Janet Jackson and Nikola Tesla

or at least of certain laptops. Some folks discovered that if they played this video on their laptop computer, or if their laptop computer was close to something else that was playing this music video, the computer would spontaneously crash. Now, to be clear, these computers were not nasty, as miss Jackson might say. They were not music critics. It turns out that a sound played in that music video matched the resonant frequency of the hard disk drives in these laptops,

though it took some time to suss that out. Chen said that these were hard drives that we're spending at five thousand four rpm. That's revolutions per minute, so going around five thousand, four hundred times every minute. That's actually on the lower end of what we typically see with hard disk drives, they can top out at more than twice as fast as that. But it's not bad. I mean, you can still go out and buy a hard disk drive today that's at five thousand PM. People typically like

faster ones. It means that you can read and write information to such a hard drive faster. Anyway, the sound from the music video was causing the hard drives to vibrate. The platters inside would vibrate, and ultimately this would prompt the computers to crash. So today I thought i'd talk a little bit about hard drives, a bit of out resonant frequencies, how a sound could cause a hard drive to actually crash, and maybe talk about some myths surrounding resonance,

including one that I kind of perpetuated last week. So I gotta hold myself up to a correction here anyway. First up, if you were to take a hard drive apart, don't do that, by the way, You're more than likely going to destroy it. But you would see that inside the hard disk drive you have a spindle, and on the spindle would be at least one disc or platter.

More likely it would actually be more than one, perhaps a stack of them, and each platter would be separated from its neighbors by a small gap, and the platters are kind of similar to a compact disk in some ways, but compact discs store information that's read and written through an optical drive. So with light laser specifically, hard disks store information magneticle, not through optics. Now, this platter or these platters are what spin inside a hard disk drive coding.

The platter is a thin layer of magnetic grains, so using an electro magnetic head, the computer can write data to the platter by realigning these magnetic grains so that they point in a specific direction, essentially pointing magnetic north or pointing magnetic south, and thus they can represent zeros

and ones. When the platter spins beneath the head or above the head, depending on how this goes, and the head is in passive mode, there's a little detector essentially on the head that can pick up the magnetic fluctuations from these aligned regions that are passing near it as the disc is spinning, so it's being read now. The head in this case can look a bit like tweezers in a sense. There's typically a pair of arms, one that goes over the top of the platter one that's beneath.

They are not making contact with the platter. In fact, if they were to touch the platter, that would damage the hard drive. You gotta keep in mind, these platters are spinning super fast, so these electro magnets are separated from the platters. They're not actually touching, they're they're hovering above and below um. So really like every head is usually a pair of red Wright heads. There's one on top, one beneath each platter that allows the computer to store

information on either side of platters. And as I said, your typical hard drive often has several of these platters arranged in a stack, separated from each of them by a small gap, and each platter has its own read right head. But that is the super basic way that hard drives work. I'm not even getting into things like actually how you store a file on these platters, because it's not as simple as like the roove on a on a vinyl album representing a song. It's not like that.

But the reason for this rapid rotational speed is that you do want to be able to read and write information from this hard disk drive quickly. And you know, if it didn't spin at these fast rates, it would take forever, which is hyperbolie. It would take a really long time for your computer to retrieve stored information from the hard disk drive. And it blows my mind that you can have platters spending times per minute or faster and read or write information to those platters, storing gigabytes

of data in the process. Technology is really kind of like magic, except you know it works. Now. If you have a mechanical device like this, clearly everything needs to be improper alignment or else you're going to have problems. Jostling a hard disk drive can potentially knock a disc off kilter, which would mean that once the spin doll that the disks start on starts to spin, you're gonna

have some damage, possibly catastrophic damage. The platters need to maintain both horizontal and vertical alignment, and honestly, knowing how delicate a hard disk drive can be, I'm actually amazed that my first ever MP three players survived for so

many years. I had a creative Zen device which had a spinning hard disk drive inside of it, which is a very tiny little hard drive, and I say I'm amazed that survived because I know that thing took a tumble more than once, and the impact could have been enough to damage the hard drive, but I guess I had more luck than brains anyway. According to a data recovery firm called drive Savers, of hard disk drive failures are the result of damage recording surfaces, typically created as

