Abstract
IT is a matter of common observation that when the sun is nearly on a level with the eye and is in the vicinity of the horizon its apparent size is greater than when high up in the sky. It is generally assumed that this is due to the circumstance that the features of the skyline provide a true standard of instinctive comparison which enables the eye to appreciate the angle subtended by the sun's disk. It is true that the linear magnitude of the terrestrial features is fairly well known and that the tone and other qualities of the horizon give an instinctive impression of its distance. The current explanation breaks down, however, under the test of actual measurement of the apparent magnitudes. These measurements are trustworthy only if made by an indirect method which sidetracks the critical faculty, for as soon as thought comes into play, the spontaneous impression of magnitude is impaired. The measurements in question have been made from a number of sketches which I have made during the last forty years, all drawn originally without measure-ment, or any intention of subsequent measurement, but from known view-points, so that the angular magnitudes of terrestrial features were afterwards ascertained from the map.
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Cornish, V. Apparent Enlargement of the Sun at the time of Rising and Setting. Nature 140, 1082–1083 (1937). https://doi.org/10.1038/1401082a0
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DOI: https://doi.org/10.1038/1401082a0