Fata Morgana (mirage)
A Fata Morgana is an unusual and complex form of superior mirage that is seen in a narrow band right above the horizon. It is an Italian phrase derived from the vulgar Latin for "fairy" and the Arthurian sorceress Morgan le Fay, from a belief that these mirages, often seen in the Strait of Messina, were fairy castles in the air or false land created by her witchcraft to lure sailors to their death. Although the term Fata Morgana is sometimes applied to other, more common kinds of mirages, the true Fata Morgana is not the same as an ordinary superior mirage, nor is it the same as an inferior mirage.
Fata Morgana mirages distort the object or objects which they are based on significantly, often such that the object is completely unrecognizable. A Fata Morgana can be seen on land or at sea, in polar regions or in deserts. This kind of mirage can involve almost any kind of distant object, including boats, islands, and the coastline.
A Fata Morgana is often rapidly changing. The mirage comprises several inverted (upside down) and erect (right side up) images that are stacked on top of one another. Fata Morgana mirages also show alternating compressed and stretched zones.
This optical phenomenon occurs because rays of light are bent when they pass through air layers of different temperatures in a steep thermal inversion where an atmospheric duct has formed. (A thermal inversion is an atmospheric condition where warmer air exists in a well-defined layer above a layer of significantly cooler air. This temperature inversion is the opposite of what is normally the case; air is usually warmer close to the surface, and cooler higher up.)
In calm weather, a layer of significantly warmer air can rest over colder dense air, forming an atmospheric duct which acts like a refracting lens, producing a series of both inverted and erect images. A Fata Morgana requires a duct to be present; thermal inversion alone is not enough to produce this kind of mirage. While a thermal inversion often takes place without there being an atmospheric duct, an atmospheric duct cannot exist without there first being a thermal inversion.
- 1 Observing a Fata Morgana
- 2 Etymology
- 3 Famous legends and observations
- 4 Fata Morgana mirages in literature
- 5 See also
- 6 References
Observing a Fata Morgana
A Fata Morgana is most commonly seen in polar regions, especially over large sheets of ice which have a uniform low temperature. It can however be observed in almost any area. In polar regions the Fata Morgana phenomenon is observed on relatively cold days, however in deserts, over oceans, and over lakes, a Fata Morgana can be observed on hot days.
To generate the Fata Morgana phenomenon, the thermal inversion has to be strong enough that the curvature of the light rays within the inversion layer is stronger than the curvature of the Earth. Under these conditions, the rays bend and create arcs. An observer needs to be within or below an atmospheric duct in order to be able to see a Fata Morgana.
A Fata Morgana can be described as a very complex superior mirage with more than three distorted erect and inverted images. Because of the constantly changing conditions of the atmosphere, a Fata Morgana can change in various ways within just a few seconds of time, including changing to become a straightforward superior mirage.
The sequential image here shows sixteen photographic frames of a mirage of the Farallon Islands as seen from San Francisco; the images were all taken on the same day.
In the first fourteen frames, elements of the Fata Morgana mirage display alternations of compressed and stretched zones. The last two frames were photographed few hours later, around sunset time. At that point in time, the air was cooler while the ocean was probably a little bit warmer, which caused the thermal inversion to be not as extreme as it was few hours before. A mirage was still present at that point, but it was not as complex as few hours before sunset: the mirage was no longer a Fata Morgana, but instead had become a simple superior mirage.
Fata Morgana mirages are visible to the naked eye, but in order to be able to see the detail within them, it is best to view them through binoculars, a telescope, or as is the case in the images here, through a telephoto lens.
"La Fata Morgana" ("The Fairy Morgana") is the name of Morgan le Fay in Italian. Morgan le Fay, alternately known as Morgane, Morgain, Morgana and other variants, was described as a powerful sorceress and antagonist of King Arthur and Queen Guinevere in the Arthurian legend. As her name indicates, the figure of Morgan appears to have been originally a fairy (Fata, Le Fay) rather than a human woman. The early works featuring Morgan do not elaborate on her nature, other than describing her role as that of a fairy or magician. Later she was described as a woman, King Arthur's half-sister, and an enchantress.
After King Arthur's final battle at Camlann, Morgan le Fay takes her half-brother Arthur to Avalon. In medieval times suggestions for the location of Avalon included the other side of the Earth at the antipodes, Sicily, and other locations in the Mediterranean.
Legends claimed that sirens in the waters around Sicily lured the unwary to their death. Morgan le Fay is associated not only with Etna, but also with sirens. In a medieval French Arthurian Romance, Floriant et Florete, she is called "mistress of the fairies of the salt sea" (La mestresse [des] fées de la mer salée.)
Ever since that time, Fata Morgana has been associated with Sicily.
