From hovering ships to cities in the sky: a short, strange history of the mirage
An image of a 'flying' tanker off Cornwall recently went viral. But the optical phenomenon of the mirage is no stranger to astonishment, doubt – and superstition.
Tourists waiting at sunset in the middle of the Salar de Uyuni, southwest Bolivia, the largest salt lake in the world. In an illusion caused by refracted light, mountains rise from a mirage as if from water in the background.
IN early March 2021 when the internet caught hold of David Morris’s photograph of a large tanker ‘flying’ above the Cornwall horizon, responses ran wild.
Some had fun with the headline semantics (a ‘floating ship’ – isn’t that normal? LOL.) Others suggested digital tampering, while a few speculated the very large and obvious ship was being used to test radical new technology.
Morris, who had been walking his dog on the coastline near Gillan, near Falmouth, spotted the tanker on February 26 – the same day a similar vision was observed off the coast of Aberdeen. According to Morris, the ship 'looked and behaved like normal', as he observed it, snapping a series of pictures before returning attention to his dog.
It wasn’t long before the correct phenomenon of optical physics was nailed down, or thereabouts: what Morris had photographed was probably a rare illusion similar to a mirage, called looming. But so counter-intuitive are the physics – and so uncanny are the results – few could pithily explain what was happening in the image, and how.
They aren't alone. This group of atmospheric quirks have amazed, tricked, confused – and struck fear – into the minds of travellers for centuries. (Pictures: This photographer's abstract images of the world look like optical illusions.)
David Morris's image of a container ship off the coast of Cornwall as been attributed to a superior mirage, or 'fata morgana.' It is actually more likely to be a similar phenomenon called 'looming.'
Fantastic light
Looming belongs to a group of phenomena that includes superior mirages, inferior mirages, towering, stooping and sinking, all of which cause an object caught amidst a specific set of atmospheric conditions – a boat, say – to exhibit a range of visual eccentricities when viewed from afar.
These range from appearing stretched, squashed, duplicated, mirrored or elevated according to our perception. Due to the curvature of the Earth, this can also result in objects below the horizon becoming visible when ordinarily they wouldn’t – or even appearing raised above it, as if flying.
“Both superior mirage and looming give the appearance that a distant object is above the horizon when it is actually on it or sometimes hidden below it,” says Professor Liz Bentley, Chief Executive of the Royal Meteorological Society. Given the lack of reflection or duplication in Morris’s photograph, “if only a single image of a distant object is seen, then we use the term looming.”
The skyline of Chicago – including the iconic Sears Tower – appears over the skyline of Lake Michigan. Due to the curvature of the earth, the city isn't visible over the lake from here: the image is a refraction of the real skyline projected above the horizon. Like the boat in David Morris's image, this is an example of 'looming.'
The cause in all cases is the conditions just above the water, which influence the path of light through air layers of different temperatures, and therefore densities. Light being the currency of sight, this can lead to some dramatic results.
“A superior mirage or looming is caused when air near the Earth’s surface is colder than the air above it – a temperature inversion,” says Bentley. “The difference in temperature of the air also means a difference in density: warmer air is less dense than colder air. As light travels through air of different density it is refracted, or bent. You see this when you put a pencil in water, because water and air are a different density.” For the same reason that looking side-on at that pencil makes it look broken, looking down on an object in water can be deceptive, too, with it often appearing in a different position beneath the surface to the reality.
A Land Rover is photographed driving across Afghanistan's Dasht-e Margo – 'Desert of Death' – in this vintage National Geographic image. Common in hot conditions, the pale areas around the vehicle are actually refractions of the light from the sky, caused by a higher temperature of air near the ground. The shimmer caused by this phenomenon can make it appear like water to an observer – a cruel trick in a dry place, leading to mirage's association with wishful hallucinations.
In the case of a superior mirage, often generated in the cool air above water, the light bends downwards from an object through thickening air densities – making any image seen by an observer appear elevated. The reverse, where air close to the ground is hotter than that above it, can cause an inferior mirage – in which light bends upwards toward the observer, creating an optical illusion below the horizon.
In the latter case think the shimmers seen above hot asphalt, or the weird puddles of light on a desert skyline. Essentially, the mirages of popular imagination – though the term is often used inaccurately. If you’re a grasping through the desert and see an ice cream van or a fridge full of mineral water appear in front of you, you are hallucinating. An inferior mirage, while clearly capable of playing with your mind, is purely optical; a refraction of the sky, usually.
The legend of the 'Flying Dutchman', said to originated from the days of the Dutch East India Company, concerned a ghost ship doomed to sail the seas without harbour. Reports of 'hovering ships' were often attributed to the story, and considered by sailors to be harbingers of disaster at sea. But they could have simply been seeing a mirage.
