ID | #1717689903 |
Added | Thu, 06/06/2024 |
Author | July N. |
Sources | Гумбольдт А. "Путешествие в равноденственные области Нового Света в I799-1804 г . г . " "Страны Центральной и Южной Америки
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Phenomena | |
Status | Hypothesis
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Initial data
CARIBBEAN SEA, 64 miles from Cape BEATA (island of HAITI).
ALEXANDER HUMBOLDT; several sailors.
At night I saw a very curious optical phenomenon, which I cannot explain. It was more than half past one, a light wind was blowing from the east, the thermometer rose to 23.2 degrees, the hygrometer with a whale's whisker showed 57%. I stayed on deck to watch the culmination of several big stars. The full moon was very high. Suddenly, in the direction of the Moon, 45 minutes before its passage through the meridian, a large arc of all colors of the spectrum was formed, but very gloomy rain; and most of all I was struck by the fact that I saw this phenomenon, completely similar to the lunar rainbow, not against the Moon. The arc remained stationary, or at least seemed so, for eight or ten minutes.
The moment I tried to check if her reflection would be visible in the sextant mirror, she began to move and descend, passing first past the Moon, just below it. It was 12:54 p.m. (true time) when the top of the arc disappeared over the horizon. (...)
Arago was kind enough to study the drawing of the arc that I made in the travel journal. He thinks that the reflection of the Moon in the water could not have given a halo of such a large size. No less difficult to explain this phenomenon, which deserves great attention, is the speed of its movement.
Hypotheses
Halo
Halo usually appears around the Sun or moon, sometimes around other powerful light sources such as street lights. There are many types of halos, but they are mostly caused by ice crystals in Cirrus clouds at a height of 5-10 km in the upper troposphere. The form of the observed halo depends on the shape and arrangement of crystals. Reflected and refracted by the ice crystals, the light often turns into a spectrum, which makes halo look like a rainbow, but a halo in low light has a low chroma, which is associated with the peculiarities of twilight vision.
Investigation
Resume
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