A square degree is a non-SI unit measure of solid angle. It is denoted in various ways, including deg2, sq.deg. and (°)². Just as degrees are used to measure parts of a circle, square degrees are used to measure parts of a sphere. Analogous to one degree being equal to π /180 radians, a square degree is equal to (π /180)2 or about 1/3283 steradian. The number of square degrees in a whole sphere is
or approximately 41 253 deg2. This is the total area of the 88 constellations in the list of constellations by area.
For example, observed from the surface of the Earth, the Moon has a diameter of approximately 0.5°, so it covers a solid angle of approximately 0.196 deg2, which is 4.8 × 10−6 of the total sky sphere.
Famous quotes containing the words square and/or degree:
“The square dance fiddler’s first concern is to carry a tune, but he must carry it loud enough to be heard over the noise of stamping feet, the cries of the “caller,” and the shouts of the dancers. When he fiddles, he “fiddles all over”; feet, hands, knees, head, and eyes are all busy.”
—State of Oklahoma, U.S. public relief program (1935-1943)
“It is a secret from nobody that the famous random event is most likely to arise from those parts of the world where the old adage “There is no alternative to victory” retains a high degree of plausibility.”
—Hannah Arendt (1906–1975)