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60 tons of mass flying at 300mph (using .5*m*v^2) has kinetic energy equivalent to 0.18 tons of TNT. Nowhere close to the to the energy equivalent of 900 tons of TNT that's released by burning the fuel.
Still, I now understand your theory a bit better. I'll try to find some time to give it some thought.
Hi hippiefired,
I gave your proposal a little thought.
The first thing I should point out is that part of your theory seems to be based on a misconception about resonance. Let’s consider your tuning fork example. Strike the fork and it rings. A good fork will actually ring for a relatively long time. But the fact that you can hear it and the fact the you can feel its vibrations as you hold the base between your fingers shows that its energy is dissipating into the air and into your fingers. It’s also losing energy to internal friction between the very molecules of the vibrating fork. These drains dampen the oscillations until, for all practical purposes, the fork is still. Now strike the fork again. Place the base on a resonator, like the body of an acoustic guitar. Suddenly the sound is so much louder. It’s as if the resonator amplified and added energy to the output of the fork. In fact there is no more energy than the energy of you gave the fork by striking it. The energy that was lost to you fingers is not drain into the soundboard of the guitar and causing it to vibrate. So why is the sound louder now? The small arms of fork are inefficient movers of the air around them. On the other hand the broad flat surface of the resonator is quite good at moving air, causing it to vibrate. The greater the volume of vibrating air, the greater the volume of the sound you hear. Now that the tuning fork is driving the soundboard, it will lose energy and dampen more quickly.
The above example merely shows how soundboards are effective at “amplifying” an aural experience without adding energy to the system. A better example of resonance is a playground swing. A swing loses energy by wave propagation through the frame, through air resistance and friction at the joints. Nevertheless, by carefully timing your thrusts you can drive the swing to ever greater amplitudes of arc. Clumsy timing can have the opposite effect of actually dampening the motion. Each push does work on the swing, either to dampen its motion or amplify it depending on when and where one pushes. By careful timing one can accumulate and in a sense store energy in the swing. The more energy stored in the swing, the greater the amplitude of its motion. Bridges too can be made to vibrate. If driven at the right frequency a bridge can be made to collapse, as in the Tacoma disaster. Swings and oscillating bridges do not add to the energy that’s employed to drive them. If they are driven at their resonate frequency they will accumulate and store the energy. The greater the amount of stored energy, the greater the amplitude of motion. If the amplitude is high enough the swing will wrap around the pole or the bridge will crumble. [Just like storing energy as heat in an oven. The more energy stored, the higher the temperature, regardless of the low temperature required to burn the fuel].
Your suggestion is that oscillations initiated by the impact on the twin tower were amplified in the way a resonator amplifies the sound of a tuning fork. As I’ve tried to explain above, the resonator does not add energy to the oscillations; it only makes use of the energy provided by the tuning fork. The energy made available by a 100 ton aircraft flying at 500 mph is equivalent to the energy stored in about a half ton of TNT. This is small compared to 900 tons of TNT which is the energy equivalent to that stored in 60 tons of jet fuel. Still, a half ton of TNT is nothing to sneeze at and if placed correctly I imagine it could do considerable damage. A lot of the kinetic energy of the plane was expanded by breaching the building and stopping the plane. But some of that energy no doubt propagated through the structure as oscillations. I’m in no position to guess how much. Nor do can I guess how the waves might have propagated. (Actually at the moment I’m too lazy to guess).
I like the banana peel metaphor you engage were the towers to collapse pancake fashion (mmmm pancakes and bananas). But I’m not convinced it necessarily applies. As the top segment of the building drops like a hammer onto the next floor/ceiling, I expect that ceiling to buckle (at lightning speed) into the relatively hollow space between ceiling and floor pulling the sidewalls along with it before it crumbles and all is swept along by the plummeting hammer. Of course these sorts of details depend on the structural components of the towers with which I’ve been adverse to acquaint myself. My interest in these matters goes only so far.
