stingrays and bridges.
March 26, 2006 2:41 PM Subscribe
can you turn solid material into liquid by sending the proper frequency through it?
my friend got stung by a stingray two days back and last night he was telling the tale around the campfire. he said that it didn't just zap once and leave, instead it latched onto his ankle and sent pulses up his leg and generally freaked out for some time.
another bonfire attendee suggested maybe the stingray knew about a specific bridge (he said the bridge name, and that's what i'm looking for, ultimately) that some scientists figured out the frequency at which it'd turn to liquid, tested the theory, and there was a noticable ripple or swaying that occured as the frequency traveled across. so if the stingray tapped into that knowledge, he could very well have been trying to get to that frequency so that he could turn his leg into liquid/dissolve the bone.
it was all in good fun, but now i'm curious what the heck the name of that bridge is and where i can see video footage of it.
my friend got stung by a stingray two days back and last night he was telling the tale around the campfire. he said that it didn't just zap once and leave, instead it latched onto his ankle and sent pulses up his leg and generally freaked out for some time.
another bonfire attendee suggested maybe the stingray knew about a specific bridge (he said the bridge name, and that's what i'm looking for, ultimately) that some scientists figured out the frequency at which it'd turn to liquid, tested the theory, and there was a noticable ripple or swaying that occured as the frequency traveled across. so if the stingray tapped into that knowledge, he could very well have been trying to get to that frequency so that he could turn his leg into liquid/dissolve the bone.
it was all in good fun, but now i'm curious what the heck the name of that bridge is and where i can see video footage of it.
The phenomenon is Harmonic Resonance, and it worked in the Tacoma case because a bridge is basically a big pendulum which swings in a coherent fashion, whereas a legbone wouldn't have such a simple reaction to the frequency and would resonate in a more disorderly and non-destructive manner. Also, the bridge didn't 'turn to liquid', but rather start swinging wildly until its cables snapped.
posted by skree at 2:48 PM on March 26, 2006
posted by skree at 2:48 PM on March 26, 2006
And the destruction of the bridge wasn't part of an experiment but rather a freak disaster, which led to investigation into the effect of resonance on man made structure.
I'm done now, I promise.
posted by skree at 2:49 PM on March 26, 2006
I'm done now, I promise.
posted by skree at 2:49 PM on March 26, 2006
pseudo-science from star trek?
the proper frequency of what? sound waves? frequency of vibration caused by wind? of light? As far as I know, there's no such thing as a frequency of electricity (unless you're talking about varying the volts or amps with a certain frequency, which I don't think is the case)
the Stingray is not using electricity to shock you, what your friend felt was a biochemical reaction to venom.
The Tacoma Narrows Bridge did indeed fall down due to bad design involving unexpected wind resonance:
the proper frequency of what? sound waves? frequency of vibration caused by wind? of light? As far as I know, there's no such thing as a frequency of electricity (unless you're talking about varying the volts or amps with a certain frequency, which I don't think is the case)
the Stingray is not using electricity to shock you, what your friend felt was a biochemical reaction to venom.
The Tacoma Narrows Bridge did indeed fall down due to bad design involving unexpected wind resonance:
Cause of collapseposted by tiamat at 2:54 PM on March 26, 2006
The bridge was solidly built, with girders of carbon steel anchored in huge blocks of concrete. Preceding designs typically had open lattice beam trusses underneath the roadbed. This bridge was the first of its type to employ plate girders (pairs of deep I beams) to support the roadbed. With the earlier designs any wind would simply pass through the truss, but in the new design the wind would be diverted above and below the structure. Shortly after its construction in July 1940 (opened to traffic on July 1), it was discovered that the bridge would sway and buckle dangerously in windy conditions. This resonance was longitudinal, meaning the bridge buckled along its length, with the roadbed alternately raised and depressed in certain locations — one half of the central span would rise while the other lowered. Drivers would see cars approaching from the other direction disappear into valleys which were dynamically appearing and disappearing. From this behavior the bridge gained the nickname "Galloping Gertie." However, the mass of the bridge was considered sufficient to keep it structurally sound.