the result of a physical shock. Other potential causes for failure include things like circuit board problems uh stiction, which is the combination of friction and sticking, where if you haven't used a hard des drive for a long time, sometimes there can be this kind of friction sticking issue that impedes the disks from spinning. And also drive motor failure, which makes up like less than a percent of all the hard disk drive failures. So usually the motor doesn't

isn't the problem. By the time the motor has given out, something else has already failed in that hard disk. Now, if something were to cause the hard drive to stop spinning while it's in operation, you get a hard disk drive failure in that prompts a full crash of the computer. And this brings us to Janet or miss Jackson. If I'm nasty, and it turns out that the song Rhythm Nation has within it a frequency that resonates with a certain popular model of hard disk drives from many years ago.

So this isn't really about current tech. We're actually talking about machines that were sold around the year two thousand five. So really kind of amazing that this even became a problem, right because Rhythm Nation came out in nine, this particular uh laptop that was prone to this kind of stuff, or these laptops, I should say, because they all had this hard drive in common. It wasn't the laptops fault.

Those were sold around two thousand five, and specifically, the the sound frequency from the music video would resonate with the natural resonant frequency produced by the hard drive when the platter is spinning. So let's talk about frequency and sound and resonance for a bit. With waves. Frequency refers to the number of waves that pass a fixed point within a given amount of time, and we use the

metric hurts to measure frequencies. So one hurts is equal to one wave passing a fixed point in one second. Two hurts would mean two waves would pass that point in one second. Now, notice I didn't say sound waves here because Hurts can refer to any kind of wave or oscillation, so we can use frequency to talk about stuff like light or sound or all sorts of other things.

But in this episode we're mostly concerned with sound. So if you were to play the middle C on a piano, and assuming that piano had been tuned according to VERD tuning, which is not standard uh, the note would produce a frequency of two hundred fifty six hurts. So that means the sound wave travels at two hundred fifty six waves past a given fixed point per second. Now, sound waves are really vibrations, right. Physical vibrations is a physical phenomenon.

It is why there's no sound in space, because you don't have stuff close enough to transmit vibration from one thing to another, and you have to have stuff close enough to vibrate and affect other things in order for that to propagate for it to travel. Most of the stuff we hear is traveling through the air, So in this case, the vibrations we're talking about are typically these

little fluctuations in air pressure. You can kind of imagine that these changes in air pressure are effectively pushing against and pulling on your ear drum. Just slightly, which then transmits those vibrations to our inner ear. Our brains ultimately interpret this signal as sound, and the frequency at which the air fluctuations affect our ear drums determines what pitch we hear. So slower frequencies produce lower pitches. Faster frequencies

produce faster pitches. Two fifty six fluctuations like full fluctuations per second produces middle C. Now, let's talk about resonant frequencies. Systems have a frequency that they tend to oscillate at. The reason middle C sounds like middle C is that there is a string in that piano that's at the right length and it's at the right tension to produce

that frequency. When that string is struck by a hammer, when you push down on the key, a hammer strikes the string and it vibrates at this frequency, and thus we hear that middle C. Similarly, if you take a wine glass and you tap the wine glass, you will hear it ring out a tone. That tone is the resonant frequency, the natural frequency for that glass. It's the frequency at which it tends to oscillate naturally when struck. Now, if you were to produce that same tone near the glass,

you would cause the glass to vibrate. You would induce vibration in the glass. If you produce the tone with enough volume or amplitude, if we're talking about waves, that vibration can start to deform the glass enough to cause the wine glass to shatter. And you've probably seen examples of this, you know. The classic one is you have an opera singer singing a clear note and holding a

wine glass and the glass inevitably breaks apart. That is possible if you have someone with the lung power and the singing ability to produce a strong enough sound at the right frequency, but it ain't easy. In demonstrations and physics classes, folks typically use a tone producer and an amplifier and a speaker, which simplifies things, and it's also safer than holding a glass close to your face while

trying to make it explode. You can also really dial into the proper frequency, and you can kind of think of this as being similar to pushing someone who is swinging on a swing set. If you push at just the right moment in their arc, you can really get them to go higher without putting in too much effort in your push but it does have to be at just the right moment within the arc of the swing to give a boost rather than interfere with the arc

