Looking at the upper right-hand corner of the building we see a rapid series of small explosions travelling upward just as the building itself begins to fall.
The claim here is that the "explosions" occurred as the building fell. The implication is they happened at the same time, but is that really true? Well, no -- not even close. Let’s start with this image, and take a look at the top of the building, where you’ll see both penthouses.
Now let’s look at some stills from the original Naudet footage, apparently used as a basis for the “squibs” video.
The stills begin here, more or less, but you’ll notice there’s a problem on the roof: the larger left-hand penthouse has already collapsed. The building is falling before the video even starts.
Note also that from the “squibs” photo and video you might think there are four or five of them all appearing within a fraction of a second of each other. However, in the stills you can see there’s already one large artefact at the base of the line, one small one at the top -- the others don’t appear until later.
Compare that picture with this one, and you’ll see now the left edge of the penthouse on the WTC7 roof has disappeared as it’s falling. The left hand top edge of the building is kinking, too, but there’s no sign of the “squibs” yet.
The picture below shows the “squibs” starting to appear. The first penthouse has fallen, though, and only the aerials on the roof remain of the second. So with floors beginning to collapse and the building deforming it really shouldn’t be surprising if there’s some signs elsewhere in the building.
This looks pretty much like the usual “squibs” picture, but clearly it’s occurring way after the collapse has started. By this stage the second penthouse has almost vanished, and the building is continuing to deform with a kink in the left corner.
If these artefacts were the result of demolition, then you might expect them to appear before the building begins to collapse, but this clearly doesn’t happen. They appear at least three quarters of a second after one penthouse falls, and an undetermined time after the first disappears (because it’s not shown in the video). And they appear as the building is deforming, which you might expect to cause (for example) some windows to shatter. On the timing argument, then, the “squibs” look more like the result of a collapse already progressing, than something used to initiate it.
Some people still say otherwise. Here’s a comment from Steve Jones:
Horizontal puffs of smoke and debris are observed emerging from WTC-7 on upper floors, in regular sequence, just as the building starts to collapse. (The reader may wish to view the close-up video clip again.) The upper floors have not moved relative to one another yet, as one can verify from the videos.
[Draft 3.1 as of 24th December 2005]
So the puffs of smoke and debris appear when “the upper floors have not moved relative to one another”? If you don’t find the stills convincing, then let’s review that by checking out the Naudet footage itself. You’ll see in reality there’s considerable movement and sagging across the whole building before the “squibs” appear, and remember this footage still doesn’t cover the beginning of the collapse (download here if the video doesn’t play for you).