A Fata Morgana (Italian: ['fa:ta mor'?a:na]) is an unusual and complex form of superior mirage that is seen in a narrow band right above the horizon. It is the Italian name for 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 deaths. Although the term Fata Morgana sometimes is applied to other, more common kinds, the true Fata Morgana is different from both an ordinary superior mirage and an inferior mirage.
Fata Morgana mirages significantly distort the object or objects on which they are based, often such that the object is completely unrecognizable. A Fata Morgana may be seen on land or at sea, in polar regions, or in deserts. It may involve almost any kind of distant object, including boats, islands, and the coastline.
Often, a Fata Morgana changes rapidly. 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.
The 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 may rest over colder dense air, forming an atmospheric duct that 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.
Video Fata Morgana (mirage)
Observing a Fata Morgana
A Fata Morgana is most commonly seen in polar regions, especially over large sheets of ice that have a uniform low temperature. It may, however, be observed in almost any area. In polar regions the Fata Morgana phenomenon is observed on relatively cold days. In deserts, over oceans, and over lakes, however, a Fata Morgana may 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 may be observed from any altitude within the Earth's atmosphere, from sea level up to mountaintops, and even including the view from airplanes.
A Fata Morgana may 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 may 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 a 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 so complex as a 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.
Gabriel Gruber (1740-1805) and Tobias Gruber (1744-1806), who observed Fata Morgana above Lake Cerknica, were the first to study it in a laboratory setting.
Maps Fata Morgana (mirage)
Etymology
"La Fata Morgana" ("The Fairy Morgana") is the name of Morgan le Fay in Italian. Morgan le Fay, also 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 and the 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 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 first century BC, and that the Rhegium Fata Morgana was described by Damascius, a Greek Philosopher of the sixth century AD. In addition, Charleton tells us that Athanasius Kircher described the Rhegium mirage in his book of travels.
An early mention of the term Fata Morgana in English, in 1818, referred to such a mirage noticed in the Strait of Messina, between Calabria and Sicily.
-
*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.
Phantom islands
In the 19th and early 20th centuries, Fata Morgana mirages may have played a role in a number of unrelated "discoveries" of arctic and antarctic land masses which were later shown not to exist. Icebergs frozen into the pack ice, or the uneven surface of the ice itself, may have contributed to the illusion of distant land features.
Sannikov Land
Yakov Sannikov and Matvei Gedenschtrom claimed to have seen a land mass north of Kotelny Island during their 1809-1810 cartographic expedition to the New Siberian Islands. Sannikov reported this sighting of a "new land" in 1811, and the supposed island was named after him. Three-quarters of a century later, in 1886, Baron Eduard Toll, a Baltic German explorer in Russian service, reported observing Sannikov Land during another expedition to the New Siberian Islands. In 1900, he would lead still another expedition to the region, which had among its objectives the location and exploration of Sannikov Land. The expedition was unsuccessful in this respect. Toll and three others were lost after they departed their ship, which was stuck in ice for the winter, and embarked on a risky expedition by dog sled. In 1937, the Soviet icebreaker Sadko also tried and failed to find Sannikov Land. Some historians and geographers have theorised that the land mass that Sannikov and Toll saw was actually Fata Morganas of Bennett Island.
Croker Mountains
In 1818, Sir John Ross led an expedition to discover the long-sought-after Northwest Passage. When he reached Lancaster Sound in Canada, he sighted, in the distance, a land mass with mountains, directly ahead in the ship's course. He named the mountain range the Croker Mountains, after First Secretary to the Admiralty John Wilson Croker, and ordered the ship to turn around and return to England. Several of his officers protested, including First Mate William Edward Parry and Edward Sabine, but they could not dissuade him. The account of Ross's voyage, published a year later, brought to light this disagreement, and the ensuing controversy over the existence of the Croker Mountains ruined Ross's reputation. The year after Ross's expedition, in 1882, Parry was given command of his own Arctic expedition, and proved Ross wrong by continuing west beyond where Ross had turned back, and sailing through the supposed location of the Croker Mountains. The mountain range that had caused Ross to abandon his mission had been a mirage.
