This Is the Kind of Nonsense the Deniers Come Up With
Watch the video (it's only seven seconds long). Notice how the bridge appears to be moving in the background? Well, of course, it's just an artifact of the camera panning back at the same time as the helicopter doing the videotaping is moving to the viewer's left.
But that's not what the Deniers think. They see something very suspicious, possibly the smoking gun!
Of course, what they're really observing is a very common phenomenon that I first noticed as a child on long car trips. When we'd see a water tower in the distance, especially if there was a hill in between, it always seemed like the water tower was moving parallel to us. This is because the angle of view of something close to you changes more rapidly than the angle of view of something far away.
Update: I love one of the comments left on that YouTube video:
Maybe the sooper-nano-mini-nuklear thermite bomb was moving the bridge, or Larry Silverstein was "pulling it"... lo