This view shows the full Moon rising over the Marina in San Diego, California in 2014. While the Moon itself may seem like the most mundane of all astronomical sights, one can glean a tremendous amount of scientific knowledge simply by observing it. (Credit: Justin Brown/flickr)
Even just by examining the Moon with the unaided eye, we can learn an incredible amount about the Moon, Earth, and more.
The Moon is Earth’s brightest, largest night sky object.
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Animation showing the umbral phase of the November 19, 2021 partial lunar eclipse. At 9:03 AM UT, maximum eclipse was reached, where only 0.9% of the Moon remains illuminated by direct sunlight. The umbral phase lasted over 3.5 hours: the longest partial eclipse of the 21st century. Reconstructing the size of Earth’s shadow relative to the physical size of the Moon is the oldest method for measuring both the size of the Moon as well as the distance to it: a method first leveraged by Aristarchus back in the 3rd Century BCE. (Credit: NASA’s Scientific Visualization Studio)
It exhibits phases,
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Although one half of the Moon, only, is ever illuminated by the Sun, both the portion of the Moon that’s illuminated by the Sun and the illuminated portion that’s visible from Earth change over the course of a lunar month. A complete cycle, from new phase to new phase, defines the length of a lunar month. (Credit: Horst Frank & Nethac DIU/Wikimedia Commons)
large apparent motions,
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This two-panel view shows a human hand with outstretched index and pinkie fingers at arm’s length: approximately a 12 degree span. This is the amount that the Moon moves, typically, in the night sky from night-to-night, as shown by the motion of the low, bright point (the Moon) between the two panels. Bright Venus and Jupiter, also shown, move far less on a nightly basis due to their much greater distances. (Credit: ESO/Y. Beletsky (background); E. Siegel/Beyond the Galaxy)
and is required for eclipses.
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When the Moon passes directly between the Earth and the Sun, a solar eclipse occurs. Whether the eclipse is total or annular depends on whether the Moon’s angular diameter appears larger or smaller than the Sun’s as viewed from Earth’s surface. Only when the Moon’s angular diameter appears larger than the Sun’s are total solar eclipses possible. When the Earth is between the Sun and Moon, lunar eclipses can occur instead. (Credit: Kevin M. Gill/flickr)
These five additional, profound lessons also arise.