It was summer, early in July, the morning calm and delightful; the winds were hushed face of the bay remarkably smooth — the tide at its full height, and the waters elevated in the middle of the channel. The sun had just surmounted the hill behind Reggio, and formed an angle of forty-five degrees on the noble expanse of water which extends before the city. Suddenly the sea that washes the Sicilian shores presented the aspect of a range of dark mountains while that on the Calabrian coast appeared like a clear polished mirror, which reflected and multiplied every object existing or moving at Reggio, with the addition of a range of more than a thousand giant pilasters, equal in altitude, distance, and degree of light and shade. In a moment they lost half their height, and bent into arcades, like those of a Roman aqueduct. A long cornice was then formed on the top, and above it rose innumerable castles, which presently divided into towers, and shortly afterwords into magnificent colonnades. To these succeeded a sweep of windows; then came pines and cypresses, and innumerable shrubs and trees: in shadier places,
- "Pan or Sylvanus never slept;
- nor nymph Nor Faunus haunted."
This glorious vision continued in full beauty till the sun was considerably advanced in the heavens; it then vanished in the twinkling of an eye; and instead of pilasters, groves, and colonnades, nothing was to be seen but the mountains of Reggio, Messina, and a beautiful expanse of water, reflecting its cultivated shores, and the cattle that were grazing on its banks.
Walter Charleton, in his 1654 treatise "Physiologia Epicuro-Gassendo-Charltoniana", devotes several pages to the description of the famous Morgana of Rhegium, in the Strait of Messina (Book III, Chap. II, Sect. II). He records that a similar phenomenon was reported in Africa by Diodorus Siculus, a Greek historian writing in the 1st century B.C., and that the Rhegium Fata Morgana was described by Damascius, a Greek Philosopher of the sixth century A.D. In addition, Charleton tells us that Athanasius Kircher described the Rhegium mirage in his book of travels.
*Fata Morgana, phr. : It. : a peculiar mirage occasionally seen on the coasts of the Straits of Messina, locally attributed to a fay Morgana. Hence, metaph. any illusory appearance. 1818 In mountainous regions, deceptions of sight, Fata Morgana, &c., are more common: In E. Burl's Lett. N. Scotl., Vol. II. p. in (1818).
Famous legends and observations
The Flying Dutchman
The Flying Dutchman, according to folklore, is a ghost ship that can never go home, and is doomed to sail the oceans forever. The Flying Dutchman is usually spotted from afar, sometimes seen to be glowing with ghostly light. One of the possible explanations of the origin of the Flying Dutchman legend is a Fata Morgana mirage seen at sea.
The news soon spread through the vessel that a phantom-ship with a ghostly crew was sailing in the air over a phantom-ocean, and that it was a bad omen, and meant that not one of them should ever see land again. The captain was told the wonderful tale, and coming on deck, he explained to the sailors that this strange appearance was caused by the reflection of some ship that was sailing on the water below this image, but at such a distance they could not see it. There were certain conditions of the atmosphere, he said, when the sun's rays could form a perfect picture in the air of objects on the earth, like the images one sees in glass or water, but they were not generally upright, as in the case of this ship, but reversed—turned bottom upwards. This appearance in the air is called a mirage. He told a sailor to go up to the foretop and look beyond the phantom-ship. The man obeyed, and reported that he could see on the water, below the ship in the air, one precisely like it. Just then another ship was seen in the air, only this one was a steamship, and was bottom-upwards, as the captain had said these mirages generally appeared. Soon after, the steamship itself came in sight. The sailors were now convinced, and never afterwards believed in phantom-ships.
While explaining the phenomenon to his crew, the captain might more precisely have used the word refraction rather than reflection, since the reflection is due to a refractive effect of layers of air. The book illustration shown above is also incorrect in the way it shows the mirage on the right: a mirage image is never wider than the source object. All the distortion and enlargement caused by this kind of mirage occurs in the vertical direction, never horizontally.
A Fata Morgana superior mirage of a ship can take many different forms. Even when the boat in the mirage does not seem to be suspended in the air, it still looks ghostly, and unusual, and what is even more important, it is ever-changing in its appearance. Sometimes a Fata Morgana causes a ship to appear to float inside the waves, at other times an inverted ship appears to sail above its "real" companion.
In fact, with a Fata Morgana it can be hard to say which individual segment of the mirage is "real" and which is not real: when a real ship is out of sight because it is below the horizon line, a Fata Morgana can cause the image of it to be elevated, and then everything which is seen by the observer is a mirage. On the other hand, if the real ship is still above the horizon, the image of it can be duplicated many times and elaborately distorted by a Fata Morgana.
The appearance of two ships changing due to the Fata Morgana phenomenon: the four frames in the first column are of ship No. 1, and four frames in the second column are of ship No. 2
Croker Mountains and Crocker Land
In the early 19th century, Fata Morgana mirages appear to have been responsible for two unrelated discoveries of non-existent arctic land masses which were given the names "Croker Mountains" and "Crocker Land".