of the swing. The sound waves are kind of giving the glass of it just the right frequency for it to oscillate and to keep oscillating. When we come back, we'll talk about what this has to do with hard drives, and we'll talk a bit more about some misconceptions about resonants, including one that that I kind of talked about. Okay, So Rhythm Nations music video had within the music video a sound that was at a frequency that matched the

hard disk drives resonant frequency when it was spinning. So if you were to play the Rhythm Nation music video on one of these laptops, that sound would start to push the platters on the hard disk drive at the frequency that they were naturally going to vibrate at, so they would start vibrating more and more, and that would cause the hard disk drive to ash and the subsequent

computer crash. So how do you solve this problem? If if hard disk drives are delicate, you know, that's why they're in these very sturdy cases typically because they need to be protected from everything else. Well, if they're so delicate, how do you protect against this issue? Well, the hard disk drive is a mechanical device, and everything has already been engineered to work a specific way, so it's not super easy to change the hard disk drive. You've already

sold all these laptops that have it in there. So the solution was really to create a sound filter that would mask the frequency, the resonant frequency. So essentially, this

filter would block laptops from playing that specific frequency. All the other frequencies could play because they weren't going to resonate with the hard disk, but this one wouldn't, and chances are it was tough for human listeners to even tell the difference, because being able to pick out a specific frequency from a whole bunch of them in a

song is and something your average person can do. So the thought was, yeah, this is technically going to have an impact on certain media that contains this frequency, but chances are no one's going to be able to tell the difference anyway, and it won't matter if it's crashing computer, So let's just block that from being able to play on these kinds of laptops. So that filter saved the day.

But you could theoretically be working on your computer, and the video for him Nation might play on some other device, like say your home entertainment system. Presumably your home entertainment system would not have this sound filter on it, so your laptop might still crash because that frequency would be

present in that version of the music video. So one reason I think Chen brought this up was that if we forget about these things, if we forget about these kinds of odd cases that require these patched solutions, then we end up with stuff that's no longer really necessary. So, like I said earlier, this regular problem was affecting machines sold around two thousand five. The hard drives today are different, and a lot of laptops don't even use hard disk

drives anymore. They use solid state drives, which don't have any moving parts in them, And that means that filter may not actually be necessary anymore. It might not be needed, but it might still be in place on machines because it was in earlier machines, and it ends up being a carryover. So, in other words, something that was originally put in place in order to fix a problem stays

in place because people haven't bothered to remove it. And if we don't remember why we put something there to begin with, we could just be living with stuff that doesn't really do anything anymore, or that can can, at least at some level impact our experience when we want to jam out to Rhythm Nation. But let's talk about some other residant frequency stories and myths, and let's start

with one I kind of whiffed on last week. So I mentioned when first covering the story that subjecting something to its resonant frequency can be quite destructive, as illustrated by the wineglass demonstration that clearly shows that a resident frequency can break something well. I also mentioned suspension bridges in that particular news item, which I really should have stopped to think about, because I already knew this was not really relevant or correct, but for some reason to

just skip my mind. But I was referencing a real world disaster that frequently is mentioned uh in concert with resonans, but the actual cause of the destruction wasn't resonants. The disaster in question was the collapse of the Tacoma Narrows Bridge in the state of Washington in the United States. So construction on this suspension bridge began in the nineteen thirties. The finished project opened for traffic on July first night, ten forty, and on November seven of that year we

got the collapse. So first, let's talk about what a suspension bridge is. So it has advantages over your traditional solid bridges that had, you know, multiple arcs of solid material spanning whatever it is you're building the bridge across, whether it's a chasm or river or a bay or whatever it might be. One of the big advantages of a suspension bridges that you need way less material to make a suspension bridge than one of these traditional bridges were.

