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Agricultural meteorology

Research of visual atmospheric phenomena[edit]

Twilight at Baker BeachSee also: Rainbow and Twilight

Ptolemy wrote on the atmospheric refraction of light in the context of astronomical observations.[12] In 1021, Alhazen showed that atmospheric refraction is also responsible for twilight; he estimated that twilight begins when the sun is 19 degrees below the horizon, and also used a geometric determination based on this to estimate the maximum possible height of the Earth’s atmosphere as 52,000 passim(about 49 miles, or 79 km).[13]

St. Albert the Great was the first to propose that each drop of falling rain had the form of a small sphere, and that this form meant that the rainbow was produced by light interacting with each raindrop.[14] Roger Bacon was the first to calculate the angular size of the rainbow. He stated that a rainbow summit can not appear higher than 42 degrees above the horizon.[15] In the late 13th century and early 14th century, Kamāl al-Dīn al-Fārisī and Theodoric of Freiberg were the first to give the correct explanations for the primary rainbow phenomenon. Theoderic went further and also explained the secondary rainbow.[16] In 1716, Edmund Halley suggested that aurorae are caused by “magnetic effluvia” moving along the Earth’s magnetic field lines.