Because 'we all know that no plane could have taken down those towers.'
Well, its true. You may not like it, but it really is true that no jet fuel burns hot enough to weaken the support core of a skyscraper which was actually designed, being so tall and everything, to withstand a full-on impact from a Boeing 747. Hell, the cheif architect said so, I'm inclined to believe the man who actually drew the damn plans.
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The world trade center was started to be constructed in 1969/70. No one ever thought a terrorist would use an airplane to crash into a building. During that time all that happened was planes being hijacked and demaned ransom and to free these people demands. The garage area on the other hand the engineers made sure to reinforce it with concrete. Which is a good thing because that car bomb that went off in 1993 did a lot of damage down there.
There's no way in hell that you could design a skyscraper that would with stand a missle which a 767 (not 747) would be without it being insanely expensive (especially considering NO ONE WAS THINKING THAT THERE WOULD BE A MISSLEL ATTACK ON THE MAINLAND U.S. some CRAZY DERANGED person would FLY A PLANE INTO IT) for an extended period of time. A 767 is has a wide body and much a wider than a 747. Also the 767 has more fuel than a 747. Before I get to the fuel thing lets stay on the steel part.
WTC had many steel beams supporting it. For an illustration of what happened (this is a fun activity for the kids so let's get the kiddies involved) get a bag of uncooked spaghetti noodles. If you put those noodles in a firm foundation (where they can stand upwards) they can hold a heavy book up (a dictionary works very well). Let's say that you get a couple of those noodles wet or some of them break. They can still hold that dictionary up pretty well. The problem is once you get a good amount of them to be compromised they will no longer be able to safely hold up the dictionary.
Inside the building nothing should even be catching on fire at 1000 F. There was nothing prepared to withstand that temperature let alone Airplane fuel which burns at 2000 F. There's nothing that can fire proof against that except ceramic tiles. Which if you look at any space shuttle you see that it has ceramic tiles on the bottom. The reason is because it reaches tempatures of an excess 4000 F.
The initial impact did not bring the buidling down alone. The initial impact compromised along with the floors collasping it and then the fires burning as well.
You named dropped so I'll name drop as well (well actually you just stated without backing which is expected) Hy Brown. Oh wait Popular Mechanics. Guess what! They put the debunking the 911 myths online. You know why because of leptons that believe myths and that wouldn't buy popular mechanics. http://www.popularmechanics.com/technology/military_law/1227842.html
Yeah I would believe them yet I also believe in logic.
On a final note, as you've 'claimed' to know most people from the states don't know this and that UBL was an Engineer. Most Engineers know that the integrity of steel once it gets heated to a certain point becomes compromised and basically useless.
Several of his top commanders were explosives experts. One of whom was trained in the U.K. as one.
People that believe in 911 myths should also be put next those few that hold onto that the earth is flat (aka flat earthers) and that category title would be leptons.