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[[Image:CenitNadir.gif|right|250px]]

[[Image:CenitNadir.gif|right|250px]]

The '''nadir''' is the point on [[Earth]] directly beneath a [[satellite]], the opposite of [[zenith]]. Compare with [[subsatellite point]]. <ref> [http://earthobservatory.nasa.gov/Library/glossary.php3?mode=all NASA Earth Observatory glossary] </ref>

The '''nadir''' is the point on [[Earth]] directly beneath a [[satellite]], the opposite of [[zenith]]. Compare with [[subsatellite point]].<ref>[http://earthobservatory.nasa.gov/Library/glossary.php3?mode=all NASA Earth Observatory glossary]</ref>

'''Etymology:''' Middle English, from Middle French, from Arabic naḍhīr opposite  

'''Etymology:''' Middle English, from Middle French, from Arabic naḍhīr opposite  

Date: 15th century. <ref>[http://www.m-w.com/dictionary/nadir Nadir] Merriam-Webster Online Dictionary </ref>  

Date: 15th century.<ref>[http://www.m-w.com/dictionary/nadir Nadir] Merriam-Webster Online Dictionary</ref>