APSIS

Apsis

An apsis, plural apsides, is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system. Historically, in geocentric systems, apsides were measured from the center of the Earth.

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apsis

Noun

  1. A recess or projection, with a dome or vault, at the east end of a church; an apse.
  2. Either of the points in the elliptical orbit of a planet or comet where it is closest or furthest from the sun; perihelion or aphelion; an apside


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

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