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------------------------ - 2241 - Do You Need Some Moon Eclipse Party Trivia?
- The Moon contains some interesting facts that make for an interesting conversation at your Moon eclipse party on the 20th of December, 2019. See Review 1228 for details about the astronomy events in December, but, here is trivia just about our Moon.
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- The total eclipse of the Full Moon occurs this Sunday night at 9:00 PM, December 20 - 21. If you have a party you may need some trivia to keep things lively because it takes 1 ½ hours for the Earth’s shadow to cross the Moon.
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- We tend to take the Moon for granted. We know it circles the Earth every month and there are phases of the Moon from New Moon to Full Moon. But the Full Moon does not occur the same day every month. That is because the Moon’s orbit is once every 27.55 days. That does not match up exactly with our 30 and 31 day months. In fact, once in a Blue Moon we have two Full Moons in the same month. The devil is in the details.
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- The Full Moon looks very bright in the night sky. It is a mirror for the bright sunlight that is coming from behind us. However, the Moon is only reflecting 7% of the sunshine that strikes its surface. By comparison the Earth reflects 37% of the sunlight. A Full Earth would be 5 times brighter then the Full Moon. The Sun would be 450,000 times brighter.
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- The Full Moon appears brightest when it is directly overhead at midnight on December 20th. That is because it is a few percent closer and you are viewing it through less atmosphere, as much as 13% less depending on the angle you are viewing toward the horizon. It also appears brighter when the air is dry. Water vapor will scatter the moonshine making it appear dimmer.
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- With a telescope or binoculars you can easily resolve on arc second on the Moon. One arc second on the Moon’s surface corresponds to 1 mile of resolution. The diameter of the Moon is 1800 arc seconds. This is ½ degree in diameter the same as the Sun. You can see over 30,000 craters on the Moon, if you have time to count them. By comparison the Earth has about 200 visible craters.
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- The Moon does not orbit the center of the Earth. The Earth and the Moon share a common center of gravity. That spot is 1,000 miles below your feet when the Moon is directly overhead. This spot is still 2,900 miles above the center of the Earth.
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- The Moon has a circular orbit that turns slightly more elliptical during a New Moon and a Full Moon. That elliptical shape rotates around the Earth completing a cycle every 9 years. As a consequence of this elliptical rotation the Moon never returns to the same starting point after each orbit. If you were in outer space and tracing out the Moon’s orbit about the Earth the tracing would look like the petals of a daisy.
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- The Moon moves through the sky its own diameter every hour, going west to east. It is traveling 2,237 miles per hour and its diameter is 2,160 miles. So, it travels its own diameter every hour. This makes it easy to predict where it will be a few hours later in the sky.
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- The Earth has a 23 ½ degree tilt compared to the plane of the orbits of the other planets. The Moon chooses to orbit with the other planets and not with the Earth. The Moon does not orbit the equator of the Earth. That is the reason that its path, which is near the elliptic, is higher and lower on the horizon much like the Sun and the other planets.
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- However, the Moon does not stay on this perfect plane. Again it wobbles. It completes one wobble every 18.61 years and the tilt of the wobble is up to 5 degrees. Looking at the Moon and the Sun-Earth plane from outer space the Moon’s orbit would trace out a wobble like a dropped dish rattling on the floor.
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- This wobble results in the Full Moon being 5% higher in the night sky at certain times of the 19 year cycle. On the 21st of December, 2010, the Full Moon is the highest it gets in the sky for that year. At 12:01 A.M. on the 21st the total eclipse will begin replacing the 120 stars you can see in the sky with 2,600 stars as the darkness brings them out.
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- The angular size of the Moon in the sky varies from 25 arc minutes to 27 arc minutes during the month. We tend to estimate that at ½ degree. It is one of the largest moons in the Solar System. 4 others are larger, but, our Moon is larger than the wannabe planet Pluto. The Moon is 27% the size of the Earth in diameter. Few people believe that when they first learn that the Moon is ¼th the size of the Earth.
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- Best wishes for a clear nights and a Happy New Year.
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- See Review 64 - What You Did Not Know about our Moon, to learn more.
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- Review 1899 - The far-side of the moon. This review also list 8 more reviews about our Moon.
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- January 21, 2019. 1232
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--------------------- Monday, January 21, 2019 -------------------------
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