The video in which a huge ship appears to float in the sky above the English city of Cornwall has gone viral on social media in recent days. The image, which appears to be the result of a computer edit, is real and constitutes an optical illusion known as fata morgana or “superior mirage”.
The phenomenon is most frequent in the winter months in the Northern Hemisphere, particularly in areas close to the Arctic, and is not usually seen at this time of year in the UK.
The necessary condition for this mirage to occur is the formation of two layers of air with a large temperature difference between them, one being cooler, closer to the surface of the water, and the other warmer, at the top.
When the light emitted by the ship on the horizon passes from the layer of warm air, which is the least dense, to the layer of cold air, which is the densest, a change in trajectory occurs and it creates the impression that the observed object is floating.
The best-known version of this phenomenon occurs on the asphalt or sand of a desert, for example. In this case, the temperature difference between the air close to the ground and the environment makes it appear that there is an area with water, like an oasis. In this case, the name is “lower mirage”.