Twenty-five years after the September 11 attacks, conspiracy theories about the World Trade Center’s collapse still circulate — but as Popular Mechanics reports in a piece revisiting its long-running fact-check of the attacks, the physics never supported the “controlled demolition” claim truthers keep repeating.
Steel didn’t need to melt to fail
Jet fuel burns at 800 to 1,500 degrees Fahrenheit, well short of steel’s 2,750-degree melting point — a gap truthers cite as proof of planted explosives. But structural steel doesn’t need to melt to give way. “Steel loses about 50 percent of its strength at 1,100 degrees,” notes AISC senior engineer Farid Alfawakhiri, and the fires were fed for hours by furniture, paper, and diesel long after the jet fuel itself burned off.
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Other claims fall apart under the same scrutiny: seismologist Arthur Lerner-Lam called the “seismic spike” theory “categorically incorrect,” the dust clouds seen during collapse were just air and pulverized concrete ejected by pancaking floors, and the National Institute of Standards and Technology traced WTC 7’s collapse to undocumented debris damage and an unusual column design — not hidden charges.
Two decades of independent engineering analysis keep landing on the same answer: fire and structural damage, not bombs, brought the towers down.
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