united states. host: upstate new york, utica. republican line. good morning. caller: this is a question about the basis of our national security strategy for the past decade. the national institute of standards and technology, the class of the world trade center, engineers will tell you that this cannot be done and the only way this can be done is with explosives. host: your question is what? caller: how do you explain this freefall without the use of explosives? guest: this is an area that i am not familiar. if you would drop me a note and mention that we talked on c- span, i will be glad to get you a more complete answer.