Illusion Proof
There is a widespread misconception, dating back at least to the time of Aristotle (4th century BC), that the larger size of the Moon near the horizon is due to the magnification effect created by the Earth's atmosphere. However, astronomical refraction near the horizon only slightly reduces the observed size, making the Moon slightly flattened along the vertical axis.
At the moment, there is no agreement on whether the Moon appears larger near the horizon - due to a larger perceived angular size or because of a larger perceived physical size, that is, whether it appears as being closer or as having increased in size.
In general, a complete explanation of this feature of human perception still does not exist. In 2002, Helen Ross and Cornelis Plag published The Riddle of the Lunar Illusion, in which, after reviewing various theories, they concluded: "No theory has won." The authors of the collection "Moon Illusion", published in 1989 under the editorship of M. Hershenson, came to the same decision.
There are many different theories to explain the moon illusion. Listed below are just the main ones.
Theory on the role of eye convergence
In the 1940s, Boring (1943; Holway & Boring, 1940; Taylor & Boring, 1942) and in the 1990s Suzuki (1991, 1998) proposed an explanation for the moon illusion, according to which the apparent magnitude of the moon depends on the degree convergence of the observer's eyes. That is, the illusion of the moon is the result of an increase in the impulses to convergence of the eyes that arise in the observer when he looks up (to look at the moon at the zenith), and the eyes themselves tend to diverge. Because eye convergence is one of the hallmarks of an object's proximity, it appears to an observer that an object high in the sky is smaller.
In one experiment, Holway and Boring (1940) asked subjects to compare their perceived magnitude of the moon to one of the light discs projected onto a screen next to them. In the first series of the experiment, the subjects sat on a chair. Observing the Moon near the horizon (at the level of the observer's eyes), they chose a disk that was much larger than the one they chose when they were observing the Moon at the zenith (raising their eyes at an angle of 30 °). In the second series, the subjects watched the moon while lying on the table. When they lay on their backs and looked at the Moon at its zenith, or when they were forced to tilt their heads back and lift their eyes up to see the Moon on the horizon from their supine position, the results were opposite. The moon near the horizon seemed to them smaller in size than the moon at its zenith.
Opponents of this hypothesis argue that the illusion of an enlarged Moon quickly fades with an increase in the height of the luminary above the horizon, when the need to throw back the head and raise the eyes up does not yet arise.
The theory of apparent remoteness
The theory of apparent remoteness was first described by Cleomedes around 200 AD. e. The theory suggests that the Moon at the horizon looks larger than the Moon in the sky due to the fact that it appears farther away. The human brain sees the sky not as a hemisphere, which it really is, but as a flattened dome. Watching clouds, birds and planes, a person sees that they decrease as they approach the horizon. Unlike terrestrial objects, the Moon, being near the horizon, has approximately the same apparent angular diameter as at the zenith, but human brain attempts to compensate for perspective distortion and suggests that the Moon's disk must be physically larger.
Experiments conducted in 1962 by Kaufman and Rock (Kaufman & Rock) showed that visual landmarks are an important factor in creating the illusion (see the Ponzo illusion). The moon near the horizon is at the end of the sequence of landscape objects, trees and buildings, which tells the brain about its great remoteness. As landmarks are removed from view, the large-looking Moon becomes smaller.
Opponents of this theory point to the presence of an illusion even when observing a star through a dark light filter, when the objects surrounding it are indistinguishable.
Relative size theory
According to the theory of relative size, the perceived size depends not only on the size on the retina, but also on the size of other objects in the field of view, which we observe simultaneously. When observing the Moon close to the horizon, we see not only the Moon, but also other objects, against which the Earth's satellite seems larger than it really is. When the Moon is in the sky, the vast expanses of the sky make it look smaller.
This effect was demonstrated by the psychologist Hermann Ebbinghaus. The circle surrounded by small circles represents the Moon at the horizon and surrounding small objects (trees, poles, etc.), while the circle surrounded by larger objects represents the Moon in the sky. While both center circles are the same size, many people think the right circle is larger in the picture. Everyone can check this effect by taking some large object (for example, a table) out of the room into the courtyard. In open space, it will look clearly smaller than indoors.
