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(1) Amir D Aczel, An Expedition Without End; Battling subzero temperatures, swarming mosquitoes and angry Inquisitors, all to find a single number. Wall Street Journal, June 27, 2011
http://online.wsj.com/article/SB10001424052702304186404576387761564776914.html
(book review on Larrie D. Ferreiro, Measure of the Earth; The Enlightenment Expedition that Reshaped the World. Basic Books, 2011)
Quote: "But Newton's recently published theory of mechanics indicated that a spinning Earth would look more like an apple, wider at the equator and flatter at the poles. Since the Earth's rotation is most pronounced at the equator, that part of the globe bulges the most—for the same reason that if you swing around a weight tied to a rubber band, the band will expand. Thus a degree of latitude there is smaller, in actual north-to-south distance, than a degree closer to one of the poles. (If the Earth were a perfect sphere, a degree of latitude would be everywhere equal.)
My comment: I did not know the eartyh is not a perfect sphere.
(a) Shape and Size of the Earth. Center for Aerospace Education, Windward Community College, University of Hawaii, undated.
http://aerospace.wcc.hawaii.edu/shape.html
* Mauna Kea
http://en.wikipedia.org/wiki/Mauna_Kea
(in Hawaii island; 4,205 m (13,796 ft) above sea level, its peak is the highest point in the state of Hawaii. However, much of the mountain is under water; when measured from its oceanic base, Mauna Kea is over 10,000 m (33,000 ft) tall—significantly taller than Mount Everest./ In Hawaiian, Mauna Kea means "white mountain",[32] a reference to its summit, which is usually snow-capped in winter)
(b) Definition and measurement of latitude:
"Latitude and longitude are angular measures: latitude tells us the angle to which a point is elevated above the plane of the equator, as measured from the center of the Earth; longitude tells us how far east or west of the prime meridian a point is (Figure 8). Note that while the equator is naturally defined by the Earth’s rotation, the prime meridian is arbitrary, so we must agree on a prime meridian before we can interpret the coordinates we are given."
Isaac Kunen, Introduction to Spatial Coordinate Systems: Flat Maps for a Round Planet. SQL Server Technical Article, July, 2008.
http://msdn.microsoft.com/en-us/library/cc749633(v=sql.100).aspx
(c)
"If the earth were a perfect sphere (which it isn’t), the distance, or the length, of 1o of latitude would be constant everywhere. In reality, the earth is slightly flattened at the poles, so the length of 1o of latitude at the poles is slightly more than at the equator. At the equator, the length of 1o of latitude is equal to 110.6 km (68.7 mi.) and at the poles, the length of 1o of latitude is equal to 111.7 km (69.4 mi.). For our purposes, we will assume the length of one degree of latitude is 111 km."
Latitude and Longitude Getting Started. Digital Mobile Map, Oct
http://www.digitalmobilemap.com/latitude-and-longitude-getting-started
Note:
(a) geodesy (n; Greek geōdaisia, from geō- ge- + daiesthai to divide):
"a branch of applied mathematics concerned with the determination of the size and shape of the earth and the exact positions of points on its surface and with the description of variations of its gravity field"
(b) expedient (n): "something done or used to achieve a particular end usually quickly or temporarily"
(c) colonial (n): "a member or inhabitant of a colony"
, which, I may add, is exactly the same as "colonist."
All definitions are from www.m-w.com.
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发表于 7-3-2011 10:06:01
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