I just keep coming back to WTC 7 as being the weakest link in the official story of what happened on 9/11. I can't help but feel that if enough people hammer and hammer on it, that eventually the whole official story will crumble. What will happen after that is anyone's guess, but I think it's safe to assume things here in the US would never be the same again.
I watched that clip about ten times. There is FIRE coming OUT OF THE WINDOWS on TOWER 7. Watch and see for yourself. No "optical illusion" there, it's plain as day to see.
It could very well be an optical illusion. I took that image and flipped it over to look at it from the same perspective as the video. It seems that the camera angle is just right to just see a tiny bit of the far end of 7 and then a good portion of the north tower.