Fifty years ago this weekend, man landed on the moon, an incredible feat but one some people still don't think happened. An expert from Sunderland University considers the psychology behind the conspiracy theories.

IT is 50 years ago this weekend – July 20, 1969 – that man first landed on the moon. Or did he? Inevitably, the milestone also sees the resurfacing of an array of conspiracy theories surrounding the historical moment. But why are we so obsessed with disproving what is arguably one of humanity’s greatest achievements?

“There are lots of reasons people believe in conspiracy theories, such as those questioning whether or not we ever went to the moon," says Dr Sophie Hodgetts, a lecturer in Psychology at the University of Sunderland. "One such reason is confirmation bias, a cognitive processing error that causes people to focus only on information that supports their view, while disregarding evidence to the contrary. We see this a lot with the moon landings – many conspiracy theorists argue against the evidence provided by NASA in favour of their own reasoning.

“There are some dispositions that are more likely to believe in conspiracy theories. Unsurprisingly, research suggests that people who are generally more paranoid are more likely to endorse conspiracy theories. In addition, there is evidence to suggest that feelings of anxiety correlate positively with conspiracy belief.

“This may be because endorsing a conspiracy theory can generate feeling 'special', as if one has unique knowledge. This also helps to create a specific social identity in believers, an 'us vs them' mentality that can bolster those beliefs. In the current global climate, this may be one reason why many more people appear to be endorsing conspiracy beliefs such as those surrounding the moon landing, Flat Earth, or vaccines.”

In the late 1960s and early 1970s, the US public was already sceptical, with everything from the Vietnam War to the corruption of Watergate leading the average person to distrust anything their government might be telling them. Back in 1970 an American newspaper company found that a whopping 30 per cent of Americans believed the moon landing had been faked. And a Gallup poll in 1976 found that 28 per cent of them believed that the landing had been staged by the US government—pretty consistent findings throughout the 1970s.

Common conspiracy theories which still abound surrounding the landing suggest the Apollo mission was a hoax staged by NASA, perhaps with the help of other organisations. Theories suggest the public were deliberately misled about the event, going as far as suggesting the whole thing was staged and vital evidence destroyed.

So what are some of the reasons that people say the landing didn't happen - and how are they refuted?

NO STARS

Some conspiracy theorists reference the lack of stars in the pictures taken by the Apollo astronauts from the surface of the moon. The answer given for this is that the stars are there, but just that they are too faint to see.

THE FLAPPING FLAG

Another claim is that the famous US flag, which appears in photos of the moment, appears to be flapping in the wind. Doubters say there wouldn't be wind on the moon as there is no air.

However, the counter-argument suggests that, although it looks like it is moving, it isn't. When it was stuck in the ground it would have been disturbed and kept that bent shape.

MISSION IMPOSSIBLE

Some people don't believe in the space shuttle and the missions to the moon because they think the journey itself was impossible because of something called the Van Allen belts. The Van Allen belts are huge belts of radiation that surround the Earth. It's been claimed that humans would not be able to pass through these belts without being subjected to lethal doses of radiation.

Radiation sickness occurs when you have been exposed to around 200 to 1000 'rads' of radiation within a few hours. The Apollo 11 crew were within the belts for less than two hours during their journey to the moon, and so would have only been exposed to an estimated 18 rads - well within the safe limit.

NASA made sure that the spacecraft was well-insulated so actually the average dose of radiation over the 12-day mission was just 0.18 rads - similar to a chest X-ray.

FOOTPRINTS

You can still see where the different Apollo missions landed and even the footprints of the astronauts from space. On Earth, footprints or other markings on the surface are easily erased by the winds, rain and other surface activity which happens on a planet with an atmosphere, oceans and life. On the moon, however, there are none of those conditions, which is why the footprints remain.

NASA's Lunar Reconnaissance Orbiter, which has been in orbit around the Moon since 2009, has captured photographs of all the Apollo landing sites. The images show the Apollo spacecraft in exactly the right locations and, amazingly, you can even see the astronauts' footprints as they explored their lunar home.