Saturday, July 12, 2014

Tonight's Sky for July 12: Full Moon


Tonight, the Moon will reach its full phase, which means that, as seen from Earth, it will appear fully lit. As for why it appears this way, read on! The moon is always half lit no matter where it is in its orbit. As seen from Earth, it does not always appear so thank to simple geometry. When the Sun is 90 degrees relative to Earth, it appears half lit as we can only see half of the lit side. At new phase, when the Moon is between the Sun and Earth, we can't see any of the lit side, which is why it appears to be invisible. At full phase, when the Moon is opposite the Sun and on the far side of Earth, we can see all of its lit side, which is why it appears to be “full.” 

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