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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?


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.

  • According to many engineers, there are many inexplicable things about the collapse of WTC. See the answer I posted here: skeptics.stackexchange.com/a/31144/1792 Commented Dec 18, 2015 at 1:45
  • "Specifically it bothers me that the buildings had steel superstructures which it's claimed couldn't possibly have gotten hot enough to melt." - it shouldn't bother you, because the explanation does not involve the structures melting. Conspiracy claims are often based entirely on knocking down a strawman of their own construction. The 9/11 theories are especially tedious because one usually has to explain that no one is claiming that the impossible thing they are refuting ever happened. Commented Oct 7, 2016 at 13:29
  • @Andrew: Christian's point about blacksmiths did it for me. I guess in retrospect it should have been obvious, but I simply never thought in terms of those steel superstructures being weakened / softened by heat even though they might have been nowhere near hot enough to actually melt. Commented Oct 7, 2016 at 13:38
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    Immediately after it all happened, I looked at spectacular claim after spectacular claim, thinking "Holy crap. This is HUGE!" My perspective comes after countless hours tracking these things down and finding nothing to them. My strawman comment was intended to make all that wasted time on my part helpful to someone else by maybe saving them some time before they go looking into whether something is possible or not, when that thing was never even claimed to have happened. Since you posted this years ago, I'm sure you've noticed how often completely debunked claims get recycled. Commented Oct 7, 2016 at 13:42

2 Answers 2


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.

  • 3
    Could you provide a reference to one (or both) of those incidents? E.g. the place and date, a news or accident report.
    – ChrisW
    Commented Sep 1, 2014 at 20:00
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    One such incident happened on the MacArthur Maze in Oakland in 2007: sfgate.com/bayarea/article/… Commented Jun 16, 2015 at 22:00

Steel doesn't have to melt to become weaker. Blacksmiths changed the shape of steel for centuries without melting it. Brian Dunning has a good explanation of the process.

In general, you also have to understand that reality is complicated. If you investigate any process detailed enough then you will find stuff that you don't understand. In science you can repeat experiments and isolate factors till you understand the process.

In historic events you usually don't understand processes in the same detail.

Even if you find something that you don't understand that doesn't mean that a conspiracy exists. It just means that you lack understanding.


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