WEBVTT - Janet Jackson and Nikola Tesla 0:00:04.400 --> 0:00:07.800 Welcome to tech Stuff, a production from I Heart Radio. 0:00:11.800 --> 0:00:14.200 Hey there, and welcome to tech Stuff. I'm your host 0:00:14.280 --> 0:00:17.000 Jonathan Strickland. I'm an executive producer with iHeart Radio and 0:00:17.040 --> 0:00:20.119 How the tech are you Now. In a recent tech 0:00:20.200 --> 0:00:24.079 News episode, I talked about how a Microsoft engineer named 0:00:24.239 --> 0:00:28.720 Raymond Chen revealed that the music video for Janet Jackson's 0:00:29.840 --> 0:00:34.640 hit Rhythm Nation was at one time the crasher of laptops, 0:00:35.000 --> 0:00:38.559 or at least of certain laptops. Some folks discovered that 0:00:38.720 --> 0:00:42.320 if they played this video on their laptop computer, or 0:00:42.520 --> 0:00:45.320 if their laptop computer was close to something else that 0:00:45.400 --> 0:00:50.680 was playing this music video, the computer would spontaneously crash. Now, 0:00:50.800 --> 0:00:54.560 to be clear, these computers were not nasty, as miss 0:00:54.720 --> 0:00:58.880 Jackson might say. They were not music critics. It turns 0:00:58.920 --> 0:01:03.800 out that a sound played in that music video matched 0:01:03.880 --> 0:01:07.759 the resonant frequency of the hard disk drives in these laptops, 0:01:08.120 --> 0:01:11.119 though it took some time to suss that out. Chen 0:01:11.319 --> 0:01:14.440 said that these were hard drives that we're spending at 0:01:14.440 --> 0:01:18.200 five thousand four rpm. That's revolutions per minute, so going 0:01:18.200 --> 0:01:21.759 around five thousand, four hundred times every minute. That's actually 0:01:22.160 --> 0:01:24.560 on the lower end of what we typically see with 0:01:24.680 --> 0:01:27.080 hard disk drives, they can top out at more than 0:01:27.160 --> 0:01:30.360 twice as fast as that. But it's not bad. I mean, 0:01:30.400 --> 0:01:33.520 you can still go out and buy a hard disk 0:01:33.600 --> 0:01:37.000 drive today that's at five thousand PM. People typically like 0:01:37.600 --> 0:01:39.760 faster ones. It means that you can read and write 0:01:39.840 --> 0:01:45.080 information to such a hard drive faster. Anyway, the sound 0:01:45.120 --> 0:01:49.680 from the music video was causing the hard drives to vibrate. 0:01:50.200 --> 0:01:53.960 The platters inside would vibrate, and ultimately this would prompt 0:01:54.000 --> 0:01:57.360 the computers to crash. So today I thought i'd talk 0:01:57.520 --> 0:02:00.160 a little bit about hard drives, a bit of out 0:02:00.200 --> 0:02:03.480 resonant frequencies, how a sound could cause a hard drive 0:02:03.520 --> 0:02:08.000 to actually crash, and maybe talk about some myths surrounding resonance, 0:02:08.000 --> 0:02:12.680 including one that I kind of perpetuated last week. So 0:02:13.040 --> 0:02:18.079 I gotta hold myself up to a correction here anyway. 0:02:18.120 --> 0:02:20.920 First up, if you were to take a hard drive apart, 0:02:21.400 --> 0:02:23.880 don't do that, by the way, You're more than likely 0:02:23.880 --> 0:02:27.079 going to destroy it. But you would see that inside 0:02:27.120 --> 0:02:31.399 the hard disk drive you have a spindle, and on 0:02:31.440 --> 0:02:34.600 the spindle would be at least one disc or platter. 0:02:34.919 --> 0:02:37.840 More likely it would actually be more than one, perhaps 0:02:37.840 --> 0:02:41.040 a stack of them, and each platter would be separated 0:02:41.200 --> 0:02:45.119 from its neighbors by a small gap, and the platters 0:02:45.160 --> 0:02:48.280 are kind of similar to a compact disk in some ways, 0:02:48.360 --> 0:02:52.680 but compact discs store information that's read and written through 0:02:53.040 --> 0:02:57.960 an optical drive. So with light laser specifically, hard disks 0:02:58.240 --> 0:03:03.800 store information magneticle, not through optics. Now, this platter or 0:03:03.840 --> 0:03:08.480 these platters are what spin inside a hard disk drive coding. 