WASHINGTON - Even conspiracy theories must sometimes be taken seriously.

Every week Roger Launius, chief historian at the Smithsonian National Air and Space Museum in Washington, devotes his time to debunking one of history’s favourite such theories: That astronauts Neil Armstrong and Buzz Aldrin never landed on the moon.

The entire July 20, 1969, landing and the spacewalk several hours later was just a show, all lies, filmed in a Hollywood studio or in a desert, the sceptics say.

Few other conspiracy theories have proven so popular or long-lived.

“We Americans love that sort of thing,” Launius said as he stood before a lunar lander like the Eagle that took Armstrong and Aldrin to the moon’s surface.

In fact, conspiracy theories abound in the US: the Sep 11, 2001, terrorist attacks were planned by the government; President Barack Obama is not really a US citizen; and various false hypotheses about the assassination of president John F. Kennedy.

It didn’t take long after the moon landing for wild speculation to surface. Then the 1976 book, “We Never Went to the Moon - America’s 30 Billion Dollar Swindle”, by Bill Kaysing really got things going. It was the era of Watergate and the Vietnam War, and the theories played off the resulting distrust of the government.

At one time, up to 10 percent of Americans may have believed the conspiracy theories about the moon. On average, it has dropped to about six percent of Americans, Launius said.

The arguments of the critics include the “waving flag”, the “missing stars” and “false shadows” in television images. But at the root of the idea is that the country was not yet technologically advanced enough to make the trip. The US was in a space race with the Soviet Union during the Cold War and could not hand a win to the communists. As a last resort they reached for fabrication, the disbelievers say.

As evidence, a favourite of the doubters is the waving flag that Armstrong and Aldrin planted in the moon’s surface. How was it waving if there is no air on the moon? In actuality, the flag was equipped with a bar to keep it extended rather than hanging limp and the ripples in the cloth were due to its folding in the packaging.

Additionally, a shot of the flag actually moving was caused by an astronaut letting go of the cloth.

Then there is the issue of missing stars. Why were there no stars visible in the television pictures? The National Aeronautics and Space Administration (NASA) has responded that starlight is too weak to appear in photos under normal lighting conditions on the moon — a phenomenon also well known to every photographer on Earth.

As for the “false shadows” in NASA pictures, objects and people appeared to cast shadows in different directions rather than in parallel directions. Because the sun is the only light source on the moon, sceptics have used this as evidence that it was all filmed in a Hollywood studio with multiple lights. The experts’ answer: The moon is not flat, meaning there is no 100 percent “correct” shadow. This can even happen on Earth.

Launius calls the theories “silly”, but admits they aren’t going away any time soon.

“It would be the coolest thing on Earth to go back to the moon - just to prove that we have been there before,” he said.