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Astro*Dictionary by Michael Erlewine





4 articles for "Libration"

Libration [Astro*Index]

Variations in the Moon's orbit. Although the time of the Moon's rotation around its own axis is identical to the time of its rotation around the Earth in its orbit, we see a bit more than 50% of it, even though it only shows one side to us. To be exact, we see 59% of it. This is due to several complexities in its motion. These rockings in its orbit are called librations.

See also:
♦ Lunar ♦ Libration in Latitude ♦ Libration in Longitude
Libration [Munkasey M.]

The various movements or wobbles of the Moon which allowsobservers on the Earth to see 59"0 as opposed to the 501'a of its total surface which would normally be seen because its orbital motion tends to keep the same side constantly towards Earth.

See also:
♦ Lunar ♦ Libration in Latitude ♦ Libration in Longitude
Libration in Latitude [Astro*Index]

One of the complexities in the Moon's orbit. The Moon's axis is inclined at 6°05' to its orbit around the Earth, much as the Earth's axis is tilted in reference to the Ecliptic. Thus every two weeks, it presents an alternate pole to us. This vertical rocking is known as libration in latitude.

See also:
♦ Ecliptic ♦ Latitude
Libration in Longitude [Astro*Index]

A variation in the Moon's orbit that arises because bodies in an elliptical orbit have different speeds at different points in their orbit (Kepler's second law). The Moon speeds up at apogee, and we see a little more of its eastern side, and slows down at perigee, so we see a little more of its western side. This happens at two-week intervals.

See also:
♦ Kepler's Laws ♦ Elliptical Orbit ♦ Apogee


Astro*Index Copyright © 1997 Michael Erlewine


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