Fata Morgana Mirage

The atmosphere plays unusual tricks with light in the polar regions, especially at sea, creating strange shapes like a looming island, a floating ship or a false wall of water to appear above the horizon. These mirages confounded early explorers. In 1818, when British explorer John Ross entered Lancaster Sound while seeking the Northwest Passage, he saw a mountain blocking his ship’s course and decided to sail no further. Ross named the mountain range the Croker Mountains, but a later expedition showed that they did not exist. In 1906, American explorer Robert Peary viewed a vast land northwest of Ellesmere Island and named it Crocker Land after his patron George Crocker. A couple of years later, Donald MacMillan went in search of the island and for five days chased the frozen apparition in vain before realizing that like Peary what he was seeing was an illusion.

The Fata Morgana mirage distorts the shape of distant ships making them appear partly hovering. Image credit: Juris Seņņikovs/Flickr

What John Ross, Robert Peary, Donald MacMillan and many others had observed was a complex mirage called Fata Morgana, named after Morgan le Fay, the shape-shifting sorceress and half-sister of King Arthur, who lured unwary sailors to their deaths.

For Fata Morgana to be observed, a condition known as temperature inversion needs to exist. This occurs when a layer of colder air immediately above the seawater is trapped below a layer of warmer air. The two layers of air that are at different temperatures and densities create an interface. When light hits this interface boundary it bends and travels through the new layer at a different angle. This is known as refraction.

In a regular mirage seen in hot conditions, the warmer layer of air is near the ground and light travelling downwards get refracted upwards creating an illusion of water reflecting. This is known as an inferior mirage. In Fata Morgana, light travelling upwards from a distant ship or landmass get refracted downwards making these objects appear to be hovering in the sky or taller than they actually are. This type of mirage is known as a superior mirage. A Fata Morgana changes rapidly and sometimes several refracted images are stacked on top of one another showing alternating compressed and stretched zones.

Image credit: Ludovica Lorenzelli, DensityDesign Research Lab

It is believed that Fata Morgana gave birth to the enduring legend of the Flying Dutchman, a ghost ship that sails around the high seas aimlessly. The story goes that a certain Dutchman came to the Cape in distress during a fierce storm but could not pilot the ship into the harbor and was lost, and ever since then in very bad weather her vision appears. The story was first mentioned in Travels in various part of Europe, Asia and Africa during a series of thirty years and upward (1790) by John MacDonald.

Throughout the 19th and 20th centuries there have been many sightings of the Flying Dutchman. Prince George of Wales, the future King George V, observed the legendary ghost ship while on a three-year voyage during his late adolescence in 1880. In the pre-dawn hours of 11 July 1881, off the coast of Australia in the Bass Strait between Melbourne and Sydney, the prince saw the Flying Dutchman crossing the bow of their ship.

A strange red light as of a phantom ship all aglow, in the midst of which light the masts, spars and sails of a brig 200 yards distant stood out in strong relief as she came up on the port bow, where also the officer of the watch from the bridge clearly saw her, as did the quarterdeck midshipman, who was sent forward at once to the forecastle; but on arriving there was no vestige nor any sign whatever of any material ship was to be seen either near or right away to the horizon, the night being clear and the sea calm.

Aside from the sea, the Fata Morgana illusion can occur also in land. In 2015, an image of a floating city appeared above a town in China startling onlookers. Although it is hard to tell from the video, experts and atmospheric scientists believe it was an example of Fata Morgana.

Superior mirage on a winter morning in the Mojave Desert creates an illusion of a large wall. The same scene in the afternoon (below). Image credit: Alan Radecki/Wikimedia Commons