0:03:08.520 --> 0:03:12.359 The platter is a thin layer of magnetic grains, so 0:03:13.560 --> 0:03:18.720 using an electro magnetic head, the computer can write data 0:03:18.960 --> 0:03:24.000 to the platter by realigning these magnetic grains so that 0:03:24.040 --> 0:03:28.320 they point in a specific direction, essentially pointing magnetic north 0:03:28.400 --> 0:03:31.880 or pointing magnetic south, and thus they can represent zeros 0:03:32.000 --> 0:03:36.000 and ones. When the platter spins beneath the head or 0:03:36.240 --> 0:03:40.400 above the head, depending on how this goes, and the 0:03:40.440 --> 0:03:44.160 head is in passive mode, there's a little detector essentially 0:03:44.840 --> 0:03:48.080 on the head that can pick up the magnetic fluctuations 0:03:48.520 --> 0:03:53.240 from these aligned regions that are passing near it as 0:03:53.280 --> 0:03:56.800 the disc is spinning, so it's being read now. The 0:03:56.840 --> 0:04:00.600 head in this case can look a bit like tweezers 0:04:00.760 --> 0:04:04.000 in a sense. There's typically a pair of arms, one 0:04:04.080 --> 0:04:07.040 that goes over the top of the platter one that's beneath. 0:04:07.280 --> 0:04:10.600 They are not making contact with the platter. In fact, 0:04:11.000 --> 0:04:13.640 if they were to touch the platter, that would damage 0:04:13.720 --> 0:04:16.440 the hard drive. You gotta keep in mind, these platters 0:04:16.440 --> 0:04:22.440 are spinning super fast, so these electro magnets are separated 0:04:22.680 --> 0:04:25.720 from the platters. They're not actually touching, they're they're hovering 0:04:25.760 --> 0:04:29.480 above and below um. So really like every head is 0:04:29.560 --> 0:04:32.240 usually a pair of red Wright heads. There's one on top, 0:04:32.320 --> 0:04:35.320 one beneath each platter that allows the computer to store 0:04:35.360 --> 0:04:38.559 information on either side of platters. And as I said, 0:04:38.720 --> 0:04:41.359 your typical hard drive often has several of these platters 0:04:41.480 --> 0:04:44.240 arranged in a stack, separated from each of them by 0:04:44.279 --> 0:04:47.560 a small gap, and each platter has its own read 0:04:47.680 --> 0:04:51.320 right head. But that is the super basic way that 0:04:51.440 --> 0:04:54.680 hard drives work. I'm not even getting into things like 0:04:55.200 --> 0:04:58.320 actually how you store a file on these platters, because 0:04:58.320 --> 0:05:00.640 it's not as simple as like the roove on a 0:05:00.839 --> 0:05:03.840 on a vinyl album representing a song. It's not like that. 0:05:04.600 --> 0:05:07.560 But the reason for this rapid rotational speed is that 0:05:07.640 --> 0:05:10.200 you do want to be able to read and write 0:05:10.240 --> 0:05:14.760 information from this hard disk drive quickly. And you know, 0:05:15.000 --> 0:05:18.960 if it didn't spin at these fast rates, it would 0:05:18.960 --> 0:05:21.880 take forever, which is hyperbolie. It would take a really 0:05:21.880 --> 0:05:24.840 long time for your computer to retrieve stored information from 0:05:24.880 --> 0:05:27.919 the hard disk drive. And it blows my mind that 0:05:28.000 --> 0:05:32.359 you can have platters spending times per minute or faster 0:05:32.920 --> 0:05:37.040 and read or write information to those platters, storing gigabytes 0:05:37.080 --> 0:05:41.000 of data in the process. Technology is really kind of 0:05:41.120 --> 0:05:46.800 like magic, except you know it works. Now. If you 0:05:46.839 --> 0:05:50.120 have a mechanical device like this, clearly everything needs to 0:05:50.160 --> 0:05:53.600 be improper alignment or else you're going to have problems. 0:05:54.160 --> 0:05:57.080 Jostling a hard disk drive can potentially knock a disc 0:05:57.160 --> 0:06:00.279 off kilter, which would mean that once the spin doll 0:06:00.600 --> 0:06:03.479 that the disks start on starts to spin, you're gonna 0:06:03.520 --> 0:06:07.520 have some damage, possibly catastrophic damage. The platters need to 0:06:07.560 --> 0:06:12.160 maintain both horizontal and vertical alignment, and honestly, knowing how 0:06:12.200 --> 0:06:14.880 delicate a hard disk drive can be, I'm actually amazed 0:06:14.920 --> 0:06:17.599 that my first ever MP three players survived for so 0:06:17.680 --> 0:06:20.800 many years. I had a creative Zen device which had 0:06:20.800 --> 0:06:24.200 a spinning hard disk drive inside of it, which