Opponents of this theory point out that aircraft pilots also observe this illusion, although there are no ground objects in their field of view.
Quantitative comparison of various theories according to experimental data
Specially designed experiments allowed quantitatively compare impact various factors offered to explain the illusion. In particular, raise the observer's head(the theory of the role of eye convergence) affects the size change, but very weakly (apparent size change - 1.04 times), the change colors or brightness of the lunar disk practically does not affect the apparent size, and presence of a horizon line or its optical model (the theory of apparent remoteness and relative size) leads to an apparent change in the size of the disk by 1.3 - 1.6 times, and the exact amount of change depends on the features of the landscape.
Notes
Links
- NASA - Solstice Moon Illusion
- Astronomy Picture of the Day (English) (September 26, 2007). Retrieved December 9, 2012.
- The Moon Illusion, An Unsolved Mystery. (English)
- The Moon Illusion Explained
| Moon | ||
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| Peculiarities |  |
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| Orbit | ||
| Surface | ||
| Selenology | ||
| Study | ||
| Other | ||
Wikimedia Foundation. 2010 .
Evidence of the phenomenon has been preserved since ancient times and recorded in various sources of human culture (for example, in chronicles). There are currently several different theories to explain this illusion.
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A widespread misconception that has existed since at least the time of Aristotle (4th century BC) is that the larger size of the Moon near the horizon is due to the increase created by the Earth's atmosphere. In fact, astronomical refraction near the horizon, on the contrary, slightly reduces the observed vertical size of the Moon and does not affect the horizontal size. As a result, the lunar disk near the horizon is seen flattened.
There is another factor due to which the angular size of the Moon near the horizon is slightly less than when it is at its zenith. With the movement of the Moon from the zenith to the horizon, the distance from it to the observer increases by the value of the earth's radius, and its apparent size decreases by 1.7%.
In addition, the angular size of the Moon changes slightly depending on its position in its orbit. Since its orbit is noticeably elongated, at perigee (the point of the orbit closest to the Earth), the angular size of the Moon is 33.5 arc minutes, and at apogee it is 12% less (29.43 arc minutes). These minor changes are not related to the apparent multiple increase of the Moon near the horizon: it is a perceptual error. Theodolite measurements and photographs of the Moon at different heights above the horizon show the same size, about half a degree, and the projection of the lunar disk on the retina of the observer's naked eye always has a size of about 0.15 mm.
The easiest way to demonstrate the illusory nature of the effect is to hold a small object (such as a coin) at arm's length while covering one eye. Comparing the size of an object with a large moon near the horizon and a small moon high in the sky, one can see that the relative size does not change. You can also make a pipe out of a sheet of paper and look through it only at the Moon, without surrounding objects - the illusion will disappear.
Possible explanations for the illusion
The size of an object we see can be determined either through its angular size (the angle formed by the rays entering the eye from the edges of the object) or through its physical size (actual size, for example, in meters). These two concepts differ from the point of view of human perception. For example, the angular dimensions of two identical objects placed at a distance of 5 and 10 meters from the observer differ by almost two times, however, as a rule, it does not seem to us that the nearest object is twice as large. Conversely, if a more distant object has the same angular size as a closer one, we will perceive it as twice as large (Emmert's law).
At the moment, there is no agreement on whether the Moon appears larger near the horizon - due to a larger perceived angular size or due to a larger perceived physical size, that is, whether it seems to be closer or increased in size.
In general, a complete explanation of this feature of human perception still does not exist. In 2002, Helen Ross and Cornelis Plag published The Riddle of the Lunar Illusion, in which, after considering various theories, they concluded: "No theory has won." The authors of the collection "Moon Illusion", published in 1989 under the editorship of M. Hershenson, came to the same decision.
There are many different theories to explain the moon illusion. Listed below are just the main ones.
