Since debating Truthers is little more than an excercise in copy and pasting, I'll lower myself to their intellectual level and post one from those notorious government agents over at Popular Mechanics:

http://www.popularmechanics.com/technolo…

Claim: Photographs and video footage shot just before United Airlines Flight 175 hit the South Tower of the World Trade Center (WTC) show an object underneath the fuselage at the base of the right wing. The film "911 In Plane Site" and the Web site LetsRoll911.org claim that no such object is found on a stock Boeing 767. They speculate that this "military pod" is a missile, a bomb or a piece of equipment on an air-refueling tanker. LetsRoll911.org points to this as evidence that the attacks were an "inside job" sanctioned by "President George Bush, who planned and engineered 9/11."

FACT: One of the clearest, most widely seen pictures of the doomed jet's undercarriage was taken by photographer Rob Howard and published in New York magazine and elsewhere (opening page). PM sent a digital scan of the original photo to Ronald Greeley, director of the Space Photography Laboratory at Arizona State University. Greeley is an expert at analyzing images to determine the shape and features of geological formations based on shadow and light effects. After studying the high-resolution image and comparing it to photos of a Boeing 767-200ER's undercarriage, Greeley dismissed the notion that the Howard photo reveals a "pod." In fact, the photo reveals only the Boeing's right fairing, a pronounced bulge that contains the landing gear. He concludes that sunlight glinting off the fairing gave it an exaggerated look. "Such a glint causes a blossoming (enlargement) on film," he writes in an e-mail to PM, "which tends to be amplified in digital versions of images — the pixels are saturated and tend to 'spill over' to adjacent pixels." When asked about pods attached to civilian aircraft, Fred E. Culick, professor of aeronautics at the California Institute of Technology, gave a blunter response: "That's bull. They're really stretching."

Claim: No fighter jets were scrambled from any of the 28 Air Force bases within close range of the four hijacked flights. "On 11 September Andrews had two squadrons of fighter jets with the job of protecting the skies over Washington D.C.," says the Web site emperors-clothes.com. "They failed to do their job." "There is only one explanation for this," writes Mark R. Elsis of StandDown.net. "Our Air Force was ordered to Stand Down on 9/11."

FACT: On 9/11 there were only 14 fighter jets on alert in the contiguous 48 states. No computer network or alarm automatically alerted the North American Air Defense Command (NORAD) of missing planes. "They [civilian Air Traffic Control, or ATC] had to pick up the phone and literally dial us," says Maj. Douglas Martin, public affairs officer for NORAD. Boston Center, one of 22 Federal Aviation Administration (FAA) regional ATC facilities, called NORAD's Northeast Air Defense Sector (NEADS) three times: at 8:37 am EST to inform NEADS that Flight 11 was hijacked; at 9:21 am to inform the agency, mistakenly, that Flight 11 was headed for Washington (the plane had hit the North Tower 35 minutes earlier); and at 9:41 am to (erroneously) identify Delta Air Lines Flight 1989 from Boston as a possible hijacking. The New York ATC called NEADS at 9:03 am to report that United Flight 175 had been hijacked — the same time the plane slammed into the South Tower. Within minutes of that first call from Boston Center, NEADS scrambled two F-15s from Otis Air Force Base in Falmouth, Mass., and three F-16s from Langley Air National Guard Base in Hampton, Va. None of the fighters got anywhere near the pirated planes.

Why couldn't ATC find the hijacked flights? When the hijackers turned off the planes' transponders, which broadcast identifying signals, ATC had to search 4500 identical radar blips crisscrossing some of the country's busiest air corridors. And NORAD's sophisticated radar? It ringed the continent, looking outward for threats, not inward. "It was like a doughnut," Martin says. "There was no coverage in the middle." Pre-9/11, flights originating in the States were not seen as threats and NORAD wasn't prepared to track them.

Claim: On Sept. 11, FOX News broadcast a live phone interview with FOX employee Marc Birnbach. 911inplanesite.com states that "Bernback" saw the plane "crash into the South Tower." "It definitely did not look like a commercial plane," Birnbach said on air. "I didn't see any windows on the sides."