is 0:06:24.240 --> 0:06:27.080 a very tiny little hard drive, and I say I'm 0:06:27.120 --> 0:06:29.320 amazed that survived because I know that thing took a 0:06:29.360 --> 0:06:32.080 tumble more than once, and the impact could have been 0:06:32.200 --> 0:06:34.680 enough to damage the hard drive, but I guess I 0:06:34.720 --> 0:06:38.719 had more luck than brains anyway. According to a data 0:06:38.720 --> 0:06:44.200 recovery firm called drive Savers, of hard disk drive failures 0:06:44.200 --> 0:06:48.000 are the result of damage recording surfaces, typically created as 0:06:48.040 --> 0:06:51.479 the result of a physical shock. Other potential causes for 0:06:51.520 --> 0:06:56.440 failure include things like circuit board problems uh stiction, which 0:06:56.520 --> 0:07:00.560 is the combination of friction and sticking, where if you 0:07:00.600 --> 0:07:02.400 haven't used a hard des drive for a long time, 0:07:02.480 --> 0:07:05.640 sometimes there can be this kind of friction sticking issue 0:07:05.880 --> 0:07:11.240 that impedes the disks from spinning. And also drive motor failure, 0:07:11.280 --> 0:07:13.840 which makes up like less than a percent of all 0:07:13.920 --> 0:07:17.720 the hard disk drive failures. So usually the motor doesn't 0:07:17.840 --> 0:07:20.480 isn't the problem. By the time the motor has given out, 0:07:20.520 --> 0:07:23.640 something else has already failed in that hard disk. Now, 0:07:24.120 --> 0:07:26.320 if something were to cause the hard drive to stop 0:07:26.360 --> 0:07:28.640 spinning while it's in operation, you get a hard disk 0:07:28.680 --> 0:07:32.000 drive failure in that prompts a full crash of the computer. 0:07:32.440 --> 0:07:36.240 And this brings us to Janet or miss Jackson. If 0:07:36.280 --> 0:07:39.080 I'm nasty, and it turns out that the song Rhythm 0:07:39.240 --> 0:07:43.240 Nation has within it a frequency that resonates with a 0:07:43.280 --> 0:07:47.680 certain popular model of hard disk drives from many years ago. 0:07:47.800 --> 0:07:50.680 So this isn't really about current tech. We're actually talking 0:07:50.720 --> 0:07:54.600 about machines that were sold around the year two thousand five. 0:07:55.160 --> 0:07:58.760 So really kind of amazing that this even became a problem, 0:07:58.840 --> 0:08:03.440 right because Rhythm Nation came out in nine, this particular 0:08:04.240 --> 0:08:08.920 uh laptop that was prone to this kind of stuff, 0:08:09.000 --> 0:08:11.840 or these laptops, I should say, because they all had 0:08:11.920 --> 0:08:14.400 this hard drive in common. It wasn't the laptops fault. 0:08:14.800 --> 0:08:19.200 Those were sold around two thousand five, and specifically, the 0:08:19.200 --> 0:08:21.840 the sound frequency from the music video would resonate with 0:08:21.880 --> 0:08:25.240 the natural resonant frequency produced by the hard drive when 0:08:25.280 --> 0:08:28.560 the platter is spinning. So let's talk about frequency and 0:08:28.720 --> 0:08:33.800 sound and resonance for a bit. With waves. Frequency refers 0:08:33.840 --> 0:08:36.840 to the number of waves that pass a fixed point 0:08:37.240 --> 0:08:39.800 within a given amount of time, and we use the 0:08:39.880 --> 0:08:44.319 metric hurts to measure frequencies. So one hurts is equal 0:08:44.360 --> 0:08:48.319 to one wave passing a fixed point in one second. 0:08:48.880 --> 0:08:52.240 Two hurts would mean two waves would pass that point 0:08:52.640 --> 0:08:56.240 in one second. Now, notice I didn't say sound waves 0:08:56.280 --> 0:08:59.680 here because Hurts can refer to any kind of wave 0:08:59.800 --> 0:09:03.760 or oscillation, so we can use frequency to talk about 0:09:03.760 --> 0:09:07.520 stuff like light or sound or all sorts of other things. 0:09:07.559 --> 0:09:10.559 But in this episode we're mostly concerned with sound. So 0:09:11.520 --> 0:09:14.720 if you were to play the middle C on a piano, 0:09:15.080 --> 0:09:19.120 and assuming that piano had been tuned according to VERD tuning, 0:09:19.360 --> 0:09:23.480 which is not standard uh, the note would produce a 0:09:23.480 --> 0:09:27.680 frequency of two hundred fifty six hurts. So that means 0:09:27.760 --> 0:09:31.480 the sound wave travels at two hundred fifty six waves 0:09:31.880 --> 0:09:36.160 past a given fixed point per second. Now, sound waves 0:09:36.320 --> 0:09:40.800 are really vibrations, right. Physical vibrations is a physical phenomenon. 