Moon-Interesting Facts

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Chandramaa (Moon)-Popular Information
See also Chandramaa's Religious Information Grahan

Interesting Facts

Moon is a cold rocky body. Its diameter is abut 2,160 mile (3,476 kms). It has no light of its own but shines through the sunlight reflected from its surface. It orbits the earth every 29 and 1/2 days.

--It is interesting to note that the "month" word has been derived from the Moon's 29.5 day period.
--It is interesting to note that if it were just 140 miles shorter than this, it could have never caused a total solar eclipse.
--On Full Moon day, it rises at sunset and is visible all night long. At the end of the night, it just sets when the Sun rises. None of the Moon's other phases has this characteristic. It happens because the Moon is directly opposite the Sun in the sky at this time and prone to lunar eclipse.

The "Moon Illusion"

The Moon appears larger on the horizon than overhead because you are comparing it to foreground objects. Right or wrong? Wrong. The Moon does appear larger on the horizon, but it is only because of the way we perceive the sky, not because it is really larger on the horizon and smaller in the sky.

This so-called "moon illusion" or "moon effect" has perplexed people since earliest historical times, at least as early as the 7th century BC. It is described in early Greek and Chinese writings. Aristotle mentions it in 350 BCE.

The moon seems larger in angular size when it is near the horizon than when it is high in the sky. Some people judge it to be as much as twice as large, but the average estimate is 50% to 75% larger. The moon does vary in angular size due to the eccentricity of its orbit. When the moon is closest to earth its angular size is about 11% larger than when it is most distant.

It's not a small effect. The Sun displays the same illusion, but viewing the Sun directly with the eye is hazardous without proper precautions. The same illusion is observed with any extended object in the sky, such as a constellation.

This phenomenon is not a physical or atmospheric effect, as may be easily demonstrated by photographing the moon in the sky at various elevations and comparing its size on the negatives. The moon's angular size is nearly constant as it moves across the sky, the moon subtending about 0.5 degree in the sky.

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