Speaker 1: to be strong enough to affect the storage medium the wire, 585 00:34:51,600 --> 00:34:54,440 Speaker 1: but also it has to fall off quickly as you 586 00:34:54,480 --> 00:34:57,239 Speaker 1: move away from the recording head. In other words, you 587 00:34:57,320 --> 00:35:01,400 Speaker 1: don't want the effect to be wide spread in area, 588 00:35:01,560 --> 00:35:04,160 Speaker 1: or else you're going to end up affecting way too 589 00:35:04,239 --> 00:35:08,759 Speaker 1: much wire at once, you'll end up with having to 590 00:35:08,840 --> 00:35:12,880 Speaker 1: use way more wire to record very short sounds in 591 00:35:12,920 --> 00:35:15,960 Speaker 1: this case, and not only is that inefficient, but you'd 592 00:35:15,960 --> 00:35:18,680 Speaker 1: also run the risk of writing over stuff you've just recorded. 593 00:35:18,760 --> 00:35:22,239 Speaker 1: Let's say that you're writing something to wire. If the 594 00:35:22,440 --> 00:35:26,120 Speaker 1: magnetic field is wide enough so that it's constantly overlapping 595 00:35:26,160 --> 00:35:28,759 Speaker 1: what you just recorded, then all you're really doing is 596 00:35:28,840 --> 00:35:33,800 Speaker 1: muddling your recording with every successive sound. So a coil 597 00:35:33,840 --> 00:35:36,839 Speaker 1: of wire creates the magnetic field when electricity runs through it. 598 00:35:36,840 --> 00:35:42,600 Speaker 1: This wire is coiled around a soft magnetic material. Remember 599 00:35:42,680 --> 00:35:45,200 Speaker 1: those are the kinds of magnetic materials that are easy 600 00:35:45,280 --> 00:35:48,400 Speaker 1: to influence, but then will go back to their natural 601 00:35:48,440 --> 00:35:51,920 Speaker 1: state shortly after the magnetic field they've been exposed to 602 00:35:52,080 --> 00:35:57,560 Speaker 1: has gone away. This creates what we call a magnetic flux, 603 00:35:58,040 --> 00:36:01,400 Speaker 1: and it concentrates at the tip of the soft magnetic 604 00:36:01,440 --> 00:36:05,800 Speaker 1: material that's the core of this coil. A common design 605 00:36:05,840 --> 00:36:08,759 Speaker 1: for early recording heads was a ring that had a 606 00:36:08,840 --> 00:36:12,720 Speaker 1: small gap cut into it, and then you would wrap 607 00:36:12,800 --> 00:36:16,920 Speaker 1: the wire around the inside of this ring, like you know, 608 00:36:17,040 --> 00:36:20,040 Speaker 1: around the ring. So imagine just a regular ring. You 609 00:36:20,080 --> 00:36:23,160 Speaker 1: cut a little gap at one end. On the other end, 610 00:36:23,480 --> 00:36:26,080 Speaker 1: you've wrapped this this coil of wire and you run 611 00:36:26,080 --> 00:36:28,960 Speaker 1: electricity through it. It turns the ring into a magnet. 612 00:36:29,480 --> 00:36:33,040 Speaker 1: But the gap creates a difference in this magnetic field. 613 00:36:33,880 --> 00:36:38,200 Speaker 1: The soft material, the soft magnetic material, conducts magnetic flux 614 00:36:38,280 --> 00:36:43,480 Speaker 1: easily and the gap doesn't. This causes the magnetic flux 615 00:36:43,520 --> 00:36:47,560 Speaker 1: to do something we call fringing. It fringes. A fringe 616 00:36:47,600 --> 00:36:50,720 Speaker 1: field is a bit tricky to explain, but it's easier 617 00:36:50,719 --> 00:36:54,680 Speaker 1: to understand if you imagine a horseshoe magnet. So the 618 00:36:54,719 --> 00:36:57,759 Speaker 1: two ends of the horseshoe are the two poles, the 619 00:36:57,800 --> 00:37:00,239 Speaker 1: north pole and the south pole. The fringe field is 620 00:37:00,239 --> 00:37:04,239 Speaker 1: the magnetic field that extends outside the space between the 621 00:37:04,280 --> 00:37:08,040 