The failure of the bridge occurred when a never-before-seen twisting mode occurred. This is called a torsional, rather than longitudinal, mode (see also torque) whereby when the left side of the roadway went down, the right side would rise, and vice-versa, with the centerline of the road remaining still. Specifically, it was the second torsional mode, in which the midpoint of the bridge remained motionless while the two halves of the bridge twisted in opposite directions. A physics professor proved this point by walking along the centre line, unaffected by the flapping of the roadway rising and falling to each side. This vibration was due to aeroelastic flutter. Flutter occurs when a torsional disturbance in the structure increases the angle of attack of the bridge (that is, the angle between the wind and the bridge). The structure responds by twisting further. Eventually, the angle of attack increases to the point of stall, and the bridge begins to twist in the opposite direction. In the case of the Tacoma Narrows bridge, this mode was negatively damped (or had positive feedback), meaning it increased in amplitude with each cycle because the wind pumped in more energy than the flexing of the structure dissipated. Eventually, the amplitude of the motion increased beyond the strength of a vital part, in this case the suspender cables. Once several cables failed, the weight of the deck transferred to the adjacent cables which broke in turn until almost all of the central deck fell into the water.
The bridge’s spectacular self-destruction is often used as an object lesson in the necessity to consider both aerodynamics and resonance effects in structural and civil engineering. However the effect which caused the destruction of the bridge should not be confused with forced resonance (as from the periodic motion induced by a group of soldiers marching in step across a bridge). In the case of the Tacoma Narrows Bridge, there was no periodic disturbance. The wind was steady at 42 mph (67 km/h). The frequency of the destructive mode, 0.2 Hz, was neither a natural mode of the isolated structure nor the frequency of blunt-body vortex shedding of the bridge at that wind speed. The event can only be understood while considering the coupled structural and aerodynamic system.
As an aside, stingrays use venom, so I don't really know how it could have been sending any specific. frequency up his leg.
posted by borkingchikapa at 2:54 PM on March 26, 2006
posted by borkingchikapa at 2:54 PM on March 26, 2006
Response by poster: i clearly had no idea. i just knew about a bridge, frequencies/resonance and the fact that we should apply that towards time traveling.
posted by kooop at 2:55 PM on March 26, 2006
posted by kooop at 2:55 PM on March 26, 2006
stingrays use venom
There are electric rays as well.
posted by ROU_Xenophobe at 3:01 PM on March 26, 2006
There are electric rays as well.
posted by ROU_Xenophobe at 3:01 PM on March 26, 2006
If you send microwaves into a solid block of ice, it will miraculously turn into liquid water. Try it!
posted by Kirth Gerson at 3:30 PM on March 26, 2006
posted by Kirth Gerson at 3:30 PM on March 26, 2006
Just for reference (and because I love this footage), a direct QT link to the old newsreel. Pretty cool.
posted by Emperor SnooKloze at 4:37 PM on March 26, 2006
posted by Emperor SnooKloze at 4:37 PM on March 26, 2006
Kirth: No it won't, surprisingly, unless it's melted a little. It'll go pretty quick if there's liquid water on the surface for the microwaves to excite which will then melt it, but actual ice is not a substance that responds appreciably to microwaves.
If you try this make sure to put the ice cube in with a glass of water or the like, because it can cause damage to leave the microwave on with nothing in it.
posted by abcde at 4:55 PM on March 26, 2006
If you try this make sure to put the ice cube in with a glass of water or the like, because it can cause damage to leave the microwave on with nothing in it.
posted by abcde at 4:55 PM on March 26, 2006
Derail...
In the video hortense just posted (this 'un), what's the background music?
posted by matthewr at 5:17 PM on March 26, 2006
In the video hortense just posted (this 'un), what's the background music?
posted by matthewr at 5:17 PM on March 26, 2006
The bridge didn't 'turn to liquid' it resonated, just like a guitar string.
There is no frequency of anything that can turn a normal solid into a normal liquid.
posted by delmoi at 6:23 PM on March 26, 2006
There is no frequency of anything that can turn a normal solid into a normal liquid.
posted by delmoi at 6:23 PM on March 26, 2006
"...because it can cause damage to leave the microwave on with nothing in it."
I don't believe that this is still true, if it ever was. It should be easy to Google, but I'm in a lazy mood. But, anyway, that (in theory) a microwave oven cannot melt solid ice is an important clue to the fact that microwave ovens work differently than most people suppose. I'm just guessing, but I suspect most people believe simply that aiming "radiation" at something heats it up. Which is certainly true in some sense, but it is not the principle behind the function of microwave ovens.
