THE ANSWER

Posted at 7:10 p.m. ET

Senators McCain and Obama will both be at Ground Zero this Thursday to commemorate the seventh anniversary of the terrorist attacks. 

We all know that these attacks have been the subject of a number of crazed, but probably lucrative, conspiracy theories.  Some of the most vivid involve Building 7, one of the smaller buildings in the World Trade Center complex, which collapsed late in the afternoon of September 11, 2001.

By coincidence, the National Institute of Standards and Technology released Friday the final report on what happened to Building 7.  It demolishes the quack theories, although a core of professional crackpots will probably still claim that Bush did it himself:

The National Institute of Standards and Technology (NIST) has at last determined, once and for all, what brought down one of the World Trade Center buildings during the 9/11 attacks.

The fall of the 47-story World Trade Center's Building 7 at 5:20 p.m. on Sept. 11, 2001, was primarily due to fires from the building itself, NIST announced Friday, following an extensive, three-year investigation. This was the first known instance of fire causing the total collapse of a tall building, the agency said.

The first known instance?  Ah hah!  Must have been an inside job. 

No, not quite, says the Institute:

"Our study found that the fires in WTC 7, which were uncontrolled but otherwise similar to fires experienced in other tall buildings, caused an extraordinary event," said lead investigator Shyam Sunder. "Heating of floor beams and girders caused a critical support column to fail, initiating a fire-induced progressive collapse that brought the building down."

The trapezoid-shaped Building 7 was connected to the World Trade Center plaza by an elevated walkway. The building was damaged and set afire by debris - including an enormous broadcast antennae - from the collapse of the nearby North Tower; it burned all day and collapsed itself late that afternoon.

The report addresses the conspiracy theories directly:

"Video and photographic evidence combined with detailed computer simulations show that neither explosives nor fuel oil fires played a role in the collapse of WTC 7," Mr. Sunder said.

I did not see a single broadcast story on this report, which I think is sad, because journalistic silence permits the conspiracy nuts to operate.  If any of you heard or saw such a story, please let us know.

As far as I'm concerned, that closes the book on the case of Building 7.  A new Building 7 has taken its place.

September 6, 2008.