Ross made two errors. First, he refused to listen to the counsel of his officers, who must have been more familiar with mirages than he was. Second, his attempt to honour Croker by naming a mountain range after him backfired when the mountains turned out to be non-existent. Ross could not obtain ships, or funds, from the government for his subsequent expeditions, and was forced to rely on private backers instead.
New South Greenland
Benjamin Morrell reported that, in March of 1823, while on a voyage to the Antarctic and southern Pacific Ocean, he had explored what he thought was the east coast of New South Greenland. The west coast of New South Greenland had been explored two years earlier by Robert Johnson, who had given the land its name. This name was not adopted, however, and the area, which is the northern part of the Antarctic Peninsula, is now known as Graham Land. Morrell's reported position was actually far to the east of Graham Land. Searches for the land that Morrell claimed to have explored would continue into the early 20th century before New South Greenland's existence was conclusively disproven. Why Morrell reported exploring a non-existent land is unclear, but one possibility is that he mistook a Fata Morgana for actual land.
Crocker Land
Robert Peary claimed to have seen, while on a 1906 Arctic expedition, a land mass in the distance. He said that it was north-west from the highest point of Cape Thomas Hubbard, which is situated in what is now the northern Canadian territory of Nunavut, and he estimated it to be 130 miles away, at about 83 degrees N, longitude 100 degrees W. He named it Crocker Land, after George Crocker of the Peary Arctic Club.
As Peary's diary contradicts his public claim that he had sighted land, it is now believed that Crocker Land was a fraudulent invention of Peary, created in an unsuccessful attempt to secure further funding from Crocker.
In 1913, unaware that Crocker Land was merely an invention, Donald Baxter MacMillan organised the Crocker Land Expedition, which set out to reach and explore the supposed land mass. On 21 April the members of the expedition did, in fact, see 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 it was just an illusion. He called it poo-jok, which means 'mist'. However, MacMillan insisted that they press on, even though it was late in the season and the sea ice was breaking up. For five days they went on, following the mirage. Finally, on 27 April, after they had covered some 125 miles (201 km) of dangerous sea ice, MacMillan was forced to admit that Piugaattoq was right--the land that they had sighted 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 north-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 (equivalent to $2,476,094 in 2017).
Lake Ontario
In July 1866 mirages of boats and islands were seen from Kingston, 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.
On 25 August 1894 Scientific American described a remarkable mirage seen by the citizens of Buffalo, New York.
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.
This description may possibly refer to looming due to inversion rather than to a real mirage.
McMurdo Sound
From McMurdo Station in Antarctica, Fata Morganas are often seen during the austral summer, across McMurdo Sound.
UFOs
Fata Morgana mirages may continue to trick some observers and 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.
Some UFOs which are seen on radar may also be due to Fata Morgana mirages. Official UFO investigations in France indicate:
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.
Australia
Fata Morgana mirages could explain the mysterious Australian Min Min light phenomenon.
Greenland
Fata Morgana Land, a phantom island in the Arctic reported first in 1907. After unfruitful search it was deemed to be Tobias Island.
In literature
A Fata Morgana is usually associated with something mysterious, something that never could be approached.
FATA MORGANA
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 treesThat 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.
In the book Thunder Below! about the submarine USS Barb, the crew sees a Fata Morgana (called an "arctic mirage" in the book) of four ships trapped in the ice. As they try to approach the ships the mirage vanishes.
The Fata Morgana is briefly mentioned in the HP Lovecraft horror novel At the Mountains of Madness, in which the narrator states: "On many occasions the curious atmospheric effects enchanted me vastly; these including a strikingly vivid mirage--the first I had ever seen--in which distant bergs became the battlements of unimaginable cosmic castles."
See also
- Atmospheric optics
- Fata Morgana (1971 film)
- Green flash
- Looming and similar refraction phenomena
- Mirage of astronomical objects
References
Source of the article : Wikipedia
0 Comments