0:09:41.840 --> 0:09:44.920 It is why there's no sound in space, because you 0:09:45.000 --> 0:09:51.320 don't have stuff close enough to transmit vibration from one 0:09:51.400 --> 0:09:54.800 thing to another, and you have to have stuff close 0:09:54.880 --> 0:09:58.440 enough to vibrate and affect other things in order for 0:09:58.480 --> 0:10:02.040 that to propagate for it to travel. Most of the 0:10:02.080 --> 0:10:06.520 stuff we hear is traveling through the air, So in 0:10:06.559 --> 0:10:09.880 this case, the vibrations we're talking about are typically these 0:10:09.960 --> 0:10:14.080 little fluctuations in air pressure. You can kind of imagine 0:10:14.280 --> 0:10:18.000 that these changes in air pressure are effectively pushing against 0:10:18.080 --> 0:10:22.280 and pulling on your ear drum. Just slightly, which then 0:10:22.320 --> 0:10:27.319 transmits those vibrations to our inner ear. Our brains ultimately 0:10:27.360 --> 0:10:31.600 interpret this signal as sound, and the frequency at which 0:10:31.600 --> 0:10:34.960 the air fluctuations affect our ear drums determines what pitch 0:10:35.120 --> 0:10:40.680 we hear. So slower frequencies produce lower pitches. Faster frequencies 0:10:40.960 --> 0:10:47.160 produce faster pitches. Two fifty six fluctuations like full fluctuations 0:10:47.160 --> 0:10:53.640 per second produces middle C. Now, let's talk about resonant frequencies. 0:10:54.400 --> 0:10:57.800 Systems have a frequency that they tend to oscillate at. 0:10:58.120 --> 0:11:01.400 The reason middle C sounds like middle C is that 0:11:01.440 --> 0:11:03.880 there is a string in that piano that's at the 0:11:04.000 --> 0:11:07.400 right length and it's at the right tension to produce 0:11:07.960 --> 0:11:11.679 that frequency. When that string is struck by a hammer, 0:11:11.920 --> 0:11:13.800 when you push down on the key, a hammer strikes 0:11:13.840 --> 0:11:17.760 the string and it vibrates at this frequency, and thus 0:11:17.800 --> 0:11:21.360 we hear that middle C. Similarly, if you take a 0:11:21.400 --> 0:11:24.840 wine glass and you tap the wine glass, you will 0:11:24.920 --> 0:11:28.640 hear it ring out a tone. That tone is the 0:11:28.760 --> 0:11:32.560 resonant frequency, the natural frequency for that glass. It's the 0:11:32.559 --> 0:11:36.880 frequency at which it tends to oscillate naturally when struck. Now, 0:11:37.200 --> 0:11:41.200 if you were to produce that same tone near the glass, 0:11:41.520 --> 0:11:44.600 you would cause the glass to vibrate. You would induce 0:11:44.760 --> 0:11:48.240 vibration in the glass. If you produce the tone with 0:11:48.400 --> 0:11:52.920 enough volume or amplitude, if we're talking about waves, that 0:11:53.080 --> 0:11:56.280 vibration can start to deform the glass enough to cause 0:11:56.320 --> 0:11:59.439 the wine glass to shatter. And you've probably seen examples 0:11:59.480 --> 0:12:01.520 of this, you know. The classic one is you have 0:12:01.559 --> 0:12:05.240 an opera singer singing a clear note and holding a 0:12:05.280 --> 0:12:09.200 wine glass and the glass inevitably breaks apart. That is 0:12:09.240 --> 0:12:11.680 possible if you have someone with the lung power and 0:12:11.720 --> 0:12:15.160 the singing ability to produce a strong enough sound at 0:12:15.160 --> 0:12:19.440 the right frequency, but it ain't easy. In demonstrations and 0:12:19.520 --> 0:12:23.600 physics classes, folks typically use a tone producer and an 0:12:23.600 --> 0:12:27.000 amplifier and a speaker, which simplifies things, and it's also 0:12:27.440 --> 0:12:29.840 safer than holding a glass close to your face while 0:12:29.840 --> 0:12:32.640 trying to make it explode. You can also really dial 0:12:32.760 --> 0:12:36.600 into the proper frequency, and you can kind of think 0:12:36.640 --> 0:12:38.760 of this as being similar to pushing someone who is 0:12:38.800 --> 0:12:40.960 swinging on a swing set. If you push at just 0:12:41.160 --> 