1 00:00:04,160 --> 00:00:07,200 Speaker 1: Get in touch with technology with tech Stuff from how 2 00:00:07,240 --> 00:00:14,200 Speaker 1: stuff works dot com. Hey there, and welcome to tech Stuff. 3 00:00:14,240 --> 00:00:18,080 Speaker 1: I'm your host, Jonathan Strickland, senior writer for how stuff 4 00:00:18,120 --> 00:00:20,920 Speaker 1: Works dot com, and today I thought it might be interesting. 5 00:00:21,239 --> 00:00:26,080 Speaker 1: So perhaps I'm mistaken to talk about data storage, specifically 6 00:00:26,120 --> 00:00:28,880 Speaker 1: magnetic storage. So there are a lot of different ways 7 00:00:28,920 --> 00:00:31,880 Speaker 1: to store data, you know, like there's always writing it down, 8 00:00:32,440 --> 00:00:34,440 Speaker 1: that's the type of data storage all the way up 9 00:00:34,479 --> 00:00:38,720 Speaker 1: to like holographic memory storage. And magnetic storage has played 10 00:00:38,720 --> 00:00:41,440 Speaker 1: a really important role in the history of technology in 11 00:00:41,479 --> 00:00:44,519 Speaker 1: general and computers in particular. So I want to focus 12 00:00:44,600 --> 00:00:47,839 Speaker 1: on how magnetic storage works. Who came up with that 13 00:00:47,960 --> 00:00:51,800 Speaker 1: idea and even dive into the science of magnets. Yes, 14 00:00:52,400 --> 00:00:56,520 Speaker 1: insane clown posse, I'm looking at you. We're gonna discover 15 00:00:56,560 --> 00:01:00,440 Speaker 1: how magnets work. So if you've been wondering since that 16 00:01:00,560 --> 00:01:03,800 Speaker 1: video I got, I got your hook up. So first, 17 00:01:03,880 --> 00:01:06,840 Speaker 1: let's talk about why magnetic storage was a necessity in 18 00:01:06,880 --> 00:01:11,200 Speaker 1: the first place. So how do you preserve information so 19 00:01:11,240 --> 00:01:14,160 Speaker 1: that you can access it again later? Because in the 20 00:01:14,200 --> 00:01:16,840 Speaker 1: old days, and I'm talking like tens of thousands of 21 00:01:16,920 --> 00:01:19,760 Speaker 1: years ago, verbal communication was where it was at you 22 00:01:19,880 --> 00:01:23,280 Speaker 1: stored all that information up in your head. Someone would 23 00:01:23,280 --> 00:01:25,400 Speaker 1: tell you something important and you had to remember it. 24 00:01:25,920 --> 00:01:28,680 Speaker 1: Perhaps they would tell you within the context of a story. 25 00:01:29,400 --> 00:01:33,119 Speaker 1: And then eventually, if you were trying to preserve information, 26 00:01:33,200 --> 00:01:35,960 Speaker 1: you would tell that same information to someone else and 27 00:01:36,040 --> 00:01:39,760 Speaker 1: pass it along. This way, this is essentially folklore. That's 28 00:01:39,800 --> 00:01:45,280 Speaker 1: how knowledge was maintained for centuries. And then way back 29 00:01:45,280 --> 00:01:48,040 Speaker 1: in the day, someone said, hey, what if we made 30 00:01:48,080 --> 00:01:51,560 Speaker 1: up some symbols to represent these sounds we're making to 31 00:01:51,600 --> 00:01:54,200 Speaker 1: communicate with each other, and then we put those symbols 32 00:01:54,200 --> 00:01:58,920 Speaker 1: into some sort of fixed format, like in a clay tablet, 33 00:01:59,800 --> 00:02:02,840 Speaker 1: And that way we can preserve the information a lot longer. 34 00:02:03,240 --> 00:02:07,600 Speaker 1: And if Bob, who's really good at making fires, can 35 00:02:07,680 --> 00:02:10,800 Speaker 1: explain how to make fires, and we we put it 36 00:02:10,840 --> 00:02:13,480 Speaker 1: down in this format, we'll be able to make fires 37 00:02:13,639 --> 00:02:17,080 Speaker 1: even if Bob does something stupid like walks off the 38 00:02:17,160 --> 00:02:21,000 Speaker 1: edge of a cliff or something. And writing was born. 39 00:02:21,760 --> 00:02:23,760 Speaker 1: It probably went a little differently from the way I 40 00:02:23,800 --> 00:02:25,560 Speaker 1: explained it, but I think I got the gist of it. 41 00:02:26,040 --> 00:02:29,720 Speaker 1: Not everyone, however, was a fan of this development. Believe 42 00:02:29,760 --> 00:02:32,600 Speaker 1: it or not. There were people who were against the 43 00:02:32,680 --> 00:02:37,200 Speaker 1: whole idea of writing stuff down. Socrates was actually a 44 00:02:37,240 --> 00:02:40,200 Speaker 1: critic of writing stuff down, or at least that's what 45 00:02:40,280 --> 00:02:45,600 Speaker 1: we hear, because Socrates didn't write anything down, his students did. Uh. 46 00:02:45,600 --> 00:02:48,600 Speaker 1: He said that the written word is fixed, and therefore 47 00:02:48,639 --> 00:02:52,200 Speaker 1: it can't defend itself or any arguments it makes, so 48 00:02:52,240 --> 00:02:56,760 Speaker 1: it's inherently flawed. If someone writes down an argument and 49 00:02:56,880 --> 00:02:59,960 Speaker 1: your access to the argument is in that written format, 50 00:03:00,360 --> 00:03:04,399 Speaker 1: and you have questions or you have attacks on that argument, 51 00:03:04,919 --> 00:03:07,919 Speaker 1: it can't defend itself. The person who wrote it could 52 00:03:08,040 --> 00:03:10,840 Speaker 1: if they were there, but if they're not there, then 53 00:03:10,880 --> 00:03:13,400 Speaker 1: the argument has to stand on its own, and therefore 54 00:03:13,600 --> 00:03:19,120 Speaker 1: it has to be less effective. Let's say that an 55 00:03:19,120 --> 00:03:21,320 Speaker 1: actual human being. He also said that if you write 56 00:03:21,320 --> 00:03:23,920 Speaker 1: stuff down, you don't have to remember it yourself, and 57 00:03:23,960 --> 00:03:27,639 Speaker 1: that makes you less intelligent, because if you're not actually 58 00:03:27,680 --> 00:03:32,639 Speaker 1: committing something to memory, you're getting super dumb. Uh. This 59 00:03:33,520 --> 00:03:35,600 Speaker 1: might sound a lot like some of the arguments people 60 00:03:35,600 --> 00:03:40,040 Speaker 1: have made about Google and the Internet, and it's absolutely correct. 61 00:03:40,160 --> 00:03:43,440 Speaker 1: Every single time we have created a new way to 62 00:03:43,800 --> 00:03:48,000 Speaker 1: permanently store data in some form or another, people have 63 00:03:49,200 --> 00:03:51,880 Speaker 1: brought up this idea that it's making us more dumb, 64 00:03:53,040 --> 00:03:55,280 Speaker 1: Like they might say, hey, Back in the day, you'd 65 00:03:55,280 --> 00:03:57,480 Speaker 1: have to remember all your phone numbers, like all the 66 00:03:57,560 --> 00:03:59,680 Speaker 1: numbers of the friends and family that you would be 67 00:03:59,680 --> 00:04:01,840 Speaker 1: calling a regular basis. But now it's all on your phone, 68 00:04:01,840 --> 00:04:04,200 Speaker 1: so you don't remember it. You may not be able 69 00:04:04,240 --> 00:04:07,120 Speaker 1: to rattle off more than two or three phone numbers 70 00:04:07,160 --> 00:04:10,080 Speaker 1: today because of that, therefore you are more dumb. I 71 00:04:10,120 --> 00:04:12,880 Speaker 1: don't subscribe to that particular argument. I think having the 72 00:04:12,960 --> 00:04:17,200 Speaker 1: accessibility of information outweighs the fact that we are no 73 00:04:17,240 --> 00:04:20,839 Speaker 1: longer able to remember it necessarily. Uh. The point I 74 00:04:20,839 --> 00:04:24,000 Speaker 1: would make is that comprehension is always more important than 75 00:04:25,000 --> 00:04:27,600 Speaker 1: being able to recall something. You might be able to 76 00:04:27,640 --> 00:04:30,280 Speaker 1: recall some information, but if you don't truly comprehend it, 77 00:04:30,279 --> 00:04:33,400 Speaker 1: it's no It's of no use to you. So I 78 00:04:33,440 --> 00:04:36,760 Speaker 1: don't think it's necessarily a measure of intelligence. It's certainly, 79 00:04:37,000 --> 00:04:39,719 Speaker 1: perhaps more of a statement about our memories than anything else. 80 00:04:40,520 --> 00:04:44,120 Speaker 1: But I'm getting off on a tangent here. So I 81 00:04:44,160 --> 00:04:48,000 Speaker 1: think the developments we've had have been phenomenal. We wouldn't 82 00:04:48,000 --> 00:04:50,720 Speaker 1: be where we are today if we were still depending 83 00:04:50,760 --> 00:04:54,400 Speaker 1: upon just telling each other the important stuff and hoping 84 00:04:54,440 --> 00:04:57,520 Speaker 1: that they would be able to then tell other people 85 00:04:57,920 --> 00:05:00,360 Speaker 1: the important stuff we just told them and in way 86 00:05:00,400 --> 00:05:05,039 Speaker 1: that was accurate and effective. We clearly wouldn't be where 87 00:05:05,040 --> 00:05:07,560 Speaker 1: we are today if we still depended upon that. And 88 00:05:07,600 --> 00:05:09,640 Speaker 1: I don't have to travel all the way across the 89 00:05:09,680 --> 00:05:12,240 Speaker 1: world to find a specific guru to learn how to 90 00:05:12,279 --> 00:05:15,680 Speaker 1: perform a particular skill. I can just go onto YouTube 91 00:05:16,080 --> 00:05:18,839 Speaker 1: and watch like thirty or forty videos until I find 92 00:05:18,839 --> 00:05:25,240 Speaker 1: one that actually makes sense. So that's progress. Take that, Socrates. Now, 93 00:05:25,240 --> 00:05:27,560 Speaker 1: throughout history, we saw many advances in the way we 94 00:05:27,600 --> 00:05:31,640 Speaker 1: store information, and as we developed more advanced technology, it 95 00:05:31,720 --> 00:05:34,800 Speaker 1: became clear that a compatible method of storing data would 96 00:05:34,839 --> 00:05:38,480 Speaker 1: be really handy. So imagine what computers would be if 97 00:05:38,520 --> 00:05:41,640 Speaker 1: they could not save information, they'd be practically useless. You 98 00:05:41,720 --> 00:05:44,920 Speaker 1: need to have a way of storing data somehow, whether 99 00:05:44,960 --> 00:05:48,599 Speaker 1: it's in magnetic storage, optical, solid state punch cards, whatever. 100 00:05:48,680 --> 00:05:53,479 Speaker 1: You need something that can record the information otherwise it's 101 00:05:53,520 --> 00:05:56,240 Speaker 1: only good for a moment. And a lot of folks 102 00:05:56,240 --> 00:05:58,960 Speaker 1: worked on this problem, and as is the case with 103 00:05:59,080 --> 00:06:02,400 Speaker 1: many technological developments, some of that work had nothing to 104 00:06:02,440 --> 00:06:06,240 Speaker 1: do with computers, but more with researching fundamental scientific questions 105 00:06:06,720 --> 00:06:10,599 Speaker 1: and finding answers to questions lead other people being able 106 00:06:10,640 --> 00:06:13,880 Speaker 1: to use that information in practical ways that we didn't anticipate. 