Koop's friend seems mightily confused to me. I don't doubt that the Tacoma bridge lurks way back there in this miscomprehension, but I'm also a little puzzled at the leap from "solid things can break apart if subjected to enough stress—which vibrating them at their natural harmonics accomplishes efficiently" to "turns solids to liquids".
I suppose that in some sense we think of a bridge, for example, as a rigid structure and when we see it oscillating so dramatically and extremely as we do in the film of the Tacoma bridge, wavelike, it's enough of a contrast to encourage the leap to an assumption of liquidity.
This all comes perilously close to the matter of "liquid" and "solid" with regard to both composite materials and to some technical confusion regarding what these words mean, and what they mean in relation to viscosity. This confusion is at the root of the glass argument (which I'm trying to avoid directly summoning) because, in short, a physicist and a materials scientist have differing working definitions of these words. The pure, abstracted, physics view of these terms belie a great deal of ambiguity in the practical realm. "Waves" of any sort seen propogating across a suspension bridge powerfully implies "liquidity" to our common, practical, lay view of the world. At the same time though, it's counterintuitive because soilds don't turn to liquids in our experience other than by the application of heat and pressure.
But an important and tangible example of solids behaving like a liquid is how the topsoil (deeper than that, I think, but I can't come up with a term) sometimes visibly behaves in an earthwuake. In some cases, at the right locations, you can literally see waves propogating through the topsoil, behaving like and appearing similar to, waves in water. Of course the various stuff that makes up the soil did not melt and become liquids, but rather the whole of it in aggregate can behave like a slurry with ripples moving visibly across its surface.
And so in a true sense, a solid material, composite or pure, relatively rigid or elastic, can behave like a liquid under the right conditions. That's just another way of describing elasticity.
The Tacoma Narrows bridge shook itself to pieces because an accident of its design meant that it naturally vibrated readily and relatively efficiently when subjected to a wind from certain directions and at certain speeds. We know from pure abstraction that material waves are always composed of both their primary waves and then harmonics (waves in simple ratios to the primary). When we watch the Tacoma Narrows bridge oscillate and come apart, we're seeing an elastic solid vibrate exactly like a plucked string, except the "note" is very, very low. It's generally not very useful, for everyday people trying to undersand the world around them, to think of such things as acting like a "liquid" because a plucked string, an elastic solid, is far more readily comprehended and relevant.
On preview: "There is no frequency of anything that can turn a normal solid into a normal liquid." I don't believe this is correct. In the abstract, you could "pump" kinetic energy into a solid by means of a material wave to a suffient degree that at the molecular level, that added energy results in a state change. And it's worth considering what it means to put something under pressure and how that is and isn't distinct from the propogation of a material wave.
posted by Ethereal Bligh at 6:37 PM on March 26, 2006
I don't believe that this is still true, if it ever was. It should be easy to Google, but I'm in a lazy mood. But, anyway, that (in theory) a microwave oven cannot melt solid ice is an important clue to the fact that microwave ovens work differently than most people suppose. I'm just guessing, but I suspect most people believe simply that aiming "radiation" at something heats it up. Which is certainly true in some sense, but it is not the principle behind the function of microwave ovens.
Koop's friend seems mightily confused to me. I don't doubt that the Tacoma bridge lurks way back there in this miscomprehension, but I'm also a little puzzled at the leap from "solid things can break apart if subjected to enough stress—which vibrating them at their natural harmonics accomplishes efficiently" to "turns solids to liquids".
I suppose that in some sense we think of a bridge, for example, as a rigid structure and when we see it oscillating so dramatically and extremely as we do in the film of the Tacoma bridge, wavelike, it's enough of a contrast to encourage the leap to an assumption of liquidity.
This all comes perilously close to the matter of "liquid" and "solid" with regard to both composite materials and to some technical confusion regarding what these words mean, and what they mean in relation to viscosity. This confusion is at the root of the glass argument (which I'm trying to avoid directly summoning) because, in short, a physicist and a materials scientist have differing working definitions of these words. The pure, abstracted, physics view of these terms belie a great deal of ambiguity in the practical realm. "Waves" of any sort seen propogating across a suspension bridge powerfully implies "liquidity" to our common, practical, lay view of the world. At the same time though, it's counterintuitive because soilds don't turn to liquids in our experience other than by the application of heat and pressure.
