Thread: Science Science is Cool....
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Old 10-17-2013, 06:13 PM   #1035
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What if the Moon was as close as the International Space Station?

The International Space Station orbits at roughly 420 kilometers (260 miles) above the surface of the Earth. What would it look like if the Moon circled about our planet at a similar distance? Pretty damn epic, that's what.



At this distance the Moon would rise in the west and set in the east, The Moon Orbits the Earth counterclockwise when viewed from the North pole looking *down*. the same direction that the earth rotates. Normally the Moon orbits much slower than the earth rotates so it rises in the east and sets in the west, however at 420km it orbits much faster, faster than the earth rotates underneath, therefore it will rise in the west and set in the east.

The Moon would also orbit very quickly, although yetipc1 notes that time in the animation has been sped up.

Of course, the Moon could never circle our planet so closely. For one thing, there's the Roche Limit to consider – the distance at which the tidal forces of a larger celestial body (the Earth, in this case) win out over the gravitational forces holding a smaller body (the Moon) together. The Earth-Moon Roche limit is a little over 18,000 kilometers, about 1/20th the distance of its current orbit. Venture any closer than that, and the Moon is liable to be ripped apart, potentially turning Earth into a ringed planet. Plus, even if the Moon could orbit our planet at so near a distance without disintegrating, there's still the question of what effect its gravitational forces (which would be felt hundreds of times more keenly) would have on proceedings here on Earth.

Still, it's a great thought experiment, and a really fantastic animation – incredibly well-planned and executed. And for those wondering, at no point in the animation is the Moon actually transparent. What you're seeing is a well-animated example of a phenomenon known as Earthshine, whereby the Moon is illuminated not only directly, by the Sun, but indirectly by sunlight reflected off the Earth. yetipc1 explains what you're seeing:

When the Moon eclipses the Sun, the camera exposure is adjusted so that you can see the Light of the earth reflecting back upon the moon... it is Blue on the left side because the moon is flying over the Gulf of Mexico, and is white/tan on the right side because that part is over the United States . it is Dark in the middle because it is casting a huge shadow, and that shadow does not reflect light back on the Moon. I didn't quite expect it to look like this, it was a nice surprise

As the Moon dips below the horizon, the sliver of illumination is also the result of planetshine.
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