On July 20, 1969, astronauts Neil Armstrong and Buzz Aldrin landed on the moon while fellow astronaut Michael Collins orbited in a command module. Conspiracy theories denying the moon landing soon started.

For authoritative Web sites debunking these conspiracy theories, see:

• Robert Braeunig’s site, “DID WE LAND ON THE MOON?”
• Phil Plait’s BadAstronomy.com site
• Redzero’s “Moon Hoax” site.

Robert Braeunig explains why stars are not visible in photographs taken on the moon:

The answer is very simple: they are too faint. The Apollo photos are of brightly lit objects on the surface of the Moon, for which fast [camera] exposure settings were required. The fast exposures simply did not allow enough starlight into the camera to record an image on the film. For the same reason, images of the Earth taken from orbit also lack stars. The stars are there; they just don’t appear in the pictures.

Redzero talks about the almost 400 kg. of moon rocks the astronauts brought back:

We know for certain that they came from the moon. 100% certain. They are like nothing else on Earth and they couldn’t have been constructed artificially because they bear the evidence of billions of years exposure to a vacuum, high energy cosmic rays, tiny asteroids and virtually no water. Nothing on Earth could replicate this, either naturally or man-made.

Phil Plait explains why the lunar landing module did not produce any flames when it took off from the moon:

There is actually a simple reason why you cannot see the flame from the lander when it took off. The fuels they used produced no visible flame! The lander used a mix of hydrazine and dinitrogen tetroxide (an oxidizer). These two chemicals ignite upon contact and produce a product that is transparent.

NASA recently stated it is “disappointed that conspiracy theorists ignore basic science principles to diminish arguably the greatest feat in the history of human exploration. It insults the dedication and the sacrifices made by hundreds of thousands of people who were a part of the Mercury, Gemini and Apollo programs.”

I did a Web chat yesterday on conspiracy theories. Topics included the September 11 attacks, the Kennedy assassination, the moon landing, the origin of AIDS, why Osama bin Laden is not wanted by the Federal Bureau of Investigation (FBI) for the September 11 attacks, the Illuminati, and other subjects. Check it out.

The popular Discovery Channel program “Mythbusters” debunked allegations that the U.S. Moon landings were faked, in an August 27 episode.

It pointed out that Apollo astronauts left several retro-reflectors on the Moon, which have been “pinged” with powerful lasers from Earth, sending a signal back. Apollo missions 11, 14, and 15 left reflectors where they landed – clear evidence they traveled to the Moon.

The mythbusters conducted elaborate experiments to debunk popular claims by hoax believers. Some examples:

Films of a flag flapping on the Moon mean there must have been wind blowing, but there’s no atmosphere on the Moon.

The mythbusters placed a replica American flag in a vacuum chamber, to test if a flag could flap in an environment with no atmosphere. They found that moving the flag’s staff, as the astronauts did when they planted it in lunar soil, caused the flag to flap vigorously, as if it were being blown by a breeze.

You can’t make a clear footprint in lunar soil because it contains no moisture.

Because the Moon lacks water and an atmosphere, lunar soil particles are not smoothed by erosion. Their sharp edges make them able to hold a well-defined footprint. The mythbusters used a spacesuit boot to make a footprint in dry material that the National Aeronautical and Space Administration (NASA) uses to simulate lunar soil. When done in a vacuum chamber, this left a footprint very similar to ones made on the Moon.

Why are no stars visible in the sky in many photographs taken on the Moon?

The program called attention to a web site that explains this puzzle. The light hitting the Moon’s surface from the sun is so bright that it “washes out” the relatively dim light from stars in the background in photographs, just as bright city lights make it hard to see stars at night.