the conspirators would have wanted take advantage of the confusion during the attacks on WTC-1 and WTC-2 and to vacate the area ASAP) but the fact of damage resulting from the collapse of WTC-1 severing seven columns of WTC-7 only adds further plausibility to the theory that ultimately fire caused a cascade failure of the structural steel supporting the building. Steel melts at around 2950 degrees F but is actually hot rolled at around 1400 degrees F. A sustained fire from burning diesel fuel would have been sufficient to raise the temperature of the steel columns on the lower floors to the point where they could no longer sustain the weight of the entire structure above them. The massive steel failures along with many events during the collapse would have reverberated throughout the building creating explosion-like sounds. However they are not evidence of any deliberate detonations. The forensic scientists and engineers who studied the problem are in a far better position to know what likely happened than armchair spy novel enthusiasts or those with political agendas are to guess about failure of technology they do not understand. BTW, having worked in both the steel and construction industry and seen probably about a million tons of structural steel made from iron ore, coal, and limestone through to fabricated steel construction shipped to building sites, I find the official explanation entirely plausible in light of the facts, the conspiracy theory entirely implausible. Comment number 81. "A combination of an uncontrolled fire and