I think I’ve established two things. First, pancake models can be nearly as speedy as free fall and indeed the observed ten second window is easily achieved by some pancake models of collapse like the PIP model I discussed in some detail on the first page of this thread. Second, were even a small fraction of the heat energy generated by burning 60 tons of jet fuel stored within the materials of the breached floors, temperatures exceeding the melting point of steel could be achieved. Hippiefried also points out the energy of impact is not unsubstantial: I personally don’t want to be anywhere near half a ton of TNT when it explodes.
One could go on forever debunking the so called physical evidence against the conspiracy theory; that after all is the nature of conspiracy theory...conspiracy theories have no “exit” strategy…there is no point at which the faithful are willing to say the evidence against them is conclusive. Evidence for the conspiracy is always undeniable and evidence against is always too convenient to be anything but a lie, a part of the conspiracy itself.
Hi back atcha Trish,
The problem with the pancake theory is that WTC is the first ever claim of pancaking from the top. We've seen lots of pancaked buildings in the aftermath of earthquakes. Most of them happen after the quake subsides. There's that pesky gravity law again. They're all failures from the bottom. The ground floor collapses first. The footage I've seen of 9/11 shows the collapse starting above the impact floor. What broke the top floors loose? If it was a pancake, it would have started at the collision point. You know. Where all that burning kerosene melted the floors loose. A gap would have appeared, if only for a short time. Didn't happen. When the north tower goes down, there's parts of the exoskeleton still intact & waving in the breeze. Not for long of course because of all that debris at the bottom. The elevator shafts are gone. Pancaking might have finished off the collapse & even exaserbated it, but it didn't start it.
When the planes hit the towers, the fuel tanks ruptured & created a flash fire. The windows were shattered, & most of the burning fuel exited the building. Most of the fuel was gone in seconds & almost all of it gone in minutes. Black smoke denotes inefficient burning & the oven effect doesn't wash because the heat wasn't contained. By blowing out the windows, the floors were fully ventilated. See how hot your oven gets or stays if you leave the door open. Even if the fire storm was hot enough to melt steel (I'm still not convinved), there was lots of cool down time before the collapse. This theory of the jet fuel bringing down the towers started the same day, & has never set right with me. It makes so little sense that it drives the conspiracy theories by giving them credence.
Then there's this collapse of WTC 7. No jet fuel there. Debris? I don't think so. You can see it collapse from the center in. That reeks of implosion from collapse of the elevator shafts. The elevator shaft is always the central structure of any commercial building more than 1 story. The building comes straight down just as if it was a planned demolition, which adds more fodder to the tinfoil hat "inside job" speculators. The only other thing that explains it is shockwave liquifaction from beneath. The tower collapse could easily create that shockwave through the ground. How is that collapse different from the towers themselves?
Concrete is man-made limestone conglomerate. Artificial rock. Shock shatters rock. You can shatter a good size boulder into manageable muck with 2 or 3 sticks of primer (TNT) & a couple of sacks of powder covering it & just sitting on top of the rock & tied into the shot. The explosion of the jet fuel shotgunned out the windows, nullifying a big part of the compression effect. But the initial shock, along with the impact itself would have been enough to send a shockwave through the shafts that multiply in number as you go down, & create an amplified feedback with more than enough reverberation to crack the man-made rock that's hollow, only a couple of feet thick, & carrying a tremendous load. It doesn't have to shatter. It just has to crack & weaken. Gravity does the rest.
