Why did the buildings collapse in less than 12 seconds?
I’m won’t talk about mass, velocity, energy, and temperatures. I’ll just note that the collapse starts 16 seconds into the video, is still going at 26 seconds in (when something dropped from the roof would hit the ground), and at 28 seconds (when you say the collapse was complete), and keeps going until well into the 40’s. You don’t need physics, just a little arithmetic. 46 seconds, when it is basically fallen down, minus 16 seconds, when it starts to collapse, is not 12 seconds, it is 30 seconds.
The tower is already collapsing as the video begins. The first debris is hitting the ground the ground just after 12 seconds, and the buildings are quite obviously not done collapsing at that point.
Starts to collapse at 2 seconds, last parts still falling when the video cuts off at 40 seconds. 40 seconds minus 2 seconds is not 12 seconds. The last part of the core falls at 31 seconds into the collapse.
Collapse begins at 16 seconds, continues until after 50 seconds, with the core seen falling at 48 seconds, corresponding exactly with #2.
This video shows the central core still standing most clearly. The tallest part of it is about 60 stories up.
Not even the external walls collapsed in 12 seconds in any video.
Why did WTC7 collapse if it wasn’t hit by a plane?
Look at video #3 in particular. You will notice WTC 7 on the left. You will also notice multi-ton pieces of steel raining on it. That tends to interfere with the structural integrity of a building.
At about 14 seconds in you will see a very large piece of the north tower fall into the front of WTC 7.
You will see a large amount of smoke coming from most of the south side of the building, which is also extensively damaged.
In short: WTC7 fell down because a 110 story building fell on it, and it caught fire, lost structural integrity, and failed.
All the common claims about this building prove to be nonsense. It was not the only other building to collapse. It did not suffer only minor damage. It did not collapse in 6 seconds, or fall straight down “into its own footprint”. “Pull it” is not a synonym for imploding a building anywhere on the planet. So on and so forth. It fell down because of a combination of structural damage, and further weakening due to fire.
(Why is it that nobody seems to wonder why the Mariott hotel, which had been 22 stories tall, all but disappeared when the tower fell on it?)
So why can’t we be told the tons of steel and concrete on every floor and basement level?
Just go get the building specs from somewhere. As I recall the towers had about 96,000,000 kg of structural steel each. Divide by the number of floors, including the basement levels, and you get something like 400 tons per floor, but heavier at the bottom than at the top, and heavier on the floors with beams instead of trusses.
There were also hundreds of tons of concrete per floor.
What this has to do with anything I don’t know.
The fact that the structural engineers won’t specify the tons of steel on the floors where the planes hit is pretty damn peculiar.
Who asked them to do this, and what was their answer?