- published: 15 Sep 2015
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An ocean (from Ancient Greek Ὠκεανὸς (Okeanos); the World Ocean of classical antiquity) is a body of saline water that composes a large part of a planet's hydrosphere. In the context of Earth, it also refers to major divisions of the planet's World Ocean, such as the Atlantic Ocean. The word "sea" is often used interchangeably with "ocean", but a sea is a body of saline water (possibly a division of the World Ocean) in a more inland location.
Earth's global ocean is the largest confirmed surface ocean on all observable planets. Approximately 71% of the planet's surface (~3.6x108 km2) is covered by saline water that is customarily divided into several principal oceans and smaller seas. Because it is the principal component of Earth's hydrosphere, the world ocean is integral to all known life, forms part of the carbon cycle, and influences climate and weather patterns. The total volume is approximately 1.3 billion cubic kilometres (310 million cu mi) with an average depth of 3,790 metres (12,430 ft). It is the habitat of 230,000 species known to science, however much of the ocean's depths remain unexplored and it is estimated that over two million marine species may exist. The origin of Earth's oceans is still unknown though they are believed to have first appeared in the Hadean period and may have been the point of origin for the emergence of life.
Documentary films constitute a broad category of nonfictional motion pictures intended to document some aspect of reality, primarily for the purposes of instruction or maintaining a historical record. A 'documentary film' was originally shot on film stock — the only medium available — but now includes video and digital productions that can be either direct-to-video, made as a television program or released for screening in cinemas. "Documentary" has been described as a "filmmaking practice, a cinematic tradition, and mode of audience reception" that is continually evolving and is without clear boundaries.
In popular myth, the word 'documentary' was coined by Scottish documentarian John Grierson in his review of Robert Flaherty's film Moana (1926), published in the New York Sun on 8 February 1926, written by "The Moviegoer" (a pen name for Grierson).
Grierson's principles of documentary were that cinema's potential for observing life could be exploited in a new art form; that the "original" actor and "original" scene are better guides than their fiction counterparts to interpreting the modern world; and that materials "thus taken from the raw" can be more real than the acted article. In this regard, Grierson's definition of documentary as "creative treatment of actuality" has gained some acceptance, with this position at variance with Soviet film-maker Dziga Vertov's provocation to present "life as it is" (that is, life filmed surreptitiously) and "life caught unawares" (life provoked or surprised by the camera).