Theory on the role of eye convergence
In the 1940s, Boring (1943; Holway & Boring, 1940; Taylor & Boring, 1942) and in the 1990s Suzuki (1991, 1998) proposed an explanation for the moon illusion, according to which the apparent magnitude of the moon depends on the degree convergence of the observer's eyes. That is, the illusion of the moon is the result of an increase in the impulses to convergence of the eyes that arise in the observer when he looks up (to look at the moon at the zenith), and the eyes themselves tend to diverge. Because eye convergence is one of the hallmarks of an object's proximity, it appears to an observer that an object high in the sky is smaller.
In one experiment, Holway and Boring (1940) asked subjects to compare their perceived magnitude of the moon to one of the light discs projected onto a screen next to them. In the first series of the experiment, the subjects sat on a chair. Observing the Moon near the horizon (at the level of the observer's eyes), they chose a disk that was much larger than the one they chose when they were observing the Moon at the zenith (raising their eyes at an angle of 30 °). In the second series, the subjects watched the moon while lying on the table. When they lay on their backs and looked at the Moon at its zenith, or when they were forced to tilt their heads back and lift their eyes up to see the Moon on the horizon from their supine position, the results were opposite. The moon near the horizon seemed to them smaller in size than the moon at its zenith.
Opponents of this hypothesis argue that the illusion of an enlarged Moon quickly fades with an increase in the height of the luminary above the horizon, when the need to throw back the head and raise the eyes up does not yet arise.
The theory of apparent remoteness
The theory of apparent remoteness was first described by Cleomedes around 200 AD. e. The theory suggests that the Moon at the horizon looks larger than the Moon in the sky due to the fact that it appears farther away. The human brain sees the sky not as a hemisphere, which it really is, but as a flattened dome. Watching clouds, birds and planes, a person sees that they decrease as they approach the horizon. Unlike terrestrial objects, the Moon, when near the horizon, has approximately the same apparent angular diameter as at the zenith, but the human brain tries to compensate for perspective distortions and assumes that the Moon's disk must be physically larger.
Experiments conducted in 1962 by Kaufman and Rock (Kaufman & Rock) showed that visual landmarks are an important factor in creating the illusion (see the Ponzo illusion). The moon near the horizon is at the end of the sequence of landscape objects, trees and buildings, which tells the brain about its great remoteness. As landmarks are removed from view, the large-looking Moon becomes smaller.
Opponents of this theory point to the presence of an illusion even when observing a star through a dark light filter, when the objects surrounding it are indistinguishable.
Relative size theory
According to the theory of relative size, the perceived size depends not only on the size on the retina, but also on the size of other objects in the field of view that we observe simultaneously. When observing the Moon close to the horizon, we see not only the Moon, but also other objects, against which the Earth's satellite seems larger than it really is. When the Moon is in the sky, the vast expanses of the sky make it look smaller.
This effect was demonstrated by the psychologist Hermann Ebbinghaus. The circle surrounded by small circles represents the Moon at the horizon and surrounding small objects (trees, poles, etc.), while the circle surrounded by larger objects represents the Moon in the sky. While both center circles are the same size, many people think the right circle is larger in the picture. Everyone can check this effect by taking some large object (for example, a table) out of the room into the courtyard. In open space, it will look clearly smaller than indoors.
Opponents of this theory point out that aircraft pilots also observe this illusion, although there are no ground objects in their field of view.
Quantitative comparison of various theories according to experimental data
Specially designed experiments allowed quantitatively compare the effects of various factors that have been proposed to explain the illusion. In particular, raise the observer's head(the theory of the role of eye convergence) affects the size change, but very weakly (apparent size change - 1.04 times), the change colors or brightness of the lunar disk practically does not affect the apparent size, and presence of a horizon line or its optical model (the theory of apparent remoteness and relative size) leads to an apparent change in the size of the disk by 1.3 - 1.6 times, and the exact amount of change depends on the features of the landscape.
