Appearance from Earth

Appearance from Earth
See also: Lunar phase, Earthshine, and Observing the Moon

The Moon has an exceptionally low albedo, giving it a similar reflectance to coal. Despite this, it is the second brightest object in the sky after the Sun.[39][nb 8] This is partly due to the brightness enhancement of the opposition effect; at quarter phase, the Moon is only one-tenth as bright, rather than half as bright, as at full Moon.[81] Additionally, colour constancy in the visual system recalibrates the relations between the colours of an object and its surroundings, and since the surrounding sky is comparatively dark, the sunlit Moon is perceived as a bright object. The edges of the full Moon seem as bright as the centre, with no limb darkening, due to the reflective properties of lunar soil, which reflects more light back towards the Sun than in other directions. The Moon does appear larger when close to the horizon, but this is a purely psychological effect, known as the Moon illusion, first described in the 7th century BC.[82]



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