Coupled with photographs and videos of Flight 175 that lack the resolution to show windows, Birnbach's statement has fueled one of the most widely referenced 9/11 conspiracy theories — specifically, that the South Tower was struck by a military cargo plane or a fuel tanker.

FACT: Birnbach, who was a freelance videographer with FOX News at the time, tells PM that he was more than 2 miles southeast of the WTC, in Brooklyn, when he briefly saw a plane fly over. He says that, in fact, he did not see the plane strike the South Tower; he says he only heard the explosion.

While heading a Federal Emergency Management Agency (FEMA) probe into the collapse of the towers, W. Gene Corley studied the airplane wreckage. A licensed structural engineer with Construction Technology Laboratories, a consulting firm based in Skokie, Ill., Corley and his team photographed aircraft debris on the roof of WTC 5, including a chunk of fuselage that clearly had passenger windows. "It's ... from the United Airlines plane that hit Tower 2," Corley states flatly. In reviewing crash footage taken by an ABC news crew, Corley was able to track the trajectory of the fragments he studied — including a section of the landing gear and part of an engine — as they tore through the South Tower, exited from the building's north side and fell from the sky.

Claim: "It has been standard operating procedures for decades to immediately intercept off-course planes that do not respond to communications from air traffic controllers," says the Web site oilempire.us. "When the Air Force 'scrambles' a fighter plane to intercept, they usually reach the plane in question in minutes."

FACT: In the decade before 9/11, NORAD intercepted only one civilian plane over North America: golfer Payne Stewart's Learjet, in October 1999. With passengers and crew unconscious from cabin decompression, the plane lost radio contact but remained in transponder contact until it crashed. Even so, it took an F-16 1 hour and 22 minutes to reach the stricken jet. Rules in effect back then, and on 9/11, prohibited supersonic flight on intercepts. Prior to 9/11, all other NORAD interceptions were limited to offshore Air Defense Identification Zones (ADIZ). "Until 9/11 there was no domestic ADIZ," FAA spokesman Bill Schumann tells PM. After 9/11, NORAD and the FAA increased cooperation, setting up hotlines between ATCs and NORAD command centers, according to officials from both agencies. NORAD has also increased its fighter coverage and has installed radar to monitor airspace over the continent.

Claim: The first hijacked plane crashed through the 94th to the 98th floors of the World Trade Center's 110-story North Tower; the second jet slammed into the 78th to the 84th floors of the 110-story South Tower. The impact and ensuing fires disrupted elevator service in both buildings. Plus, the lobbies of both buildings were visibly damaged before the towers collapsed. "There is NO WAY the impact of the jet caused such widespread damage 80 stories below," claims a posting on the San Diego Independent Media Center Web site (sandiego.indymedia.org). "It is OBVIOUS and irrefutable that OTHER EXPLOSIVES (... such as concussion bombs) HAD ALREADY BEEN DETONATED in the lower levels of tower one at the same time as the plane crash."

FACT: Following up on a May 2002 preliminary report by the Federal Emergency Management Agency (FEMA), a major study will be released in spring 2005 by the National Institute of Standards and Technology (NIST), a branch of the U.S. Department of Commerce. NIST shared its initial findings with PM and made its lead researcher available to our team of reporters.

The NIST investigation revealed that plane debris sliced through the utility shafts at the North Tower's core, creating a conduit for burning jet fuel — and fiery destruction throughout the building. "It's very hard to document where the fuel went," says Forman Williams, a NIST adviser and a combustion expert, "but if it's atomized and combustible and gets to an ignition source, it'll go off."

Burning fuel traveling down the elevator shafts would have disrupted the elevator systems and caused extensive damage to the lobbies. NIST heard first-person testimony that "some elevators slammed right down" to the ground floor. "The doors cracked open on the lobby floor and flames came out and people died," says James Quintiere, an engineering professor at the University of Maryland and a NIST adviser. A similar observation was made in the French documentary "9/11," by Jules and Gedeon Naudet. As Jules Naudet entered the North Tower lobby, minutes after the first aircraft struck, he saw victims on fire, a scene he found too horrific to film.