107 00:06:14,520 --> 00:06:17,120 Speaker 1: And this is kind of another soapbox I like to 108 00:06:17,160 --> 00:06:19,680 Speaker 1: get up on, uh to argue for the importance of 109 00:06:19,720 --> 00:06:24,160 Speaker 1: exploratory science. Applied science is really interesting. Applied sciences when 110 00:06:24,200 --> 00:06:27,159 Speaker 1: you're trying to find a particular solution that will work 111 00:06:27,600 --> 00:06:30,320 Speaker 1: for some sort of problem. Right your you might be 112 00:06:30,400 --> 00:06:34,200 Speaker 1: researching whether or not a specific material would be great 113 00:06:34,640 --> 00:06:39,960 Speaker 1: to use for a particular purpose, like bulletproof material something 114 00:06:40,000 --> 00:06:43,839 Speaker 1: like that. But exploratory science, when you're not necessarily looking 115 00:06:43,880 --> 00:06:48,400 Speaker 1: for applications, is also important because we expand our knowledge 116 00:06:48,440 --> 00:06:51,920 Speaker 1: about how the universe works, and it can open up 117 00:06:51,920 --> 00:06:55,000 Speaker 1: opportunities to leverage that knowledge in ways we could not 118 00:06:55,160 --> 00:06:58,440 Speaker 1: have anticipated when we first started looking into the issue 119 00:06:58,440 --> 00:07:02,240 Speaker 1: in the first place. It's in and stuff, So I 120 00:07:02,440 --> 00:07:05,720 Speaker 1: argue that exploratory science needs to continue to be supported. 121 00:07:05,880 --> 00:07:09,360 Speaker 1: Let's uh now acknowledge all this, take a deep breath, 122 00:07:09,400 --> 00:07:14,240 Speaker 1: and get ready to jump into the strange world of magnetism. So, first, magnetism, 123 00:07:14,520 --> 00:07:20,000 Speaker 1: or more specifically, electro magnetism, is one of four fundamental 124 00:07:20,080 --> 00:07:25,320 Speaker 1: forces that govern the atomic behavior in our universe. So 125 00:07:25,360 --> 00:07:28,080 Speaker 1: the other three if you're keeping track, are the strong 126 00:07:28,160 --> 00:07:32,200 Speaker 1: nuclear force, the weak nuclear force, and gravity, And if 127 00:07:32,200 --> 00:07:35,920 Speaker 1: you want to rank those from the weakest to the strongest, 128 00:07:36,320 --> 00:07:41,000 Speaker 1: you'd start with gravity. Gravity is negligible at the atomic scale. 129 00:07:41,040 --> 00:07:44,480 Speaker 1: It's there, but it's so faint as to be almost absent. 130 00:07:45,160 --> 00:07:48,360 Speaker 1: And this is largely because gravity is dependent upon mass, 131 00:07:48,760 --> 00:07:51,680 Speaker 1: So at the atomic scale, mass masses are so small 132 00:07:51,960 --> 00:07:56,360 Speaker 1: there's barely any gravitational attraction between particles. But gravity is 133 00:07:56,400 --> 00:07:59,600 Speaker 1: kind of nifty because while it's weak, it is there. 134 00:08:00,160 --> 00:08:03,240 Speaker 1: And in fact, there's a gravitational pull on every bit 135 00:08:03,280 --> 00:08:07,080 Speaker 1: of matter from every other bit of matter in our universe. 136 00:08:07,840 --> 00:08:10,880 Speaker 1: So you, that is you listening to me right now, 137 00:08:11,280 --> 00:08:14,600 Speaker 1: you are are exerting a gravitational pull on the Sun, 138 00:08:15,440 --> 00:08:20,320 Speaker 1: and on Alpha Centauri, and on the Andromeda galaxy. You 139 00:08:20,360 --> 00:08:23,840 Speaker 1: are exerting a gravitational pull on everything else that is 140 00:08:23,960 --> 00:08:29,280 Speaker 1: matter in our universe. It's just that that gravitational pull 141 00:08:29,400 --> 00:08:32,240 Speaker 1: is so weak as to be practically nothing, but it 142 00:08:32,440 --> 00:08:36,520 Speaker 1: is there. So since gravity is something we ourselves can 143 00:08:36,559 --> 00:08:41,000 Speaker 1: and do experience in our daily lives, we categorize it 144 00:08:41,320 --> 00:08:47,480 Speaker 1: as one of the familiar forces. Now, next in the 145 00:08:47,600 --> 00:08:51,480 Speaker 1: rank from weakest to strongest, is the weak force. Now 146 00:08:51,520 --> 00:08:55,720 Speaker 1: that's responsible for nuclear beta decay and some other decay processes. 147 00:08:55,760 --> 00:08:58,440 Speaker 1: And this one's pretty difficult to explain. And since I'm 148 00:08:58,480 --> 00:09:01,160 Speaker 1: are you going to have to explain magnetism, I'm gonna 149 00:09:01,400 --> 00:09:04,320 Speaker 1: call for a pass on this one. Let's mulligan it. 150 00:09:05,120 --> 00:09:08,319 Speaker 1: But this is a force that we do not experience 151 00:09:08,360 --> 00:09:10,960 Speaker 1: firsthand in our daily lives, So this one actually falls 152 00:09:11,000 --> 00:09:16,000 Speaker 1: into the category of unfamiliar forces. Now next in strength, 153 00:09:16,280 --> 00:09:21,680 Speaker 1: so second strongest if you prefer, is the electromagnetic force, 154 00:09:21,760 --> 00:09:24,839 Speaker 1: the one will be focusing on today. Now, this is 155 00:09:24,880 --> 00:09:27,640 Speaker 1: a force that exists between all particles that have an 156 00:09:27,679 --> 00:09:31,360 Speaker 1: electric charge. So electrons, for example, will bind to a 157 00:09:31,480 --> 00:09:35,680 Speaker 1: nucleus because electrons have a negative charge, and a nucleus, 158 00:09:35,720 --> 00:09:40,280 Speaker 1: which only contains positively charged protons and neutral neutrons, is 159 00:09:40,360 --> 00:09:45,360 Speaker 1: net positive. And you know that opposites attract, so we 160 00:09:45,520 --> 00:09:50,480 Speaker 1: have the negative electrons attracted to the positive nucleus. We 161 00:09:50,679 --> 00:09:54,480 Speaker 1: can and do experience electromagnetic forces on a daily basis, 162 00:09:54,480 --> 00:09:58,200 Speaker 1: so this one is one of the familiar forces. And 163 00:09:58,440 --> 00:10:00,680 Speaker 1: then we have the strongest of them all, all the 164 00:10:00,840 --> 00:10:04,640 Speaker 1: strong nuclear force. This is the force that holds a 165 00:10:04,760 --> 00:10:09,280 Speaker 1: nucleus together it's a dominant force in various chemical reactions, 166 00:10:09,280 --> 00:10:12,439 Speaker 1: and it has to be strong because it's doing something 167 00:10:12,480 --> 00:10:18,199 Speaker 1: that's really difficult to do. It's holding together similarly charged particles. Remember, 168 00:10:18,240 --> 00:10:21,800 Speaker 1: a nucleus is a bunch of protons and neutrons. The 169 00:10:21,840 --> 00:10:25,160 Speaker 1: protons all have a positive charge. They don't want to 170 00:10:25,240 --> 00:10:28,560 Speaker 1: be and when I say want, I don't actually mean 171 00:10:28,640 --> 00:10:32,160 Speaker 1: they have motivations, but they don't want to be next 172 00:10:32,160 --> 00:10:36,280 Speaker 1: to each other. Those parts, those similar charges are repelling 173 00:10:36,320 --> 00:10:39,400 Speaker 1: one another. So the strong nuclear force has to be 174 00:10:39,480 --> 00:10:43,079 Speaker 1: stronger than the electromagnetic force in order to hold protons 175 00:10:43,160 --> 00:10:48,760 Speaker 1: together in a nucleus with a bunch of neutral charge particles. Ah, 176 00:10:48,920 --> 00:10:52,959 Speaker 1: it does have a very short range, however, so while 177 00:10:53,000 --> 00:10:56,280 Speaker 1: it's stronger than the electromagnetic force, it does, the range 178 00:10:56,320 --> 00:10:59,640 Speaker 1: does not reach very far outside of a nucleus, so 179 00:10:59,720 --> 00:11:02,480 Speaker 1: we do directly observe it in our daily lives, and 180 00:11:02,559 --> 00:11:06,120 Speaker 1: therefore it is an unfamiliar force. So gravity and electro 181 00:11:06,160 --> 00:11:10,040 Speaker 1: magnetism are familiar forces. The strong and weak nuclear forces 182 00:11:10,080 --> 00:11:16,240 Speaker 1: are unfamiliar forces. Uh So what makes electro magnetism tick 183 00:11:16,400 --> 00:11:19,040 Speaker 1: and how did we even figure out how to make 184 00:11:19,080 --> 00:11:22,599 Speaker 1: good use of it? Well, let's start by imagining a 185 00:11:22,720 --> 00:11:24,679 Speaker 1: bar magnet. A lot of this is going to go 186 00:11:24,720 --> 00:11:27,840 Speaker 1: back to stuff that you probably learned in elementary school, 187 00:11:27,840 --> 00:11:30,880 Speaker 1: middle school, high school, those physics courses, that kind of stuff, 188 00:11:30,920 --> 00:11:34,720 Speaker 1: basic science. So you've got your bar magnet. Uh, let's 189 00:11:34,760 --> 00:11:37,480 Speaker 1: just say it's a rectang. It's rectangular in shape. So 190 00:11:37,720 --> 00:11:40,960 Speaker 1: you know you've you've got uh, your north pole and 191 00:11:41,000 --> 00:11:45,000 Speaker 1: your south pole on the magnet. Um this these represent 192 00:11:45,400 --> 00:11:50,360 Speaker 1: the various charges, magnetic charges of the magnet, opposites tracked. 193 00:11:50,960 --> 00:11:54,000 Speaker 1: So if we were to bring this bar magnet close 194 00:11:54,040 --> 00:11:57,320 Speaker 1: to another bar magnet, the north end of our bar 195 00:11:57,440 --> 00:12:00,600 Speaker 1: magnet would start to exert a poll on the south 196 00:12:00,720 --> 00:12:03,920 Speaker 1: end of the other bar magnet. Or if we were 197 00:12:03,960 --> 00:12:06,760 Speaker 1: to try and bring the north pole of our magnet 198 00:12:06,800 --> 00:12:09,199 Speaker 1: close to the north pole of the second magnet, it 199 00:12:09,240 --> 00:12:12,600 Speaker 1: would push against each other, just like I was mentioning 200 00:12:12,600 --> 00:12:15,920 Speaker 1: a second ago. Now, magnets produce a field around them 201 00:12:16,040 --> 00:12:20,560 Speaker 1: that we can represent as lines of force, and those 202 00:12:20,600 --> 00:12:24,640 Speaker 1: lines exit from the north pole, loop around the magnet 203 00:12:24,960 --> 00:12:28,440 Speaker 1: and enter the south pole. A permanent magnet is always 204 00:12:28,480 --> 00:12:32,720 Speaker 1: producing the sort of magnetic field. It's it's consistent, it 205 00:12:32,800 --> 00:12:37,559 Speaker 1: doesn't waiver. Um. You may hear about things like electromagnetism. 