But an important and tangible example of solids behaving like a liquid is how the topsoil (deeper than that, I think, but I can't come up with a term) sometimes visibly behaves in an earthwuake. In some cases, at the right locations, you can literally see waves propogating through the topsoil, behaving like and appearing similar to, waves in water. Of course the various stuff that makes up the soil did not melt and become liquids, but rather the whole of it in aggregate can behave like a slurry with ripples moving visibly across its surface.
And so in a true sense, a solid material, composite or pure, relatively rigid or elastic, can behave like a liquid under the right conditions. That's just another way of describing elasticity.
The Tacoma Narrows bridge shook itself to pieces because an accident of its design meant that it naturally vibrated readily and relatively efficiently when subjected to a wind from certain directions and at certain speeds. We know from pure abstraction that material waves are always composed of both their primary waves and then harmonics (waves in simple ratios to the primary). When we watch the Tacoma Narrows bridge oscillate and come apart, we're seeing an elastic solid vibrate exactly like a plucked string, except the "note" is very, very low. It's generally not very useful, for everyday people trying to undersand the world around them, to think of such things as acting like a "liquid" because a plucked string, an elastic solid, is far more readily comprehended and relevant.
On preview: "There is no frequency of anything that can turn a normal solid into a normal liquid." I don't believe this is correct. In the abstract, you could "pump" kinetic energy into a solid by means of a material wave to a suffient degree that at the molecular level, that added energy results in a state change. And it's worth considering what it means to put something under pressure and how that is and isn't distinct from the propogation of a material wave.
posted by Ethereal Bligh at 6:37 PM on March 26, 2006
Tesla is said to have invented a machine which he set to tapping one of the columns in his building. It found the harmonic frequency and gently tap-tap-tapped it to the point the building began to shake.
posted by five fresh fish at 6:45 PM on March 26, 2006
posted by five fresh fish at 6:45 PM on March 26, 2006
There is no frequency of anything that can turn a normal solid into a normal liquid.
Lasers spring to mind. Or, to be more mundane, sufficient infra-red radiation (electromagnetic waves within a particular range of frequencies) can heat solids to their melting point. The sun does just that whenever snow melts, for example.
posted by normy at 7:27 PM on March 26, 2006
Lasers spring to mind. Or, to be more mundane, sufficient infra-red radiation (electromagnetic waves within a particular range of frequencies) can heat solids to their melting point. The sun does just that whenever snow melts, for example.
posted by normy at 7:27 PM on March 26, 2006
there's no such thing as a frequency of electricity
Alternating Current
its what come out of the wall in your house.
frequency is in fact a very very very important part of electricity.
posted by I_am_jesus at 7:40 PM on March 26, 2006
Alternating Current
its what come out of the wall in your house.
frequency is in fact a very very very important part of electricity.
posted by I_am_jesus at 7:40 PM on March 26, 2006
I don't believe this is correct. In the abstract, you could "pump" kinetic energy into a solid by means of a material wave to a suffient degree that at the molecular level, that added energy results in a state change.
Lasers spring to mind. Or, to be more mundane, sufficient infra-red radiation (electromagnetic waves within a particular range of frequencies) can heat solids to their melting point. The sun does just that whenever snow melts, for example.
Yes, regardless of frequency. Laser light, sunlight, whatever turn things to liquid by heat. Energy can be transmitted at any frequency.
On the other hand, a low power laser pointer with the same frequency won't do anything.
In other words, its not the frequency, it's the amplitude.
posted by delmoi at 7:41 PM on March 26, 2006
Lasers spring to mind. Or, to be more mundane, sufficient infra-red radiation (electromagnetic waves within a particular range of frequencies) can heat solids to their melting point. The sun does just that whenever snow melts, for example.
Yes, regardless of frequency. Laser light, sunlight, whatever turn things to liquid by heat. Energy can be transmitted at any frequency.
On the other hand, a low power laser pointer with the same frequency won't do anything.
In other words, its not the frequency, it's the amplitude.
posted by delmoi at 7:41 PM on March 26, 2006
In other words, its not the frequency, it's the amplitude.