Most of the time, the Fata Morgana display is associated with solid objects, but even the sea surface itself can create a Fata Morgana mirage under certain conditions, (see the image on the right). The small boat on the left in this image appears as if it could go right through the apparent "wall" behind it. But in reality the sailors on this boat do not see the same "wall". This wall does not really exist; it is just a mirage that is seen by an observer located on shore. The sailors on the boat might or might not have seen something similar on their horizon, depending on the exact conditions. If the sailors did see a "wall" and tried to reach it, they would have been disappointed, because, like the end of the rainbow, a Fata Morgana can never be reached.
In exactly the same way, "Croker Mountains" and Crocker Land were apparent arctic land masses which were genuinely "seen", but which could never have been reached. It is possible that the apparent "mountains" may have been caused by icebergs frozen into the pack ice. On the other hand, the apparent mountains may simply have been caused by the uneven surface of the ice itself.
In 1818, Sir John Ross was on a voyage which was an attempt to discover the long-sought-after Northwest Passage. Ross's ship reached Lancaster Sound in Canada. The Northwest Passage was straight ahead, but John Ross did not go in that direction because he saw, or thought he saw, in the distance, a land mass with mountains, which he believed made going any further simply impossible. He named the mountain range of this supposed land mass "Croker Mountains". He gave up and returned to England, despite the protests of several of his officers, including First Mate William Edward Parry and Edward Sabine. The account of his voyage, published a year later, brought to light their disagreement, and the ensuing controversy over the existence of Croker Mountains ruined his reputation. Just a year later William Edward Parry was able to sail further west, through those non-existent mountains.
Ross made two errors. His first mistake was when he was sure he saw a land mass and mountains that were not actually there despite the objections of his officers, who must have been more familiar with mirages than he was. Ross's second mistake was to name the apparent mountain range after the then–First Secretary to the Admiralty, John Wilson Croker. Naming what was in fact a mirage after such a high official cost Sir John Ross dearly: he was refused ship and money for his subsequent expeditions, and was forced to use private funding instead.
By an odd coincidence, during a 1906 expedition 88 years after Ross's expedition, Robert Peary gave the name Crocker Land to a land mass which he believed he saw in the distance, northwest from the highest point of Cape Thomas Hubbard, which is situated in what is now the northern Canadian territory of Nunavut. Peary named the apparent land mass after the late George Crocker of the Peary Arctic Club. Peary estimated the landmass to be 130 miles away, at about 83 degrees N, longitude 100 degrees W.
It is now known there is no land at that location. What Peary actually saw was almost certainly a Fata Morgana mirage.
The Crocker Land Expedition
In 1913, Donald Baxter MacMillan organised the Crocker Land Expedition which set out to reach and explore Crocker Land. On 21 April the members of the expedition saw what appeared to be a huge island on the north-western horizon. As MacMillan later said, "Hills, valleys, snow-capped peaks extending through at least one hundred and twenty degrees of the horizon.”
Piugaattoq, a member of the expedition and an Inuit hunter with 20 years of experience of the area, explained that this was just an illusion. He called it "poo-jok", which means mist. However MacMillan insisted that they press on, despite the fact that it was late in the season and the sea-ice was breaking up. For five days they went on, following the mirage, until on 27 April, having covered some 125 miles (201 km) of dangerous sea-ice, MacMillan was forced to admit that Piugaattoq was right. Crocker Land was in fact a mirage, probably a Fata Morgana.
Later, MacMillan wrote:
The day was exceptionally clear, not a cloud or trace of mist; if land could be seen, now was our time. Yes, there it was! It could even be seen without a glass, extending from southwest true to northeast. Our powerful glasses, however.. brought out more clearly the dark background in contrast with the white) the whole resembling hills, valleys and snow-capped peaks to such a degree that, had we not been out on the frozen sea for 150 miles, we would have staked our lives upon its reality. Our judgment then as now, is that this was a mirage or loom of the sea ice.
The expedition collected interesting samples, but is still considered to be a failure and a very expensive mistake. The final cost was $100,000, which was a huge sum for that time.
Mirages seen at Lake Ontario
A Mirage – The atmospheric phenomenon known as "mirage" might have been observed on Sunday evening between 6 and 7 o'clock, by looking towards the lake. The line beyond which this phenomenon was observable seemed to strike from about the middle portion of Amherst Island across to the southeast, for while the lower half of the island presented its usual appearance, the upper half was unnaturally distorted and thrown upward in columnar shape with an apparent height of two to three hundred feet. The upper line or cloud from this elevation stretched southward, upon which was thrown the image of objects. A barque sailing in front of this cloud presented a double appearance. While she appeared slightly distorted on the surface of the water, her image was inverted upon the background of the cloud referred to, and both blending together produced a curious sight. At the same time the ship and its shadow were again repeated in a more shadowy form, but distinct, in the foreground, the base being a line of smooth water. Another bark whose hull was entirely below the horizon, the topsails alone being visible, had its hull shadowed on this foreground, but no inversion in this case could be observed. It may be added that these optical phenomena in regard to the vessels could only be seen with the aid of a telescope, for the nearest vessel was at the time fully sixteen miles distant. The phenomena lasted over an hour, the illusion changing every moment in its character.