206 00:12:37,640 --> 00:12:39,240 Speaker 1: I'll talk a little bit more about in a in 207 00:12:39,240 --> 00:12:42,680 Speaker 1: a bit, where you have to move a coil through 208 00:12:42,679 --> 00:12:46,000 Speaker 1: a varying magnetic field, will a permanent magnet creates a 209 00:12:46,040 --> 00:12:50,640 Speaker 1: consistent magnetic field unless you start doing things like moving 210 00:12:50,640 --> 00:12:52,920 Speaker 1: it around, in which case you're really just moving where 211 00:12:52,920 --> 00:12:57,840 Speaker 1: the magnetic field is. You're not actually fluctuating the field itself. Now, 212 00:12:58,520 --> 00:13:04,360 Speaker 1: inside a magnet a permanent magnet are microscopic regions called 213 00:13:04,559 --> 00:13:09,800 Speaker 1: magnetic domains, and each of these domains is essentially a 214 00:13:09,840 --> 00:13:13,880 Speaker 1: tiny magnet with its own north and south pole. Only 215 00:13:13,920 --> 00:13:18,000 Speaker 1: by aligning the poles of all of these uh magnetic 216 00:13:18,040 --> 00:13:21,640 Speaker 1: domains in a similar direction, like north south, will you 217 00:13:21,640 --> 00:13:25,640 Speaker 1: get a permanent magnet. So if you could just zoom 218 00:13:25,720 --> 00:13:28,040 Speaker 1: in on a permanent magnet, you would see all these 219 00:13:28,080 --> 00:13:32,160 Speaker 1: tiny regions that are essentially magnets that are all aligned 220 00:13:32,360 --> 00:13:36,920 Speaker 1: the same way north south. If you didn't do that, 221 00:13:37,480 --> 00:13:40,400 Speaker 1: if the alignment was mixed up so that you had, 222 00:13:40,760 --> 00:13:44,120 Speaker 1: you know, an equal mixture of north south and south north, 223 00:13:44,720 --> 00:13:46,880 Speaker 1: they would cancel each other out and you wouldn't have 224 00:13:46,920 --> 00:13:52,320 Speaker 1: a magnet. It would just be inert magnetically speaking. So, uh, 225 00:13:52,360 --> 00:13:55,080 Speaker 1: that is something that's interesting because you can actually do 226 00:13:55,200 --> 00:13:58,040 Speaker 1: that to magnets in a couple of different ways. I'll 227 00:13:58,040 --> 00:14:02,400 Speaker 1: talk about that in a second. So all of that 228 00:14:02,679 --> 00:14:08,680 Speaker 1: is changeable. Bomb bom bomb. I wrote that in my notes. 229 00:14:08,840 --> 00:14:11,760 Speaker 1: Actually I had to say it. I could show Dylan, 230 00:14:11,800 --> 00:14:14,559 Speaker 1: but he's working on something else. By the way, when 231 00:14:14,600 --> 00:14:18,320 Speaker 1: all those magnetic domains are aligned north south, what happens 232 00:14:18,320 --> 00:14:20,360 Speaker 1: if you were to cut the magnet in half right 233 00:14:20,400 --> 00:14:23,320 Speaker 1: between the north and south pole. So imagine you've got 234 00:14:23,320 --> 00:14:26,040 Speaker 1: this rectangular bar magnet. You've got you've labeled one in 235 00:14:26,120 --> 00:14:28,320 Speaker 1: the north pole, the other in the south pole. You 236 00:14:28,400 --> 00:14:33,160 Speaker 1: cut the magnet in half horizontally across, well, you would 237 00:14:33,240 --> 00:14:37,240 Speaker 1: end up with two magnets. The middle of that magnet 238 00:14:37,280 --> 00:14:40,040 Speaker 1: would become the south pole for the north end and 239 00:14:40,080 --> 00:14:42,520 Speaker 1: the north pole for the south end. That's because those 240 00:14:42,560 --> 00:14:46,320 Speaker 1: magnetic domains I was talking about, those tiny regions inside 241 00:14:46,320 --> 00:14:50,080 Speaker 1: the magnet themselves itself, those are all aligned north south. 242 00:14:50,200 --> 00:14:52,560 Speaker 1: So if you cut the magnet across, you still have 243 00:14:52,640 --> 00:14:56,880 Speaker 1: those magnetic domains lined up north south, so the overall 244 00:14:57,000 --> 00:14:59,960 Speaker 1: magnetism is preserved. You get two magnets for the price 245 00:15:00,040 --> 00:15:03,840 Speaker 1: of one, but don't cut into magnets magnets, they tend 246 00:15:03,920 --> 00:15:06,200 Speaker 1: to be at least the ones that we typically use 247 00:15:06,400 --> 00:15:08,920 Speaker 1: for things like our fridges and stuff are ceramic magnets, 248 00:15:08,920 --> 00:15:10,600 Speaker 1: and they don't cut so well unless you have like 249 00:15:10,640 --> 00:15:14,880 Speaker 1: a a diamond saw, which some of you probably do. 250 00:15:15,720 --> 00:15:19,280 Speaker 1: And and if you cut magnets normally, then disregard my warning. 251 00:15:19,280 --> 00:15:21,480 Speaker 1: I'm talking about people who don't typically do that sort 252 00:15:21,520 --> 00:15:23,160 Speaker 1: of thing. If you are going to do it, where 253 00:15:23,160 --> 00:15:28,960 Speaker 1: eye protection because that stuff can shatter anyway. Uh, if 254 00:15:29,000 --> 00:15:32,680 Speaker 1: you do that with the magnet. Essentially, each magnet has 255 00:15:32,760 --> 00:15:36,520 Speaker 1: approximately half the magnetic domains of the old magnets, so 256 00:15:37,120 --> 00:15:39,840 Speaker 1: they're not particularly you know, the the individual magnets aren't 257 00:15:39,880 --> 00:15:42,240 Speaker 1: as strong as they were when they were a single magnet. 258 00:15:42,640 --> 00:15:47,080 Speaker 1: Because you're you're magnets, You're overall magnet strength is dependent 259 00:15:47,160 --> 00:15:51,000 Speaker 1: upon the accumulative effect of the magnetic domains within it, 260 00:15:51,520 --> 00:15:56,520 Speaker 1: all right, So each of those magnet domains are tiny magnets. 261 00:15:57,680 --> 00:15:59,840 Speaker 1: There are three ways to get them to line up 262 00:16:00,240 --> 00:16:03,960 Speaker 1: so that the overall material becomes a magnet itself. Like 263 00:16:04,000 --> 00:16:06,240 Speaker 1: how you get them all to line up like north south? 264 00:16:06,720 --> 00:16:09,480 Speaker 1: So way number one is to whack on it with 265 00:16:09,520 --> 00:16:12,560 Speaker 1: something heavy, which isn't a joke. If you hold the 266 00:16:12,560 --> 00:16:14,960 Speaker 1: material in the north south direction and strike it with 267 00:16:15,000 --> 00:16:19,040 Speaker 1: a hammer, you physically realign the magnetic domains and you 268 00:16:19,120 --> 00:16:23,960 Speaker 1: can knock the material into a weak magnet. There's a 269 00:16:23,960 --> 00:16:26,080 Speaker 1: bit more to it than that, but that's the basic idea, 270 00:16:26,160 --> 00:16:27,920 Speaker 1: and that that does mean that you're not going to 271 00:16:27,960 --> 00:16:30,120 Speaker 1: get a very strong magnet as a result, but you 272 00:16:30,200 --> 00:16:35,400 Speaker 1: can physically force those magnetic domains to be in the 273 00:16:35,480 --> 00:16:39,920 Speaker 1: same direction and create a magnet that way. Way number 274 00:16:39,920 --> 00:16:43,240 Speaker 1: two is that you can place the material inside a 275 00:16:43,280 --> 00:16:46,000 Speaker 1: strong magnetic field and make sure the material is in 276 00:16:46,080 --> 00:16:49,040 Speaker 1: the north south alignment and you just leave it there 277 00:16:49,720 --> 00:16:52,520 Speaker 1: and if it's a strong magnetic field, it will start 278 00:16:52,560 --> 00:16:57,640 Speaker 1: to realign the magnetic domains within your target material so 279 00:16:57,680 --> 00:17:02,000 Speaker 1: that they gradually line up with the magnetic fields direction. 280 00:17:02,640 --> 00:17:04,120 Speaker 1: So you just have to have a strong enough one 281 00:17:04,160 --> 00:17:06,840 Speaker 1: to affect the magnetic domains in your target material and 282 00:17:06,840 --> 00:17:10,080 Speaker 1: then eventually you end up with a magnet. So that's 283 00:17:10,160 --> 00:17:13,000 Speaker 1: kind of cool. And way number three is yes, zap 284 00:17:13,080 --> 00:17:17,560 Speaker 1: it with electric current. So one hypothesis is that this 285 00:17:17,640 --> 00:17:21,280 Speaker 1: is how loadstone, which is a naturally magnetic material you 286 00:17:21,280 --> 00:17:24,960 Speaker 1: can find here on Earth, was originally formed the ideas 287 00:17:25,000 --> 00:17:29,840 Speaker 1: that loadstone, which is made up of this stuff called magnetite. Uh, 288 00:17:29,880 --> 00:17:33,000 Speaker 1: some of it was struck by lightning over the the 289 00:17:33,000 --> 00:17:37,320 Speaker 1: the millennia that Earth was forming. So you have magnetite 290 00:17:37,440 --> 00:17:40,399 Speaker 1: on the surface of the planet. Occasionally lightning strikes and 291 00:17:40,480 --> 00:17:44,280 Speaker 1: hits some of this magnetite and then magnetizes it. That 292 00:17:44,400 --> 00:17:48,480 Speaker 1: was That's one hypothesis. But there's another one which suggests 293 00:17:48,560 --> 00:17:51,520 Speaker 1: that magnetite gained its magnetic properties during the time when 294 00:17:51,560 --> 00:17:53,720 Speaker 1: Earth was forming, and it was through more of a 295 00:17:53,840 --> 00:17:57,879 Speaker 1: just a physical uh, the physical process of cooling where 296 00:17:57,920 --> 00:18:01,720 Speaker 1: these magnetic domains aligned in the proper way. Here's the thing, 297 00:18:01,960 --> 00:18:05,439 Speaker 1: we don't really know how it all got started. We 298 00:18:05,480 --> 00:18:07,840 Speaker 1: don't have that information. No one was around back then 299 00:18:07,920 --> 00:18:10,800 Speaker 1: to write it down or put it in magnetic storage. 300 00:18:11,040 --> 00:18:13,600 Speaker 1: So it's still a bit of a mystery. But we 301 00:18:13,680 --> 00:18:16,399 Speaker 1: do know that those are two possible ways that this 302 00:18:16,440 --> 00:18:20,479 Speaker 1: could have come about. And uh, you can also render 303 00:18:20,600 --> 00:18:25,119 Speaker 1: magnets inert by changing the alignment of the magnetic domains 304 00:18:25,160 --> 00:18:28,080 Speaker 1: within it. If you heat a magnet up beyond its 305 00:18:28,160 --> 00:18:32,560 Speaker 1: cury point, which is different for different magnetic materials, it 306 00:18:32,680 --> 00:18:36,400 Speaker 1: loses its magnetism. The heat warps the material and makes 307 00:18:36,440 --> 00:18:40,120 Speaker 1: the magnetic domains fall out of alignment. So what used 308 00:18:40,119 --> 00:18:42,960 Speaker 1: to be magnetic will no longer be. So something that 309 00:18:42,960 --> 00:18:45,639 Speaker 1: would stick to your fridge no problem, will just slide 310 00:18:45,680 --> 00:18:48,959 Speaker 1: off and hit the floor, and everyone will be sad, 311 00:18:49,560 --> 00:18:51,879 Speaker 1: unless you just did it as a scientific experiment, in 312 00:18:51,880 --> 00:18:53,359 Speaker 1: which case you might be happy that you've got the 313 00:18:53,400 --> 00:18:59,320 Speaker 1: result you expected. Now we can experience magnetism because of electrons. 