Claim: "We have been lied to," announces the Web site AttackOnAmerica.net. "The first lie was that the load of fuel from the aircraft was the cause of structural failure. No kerosene fire can burn hot enough to melt steel." The posting is entitled "Proof Of Controlled Demolition At The WTC."

FACT: Jet fuel burns at 800° to 1500°F, not hot enough to melt steel (2750°F). However, experts agree that for the towers to collapse, their steel frames didn't need to melt, they just had to lose some of their structural strength — and that required exposure to much less heat. "I have never seen melted steel in a building fire," says retired New York deputy fire chief Vincent Dunn, author of The Collapse Of Burning Buildings: A Guide To Fireground Safety. "But I've seen a lot of twisted, warped, bent and sagging steel. What happens is that the steel tries to expand at both ends, but when it can no longer expand, it sags and the surrounding concrete cracks."

"Steel loses about 50 percent of its strength at 1100°F," notes senior engineer Farid Alfawak-hiri of the American Institute of Steel Construction. "And at 1800° it is probably at less than 10 percent." NIST also believes that a great deal of the spray-on fireproofing insulation was likely knocked off the steel beams that were in the path of the crashing jets, leaving the metal more vulnerable to the heat.

But jet fuel wasn't the only thing burning, notes Forman Williams, a professor of engineering at the University of California, San Diego, and one of seven structural engineers and fire experts that PM consulted. He says that while the jet fuel was the catalyst for the WTC fires, the resulting inferno was intensified by the combustible material inside the buildings, including rugs, curtains, furniture and paper. NIST reports that pockets of fire hit 1832°F.

"The jet fuel was the ignition source," Williams tells PM. "It burned for maybe 10 minutes, and [the towers] were still standing in 10 minutes. It was the rest of the stuff burning afterward that was responsible for the heat transfer that eventually brought them down."

Claim: As each tower collapsed, clearly visible puffs of dust and debris were ejected from the sides of the buildings. An advertisement in The New York Times for the book Painful Questions: An Analysis Of The September 11th Attack made this claim: "The concrete clouds shooting out of the buildings are not possible from a mere collapse. They do occur from explosions." Numerous conspiracy theorists cite Van Romero, an explosives expert and vice president of the New Mexico Institute of Mining and Technology, who was quoted on 9/11 by the Albuquerque Journal as saying "there were some explosive devices inside the buildings that caused the towers to collapse." The article continues, "Romero said the collapse of the structures resembled those of controlled implosions used to demolish old structures."

FACT: Once each tower began to collapse, the weight of all the floors above the collapsed zone bore down with pulverizing force on the highest intact floor. Unable to absorb the massive energy, that floor would fail, transmitting the forces to the floor below, allowing the collapse to progress downward through the building in a chain reaction. Engineers call the process "pancaking," and it does not require an explosion to begin, according to David Biggs, a structural engineer at Ryan-Biggs Associates and a member of the American Society of Civil Engineers (ASCE) team that worked on the FEMA report.

Like all office buildings, the WTC towers contained a huge volume of air. As they pancaked, all that air — along with the concrete and other debris pulverized by the force of the collapse — was ejected with enormous energy. "When you have a significant portion of a floor collapsing, it's going to shoot air and concrete dust out the window," NIST lead investigator Shyam Sunder tells PM. Those clouds of dust may create the impression of a controlled demolition, Sunder adds, "but it is the floor pancaking that leads to that perception."

Demolition expert Romero regrets that his comments to the Albuquerque Journal became fodder for conspiracy theorists. "I was misquoted in saying that I thought it was explosives that brought down the building," he tells PM. "I only said that that's what it looked like."

Romero, who agrees with the scientific conclusion that fire triggered the collapses, demanded a retraction from the Journal. It was printed Sept. 22, 2001. "I felt like my scientific reputation was on the line." But emperors-clothes.com saw something else: "The paymaster of Romero's research institute is the Pentagon. Directly or indirectly, pressure was brought to bear, forcing Romero to retract his original statement." Romero responds: "Conspiracy theorists came out saying that the government got to me. That is the farthest thing from the truth. This has been an albatross around my neck for three years."

