According to a new article in Popular Mechanics (Aug. 21, 2008): Conspiracy theorists have long claimed that explosives downed World Trade Center 7, north of the Twin Towers. The long-awaited report from the National Institute of Standards and Technology (NIST) conclusively rebuts those claims. Fire alone brought down the building, the report concludes, pointing to thermal expansion of key structural members as the culprit. The report also raises concerns that other large buildings might be more vulnerable to fire-induced structural failure than previously thought.In particular: The final report describes how debris from the collapse of WTC 1 ignited fires on at least 10 floors of WTC 7 at the western half of the south face. Fires on Floors 7 through 9 and 11 through 13 burned out of control, because the water supply to the automatic sprinkler system had failed. The primary and backup water supply to the sprinkler systems for the lower floors relied on the city's water supply. Those water lines were damaged by the collapse of WTC 1 and 2. These uncontrolled fires in WTC 7 eventually spread to the northeast part of the building, where the collapse began. After 7 hours of uncontrolled fires, a steel girder on Floor 13 lost its connection to one of the 81 columns supporting the building. Floor 13 collapsed, beginning a cascade of floor failures to Floor 5. Column 79, no longer supported by a girder, buckled, triggering a rapid succession of structural failures that moved from east to west. All 23 central columns, followed by the exterior columns, failed in what's known as a "progressive collapse"that is, local damage that spreads from one structural element to another, eventually resulting in the collapse of the entire structure. But I suppose that this just goes to show that the NIST is part of the conspiracy to cover up the true story of US government involvement, right?