Actually, the frequency is a factor in that different materials are transparent or opaque at different frequencies. Microwave ovens work because water is opaque to 12cm radio waves, while plastics, glass and ceramics are transparent at the same frequency. So you can use plastics in a kW microwave that would melt if placed next to a kW 500nm light source.
So you need both a high total power, and a frequency at which your target material is highly opaque. It is probably is a bad idea to use "amplitude" here because of the quantum nature of light.
posted by KirkJobSluder at 10:53 PM on March 26, 2006
Actually, the frequency is a factor in that different materials are transparent or opaque at different frequencies. Microwave ovens work because water is opaque to 12cm radio waves, while plastics, glass and ceramics are transparent at the same frequency. So you can use plastics in a kW microwave that would melt if placed next to a kW 500nm light source.
So you need both a high total power, and a frequency at which your target material is highly opaque. It is probably is a bad idea to use "amplitude" here because of the quantum nature of light.
posted by KirkJobSluder at 10:53 PM on March 26, 2006
Oh, and in addition, the mode by which light is converted to heat when it is absorbed by a material depends on both the material and the frequency. Microwaves work because the changing magnetic field forces polar molecules to rotate (in the process bumping into nearby molecules). Visible light heats things up by changing the energy state of electrons in chemical bonds.
posted by KirkJobSluder at 11:11 PM on March 26, 2006
posted by KirkJobSluder at 11:11 PM on March 26, 2006
"In other words, its not the frequency, it's the amplitude."
KirkJobSluder says concisely what I just wrote at great length and deleted.
But I still want to mention that it's important to realize that EM waves and material waves are not the same sort of thing. But if you are thinking they are, or that EM waves are relevant to this discussion, then as KJS explains, the efficiency of the conversion to the mechanical energy of heated water molecules is highly dependent upon frequency.
And one reason we call both EM and mechanical waves "waves" is because there's a number of things about both that are wave-like. Just as there is a resonance frequency of a microwave with regard to a liquid water molecule, there are resonance frequencies of simple matter compression waves with regard to their medium and other objects which interact with it. The most clear example of this are wind musical instruments. They have their tonality because the instrument itself resonates to varying degress at different frequencies in response to the frequency of the proximate source, such as the vibration of a reed. A resonance allows what is mostly a turbulent mechanical energy to be more efficiently converted to the kinetic energy of the regular sound waves that a musical instrument produces.
Also, I while thinking about this, and writing and deleting something much longer than the previous paragraph, I hypothesized that insofar as the Tacoma bridge was concerned, the wind didn't have a "frequency" (though it certainly did in some sense or another), but the turbulence caused by the wind's flow through the bridge's structure caused some portion of the bridge's structure to vibrate at certain frequencies that resonate strongly with other parts of the bridge structure. I wondered if the initial frequency might have been a vibration of the suspension cables. And it's enlightening, too, to compare this to a musical instrument.
In sum, the very notion of "wavelengths" implies a variation of a transfer of energy relative to the frequency of a wave, EM or material. And we're surrounded by examples of conversion efficiencies varying by frequency. Amplitude most certainly is not all that matters.
posted by Ethereal Bligh at 11:24 PM on March 26, 2006
KirkJobSluder says concisely what I just wrote at great length and deleted.
But I still want to mention that it's important to realize that EM waves and material waves are not the same sort of thing. But if you are thinking they are, or that EM waves are relevant to this discussion, then as KJS explains, the efficiency of the conversion to the mechanical energy of heated water molecules is highly dependent upon frequency.
And one reason we call both EM and mechanical waves "waves" is because there's a number of things about both that are wave-like. Just as there is a resonance frequency of a microwave with regard to a liquid water molecule, there are resonance frequencies of simple matter compression waves with regard to their medium and other objects which interact with it. The most clear example of this are wind musical instruments. They have their tonality because the instrument itself resonates to varying degress at different frequencies in response to the frequency of the proximate source, such as the vibration of a reed. A resonance allows what is mostly a turbulent mechanical energy to be more efficiently converted to the kinetic energy of the regular sound waves that a musical instrument produces.
