Potential Earthrises As Seen From The Moon's Surface
An earthrise that might be witnessed from the surface of the Moon would be quite unlike sunrises on Earth. Because the Moon is tidally locked with the Earth, one side of the Moon always faces toward Earth. Interpretation of this fact would lead one to believe that the Earth's position is fixed on the lunar sky and no earthrises can occur, however, the Moon librates slightly, which causes the Earth to draw a Lissajous figure on the sky. This figure fits inside a rectangle 15°48' wide and 13°20' high (in angular dimensions), while the angular diameter of the Earth as seen from Moon is only about 2°. This means that earthrises are visible near the edge of the Earth-observable surface of the Moon (about 20% of the surface). Since a full libration cycle takes about 27 days, earthrises are very slow, and it takes about 48 hours for Earth to clear its diameter. During the course of the month-long lunar orbit, an observer would additionally witness a succession of "Earth phases", much like the lunar phases seen from Earth. That is what accounts for the half-illuminated globe seen in the photograph.
Read more about this topic: Earthrise
Famous quotes containing the words potential, moon and/or surface:
“If the Russians have gone too far in subjecting the child and his peer group to conformity to a single set of values imposed by the adult society, perhaps we have reached the point of diminishing returns in allowing excessive autonomy and in failing to utilize the constructive potential of the peer group in developing social responsibility and consideration for others.”
—Urie Bronfenbrenner (b. 1917)
“The moon gives you light,
And the bugles and the drums give you music,
And my heart, O my soldiers, my veterans,
My heart gives you love.”
—Walt Whitman (1819–1892)
“All beauties contain, like all possible phenomena, something eternal and something transitory,—something absolute and something particular. Absolute and eternal beauty does not exist, or rather it is only an abstraction skimmed from the common surface of different sorts of beauty. The particular element of each beauty comes from the emotions, and as we each have our own particular emotions, so we have our beauty.”
—Charles Baudelaire (1821–1867)