Is there anything inexplicable about how the WTC Twin Towers collapsed? > **Possible Duplicate:** > On 9/11, was Building 7 destroyed in a controlled explosion? Having just watched the movie Zeitgeist, I'm a bit unsettled because I don't know how to refute the idea that the Twin Towers collapsed in a way that's inconsistent with known physics. Specifically it bothers me that the buildings had steel superstructures which it's claimed couldn't possibly have gotten hot enough to melt. If that's so, why did they not remain standing even when the supported floors collapsed? ### NEXT DAY... I don't have the rep to delete my own question here. But this other question, although primarily about Building 7, has very good answers covering everything I wanted to know. My apologies if anyone feels I have wasted their time asking again.

Jeez... You might check out the James Randi forum where the refutations of the "truthers" are both long and detailed... Check out the "conspiracy theories" threads.

However... One need not go into such detail. It is not necessary for the steel support structures to "melt". Only that they be weakened. And that's precisely what happened. They became too weak to support the thirty-odd stories of structure above them, and they collapsed. The kinetic energy of the falling 30-stories atop the weakened section was enormous...

Consider this. In the years following 9/11, I am familiar with two incidents where gasoline tanker-trucks were involved in accidents on bridges and caught fire. The fire,fed by thousands of gallons of gasoline, got very hot. Both bridges collapsed.

No "melting", just weakening of the steel to the point it could no longer hold the structure up.