No, this isn’t the plot of Bioshock Infinite come to life. IFLScience brings us word that thousands of people in China this week reported seeing a large “floating city” in the sky that actually turned out to be a Fata Morgana, which is a rare type of mirage.
As you can see in this news video, this particular mirage is absolutely massive and really does look like a giant city that’s floating in the clouds.
But how is this possible? This page from San Diego State University offers a nice introduction to mirages and explains how giant mirages such as this one are formed.
“[Mirages] are real phenomena of atmospheric optics, caused by strong ray-bending in layers with steep thermal gradients,” the page explains. “Because mirages are real physical phenomena, they can be photographed.”
Essentially these mirages occur whenever the sun heats up a layer of the atmosphere even as the layer below it remains at a cooler temperature. This causes light travelling through the atmosphere to get refracted and creates the illusion of objects in the sky like the giant city we see in the video.