... Thus, the impacts were either close to, or well within, the Towers' capacity to absorb them without collapse."

And they didn't collapse from the kinetic impact. Wow.

Cheers,

I found Mr. Brown. He seems to think that the steel melted!

"Dr. Hyman Brown from the WTC construction crew, claims that the buildings collapsed due to fires at 2000F melting the steel (1). He states "What caused the building to collapse is the airplane fuel…burning at 2,000 degrees Fahrenheit. The steel in that five-floor area melts." http://www.septembereleventh.org/newsarchive/2004-11-11-ryan.php

"This building would have stood had a plane or a force caused by a plane smashed into it," he said. He also said that the buildings were designed to withstand 200 mph winds." Prof. Brown

There has been nothing from the now Prof. Brown lately on what he thinks, I suspect that his earlier comments were off the cuff. He was probably astounded that buildings this strong would collapse after a designed for plane impact any more than they would have collapsed in a strong wind and was disparately seeking a logical explanation.

He is not on record for 7 World Trade Center. His email is there in the links, maybe someone might like to ask him for his opinion today?

http://www.colorado.edu/news/experts/results.html?id=ENGINEERING+-+BUILDINGS+AND+INFRASTRUCTURE

http://911research.wtc7.net/disinfo/collapse/meltdown.html

http://www.zoominfo.com/people/Brown_Hyman_112566459.aspx

This thread has turned into a 9/11 bunfight, which I am sure was not Glenn's intention, but insofar as it is now a bunfight, certain things need to be said.

First of all, skeptics need not prove anything. The 9/11 Commission has put forth a theory. The onus falls on the Commission, and its supporters, to defend this theory. Again, skeptics are entitled to nitpick this theory to death without providing any alternative theory. Dat's da way science works.

So let's nitpick.

As for the collapse of towers 1 & 2: The 9/11 Commission has suggested that the massive, steel reinforced cores collapsed into themselves, at freefall speeds, no less. To anyone (with an open mind, that is) who has been in the least educated in fields of structural engineerig, this is absurd. The best analogy I heard was that of a tree collapsing into its own trunk. At near freefall speeds! If you believe this, you will believe anything.

Like, for example, the NIST speculation regarding the collapse of WTC7. No plane hit 7. Rather, the thing just disintegrated some seven hours after having been struck by some falling debris. As others have mentioned, no modern streel-framed structure has ever collapsed in this manner before, even as many steel-framed structures have caught fire in the past. Ever. But it was less that the building collapsed and more the way in which it collapsed, namely, at freefall speeds and with almost perfect symmetry. Pls consider that in order for this to have happened, all structural resistance of the building must have dissipated simultaneously. What -- the fire cooked the building so evenly that every joint, rivet and beam failed at the same time? Again -- this is an absurd proposition.

The irony is that here the government body charged with explaining this sequence -- NIST -- has so far, some six years later, failed to come up with a theory it feels comfortable presenting in the public domain. (A report which was to include detailed finite element modelling of the collapse was supposed to have been published something like a year ago. We are all still waiting...) Yet here we have presumably smart folks sniping at skeptics and hugging the theories of a Commission, (a Commission whose Chair's just levelled the charge of obstruction against the government, as per Glenn's original post), as if to save themselves from disappearing down some rabbit hole.

I stated, above, "the 47 massive, vertical steel columns that made up about 40% of the area within the core of each tower." What I meant was that the steel core made up 40% of the area within each tower.

Leastwise, the pictures all show the buildings collapsing floor by floor from the top. Demolitions don't.

There were people in the sublevels (below the basements) of the towers reporting explosions in the base of the towers. There was an eyewitness who reported having passed a huge, steel door on his way out of the basement that was bent, deformed and hanging off it's hinges. There was another man, a maintenance worker, who was severely burned by what he reported as an explosion in the basement of one of the towers.

Given the amount of support I mentioned was being provided by the massive, vertical steel columns within the cores of each tower, one would expect each floor would meet with a certain amount of resistance as it collapsed. As Bill Owen has pointed out, this didn't happen. Using the North Tower as an example, even if we were to allow a half a second for each floor to meet and then push past this resistance, and assuming the collapse started at the lowest floor involved in the point of impact (the 94th floor), it would've taken the North Tower 47 seconds to collapse. Even if we were to allow for even less time to elapse as the collapse progressed further (allowing for the amount of weight and force involved) and calculate that, halfway through the collapse, it would occur at a faster rate, and allow for 1/4 second for each floor to meet and push past the resistance, it would've taken 35.25 seconds for the tower to collapse. As has been pointed out, the collapse actually occurred in approximately 12.74 seconds. This tells us that there was virtually NO resistance.

Also, as pointed out in the source provided in my previous post, the towers were originally designed to comply with the 1968 NYC fire code rating 1A. This requires 4 hours of fire resistance for columns and 3 for floor assemblies. The buildings received a rating of 1B (3 hours and 2 hours respectively, because of the lack of a sprinkler system.) These are the requirements the steel used in the construction must meet BEFORE fireproofing is applied, so the talk about the fireproofing being knocked off by the impact doesn't figure in.

The South Tower collapsed 56 minutes after impact. The North Tower collapsed 102 minutes after impact.