The time t required for an object to fall from a height h (in a vacuum) is given by the formula t = sqrt(2h/g), where g is the acceleration due to gravity. Thus an object falling from the top of one of the towers (taking h = 1306 feet and g = 32.174 ft/sec2) would take 9.01 seconds to hit the ground if we ignore the resistance of the air and a few seconds longer if we take air resistance into account. The Twin Towers each collapsed in less than fifteen seconds, close to free fall (see this video clip, originally from
http://thewebfairy.com/911/). Following the start of the collapse the upper floors would have had to shatter the steel joints in all 85 or so floors at the lower levels. If this required only one second per floor then the collapse would have required more than a minute. But the material from the upper floors ploughed through the lower floors at a speed of at least six floors per second. This is possible only if all structural support in the lower 85 or so floors had been completely eliminated prior to the initiation of the collapse. Since the lower floors were undamaged by the plane impacts and the fires, the removal of all structural support in these floors must have been due to some other cause — and the most obvious possibility is explosives. Thus the speed of the collapse (not much more than the time of free fall) is conclusive evidence that the Twin Towers were brought down in a controlled demolition involving the use of explosives (or some other destructive technology) at all levels.
if you want to argue one or two seconds and try and say its for some reason a significant deviation from free fall speeds your welcome to it
given that the calculated time of a natural collapse is over one minute Id say your barking at the wind again
http://www.serendipity.li/wot/wtc_fig_01.gif
there's your seismic evidence of the various explosions
read it and weep
Seismic Evidence
But although some kind of "black" technology may have been used in the demolition of the Twin Towers, we do not need to establish this, since their collapse can be explained as a controlled demolition brought about by explosives. In fact (as Christopher Bollyn was the first to point out in his Open Letter) evidence for massive explosions was captured by a seismograph located 34 km from the WTC:
http://www.serendipity.li/wot/wtc_fig_01.gif
A "sharp spike of short duration" is how an underground nuclear explosion appears on a seismograph.
The seismograph which recorded this data was operated by Columbia University's Lamont-Doherty Earth Observatory. A report was published by the American Geophysical Union in the November 20 issue of Eos, but the authors misinterpreted the data. They assumed, and thus reported, that the two largest signals were caused by the collapses of the Twin Towers. But:
During the collapse, most of the energy of the falling debris was absorbed by the towers and the neighboring structures, converting them into rubble and dust or causing other damage — but not causing significant ground shaking. — Dr. Arthur Lerner-Lam, Director of Columbia University's Center for Hazards and Risk Research, as quoted in Earth Institute News