). In fact, the angular size of the Moon is practically independent of its height above the horizon. The illusion also arises when observing the Sun and constellations. Evidence of the phenomenon has been preserved since ancient times and recorded in various sources of human culture (for example, in chronicles). There are currently several different theories to explain this illusion.
Illusion Proof
There is a widespread misconception, dating back at least to the time of Aristotle (4th century BC), that the larger size of the Moon near the horizon is due to the increase created by the Earth's atmosphere. In fact, astronomical refraction near the horizon, on the contrary, slightly reduces the observed vertical size of the Moon and does not affect the horizontal size. As a result, the lunar disk near the horizon is seen flattened.
There is another factor due to which the angular size of the Moon near the horizon is slightly less than when it is at its zenith. With the movement of the Moon from the zenith to the horizon, the distance from it to the observer increases by the value of the earth's radius, and its apparent size decreases by 1.7%.
In addition, the angular size of the Moon changes slightly depending on its position in its orbit. Since its orbit is noticeably elongated, at perigee (the point of the orbit closest to the Earth), the angular size of the Moon is 33.5 arc minutes, and at apogee - 12% less (29.43 arc minutes). These minor changes are not related to the apparent multiple increase of the Moon near the horizon: it is a perceptual error. Measurements with theodolite and photographs of the Moon at different heights above the horizon show a constant size, about half a degree, and the projection of the lunar disk on the retina of the observer's naked eye always has a size of about 0.15 mm.
The easiest way to demonstrate the illusory nature of the effect is to hold a small object (such as a coin) at arm's length while covering one eye. Comparing the size of an object with a large moon near the horizon and a small moon high in the sky, one can see that the relative size does not change. You can also make a pipe out of a sheet of paper and look through it only at the Moon, without surrounding objects - the illusion will disappear.
Possible explanations for the illusion
The size of an object we see can be determined either through its angular size (the angle formed by the rays entering the eye from the edges of the object) or through its physical size (actual size, for example, in meters). These two concepts differ from the point of view of human perception. For example, the angular dimensions of two identical objects placed at a distance of 5 and 10 meters from the observer differ by almost two times, however, as a rule, it does not seem to us that the nearest object is twice as large. Conversely, if a more distant object has the same angular size as a closer one, we will perceive it as twice as large (Emmert's law).
At the moment, there is no agreement on whether the Moon appears larger near the horizon - due to a larger perceived angular size or due to a larger perceived physical size, that is, whether it seems to be closer or increased in size.
In general, a complete explanation of this feature of human perception still does not exist. In 2002, Helen Ross and Cornelis Plag published The Riddle of the Lunar Illusion, in which, after reviewing various theories, they concluded: "No theory has won." The authors of the collection "Moon Illusion", published in 1989 under the editorship of M. Hershenson, came to the same decision.
There are many different theories to explain the moon illusion. Listed below are just the main ones.
Theory on the role of eye convergence
In the 1940s, Boring (1943; Holway & Boring, 1940; Taylor & Boring, 1942) and in the 1990s Suzuki (1991, 1998) proposed an explanation for the moon illusion, according to which the apparent magnitude of the moon depends on the degree convergence of the observer's eyes. That is, the illusion of the moon is the result of an increase in the impulses to convergence of the eyes that arise in the observer when he looks up (to look at the moon at the zenith), and the eyes themselves tend to diverge. Because eye convergence is one of the hallmarks of an object's proximity, it appears to an observer that an object high in the sky is smaller.
In one experiment, Holway and Boring (1940) asked subjects to compare their perceived magnitude of the moon to one of the light discs projected onto a screen next to them. In the first series of the experiment, the subjects sat on a chair. Observing the Moon near the horizon (at the level of the observer's eyes), they chose a disk that was much larger than the one they chose when they were observing the Moon at the zenith (raising their eyes at an angle of 30 °). In the second series, the subjects watched the moon while lying on the table. When they lay on their backs and looked at the Moon at its zenith, or when they were forced to tilt their heads back and lift their eyes up to see the Moon on the horizon from their supine position, the results were opposite. The moon near the horizon seemed to them smaller in size than the moon at its zenith.