Given its tendency to resemble rippling water in hot conditions such as a desert, it's a cruel trick to play on any parched traveller – and in any case, all of this rests on what the light is telling your brain, and the logical comparisons that then draws. Which can of course have consequences beyond the simply visual.
Meteorology meets mythology
The seemingly fantastical science of mirages has on occasion intertwined with the actually fantastical. Centuries ago, long before darkroom trickery or the anything-goes digital world of Photoshop, superior mirages were scaring the daylights out of already superstitious sailors. The old legend of the Flying Dutchman, a vengeful ghost clipper, was often associated with any peculiar sightings of a ship at sea, and one elevated off the water or exhibiting an inverse reflection – thus apparently sailing upside down – would certainly qualify. Such sightings were considered bad omens, but both are attributable to mirages, or in the case of a ‘flying’ ship, looming.
Another term often employed to describe an optical illusion on the horizon is fata morgana – named for Morgan le Fey, the legendary magical half-sister of King Arthur who was infamous for her visual trickery. The phenomenon was given an Italian term due to a tendency to occur in the Straits of Messina, off Sicily and is often a synonym for any kind of mirage, though there are different physics at play in each.
Less well known is its meteorological sister, the fata bromosa – another optical illusion that gives the appearance of a mist that seems to envelop (and eject) objects close to the horizon. The translation is ‘fairy fog.’
Spooks, scams and cities in the sky
Away from the water, a persistent report from 19th century travellers detailed mysterious cityscapes appearing in the sky above certain Arctic regions. This was given a bizarrely specific – not to mention enterprising – twist when Richard Willoughby, a gold prospector in Alaska, claimed to have photographed such a ‘silent city’ in the sky above a glacier near Juneau in 1888. His explanation was that it was some sort of atmospheric reflection of a steepled, faraway town, perhaps in Arctic Russia.
Willoughby’s photo was almost undoubtedly a ruse to make a quick buck: his image was later identified as being a particularly moody photograph of Bristol, complete with identifiable landmarks, probably purchased by the prospector as a job lot with some camera gear. It proved lucrative; Willoughby made meaningful money selling prints of the shot, and claimed before his death to have sold the original lantern slide for $500.
Richard Willoughby's infamous image of the 'Silent City,' which he reputedly photographed in 1888 above a glacier near Juneau, Alaska. Though widely debunked – identified as a view of the English city of Bristol taken from Brandon Hill. The identity of the true photographer is unknown, but is reputed to have been a local photographer named Harvey Barton, who may have sold Willoughby the negative as part of a job lot of photo gear.
Ruse or not, others reported the mirage in other locations in Alaska both before or after Willoughby's 'proof'. We know today that mirages are common in polar regions due to favourable conditions, but some of the descriptions defied any easy explanation. In 1889 The New York Times ran the observations of a traveller named L.B. French, who claimed to have seen a ‘specter city’ so distinct he recalled seeing “houses, streets and well defined trees… here and there rose tall spires over huge buildings with appeared to be ancient mosques or cathedrals.”
Almost a decade later in 1897, the climbers C.W. Thornton and Prince Luigi Amedeo – the latter better known as the Duke of Abruzzi – had a similar vision from the top of Mount St Elias. Thornton was reported saying that "It was so distinct that it required faith to believe that it was not really a city." Both described it as European in appearance.
The San Fransisco Call of 28 April 1901 carry the story of an expedition that intended to look for the Silent City mirage - following reports from a variety of travellers of such a spectacle in the sky above Alaska. Willoughby's photograph, while now debunked as an opportunistic fraud, was clearly designed to capitalise on a genuine phenomenon.
A scientist on the expedition, Dr Filipo de Filippi, cannily likened the vision to a desert mirage, describing its features as a 'marvellous spectacle... Their outlines underwent changes before our very eyes, assuming the forms of spires, belfries, minarets and architectural outlines of fantastic cathedrals, all of which slowly appeared and disappeared to be succeeded by buildings of lesser height, severely rectilinear.”
Either way, so unknown and mystical was Alaska, a refracted image of an English city appearing in the sky above a location over 4,000 miles was apparently accepted as simply an intriguing quirk of a peculiar region – despite experts of the time expressing grave doubt such a thing was possible.
Caught on video
This if anything, attests to the peculiar and unpredictable nature of the mirage. And city-sized visions are not unknown – most dramatically evidenced by recent scenes captured on video from China, such as one in 2015 showing the ominous shapes of high rises in the sky, and another from 2019 above Yantai, with even fine details like cranes visible.
What all of these phenomena apparently share is their unpredictability: it's difficult to know when they will occur, or – as evidenced by all – where they will appear. And as David Morris's picture of that ‘hovering’ ship neatly demonstrates, after centuries of mystique the mirage's capability to confound and amaze shows no signs of diminishing.