Now this is a nice conversation. Civility is so much more pleasant than name calling. Anyway, you're the egghead. Check out the math. I couldn't if I wanted to. I never studied law, judicial or physical. I'm sure there's some string theory that'll prove anything you want. :D
I haven’t seen a lot of films of falling towers. The ones I have seen I just happened to catch on the news or in a movie. I can’t say that I personally have noticed they usually fall from the bottom up or from the top town. Most of the examples I’ve seen have been caused either my deliberate demolition or by seismic activity. In the former case, the collapse is designed and controlled. In the later case the collapse is driven by energetic oscillations that originate at the base of the tower. The twin towers may be an exception. The historical argument which goes, “most buildings don’t fall that way” doesn’t have a lot of validity. Most towers haven’t been penetrated by fully fueled commercial jetliners before collapsing.
In an attempt to remain at my most cautious I will say that pancake models of tower collapse are not physically impossible. Once initiated (i.e. once you drop the upper segment, weighing an eighth of a million tons, of a tower twelve feet onto the lower segment) pancake collapse is entirely powered by gravity and is self-sustaining. Each inelastic collision of upper segment onto next lower floor releases enormous energy; enough, in most cases, to cause the failure the next lower set of supports and continue the collapse. Moreover the energy released increases with each floor. For the mathematical details of one such model see my first post in this thread. This does not mean the twin towers fell in this way. But it does mean that one needs to do a lot more work to eliminate the possibility.
How would one eliminate all pancake models of twin tower collapse?
1. One could study video of the collapse and demonstrate pancaking did not take place; e.g. one might discover, as Hippiefried speculates, that the collapse was from the bottom up instead of from the top down.
2. One might attempt to demonstrate the impossibility of initiating a pancake collapse in the twin towers.
3. One might attempt to argue that in the specific structure of twin towers was such that the energy released by the initial fall of the top segment of the tower onto the lower segment was not sufficient to sustain further collapse.
4. One might propose a different theory that assumes less and explains more.
5. I’m sure I’m leaving out a few other strategies.
I confess, I haven’t studied the video of the TWC collapses frame by frame. Like most people, I’ve just seen them over and over again on the news. So I can only address (1) anecdotally. I can only say that if it’s an illusion they are falling from the top down, then it’s a good illusion.
Hippiefried and others have attempted to eliminate the pancake model of TWC collapse through route (2). The usual argument is that jet fuel doesn’t burn at high enough temperatures to melt steel. My counter is that the 60 tons of fuel carried by each airliner contained the energy equivalent of 900 tons of TNT (that’s just 10% short of the energy released by a kiloton bomb). The heat released by the burning fuel would not all dissipate but would be stored in the concrete and other materials of the breached floors creating an oven. Some have objected the breach floors were open to the wind which would’ve carried away the heat and Hippiefried has also objected that most of the fuel spilled outside the buildings and what remained burned away rapidly. To these objections I have countered that compared to the 300mph winds that are required to carry away the comparatively small amount of heat generated in a jet turbine, the wind blowing through the TWC could not have carried away 357 million BTU’s of heat (the equivalent of 900 tons of TNT). Hippiefried says the fuel was mostly lost and burned away quickly. From what I remember of the video I’ve seen, the fires on the breached floors lasted quite awhile. Perhaps that just what I want to remember. But suppose 99% of the jet fuel was spilled outside the building. That leaves 9 tons of TNT or 3.6 million BTU’s of heat. Depending on its distribution within the materials of the building, that’s still is enough heat to melt steel and crumble concrete into calcium oxides and carbon dioxide gas. I can’t say this is indeed what happened at the WTCs, but it seems to me to be a likely scenario and one that certainly hasn’t been eliminated by the current objections.
It should be clear my study of the WTC collapse is not a very serious one. So perhaps its not surprising I haven’t encounter anyone proposing strategy (3). Strategy (3) would require one to argue from the specific engineering design of the twin towers. Any such argument would be intricate and involve more detail than I would have the time and patience for.
