high temperature documentedby FEMA in Appendix C of its report. Subsequent analysis also revealed thesignature of thermite.In addition to thermite, a material that shouldnot be in the WTC, a group of scientists led by physicist Steven Jones found indust samples (those clouds of pulverized concrete) what they callednano-thermite. Their findings were published in the Open Chemical Physics Journal, Volume 2, with the title"Active Thermitic Material Discovered in Dust from the 9/11 World TradeCenter Catastrophe" and were confirmed by chemical engineer Mark Basilewho found the same material. Unlike thermite, an incendiary material,nano-thermite is explosive.The first thing they found were microspheresrich in iron (photo below) that are a signature of a thermitic reaction. Inaddition to them the USGS (United States Geological Survey), a governmentagency, and the environmental firm RJ Lee also found these spheres. Then Steve Jones with the help of physicistJeff Ferrer, an expert in the use of scanning and transmission electron microscopes,found the red/gray chips that are unreacted nano-thermite.Red/gray chipsThe nano-thermite is basically composed ofaluminum and iron oxide, such as thermite, in an array of silicon with carbon,an organic component used to generate gas making the material explosive. Whatmade these scientists to characterize this kind of thermite as nano-thermitewas precisely their scale. This material begins to react only when thetemperature reaches 430o C, so its necessary to use some incendiary to generatethat temperature. Then, once is ignite, the oxygen passes from the iron oxideto the aluminum releasing large amounts of energy and generating molten iron.To create the micro-spheres the only plausibleexplanation so far is that when the nano-thermite explodes, it generates molteniron that is ejected into the air very quickly, and similarly when it rains thewater falls as droplets, the molten iron form droplets that quickly cooledbefore reaching the ground, forming the micro-spheres.If we going to analyze the collapse of the WTCtowers we must at least have an idea of how the towers were built and some ofthe characteristics are really interesting.The core of each tower was a rectangle of 26.5by 40.5 meters,divided into 47 steel columns that ranged from 91.5 by 40.5 centimeters to56 by 132 centimetersand were much thicker at the base. In this core was where the elevators (eachtower had 99), ladders, pipes and pipe maintenance were, in other words,despite this massive steel structure in the center to support the building, thecore was basically empty.WTC tower being builtWTC tower schematicAs for the external perimeter walls they werecomposed of a dense frame of vertical steel columns with a layer of steelspandrel enclosing each floor.Assembling of the externallayerThis external layer was constructed with piecesof steel prefabricated consisting of three vertical columns with threehorizontal steel spandrels welded together. Adjacent parts were bolted, column withcolumn in the top and bottom, spandrels with their neighbors on which side withnumerous screws. Pieces used in the externallayerThere were 59 columns on the external layer ofeach face and one column in the beveled corner, a total of 240 external columnsin each tower. And as the columns in the core at the base they were much thickerthan in the top. Tower in constructionThe towers were supported by this