Physics question about WTC towers on September 11th?

Heating of the beams caused thermal expansion and buckling.

And what else do you expect besides straight-down collapse. Do you seriously think the tower is going to tip over or something like that. Imagine for a second the amount of torque it would take to make the building tip over (or even to make the top segment tip over). No material known to man could do that. It's going to go straight down.

The government report by NIST shows inward buckling of the vertical beams in the vicinity of the impact just before the buildings collapsed. The beams buckled because the airplane impact dislodged fireproofing that surrounded the beams, increasing their susceptibility to the heat of the fire. NIST concluded that once the beams buckled, the floors above the impact tilted as one big block and collapsed. The structure was not designed to hold that much added unsupported weight, and so the whole building just pancaked straight down.

Pictures clearly show the top of each tower falling with a distinct tilt, consistent with the buckling of the vertical support beams, which should not occur evenly all around. A controlled collapse should have caused the upper part of the building to fall without tilt.

Bottom line is that there isn't really any reason to invoke an intentional controlled collapse to explain what happened. IMHO, if the WTC collapse was indeed intentionally created by planted explosives, the perpetrators are the best secret-keepers in history. There is always somebody blowing the whistle when the U.S. government does seriously bad stuff. See for example the Pentagon papers, the Watergate cover-up, the lead-up to the Iraq war, Abu Ghraib prison, etc.

Robito has an excellent answer, among other. I'll just add that there's video of Bin Laden discussing what he thought would happen. He actually agreed with you, based on his experience in the construction industry. He expected that the "best case scenario", in his warped view, was the distruction of the part of the towers above the airplane strikes with the remnants of the building falling down below. For the reasons others have explained better than I can, he was mistaken and the towers collapsed in their entirety in largely a pancake style.

I did, by the way, see quite a few beems a decent distance away from the collapse in various conditions when I went to see it in October of 2001. They hadn't really cleaned anything up yet at that point, they were still working on recovering of bodies.

The beams were designed to support the weight above them. When weakened by heat and damage, they could no longer do that. Once the mass above the damage started moving, nothing was going to stop it until the material below as solid. Since there was nothing to cause the mass to move much sideways, it was going to drop straight down.

If the steel were solid and the idiocy about cutting charges were carried out, there would be so many charges and interconnect cord they would be totally obvious and THEY would be damaged by the fire. And if you watch the available videos and somehow imagine that those wobbling planes hit exactly where the charges were planted, you don't have any idea of what it is like to fly a plane over a heated city.

This whole theory is so full of holes, those of us who understand the forces involved have trouble believing that people can be so stupid as to believe it.

Despite what you have scene in the loose change video steel begins to weaken at a much lower temperature than it melts. Once the steel heats up it is weakened, it does not have to melt to fail, a weakened beam will bend due to a load acting on it (like a tower).

Before you make an outrageous claim like this take an engineering class or material science class, they have all the answers.

The engineers of the towers discussed this at length.

http://www.pbs.org/wgbh/nova/transcripts/2907_wtc....