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While debating what became the Land Ordinance of 1785, Thomas Jefferson's committee wanted to divide the public lands in the west into "hundreds of ten geographical miles square, each mile containing 6,086 and 4-10ths of a foot" and "sub-divided into lots of one mile square each, or 850 and 4-10ths of an acre". [9]
1 square yoctometre (ym 2) 1 ym 2 10 −43 100,000 ym 2: 1 femtobarn [3] 10 −42: 1 square zeptometre (zm 2) 1 zm 2 10 −36: 1 square attometre (am 2) 1 am 2 10 −30: 1 square femtometre (fm 2) 1 fm 2 10 −29 66.52 fm 2: Thomson cross-section of the electron [4] 10 −28 100 fm 2: 1 barn, roughly the cross-sectional area of a uranium ...
A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute ( 1 / 60 of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).
[1] This diagram gives a visual analogue using a square: regardless of the size of the square, the added perimeter is the sum of the four blue arcs, a circle with the same radius as the offset. More formally, let c be the Earth's circumference, r its radius, Δc the added string length and Δr the added radius.
Leonardo da Vinci drew the Vitruvian Man within a square of side 1.83 m (6 ft 0 in) and a circle about 1.2 m (3 ft 11 in) in radius. To help compare different orders of magnitude, this section lists lengths between one meter and ten meters. Light, in vacuum, travels 1 meter in 1 ⁄ 299,792,458, or 3.3356409519815E-9 of a second.
Respectively, these square divisions of land are approximately 80 chains (one mile or 1.6 km), 40 chains (half a mile or 800 m), and 20 chains (a quarter mile or 400 m) on a side. The chain is still used in agriculture: measuring wheels with a circumference of 0.1 chain (diameter ≈ 2.1 ft or 64 cm) are still readily available in Canada and ...
Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).
[13] [14] The total water extraction from center-pivot irrigation in the area is estimated to be about 5.42 million acre-feet of water per year. [15] In 1950, irrigated cropland covered 100,000 hectares (250,000 acres). With the use of center-pivot irrigation, nearly 1.2 million hectares (3 million acres) of land were irrigated in Kansas alone.