Looming and similar refraction phenomena
Encyclopedia
While mirage
s are the best known atmospheric refraction
phenomena, looming and similar refraction phenomena do not produce mirages. Mirages show an extra image or images of the miraged object, while looming, towering, stooping, and sinking do not. No inverted image is present in those phenomena either. Depending on atmospheric conditions, the objects can appear to be elevated or lowered, stretched or stooped. These phenomena can occur together, changing the appearance of different parts of the objects in different ways. Sometimes these phenomena can occur together with a true mirage.
in 1798, who wrote:
Other famous observations that were called "mirages" may actually be referring to looming. One of those was described in Scientific American on August 25, 1894 as "a remarkable mirage seen by the citizens of Buffalo, New York
".
Looming is most commonly seen in the polar region
s. Looming was sometimes responsible for the errors made by polar explorers; for example, Charles Wilkes
charted the coast of Antarctica, where later only water was found.
The larger the size of the sphere (the planet where an observer is located) the less curved the horizon is. William Jackson Humphreys'
calculations showed that an observer could see all the way around a planet nearly six times larger in radius than the Earth, with the same atmosphere
as the Earth, because of looming.
In general looming is more noticeable than sinking because objects that get bigger stand out more than ones that get smaller.
is curved.
Mirage
A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. The word comes to English via the French mirage, from the Latin mirare, meaning "to look at, to wonder at"...
s are the best known atmospheric refraction
Atmospheric refraction
Atmospheric refraction is the deviation of light or other things like humanelectromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of altitude...
phenomena, looming and similar refraction phenomena do not produce mirages. Mirages show an extra image or images of the miraged object, while looming, towering, stooping, and sinking do not. No inverted image is present in those phenomena either. Depending on atmospheric conditions, the objects can appear to be elevated or lowered, stretched or stooped. These phenomena can occur together, changing the appearance of different parts of the objects in different ways. Sometimes these phenomena can occur together with a true mirage.
Looming
Looming is the most noticeable and most often observed of these phenomena. It is an abnormally large refraction of the object that increases the apparent elevation of the distant objects and sometimes allows an observer to see objects that are located below the horizon under normal conditions. One of the most famous looming observations was made by William LathamWilliam Latham
William Latham is a British computer artist, most known as the creator of the Organic Art product as well as for creating album covers and artwork for the dance group The Shamen. Latham is the founder of the company Computer Artworks which released the Organic Art product through Time Warner...
in 1798, who wrote:
Other famous observations that were called "mirages" may actually be referring to looming. One of those was described in Scientific American on August 25, 1894 as "a remarkable mirage seen by the citizens of Buffalo, New York
Buffalo, New York
Buffalo is the second most populous city in the state of New York, after New York City. Located in Western New York on the eastern shores of Lake Erie and at the head of the Niagara River across from Fort Erie, Ontario, Buffalo is the seat of Erie County and the principal city of the...
".
Looming is most commonly seen in the polar region
Polar region
Earth's polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica...
s. Looming was sometimes responsible for the errors made by polar explorers; for example, Charles Wilkes
Charles Wilkes
Charles Wilkes was an American naval officer and explorer. He led the United States Exploring Expedition, 1838-1842 and commanded the ship in the Trent Affair during the American Civil War...
charted the coast of Antarctica, where later only water was found.
The larger the size of the sphere (the planet where an observer is located) the less curved the horizon is. William Jackson Humphreys'
William Jackson Humphreys
William Jackson Humphreys was an American physicist and atmospheric researcher.-Biography:Hymphreys was born on February 3, 1862 in Gap Mills, West Virginia. He studied physics at Washington & Lee University in Virginia and later at Johns Hopkins University in Baltimore, where he earned his Ph.D...
calculations showed that an observer could see all the way around a planet nearly six times larger in radius than the Earth, with the same atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
as the Earth, because of looming.
Sinking
Sinking is the opposite of looming. In sinking, objects that are normally seen above the horizon appear to be less elevated, or may even disappear below the horizon. While with looming the curvature of the rays is increasing, sinking produces the opposite effect.In general looming is more noticeable than sinking because objects that get bigger stand out more than ones that get smaller.
Towering and stooping
Towering and stooping are more complex forms of atmospheric refraction than looming and sinking. While looming and sinking change the apparent elevation of an object, towering and stooping change the shape of the object itself. With towering, objects seem to be stretched; with stooping, objects appear shortened. The stretching and shortening of the objects are not symmetrical, and depends on the temperature profile of the atmosphere. The curvature of the rays changes more rapidly in some places because the temperature profileThermal profiling
A thermal profile is a complex set of time-temperature data typically associated with an objected heat up and cool down. The thermal profile is often measured along a variety of dimensions such as slope, soak, time above liquidus , and peak....
is curved.
Image example and explanation
These images were taken from the same place on different days under different atmospheric conditions. The top frame shows looming. The island shape is not distorted, but is elevated. The middle frame shows looming with towering. The lowest frame is 5-image superior mirage of the islands. The uppermost image is stooped severely. As it is clearly seen from the image, the different refraction phenomena do not exclude each other, and may be present together, depending on atmospheric conditions.External links
See also
- MirageMirageA mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. The word comes to English via the French mirage, from the Latin mirare, meaning "to look at, to wonder at"...
- Mirage of astronomical objectsMirage of astronomical objectsA mirage of an astronomical object is a naturally occurring optical phenomenon, in which light rays are bent to produce distorted or multiple images of an astronomical object. The mirages might be observed for such astronomical objects as the Sun, the Moon, the planets, bright stars and very...
- Fata Morgana (mirage)Fata Morgana (mirage)A Fata Morgana is an unusual and very complex form of mirage, a form of superior mirage, which, like many other kinds of superior mirages, is seen in a narrow band right above the horizon...