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The 'Western Hemisphere', also 'Western hemisphere'^[1] or 'western hemisphere',^[2] is a geographical term for the half of the Earth that lies west of the Prime Meridian (which crosses Greenwich in London, England, United Kingdom), the other half being the eastern hemisphere.^[3] It is also used to specifically refer to the Americas (or the New World) and adjacent waters, while excluding other territories that lie geographically in the hemisphere (parts of Africa, Europe, Antarctica, and Asia); thus, it is sometimes referred to as the 'American hemisphere'.Olson, Judy M. "Projecting the hemisphere", ch. 4 from ''Matching the map projection to the need''; Robinson, Arthur H. & Snyder, John P., eds. 1997. Bethesda, MD: Cartography and Geographic Information Society, American Congress on Surveying and Mapping. ''Western hemisphere'' is sometimes used as an equivalent for the geopolitical construct, the ''Western World'', which typically includes the Americas and Europe.

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Overview

Sources

Overview

A hemisphere is a geometric term that literally means 'half sphere', and in geography the term is used when dividing the Earth into two halves. The most obvious dividing line is the equator, creating the northern and southern hemispheres. These hemispheres are based on unambiguous reference points — the north and south poles — which are defined by the Earth's axis of rotation and, in turn, define the equator.
Any definition of eastern and western hemispheres, however, requires the selection of an arbitrary meridian and a corresponding meridian on the other side of the Earth. The Prime Meridian at 0° longitude is typically used, which runs through Greenwich; this is used to define the International Date Line (or End Meridian) on the other side of the Earth at 180° longitude. In its proper geographic sense, the western hemisphere includes not only the Americas, but the western portions of Europe and Africa, the easternmost tip of Russia, numerous territories in Oceania, and a portion of Antarctica while excluding some of the Aleutian Islands to the southwest of the Alaskan mainland. Often, the meridians of 20° W and the diametrically opposed 160° E are used,^[4] which excludes the European and African mainlands but also excludes a small portion of northeast Greenland and includes more of eastern Russia and Oceania (e.g., New Zealand).

Sources

1. ''Oxford Dictionary of English'', 2nd ed., rev. 2006. London, UK: Oxford University Press, p. 2001.
2. ''Merriam Webster's Online Dictionary'' (based on Collegiate vol., 11th ed.) 2006. Springfield, MA: Merriam-Webster, Inc.
3. "Latitude and longitude" ''Encyclopædia Britannica''. 2006. Chicago: Encyclopædia Britannica, Inc.
4. "Western Hemisphere". ''Merriam-Webster's Geographical Dictionary,'' 3rd ed. 2001. Springfield, MA: Merriam-Webster, Inc., p. 1294.