Opponents of this hypothesis argue that the illusion of an enlarged Moon quickly fades with an increase in the height of the luminary above the horizon, when the need to throw back the head and raise the eyes up does not yet arise.
The theory of apparent remoteness
The theory of apparent remoteness was first described by Cleomedes around 200 AD. e. The theory suggests that the Moon at the horizon looks larger than the Moon in the sky due to the fact that it appears farther away. The human brain sees the sky not as a hemisphere, which it really is, but as a flattened dome. Watching clouds, birds and planes, a person sees that they decrease as they approach the horizon. Unlike terrestrial objects, the Moon, when near the horizon, has approximately the same apparent angular diameter as at the zenith, but the human brain tries to compensate for perspective distortions and assumes that the Moon's disk must be physically larger.
Experiments conducted in 1962 by Kaufman and Rock (Kaufman & Rock) showed that visual landmarks are an important factor in creating the illusion (see the Ponzo illusion). The moon near the horizon is at the end of the sequence of landscape objects, trees and buildings, which tells the brain about its great remoteness. As landmarks are removed from view, the large-looking Moon becomes smaller.
Opponents of this theory point to the presence of an illusion even when observing a star through a dark light filter, when the objects surrounding it are indistinguishable.
Relative size theory
According to the theory of relative size, the perceived size depends not only on the size on the retina, but also on the size of other objects in the field of view, which we observe simultaneously. When observing the Moon close to the horizon, we see not only the Moon, but also other objects, against which the Earth's satellite seems larger than it really is. When the Moon is in the sky, the vast expanses of the sky make it look smaller.
This effect was demonstrated by the psychologist Hermann Ebbinghaus. The circle surrounded by small circles represents the Moon at the horizon and surrounding small objects (trees, poles, etc.), while the circle surrounded by larger objects represents the Moon in the sky. While both center circles are the same size, many people think the right circle is larger in the picture. Everyone can check this effect by taking some large object (for example, a table) out of the room into the courtyard. In open space, it will look clearly smaller than indoors.
Opponents of this theory point out that aircraft pilots also observe this illusion, although there are no ground objects in their field of view.
Quantitative comparison of various theories according to experimental data
Specially designed experiments allowed quantitatively compare the effects of various factors that have been proposed to explain the illusion. In particular, raise the observer's head(the theory of the role of eye convergence) affects the size change, but very weakly (apparent size change - 1.04 times), the change colors or brightness of the lunar disk practically does not affect the apparent size, and presence of a horizon line or its optical model (the theory of apparent remoteness and relative size) leads to an apparent change in the size of the disk by 1.3 - 1.6 times, and the exact amount of change depends on the features of the landscape.
Illusion Proof
A widespread misconception that has existed at least since Aristotle (4th century BC e.), which consists in the fact that the larger size of the Moon near the horizon is explained by the effect increase, which is created Earth's atmosphere. However, astronomical refraction at the horizon only slightly reduces observed size making the moon slightly flattened along the vertical axis.
At the moment, there is no agreement on whether the Moon appears larger near the horizon - due to a larger perceived angular size or because of a larger perceived physical size, that is, whether it appears as being closer or as having increased in size.
In general, a complete explanation of this feature of the human perception still does not exist. IN 2002 Helen Ross and Cornelis Plag published The Riddle of the Lunar Illusion, in which, after considering various theories, they concluded: "No theory has won." The same decision was made by the authors of the collection "Moon Illusion", published in 1989 edited by M. Hershenson.
There are many different theories to explain the moon illusion. Listed below are just the main ones.
