Astronomy — The Moon
- Diameter = 2000 miles
- Distance from the Earth = 239,000 miles
- Lunar daytime lasts about 2 weeks and surface temperature is 250 degrees Fahrenheit
- Lunar night lasts 2 weeks and surface temperature is -300 degrees Fahrenheit
- Orbital speed around Earth = 2200 mph
- Moon’s orbit times
- Sidereal (relative to the stars) = 27 days 7 hours
- Solar or synodic (relative to the Sun) = 29 days 13 hours
- The Moon is a poor reflector, reflecting only 7% of the sunlight which strikes it. The Earth reflects 40%.
- Inertia and gravity are the two forces which keep the Moon in orbit around the Earth
- Since the Moon rises in the east and sets in the west, it appears to be traveling westward. Actually, it orbits Earth from west to east, but because Earth is rotating from west to east faster than the moon travels in orbit (relatively speaking), we are “passing” the Moon. As verification, the Moon will draw closer to a star east of it even though the Moon seems to be moving westward relative to the Earth.
- While the Earth is making one full rotation, the Moon moves 13 degrees east in its orbit.
- The Moon revolves once on its axis in the same time it takes to orbit the Earth once, so it keeps the same face pointed toward Earth continuously. This phenomenon is due to Earth’s gravitational effect on the Moon.
- Lunar eclipse:
- At the distance of the Moon, the Earth’s shadow is 5700 miles in diameter
- Penumbra is a partial eclipse or shadow
- Umbra is a complete eclipse or shadow
- The refracted sunlight illuminates the Moon and makes it glow copper-red
- Moon’s orbit is inclined 5 degrees relative to the plane of the Earth’s orbit around the Sun, which is why we don’t have eclipses every month.
- Lunar geology:
- Rocks found on the Moon are 4.6 billion years old, as old as the solar system and Sun
- The Moon’s period of volcanism only lasted about 1 billion years
- The Moon has a solid crust which hasn’t broken into planes
- The lunar terrain has 2 distinct areas – the uncratered lowlands (maria) and the heavily-cratered highlands
- The four stages of the Moon’s history are melting, differentiation, cratering, lava floods
- The most likely scientific explanation for Moon’s creation is the large-impact hypothesis (a Mars-sized planetesimal struck Earth at a sharp angle, fracturing off the material from which the Moon ultimately formed)
- The Moon appears red during a lunar eclipse because Earth’s atmosphere preferentially filters out the other colors in the sunlight and bends reddened light into Earth’s shadow.
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