Here's a video I think very few people have seen. It reveals something fascinating. The strip in the middle is frozen just before impact. Everything above and below it is live. Watch the South Tower's edge slide back and forth against it. That's roughly 22 inches of sway at the roof, per NIST, and it stayed up. That's a credit to the people who designed it. They planned for a Boeing 707. What hit it was a bigger, heavier 767 doing roughly 545 mph. NIST measured the sway from impact video and found the building's rhythm barely changed, meaning the hit didn't appreciably affect its overall stiffness. So it wasn't the impact that brought the towers down. And it certainly wasn't nonexistent explosives. It was the fire. The crash stripped fireproofing off the steel, the fires weakened it, sagging floors pulled the outer columns inward until they buckled, and then thousands of tons of building came down on floors that were never built to stop it. The South Tower fell 56 minutes after this clip.