> I just wonder how WTC7 collapsed in 5 seconds despite not being hit by any aircraft.
Did you see the video of, say, the Surfside condo collapse? When a skyscraper starts to collapse--and it doesn't really matter all that much how it starts to collapse--it invariably collapses quite quickly and in much the same way.
WTC7 didn't collapse in "5 seconds". The actual observed portion of the collapse took about 9 seconds, and this is a view that only shows about the first ⅓ of the collapse. One of the things that greatly hampers analysis of the WTC7 collapse is there just aren't good views of much of WTC7, and so the full extent of the damage it received from its front-row seat of a collapsing building isn't entirely known.
Did you see the video of, say, the Surfside condo collapse? When a skyscraper starts to collapse--and it doesn't really matter all that much how it starts to collapse--it invariably collapses quite quickly and in much the same way.
WTC7 didn't collapse in "5 seconds". The actual observed portion of the collapse took about 9 seconds, and this is a view that only shows about the first ⅓ of the collapse. One of the things that greatly hampers analysis of the WTC7 collapse is there just aren't good views of much of WTC7, and so the full extent of the damage it received from its front-row seat of a collapsing building isn't entirely known.