314 00:18:59,520 --> 00:19:03,280 Speaker 1: This time, negatively charged sub atomic particles hold the key 315 00:19:03,440 --> 00:19:06,760 Speaker 1: to whether a material is affected by magnets or isn't. 316 00:19:07,440 --> 00:19:09,960 Speaker 1: You know, might wonder like, why are some things magnetic 317 00:19:10,040 --> 00:19:12,359 Speaker 1: and some things aren't? Why do magnets stick to some 318 00:19:12,440 --> 00:19:15,879 Speaker 1: materials but slide right off of other materials? And ultimately 319 00:19:16,320 --> 00:19:23,360 Speaker 1: the answer falls with electrons. Now, electrons orbit the nucleus 320 00:19:24,160 --> 00:19:27,520 Speaker 1: right in the atoms. You remember your basic description of 321 00:19:27,520 --> 00:19:29,480 Speaker 1: an atom, where you have a nucleus at the center 322 00:19:29,560 --> 00:19:34,679 Speaker 1: and electrons orbiting at different orbital shells around the electrons. Typically, 323 00:19:35,280 --> 00:19:39,080 Speaker 1: electrons will pair up with other electrons. You'll get pairs 324 00:19:39,160 --> 00:19:43,280 Speaker 1: of electrons. They have a state that's called spin, and 325 00:19:43,400 --> 00:19:46,080 Speaker 1: each electron in a pair has the opposite spin of 326 00:19:46,119 --> 00:19:49,480 Speaker 1: its partner. So we can describe spin as up or down. 327 00:19:49,640 --> 00:19:52,880 Speaker 1: For example, if one electron is spinning up, the other 328 00:19:52,920 --> 00:19:56,679 Speaker 1: one by necessity has to be spinning down. You cannot 329 00:19:56,720 --> 00:19:59,639 Speaker 1: get both electrons in a pair to spin in the 330 00:19:59,720 --> 00:20:03,160 Speaker 1: same direction in the same orbital That just that ain't cricket. 331 00:20:03,680 --> 00:20:06,199 Speaker 1: It's part of the quantum mechanical principle we call the 332 00:20:06,320 --> 00:20:10,119 Speaker 1: poly exclusion principle. And until I did a research for 333 00:20:10,160 --> 00:20:12,040 Speaker 1: this show, I could have sworn that referred to the 334 00:20:12,040 --> 00:20:15,480 Speaker 1: practice of non inviting Polly shortier parties. So I guess 335 00:20:15,520 --> 00:20:18,200 Speaker 1: you've learned something new every day. That got a smirk 336 00:20:18,640 --> 00:20:22,639 Speaker 1: from Dylan. It's maybe he'll laugh when he listens to 337 00:20:22,680 --> 00:20:26,320 Speaker 1: it the second time. Uh. Some elements have an unpaired 338 00:20:26,359 --> 00:20:29,040 Speaker 1: electron in an orbital just because that's just how it 339 00:20:29,080 --> 00:20:34,320 Speaker 1: works out. So those unpaired spinning electrons generate a very 340 00:20:34,359 --> 00:20:39,080 Speaker 1: tiny magnetic field, and we call it an orbital magnetic moment, 341 00:20:39,160 --> 00:20:41,800 Speaker 1: which sounds like something you'd expect in a romantic science 342 00:20:41,800 --> 00:20:47,720 Speaker 1: fiction film. Iron, for example, has four unpaired electrons that 343 00:20:47,880 --> 00:20:52,119 Speaker 1: all have the same spin. Those four unpaired electrons have 344 00:20:52,200 --> 00:20:56,560 Speaker 1: an orbital magnetic moment. So magnetic moment has a magnitude 345 00:20:56,720 --> 00:21:00,280 Speaker 1: and the direction, which means it is a vector. The 346 00:21:00,280 --> 00:21:03,040 Speaker 1: bottom line is this vector refers to the strength of 347 00:21:03,080 --> 00:21:06,760 Speaker 1: the magnetic field and the torque it can exert. So 348 00:21:06,840 --> 00:21:10,199 Speaker 1: a permanent magnets magnetic moments are composed of all the 349 00:21:10,240 --> 00:21:14,040 Speaker 1: moments of its atoms. In other words, you've got all 350 00:21:14,080 --> 00:21:18,199 Speaker 1: these atoms that represent an orbital magnetic moment because of 351 00:21:18,240 --> 00:21:21,439 Speaker 1: the spin of the electrons of the unpaired electrons. If 352 00:21:21,440 --> 00:21:23,800 Speaker 1: you've got enough of them and they're aligned the right way, 353 00:21:23,880 --> 00:21:29,000 Speaker 1: that determines the permanent magnets magnetic moments. So iron and 354 00:21:29,040 --> 00:21:33,280 Speaker 1: several other magnetic elements have a crystalline structure, right, so 355 00:21:33,560 --> 00:21:37,120 Speaker 1: think of it like scaffolding. It makes this very ordered 356 00:21:37,200 --> 00:21:40,680 Speaker 1: kind of structure as opposed to something that looks much 357 00:21:40,680 --> 00:21:44,639 Speaker 1: more chaotic. So as iron cools from a molten state, 358 00:21:45,040 --> 00:21:49,159 Speaker 1: atoms line up into this crystalline arrangement, and groups of 359 00:21:49,200 --> 00:21:52,280 Speaker 1: atoms that have a parallel orbital spin will line up 360 00:21:52,320 --> 00:21:55,840 Speaker 1: within the crystal and those form those magnetic domains I 361 00:21:55,880 --> 00:21:59,480 Speaker 1: mentioned earlier. The qualities that make good magnets are also 362 00:21:59,560 --> 00:22:03,000 Speaker 1: the same ones as the qualities that make materials attracted 363 00:22:03,119 --> 00:22:06,159 Speaker 1: to magnets. So a strong magnet will attract iron and 364 00:22:06,240 --> 00:22:10,560 Speaker 1: other elements that have these orbital magnetic moments in alignment. Now, 365 00:22:10,600 --> 00:22:14,600 Speaker 1: not all permanent magnets are equal. The ceramic magnets you 366 00:22:14,640 --> 00:22:16,800 Speaker 1: may have on your fringe door a pretty weak all 367 00:22:16,840 --> 00:22:20,199 Speaker 1: things considered. They're made of a mixture of iron oxide 368 00:22:20,240 --> 00:22:24,439 Speaker 1: and a ceramic composite. These are ferric magnets, that's what 369 00:22:24,480 --> 00:22:26,760 Speaker 1: we call them, ferric for the iron that's in them. 370 00:22:27,040 --> 00:22:30,879 Speaker 1: But on the other end of the scale are neodymium magnets, 371 00:22:30,880 --> 00:22:34,720 Speaker 1: a rare earth element magnet there is much much stronger 372 00:22:34,760 --> 00:22:37,600 Speaker 1: than the ferric magnets we tend to use, and they 373 00:22:37,640 --> 00:22:42,800 Speaker 1: typically contain a mixture of neodymium, iron and boron. They 374 00:22:42,840 --> 00:22:47,040 Speaker 1: could be really strong too, uh, I have played with somewhere. 375 00:22:47,440 --> 00:22:49,960 Speaker 1: If they get into contact with something like a metal table, 376 00:22:50,600 --> 00:22:54,000 Speaker 1: it can be really hard to remove them. We had 377 00:22:54,040 --> 00:22:59,560 Speaker 1: some here at how Stuff Works that were potentially causing injuries. Uh. 378 00:22:59,720 --> 00:23:02,200 Speaker 1: One person slipped one in their pocket and then found 379 00:23:02,240 --> 00:23:05,320 Speaker 1: themselves stuck to a filing cabinet for a little bit. Uh. 380 00:23:05,359 --> 00:23:08,280 Speaker 1: This was way back in the day, but it was 381 00:23:08,320 --> 00:23:09,720 Speaker 1: one of those things where a lot of us didn't 382 00:23:09,720 --> 00:23:11,280 Speaker 1: have a whole lot of experience with it because at 383 00:23:11,320 --> 00:23:14,760 Speaker 1: the time they were fairly uncommon. Today you can order 384 00:23:15,000 --> 00:23:19,679 Speaker 1: neodymium and other rare earth magnets online without much trouble. 385 00:23:20,160 --> 00:23:23,400 Speaker 1: But when I started um, first of all, how stuff 386 00:23:23,440 --> 00:23:26,000 Speaker 1: works was easy because there are only three things, so 387 00:23:26,480 --> 00:23:28,439 Speaker 1: it was easy to explain how stuff works. Once you 388 00:23:28,440 --> 00:23:31,160 Speaker 1: wrote the three articles, you were done. But over time 389 00:23:31,160 --> 00:23:34,680 Speaker 1: more stuff was made and we had more work to do, 390 00:23:35,080 --> 00:23:39,040 Speaker 1: and at that point it was more. It was more 391 00:23:39,160 --> 00:23:43,320 Speaker 1: uh uh, well, it was easier to get ahold of 392 00:23:43,359 --> 00:23:47,400 Speaker 1: neodymium magnets at that point. Now, some materials are called 393 00:23:47,440 --> 00:23:50,960 Speaker 1: temporary or soft magnets, and those will produce a magnetic 394 00:23:51,000 --> 00:23:53,840 Speaker 1: field in the presence of another magnetic field and retain 395 00:23:53,960 --> 00:23:57,400 Speaker 1: some of that magnetism for a while after they leave 396 00:23:57,480 --> 00:24:00,800 Speaker 1: the field itself, so they're very easy to LUNs. So 397 00:24:00,920 --> 00:24:03,879 Speaker 1: imagine that you've got something like a paper clip and 398 00:24:03,920 --> 00:24:06,600 Speaker 1: you put it within the range of a magnetic field 399 00:24:06,600 --> 00:24:11,480 Speaker 1: for a while, and it starts to have its magnetic 400 00:24:12,320 --> 00:24:15,919 Speaker 1: domains aligned according to this magnetic field. You remove it 401 00:24:16,119 --> 00:24:18,040 Speaker 1: and you find you can pick up other paper clips 402 00:24:18,040 --> 00:24:19,959 Speaker 1: with it, but only for a little while, and then 403 00:24:20,000 --> 00:24:24,720 Speaker 1: it stops working. That's that's very typical with soft or 404 00:24:24,800 --> 00:24:29,600 Speaker 1: temporary magnets, they very quickly will change, but then they 405 00:24:29,600 --> 00:24:31,800 Speaker 1: will over time change back to being, let you know, 406 00:24:31,840 --> 00:24:38,520 Speaker 1: not magnetic. But if they're also hard magnetic materials, these 407 00:24:38,680 --> 00:24:41,840 Speaker 1: it's harder to change them, but then they will stay 408 00:24:42,000 --> 00:24:45,679 Speaker 1: changed for longer. So stuff like iron, if you're able 409 00:24:45,720 --> 00:24:50,200 Speaker 1: to really realign those magnetic domains and iron magnet will 410 00:24:50,240 --> 00:24:54,640 Speaker 1: hold that magnetic ability much much longer. And that's how 411 00:24:54,680 --> 00:24:56,919 Speaker 1: you can end up with permanent magnets as opposed to 412 00:24:56,960 --> 00:25:00,760 Speaker 1: some that will just temporarily be magnetic. Um it's kind 413 00:25:00,760 --> 00:25:04,199 Speaker 1: of interesting. Uh. So then you've got electro magnets and 414 00:25:04,280 --> 00:25:06,959 Speaker 1: this will only produce the magnetic field in the presence 415 00:25:06,960 --> 00:25:11,560 Speaker 1: of electricity. And I'm sure everyone listening to this has 416 00:25:11,600 --> 00:25:16,080 Speaker 1: done some variation on the the experiment where you take 417 00:25:16,119 --> 00:25:20,080 Speaker 1: an iron nail and you coil some wire around it, 418 00:25:20,160 --> 00:25:24,720 Speaker 1: usually some insulated copper wire around the nail several times, uh, 419 00:25:24,760 --> 00:25:27,240 Speaker 1: and then you run an electric current through the wire 420 00:25:27,359 --> 00:25:30,960 Speaker 1: and you create an electro magnet. The nail becomes magnetic 421 00:25:31,359 --> 00:25:33,320 Speaker 1: and you can pick up all sorts of stuff with it. 422 00:25:33,800 --> 00:25:37,240 Speaker 1: The strength of the magnetic field is dependent upon the 423 00:25:37,320 --> 00:25:42,040 Speaker 1: number of coils around the nail as well as some 424 00:25:42,080 --> 00:25:45,359 Speaker 1: other factors, but that's the primary one. Uh. And UH, 425 00:25:45,520 --> 00:25:48,200 Speaker 1: you know it's it's a cool, little basic science experiment 426 00:25:48,240 --> 00:25:51,679 Speaker 1: you can run, but it's also the basis of a 427 00:25:51,880 --> 00:25:59,520 Speaker 1: ton of the work done in electrical fields, including general electronics, computers, storage. 