单词 | physical libration |
释义 | physical librationphysical librationSlight variations in the Moon's rotation on its axis that are caused by minor irregularities in shape. They amount to less than two arc minutes but allow the Moon's principal moments of inertia, and hence the distribution of mass within the Moon, to be calculated. The mean orientation of the Moon with respect to its physical librations defines the Moon's prime meridian. See also libration. |
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