Speaker 1: two poles. That would be a fringe field. Now, that 622 00:37:08,080 --> 00:37:10,560 Speaker 1: fringe field is what the right head uses to actually 623 00:37:10,600 --> 00:37:15,120 Speaker 1: record information onto the magnetic medium. Now, with sound, we're 624 00:37:15,120 --> 00:37:18,760 Speaker 1: talking about an analog approach, meaning you'd find a smooth 625 00:37:18,960 --> 00:37:23,680 Speaker 1: variability in the medium. You would create that by varying 626 00:37:23,719 --> 00:37:27,720 Speaker 1: the magnetic flux in subtle ways. The recording head adjusts 627 00:37:27,760 --> 00:37:30,279 Speaker 1: the magnetic flux by varying the current running through the 628 00:37:30,320 --> 00:37:33,160 Speaker 1: head and the recording medium thus has a variability in 629 00:37:33,200 --> 00:37:37,880 Speaker 1: the magnetic flux recorded within the wire itself. The wire 630 00:37:37,960 --> 00:37:41,640 Speaker 1: represents a sort of copy of the flux if you 631 00:37:41,680 --> 00:37:44,520 Speaker 1: were to run the wire back. So let's say you've 632 00:37:44,520 --> 00:37:48,200 Speaker 1: got the red head, the transducer that acts as a redhead, 633 00:37:48,800 --> 00:37:53,000 Speaker 1: and you run the wire next to it sequentially, so 634 00:37:53,160 --> 00:37:58,000 Speaker 1: you're just spinning one reel pulling wire across so that 635 00:37:58,040 --> 00:38:01,240 Speaker 1: this redhead is very close to it. That would create 636 00:38:01,239 --> 00:38:05,240 Speaker 1: a varying magnetic field across the gap in the red head, 637 00:38:05,680 --> 00:38:08,160 Speaker 1: and that then would create a varying magnetic field in 638 00:38:08,200 --> 00:38:11,360 Speaker 1: the core of the red head, which would induce a 639 00:38:11,440 --> 00:38:14,520 Speaker 1: current to flow through the coil of wire, which then 640 00:38:14,520 --> 00:38:18,080 Speaker 1: could be sent to an amplifier. The varying electric electrical 641 00:38:18,080 --> 00:38:20,839 Speaker 1: signal goes to a transducer such as speakers, and then 642 00:38:20,880 --> 00:38:24,840 Speaker 1: it can play back the sound. Now, those old wire 643 00:38:24,880 --> 00:38:26,520 Speaker 1: recorders moved at a pretty good clip. 644 00:38:26,840 --> 00:38:27,960 Speaker 2: The post war. 645 00:38:28,440 --> 00:38:31,319 Speaker 1: Wire recorders would play back wire at about twenty four 646 00:38:31,480 --> 00:38:35,000 Speaker 1: inches per second, so two feet of wire per second. 647 00:38:35,680 --> 00:38:38,319 Speaker 1: That's about sixty one centimeters per second for you folks 648 00:38:38,400 --> 00:38:41,120 Speaker 1: on the metric system, if you wanted to record an 649 00:38:41,120 --> 00:38:44,840 Speaker 1: hour's worth of audio, you would need seven two hundred 650 00:38:44,960 --> 00:38:48,000 Speaker 1: feet of wire or about two thy one hundred and 651 00:38:48,040 --> 00:38:52,680 Speaker 1: ninety five meters of wire, and you could only record 652 00:38:52,800 --> 00:38:56,600 Speaker 1: along one direction of the wire, so if you wanted 653 00:38:56,600 --> 00:38:59,160 Speaker 1: to listen to it again, you'd have to wind all 654 00:38:59,280 --> 00:39:02,080 Speaker 1: the wire back up up into a reel and then 655 00:39:02,320 --> 00:39:06,759 Speaker 1: play it out across a redhead all over again. Most 656 00:39:06,800 --> 00:39:10,480 Speaker 1: of these early ones were hand cranked too, so you 657 00:39:10,480 --> 00:39:12,920 Speaker 1: would get variability on the sound quality as it was 658 00:39:12,960 --> 00:39:17,160 Speaker 1: played back, plus when you were recording, so it took 659 00:39:17,160 --> 00:39:21,360 Speaker 1: a