Humans have been in continuous orbit aboard the International Space Station for 14 years and 85 days.In that time 216 individual astronauts from 15 nations have circled the Earth around 90,000 times, travelling just shy of 8km a second, watching the sun rise once every 45 minutes.Occasionally, they see stuff outside in the dark. And occasionally, so do people down here.Whether NASA likes it or not, ISS is increasingly becoming a real focus for UFO hunters.

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Last week a piece of footage supposedly showing something rising above the horizon became the basis for one of the most popular stories on this website in recent weeks.So what was it? And why do UFO hunters keep claiming that ISS is more than it appears – even though, as almost everyone knows, this is largely a huge waste of everyone’s time?

“I saw some lights that seemed to be in a line and it was almost like an upside-down check mark,” astronaut Leroy Chiao told HuffPost last year, about a famous incident during a space walk outside ISS in 2005.

“And I saw them fly by and thought it was awfully strange.”

But no, it wasn’t aliens. Like several such ‘eerie sightings’ by ISS astronauts over the years, this was a case of disquieting – but mistaken – unidentity.

“It wasn’t just one fishing boat, but a line of them strung out along the South American coast,” Chiao said. “That’s why it looked like five lights from the ISS.”

Chiao’s story is similar to several incidents in the long history of ISS.

The fact is that while ‘unexplained’ or weird sightings of lights and even objects have been reported throughout the history of the space race, none have ever held any real weight as UFO ‘experiences’.

When astronaut Chris Cassidy saw a UFO floating past his window in 2013? That was an antenna cover. When Italy’s Samantha Cristoforetti reported an “almost alien” presence outside the space station, she was commenting on the sunshine and not an actual alien. And no, slightly pausing before answering a UFO question is not the same thing as saying you saw one.

As it turns out, all the reports by ISS astronauts of aliens’ fall into the same problems as those seen by other space travellers. Like the time Gemini IV pilot saw a rotating white cylinder in space? (A rocket booster.) The circular ‘objects’ that approached the Space Shuttle in 1996? A video illusion. And no, there weren’t any aliens outside the Apollo 11 capsule, despite some poorly-worded quotes indicating the contrary.

The Sightings From Earth

There is a loose theory which states any sufficiently over-analysed event will eventually appear inexplicable.

Whether it’s an assassination or a sports event, the theory says that if enough people scour enough video and photographic evidence, they can use it to explain pretty much anything.

In the case of ISS, that’s a bit of a problem.

There have always been cameras on board the space station. And there have always been publicly-available archives of images and video clips to scour for any minute imperfection – a blip of data, a reflecting light – to blow up on Photoshop and claim as evidence of a UFO.

But as of 2014, NASA has been broadcasting – and archiving constant, live high-definition video of Earth. Almost immediately UFOs started showing up (on YouTube). And since then things have gotten a bit out of hand.

Since October alone at least four UFOs appear to have been recorded outside ISS. Earlier this year someone even spotted a ship ‘docked’ with the space station. Many of these typically pixelated, slowed-down clips are the work of the notorious UFO sleuth Streetcap1, who documents large numbers of UFO sightings on his Facebook page and on YouTube (he has almost 10,000 subscribers), which are collected by UFOSightingsDaily and – from time to time – republished by sites like ours. And now they turn up all, the, time.

In one clip recently the NASA feed seemed to cut off right after a grey shape (probably the Moon) emerged over the horizon. Streetcap1 said it definitely wasn’t the Moon, but which turned out to be the Moon. In the meantime we wrote a short, sceptical post about it and it ended up being shared on Facebook 60,000 times.

So what’s going on?

First, let’s just assume for the moment that these objects aren’t really aliens. There is, of course, a minute possibility that they are – though we’d need a bit more than a shiny light in the far distance of a 10-second video to believe it.

In reality, this just seems like a problem of volume. The amount of footage being streamed constantly from ISS means that something with some imperfection is almost always going to turn up somewhere in a week’s worth of video – if you look hard enough, you’ll find a bright object in the background, just as you would if it was live-streamed video of any other dark area.

And it’s not as if there aren’t a whole load of possible explanations: stray asteroids, space debris, reflections and even an oddly-shaped Moon have all been blamed for sightings in the past.

“Spacecraft-generated ‘dandruff’ has been seen since the very first human spaceflights, when the non-intuitive relative motions and impossible-to-judge distances in the earthly environment of outer space tricked observers into misinterpreting visual stimuli,” James Oberg, a former space engineer who specialized in NASA space shuttle operations, told HuffPost recently.

“It shouldn’t be surprising that only half a century later, most folks watching YouTube videos are still totally flummoxed by what they understandably and excusably can’t comprehend… It’s good to keep scanning space video for possible anomalies and reporting them quickly. The reason is, there is always a real chance that it could be a genuine anomaly, either a spacecraft malfunction or other threat, expected or unexpected. In the past, missions have failed because a clue that should have been seen out the window was overlooked.”

Ultimately, though, sites like Examiner.com — and us — also share some of the blame. For whatever reason, ‘UFO Outside ISS’ makes for a fairly good and easy headline – and so we and others often end up taking the bait and publishing it, although usually in honest jest rather than pretend surprise. We’ll try to resist that in future – and we’ll always let you know what we really think is going on in a particular trending clip.

Whatever you think about aliens, however, it’s hard not to admit that it is a nice idea – that an astronaut dreamily looking out of the Cupola window might see ET flying past in a saucer.