Really the only thing you have to worry about is that the bridge is able to, you know, withstand the gravitational force of it being pulled down, right. That's it. Like otherwise they're pretty sturdy. Suspension bridges have other concerns. Suspension bridges can be lighter, that can be less expensive to build because you're using less material, and since the public typically foots the bill for a construction of bridges, making construction less spensive is a pretty high priority in

most projects. So a suspension bridge consists of two towers, kind of like Tolkien, and these two towers are connected to each other by cables. Those cables also extend further to attached to either end of the bridged area. You have rods that connect these cables to the bridges surface, which is also known as the deck uh And so the deck is suspended above whatever it is. The bridge is crossing the chasm, the bay, the river, whatever it

might be. Thus we get suspension bridge. Now, the Tacoma Narrows Bridge was the third longest suspension bridge at the time of its construction, and in an effort to maximize cost efficiency, the bridge was using plate girders along the sides of the bridge to provide rigidity to the deck. Now, typically instead of girders, you would use trusses, but trusses would require more material and thus would have been more expensive,

So this was one of the considerations. One of the the compromises made to have the bridge be less expensive was to go with this model where you kind of had this this ribbon like effect across the bridge as opposed to trusses to make it more rigid. So this compromise meant the bridge was more flexible than other suspension bridges.

Too flexible, you would say. Construction workers who were working on building the darn thing referred to it as the galloping Gurdie because of the girders and because well even before the bridge opened, it was clear that the bridge moved more than it necessarily should, at least under certain conditions. So on November seven in Washington, the winds were in high force, and as these high sustained winds were hitting

the suspension bridge, vorteses were forming. So when a fluid hits a blunt object, vortices form as the fluid moves around and then beyond the object. So if you could see the wind, you would see it was creating this sort of wiggly vortices behind the components that was hitting on the bridge. And we were talking about some issues with residents here. If those vibrations were at the right frequency, then it starts to impart vibrations into the bridge itself

and the bridge begins to move up and down. And that, in fact did happen, So there was at least some movement of the bridge on November seven that related to residents. However, that was not what caused the bridge to ultimately break apart and collapse. So the bridge began to twist, not just move up and down, but starting to twist along its length, and that was really the problem, and that

twisting didn't come from residents. Instead, the wind was hitting these girders along the side, and the vote disease that we're forming, we're causing the bridge to move in a specific way, like one side would move down, the other side would move up. But then the bridge would try to return back to its neutral position, you know, being level, instead of being tilted to the left or to the right.

But when it would return, it would go beyond its normal rest spot due to momentum, kind of like how if you pluck a string, it actually moves beyond its rest position when it when it uh when you let it go. So the wind would then push on the girders again as they had reached their other side, kind of like you know, pushing someone on a swing. And this introduced what engineers referred to as aero elastic flutter.

If you hold up a sheet of paper to the wind and you see it like fluttering back and forth, vibrating kind of in your hand, you can see an example of aero elastic flutter. This is not resonance, it's a separate phenomenon. So it ends up shaking up the bridge. But it's not because it's at a resonant frequency. It's because the wind is creating these war disease that are putting additional pressures on the bridge and making it twist

back and forth. And you know, when you physically move stuff like that, like if you're wiggling something over and over and over again, you weaken it. And at around eleven am, some concrete from the bridge structure broke loose from the deck and fell down. Then a cable broke and that drastically impacted stabilization, and it began to twist even more violently, and eventually the bridge buckled and collapsed.

Reports say that at the peak of the twisting motion, the sidewalk on one side, like the left side of the bridge, would be nearly thirty feet higher than the sidewalk on the opposite side of the bridge, like on the right side. Um, as you were going down the bridge, and that is terrifying to think of. Also, there's film of the is happening. You can watch videos on YouTube showing the twisting of the Tacoma Narrows Bridge and it

is dramatic to say the least. But as I said, resonance ultimately did not play the major part of destruction on that bridge. It did have an impact, but the actual destruction came from these vortices and the arrow elastic flutter. Now, when we come back, we'll talk about another mythical story about residents and our good friend Nicola Tesla. But first

let's take a quick break Ah Tesla. Depending on what circles you run in on the Internet, Tesla can either be looked at as a very eccentric, tortured person who had to struggle with mental health both issues for much of his life and who got the raw end of the deal on more than one occasion, but also was

