The physical characteristics of the World Trade Centre collapses rule out a gravity only cause for their demise, especially for WTC7 that entered into a period of complete freefall without any resistance being offered by the steel structural members. The only reasonable explanation for such a resistance free fall must consider the explosive hypothesis since the steel MUST be removed to allow the rapid collapse- at a rate equivalent to air resistance.
However, the fact that explosive materials have been found all throughout the dust has proven the case for Controlled Demolition- beyond the evidence offered by the collapse features. 911 = inside job.
[Posted at the SpookyWeather blog, May 11th, 2009.]