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:
“A man who is good enough to shed his blood for his country is good enough to be given a square deal afterwards. More than that no man is entitled to, and less than that no man shall have.”
—Theodore Roosevelt (1858–1919)
“The eloquence of one stimulates all the rest, some up to the speaking-point, and all others to a degree that makes them good receivers and conductors, and they avenge themselves for their enforced silence by increased loquacity on their return.”
—Ralph Waldo Emerson (1803–1882)