UFO sightings seemingly reached a cultural peak in the latter half of the 20th century; an age where home recording and crackly VHS added alien life to the skies, but the internet has – if anything – amped extraterrestrial conspiracy theories to a new level. From YouTube to Reddit, the internet can quickly turn a meteor or cloud formation into an alien spaceship.

Enter former NASA engineer, James Oberg. As Atlas Obscura reports, Oberg worked for NASA mission control in the 1990s, and is now a space journalist and historian. His newest hobby is debunking UFO sightings, not by dismissing them out of hand but by working out what’s actually going on. He also theorises reasons why people misinterpret what they’re seeing.

A common part of why people see UFOs, Oberg claims, is that our brains are used to making sense of Earth-bound objects and light conditions. If we see things that move faster or brighter than we’re used to, we get confused:

“Our sensory system is functioning absolutely perfectly for Earth conditions,” Oberg told Atlas Obscura. “But we’re still a local civilisation. Moving beyond our neighbourhood has been visually confusing.”

On his website, in a post from 2012, Oberg debunks the theory that NASA astronauts are sworn to secrecy about UFOs sighted at work. He says many of these claims are “total fantasy”, and the remaining are simply naturally occurring phenomena in space: “Most of the stories, especially videos and photographs, show phenomena that we have learned are ‘normal’ to spaceflight and the hardware that humans use there, with no extraordinary causes required,” he writes.

“These visual phenomena represent what we’ve come to recognise as expected perceptions of the consequences of human space activity. A very few others are indeed straightforward accounts of visual effects that are genuinely interesting – but hardly suggestive of ETI or unknown physics or biology.”

Oberg goes on to breakdown several common ‘sightings’ of UFOs, from bulbous plumes, which are actually caused by test missiles, to “twilight shadowing”, which are actually caused by particles on a space shuttle window.

On his website he says the “overwhelming majority of real ‘stuff’ seen by astronauts or via television or film [motion and still] is derived directly from the vehicle they happen to be aboard”. He calls this “space dandruff”, encompassing everything from paint chips to small pieces of insulation. This is different from “space junk”, which can actually pose a threat to a spacecraft.

While Oberg links UFO sightings to folklore, he ultimately admits that the spread of false accounts is “frustrating”, and distracts people from actual discoveries or real hazards during missions:

“It’s dangerous both to our astronauts and the entire nation because incorrect interpretations of in-flight reports can distract from glimpses of genuine hazards on space missions. With too many false alarms, perhaps a genuine warning could be overlooked, even briefly.”