0:12:44.880 the right moment in their arc, you can really get 0:12:44.920 --> 0:12:48.319 them to go higher without putting in too much effort 0:12:48.320 --> 0:12:50.400 in your push but it does have to be at 0:12:50.440 --> 0:12:52.640 just the right moment within the arc of the swing 0:12:52.720 --> 0:12:56.080 to give a boost rather than interfere with the arc 0:12:56.160 --> 0:12:59.280 of the swing. The sound waves are kind of giving 0:12:59.320 --> 0:13:01.679 the glass of it just the right frequency for it 0:13:01.720 --> 0:13:05.480 to oscillate and to keep oscillating. When we come back, 0:13:05.880 --> 0:13:08.360 we'll talk about what this has to do with hard drives, 0:13:08.679 --> 0:13:12.000 and we'll talk a bit more about some misconceptions about resonants, 0:13:12.000 --> 0:13:26.920 including one that that I kind of talked about. Okay, 0:13:26.960 --> 0:13:31.120 So Rhythm Nations music video had within the music video 0:13:31.160 --> 0:13:34.640 a sound that was at a frequency that matched the 0:13:34.640 --> 0:13:38.520 hard disk drives resonant frequency when it was spinning. So 0:13:40.040 --> 0:13:43.000 if you were to play the Rhythm Nation music video 0:13:43.200 --> 0:13:46.080 on one of these laptops, that sound would start to 0:13:46.880 --> 0:13:51.240 push the platters on the hard disk drive at the 0:13:51.280 --> 0:13:53.920 frequency that they were naturally going to vibrate at, so 0:13:54.240 --> 0:13:57.440 they would start vibrating more and more, and that would 0:13:57.520 --> 0:14:01.040 cause the hard disk drive to ash and the subsequent 0:14:01.040 --> 0:14:04.400 computer crash. So how do you solve this problem? If 0:14:04.440 --> 0:14:07.480 if hard disk drives are delicate, you know, that's why 0:14:07.480 --> 0:14:11.800 they're in these very sturdy cases typically because they need 0:14:11.840 --> 0:14:15.960 to be protected from everything else. Well, if they're so delicate, 0:14:16.000 --> 0:14:19.640 how do you protect against this issue? Well, the hard 0:14:19.680 --> 0:14:22.320 disk drive is a mechanical device, and everything has already 0:14:22.320 --> 0:14:24.880 been engineered to work a specific way, so it's not 0:14:25.120 --> 0:14:28.120 super easy to change the hard disk drive. You've already 0:14:28.120 --> 0:14:31.080 sold all these laptops that have it in there. So 0:14:31.320 --> 0:14:34.280 the solution was really to create a sound filter that 0:14:34.320 --> 0:14:39.720 would mask the frequency, the resonant frequency. So essentially, this 0:14:39.800 --> 0:14:44.640 filter would block laptops from playing that specific frequency. All 0:14:44.640 --> 0:14:47.400 the other frequencies could play because they weren't going to 0:14:47.480 --> 0:14:51.640 resonate with the hard disk, but this one wouldn't, and 0:14:51.800 --> 0:14:54.120 chances are it was tough for human listeners to even 0:14:54.120 --> 0:14:56.240 tell the difference, because being able to pick out a 0:14:56.280 --> 0:14:58.760 specific frequency from a whole bunch of them in a 0:14:58.840 --> 0:15:02.240 song is and something your average person can do. So 0:15:02.280 --> 0:15:05.160 the thought was, yeah, this is technically going to have 0:15:05.200 --> 0:15:08.320 an impact on certain media that contains this frequency, but 0:15:08.440 --> 0:15:10.000 chances are no one's going to be able to tell 0:15:10.000 --> 0:15:13.520 the difference anyway, and it won't matter if it's crashing computer, 0:15:13.640 --> 0:15:16.680 So let's just block that from being able to play 0:15:16.720 --> 0:15:20.880 on these kinds of laptops. So that filter saved the day. 0:15:20.920 --> 0:15:23.720 But you could theoretically be working on your computer, and 0:15:23.720 --> 0:15:26.600 the video for him Nation might play on some other device, 0:15:27.320 --> 0:15:31.480 like say your home entertainment system. Presumably your home entertainment 0:15:31.480 --> 0:15:34.560 system would not have this sound filter on it, so 0:15:34.960 --> 0:15:37.880 your laptop might still crash because that frequency would be 0:15:37.920 --> 0:15:42.560 present in that version of the music video. So one 0:15:42.560 --> 0:15:46.240 reason I think Chen brought this