On Saturday, the world will remember, and millions will celebrate, the Apollo 11 moon landing 50 years ago, on July 20, 1969.

A few, however, will do neither — they don’t believe it happened.

Polls show that as many as 6 percent of Americans “live in a parallel belief universe where NASA faked the Apollo moon landings,” says the Washington Post.

“The moon hoax is a classic conspiracy theory — elaborate, oddly durable, requiring the existence of malevolent actors with a secret agenda. The moon-fakers are allegedly so competent they can fool the whole world (but not so competent that they can actually put humans on the moon),” the Post says.

NASA offers considerable evidence to combat such beliefs, including the 842 pounds of rocks that astronauts brought back from the Lunar surface. But it appears that nothing will convince the  non-believers.

“The evidence that the moon landings were real is exactly what a conspiracist would expect to be manufactured by an agency committed to hoodwinking the public. This is the eternal conundrum for debunkers,” says the Post.

Some conspiracists think the filmmaker Stanley Kubrick (“2001: A Space Odyssey”) created the Apollo missions in a studio — particularly the images of astronauts walking on the moon.

They point out that photos taken by the moonwalkers don’t show stars in the sky, or that there’s no blast crater beneath their landing craft.

“The camera couldn’t pick up the faint light of stars behind the astronauts and other bright objects on the sunbathed surface,” says the Post. “And in the moon’s gentle gravity field, the lander’s descent engine didn’t need to produce much thrust to settle onto the moon’s surface.”

NASA’s reasoned approach toward the conspiracists might not be as effective as the direct method employed by Apollo 11 astronaut Buzz Aldrin.

In 2002, the Post says, Aldrin “was hectored by conspiracy theorist Bart Sibrel” outside a Beverly Hills hotel.

“Sibrel, brandishing a Bible and asking Aldrin to swear on it, said, ‘You’re the one who said you walked on the moon when you didn’t. . . . You’re a coward and a liar and a thief.’”

That, the Post says, was a mistake: 

WHAM.

“Aldrin decked him with a right cross.”