Here the described mirages of vessels "could only be seen with the aid of a telescope". It is often the case when observing a Fata Morgana that one needs to use a telescope or binoculars to really make out the mirage. The "cloud" that the article mentions a few times probably refers to a duct.
A MIRAGE SEEN AT BUFFALO, N. Y. The people of Buffalo, N. Y., were treated to a remarkable mirage, between ten and eleven o'clock, on the morning of August 16, 1894. It was the city of Toronto with its harbor and small island to the south of the city. Toronto is fifty-six miles from Buffalo, but the church spires could be counted with the greatest ease. The mirage took in the whole breadth of lake Ontario, Charlotte, the suburbs of Rochester, being recognized as a projection east of Toronto. A side-wheel steamer could be seen traveling in a line from Charlotte to Toronto Bay. Two dark objects were at last found to be the steamers of the New York Central plying between Lewiston and Toronto. A sail-boat was also visible and disappeared suddenly. Slowly the mirage began to fade away, to the disappointment of thousands who crowded the roofs of houses and office buildings. A bank of clouds was the cause of the disappearance of the mirage. A close examination of the map showed the mirage did not cause the slightest distortion, the gradual rise of the city from the water being rendered perfectly. It is estimated that at least 20,000 spectators saw the novel spectacle. This mirage is what is known as that of the third order ; that is, the object looms up far above the level and not inverted, as with mirages of the first and second orders, but appearing like a perfect landscape far away in the sky. — Scientific American, August 25, 1894.
Fata Morgana mirages and UFOs
Fata Morgana mirages may continue to trick some observers. These days hardly anybody believes in the Flying Dutchman, but Fata Morgana mirages are still sometimes mistaken for otherworldly objects such as UFOs. A Fata Morgana can display an object that is located below the astronomical horizon as an apparent object hovering in the sky. A Fata Morgana can also magnify such an object vertically and make it look absolutely unrecognizable.
As is well known, atmospheric ducting is the explanation for certain optical mirages, and in particular the arctic illusion called "fata morgana" where distant ocean or surface ice, which is essentially flat, appears to the viewer in the form of vertical columns and spires, or "castles in the air."
People often assume that mirages occur only rarely. This may be true of optical mirages, but conditions for radar mirages are more common, due to the role played by water vapor which strongly affects the atmospheric refractivity in relation to radio waves. Since clouds are closely associated with high levels of water vapor, optical mirages due to water vapor are often rendered undetectable by the accompanying opaque cloud. On the other hand, radar propagation is essentially unaffected by the water droplets of the cloud so that changes in water vapor content with altitude are very effective in producing atmospheric ducting and radar mirages.
Fata Morgana is commonly seen from McMurdo Station across McMurdo Sound during the Austral Summer. (McMurdo Fata Morgana).
Fata Morgana mirages in literature
A Fata Morgana is usually associated with something mysterious, something that never could be approached.
published in 1873 by
Henry Wadsworth Longfellow
O sweet illusions of song
That tempt me everywhere,
In the lonely fields, and the throng
Of the crowded thoroughfare!
I approach and ye vanish away,
I grasp you, and ye are gone;
But ever by night and by day,
The melody soundeth on.
As the weary traveler sees
In desert or prairie vast,
Blue lakes, overhung with trees
That a pleasant shadow cast;
Fair towns with turrets high,
And shining roofs of gold,
That vanish as he draws nigh,
Like mists together rolled --
So I wander and wander along,
And forever before me gleams
The shining city of song,
In the beautiful land of dreams.
But when I would enter the gate
Of that golden atmosphere,
It is gone, and I wonder and wait
For the vision to reappear.
In the lines, "the weary traveller sees In desert or prairie vast, Blue lakes, overhung with trees That a pleasant shadow cast", because of the mention of blue lakes, it is clear that the author is actually describing not a Fata Morgana, but rather a common inferior or desert mirage. The 1886 drawing shown here of a "Fata Morgana" in a desert might have been an imaginative illustration for the poem, but in reality no mirage ever looks like this. Andy Young writes, "They're always confined to a narrow strip of sky – less than a finger's width at arm's length – at the horizon."
The 18th-century poet Christoph Martin Wieland wrote about "Fata Morgana's castles in the air." The idea of castles in the air was probably so irresistible that many languages still use the phrase Fata Morgana to describe a mirage.
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