up was that if 0:15:46.280 --> 0:15:48.760 we forget about these things, if we forget about these 0:15:48.840 --> 0:15:54.360 kinds of odd cases that require these patched solutions, then 0:15:54.400 --> 0:15:58.200 we end up with stuff that's no longer really necessary. So, 0:15:58.240 --> 0:16:01.680 like I said earlier, this regular problem was affecting machines 0:16:01.760 --> 0:16:05.480 sold around two thousand five. The hard drives today are different, 0:16:05.520 --> 0:16:07.680 and a lot of laptops don't even use hard disk 0:16:07.720 --> 0:16:11.320 drives anymore. They use solid state drives, which don't have 0:16:11.320 --> 0:16:14.920 any moving parts in them, And that means that filter 0:16:15.480 --> 0:16:19.080 may not actually be necessary anymore. It might not be needed, 0:16:19.120 --> 0:16:22.120 but it might still be in place on machines because 0:16:22.200 --> 0:16:25.000 it was in earlier machines, and it ends up being 0:16:25.080 --> 0:16:30.120 a carryover. So, in other words, something that was originally 0:16:30.440 --> 0:16:33.240 put in place in order to fix a problem stays 0:16:33.280 --> 0:16:36.920 in place because people haven't bothered to remove it. And 0:16:36.960 --> 0:16:39.280 if we don't remember why we put something there to 0:16:39.360 --> 0:16:42.360 begin with, we could just be living with stuff that 0:16:42.400 --> 0:16:46.080 doesn't really do anything anymore, or that can can, at 0:16:46.160 --> 0:16:50.000 least at some level impact our experience when we want 0:16:50.000 --> 0:16:53.440 to jam out to Rhythm Nation. But let's talk about 0:16:53.440 --> 0:16:57.080 some other residant frequency stories and myths, and let's start 0:16:57.160 --> 0:16:59.880 with one I kind of whiffed on last week. So 0:17:00.240 --> 0:17:03.160 I mentioned when first covering the story that subjecting something 0:17:03.160 --> 0:17:07.520 to its resonant frequency can be quite destructive, as illustrated 0:17:07.600 --> 0:17:12.520 by the wineglass demonstration that clearly shows that a resident 0:17:12.600 --> 0:17:18.480 frequency can break something well. I also mentioned suspension bridges 0:17:18.760 --> 0:17:22.120 in that particular news item, which I really should have 0:17:22.600 --> 0:17:25.119 stopped to think about, because I already knew this was 0:17:25.160 --> 0:17:29.800 not really relevant or correct, but for some reason to 0:17:29.840 --> 0:17:32.640 just skip my mind. But I was referencing a real 0:17:32.680 --> 0:17:39.560 world disaster that frequently is mentioned uh in concert with resonans, 0:17:40.000 --> 0:17:45.080 but the actual cause of the destruction wasn't resonants. The 0:17:45.160 --> 0:17:49.120 disaster in question was the collapse of the Tacoma Narrows 0:17:49.200 --> 0:17:53.280 Bridge in the state of Washington in the United States. 0:17:53.320 --> 0:17:56.840 So construction on this suspension bridge began in the nineteen thirties. 0:17:57.119 --> 0:17:59.919 The finished project opened for traffic on July first night, 0:18:00.000 --> 0:18:04.439 ten forty, and on November seven of that year we 0:18:04.560 --> 0:18:08.240 got the collapse. So first, let's talk about what a 0:18:08.320 --> 0:18:13.760 suspension bridge is. So it has advantages over your traditional 0:18:14.240 --> 0:18:18.160 solid bridges that had, you know, multiple arcs of solid 0:18:18.200 --> 0:18:21.520 material spanning whatever it is you're building the bridge across, 0:18:21.520 --> 0:18:24.240 whether it's a chasm or river or a bay or 0:18:24.240 --> 0:18:27.199 whatever it might be. One of the big advantages of 0:18:27.200 --> 0:18:30.080 a suspension bridges that you need way less material to 0:18:30.119 --> 0:18:33.720 make a suspension bridge than one of these traditional bridges were. 0:18:33.720 --> 0:18:35.600 Really the only thing you have to worry about is 0:18:35.640 --> 0:18:38.600 that the bridge is able to, you know, withstand the 0:18:38.600 --> 0:18:42.840 gravitational force of it being pulled down, right. That's it. 0:18:43.160 --> 0:18:47.600 Like otherwise they're pretty sturdy. Suspension bridges have other concerns. 