428 00:26:00,359 --> 00:26:08,480 Speaker 1: It is an important fundamental piece of technology. UH. And 429 00:26:08,680 --> 00:26:12,920 Speaker 1: the very simple applications of this you can find in 430 00:26:13,000 --> 00:26:19,520 Speaker 1: stuff like electric transformers or electric motors and dynamos. Like transformer, 431 00:26:19,760 --> 00:26:24,399 Speaker 1: you can have two different coils of wire, one that 432 00:26:24,680 --> 00:26:27,239 Speaker 1: is got a lot more coils to it, uh, like 433 00:26:27,320 --> 00:26:30,560 Speaker 1: maybe twice as many as the second one, And when 434 00:26:30,760 --> 00:26:35,120 Speaker 1: you run a current through the the larger number of coils, 435 00:26:35,560 --> 00:26:39,520 Speaker 1: the magnetic field it generates induces electricity to flow through 436 00:26:39,560 --> 00:26:43,360 Speaker 1: the second set of coils, but steps down the voltage 437 00:26:43,920 --> 00:26:48,160 Speaker 1: because you have half as many coils around a core 438 00:26:48,280 --> 00:26:50,840 Speaker 1: as you do with the first one. Uh. That's how 439 00:26:50,880 --> 00:26:53,880 Speaker 1: you can step down or step up voltage. And that's 440 00:26:53,880 --> 00:26:58,119 Speaker 1: why alternating current ends up being much more effective for 441 00:26:58,320 --> 00:27:02,800 Speaker 1: distributing electricity across the distances than direct current, because you 442 00:27:02,800 --> 00:27:05,040 Speaker 1: can't do that with direct current. You need that alternating 443 00:27:06,080 --> 00:27:08,960 Speaker 1: electric current in order to create the magnetic field that 444 00:27:09,000 --> 00:27:13,639 Speaker 1: will induce electricity to flow through a separate set of coils. 445 00:27:13,680 --> 00:27:18,480 Speaker 1: Just like you need a varying magnetic field to induce electricity, 446 00:27:18,720 --> 00:27:22,720 Speaker 1: you need that varying electricity to produce a varying magnetic field. 447 00:27:23,040 --> 00:27:27,919 Speaker 1: It's this interesting relationship, a fundamental relationship in our universe 448 00:27:27,920 --> 00:27:32,320 Speaker 1: between electricity and magnetism. And uh, that's why I was 449 00:27:32,320 --> 00:27:34,359 Speaker 1: saying before. If you have a permanent magnet and you 450 00:27:34,440 --> 00:27:38,000 Speaker 1: just put it next to a coil of wire, it's 451 00:27:38,040 --> 00:27:41,160 Speaker 1: not going to induce electricity to flow apart from when 452 00:27:41,200 --> 00:27:44,080 Speaker 1: you first introduce the magnetic field to the coil, because 453 00:27:44,080 --> 00:27:49,240 Speaker 1: it's not varying. You'd have to spin the the permanent magnet, 454 00:27:49,600 --> 00:27:53,800 Speaker 1: which would uh, you know, effectively, according to the coil's perspective, 455 00:27:53,960 --> 00:27:58,720 Speaker 1: change the alignment of that magnetic field. That would induce 456 00:27:58,800 --> 00:28:02,240 Speaker 1: electricity to flow through the wire. But just having a 457 00:28:03,320 --> 00:28:06,440 Speaker 1: standard magnet staying perfectly still next to wire, you don't 458 00:28:06,480 --> 00:28:09,840 Speaker 1: get the electricity to flow that way. And that is 459 00:28:10,359 --> 00:28:14,679 Speaker 1: a very important aspect to memory storage as well. And 460 00:28:14,760 --> 00:28:17,560 Speaker 1: that's our lesson on the physics of magnets. Without diving 461 00:28:17,600 --> 00:28:20,840 Speaker 1: too deeply into quantum mechanics, I think we're ready to 462 00:28:20,840 --> 00:28:23,879 Speaker 1: talk about our use of magnets with electronics. But first 463 00:28:24,440 --> 00:28:35,560 Speaker 1: let's take a quick break to thank our sponsor. All right, 464 00:28:35,600 --> 00:28:39,120 Speaker 1: we're back, and we just learned how magnets work in general, 465 00:28:39,200 --> 00:28:41,400 Speaker 1: But when did we figure out they could be useful 466 00:28:41,440 --> 00:28:45,239 Speaker 1: for storing information? So I'm gonna skip over all the 467 00:28:45,320 --> 00:28:48,400 Speaker 1: historic uses of magnets leading up to data storage because 468 00:28:48,440 --> 00:28:52,760 Speaker 1: I cannot spend another hour talking about compasses, or ironically, 469 00:28:52,880 --> 00:28:55,920 Speaker 1: i'll lose Dylan here in the studio. So in the 470 00:28:56,040 --> 00:29:00,240 Speaker 1: late nineteenth century we saw a boom in innovation that 471 00:29:00,400 --> 00:29:03,760 Speaker 1: was mid to late nineteenth century was a crazy time 472 00:29:04,000 --> 00:29:09,640 Speaker 1: in the world really for inventors discovering not just fundamental 473 00:29:09,680 --> 00:29:13,360 Speaker 1: principles of science, but how to apply them in technology. 474 00:29:13,560 --> 00:29:16,400 Speaker 1: I'm talking about stuff like Samuel Moore successfully sending an 475 00:29:16,440 --> 00:29:20,080 Speaker 1: electrical signal that could be decoded into communication, all the 476 00:29:20,120 --> 00:29:23,360 Speaker 1: way up to Alexander Graham Bell showing that electricity could 477 00:29:23,360 --> 00:29:26,320 Speaker 1: also be used to carry audio signals and then be 478 00:29:26,520 --> 00:29:30,760 Speaker 1: converted from electricity back into audio signals. That really got 479 00:29:30,760 --> 00:29:34,880 Speaker 1: things moving. And over at Thomas Edison's Menlo Park, a 480 00:29:34,920 --> 00:29:38,960 Speaker 1: guy named Oberlin Smith got a gander at a cylinder 481 00:29:39,000 --> 00:29:43,040 Speaker 1: phonograph and got some interesting ideas. So first let's talk 482 00:29:43,040 --> 00:29:48,320 Speaker 1: about this cylinder phonograph. It would record sound by transforming 483 00:29:48,480 --> 00:29:52,320 Speaker 1: audio waves into electrical signals. That would then cause a 484 00:29:52,400 --> 00:29:56,680 Speaker 1: needle to etch grooves into a wax cylinder. So you've 485 00:29:56,680 --> 00:30:00,400 Speaker 1: got this wax cylinder. It would slowly spin, a needle 486 00:30:00,440 --> 00:30:02,760 Speaker 1: would be dragged across it, and as sound came in, 487 00:30:02,800 --> 00:30:05,640 Speaker 1: it would cause the needle to wiggle around and that 488 00:30:05,800 --> 00:30:11,200 Speaker 1: should cause variations in the etching on the wax cylinder itself. Now, 489 00:30:11,200 --> 00:30:13,480 Speaker 1: when you took that cylinder out and you put it 490 00:30:13,520 --> 00:30:16,440 Speaker 1: in another phonograph and you placed a needle on it, 491 00:30:17,320 --> 00:30:19,880 Speaker 1: uh within the groove and he started to earn the 492 00:30:19,920 --> 00:30:23,520 Speaker 1: thing the cylinder, the needle would start to shake because 493 00:30:23,520 --> 00:30:28,040 Speaker 1: it's following the groove that was made by the previous recording. Essentially, 494 00:30:28,080 --> 00:30:31,440 Speaker 1: that whole process would be reversed. The shaky needle would 495 00:30:31,440 --> 00:30:35,480 Speaker 1: generate an electrical signal which would then go to a 496 00:30:36,240 --> 00:30:39,440 Speaker 1: essentially a speaker a diaphragm and cause it to vibrate 497 00:30:39,920 --> 00:30:42,160 Speaker 1: and that would generate the sound. So you would get 498 00:30:42,200 --> 00:30:44,440 Speaker 1: a replica of the sound you made when you were 499 00:30:44,480 --> 00:30:49,920 Speaker 1: speaking into the wax cylinder phonograph. Now, Oberlin Smith wondered 500 00:30:49,960 --> 00:30:51,840 Speaker 1: if he might be able to do the same thing, 501 00:30:52,000 --> 00:30:56,600 Speaker 1: only instead of using a wax cylinder, he would record 502 00:30:56,720 --> 00:31:01,440 Speaker 1: sound onto magnetic wire, not ape, not a disk, but 503 00:31:01,520 --> 00:31:07,320 Speaker 1: an actual length of wire using magnetism. Now, he was 504 00:31:07,360 --> 00:31:11,880 Speaker 1: not successful in this attempt, but he published his ideas 505 00:31:12,120 --> 00:31:17,320 Speaker 1: in a journal called Electrical World in eight and ten 506 00:31:17,400 --> 00:31:22,960 Speaker 1: years later a Dutch inventor inventor named Valdemar Poulson gave 507 00:31:22,960 --> 00:31:27,880 Speaker 1: it another go. He began a working magnet recorder. He 508 00:31:28,160 --> 00:31:32,200 Speaker 1: started building it. He called it the telegraphone Poulson, and 509 00:31:32,240 --> 00:31:34,880 Speaker 1: he filed a patent for this invention in eighteen nine. 510 00:31:35,560 --> 00:31:38,040 Speaker 1: So one year after he started working on it, he 511 00:31:38,120 --> 00:31:42,760 Speaker 1: showed it off at the nineteen hundred Paris Exhibition. So 512 00:31:43,200 --> 00:31:46,080 Speaker 1: how did it work? What exactly was it doing? How 513 00:31:46,160 --> 00:31:50,480 Speaker 1: was it preserving this audio information in a magnetic format 514 00:31:50,680 --> 00:31:53,680 Speaker 1: so that it could be played back? Well? Paulson knew 515 00:31:53,760 --> 00:31:57,120 Speaker 1: that he needed a magnetically hard material. If you remember 516 00:31:57,120 --> 00:31:59,200 Speaker 1: what I was talking about before the break, that's a 517 00:31:59,280 --> 00:32:03,560 Speaker 1: material that we're retain its magnetic moment indefinitely. It may 518 00:32:03,680 --> 00:32:08,600 Speaker 1: very gradually revert back to its original status, but it 519 00:32:08,640 --> 00:32:11,280 Speaker 1: will hold it over a great deal of time. And 520 00:32:11,320 --> 00:32:14,200 Speaker 1: if you want to record data for later retrieval, obviously 521 00:32:14,240 --> 00:32:17,040 Speaker 1: you want to make sure that that data remains intact. 