A video is being widely shared on social media (and the "weird news" sections of more traditional media) claiming to show the image of an impossibly large city rising above the fog in the city of Foshan (佛山), Guangdong province, China
Here's a composite image of the Foshan video
Notice the scale of things here, there are what looks like two construction cranes on the "horizon" to the left, and the buildings seem to loom high into the sky above them.
Some have said this is an example of a fata morgana, a type of mirage where light is bent though the atmosphere in such a way to create the illusion of buildings on the horizon. This is utterly impossible in this case, as fata morgana only creates a very thin strip of such an illusion very close to the horizon, and appears small and far away. It does not create images high in the sky.
Besides, a fata morgana might create the illusion of buildings by stretching landscape features, or it might distort existing buildings. But what it cannot do it create a perfect image of existing nearby buildings, complete with windows.
The fata morgana explanation has been promoted with quotes from Atomospheric Sciences professor Kenneth Bowman, who gives a detailed explanation of what a fata morgana is. Unfortunately this was quoted in such a way that it seems like he though this was the explanation here. When I contacted him about this he said:
So no expert has actually looked at this video and said it was a fata morgana, and they won't because it's obviously not.
The second and more common type of "floating city" illusions is with buildings that are simply rising up out of clouds or low fog, and hence appear to be floating above them. This has led to "floating city" stories in the past, with this recent example, also from China.
This is simply a photo of building across the river, but when cropped it appears like they are floating, which led to all kinds of wild stories of "ghost cities". This actually came from mistranslations of the original news reports, where local people (who knew exactly what they were looking at) were simply marveling at how pretty the scene looked, with the buildings appearing to float above clouds.
Could the Foshan video be of real buildings obscured by clouds? It does not appear so. Look at some real buildings in Foshan (and keep in mind it's not entirely clear if Foshan is the actual setting of either the top or the bottom of the video.
Consider what it would take for these buildings to appear like they do in the video, with the road beneath them. The scale is simply impossible. The image has to be composited somehow, and the possibilities are:
- Computer generated buildings spliced into the video of the road.
- Two different videos spliced together
- The video is shot though glass, and the buildings are behind the camera, or to the side (with the glass at around 45°, like a half open window/door)
The image actually looks quite like this older image taken from a video published in June 2015.
Here we can see the image is more obviously faked in some way. The "floating" building on the right goes in front of the mountains. This means it cannot be some kind of natural phenomena. The image is either a digital composite, or it was filmed through a window or other sheet of glass.
While the two examples are not identical, there's enough similarities to think that they were faked in the same manner.
Here's an example of how a reflection from a half open glass door (opening outwards) can appear to be an image in the sky.
Here's an example of someone posting a reflection on Weibo, and calling it a "Mirage" (海市蜃楼)
On Weibo it's quite common to see the word "mirage" used to describe a photo of buildings in cloud. i.e. it's generally used figuratively.
The individual characters of 海市蜃楼 translate as
海 - Sea
市 - City
蜃 - Mirage
楼 - Floor