Was the real cause of the collapse of the Twin Towers on Sep 11 something other than the plane crashes? Were in fact the towers demolished by controlled explosions? Was it an inside job? Judge for yourself:
http://serendipity.magnet.ch/wtc.html
"Obviously the towers did not collapse because of the plane impacts alone, because both towers stood for 45 to 90 minutes after impact. The official explanation, parroted faithfully by the mainstream media, is that the towers collapsed because burning jet fuel caused the steel girders supporting them to melt. First we must examine this hypothesis as to its credibility.
"Firstly, much, or perhaps most, of the jet fuel was consumed in the fireballs which erupted when the planes hit the towers. Furthermore, it is likely that the jet fuel which managed to enter the towers would have burnt fairly quickly (jet fuel does not burn slowly like wood). And finally there were sprinkler systems in place in the towers, and it can be surmised that these would have hindered the spread of the fire (by soaking combustible material) even if they had no effect on the burning jet fuel itself. The Twin Towers were giving off a lot of black sooty smoke, but there was little fire visible. But to melt steel you need the high temperature produced by, e.g., an oxy-acetylene torch. Jet fuel burning in air (especially in an enclosed space within a building, where there is much smoke and little available oxygen) just won't do it. And if the steel columns had melted, would this have produced the implosive collapse observed? If the columns had melted like toffee they would have bent (not snapped), causing the upper parts of the towers to buckle and tip to one side (probably the side where the planes hit). This did not happen. These considerations show that the claim that tens of thousands of liters of burning jet fuel produced a raging inferno and caused the steel columns to melt is extremely dubious, and does not account for the collapse of the towers."
http://serendipity.magnet.ch/wtc.html
"Obviously the towers did not collapse because of the plane impacts alone, because both towers stood for 45 to 90 minutes after impact. The official explanation, parroted faithfully by the mainstream media, is that the towers collapsed because burning jet fuel caused the steel girders supporting them to melt. First we must examine this hypothesis as to its credibility.
"Firstly, much, or perhaps most, of the jet fuel was consumed in the fireballs which erupted when the planes hit the towers. Furthermore, it is likely that the jet fuel which managed to enter the towers would have burnt fairly quickly (jet fuel does not burn slowly like wood). And finally there were sprinkler systems in place in the towers, and it can be surmised that these would have hindered the spread of the fire (by soaking combustible material) even if they had no effect on the burning jet fuel itself. The Twin Towers were giving off a lot of black sooty smoke, but there was little fire visible. But to melt steel you need the high temperature produced by, e.g., an oxy-acetylene torch. Jet fuel burning in air (especially in an enclosed space within a building, where there is much smoke and little available oxygen) just won't do it. And if the steel columns had melted, would this have produced the implosive collapse observed? If the columns had melted like toffee they would have bent (not snapped), causing the upper parts of the towers to buckle and tip to one side (probably the side where the planes hit). This did not happen. These considerations show that the claim that tens of thousands of liters of burning jet fuel produced a raging inferno and caused the steel columns to melt is extremely dubious, and does not account for the collapse of the towers."