Theory on the role of eye convergence
In the 1940s, Boring (1943; Holway & Boring, 1940; Taylor & Boring, 1942) and in the 1990s Suzuki (1991, 1998) proposed an explanation for the moon illusion, according to which the apparent magnitude of the moon depends on the degree convergence the eye of the observer. That is, the illusion of the moon is the result of an increase in the impulses for convergence of the eyes that occur in the observer when he looks up (to look at the moon in zenith), and the eyes themselves tend to diverge. Because eye convergence is one of the hallmarks of an object's proximity, it appears to an observer that an object high in the sky is smaller.
In one experiment, Holway and Boring (1940) asked subjects to compare their perceived magnitude of the moon to one of the light discs projected onto a screen next to them. In the first series of the experiment, the subjects sat on a chair. Observing the Moon near the horizon (at the level of the observer's eyes), they chose a disk that was much larger than the one they chose when they were observing the Moon at the zenith (raising their eyes at an angle of 30 °). In the second series, the subjects watched the moon while lying on the table. When they lay on their backs and looked at the Moon at its zenith, or when they were forced to tilt their heads back and lift their eyes up to see the Moon on the horizon from their supine position, the results were opposite. The moon near the horizon seemed to them smaller in size than the moon at its zenith.
Opponents of this hypothesis argue that the illusion of an enlarged Moon quickly fades with an increase in the height of the luminary above the horizon, when the need to throw back the head and raise the eyes up does not yet arise.
The theory of apparent remoteness
The theory of apparent remoteness was first described by Cleomedes around 200 AD e. The theory suggests that the Moon at the horizon looks larger than the Moon in the sky due to the fact that it appears farther away. The human brain sees the sky not as a hemisphere, which it really is, but as a flattened dome. Watching clouds, birds and planes, a person sees that they decrease as they approach the horizon. Unlike terrestrial objects, the Moon, being near the horizon, has approximately the same apparent angular diameter as in zenith, but the human brain tries to compensate promising distortion and suggests that the disk of the moon must be physically larger.
Experiments carried out in 1962 Kaufman and Rock (Kaufman & Rock), showed that visual landmarks are an essential factor in creating the illusion (see. illusion ponzo). The moon near the horizon is at the end of the sequence of objects landscape, trees and buildings, which tells the brain about its great remoteness. As landmarks are removed from view, the large-looking Moon becomes smaller.
Opponents of this theory point to the presence of an illusion even when observing a star through a dark light filter, when the objects surrounding it are indistinguishable.
Relative size theory
According to the theory of relative size, the perceived size depends not only on the size on the retina, but also on the size of other objects in the line of sight that we observe at the same time. When observing the Moon close to the horizon, we see not only the Moon, but also other objects, against which the Earth's satellite seems larger than it actually is. When the Moon is in the sky, the vast expanses of the sky make it look smaller.
This effect has been demonstrated by psychologist Herman Ebbinghaus. The circle surrounded by small circles represents the Moon at the horizon and surrounding small objects (trees, poles, etc.), while the circle surrounded by larger objects represents the Moon in the sky. While both center circles are the same size, many people think the right circle is larger in the picture. Everyone can check this effect by taking some large object (for example, a table) out of the room into the courtyard. In open space, it will look clearly smaller than indoors.
Opponents of this theory point out that aircraft pilots also observe this illusion, although there are no ground objects in their field of view.
Quantitative comparison of various theories according to experimental data
Specially designed experiments allowed quantitatively compare the effects of various factors that have been proposed to explain the illusion. In particular, raise the observer's head(the theory of the role of eye convergence) affects the size change, but very weakly (apparent size change - 1.04 times), the change colors or brightness of the lunar disk practically does not affect the apparent size, and presence of a horizon line or its optical model (the theory of apparent remoteness and relative size) leads to an apparent change in the size of the disk by 1.3 - 1.6 times, and the exact amount of change depends on the features of the landscape.
Notes
Links
- NASA - Solstice Moon Illusion
- Astronomy Picture of the Day (English) (September 26, 2007). Retrieved December 9, 2012.
- The Moon Illusion, An Unsolved Mystery. (English)
- The Moon Illusion Explained
Moon Peculiarities Orbit Surface Selenology Study Other Wikimedia Foundation. 2010 .