steady hand to create a decent recording and a 660 00:39:21,400 --> 00:39:25,160 Speaker 1: decent replication. And if you wanted to re record over it, 661 00:39:25,239 --> 00:39:28,320 Speaker 1: Let's say that you've you know, you recorded an hour 662 00:39:28,480 --> 00:39:31,680 Speaker 1: of someone catterwaulling, and then you're like, well, that wasn't 663 00:39:31,719 --> 00:39:33,520 Speaker 1: really worth it. I would love to use this wire 664 00:39:33,640 --> 00:39:36,799 Speaker 1: to record something else. You would first have to run 665 00:39:36,880 --> 00:39:41,080 Speaker 1: that wire by a strong permanent magnet, and that would 666 00:39:41,080 --> 00:39:43,920 Speaker 1: effectively erase the stuff that was on it before, because 667 00:39:43,960 --> 00:39:48,399 Speaker 1: the strong permanent magnet would cause all those those those 668 00:39:48,760 --> 00:39:53,480 Speaker 1: magnetic domains inside the wire to realign to the permanent 669 00:39:53,480 --> 00:39:57,960 Speaker 1: magnet's magnetic field. It essentially erases all the variability, all 670 00:39:58,000 --> 00:40:01,480 Speaker 1: the flux that was copied there before and turns it 671 00:40:01,520 --> 00:40:06,879 Speaker 1: back into a uniform medium which you then could run 672 00:40:06,920 --> 00:40:10,880 Speaker 1: through and record stuff on again. The same thing, by 673 00:40:10,880 --> 00:40:13,880 Speaker 1: the way, is true for lots of other magnetic storage media. 674 00:40:14,400 --> 00:40:14,560 Speaker 2: Now. 675 00:40:14,600 --> 00:40:18,640 Speaker 1: Eventually Polson began to work with other types of magnetic media, 676 00:40:18,760 --> 00:40:22,239 Speaker 1: and a big breakthrough came with the invention of plastic. 677 00:40:23,000 --> 00:40:25,040 Speaker 1: I say the invention of I really mean the mass 678 00:40:25,040 --> 00:40:27,640 Speaker 1: production of plastic's been around for a pretty long time, 679 00:40:27,960 --> 00:40:30,480 Speaker 1: but I'm talking about when we really started producing it 680 00:40:30,520 --> 00:40:31,360 Speaker 1: on a mass scale. 681 00:40:32,520 --> 00:40:33,760 Speaker 2: So you can use. 682 00:40:33,600 --> 00:40:37,440 Speaker 1: Plastic film coated with a ferro magnetic powder. This is 683 00:40:37,560 --> 00:40:40,759 Speaker 1: how cassette tapes, VHS tapes, even floppy disks work. You 684 00:40:40,800 --> 00:40:44,520 Speaker 1: can make a cheap recording medium this way. The invention 685 00:40:44,600 --> 00:40:47,120 Speaker 1: of the cassette tape itself was another big jump, because 686 00:40:47,160 --> 00:40:49,320 Speaker 1: engineers figured out how you could double the amount of 687 00:40:49,360 --> 00:40:52,480 Speaker 1: material you could record on a tape if you just 688 00:40:52,560 --> 00:40:55,640 Speaker 1: record it on half of it at a time. Now, 689 00:40:55,680 --> 00:40:58,439 Speaker 1: this is a little triggy to explain without the use 690 00:40:58,520 --> 00:41:00,800 Speaker 1: of visual aids, but I'll try and give it a shot. 691 00:41:01,680 --> 00:41:04,760 Speaker 1: So imagine that you've got a length of flat ribbon 692 00:41:04,840 --> 00:41:08,000 Speaker 1: in front of you. You might think of cassette that 693 00:41:08,080 --> 00:41:11,000 Speaker 1: cassette recorders are actually putting information on both sides of 694 00:41:11,040 --> 00:41:14,279 Speaker 1: the ribbon, but that's not what is happening. All the 695 00:41:14,280 --> 00:41:17,640 Speaker 1: information for Side A and Side B are on one 696 00:41:17,680 --> 00:41:20,759 Speaker 1: side of that ribbon, but they are one hundred and 697 00:41:20,840 --> 00:41:26,080 Speaker 1: eighty degrees opposite