Though it’s fun to fantasize that the footage of a city floating above two cities in China has captured the leaking of a parallel universe into our own reality, the truth is much more boring.

Debunkers have stepped forward to calm the online mania that followed the posting of several photos and videos of the mysterious floating city. Their explanation is quite simple: it’s an optical illusion called Fata Morgana.

And as interesting as that phenomenon may be, there are several other — and far more outlandish — theories to explain the strange sighting.

It all began on October 7, when people spied the remarkable image above Foshan in China’s Guangdong province, Tech Times reported. They pulled out smart phones and began to film the sight, fascinated and probably a little terrified at the same time. A few days later, the city was seen floating above Jiangxi in China.

All told, thousands of people reported seeing the floating city, the Express noted.

“The footage captured by a local resident appears to show a huge city floating in the clouds. The apparition, which was witnessed by hundreds of shocked residents, only lasted a few minutes before completely disappearing.”

Understandably, people began to lose their collective minds over the sighting, espousing all kinds of crazy (or are they crazy?) theories to explain it. But first, the most likely explanation: the Fata Morgana.

This optical illusion is created by the weather and is caused when warm air sits atop cool air — which doesn’t happen too often. When it does, this creates an atmospheric duct, which acts like a lens for radiation wavelengths and refracts light. This then creates a sharp image.

So, why the skyscrapers? Fata Mogana distorts and inverts distant objects like boats, and these can then appear as skyscrapers in the resulting illusion because the images end up stacked, as light rays pass through air of different temperatures and bends.

The only problem with this theory, however, was pointed out by Uproxx: Foshan is 30 miles from the ocean and the atmospheric ducts responsible are pretty rare over land (though they do happen), so that raises some questions.

Now for the crazier theories about China’s floating city. One contends that it’s actually the product of NASA’s “secret” program, Project Blue Beam, whose mission is to use holographic image projection to create an alien invasion or coming of Christ to see what the masses would do. Quebecois conspiracist Serge Monast first discussed this program in the 1980s and predicted they would take place in 1983, 1996, and 2000.

Another option is that China is doing something similar to test their own citizens — proponents of this theory believe China has made the technological advancements necessary to pull off a giant holographic image in the sky.

Thousands of residents of Jiangxi and Foshan of China claim they have seen a 'floating city' in the sky pic.twitter.com/kc2vsj1yUf — People's Daily,China (@PDChina) October 18, 2015

Then there’s the much more interesting idea that the floating city is actually a parallel universe, which dipped through the veil long enough to show itself to Earth. Tech Times noted that most people think such a phenomenon is the stuff of fiction, but some serious scientists are actually studying the possibility that they exist.

One of these scientists is a guy named Michael Hall, who in 2014 brought forth a quantum theory about parallel universes. He and his research team believe they react and influence other worlds through repulsion.

Floating city seen in 2011 -- Photo Courtesy YouTube Screengrab

Whatever the truth behind the phenomenon is — secret government program, parallel universe, or simple mirage — it has happened before. In 2011, another floating city appeared above Huangshan City, as well.

What’s your favorite theory? Got one of your own?

[Photo Courtesy Twitter]