On this fifth anniversary of the World Trade Center attack, the talk shows are still full of the conspiracy theorists. Although I have tackled the subject before, CUUMBAYA: 9/11 Conspiracies I thought I would take one more stab at getting those who still believe in those conspiracies to see reason.
The central issue is “Would the buildings really have collapsed in the manner we all witnessed?” All else hinges on this; if the buildings really were brought down by the aircraft that hit them rather than by demolition charges, all the other silly claims fall like the buildings themselves did. As all the explanations as to why they couldn’t have been brought down in the manner explained by the 9/11 commission are based on misunderstandings of physics and construction techniques, I thought I’d try to explain it in lay terms. Disclaimer: I am not a working engineer, but I did start in engineering at Purdue before changing to another trade- I feel that may be an advantage as unlike a graduate engineer, I still speak English rather than technobabble.
Most materials are much stronger under tension (pulling on it, like a rope) or compression (just what it sounds like) than any other type of stress. For example, an arrow is strong enough under compression to punch all the way through a large animal like a deer- but has so little strength under a bending load that you can easily bend and break it with your bare hands. In fact, the impact energy that arrow shaft withstands is probably greater than your weight, unless you’re as fat as I am. So could we use an arrow as the shaft of a bar stool?
No- because that arrow is only so strong when all the forces acting on it are perfectly aligned along the shaft, as in flight. In fact, even then if it doesn’t hit straight, it will shatter- ask any bow hunter. There is no possibility that you could sit on it without causing it to bend, which will cause it to shatter. Suppose we were to use a dozen arrow shafts, spaced evenly, so that the stool resembles a bird cage, making it twelve times as strong- would that work? No- strength wasn’t the issue in the first place; bending was. Each of those twelve shafts would be just as likely to bend and break as a single shaft would; there is nothing to prevent this flexing. Now suppose we put several shelves inside the birdcage, rigidly attached to the arrow shafts- they are no longer permitted to flex or bend, and we now have an enormously strong, lightweight stool. This is how the Trade Center towers were built.
Suppose while you’re sitting on the stool somebody kicks it and breaks some of those shafts- does your stool break in half and fall over to the broken side? No- because those rigid shelves prevent the shafts from bending, so the force is distributed to the remaining shafts... but the stress on them is enormous. Now break one of those shelves- what happens? The remaining shafts will instantly shatter at the point where they are now allowed to flex- it will happen so fast that your butt will still be centered over the base. There is simply no time for the weight to fall over sideways; the shafts will go with explosive force and you’ll fall vertically.
There is actually an experiment you can do at home to demonstrate this phenomenon; it requires an empty beer can and two pencils. Stand the can up on end, kneel down, and place one foot on the can. You can put quite a bit of weight on it- in fact, if you use two people (one to steady the other) the can will support the weight of a small adult... as long as that weight is PERFECTLY centered. Now reach down with the pencils and poke both sides of the can. (we poke both sides so that the metal will bend rather than pushing the can sideways) The can will instantly collapse, completely vertically, leaving a flat disk! This is also, by the way, what happened to the plane that struck the Pentagon, and why there is such a small hole- an airplane is a nearly empty hollow aluminum tube, just like that beer can, 99% air.
But back to the building. I can hear the conspiracy nuts now- “Yes, yes, I get it- the floors of the Tower were like the shelves in your bar stool; once one or two went, the structural members shattered and the towers dropped vertically... but it’s a scientific fact that jet fuel does not burn hot enough to have melted those floors! get around that one, smart guy!” Never- with the possible exception of Paris Hilton’s attempt to prove herself an actress- has so much bandwidth been spent trying to prove a non-issue. Nobody ever claimed the floors melted! Metal begins to loose strength at temperatures far below their melting point; jet fuel burns at a temperature high enough to weaken structural steel by nearly half- but the real damage was done by temperatures even lower than that. Hot metal expands- look at any steel highway bridge and you’ll find it sits on rollers or pivots, to allow for several inches of expansion; you’ll also find expansion joints where the steel meets the road, and in-between two steel sections... and that’s just for a hot summer day! At hundreds of degrees, those floors would have expanded a couple feet or more, and probably twisted and bowed as well- instead of preventing the structural shafts from flexing, they were introducing flex where none had been before, while simultaneously those structural members were carrying a greater load than they had been designed for. Of course they went bang- the forces concentrated on those points were greater than the energy contained in the demolition charges normally used to raze a building.
“But look at the cleanup,” the conspiracy nuts say, “weeks later, girders pulled from the hole were still cherry-red and dripping! Jet fuel couldn’t have burned hot enough for them to still be cherry weeks later; it must have been thermite charges used to melt the floors!” As I said before, the jet fuel didn’t melt the floors; in fact, it would have burned itself out within minutes- the fuel merely served as lighter fluid. And yes, thermite could have melted the girders- but a thermite charge burns out in seconds, perhaps minutes if it were a really big one. For the steel to still be hot weeks later merely proves that the fire was still raging under the rubble! Those building were filled with things that are not normally particularly flammable, but if adequately fueled would have burned long and hot- and adequate fuel there was in abundance. The many lower levels of the building contained many machines with flammable fuels and greases; large gas and diesel tanks for emergency generators; natural gas lines- and, of course, a hundred stories of carpets, paneling, and furniture. There are coal-mine fires that burned for decades underground, and a used tire fire burned for nine months - these fires are nothing in comparison.
So come on, people, do a little research before you call the talk shows or write your chicken-little blogs or- God save the mark!- teach a college class . The Dixie Chicks are embarrassed that Bush is from Texas? I’m embarrassed that a third of my countrymen can swallow a camel of a conspiracy theory and strain at a gnat of logic.