Monday, May 22, 2006

Now emit your derisive laughter

Misery of constipation today. Last time I went was Tuesday.

Geek Girl recently supplied a bunch of links explaining the Twin Towers collapses on 9/11. This post looks at just one link she supplied, in which Scientific American reports on an MIT group's opinion.
The main culprits in bringing the famously lofty buildings down, they concluded, were the two intensely hot infernos that erupted when tens of thousands of gallons of aviation fuel spilled from the doomed airliners. Once high temperatures weakened the towers' supporting steel structures, it was only a matter of time until the mass of the stories above initiated a rapid-sequence "pancaking" phenomena in which floor after floor was instantly crushed and then sent into near free fall to the ground below.

According to the report of he 9/11 Commission, "At 9:58:59, the South Tower collapsed in ten seconds." I've seen the video, and while it may be a tad longer than 10 seconds, it's less than 11.

The towers were 1350 and 1360 feet tall. So let's start by using our trusty free-fall equation to see how long it should take an object to free-fall from the towers' former height.

Distance = 1/2 x Gravity x Time(squared)


Time(squared) = (2 x Distance) / Gravity

Time(squared) = 2710 / 32 = 84.7

Time = 9.2

So our equation tells us that it will take 9.2 seconds to free-fall to the ground from the towers' former height.

Using our simpler equation, V = GT, we can see that at 9.2 seconds, in order to reach the ground in 9.2 seconds, the free-falling object's velocity must be about 295 ft/sec, which is just over 200 mph.

But that can only occur in a vacuum.

Since the WTC was at sea level, in Earth's atmosphere, you might be able to imagine how much air resistance that represents. (Think about putting your arm out the window of a car moving half that fast!) Most free-falling objects would reach their terminal velocity long before they reached 200 mph. For example, the commonly-accepted terminal velocity of a free-falling human is around 120 mph. The terminal velocity of a free-falling cat is around 60 mph. (source)

Therefore, air resistance alone will make it take longer than 10 seconds for gravity to pull an object to the ground from the towers' former height.

I didn't write the above italic section, some scientists did.

What this means is that the buildings appear to fall with almost nothing in their way to slow them down. Unless you buy the explanation that the towers had begun collapsing internally before the visual 10-second event.

We have video of an airliner hitting. The huge fireball of fuel explodes mostly OUTSIDE the building. Nonetheless, let's assume that intense fires attacked the four main central supports. Aviation fuel burns at about 1200 degrees F I think and steel melts at 2700 degrees F I think (Feel free to check me on that). To my knowledge no steel-frame building has ever collapsed from fire, even fires lasting many hours. We might say that the twins towers and WTC 7 were of special construction. Recall how long it took between the impacts of the planes and the tower collapses. 110 minutes and 47 minutes. The second tower struck collapsed first, which is unexpected if fire weakened the supports and caused the collapses. The idea that the supports didn't melt, but just weakened, has a high hurdle.

The scientists I quoted above put it this way in a press release hampered by lots of useless political rhetoric:

Since the melting point of steel is about 2,700°F, the temperature of jet fuel fires does not exceed 1,800°F under optimal conditions, and UL certified the steel used to 2,000°F for six hours, the buildings cannot have collapsed due to heat from the fires. How is this possible?

Recall also the photos of a live woman, a blond, squatting, then standing, in the gash of the impact zone. How hot was it there?

The main culprits [...] were the two intensely hot infernos...

Then we get to the pancaking. which floor after floor was instantly crushed and then sent into near free fall...

It's important that they say "instantly" and "free fall" because the video of WTC 1 and 2 collapsing tend to show that nothing obstructed or delayed the top floors on the way down.

If the pancaking happened, would we not expect some slight delay as each floor struck the one below? Some puffs of debris and smoke?

And how about the huge central support pillars (unmelted and unweakened, certainly) of the lower floors? As the pancake hit them, would they not tend to delay the collapse? Would these huge supports not tend to jut out of the rubble? And why did they fail with such precision, allowing the towers to fall straight down and not topple?

Has anyone that you know of ever tried to model this pancaking effect with a large mockup of the towers, to time how long it takes for the top floor to reach the ground?

No, I don't think the experts and publishers are all part of some conspiracy of lies. I think they're groping for an explanation that doesn't stray into the realm of the unthinkable.

And no, I haven't made up my mind. For nearly five years I was content with the prevailing theory, and argued in favor of it. But now I have questions.
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