522 00:32:17,800 --> 00:32:20,640 Speaker 1: Otherwise you have a self destructing or at least a 523 00:32:20,720 --> 00:32:24,760 Speaker 1: self erasing message on your hands. So Poulson had to 524 00:32:24,800 --> 00:32:27,840 Speaker 1: experiment with various factors to make certain he could record 525 00:32:27,960 --> 00:32:31,400 Speaker 1: anything to the medium. To begin with, if the medium 526 00:32:31,400 --> 00:32:35,120 Speaker 1: has a coercivity factor that's very high, that means you 527 00:32:35,120 --> 00:32:39,760 Speaker 1: have to use stronger magnetic fields to affect it. I'm 528 00:32:39,800 --> 00:32:42,080 Speaker 1: always talk about magnetic fields. Now I'm thinking about the 529 00:32:42,080 --> 00:32:44,680 Speaker 1: Book of Love. It's great song by a group called 530 00:32:44,680 --> 00:32:47,640 Speaker 1: the Magnetic Fields. Back back to this. So you have 531 00:32:47,640 --> 00:32:49,720 Speaker 1: to have a really strong magnetic field in order to 532 00:32:49,760 --> 00:32:54,480 Speaker 1: affect that material, and uh, that can be difficult. It 533 00:32:54,560 --> 00:32:56,760 Speaker 1: can start to eat in on your efficiency. And you 534 00:32:56,800 --> 00:32:59,240 Speaker 1: need the magnetic information to be distinct enough so that 535 00:32:59,320 --> 00:33:02,719 Speaker 1: you could get a would replay signal. And uh, you know, 536 00:33:02,760 --> 00:33:04,880 Speaker 1: when you're reading the material back later, you want to 537 00:33:04,920 --> 00:33:07,080 Speaker 1: make sure you can actually hear what was recorded and 538 00:33:07,200 --> 00:33:12,200 Speaker 1: not just get some sort of muffled you know, simulation 539 00:33:12,480 --> 00:33:15,200 Speaker 1: of the of the sounds you made. So to record 540 00:33:15,200 --> 00:33:19,520 Speaker 1: information onto a wire, you first need a recording head. 541 00:33:19,880 --> 00:33:23,600 Speaker 1: You need something that's going to generate a magnetic flux 542 00:33:24,120 --> 00:33:27,200 Speaker 1: that can affect the medium you're using the wire in 543 00:33:27,240 --> 00:33:30,360 Speaker 1: this case. This, by the way, is also true for 544 00:33:30,400 --> 00:33:34,120 Speaker 1: other methods of magnetic storage, including cassette tapes, VHS tapes, 545 00:33:34,160 --> 00:33:37,360 Speaker 1: floppy disks, and some hard drives. When I say some 546 00:33:37,440 --> 00:33:41,000 Speaker 1: hard drives, I mean magnetic hard drives. Obviously there solid 547 00:33:41,040 --> 00:33:43,560 Speaker 1: state hard drives that are not affected in this way. 548 00:33:43,560 --> 00:33:46,960 Speaker 1: They don't use that that technology, they are not part 549 00:33:47,000 --> 00:33:52,000 Speaker 1: of this discussion. So the recording head is a transducer, 550 00:33:52,920 --> 00:33:57,040 Speaker 1: and basically a transducer is something that converts some physical 551 00:33:57,120 --> 00:34:01,480 Speaker 1: quantity into an electrical signal, or as the reverse, So 552 00:34:01,560 --> 00:34:04,760 Speaker 1: you might have a transducer that can measure pressure like 553 00:34:04,840 --> 00:34:08,319 Speaker 1: air pressure and change that into an electrical signal. That's 554 00:34:08,360 --> 00:34:11,319 Speaker 1: a transducer. But in this case we're talking about things 555 00:34:11,320 --> 00:34:15,120 Speaker 1: like a microphone a transducer, and a microphone converts pressure 556 00:34:15,200 --> 00:34:20,080 Speaker 1: from sound waves into electrical signals. With recording devices, you 557 00:34:20,080 --> 00:34:23,480 Speaker 1: can use one transducer to pull double duty one of them. 558 00:34:24,080 --> 00:34:27,200 Speaker 1: It can act as both a recording head when recording, 559 00:34:27,320 --> 00:34:30,560 Speaker 1: so it's it's actually writing something to the storage medium, 560 00:34:30,800 --> 00:34:33,560 Speaker 1: or it could be a read head when playing a 561 00:34:33,600 --> 00:34:36,359 Speaker 1: signal back. It's reading the signal and then converting it 562 00:34:36,400 --> 00:34:39,280 Speaker 1: back into whatever it was originally before it was stored 563 00:34:39,360 --> 00:34:43,720 Speaker 1: in that format. Now these days, most recording devices still 564 00:34:43,840 --> 00:34:47,799 Speaker 1: use that are still using magnetic storage, have a dedicated 565 00:34:48,040 --> 00:34:51,680 Speaker 1: recording head and a dedicated read head so that each 566 00:34:51,719 --> 00:34:54,719 Speaker 1: transducer can be optimized for its respective role. You don't 567 00:34:54,760 --> 00:34:58,920 Speaker 1: see a whole lot of them where it's doing both things. Uh. 568 00:34:59,120 --> 00:35:02,319 Speaker 1: Some very cheap electronics, probably because then you don't have 569 00:35:02,400 --> 00:35:04,759 Speaker 1: to have as many components in It makes it less 570 00:35:04,760 --> 00:35:08,799 Speaker 1: expensive to produce. Now, the right head's job, or the 571 00:35:08,840 --> 00:35:12,080 Speaker 1: recording head if you prefer, is to convert electric current 572 00:35:12,320 --> 00:35:15,440 Speaker 1: into a magnetic field. But you remember what we said 573 00:35:15,480 --> 00:35:19,160 Speaker 1: about electro magnets, that's pretty easy to do. The field 574 00:35:19,200 --> 00:35:22,520 Speaker 1: it generates needs to be strong enough to affect the 575 00:35:22,600 --> 00:35:26,160 Speaker 1: storage medium, the wire, but also it has to fall 576 00:35:26,280 --> 00:35:29,160 Speaker 1: off quickly as you move away from the recording head. 577 00:35:29,160 --> 00:35:32,200 Speaker 1: In other words, you don't want the effect to be 578 00:35:32,640 --> 00:35:36,440 Speaker 1: widespread in area, or else you're going to end up 579 00:35:36,480 --> 00:35:40,160 Speaker 1: affecting way too much wire at once. You'll end up 580 00:35:40,680 --> 00:35:43,920 Speaker 1: with having to use way more wire to record very 581 00:35:43,960 --> 00:35:48,719 Speaker 1: short sounds. In this case, and not only is that inefficient, 582 00:35:48,760 --> 00:35:51,000 Speaker 1: but you'd also run the risk of writing over stuff 583 00:35:51,040 --> 00:35:53,800 Speaker 1: you've just recorded. Let's say that you're writing something to wire. 584 00:35:54,600 --> 00:35:57,919 Speaker 1: If the magnetic field is wide enough so that it's 585 00:35:57,960 --> 00:36:01,439 Speaker 1: constantly overlapping what you just corded, then all you're really 586 00:36:01,480 --> 00:36:06,440 Speaker 1: doing is muddling your recording with every successive sound. So 587 00:36:06,520 --> 00:36:09,360 Speaker 1: a coil of wire creates the magnetic field when electricity 588 00:36:09,440 --> 00:36:13,280 Speaker 1: runs through it. This wire is coiled around a soft 589 00:36:13,400 --> 00:36:17,600 Speaker 1: magnetic material. Remember those are the kinds of magnetic materials 590 00:36:17,600 --> 00:36:20,680 Speaker 1: that are easy to influence. But then we'll go back 591 00:36:20,680 --> 00:36:24,359 Speaker 1: to their natural state shortly after the magnetic field they've 592 00:36:24,400 --> 00:36:29,120 Speaker 1: been exposed to has gone away. This creates what we 593 00:36:29,160 --> 00:36:33,120 Speaker 1: call a magnetic flux, and it concentrates at the tip 594 00:36:33,320 --> 00:36:37,440 Speaker 1: of the soft magnetic material that's the core of this coil. 595 00:36:37,960 --> 00:36:40,959 Speaker 1: A common design for early recording heads was a ring 596 00:36:41,480 --> 00:36:44,799 Speaker 1: that had a small gap cut into it, and then 597 00:36:44,840 --> 00:36:49,200 Speaker 1: you would wrap the wire around the inside of this ring, 598 00:36:49,480 --> 00:36:52,239 Speaker 1: like you know around the ring. So imagine just a 599 00:36:52,280 --> 00:36:55,120 Speaker 1: regular ring. You cut a little gap at one end. 600 00:36:55,440 --> 00:36:58,720 Speaker 1: On the other end, you've wrapped this this coil of wire, 601 00:36:58,760 --> 00:37:01,399 Speaker 1: and you run electricity through it. Turns the ring into 602 00:37:01,480 --> 00:37:05,200 Speaker 1: a magnet, but the gap creates a difference in this 603 00:37:05,280 --> 00:37:10,440 Speaker 1: magnetic field. The soft material, the soft magnetic material, conducts 604 00:37:10,480 --> 00:37:15,600 Speaker 1: magnetic flux easily and the gap doesn't. This causes the 605 00:37:15,640 --> 00:37:19,480 Speaker 1: magnetic flux to do something we call fringing. It fringes. 606 00:37:20,040 --> 00:37:23,120 Speaker 1: A fringe field is a bit tricky to explain, but 607 00:37:23,200 --> 00:37:26,360 Speaker 1: it's easier to understand if you imagine a horseshoe magnet. 608 00:37:27,120 --> 00:37:30,680 Speaker 1: So the two ends of the horseshoe are the two poles, 609 00:37:30,719 --> 00:37:33,200 Speaker 1: the north pole and the south pole. The fringe field 610 00:37:33,239 --> 00:37:37,080 Speaker 1: is the magnetic field that extends outside the space between 611 00:37:37,239 --> 00:37:40,960 Speaker 1: the two poles. That would be a fringe field. Now, 612 00:37:41,000 --> 00:37:43,120 Speaker 1: that fringe field is what the right head uses to 613 00:37:43,239 --> 00:37:47,600 Speaker 1: actually record information onto the magnetic medium. Now, with sound, 614 00:37:48,040 --> 00:37:51,200 Speaker 1: we're talking about an analog approach, meaning you'd find a 615 00:37:51,400 --> 00:37:56,080 Speaker 1: smooth variability in the medium. You would create that by 616 00:37:56,360 --> 00:38:00,239 Speaker 1: varying the magnetic flux in subtle ways. The record warding 617 00:38:00,280 --> 00:38:03,040 Speaker 1: head adjust the magnetic flux by varying the current running 618 00:38:03,080 --> 00:38:05,400 Speaker 1: through the head and the recording medium thus has a 619 00:38:05,520 --> 00:38:09,640 Speaker 1: variability in the magnetic flux recorded within the wire itself. 620 00:38:10,520 --> 00:38:13,840 Speaker 1: The wire represents a sort of copy of the flux. 621 00:38:14,480 --> 00:38:17,279 Speaker 1: If you were to run the wire back. So let's 622 00:38:17,280 --> 00:38:20,719 Speaker 1: say you've got the red head. The transducer acts as 623 00:38:20,719 --> 00:38:23,840 Speaker 1: a red head, and you run the wire next to 624 00:38:23,920 --> 00:38:29,360 Speaker 1: it uh sequentially, so you're just spinning one reel pulling 625 00:38:29,400 --> 00:38:32,440 Speaker 1: wire across so that this red head is very close 626 00:38:32,480 --> 00:38:36,240 Speaker 1: to it. That would create a varying magnetic field across 627 00:38:36,320 --> 00:38:39,640 Speaker 1: the gap in the red head, and that then would 628 00:38:39,680 --> 00:38:42,640 Speaker 1: create a varying magnetic field in the core of the 629 00:38:42,719 --> 00:38:45,480 Speaker 1: red head, which would induce a current to flow through 630 00:38:45,480 --> 00:38:48,319 Speaker 1: the coil of wire, which then could be sent to 631 00:38:48,320 --> 00:38:51,920 Speaker 1: an amplifier. The varying electric electrical signal goes to a 632 00:38:51,960 --> 00:38:54,719 Speaker 1: transducer such as speakers, and then it can play back 633 00:38:54,760 --> 00:38:58,840 Speaker 1: the sound. Now, those old wire recorders moved at a 634 00:38:58,840 --> 00:39:02,799 Speaker 1: pretty good clip. A post war wire recorders would play 635 00:39:02,840 --> 00:39:06,520 Speaker 1: back wire at about twenty four inches per second, so 636 00:39:06,640 --> 00:39:09,719 Speaker 1: two ft a wire per second. That's about sixty one 637 00:39:10,400 --> 00:39:13,200 Speaker 1: per second for you folks on the metric system, if 638 00:39:13,239 --> 00:39:15,600 Speaker 1: you wanted to record an hour's worth of audio, you 639 00:39:15,640 --> 00:39:19,600 Speaker 1: would need seven thousand, two hundred feet of wire or 640 00:39:19,600 --> 00:39:25,320 Speaker 1: about two thousand one of wire, and you could only 641 00:39:25,360 --> 00:39:29,480 Speaker 1: record along one direction of the wire. So if you 642 00:39:29,520 --> 00:39:31,520 Speaker 1: want to listen to it again. You don't have to 643 00:39:31,560 --> 00:39:34,879 Speaker 1: wind all the wire back up into a reel and 644 00:39:34,880 --> 00:39:38,680 Speaker 1: then play it out across a reed head all over again. 