each other, side by side. So you 698 00:41:26,160 --> 00:41:29,680 Speaker 1: lay out the ribbon so it's horizontal in relation to you. 699 00:41:29,680 --> 00:41:33,279 Speaker 1: You're looking at a horizontal strip of ribbon. Imagine a 700 00:41:33,360 --> 00:41:37,319 Speaker 1: line going down the middle of that ribbon horizontally. The 701 00:41:37,360 --> 00:41:41,279 Speaker 1: top half of the ribbon is one side of the 702 00:41:41,320 --> 00:41:45,400 Speaker 1: cassette and the bottom half is the other side of 703 00:41:45,440 --> 00:41:48,160 Speaker 1: the cassette. So when you put a cassette into a 704 00:41:48,200 --> 00:41:52,640 Speaker 1: cassette player, the red head is positioned over just one 705 00:41:52,760 --> 00:41:56,640 Speaker 1: half of that tape and it reads what's off of that. 706 00:41:57,080 --> 00:42:01,680 Speaker 1: When you flip the cassette over, then and the side 707 00:42:01,680 --> 00:42:04,360 Speaker 1: of the tape that's running across the redhead is the 708 00:42:04,440 --> 00:42:08,160 Speaker 1: opposite of that. You know, it's the bottom of the 709 00:42:08,239 --> 00:42:09,960 Speaker 1: ribbon as opposed to the top of the ribbon, and 710 00:42:09,960 --> 00:42:12,919 Speaker 1: that's how you're able to listen to Side B. We're 711 00:42:12,920 --> 00:42:15,040 Speaker 1: going to take another quick break and then we'll be 712 00:42:15,120 --> 00:42:27,520 Speaker 1: back to talk more about magnetic storage. So while the 713 00:42:27,560 --> 00:42:31,240 Speaker 1: format is more or less obsolete. I'm gonna talk about 714 00:42:31,320 --> 00:42:34,440 Speaker 1: floppy disks for a bit, and that's because there are 715 00:42:34,440 --> 00:42:37,200 Speaker 1: a lot of parallels between floppy disks and cassette tapes, 716 00:42:37,200 --> 00:42:40,120 Speaker 1: which I talked about in the last section. Floppy discs, 717 00:42:40,239 --> 00:42:43,480 Speaker 1: by the way, used to come in several sizes. When 718 00:42:43,520 --> 00:42:46,040 Speaker 1: I first started using computers, the standard size and the 719 00:42:46,160 --> 00:42:48,960 Speaker 1: US was the five and a quarter inch disc. There 720 00:42:49,000 --> 00:42:51,879 Speaker 1: were larger discs that came before that, but the first 721 00:42:51,920 --> 00:42:53,680 Speaker 1: ones I ever used were five and a quarter inch. 722 00:42:54,320 --> 00:42:56,280 Speaker 1: A lot of people thought they were called floppy disks 723 00:42:56,360 --> 00:43:00,000 Speaker 1: because the outer sheath of the disc itself was flexible. 724 00:43:00,600 --> 00:43:02,360 Speaker 1: Some people even thought you could fold them up and 725 00:43:02,360 --> 00:43:05,080 Speaker 1: put them in your pocket, which technically I guess you 726 00:43:05,120 --> 00:43:07,239 Speaker 1: could do, but you wouldn't be able to use them 727 00:43:07,320 --> 00:43:10,239 Speaker 1: later because you'd mangle the disk inside and it would 728 00:43:10,280 --> 00:43:14,680 Speaker 1: no longer spend properly inside a computer, So don't do that. 729 00:43:15,360 --> 00:43:17,640 Speaker 1: Later on came the three and a half inch discs, 730 00:43:17,680 --> 00:43:20,520 Speaker 1: and these had a hard plastic casing, but they were 731 00:43:20,600 --> 00:43:24,760 Speaker 1: still floppy disks because the disk inside, the actual medium 732 00:43:24,840 --> 00:43:29,360 Speaker 1: upon which information was stored, was still this flexible material. 