Standardized Kt/V: Difference between revisions
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A '''square degree''' is a non-[[SI]] [[Units of measurement|unit]] measure of [[solid angle]]. It is denoted in various ways, including '''deg<sup>2</sup>''', '''sq.deg.''', (°)², and ☐°. Just as [[degree (angle)|degree]]s 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)<sup>2</sup>, or about 1/3283 or 3.0462{{e|-4}} [[steradian]] (0.30462 msr). The number of square degrees in a whole sphere is | |||
: <math>4 \pi \left(\frac{180}{\pi}\right)^2 = \frac{129\,600}{\pi},</math> | |||
or approximately 41 253 deg<sup>2</sup>. This is the total area of the 88 constellations in the [[list of constellations by area]]. The largest constellation, [[Hydra (constellation)|Hydra]] covers a solid angle of 1303 deg<sup>2</sup>, whereas the smallest, [[Crux]] covers 68 deg<sup>2</sup>.<ref>[http://calgary.rasc.ca/constellation.htm#list RASC Calgary Centre - The Constellations]</ref> | |||
For example, observed from the surface of the [[Earth]], the [[sun]] or the [[Moon|full moon]] has a diameter of approximately 0.5°, so it covers a solid angle of approximately 0.2 deg<sup>2</sup> (≈ ''π'' ({{sfrac|0.5|2}})<sup>2</sup> deg<sup>2</sup>), which is 4.8 × 10<sup>−6</sup> of the total sky sphere. | |||
Assuming the Earth to be a sphere with a surface area of 510 000 000 km<sup>2</sup>, the area of [[Northern Ireland]], 13 600 km<sup>2</sup> represents a solid angle of 1.10 deg<sup>2</sup>.<ref>[http://www.ons.gov.uk/ons/rel/regional-trends/region-and-country-profiles/key-statistics-and-profiles---august-2012/key-statistics---northern-ireland--august-2012.html Country Profiles: Key Statistics - Northern Ireland, August 2012]</ref> Similarly, the area of [[Connecticut]], 14 356 km<sup>2</sup> represents a solid angle of 1.16 deg<sup>2</sup>.<ref>[http://m.usembassy.gov/67133/show/48cfb5952231d07616e065c4e972a2b4&t=3854e8b8732893e84a65c8b81e3312c1 The 50 States | Embassies & Consulates Directory]</ref> | |||
==References== | |||
<References/> | |||
==External links== | |||
* http://calgary.rasc.ca/constellation.htm#square | |||
{{DEFAULTSORT:Square Degree}} | |||
[[Category:Units of angle]] | |||
Revision as of 10:06, 30 January 2014
A square degree is a non-SI unit measure of solid angle. It is denoted in various ways, including deg2, sq.deg., (°)², and ☐°. 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 or 3.0462Template:E steradian (0.30462 msr). 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. The largest constellation, Hydra covers a solid angle of 1303 deg2, whereas the smallest, Crux covers 68 deg2.[1]
For example, observed from the surface of the Earth, the sun or the full moon has a diameter of approximately 0.5°, so it covers a solid angle of approximately 0.2 deg2 (≈ π (Electrical Engineer Stephan from Merrickville-Wolford, likes to spend time body building, property developers ec in singapore singapore and storytelling. Gets inspiration through travel and just spent 6 days at Würzburg Residence with the Court Gardens.)2 deg2), which is 4.8 × 10−6 of the total sky sphere.
Assuming the Earth to be a sphere with a surface area of 510 000 000 km2, the area of Northern Ireland, 13 600 km2 represents a solid angle of 1.10 deg2.[2] Similarly, the area of Connecticut, 14 356 km2 represents a solid angle of 1.16 deg2.[3]