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A coordinate singularity (or coördinate singularity) occurs when an apparent singularity or discontinuity occurs in one coordinate frame, which can be removed by choosing a different frame. An example is the apparent (longitudinal) singularity at the 90 degree latitude in spherical coordinates. An object moving due north (for example, along the line 0 degrees longitude) on the surface of a sphere will suddenly experience an instantaneous change in longitude at the pole (i.e., jumping from longitude 0 to longitude 180 degrees). In fact, longitude is not uniquely defined at the poles. This discontinuity, however, is only apparent; it is an artifact of the coordinate system chosen, which is singular at the poles. A different coordinate system would eliminate the apparent discontinuity, e.g. by replacing latitude/longitude with n-vectors. Stephen Hawking aptly summed this up, when once asking the question "what's north of the north pole?".〔(What is Cosmology? ), wiseGEEK.com. Accessed 15 Feb 2013. In a related discussion, he mentions this again : (The Beginning of Time - Stephen Hawking ); accessed 15 Feb 2013.〕 ==See also== *Chronometric singularity *Imaginary time * Mathematical singularity * No-boundary proposal 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「coordinate singularity」の詳細全文を読む スポンサード リンク
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