Also, I while thinking about this, and writing and deleting something much longer than the previous paragraph, I hypothesized that insofar as the Tacoma bridge was concerned, the wind didn't have a "frequency" (though it certainly did in some sense or another), but the turbulence caused by the wind's flow through the bridge's structure caused some portion of the bridge's structure to vibrate at certain frequencies that resonate strongly with other parts of the bridge structure. I wondered if the initial frequency might have been a vibration of the suspension cables. And it's enlightening, too, to compare this to a musical instrument.
In sum, the very notion of "wavelengths" implies a variation of a transfer of energy relative to the frequency of a wave, EM or material. And we're surrounded by examples of conversion efficiencies varying by frequency. Amplitude most certainly is not all that matters.
posted by Ethereal Bligh at 11:24 PM on March 26, 2006
Tesla is said to have invented a machine which he set to tapping one of the columns in his building. It found the harmonic frequency and gently tap-tap-tapped it to the point the building began to shake.
I did some research into this, seeking to duplicate it for nefarious purposes. It was called the Earthquake Machine, and you can buy a (terrible) book purporting to contain the plans, but they're actually sort of useless because there's no documentation so it's just a bunch of puzzling shapes on the page.
The result of my research, though, was that the machine did not find the resonant frequency in any automatic manner. Tesla estimated the resonant frequency in his head, and then configured the machine to tap at that rate. I believe that most modern structures are engineered to be resonant in non-sinusoidal ways, so that it's not possible to wreck them in this manner anymore.
The Earthquake Machine was just an efficient variable-frequency vibrator with good power at low frequencies. That's what Tesla told the ladies, anyway.
posted by breath at 12:48 AM on March 27, 2006
I did some research into this, seeking to duplicate it for nefarious purposes. It was called the Earthquake Machine, and you can buy a (terrible) book purporting to contain the plans, but they're actually sort of useless because there's no documentation so it's just a bunch of puzzling shapes on the page.
The result of my research, though, was that the machine did not find the resonant frequency in any automatic manner. Tesla estimated the resonant frequency in his head, and then configured the machine to tap at that rate. I believe that most modern structures are engineered to be resonant in non-sinusoidal ways, so that it's not possible to wreck them in this manner anymore.
The Earthquake Machine was just an efficient variable-frequency vibrator with good power at low frequencies. That's what Tesla told the ladies, anyway.
posted by breath at 12:48 AM on March 27, 2006
Another example of resonance is the London Millenium Bridge, which started vibrating when people walked across it during the opening ceremony. The people were part of the resonant structure, without being aware of it. The bridge started vibrating slightly, people unconsciously adjusted their gait to match the movement of the bridge, and that amplified the vibration in a positive feedback loop.
So maybe alien stingrays could send vibrations into our brains at just the right frequencies. That would make our brains respond by resonating in sync, letting the stingrays control our thoughts.
posted by fuzz at 7:09 AM on March 27, 2006
So maybe alien stingrays could send vibrations into our brains at just the right frequencies. That would make our brains respond by resonating in sync, letting the stingrays control our thoughts.
posted by fuzz at 7:09 AM on March 27, 2006
From the question (and the answers above) I'm not sure if you're talking about a vibrational wave or an electric one. People above have covered EM quite well, so I'll talk about vibrational effects.
It's easy to heat with sound, which can turn any solid into a liquid. We ultrasonicate stuff all the time and keeping the temperature down is a real problem. I've melted waxes ultrasonically.
In it's most extreme form, ultrasonic waves causing bubble collapse with such violence that molecules are ripped apart. This is called sonoluminescence. Some people think that this might even be high enough energy to cause nuclear fusion, but that's not been proven yet.
posted by bonehead at 8:25 AM on March 27, 2006
It's easy to heat with sound, which can turn any solid into a liquid. We ultrasonicate stuff all the time and keeping the temperature down is a real problem. I've melted waxes ultrasonically.
In it's most extreme form, ultrasonic waves causing bubble collapse with such violence that molecules are ripped apart. This is called sonoluminescence. Some people think that this might even be high enough energy to cause nuclear fusion, but that's not been proven yet.
posted by bonehead at 8:25 AM on March 27, 2006
« Older Dealing with financial woes of the socially inept. | Modeling Agencies in the Bay Area Newer »
This thread is closed to new comments.
posted by skree at 2:44 PM on March 26, 2006