Recently there was an astonishing report from China. According to the Daily Mail, “thousands of people in China claim they have seen a floating city in the sky.” There is even a video that shows this strange event.
It wasn't too long before skeptics attempted to debunk this sighting, trying to explain it as something natural and understandable. This Daily Mail story had the headline “Sightings of a 'floating city' in China are simply an optical illusion, say scientists.” The story then suggested that the sighting was an example of an optical illusion called Fata Morgana. A Fata Morgana is a rather complex form of mirage.
Is this explanation a credible hypothesis to explain the reported sighting? No, it isn't. The explanation is completely unbelievable, for some reasons I will now explain.
A Fata Morgana is a mirage that appears on the horizon, as mentioned in the first sentence of the wikipedia.org article on the topic: “A Fata Morgana is an unusual and complex form of superior mirage that is seen in a narrow band right above the horizon.” But the video does not show a floating city on the horizon. It shows what looks like a city floating quite far above the horizon. If you fast forward to the 55th second of the video above, you will see the image below. It is something that occupies a large fraction of the viewing area, and is far above the horizon.
Another reason why the Fata Morgana explanation does not work is that when one sees a Fata Morgana or any type of mirage, it only appears as a relatively tiny part of your viewing area. You may see a mirage that looks like an object that is one percent of the viewing area in front of you, but no one ever reports a mirage that appears as a large fraction of their viewing area. For example, someone walking in the desert may see a mirage that looks like a distant oasis, but he will never see a mirage that looks like a huge ocean ahead of him. But the video of the sighting shows a huge “floating city” that is a large fraction of the viewing area. In fact, the buildings of the "floating city" look 10 times taller than any of the buildings on the horizon, which is not at all what one sees in a mirage or Fata Morgana (which may mirror something on the horizon, but never make it look many times bigger).
Another reason for rejecting the Fata Morgana explanation is that the “floating city” looks like a set of buildings as you would see them looking up at them from the ground, with the buildings towering above you. But the video was taken from a high location way above the ground; and if some distant buildings were somehow to be reflected up in the sky through some Fata Morgana effect, we would not see the buildings from such a “towering above you” angle. You would instead see them looking as distant buildings might look if you viewed them from a high window of an apartment building.
There is no known natural effect that can explain seeing large floating cities well above the horizon. Hilariously, the Daily Mail article claims that floating cities in the sky are a “relatively common occurrence,” which simply isn't true.
What explanations can we give for this sighting? One possibility is that the video is just a fraud. But that doesn't explain the reported fact that thousands of people witnessed the sighting. (Of course, it's always possible that both the video and the news story are frauds.)
The Daily Mail article does mention some weird conspiracy theory called Project Blue Beam, involving the idea that “Nasa will someday simulate an alien invasion of Earth or second coming of Christ through holograms.” That, of course, is nonsense. I think that it has been included in the article so that skeptics can say, “Why of course we should believe in the sensible idea of a mirage rather than the absurd idea of some weird NASA conspiracy to project holograms.” I've seen this countless times – when you want people to pay no attention to some paranormal-seeming phenomenon, always suggest the most ridiculous paranormal explanation you can think of, so people will prefer your natural explanation, no matter how untenable your natural explanation is.
I can think of a more intelligent idea, which is simply that some mysterious unknown intelligence is trying to gradually make its presence known to us, by a series of signs that are growing more dramatic in number and more spectacular as time goes on. Such an intelligence might be divine, extraterrestrial, spiritual, extra-dimensional or angelic. Using such a theory, we might explain several different phenomena, including crop circles, inexplicable objects photographed on Mars, various types of UFOs, and some other bizarre phenomena. Of course, it's quite a conceptual leap to suggest such an idea, but when “thousands of people” start reporting a city floating in the sky, we should not necessarily be conservative in trying to explain things.