Top Document: [sci.astro] Solar System (Astronomy Frequently Asked Questions) (5/9) Previous Document: E.14 Earth-Moon system Next Document: E.14.2 Why does the Moon always show the same face to the Earth? See reader questions & answers on this topic! - Help others by sharing your knowledge In fact the Moon *does* rotate: It rotates exactly once for every orbit it makes about the Earth. The fact that the Moon is rotating may seem counterintuitive: If it's always facing towards us, how can it be rotating at all? To see how this works, put two coins on a table, a large one to represent the Earth, and a small one to represent the Moon. Choose a particular place on the edge of the "Moon" as a reference point. Now, move the Moon around the Earth in a circle, but be careful to always keep the spot you picked pointed at the Earth (this is analogous to the Moon always keeping the same face pointed at the Earth). You should notice that as you do this, you have to slowly rotate the Moon as it circles the Earth. By the time the Moon coin goes once around the Earth coin, you should have had to rotate the Moon exactly once. This exact equality between the Moon's rotation period and orbital period is sometimes seen as a fantastic coincidence, but, in fact, there is a physical process which slowly changes the rotation period until it matches the orbital period. See the next entry. User Contributions:Top Document: [sci.astro] Solar System (Astronomy Frequently Asked Questions) (5/9) Previous Document: E.14 Earth-Moon system Next Document: E.14.2 Why does the Moon always show the same face to the Earth? Part0 - Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Part8 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jlazio@patriot.net
Last Update March 27 2014 @ 02:11 PM
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