Hippiefried, in proposing his oscillation theory of collapse, has opted for strategy (4). My objection to this theory is that even if we are very generous and assume the planes had a velocity of 500mph when they collided with their respective towers, the energy of impact is relatively small, a half a ton of TNT per impact. Most of this energy was used to penetrate the building and stop the plane. If there were lot’s of energy to spare the planes would’ve burst through the other sides of buildings and fallen to the ground. Any vibration caused by the initial impact would have died out in minutes, unless (and here I’m taking the liberty to modify Hippiefried’s proposal) there was another source of energy driving the vibrations. The only other source I can think of is the wind currents that must’ve been blowing through building from the bottom up. To make this proposal work one would have to show the towers had a design flaw; i.e. a natural resonate frequency and that the chimney currents somehow drove the building to oscillate just at this frequency. My current point of view is: I don’t think this theory assumes less and explains more. That doesn’t mean it isn’t true, but it doesn’t eliminate the pancake model.
:shock: Squeeeeeze me????!!!!!??Quote:
My counter is that the 60 tons of fuel carried by each airliner contained the energy equivalent of 900 tons of TNT (that’s just 10% short of the energy released by a kiloton bomb).
Other way around maybe. If that were the case, we'd be taking down mountains with jet fuel instead of dynamite. Trinitrotoluenol (Al Nobel's weapon to end all wars) is basically just stabilized nitro glycerine. Takes a blasting cap to set it off. A half pound stick primer will take out the side of your house. The cap alone will take your hand off. Think you can do that with less than a gram of kerosene? Methinks it might be time to recheck your sources. TNT is an extremely fast accellerant.
The explosion from the fuel was caused by compression of the tanks just prior to the rupture. The fuel is liquid, so without compression, there's no explosion. It doesn't burn fast enough to explode in the open air. Most of the fuel shotgunned out the windows, but the initial shock could easily rupture the concrete shaft structure. Shock, not heat.
Ah so, Grasshopper! But now we're talking tower segments as opposed to floors. This is where the heat theory really breaks down. In order to cause the floor by floor pancake effect, you have to weaken the anchors all around the building & on the shaft structure. The floors are radial spans. Other than the shaft structure itself, there's no columns inside the building. If heat were the culprit, it would have taken out a couple of floors & only on one side of the building. The wingspan of the 747 is less than half the width of the tower.Quote:
Once initiated (i.e. once you drop the upper segment, weighing an eighth of a million tons, of a tower twelve feet onto the lower segment) pancake collapse is entirely powered by gravity and is self-sustaining.
Now to me, liquifaction makes sense & it's the only explanation I can see for the collapse of the 3rd building. But that said, the beginnings of the tower collapse doesn't have to start at the bottom. It could start at the point of impact. It has to start with the shaft structure though. That's how you pull it straight down from the top. I'm thinking the anchors held better than anyone would have thought. As the central structure collapses, it drags the floors down & they pull the exoskeleton inward. Since the shaft structure is hollow, the rest of it would shatter like an eggshell as all that weight came down pushing from all angles. It'd be like splitting a log with a wedge. The amount of energy released into the ground from the collapse is enormous. I wouldn't know how to do the math on it, but I imagine it was measurable on the richter scale. There's that liquifaction. Enough to shatter any weak point in the 2nd tower, & bring it down the same way, along with the 3rd building that collapsed while the 2nd one was going down. There was no toppling anywhere. The exoskeleton did a good job containing the collapse because the floor anchors held.
Just sowing the seeds of doubt. How'm I doin'? It must be my pyrronistic nature. Is it rubbing off? :D
Exactly, it is in fact explosive…it releases it’s energy quickly. However, one ton of gasoline will release 15 times as much energy as one ton of TNT. Gasoline is extremely energy dense. That’s why it’s a great fuel.Quote:
TNT is an extremely fast accellerant.
An explosion of the right magnitude would’ve dropped the top segment of the building onto the lower segment immediately. But if you got an hour or two to wait around, just one percent [of the fuel] that was in that airliner, will release 357 million BTU’s of heat. Enough to degrade the concrete, buckle and perhaps melt the steel.Quote:
The fuel is liquid, so without compression, there's no explosion. It doesn't burn fast enough to explode in the open air.