a heck of a self promoter. Or you might see him as an unimpeachable source of genius and innovation who had come up with almost magical technologies that never manifested but he totally had them in his head, like death rays and stuff. Um. I tend to go on the more modest side, uh and and I would never say that Tesla was not a genius. He clearly was a genius,

but again he was a born self promoter. In fact, I would say he was pretty darn similar to Thomas Edison, in that regard, and a lot of folks kind of referred to Thomas Edison as being lex luthor to Nick Nicola Tesla's superman. Uh that there were two sides of the same coin. Uh. I think that's being more than a little melodramatic personally. But one thing Nikola Tesla experimented with was an oscillating or reciprocating electric generator, and in fact he got it to work. The principle was very

much sound. It's just that he found a better way of accomplishing what his goal was, which was to create a a sustained, consistent alternating current. So let's break this down. Now. Imagine that you've got kind of like it looks kind of like a metal post that's several inches long, maybe you know, maybe up to a foot or maybe even bigger, uh, and cylindrical in nature. Inside of that, you had a chamber where there was a piston that could go up

and down the chamber cylinder. This piston would drive a post like an iron core that had copper wire wrapped around it, and this wire would connect to a circuit of some sort and that would freely move up and down the length of this one chamber based upon the movements of this piston inside a cylinder. Now surrounding this rod with copper coil on it was an electro magnet connected to a battery. So a battery generates direct current.

That means the electricity always flows in the same direction from uh, I mean, if you're talking about you're talking about the way Benjamin Franklin thought of it. It goes from positive to negative. The actual electrons go from negative to positive. But you know, you you get what I'm saying, So it always flows in that direction that cannot reverse with direct current. So the electro magnet inside this piston generator thing was acting just like a stationary permanent magnet was.

In fact, Tesla could have just put a very powerful permanent magnet in this thing. It would have worked the same way when you move a conductor through a stationary magnetic field. So like you have a conductive material and you pass it through a magnetic field that induces electricity to flow within the conductor. You induce electric current by moving the conductor up and down past this electric magnetic field.

Rather then you know, having this oscillating or reciprocating action as the the coil moves up and down through this this magnetic field. You actually have a similar effect as if the magnetic field was fluctuating, was reversing its current back and forth. So it's it's almost the same as if the the coil were stationary, but the electro magnet around it was powered by alternating current. Now, the reason why this is important is that that would actually reverse

the flow of electricity through that coil. You generate alternating current by moving this this coil up and down through this magnetic field. So you take a direct current source from the battery into this reciprocating electric generator, and by moving this piston up and down, you can output alternating current. UH. To provide the up and down power to move the coil, we have to go to the piston. Now, in this

early invention, the piston was driven by steam power. Now, I wish I could adequately describe Tesla's design here because it really was genius. I mean, it was a beautiful approach to creating a piston that can move up and down be driven by steam, and it was beautifully simple uh in design. However, to describe it is really hard to do without visual aids. There are videos that You can watch that show how this worked, and I recommend

you check it out if you want. But what you need to know is that Tesla's piston served also as a valve, and that valve controlled where steam could enter an exit the cylinder that the piston was moving in. So Tesla was using steam for both directions of the stroke of the piston. So the upward and the downward

movements of the piston were driven by steam. Steam would push the piston down, steam would push the piston back up, and this would drive that coil to move up and down the magnetic field further up inside the electric generator, and thus the piston was providing the reciprocating motion. Now

let's get to resonance. So the story Tesla told is that he was working in the lab late one night when his eyes beheld an eerie sight because his reciprocating electric generator or some oscillator that was similar to it because it changes from story to story, was moving at the same frequency as his buildings natural frequency. Some versions of the story say that he had attached the piston to a girder to provide stability, because obviously, if you

have something that's moving up and down rapidly. It's going to be clattering all over the place unless you has

strap it down somewhere. So he was saying that he was tuning in the resonance or the frequency rather of this oscillator, so it resonated with the girder that it was connected to within his building, and thus he began to introduce increasingly violent vibrations into the building, and those vibrations continue to build an intensity, and it led to a small man made earthquake, leading a lot of people

to call this Tesla's earthquake machine. Then the story goes that police and ambulances responded to the scene and they got there justice Tesla was either taking a sledgehammer to his generator to stop it from tearing the joint apart, or that he had already stopped it and that he was just playing coy and saying, oh, I didn't even notice an earthquake. Now, could such a thing be possible?

