Saturday, February 04, 2006

Did a controlled demolition bring down the towers?

Last month, a friend directed me to a video claiming that the September 11th attacks were a masssive conspiracy by the U.S. government. After watching it, I sent her the well-known Popular Mechanics arcticle that deals with most of these claims.

Later that day, she responded by sending me a link to the updated version (linked above) which includes a calculation showing that the towers came down at nearly free fall speed. She said she had checked with an engineering student at Madison, and he had confirmed that if the towers had been pancaking, as the PM article claimed, the would have taken longer to fall.

I then gave something of a lecture on the impossibility of concealing such a conspiracy, and the absurdity of the idea that the whole engineering community would be silent if the PM article was wrong about the pancaking. She replied that people are afraid, with all criticism of Bush being considered unpatriotic. I wasn't all that concerned with the data at that point, but I did say that the pancaking might be accounted for in the ~1s longer it took above free fall (a figure we seemed to agree on).

At the end, I demanded to see the engineering student's calculations and see his data sources. I was ready to get some engineering textbooks and learn, learn the relevant material, and do the equations myself.

After telling her this in a somewhat emotional burst, I paused to think about it for a moment: how fast did the towers really fall? To answer this question, I drew upon a skill I had learned in high school physics: the art of making marks on a video screen.

In my first couple analysis, I used pencil and ruler. My efforts are recreated below using Microsoft's paint program (note that I had to put these into jpg format to get blogger to take them, so they're somewhat fuzzier than my originals, but they should be clear enough when you click for the full versions):


The first picture shows a line at the bottom of the smoke cloud, a line at the burning part of the other tower (to compensate for camera movement) and a line across one tower to establish a scale. This scale would be 91 pixels:64 meters (at least it's 91 pixels on my computer). The 64 meter figure for the width of the tower may be found here:

http://www.tms.org/pubs/journals/JOM/0112/Eagar/Eagar-0112.html

In the second picture, we see that the camera has followed the fall 131 pixels down, while the bottom of the dust cloud is 10 pixels higher on the screen. This means the tower has fallen 121 pixels, or ~85.1m.

As best I can tell, the number after the colon on the timer is 30ths of a second. Put in decimal form, we are 5.73s in to the fall. From all this, we have

85.1m = 1/2 * a * (5.73s)^2

a = 2 * 85.1m / [(5.73s)^2] = 5.18m/s^2

(5.18m/s^2) / (9.8m/s^2) * 100% = 52.8% of freefall acceleration

When I attacked this with ruler and pencil, I got answers from 53% to 56%. I suspect that this is perfectly consistent with pancaking, though I only sent these screen shots to my friend today, and she hasn't found out from the engineer how long pancaking should have taken. This is something of an ongoing story, I may update this if the situation warrants it.

7 comments:

Francois Tremblay said...

To me no possible scenario makes any sense. It can't possibly have been only planes crashing into the buildings. It also can't possibly have been a vast government conspiracy. I really have no idea what happened, and the government made sure that no one could ever know.

Anonymous said...

My biggest objection to this conspiracy theory is that if the planes that took off and subsequently disappeared were not the same as the planes that hit the towers and the Pentagon, what happened to those planes that took off and are still unaccounted for, with all the people who are known to have disappeared and who were recorded as passengers on those planes?

Francois Tremblay said...

"if the planes that took off and subsequently disappeared were not the same as the planes that hit the towers and the Pentagon"

What ? I've never heard about that. What evidence is there for that position ?

Aaron Kinney said...

Good post Hallq. I really do hope you follow up on this soon and post more about it, as I have a friend who recently began trying to convince me of this whole conspiracy idea.

Hey, I hate government asm uch as the next guy. I hate Bush, and if he got impeached or imprisoned I would literally cream my pants for a week straight. But lets be realistic here. Extraordinary claims require extraordinary evidence.

So far the evidence has been wanting to say the least.

To top it off, while I am no expert at demolitions and engineering, I do happen to be a HUGE aviation buff, and I fond various conspiracy theory websites that posted horibly incorrect information on the Boeing 707 (which the WTC was designed to take a hit from) and I pulled out my handy old Encyclopedia of civil Aircraft and refuted their baloney. Basically, they quoted the wrong maximum speed, the wrong lb/thrust amounts for the 707 engines (in fact they claimed the wrong engine model # entirely; the conspiracists cite specs for an engine that didnt even EXIST whent he WTC was designed) and therefore they came up with horribly innacurrate thrust to weight ratios. It was embarassing because I am an amateur (but knowledgable) aviation buff that discovered their sloppy mistakes.

Anyway, yea. conspiracies like this are silly.

SocialScientist777 said...

I am an Australian so I cannot claim to know the American people well, but I find it hard to believe that a government that promotes Capitalism would blow up the symbol of capitalism along with people who were leading economic experts. It is a bit far fetched for me.

King Aardvark said...

I'm a structural engineer, and we had an expert come to my university to do a lecture of the report of the findings for the WTC collapse (he was actually one of the analysts). The heat from the fire didn't melt the steel, but sufficiently weakened it so that it failed. The expert said it was from pancaking. Given that he was Canadian, not American, I'm pretty sure he wasn't covering up anything on behalf of Bush.

bookunky said...

What seems the oddest to me is that WTC7, a 47-story structure which was NOT hit by aircraft, also fell after burning at a fairly low level for a relatively short period of time. The official investigation group never did come up with an explanation for why this building fell. Possibly interesting is that among the building's occupants were the IRS, SEC and other government offices. Most damningly, however, all the evidence from these investigations was destroyed.

Also, why did Air Force One not scramble right away? Why was the attack on the Pentagon allowed to take place after two other planes had hit targets?

Clearly the idea that the planes were empty drones and crackpot thinking along those lines are nonsense. However, there were a lot of exceedingly strange things that happened that day, some of which suggest some people in the government were colluding at some level. I don't know what happened, and I suspect we never will. I agree with francois that no possible scenario makes sense.