Thousands of residents from Jiangxi and Foshan in China reported seeing a "floating city" in the sky earlier this month. The images and grainy video footage appear to show towering skyscrapers poking out of the clouds and looming over the ground below.

Of course, the news has got people's imaginations turned up to overdrive when trying to figure out what was going on. Explanations for the event have ranged from a glitch in the matrix, alternate universes opening up and NASA attempting to establish a new world order through a plan called the "Blue Beam Project".

However, it appears the explanation is actually a rare type of mirage called Fata Morgana. It’s essentially an optical illusion caused by specific weather conditions bending light rays. As Wired explains, it occurs when the Sun heats up a layer of the atmosphere but the layer of air below it remains cool. When different layers of the atmosphere are different temperatures, a temperature gradient is generated. These different temperatures also mean differing densities between the layers.

When light hits a boundary between two layers of the atmosphere that are different temperatures and thus densities, it is bent, or refracted, and subsequently enters the next layer at a different angle. Our brain can't automatically account for this, so when light hits our eyes, our brain assumes that it traveled in a straight path. When it has been refracted, we therefore perceive the object is where it would be if the light had run straight – which is higher than it actually is.

Fata Morganas have been confusing people and messing with minds for centuries. They’re named after Morgan le Fay, a powerful enchantress from the tales of King Arthur. It’s believed they are the explanation behind the legendary ghost ship the Flying Dutchman and sailor’s stories of floating castles which lured men to their deaths.

So there you have it. Although, we’ve got our eye on you NASA…