The heat of the fuel is ONLY required to degrade the support materials of the breached floors. The fact that those floors were also damaged by the penetration of the plane and the initial shock also helps. Once the top segment begins to fall, nothing can stop it, especially as it gathers up more mass and more speed on the way down. I agree the likelyhood of degrading all the supports [of the breached floors] decreases with amount of fuel that was spilled. I have no actual reported numbers on that. Do we in fact know how much was spilled outside the tower and how much remained inside?Quote:
Ah so, Grasshopper! But now we're talking tower segments as opposed to floors. This is where the heat theory really breaks down. In order to cause the floor by floor pancake effect, you have to weaken the anchors all around the building & on the shaft structure.
I agree that the relative hollowness of the towers is an important feature, it allows for the entire structure to be pulled inward as it falls.Quote:
That's how you pull it straight down from the top. I'm thinking the anchors held better than anyone would have thought. As the central structure collapses, it drags the floors down & they pull the exoskeleton inward. Since the shaft structure is hollow, the rest of it would shatter like an eggshell as all that weight came down pushing from all angles.
In order to release all that energy from a liquid fuel, it needs to be vaporized, aerated, & ignited under contained compression. What happened to the towers was not what happens in the combustion chamber of an internal combustion engine. No compression, no power.
To melt steel, you need sustained heat of nearly 2800 degrees F.
I found this:
Here:Quote:
Jet fuel (refined kerosene) boils at temperatures above 160 degrees Celsius (350 F) and the vapor flashes into flame at 41 degrees Celsius (106 F). In an environment of 1500 degrees F, jet fuel spread thinly on walls, floor, and ceiling would boil off very quickly. If there were sufficient oxygen, it would burn; otherwise it would disperse out the open windows and flame when it met oxygen in the open air -- as was likely happening in the pictures that showed flames shooting from the windows. Some New Yorkers miles distant claimed they smelled the fuel, which would indicate fuel vapors were escaping without being burned.
http://www.public-action.com/911/jmcm/physics_1.html
There's a lot of info in a tongue & cheek look at the jet fuel theory.
Not true. A hurricane lamp that burns a gram of kerosene drawn by a wick from a reservoir at ordinary air pressure will release as much of its energy as a kerosene lamp that burns a gram of kerosene vapor drawn from a pressurized tank. The only difference is the rate of burning and therefore the brightness of the emitted light. If you’ve ever spilled a lit hurricane lamp you may have experienced first hand the fact that kerosene will burn even when not wicked and when not under pressure. Though all and all, it’s a relatively safe fuel; I’m told that decades ago it was used to clean and disinfect old wooden floors in public buildings. It’s true that in the WTC some jet fuel might have spill away without burning, some may have vaporized and escaped as fumes. But 60 tons of jet fuel equates to over one million kilowatt hours of energy. I cannot rule out the possibility that some portion of this enormous store of energy was principally involved in the initial stages of the WTC collapse; not without an account of what happened to all of that store of energy. Even if only one percent of that energy was actually stored in materials of the breached floors as heat, that would be 3.6 billion BTU’s of heat!!! Do you really believe more than 99% of the fuel fell away or evaporated before being consumed by flames? Perhaps you're right, but how would we know? It seems like a lot of stored energy unaccounted for.Quote:
In order to release all that energy from a liquid fuel, it needs to be vaporized, aerated, & ignited under contained compression.
In order to make full use of any liquid fuel, it has to be contained & controlled. Just like your lamp. As long as the rate of fuel consumption is held to a minimum, you get light for a while. If you take that same amount of fuel & light it all at once, it burns up in seconds or minutes & is gone. In order to raise the temperature, you need to add more oxygen than is in the surrounding air. If you want it to explode, you have to contain the pressurized gasses from the burn until they build up enough to rupture the containment. Kerosene burns too cold to accelerate to explosiveness without containment.
