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:
“If the physicians had not their cassocks and their mules, if the doctors had not their square caps and their robes four times too wide, they would never had duped the world, which cannot resist so original an appearance.”
—Blaise Pascal (1623–1662)
“Essential truth, the truth of the intellectualists, the truth with no one thinking it, is like the coat that fits tho no one has ever tried it on, like the music that no ear has listened to. It is less real, not more real, than the verified article; and to attribute a superior degree of glory to it seems little more than a piece of perverse abstraction-worship.”
—William James (1842–1910)