EPOCH

Epoch

In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as the celestial coordinates or elliptical orbital elements of a celestial body, because these are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit.

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epoch

Noun

  1. A particular period of history, especially one considered remarkable or noteworthy.
  2. A notable event which marks the beginning of such a period.
  3. A precise instant of time that is used as a reference point.
  4. A precise instant of time that is used as a reference point (e.g. January 1, 1970, 00:00:00 UTC).


The above text is a snippet from Wiktionary: epoch
and as such is available under the Creative Commons Attribution/Share-Alike License.

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