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The physical group size equivalent to m minutes of arc can be calculated as follows: group size = tan( m / 60 ) × distance. In the example previously given, for 1 minute of arc, and substituting 3,600 inches for 100 yards, 3,600 tan( 1 / 60 ) ≈ 1.047 inches. In metric units 1 MOA at 100 metres ≈ 2.908 centimetres.
The use of the parsec as a unit of distance follows naturally from Bessel's method, because the distance in parsecs can be computed simply as the reciprocal of the parallax angle in arcseconds (i.e.: if the parallax angle is 1 arcsecond, the object is 1 pc from the Sun; if the parallax angle is 0.5 arcseconds, the object is 2 pc away; etc.).
One acre equals 1 ⁄ 640 (0.0015625) square mile, 4,840 square yards, 43,560 square feet, [2] or about 4,047 square metres (0.4047 hectares) (see below).While all modern variants of the acre contain 4,840 square yards, there are alternative definitions of a yard, so the exact size of an acre depends upon the particular yard on which it is based.
Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).
minutes, (1 minute = 15/60 degrees = 1/4 of a degree = 15 arcminutes) and; seconds, (1 second = 15/3600 degrees = 1/240 of a degree = 15 arcseconds) This a fair thing to put in an article on arcminutes (or arcseconds for that matter).
An arcsecond is 1/3600th of one degree (1°) and a radian is 180/π degrees. So one radian equals 3,600 × 180/ arcseconds, which is about 206,265 arcseconds (1 rad ≈ 206,264.806247"). Therefore, the angular diameter of an object with physical diameter d at a distance D, expressed in arcseconds, is given by: [9]
1.6 × 10 −5 quectometers (1.6 × 10 −35 meters) – the Planck length (Measures of distance shorter than this do not make physical sense, according to current theories of physics.) 1 qm – 1 quectometer, the smallest named subdivision of the meter in the SI base unit of length, one nonillionth of a meter.
The acre is also commonly used to measure land areas, where 1 acre = 4,840 square yards = 43,560 square feet. An acre is approximately 40% of a hectare. On the atomic scale, area is measured in units of barns, such that: [13] 1 barn = 10 −28 square meters. The barn is commonly used in describing the cross-sectional area of interaction in ...