In the WTC incident, the only containment was the windows. Once containment was breached (almost immediately) the fuel which was already ignited & expanding, along with most of that theoretically potential stored energy, blew out into the open air & dissipated.
If it takes 60 tons of fuel to drive 4 or 5 jet engines for a few hours, under controlled conditions, where's this stored energy equal to a kiloton TNT explosion, a million KWH, or 3.6 billion BTUs? Answer: The same place it's always been. In a theoretical formula on a piece of paper or a computer screen. There's loads of stored energy everywhere. The whole trick is to get it released efficiently.
:smh I'm not a kid & we're not talking potentials. I was under the impression that this was a discussion of the possibilities & probabilities of what really happened in a real event.
Mostly I agree. Temperature can also be raised without increasing the available oxygen density simply by storing the released heat of the combustion in high heat capacity materials, like brick and concrete.Quote:
In order to make full use of any liquid fuel, it has to be contained & controlled. Just like your lamp. As long as the rate of fuel consumption is held to a minimum, you get light for a while. If you take that same amount of fuel & light it all at once, it burns up in seconds or minutes & is gone. In order to raise the temperature, you need to add more oxygen than is in the surrounding air. If you want it to explode, you have to contain the pressurized gasses from the burn until they build up enough to rupture the containment. Kerosene burns too cold to accelerate to explosiveness without containment.
I simply can’t confirm that. Sixty tons of fuel is a lot of fuel to get rid of. It’s not enough volume to rise to the windows and pour out. As it vaporizes some of it will chemically combine with the oxygen carried by chimney current (referred to in our prior postings) and add its released heat into the atmosphere and into the materials of the breached floors. A lot of the vaporized jet fuel will escape. But do we have any idea of the proportion of the energy that is actually released as heat and the proportion that remains stored in the chemical bonds of the fuel?Quote:
In the WTC incident, the only containment was the windows. Once containment was breached (almost immediately) the fuel which was already ignited & expanding, along with most of that theoretically potential stored energy, blew out into the open air & dissipated.
Actually the answer is that the energy is stored in the chemical bonds of the fuel. The only way to have an inefficient RELEASE of that energy is not to burn all the fuel; spill some or let some boil away…which I believe is your point. [But just in case you’re thinking something else let me remark that if all the fuel is burned (quickly, slowly, under pressure or not) ALL the energy available through oxidation will be released.] I believe your claim is that the release at the twin towers was nearly 100% inefficient. I have reservations about that claim and moreover, I propose that even 99% inefficiency releases enough heat to degrade the structure of the breached floor. On these points we seem now to be repeating ourselves. Let me be the first to admit that I haven’t added anything new to my argument in the last several posts. I’ve just been trying to make my position clear and trying to get clear on your position.Quote:
If it takes 60 tons of fuel to drive 4 or 5 jet engines for a few hours, under controlled conditions, where's this stored energy equal to a kiloton TNT explosion, a million KWH, or 3.6 billion BTUs? Answer: The same place it's always been. In a theoretical formula on a piece of paper or a computer screen. There's loads of stored energy everywhere. The whole trick is to get it released efficiently.
The question is what proportion of the initially available 3.6 billion BTU of potential energy was actually released and what proportion of that was stored as heat in the materials of the building? Was the heat density high enough in key areas to generate temperatures that would degrade the structure of the breached floors? I propose that even if a small fraction of the initially available potential energy was converted and stored as heat, it would have been enough to initiate collapse. That’s why I think proper energy bookkeeping is essential here. But I just don’t know how to verify the alleged and conflicting accounts of various scenarios.Quote:
I'm not a kid & we're not talking potentials. I was under the impression that this was a discussion of the possibilities & probabilities of what really happened in a real event.
Even if I am repeating myself, it is BTW refreshing to have a real and honest discussion on this topic.