733 00:43:29,600 --> 00:43:32,000 Speaker 1: A lot of folks thought that these three and a 734 00:43:32,000 --> 00:43:35,600 Speaker 1: half inch discs were actually hard disks. They said, you know, 735 00:43:35,600 --> 00:43:37,480 Speaker 1: the floppy disks wereth the five and a quarter three 736 00:43:37,480 --> 00:43:40,520 Speaker 1: and a half because the plastic is sturdy, that's a 737 00:43:40,560 --> 00:43:43,760 Speaker 1: hard disk. No, that's not a hard disk. But anyway, 738 00:43:43,800 --> 00:43:46,360 Speaker 1: that's all ancient history, and you guys probably don't even 739 00:43:46,920 --> 00:43:48,880 Speaker 1: understand what I'm talking about, so get off my lawn, 740 00:43:49,760 --> 00:43:52,840 Speaker 1: all right. Inside the outer covering of these disks was 741 00:43:52,880 --> 00:43:54,320 Speaker 1: the actual disc itself. 742 00:43:54,360 --> 00:43:56,720 Speaker 2: We call the floppy. 743 00:43:56,280 --> 00:44:00,480 Speaker 1: Disks that, but they're not disc shaped. If you were 744 00:44:00,520 --> 00:44:03,719 Speaker 1: to show someone a floppy disk and they had absolutely 745 00:44:03,800 --> 00:44:07,120 Speaker 1: no context for it, they knew what the word disc meant, 746 00:44:07,480 --> 00:44:08,600 Speaker 1: they'd take one look at it and. 747 00:44:08,480 --> 00:44:10,160 Speaker 2: Say, why the heck do you call it a disc. 748 00:44:10,680 --> 00:44:12,880 Speaker 2: It's because on the inside. 749 00:44:12,680 --> 00:44:17,320 Speaker 1: There is a disc of material and it is essentially 750 00:44:17,360 --> 00:44:21,960 Speaker 1: a plastic base that's coded with ferromagnetic materials. And the 751 00:44:22,000 --> 00:44:24,759 Speaker 1: advantage of this is that if you apply a magnetic 752 00:44:24,800 --> 00:44:28,360 Speaker 1: field to it, it would record the information permanently, or 753 00:44:28,360 --> 00:44:30,680 Speaker 1: at least until you erased it and wrote over it, 754 00:44:30,880 --> 00:44:34,160 Speaker 1: or if you encountered a really strong magnetic field, and 755 00:44:34,239 --> 00:44:36,319 Speaker 1: it was a really fast way to record a lot 756 00:44:36,360 --> 00:44:42,880 Speaker 1: of information. So discs are organized into concentric rings. You 757 00:44:42,880 --> 00:44:46,719 Speaker 1: can kind of think of an old vinyl album in 758 00:44:46,760 --> 00:44:49,799 Speaker 1: the same way how the grooves slowly move inward on the. 759 00:44:51,360 --> 00:44:51,640 Speaker 2: Disc. 760 00:44:51,800 --> 00:44:56,440 Speaker 1: But in this case they're actual concentric rings of information, 761 00:44:56,719 --> 00:45:01,400 Speaker 1: not just one line that slowly, you know, swirls inward 762 00:45:01,440 --> 00:45:05,920 Speaker 1: towards the center. So when a computer is reading information back, 763 00:45:06,280 --> 00:45:08,960 Speaker 1: it can it can reference some information at the at 764 00:45:08,960 --> 00:45:11,360 Speaker 1: the front of the disc and learn exactly where a 765 00:45:11,400 --> 00:45:14,839 Speaker 1: file is located, and it can then position the read 766 00:45:14,920 --> 00:45:17,479 Speaker 1: right head directly over the appropriate part of the disc, 767 00:45:17,960 --> 00:45:19,320 Speaker 1: rather than having to go through. 768 00:45:19,160 --> 00:45:20,360 Speaker 2: The whole thing sequentially. 769 00:45:21,239 --> 00:45:23,399 Speaker 1: So with a cassette tape, if you want to listen 770 00:45:23,400 --> 00:45:27,080 Speaker 1: to a specific song, you have to wait. I mean, 771 00:45:27,080 --> 00:45:29,520 Speaker 1: you can use fast forward to speed things up, but 772 00:45:29,560 --> 00:45:32,560 Speaker 1: you can't jump straight to the track you want to 773 00:45:32,640 --> 00:45:37,200 Speaker 1: hear onlike you could with say a compact disc. Well, 774 00:45:37,520 --> 00:45:40,279 Speaker 1: in this way, a floppy disk is more like a 775 