0:18:47.760 --> 0:18:50.840 Suspension bridges can be lighter, that can be less expensive 0:18:51.040 --> 0:18:54.879 to build because you're using less material, and since the 0:18:54.920 --> 0:18:57.920 public typically foots the bill for a construction of bridges, 0:18:58.560 --> 0:19:02.359 making construction less spensive is a pretty high priority in 0:19:02.440 --> 0:19:06.960 most projects. So a suspension bridge consists of two towers, 0:19:07.840 --> 0:19:10.800 kind of like Tolkien, and these two towers are connected 0:19:10.840 --> 0:19:14.440 to each other by cables. Those cables also extend further 0:19:14.920 --> 0:19:19.560 to attached to either end of the bridged area. You 0:19:19.640 --> 0:19:24.240 have rods that connect these cables to the bridges surface, 0:19:24.560 --> 0:19:27.720 which is also known as the deck uh And so 0:19:27.760 --> 0:19:31.080 the deck is suspended above whatever it is. The bridge 0:19:31.119 --> 0:19:33.399 is crossing the chasm, the bay, the river, whatever it 0:19:33.480 --> 0:19:37.280 might be. Thus we get suspension bridge. Now, the Tacoma 0:19:37.400 --> 0:19:41.399 Narrows Bridge was the third longest suspension bridge at the 0:19:41.400 --> 0:19:45.000 time of its construction, and in an effort to maximize 0:19:45.040 --> 0:19:49.720 cost efficiency, the bridge was using plate girders along the 0:19:49.800 --> 0:19:53.520 sides of the bridge to provide rigidity to the deck. Now, 0:19:53.560 --> 0:19:58.560 typically instead of girders, you would use trusses, but trusses 0:19:58.560 --> 0:20:01.879 would require more material and thus would have been more expensive, 0:20:01.920 --> 0:20:05.159 So this was one of the considerations. One of the 0:20:05.160 --> 0:20:08.960 the compromises made to have the bridge be less expensive 0:20:09.080 --> 0:20:11.639 was to go with this model where you kind of 0:20:11.680 --> 0:20:15.360 had this this ribbon like effect across the bridge as 0:20:15.400 --> 0:20:20.919 opposed to trusses to make it more rigid. So this 0:20:21.000 --> 0:20:25.160 compromise meant the bridge was more flexible than other suspension bridges. 0:20:25.240 --> 0:20:30.320 Too flexible, you would say. Construction workers who were working 0:20:30.440 --> 0:20:33.040 on building the darn thing referred to it as the 0:20:33.160 --> 0:20:37.240 galloping Gurdie because of the girders and because well even 0:20:37.280 --> 0:20:39.399 before the bridge opened, it was clear that the bridge 0:20:39.560 --> 0:20:43.919 moved more than it necessarily should, at least under certain conditions. 0:20:44.440 --> 0:20:49.840 So on November seven in Washington, the winds were in 0:20:49.920 --> 0:20:54.280 high force, and as these high sustained winds were hitting 0:20:54.359 --> 0:20:59.120 the suspension bridge, vorteses were forming. So when a fluid 0:20:59.640 --> 0:21:03.920 hits a blunt object, vortices form as the fluid moves 0:21:04.000 --> 0:21:07.400 around and then beyond the object. So if you could 0:21:07.440 --> 0:21:09.200 see the wind, you would see it was creating this 0:21:09.280 --> 0:21:14.760 sort of wiggly vortices behind the components that was hitting 0:21:14.760 --> 0:21:18.919 on the bridge. And we were talking about some issues 0:21:18.920 --> 0:21:23.520 with residents here. If those vibrations were at the right frequency, 0:21:23.600 --> 0:21:26.760 then it starts to impart vibrations into the bridge itself 0:21:26.800 --> 0:21:28.919 and the bridge begins to move up and down. And that, 0:21:29.000 --> 0:21:32.000 in fact did happen, So there was at least some 0:21:32.119 --> 0:21:35.960 movement of the bridge on November seven that related to residents. However, 0:21:37.480 --> 0:21:42.040 that was not what caused the bridge to ultimately break 0:21:42.080 --> 0:21:46.479 apart and collapse. So the bridge began to twist, not 0:21:46.560 --> 0:21:49.280 just move up and down, but starting to twist along 0:21:49.320 --> 0:21:52.199 its length, and that was really the problem, and that 0:21:52.240 --> 0:21:56.760 twisting didn't come from residents. Instead, the wind was hitting 0:21:56.760 --> 0:22:00.760 these girders along the side, and the vote disease that 0:22:00.840 --> 0:22:05.520 we're forming, we're causing the bridge to move in a 0:22:05.560 --> 0:22:08.320 specific way, like one side would move down, the other 0:22:08.359 --> 0:22:12.520 side would move up. But then the bridge would try 0:22:12.600 --> 0:22:16.000 to return back to its neutral position, you know, being level, 0:22:16.119 --> 0:22:18.800 instead of being tilted to the left or to the right. 