Claim: Seven hours after the two towers fell, the 47-story WTC 7 collapsed. According to 911review.org: "The video clearly shows that it was not a collapse subsequent to a fire, but rather a controlled demolition: amongst the Internet investigators, the jury is in on this one."

FACT: Many conspiracy theorists point to FEMA's preliminary report, which said there was relatively light damage to WTC 7 prior to its collapse. With the benefit of more time and resources, NIST researchers now support the working hypothesis that WTC 7 was far more compromised by falling debris than the FEMA report indicated. "The most important thing we found was that there was, in fact, physical damage to the south face of building 7," NIST's Sunder tells PM. "On about a third of the face to the center and to the bottom — approximately 10 stories — about 25 percent of the depth of the building was scooped out." NIST also discovered previously undocumented damage to WTC 7's upper stories and its southwest corner.

NIST investigators believe a combination of intense fire and severe structural damage contributed to the collapse, though assigning the exact proportion requires more research. But NIST's analysis suggests the fall of WTC 7 was an example of "progressive collapse," a process in which the failure of parts of a structure ultimately creates strains that cause the entire building to come down. Videos of the fall of WTC 7 show cracks, or "kinks," in the building's facade just before the two penthouses disappeared into the structure, one after the other. The entire building fell in on itself, with the slumping east side of the structure pulling down the west side in a diagonal collapse.

According to NIST, there was one primary reason for the building's failure: In an unusual design, the columns near the visible kinks were carrying exceptionally large loads, roughly 2000 sq. ft. of floor area for each floor. "What our preliminary analysis has shown is that if you take out just one column on one of the lower floors," Sunder notes, "it could cause a vertical progression of collapse so that the entire section comes down."

There are two other possible contributing factors still under investigation: First, trusses on the fifth and seventh floors were designed to transfer loads from one set of columns to another. With columns on the south face apparently damaged, high stresses would likely have been communicated to columns on the building's other faces, thereby exceeding their load-bearing capacities.

Second, a fifth-floor fire burned for up to 7 hours. "There was no firefighting in WTC 7," Sunder says. Investigators believe the fire was fed by tanks of diesel fuel that many tenants used to run emergency generators. Most tanks throughout the building were fairly small, but a generator on the fifth floor was connected to a large tank in the basement via a pressurized line. Says Sunder: "Our current working hypothesis is that this pressurized line was supplying fuel [to the fire] for a long period of time."

WTC 7 might have withstood the physical damage it received, or the fire that burned for hours, but those combined factors — along with the building's unusual construction — were enough to set off the chain-reaction collapse.

CLAIM: 2) There is zero historical precedent for fire or jet fuel to have EVER caused a building to collapse in a pancake fashion

FACT: Jet fuel burns at 800° to 1500°F, not hot enough to melt steel (2750°F). However, experts agree that for the towers to collapse, their steel frames didn't need to melt, they just had to lose some of their structural strength — and that required exposure to much less heat. "I have never seen melted steel in a building fire," says retired New York deputy fire chief Vincent Dunn, author of The Collapse Of Burning Buildings: A Guide To Fireground Safety. "But I've seen a lot of twisted, warped, bent and sagging steel. What happens is that the steel tries to expand at both ends, but when it can no longer expand, it sags and the surrounding concrete cracks."

"Steel loses about 50 percent of its strength at 1100°F," notes senior engineer Farid Alfawak-hiri of the American Institute of Steel Construction. "And at 1800° it is probably at less than 10 percent." NIST also believes that a great deal of the spray-on fireproofing insulation was likely knocked off the steel beams that were in the path of the crashing jets, leaving the metal more vulnerable to the heat.

But jet fuel wasn't the only thing burning, notes Forman Williams, a professor of engineering at the University of California, San Diego, and one of seven structural engineers and fire experts that PM consulted. He says that while the jet fuel was the catalyst for the WTC fires, the resulting inferno was intensified by the combustible material inside the buildings, including rugs, curtains, furniture and paper. NIST reports that pockets of fire hit 1832°F.

"The jet fuel was the ignition source," Williams tells PM. "It burned for maybe 10 minutes, and [the towers] were still standing in 10 minutes. It was the rest of the stuff burning afterward that was responsible for the heat transfer that eventually brought them down."