00:45:40,320 --> 00:45:44,680 Speaker 1: compact disc in that a computer can understand exactly where 776 00:45:45,000 --> 00:45:49,560 Speaker 1: the file is stored within those concentric rings and go 777 00:45:49,680 --> 00:45:53,399 Speaker 1: straight there. In other ways, it is very different from 778 00:45:53,400 --> 00:45:58,319 Speaker 1: a compact disc, but in that specific way it is similar. Now, 779 00:45:59,160 --> 00:46:01,520 Speaker 1: in other words, it's kind of lifting a record player's 780 00:46:01,560 --> 00:46:04,560 Speaker 1: needle off of one groove and skipping ahead to a 781 00:46:04,680 --> 00:46:07,000 Speaker 1: specific song on an album, lowering the needle and then 782 00:46:07,040 --> 00:46:11,239 Speaker 1: playing it, and thank goodness, record players are coming back. 783 00:46:11,880 --> 00:46:13,480 Speaker 1: So that you guys know what I'm talking about when 784 00:46:13,520 --> 00:46:16,160 Speaker 1: I say these things. This, by the way, is a 785 00:46:16,560 --> 00:46:21,200 Speaker 1: type of direct access storage, meaning the computer can get 786 00:46:21,320 --> 00:46:24,680 Speaker 1: direct access to that information in a very short amount 787 00:46:24,719 --> 00:46:28,200 Speaker 1: of time. When writing to a disc, first the drive 788 00:46:28,239 --> 00:46:32,880 Speaker 1: will use an erase coil, and this essentially just clears 789 00:46:32,880 --> 00:46:36,640 Speaker 1: a section of the storage medium for writing. So it's 790 00:46:36,719 --> 00:46:39,920 Speaker 1: kind of like exposing that steel wired to a permanent magnet. 791 00:46:40,000 --> 00:46:43,160 Speaker 1: It's that same principle. You want a clean slate to 792 00:46:43,200 --> 00:46:47,120 Speaker 1: write upon, and typically this clean slate is a bit 793 00:46:47,160 --> 00:46:50,560 Speaker 1: wider than the actual right section you're going to be 794 00:46:50,600 --> 00:46:55,040 Speaker 1: working on. You want the area that is a clean 795 00:46:55,160 --> 00:46:57,760 Speaker 1: slate to be larger so that you have a buffer 796 00:46:57,880 --> 00:47:01,000 Speaker 1: zone at either end, and that way it keeps adjacent 797 00:47:01,120 --> 00:47:04,640 Speaker 1: files from interfering with each other. If you were writing 798 00:47:04,640 --> 00:47:06,799 Speaker 1: information to that part of the disc and it went 799 00:47:06,960 --> 00:47:10,279 Speaker 1: over that area, you would start writing on top of 800 00:47:10,360 --> 00:47:14,839 Speaker 1: some other file and then the storage wouldn't work at all. 801 00:47:15,040 --> 00:47:19,080 Speaker 1: So the right head puts data on the disk drive. 802 00:47:19,120 --> 00:47:23,480 Speaker 1: By applying one of two magnetic fields to the tape, 803 00:47:24,600 --> 00:47:28,719 Speaker 1: it either aligns the magnetic material as north south or 804 00:47:28,880 --> 00:47:33,239 Speaker 1: south north. That means it's either a zero or a one. 805 00:47:34,400 --> 00:47:38,719 Speaker 1: So imagine that north south magnetization represents as zero and 806 00:47:38,880 --> 00:47:42,160 Speaker 1: south north represents a one. The right head can then 807 00:47:42,239 --> 00:47:47,160 Speaker 1: go through this disc very very quickly, applying these magnetic 808 00:47:47,200 --> 00:47:50,520 Speaker 1: fields one after the other, maybe several north south in 809 00:47:50,560 --> 00:47:54,399 Speaker 1: a row, followed by a south north or whatever, and 810 00:47:54,800 --> 00:47:58,040 Speaker 1: it is recorded on the disc itself, and when you 811 00:47:58,080 --> 00:48:02,880 Speaker 1: read it back then you know by looking at the code, oh, 812 00:48:03,360 --> 00:48:06,759 Speaker 1: these are three zeros in a row and then a one. 813 00:48:06,840 --> 00:48:10,000 Speaker 1: It replicates those zeros and ones that were recorded to 814 00:48:10,120 --> 00:48:12,520 Speaker 1: the storage medium. This, in a way is much more 815 00:48:12,600 --> 00:48:15,480 Speaker 1: simple than a variable magnetic flux because you only have 816 00:48:15,560 --> 00:48:18,959 Speaker 1: to have two magnetic states. You just have to have 817 00:48:19,000 --> 00:48:22,960 Speaker 1: something that represents a zero and something that represents a one. 818 00:48:23,280 --> 00:48:26,719 Speaker 1: No other values are accepted, so you just have to 819 00:48:26,760 --> 00:48:31,360 Speaker 1: have those two basic modes, and the same basic principles 820 00:48:31,400 --> 00:48:35,520 Speaker 1: apply to other computer magnetic storage. Magnetic hard drives use 821 00:48:35,560 --> 00:48:37,600 Speaker 1: a very similar approach to the ones I describe for 822 00:48:37,640 --> 00:48:40,919 Speaker 1: floppy drives. And you probably heard that it's a bad 823 00:48:40,960 --> 00:48:44,160 Speaker 1: idea to expose computers to strong magnetic fields. And the 824 00:48:44,160 --> 00:48:47,400 Speaker 1: big reason for this is that magnetic storage. If you 825 00:48:47,440 --> 00:48:51,640 Speaker 1: bring a strong permanent magnet close enough to magnetic storage media, 826 00:48:52,160 --> 00:48:55,440 Speaker 1: you'll erase the data that's stored there. That includes data 827 00:48:55,480 --> 00:48:59,320 Speaker 1: that's on a hard drive if it's a magnetic drive, right, 828 00:48:59,440 --> 00:49:02,280 Speaker 1: If it's a solid state drive, it's a different story. 829 00:49:02,920 --> 00:49:05,760 Speaker 1: Or if you were to take a strong permanent magnet 830 00:49:06,160 --> 00:49:10,200 Speaker 1: and threatening someone by holding a compact disc with all 831 00:49:10,239 --> 00:49:12,359 Speaker 1: their photos on it, and you're saying, if you come 832 00:49:12,360 --> 00:49:14,720 Speaker 1: any closer, I'm going to ruin your pictures by putting 833 00:49:14,719 --> 00:49:18,440 Speaker 1: this magnet up to the CD, it won't work because 834 00:49:18,480 --> 00:49:22,000 Speaker 1: the information stored on the CD is an optical format, 835 00:49:22,480 --> 00:49:26,160 Speaker 1: not magnetic, and magnets aren't going to affect it at all. 836 00:49:26,320 --> 00:49:29,600 Speaker 1: That's it for that classic episode how magnetic storage works. 837 00:49:29,640 --> 00:49:31,880 Speaker 1: I hope you enjoyed it. 838 00:49:32,360 --> 00:49:33,799 Speaker 2: Clearly still a thing. 839 00:49:34,120 --> 00:49:37,359 Speaker 1: We still use magnetic storage and lots of different applications. 840 00:49:37,920 --> 00:49:42,040 Speaker 1: But yeah, it's not uncommon to find machines that only 841 00:49:42,080 --> 00:49:44,520 Speaker 1: have solid state drives these days and not a magnetic 842 00:49:44,520 --> 00:49:48,600 Speaker 1: storage drive. But yes, very important in the history of 843 00:49:48,719 --> 00:49:53,640 Speaker 1: computers and data storage. If we're being honest. 844 00:49:53,920 --> 00:49:54,520 Speaker 2: I hope you. 845 00:49:54,520 --> 00:49:57,160 Speaker 1: Enjoyed that episode. Hope you're all well, and I'll talk 846 00:49:57,160 --> 00:49:57,720 Speaker 1: to you again. 847 00:49:58,239 --> 00:49:58,879 Speaker 2: Release It. 848 00:50:04,920 --> 00:50:09,600 Speaker 1: Tech Stuff is an iHeartRadio production. For more podcasts from iHeartRadio, 849 00:50:09,920 --> 00:50:13,640 Speaker 1: visit the iHeartRadio app, Apple Podcasts, or wherever you listen 850 00:50:13,640 --> 00:50:14,720 Speaker 1: to your favorite shows.