Pic de Finestrelles: Altitude and Location
Altitude: Pic de Finestrelles has an altitude of
2,826 metres (or
9,272 feet) above sea level
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Location: This mountain is situated in the
Oriental Pyrenees, straddling the border between
France and Spain
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. It is notable for its scenic views and is a popular destination for hikers and climbers.
Pic Gaspard: Altitude and Location
Altitude: Pic Gaspard stands at an impressive
3,883 meters (12,740 feet), making it one of the tallest peaks in the French Alps, specifically within the Massif des Écrins
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Location: The mountain is situated in the
Dauphine Alps, in the region of
Hautes-Alpes, France. It is part of the broader Provença-Alpes-Costa Azul area. This stunning peak is named after Pierre Gaspard, a renowned mountain guide known for his ascent of La Meije in 1877
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Understanding Atmospheric Refraction and Its Effect on Visibility
Atmospheric refraction is the bending of light as it passes through the Earth's atmosphere, which can significantly affect visibility. This phenomenon occurs due to variations in air density and temperature, which change the speed of light in the atmosphere.Key effects of atmospheric refraction on visibility include:
- Elevation of Objects: Atmospheric refraction allows objects that are actually below the horizon to become visible. This effect is particularly pronounced for celestial bodies like the Sun and stars, which can appear above the horizon even when they are technically below it. For instance, the Sun can be seen just before it rises and just after it sets due to this bending of light
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- Increased Range of Vision: In geodesy, atmospheric refraction is accounted for in calculations, which effectively increases the range of vision. This means that observers can see objects that are further away than they would under ideal conditions without atmospheric interference
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- Twinkling of Stars: The twinkling effect observed in stars is also a result of atmospheric refraction. As light from stars passes through varying layers of the atmosphere, it is refracted differently, causing the stars to appear to change brightness and position slightly
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- Temperature Influence: The degree of refraction is influenced by temperature changes. For example, a decrease in temperature can increase the amount of refraction by approximately 1% for every 3 °C drop, which can further affect visibility conditions
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- Color Dispersion: Atmospheric refraction can cause the light from stars to spread into a spectrum of colors, although this effect is more noticeable through telescopes
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Distance Between Pic de Finestrelles and Pic Gaspard
The distance between
Pic de Finestrelles in the Pyrenees and
Pic Gaspard in the Alps is approximately
443 kilometers. This remarkable distance is notable for being the longest line of sight ever photographed, achieved on July 16, 2016, by photographer Marc Bret
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.This impressive visibility is attributed to the heights of both peaks, with Pic de Finestrelles standing at 2,826 meters and Pic Gaspard at 3,883 meters, allowing for such a long sightline under the right atmospheric conditions
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Visibility Calculation
To determine if it's possible to observe Pic de Finestrelles from the summit of Pic Gaspard, we need to consider the Earth's curvature and the effect of atmospheric refraction.The geometric horizon distance for an observer at height hh above sea level can be calculated using the formula:d=2Rhd=2Rh
where RR is the Earth's radius (approximately 6,371 kilometers), and hh is the observer's height above sea level.
This formula gives the distance to the horizon assuming no atmospheric refraction. However, atmospheric refraction typically extends the visible horizon by about 13% beyond the geometric horizon. So, we adjust the horizon distance for refraction as:drefraction=d×(1+0.13)drefraction=d×(1+0.13)
The total visible distance between two points at different heights is the sum of their refracted horizon distances. If this total visible distance is greater than or equal to the actual distance between the two points, then one point should be visible from the other.
After performing these calculations, it is found that the total visible distance between Pic de Finestrelles and Pic Gaspard is indeed greater than the actual distance between them. Therefore, it is possible to observe Pic de Finestrelles from the summit of Pic Gaspard, taking into account the phenomenon of atmospheric refraction.