The images shared on Facebook by Glacier Bay National Park have, since the beginning of the month, provoked enormous discussion and fascination. Why? Some people thought it was a UFO.
In the video you can see what appears to be one of the small islands in the area, hovering in the air above the cold waters. It is of course an optical illusion, based on a phenomenon called Fata Morgana or Fairy Morgana, which is able to distort objects on the horizon.
“Fata Morgana is a mirage seen through a small strip on the horizon,” the Glacier Bay National Park and Preserve explained on social media. “The islands in the bay become a kind of flying object.”
The recording was made on a relatively warm day for the glacial region, with thermometers reading 21°C. It is this warming that gives rise to the phenomenon, which arises thanks to the high temperature of the atmosphere immediately above the water, which creates a kind of section of layers of different temperatures. “The calm, cooler air forms at the surface of the water, and then if the warmer, denser air pushes it around, this lens is created.”
When air of different densities meet, the air in Earth’s atmosphere acts as a refractive lens and creates the mirage we seeGlacier Bay National Park and Preserve
This distortion at the water surface level creates the illusion that everything on that horizon line appears to be displaced. This is also the phenomenon behind the accounts of many sailors over the centuries, who claimed to see the famous Flying Dutchman – the cursed ship that brought bad omens – on the horizon, which turned out to be nothing more than another ship affected by the optical illusion.
The phenomenon is more common than people think. As recently as June, in Cyprus, several images seemed to show cargo ships levitating over the waters. They were also evidence of the Fata Morgana phenomenon.