Professor thinks bombs, not planes, toppled WTC

A professor at my university gave a lecture on what happened, it was pretty plain and simple. The energy stored in each phase of the collapse mechanism is more than enough to take the next one out, steel loses huge amounts of strength as it heats (note the fuel loads and huge calorific value) causing a single floor column to collapse. There was a problem with the welding of the floor beams to the columns, the joints were not as originally specified and changed on site by the contractor. This compounded the above. PS excellent post Yankee fan.