by APOD Robot » Sun Feb 05, 2012 5:06 am
Lunation
Explanation: Our Moon's appearance changes nightly.
This time-lapse sequence shows what our Moon looks like during a
lunation, a complete lunar cycle. As the
Moon orbits the
Earth, the half illuminated by the
Sun first becomes increasingly visible, then decreasingly visible. The
Moon always keeps the same face toward the Earth. The
Moon's apparent size changes slightly, though, and a slight wobble called a
libration is discernible as it progresses along its
elliptical orbit. During the cycle, sunlight reflects from the
Moon at different angles, and so illuminates different features differently. A full
lunation takes about 29.5 days, just under a month (moon-th).
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[url=http://apod.nasa.gov/apod/ap120205.html][img]http://apod.nasa.gov/apod/calendar/S_120205.jpg[/img] [size=150]Lunation[/size][/url]
[b] Explanation: [/b] Our Moon's appearance changes nightly. [url=http://www.astrosurf.com/cidadao/animations.htm]This time-lapse sequence[/url] shows what our Moon looks like during a [url=http://en.wikipedia.org/wiki/Lunation]lunation[/url], a complete lunar cycle. As the [url=http://www.nineplanets.org/luna.html]Moon[/url] orbits the [url=http://apod.nasa.gov/apod/ap070325.html]Earth[/url], the half illuminated by the [url=http://en.wikipedia.org/wiki/Sun]Sun[/url] first becomes increasingly visible, then decreasingly visible. The [url=http://en.wikipedia.org/wiki/Moon]Moon[/url] always keeps the same face toward the Earth. The [url=http://www.astronomycafe.net/qadir/amoonm.html]Moon[/url]'s apparent size changes slightly, though, and a slight wobble called a [url=http://en.wikipedia.org/wiki/Libration]libration[/url] is discernible as it progresses along its [url=http://galileoandeinstein.physics.virginia.edu/more_stuff/flashlets/kepler6.htm]elliptical orbit[/url]. During the cycle, sunlight reflects from the [url=http://apod.nasa.gov/apod/moon.html]Moon[/url] at different angles, and so illuminates different features differently. A full [url=http://www.inconstantmoon.com/not_phas.htm]lunation[/url] takes about 29.5 days, just under a month (moon-th).
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