From the million dollar offer website, StupidIdiots - which, IMO, is in extremely bad taste:

"The first person to prove explosives were NOT used in all of the above with a full, detailed mathematical analysis covering all of the points above will receive $1,000,000. The proof will be subject to verification by a scientific panel of PHD engineers, physicists, and lawyers"

Notice that they left out professional architects as people who would verify the evidence. There is no "proof", only theory, because the only way it could be proven would be to re-enact the whole scene again, which is very unlikely to ever happen.

Funny, but it's been almost five years since the attack, and I have yet to meet a single person in NYC that thinks the government did it - and I work less than a mile from Ground Zero.