0:22:19.480 --> 0:22:22.600 But when it would return, it would go beyond its 0:22:22.640 --> 0:22:26.320 normal rest spot due to momentum, kind of like how 0:22:26.359 --> 0:22:29.320 if you pluck a string, it actually moves beyond its 0:22:29.400 --> 0:22:32.880 rest position when it when it uh when you let 0:22:32.880 --> 0:22:35.720 it go. So the wind would then push on the 0:22:35.720 --> 0:22:39.080 girders again as they had reached their other side, kind 0:22:39.119 --> 0:22:41.879 of like you know, pushing someone on a swing. And 0:22:42.760 --> 0:22:47.400 this introduced what engineers referred to as aero elastic flutter. 0:22:47.920 --> 0:22:49.359 If you hold up a sheet of paper to the 0:22:49.359 --> 0:22:51.920 wind and you see it like fluttering back and forth, 0:22:52.040 --> 0:22:55.080 vibrating kind of in your hand, you can see an 0:22:55.080 --> 0:22:59.760 example of aero elastic flutter. This is not resonance, it's 0:22:59.760 --> 0:23:04.600 a separate phenomenon. So it ends up shaking up the bridge. 0:23:04.640 --> 0:23:07.680 But it's not because it's at a resonant frequency. It's 0:23:07.720 --> 0:23:10.399 because the wind is creating these war disease that are 0:23:10.440 --> 0:23:13.800 putting additional pressures on the bridge and making it twist 0:23:13.840 --> 0:23:16.720 back and forth. And you know, when you physically move 0:23:16.760 --> 0:23:19.840 stuff like that, like if you're wiggling something over and 0:23:19.880 --> 0:23:22.719 over and over again, you weaken it. And at around 0:23:22.760 --> 0:23:26.920 eleven am, some concrete from the bridge structure broke loose 0:23:26.920 --> 0:23:29.960 from the deck and fell down. Then a cable broke 0:23:30.160 --> 0:23:33.679 and that drastically impacted stabilization, and it began to twist 0:23:33.720 --> 0:23:39.119 even more violently, and eventually the bridge buckled and collapsed. 0:23:39.800 --> 0:23:42.719 Reports say that at the peak of the twisting motion, 0:23:43.359 --> 0:23:45.399 the sidewalk on one side, like the left side of 0:23:45.400 --> 0:23:48.320 the bridge, would be nearly thirty feet higher than the 0:23:48.400 --> 0:23:51.879 sidewalk on the opposite side of the bridge, like on 0:23:51.920 --> 0:23:55.119 the right side. Um, as you were going down the bridge, 0:23:55.359 --> 0:23:59.560 and that is terrifying to think of. Also, there's film 0:23:59.600 --> 0:24:02.640 of the is happening. You can watch videos on YouTube 0:24:02.680 --> 0:24:06.280 showing the twisting of the Tacoma Narrows Bridge and it 0:24:06.440 --> 0:24:10.560 is dramatic to say the least. But as I said, 0:24:10.800 --> 0:24:15.679 resonance ultimately did not play the major part of destruction 0:24:15.840 --> 0:24:19.879 on that bridge. It did have an impact, but the 0:24:19.960 --> 0:24:26.240 actual destruction came from these vortices and the arrow elastic flutter. Now, 0:24:26.280 --> 0:24:29.879 when we come back, we'll talk about another mythical story 0:24:29.920 --> 0:24:34.320 about residents and our good friend Nicola Tesla. But first 0:24:34.359 --> 0:24:47.600 let's take a quick break Ah Tesla. Depending on what 0:24:47.720 --> 0:24:51.480 circles you run in on the Internet, Tesla can either 0:24:51.600 --> 0:24:57.040 be looked at as a very eccentric, tortured person who 0:24:57.680 --> 0:25:01.320 had to struggle with mental health both issues for much 0:25:01.359 --> 0:25:04.080 of his life and who got the raw end of 0:25:04.119 --> 0:25:07.439 the deal on more than one occasion, but also was 0:25:08.280 --> 0:25:11.720 a heck of a self promoter. Or you might see 0:25:11.760 --> 0:25:17.200 him as an unimpeachable source of genius and innovation who 0:25:17.240 --> 0:25:21.879 had come up with almost magical technologies that never manifested 0:25:21.880 --> 0:25:24.120 but he totally had them in his head, like death 0:25:24.240 --> 0:25:28.679