645 00:39:39,600 --> 00:39:42,480 Speaker 1: Most of these early ones were hand cranked too, so 646 00:39:43,520 --> 00:39:45,920 Speaker 1: you would get variability on the sound quality as it 647 00:39:45,960 --> 00:39:49,960 Speaker 1: was played back, plus when you were recording, so it 648 00:39:50,040 --> 00:39:53,840 Speaker 1: took a steady hand to create a decent recording and 649 00:39:53,760 --> 00:39:58,279 Speaker 1: a decent replication. And if you wanted to rerecord over it. 650 00:39:58,360 --> 00:40:01,320 Speaker 1: Let's say that you've you know, you recorded an hour 651 00:40:01,560 --> 00:40:04,800 Speaker 1: of someone catterwauling, and then you're like, well, that wasn't 652 00:40:04,800 --> 00:40:06,640 Speaker 1: really worth it. I would love to use this wire 653 00:40:06,719 --> 00:40:09,879 Speaker 1: to record something else. You would first have to run 654 00:40:10,000 --> 00:40:14,160 Speaker 1: that wire by a strong permanent magnet, and that would 655 00:40:14,200 --> 00:40:17,040 Speaker 1: effectively erase the stuff that was on it before, because 656 00:40:17,040 --> 00:40:21,040 Speaker 1: the strong permanent magnet would cause all those uh, those 657 00:40:21,239 --> 00:40:26,000 Speaker 1: those magnet magnetic domains inside the wire to realign to 658 00:40:26,120 --> 00:40:30,799 Speaker 1: the permanent magnets magnetic field. It essentially erases all the variability, 659 00:40:30,880 --> 00:40:34,440 Speaker 1: all the flux that was copied there before and turns 660 00:40:34,440 --> 00:40:39,080 Speaker 1: it back into a uniform medium which you then could 661 00:40:39,719 --> 00:40:43,839 Speaker 1: run through and record stuff on again the same thing. 662 00:40:43,840 --> 00:40:46,280 Speaker 1: By the way, it's true for lots of other magnetic 663 00:40:46,320 --> 00:40:50,319 Speaker 1: storage media. Now, eventually Poulson began to work with other 664 00:40:50,360 --> 00:40:53,680 Speaker 1: types of magnetic media, and a big breakthrough came with 665 00:40:53,840 --> 00:40:57,360 Speaker 1: the invention of plastic. I say the invention of I 666 00:40:57,400 --> 00:40:59,600 Speaker 1: really mean the mass production of plastic has been around 667 00:40:59,600 --> 00:41:01,960 Speaker 1: for a pretty a long time, but I'm talking about 668 00:41:01,960 --> 00:41:04,480 Speaker 1: when we really started producing it on a mass scale. 669 00:41:05,640 --> 00:41:08,560 Speaker 1: So you can use plastic film coated with a ferro 670 00:41:08,640 --> 00:41:12,520 Speaker 1: magnetic powder. This is how cassette tapes, VHS tapes, even 671 00:41:12,520 --> 00:41:15,920 Speaker 1: floppy disks work. You can make a cheap recording medium 672 00:41:15,960 --> 00:41:18,800 Speaker 1: this way. Uh, the invention of the cassette tape itself 673 00:41:18,880 --> 00:41:21,360 Speaker 1: was another big jump because engineers figured out how you 674 00:41:21,400 --> 00:41:24,319 Speaker 1: could double the amount of material you could record on 675 00:41:24,360 --> 00:41:27,200 Speaker 1: a tape if you just recorded on half of it 676 00:41:27,280 --> 00:41:30,160 Speaker 1: at a time. Now, this is a little tricky to 677 00:41:30,239 --> 00:41:33,040 Speaker 1: explain without the use of visual aids, but I'll try 678 00:41:33,120 --> 00:41:36,160 Speaker 1: and give it a shot. So imagine that you've got 679 00:41:36,200 --> 00:41:39,600 Speaker 1: a length of flat ribbon in front of you. You 680 00:41:39,680 --> 00:41:42,439 Speaker 1: might think of cassette that cassette recorders are actually putting 681 00:41:42,440 --> 00:41:45,399 Speaker 1: information on both sides of the ribbon, but that's not 682 00:41:45,560 --> 00:41:48,719 Speaker 1: what is happening. All the information for side A and 683 00:41:48,840 --> 00:41:52,640 Speaker 1: side b are on one side of that ribbon, but 684 00:41:52,719 --> 00:41:56,080 Speaker 1: they are one hundred and eighty degrees opposite each other, 685 00:41:56,239 --> 00:42:00,080 Speaker 1: side by side. So you lay out the ribbons so 686 00:42:00,120 --> 00:42:03,520 Speaker 1: it's horizontal in relation to you. You're looking at a 687 00:42:03,560 --> 00:42:07,680 Speaker 1: horizontal strip of ribbon. Imagine a line going down the 688 00:42:07,719 --> 00:42:11,600 Speaker 1: middle of that ribbon horizontally. The top half of the 689 00:42:11,680 --> 00:42:15,920 Speaker 1: ribbon is one side of the cassette and the bottom 690 00:42:16,040 --> 00:42:20,080 Speaker 1: half is the other side of the cassette. So when 691 00:42:20,120 --> 00:42:23,800 Speaker 1: you put a cassette into a cassette player, the reed 692 00:42:23,880 --> 00:42:27,800 Speaker 1: head is positioned over just one half of that tape 693 00:42:28,200 --> 00:42:30,840 Speaker 1: and it reads what's off of that. When you flip 694 00:42:30,880 --> 00:42:35,399 Speaker 1: the cassette over, then the side of the tape that's 695 00:42:35,480 --> 00:42:39,920 Speaker 1: running across the reed head is the opposite of of that. 696 00:42:40,000 --> 00:42:42,080 Speaker 1: You know, it's the bottom of the ribbon as opposed 697 00:42:42,080 --> 00:42:43,520 Speaker 1: to the top of the ribbon, and that's all you're 698 00:42:43,520 --> 00:42:47,239 Speaker 1: able to listen to side b uh. So that's kind 699 00:42:47,239 --> 00:42:51,840 Speaker 1: of cool, I thought. Now, next, I'm gonna talk specifically 700 00:42:51,880 --> 00:42:55,120 Speaker 1: about using magnetism to store information for a digital computer, 701 00:42:55,800 --> 00:42:57,400 Speaker 1: which is a little bit different from what I've been 702 00:42:57,480 --> 00:43:00,799 Speaker 1: chatting about so far. But first, let's take another quick 703 00:43:00,840 --> 00:43:10,880 Speaker 1: break to thank our sponsor. All right, So in the 704 00:43:10,960 --> 00:43:13,720 Speaker 1: last section I talked about how magnetic recording can create 705 00:43:13,719 --> 00:43:17,879 Speaker 1: a variable magnetic flux for analog playback. But what about computers. 706 00:43:18,160 --> 00:43:23,680 Speaker 1: Computers rely on binary language, not analog. It's not a variability, 707 00:43:23,800 --> 00:43:27,160 Speaker 1: it's a collection of zeros and ones. You have to 708 00:43:27,200 --> 00:43:30,800 Speaker 1: describe computer information in this format as either a zero 709 00:43:30,960 --> 00:43:33,920 Speaker 1: or one. Ultimately, when you get down to it, every 710 00:43:33,960 --> 00:43:37,239 Speaker 1: computer language out there, once you get down to the 711 00:43:37,400 --> 00:43:41,160 Speaker 1: very basics, ends up being translated into zeros and ones 712 00:43:41,480 --> 00:43:44,239 Speaker 1: because computers just don't deal with these variable fields. So 713 00:43:44,480 --> 00:43:48,479 Speaker 1: how do you get it to do that? So, while 714 00:43:48,480 --> 00:43:51,879 Speaker 1: the format is more or less obsolete, I'm gonna talk 715 00:43:51,920 --> 00:43:55,360 Speaker 1: about floppy disks for a bit, and that's because there 716 00:43:55,360 --> 00:43:58,200 Speaker 1: are a lot of parallels between floppy disks and cassette tapes, 717 00:43:58,239 --> 00:44:01,280 Speaker 1: which I talked about in the last section. Floppy disks, 718 00:44:01,280 --> 00:44:04,520 Speaker 1: by the way, used to come in several sizes. When 719 00:44:04,560 --> 00:44:07,080 Speaker 1: I first started using computers, the standard size in the 720 00:44:07,160 --> 00:44:10,000 Speaker 1: US was the five and a quarter inch disc. There 721 00:44:10,000 --> 00:44:12,919 Speaker 1: were larger discs that came before that, but the first 722 00:44:13,000 --> 00:44:14,680 Speaker 1: ones I ever used were five and a quarter inch. 723 00:44:15,360 --> 00:44:17,360 Speaker 1: A lot of people thought they were called floppy disks. 724 00:44:17,400 --> 00:44:21,080 Speaker 1: Because the outer sheath of the disc itself was flexible. 725 00:44:21,640 --> 00:44:23,400 Speaker 1: Some people even thought you could fold them up and 726 00:44:23,400 --> 00:44:26,120 Speaker 1: put them in your pocket, which technically I guess you 727 00:44:26,160 --> 00:44:28,279 Speaker 1: could do, but you wouldn't be able to use them 728 00:44:28,360 --> 00:44:31,320 Speaker 1: later because you mangle the disk inside and it would 729 00:44:31,320 --> 00:44:35,759 Speaker 1: no longer spend properly inside a computer. So don't do that. 730 00:44:36,440 --> 00:44:38,680 Speaker 1: Later on came the three and a half inch discs, 731 00:44:38,719 --> 00:44:41,600 Speaker 1: and these had a hard plastic casing, but they were 732 00:44:41,600 --> 00:44:45,800 Speaker 1: still floppy disks because the disk inside, the actual medium 733 00:44:45,880 --> 00:44:50,360 Speaker 1: upon which information was stored, was still this flexible material. 734 00:44:50,600 --> 00:44:53,040 Speaker 1: A lot of folks thought that these three and a 735 00:44:53,040 --> 00:44:56,640 Speaker 1: half inch discs were actually hard disks. They said, you know, 736 00:44:56,640 --> 00:44:58,480 Speaker 1: the floppy disks were the five and a quarter three 737 00:44:58,520 --> 00:45:01,439 Speaker 1: and a half Because the plastic it is sturdy, that's 738 00:45:01,480 --> 00:45:04,800 Speaker 1: a hard disk. No, that's not a hard disk. But anyway, 739 00:45:04,800 --> 00:45:07,360 Speaker 1: that's all ancient history, and you guys probably don't even 740 00:45:07,960 --> 00:45:11,080 Speaker 1: understand what I'm talking about. Get off my lawn, all right. 