Maybe you could theoretically create a reciprocating device and tune it to a frequency that induces vibrations in a structure, And theoretically you could maybe do one powerful enough that ultimately it would start to cause damage. But We need to keep several things in mind here. One is that

Tesla mostly told this story in his declining years. Uh. The account I see most frequently cited comes from an article that was published in nineteen on Tesla's seventy ninth birthday, and that the actual shaking of the building was said to have happened either in eighty seven or eight eight eight, according to that article. So even that article doesn't get specific on when this supposedly happened, and a different source targets the the event to eight, so we don't even

have agreement of when this supposed earthquake happened. Tesla also told other stories at that same party that are referenced in the article I was mentioning, like the fact that he had discovered cosmic radiation before anyone else did, he just didn't think to tell anyone about it, and that he found there are particles that traveled perhaps as much as five times faster than the speed of light, which

just isn't true. So my point is that Tesla is at best and unreliable source when it comes to stories about his own work. In many ways, his life depended upon his fame at this stage in his life he was drifting from hotel to hotel in an effort to avoid homelessness, and hotels would be happy to receive the famous Tesla at least initially, but eventually his welcome would wear out and he'd take the show on the road again.

So I have my doubts about Tesla's stories. At least I doubt he was producing enough vibration to simulate an earthquake. And I definitely doubt the versions that suggests that not only was this building shaking, but that glass was bursting from nearby buildings and that the road outside was quaking. I don't believe that for a second. And one reason I doubt this is that you've got a lot of material and buildings that can have a dampening effect on vibrations. Right.

Not everything is contributing to this resonant frequency, this resonant oscillation. Some stuff ends up resisting that and inhibiting that. And typically, or usually, like the larger the thing you're trying to to to vibrate, the larger the thing you're trying to shake apart, the more force you need to really get things going. In other words, if you walk up to a building and you happen to know exactly how frequently you need to tap on a girder to match the

frequency of that girder, and you do it. Uh yeah, you're tapping at it, and you could probably feel those vibrations along the length of the girder, but you're not gonna force it to break apart. You'd have to use more force than that. Pushing a kid at just the right moment in the swings arc gives the kid a significant boost, but you do have to push. You can't just you know, like tap, it's not gonna do anything. So the source of the vibrations have to produce waves

of significant amplitude to affect something like a building. Same thing with the wine glass. Right, If you can produce the right note, but you're not producing it at a high enough volume, the glass won't break. It will vibrate. If you put something like a piece of paper inside the glass, you'll see the paper jump around because the glass will be vibrating, but it won't be enough to cause the glass to deform to the point where it breaks.

So I just doubt that Tesla's oscillator would be able to do it, particularly the way he was describing it. In his later descriptions of the technology, he said that he had as an air powered one that could fit in your pocket. So it was like a smaller version of the oscillating electric generator. So technically, yes, I think you could do this if you had something that was significantly powerful enough to introduce vibrations that would ultimately cause destruction.

I just don't think Tesla's did it. I don't think so, but I could be wrong. It's it's the hard thing is that there just aren't any reliable sources outside of Tesla, and Tesla was not a reliable source. He made a lot of claims that have been unsubstantiated, and many of them I believe were really meant to help keep him in the public eye so that he could, you know, live out his life with as little hardship as he could. Again, he lived rather tortured existence, So no hard feelings against

the guy. He was just trying to get through life under frustrating, to say the least circumstances. I mean, I could go into the whole story about Tesla and Marconi. If you think Tesla and Edison is one of those big tales of two people, you know, posed against each other, which really I would say Edison Westinghouse really is that story. That's nothing compared to Marconi and and Tesla in my mind.

But that's the story for another time. Anyway, hope you enjoyed this discussion about resonant frequencies and how a Janet Jackson music video was shutting down computers left and right in two thousand five. I found it interesting. I hope you did too. If you would like me to cover something specific on tech stuff, please reach out to me. One way to do that is to download the I

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