BROOKE GLADSTONE: That conversation originally took place in November of 2003, and we now know that Professor Marcus was quite right in his remarks about 9/11 and the World Trade Center. Many people are suspicious about what the government says happened that day, and that's led to a lot of theories about the planes, the buildings and the smoke. The magazine Popular Mechanics set out to apply their expertise in aviation, engineering and the military to the conspiracy theories, and the results can be found in their March issue. The headline: Debunking 9/11 Lies - Conspiracy Theories Can't Stand Up to Hard Facts. James Meigs is the editor in chief of Popular Mechanics.

JAMES MEIGS: The claims that we looked at range from things like the idea that a guided missile, not a passenger plane, struck the Pentagon; that some kind of military plane, perhaps a tanker or something laden with bombs, hit the World Trade Center; that the plane that hit the World Trade Center didn't have any windows; that the World Trade Center was actually wired with explosives to make sure that it fell to the ground; that a seismograph at Columbia University picked up clear signals of bombs going off in the World Trade Center towers prior to that collapse. Those were the kinds of factual claims, and claims that can be checked, that we decided to go and basically fact check.

BROOKE GLADSTONE: Do you think you would put on the cover of Popular Mechanics - Turns Our One of These Is Actually Kind of True?

JAMES MEIGS: We were hoping we'd come up with something like that. We were hoping that there'd be a grain of truth in there somewhere that would lead to an interesting investigation. The fact is, as a journalist, what you'll see on these sites is the reporting is almost unbelievably sloppy. Things taken from, you know, a newspaper article on September 12th that was immediately corrected the next day - the correction doesn't appear - just the fact that, that emerged in the chaotic, disorganized day when everything was happening, and any big story you see, you know, the press gets a lot wrong at first. Gradually we get closer to the truth. It's never perfect. Popular Mechanics has been criticized in some quarters as focusing on the less-plausible claims. We focused on the claims that we found were most prevalent. What was interesting about the conspiracy theorists is they think anyone who's put out a claim that's less plausible is a government plant. They're doing it on purpose in order to discredit the 9/11, you know, conspiracy theory movement. They're not just confused people. And I think you see this in conspiracy theories, whether it was the anti-Communist hysteria of the '50s or the black helicopter crowd in the '80s - they think that the world is far more organized than it really is.

BROOKE GLADSTONE: Who's your audience for this? I can't imagine you'll win too many converts among the conspiracy theorists themselves, because in many respects it's really about how one views the world, your set of core beliefs, and that isn't going to necessarily be altered by an expert from NASA or the FBI.

JAMES MEIGS: That's absolutely right. We didn't think we were going to win over the kind of obsessive fringe here. But we're really trying to influence the sensible middle. There's an awful lot of people who have questions about 9/11. These questions are legitimate. We should be investigating it. But we feel that theories that are based on falsehoods don't advance the debate.

BROOKE GLADSTONE: I don't want to be contrarian here, but when you talk about a sensible middle - that's rather a slippery location. It seems from the tone of the piece that you came to your own conclusions before conducting the investigation.

JAMES MEIGS: No, we, we didn't come to any conclusions in advance. In fact, you know, there are certain things that conspiracy theorists claim that aren't completely beyond the pale, such as the idea that maybe a US military plane actually shot down the jet - Flight 93 - over Shanksville, Pennsylvania. I mean that's not a bizarre thing to wonder about, and if there is evidence that might support that, that's an important thing to look into. So, we went into it with an open mind. But when we traced these facts back to the source, they evaporated. They fell apart. I mean in the case of Shanksville, a lot of websites talk about a mysterious white plane that was seen circling the wreckage, and there's debate as to whether it was an unmarked Air Force plane or it had some kind of electro-magnetic device which would have forced the plane down. Well, we located the plane, talked to the pilot. It was just an ordinary commercial flight that happened to be on approach to a nearby airport. The FAA asked it to go in and confirm that a plane had crashed there, and it did that, and they went on their way. As journalists, we do believe that there are facts, and that it's our job to look at them, to sort them, and kind of, you know, in good faith make sure that the viewpoints that are being put out there do have some factual foundation, and I think that, regardless of one's political viewpoint, I think that's what journalism should do, and that's what we were trying to do with the story.

BROOKE GLADSTONE: James, I want you to level with me, here. Is there an unanswered question, in the midst of all your digging - is there something that was satisfying enough to put in the magazine but maybe didn't all together satisfy you?

JAMES MEIGS: Where I think more digging is needed is in what the hell went wrong that day, and in the months and years leading up to it. I think that, that that's where mainstream journalism perhaps has let us down, and I think the conspiracy theorists exploit a very natural and very healthy anger that many people have at our government that we didn't connect the dots, that we didn't manage to head this off, that we didn't protect ourselves. And I think if there's an area that needs to be investigated, that's the area. Conspiracy theorists are touching on that sense of frustration, but they're misdirecting it by, you know, kind of polluting the argument with facts that turn out not to be true and do not support the conclusions that conspiracy theorists are reaching with them.

BROOKE GLADSTONE: All right. Thank you very much.

JAMES MEIGS: It's my pleasure.

BROOKE GLADSTONE: James Meigs is the editor in chief of Popular Mechanics.