741 00:45:11,120 --> 00:45:14,560 Speaker 1: Inside the outer covering of these discs was the actual 742 00:45:14,680 --> 00:45:19,480 Speaker 1: disc itself. We call the floppy disks that, but they're 743 00:45:19,520 --> 00:45:22,839 Speaker 1: not disc shaped. If you were to show someone a 744 00:45:22,840 --> 00:45:26,600 Speaker 1: floppy disk and they had absolutely no context for it. 745 00:45:26,600 --> 00:45:29,040 Speaker 1: They knew what the word disc meant. They take one 746 00:45:29,040 --> 00:45:30,640 Speaker 1: look at and say, why the heck do you call 747 00:45:30,680 --> 00:45:34,279 Speaker 1: it a disc. It's because on the inside there is 748 00:45:34,320 --> 00:45:39,000 Speaker 1: a disc of material, and it is essentially a plastic 749 00:45:39,040 --> 00:45:43,480 Speaker 1: base that's coated with ferro magnetic materials. And the advantage 750 00:45:43,520 --> 00:45:46,160 Speaker 1: of this is that if you apply a magnetic field 751 00:45:46,200 --> 00:45:49,480 Speaker 1: to it, it would record that information permanently, or at 752 00:45:49,520 --> 00:45:52,000 Speaker 1: least until you erased it and wrote over it, or 753 00:45:52,080 --> 00:45:55,319 Speaker 1: if you encountered a really strong magnetic field, and it 754 00:45:55,440 --> 00:45:58,160 Speaker 1: was a really fast way to record a lot of information. 755 00:45:59,000 --> 00:46:04,279 Speaker 1: So disks are organized into concentric rings. You can kind 756 00:46:04,280 --> 00:46:08,160 Speaker 1: of think of an old vinyl album in the same 757 00:46:08,200 --> 00:46:11,960 Speaker 1: way how the grooves slowly move inward on the um 758 00:46:12,000 --> 00:46:15,880 Speaker 1: on the disc, But in this case their actual concentric 759 00:46:16,000 --> 00:46:20,120 Speaker 1: rings of information, not not just one line that slowly, 760 00:46:21,280 --> 00:46:24,680 Speaker 1: you know, swirls inward towards the center. So when a 761 00:46:24,719 --> 00:46:28,920 Speaker 1: computer is reading information back, it can it can reference 762 00:46:28,920 --> 00:46:31,000 Speaker 1: some information at the at the front of the disc 763 00:46:31,080 --> 00:46:34,680 Speaker 1: and learn exactly where a file is located, and it 764 00:46:34,719 --> 00:46:37,319 Speaker 1: can then position the read right head directly over the 765 00:46:37,360 --> 00:46:39,880 Speaker 1: appropriate part of the disc, rather than having to go 766 00:46:39,960 --> 00:46:43,360 Speaker 1: through the whole thing sequentially. So with the cassette tape, 767 00:46:43,600 --> 00:46:46,719 Speaker 1: if you want to listen to a specific song, you 768 00:46:46,800 --> 00:46:49,320 Speaker 1: have to wait. You mean, you can use fast forward 769 00:46:49,360 --> 00:46:52,480 Speaker 1: to speed things up, but you can't jump straight to 770 00:46:52,600 --> 00:46:56,120 Speaker 1: the track you want to hear, unlike you could with say, 771 00:46:56,440 --> 00:47:00,600 Speaker 1: compact disc. Well, in this way, a flop disc is 772 00:47:00,680 --> 00:47:03,960 Speaker 1: more like a compact disc in that a computer can 773 00:47:04,040 --> 00:47:09,400 Speaker 1: understand exactly where the file is stored within those concentric 774 00:47:09,520 --> 00:47:13,040 Speaker 1: rings and go straight there. In other ways, it is 775 00:47:13,200 --> 00:47:16,880 Speaker 1: very different from a compact disc, but in that specific 776 00:47:16,960 --> 00:47:21,040 Speaker 1: way it is similar. Now in other words, it's kind 777 00:47:21,040 --> 00:47:23,600 Speaker 1: of like lifting a record player's needle off of one 778 00:47:23,640 --> 00:47:26,960 Speaker 1: groove and skipping ahead to a specific song on an album, 779 00:47:27,040 --> 00:47:30,040 Speaker 1: lowering the needle and then playing it, and thank goodness 780 00:47:30,880 --> 00:47:33,600 Speaker 1: record players are coming back. So that you guys know 781 00:47:33,640 --> 00:47:36,480 Speaker 1: what I'm talking about when I say these things. This, 782 00:47:36,600 --> 00:47:40,360 Speaker 1: by the way, is a type of direct access storage, 783 00:47:40,840 --> 00:47:44,400 Speaker 1: meaning the computer can get direct access to that information 784 00:47:44,680 --> 00:47:47,400 Speaker 1: in a very short amount of time. When writing to 785 00:47:47,440 --> 00:47:50,800 Speaker 1: a disc, first the drive will use in a race coil, 786 00:47:51,680 --> 00:47:55,320 Speaker 1: and this essentially just clears a section of the storage 787 00:47:55,320 --> 00:47:58,960 Speaker 1: medium for writing. So it's it's kind of like exposing 788 00:47:59,000 --> 00:48:02,160 Speaker 1: that steel wired to a permanent magnet. It's that same principle. 789 00:48:02,239 --> 00:48:06,800 Speaker 1: You want a clean slate to write upon, and typically 790 00:48:06,840 --> 00:48:09,800 Speaker 1: this clean slate is a bit wider than the actual 791 00:48:10,080 --> 00:48:13,520 Speaker 1: right section you're going to be working on. You want 792 00:48:13,760 --> 00:48:17,320 Speaker 1: the area that is a clean slate to be larger 793 00:48:17,760 --> 00:48:19,960 Speaker 1: so that you have a buffer zone at either end, 794 00:48:20,200 --> 00:48:23,600 Speaker 1: and that way it keeps adjacent files from interfering with 795 00:48:23,640 --> 00:48:26,759 Speaker 1: each other. If you were writing information to that part 796 00:48:26,760 --> 00:48:29,719 Speaker 1: of the disc and it went over that area, you 797 00:48:29,719 --> 00:48:32,600 Speaker 1: would start writing on top of some other file and 798 00:48:32,640 --> 00:48:38,279 Speaker 1: then the storage wouldn't work at all. So the right 799 00:48:38,360 --> 00:48:41,240 Speaker 1: head puts data on the disk drive by applying one 800 00:48:41,440 --> 00:48:47,080 Speaker 1: of two magnetic fields to the tape. It either aligns 801 00:48:47,120 --> 00:48:52,399 Speaker 1: the magnetic material as north south or south north. That 802 00:48:52,440 --> 00:48:55,560 Speaker 1: means it's either a zero or a one. Like so 803 00:48:55,640 --> 00:49:00,120 Speaker 1: imagine that north south magnetization represents a zero and ou 804 00:49:00,360 --> 00:49:03,400 Speaker 1: north represents a one. The right head can then go 805 00:49:03,560 --> 00:49:08,680 Speaker 1: through this disc very very quickly, applying these magnetic fields 806 00:49:08,680 --> 00:49:11,640 Speaker 1: one after the other, maybe several North south in a 807 00:49:11,719 --> 00:49:15,920 Speaker 1: row followed by a south north or whatever, and it 808 00:49:16,040 --> 00:49:19,359 Speaker 1: is recorded on the disc itself, and when you read 809 00:49:19,400 --> 00:49:23,320 Speaker 1: it back then you know by looking at the code, 810 00:49:23,520 --> 00:49:26,200 Speaker 1: Oh these are you know, three zeros in a row 811 00:49:26,239 --> 00:49:30,000 Speaker 1: and then a one. It replicates those zeros and ones 812 00:49:30,080 --> 00:49:32,600 Speaker 1: that were recorded to the storage medium. This, in a 813 00:49:32,600 --> 00:49:35,680 Speaker 1: way is much more simple than a variable magnetic flux 814 00:49:35,719 --> 00:49:38,960 Speaker 1: because you only have to have two magnetic states. You 815 00:49:39,040 --> 00:49:41,920 Speaker 1: just have to have something that represents a zero and 816 00:49:42,040 --> 00:49:46,440 Speaker 1: something that represents a one. No other values are accepted, 817 00:49:47,040 --> 00:49:49,840 Speaker 1: so you just have to have those two basic modes, 818 00:49:51,120 --> 00:49:54,760 Speaker 1: and the same basic principles apply to other computer magnetic storage. 819 00:49:55,120 --> 00:49:57,759 Speaker 1: Magnetic hard drives use a very similar approach to the 820 00:49:57,760 --> 00:50:01,280 Speaker 1: ones I described for floppy drives. And you probably heard 821 00:50:01,320 --> 00:50:03,880 Speaker 1: that it's a bad idea to expose computers to strong 822 00:50:03,960 --> 00:50:06,680 Speaker 1: magnetic fields, and the big reason for this is that 823 00:50:06,800 --> 00:50:10,920 Speaker 1: magnetic storage. If you bring a strong permanent magnet close 824 00:50:11,000 --> 00:50:14,359 Speaker 1: enough to magnetic storage media, you'll erase the data that's 825 00:50:14,360 --> 00:50:17,520 Speaker 1: stored there. That includes data that's on a hard drive 826 00:50:17,719 --> 00:50:21,680 Speaker 1: if it's a magnetic drive, right, if it's a solid 827 00:50:21,680 --> 00:50:24,719 Speaker 1: state drive, it's a different story. Or if you were 828 00:50:24,760 --> 00:50:29,200 Speaker 1: to take a strong permanent magnet and threatening someone by 829 00:50:29,320 --> 00:50:32,120 Speaker 1: by holding a compact disc with all their photos on it, 830 00:50:32,160 --> 00:50:34,200 Speaker 1: and you're saying if you come any closer, I'm going 831 00:50:34,239 --> 00:50:36,640 Speaker 1: to ruin your pictures by putting this magnet up to 832 00:50:36,680 --> 00:50:40,560 Speaker 1: the c D. It won't work because the information stored 833 00:50:40,560 --> 00:50:44,640 Speaker 1: on the CD is an optical format, not magnetic, and 834 00:50:44,680 --> 00:50:48,759 Speaker 1: magnets aren't going to affect it at all, so you 835 00:50:48,760 --> 00:50:50,799 Speaker 1: shouldn't be doing that anyway. It's kind of a jerk move, 836 00:50:51,480 --> 00:50:54,120 Speaker 1: but it wouldn't work, is what I'm getting at. So 837 00:50:54,160 --> 00:50:57,800 Speaker 1: in future episodes I plan on exploring stuff like optical 838 00:50:57,880 --> 00:51:01,160 Speaker 1: storage and how that works, how is it similar to 839 00:51:01,400 --> 00:51:05,600 Speaker 1: and different from magnetic storage? And also solid state drives, 840 00:51:06,040 --> 00:51:08,880 Speaker 1: which are you know, pretty much the standard and a 841 00:51:08,920 --> 00:51:12,839 Speaker 1: lot of different computers these days, which have incredible advantages 842 00:51:13,040 --> 00:51:15,480 Speaker 1: in how quiet they are and how fast they are, 843 00:51:15,880 --> 00:51:17,919 Speaker 1: but they tend to be a lot more expensive than 844 00:51:17,960 --> 00:51:21,520 Speaker 1: your old style magnetic drives. I'll talk about those in 845 00:51:21,600 --> 00:51:24,200 Speaker 1: future episodes too, And if you guys have any questions 846 00:51:24,200 --> 00:51:26,600 Speaker 1: about the stuff I mentioned here, feel free to send 847 00:51:26,640 --> 00:51:30,480 Speaker 1: me an email. My address is tech stuff at how 848 00:51:30,560 --> 00:51:33,319 Speaker 1: stuff Works dot com, or you can always drop me 849 00:51:33,360 --> 00:51:36,520 Speaker 1: a line on Facebook or Twitter. The handle of both 850 00:51:36,520 --> 00:51:40,200 Speaker 1: of those is text stuff H s W. And I 851 00:51:40,239 --> 00:51:48,080 Speaker 1: will talk to you again really see for more on 852 00:51:48,160 --> 00:51:50,920 Speaker 1: this and thousands of other topics. Is it how stuff works? 853 00:51:50,920 --> 00:52:00,239 Speaker 1: Dot com two