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Welcome to...
THE MOON!
General Information:
When you look at the full moon, it is hard to believe that it is around 400,000 km away from Earth. With a diameter of almost 3,500 km, the moon is approximately 1/4 the size of Earth (Earth's diameter = 12,800 km) and has a gravity only 1/6 that of Earth’s. Imagine playing volleyball on the moon - your waist would be as high as the top of the net when you jumped up to spike the ball!

It takes the moon 27.3 days to revolve (orbit) around Earth which is the exact same amount of time it takes the moon to rotate (spin) on it’s axis. Because of this the same side of the moon always faces Earth so no matter when we look, the Sea of Tranquility and Tycho crater are always on the side facing us! This long "day" and "night", about two Earth weeks each, along with no atmosphere, causes the daytime high temperature to reach a staggering 107 degrees C and the nighttime low to reach -153 degrees C. The moon's orbit isn't a perfect circle. The point in it's orbit when it passes closest to Earth (363,300 Km) is called perigee and the point when it passes farthest away (405,500 Km) is called apogee (think "Apogee Away").

So where did the moon come from? Theories of how the moon came into existence might be considered “historical science” since we can only infer what happened based on observations we can make today. One of the most common theories is that the moon resulted when another large object (asteroid or small planet) in the same nebula from which Earth formed struck the Earth. The asteroid, about the size of Mars, collided with Earth, maybe forming the depression where the Pacific Ocean is today. As a result of the collision, a chunk broke off and formed the moon. A second theory is that the moon was an asteroid that was "captured" when it passed too close to the Earth. Can you think of other explanations for the moon's origin?

Main Surface Features:
The main surface features on the moon include highlands, maria, craters, rays, and rilles. Highlands are the lighter surfaces of the moon. They are areas of high or mountainous land - some are thousands of meters high! They are made of felspar-rich rock. Maria are the broad, smooth lowland plains that are filled with dense rock called basalt. It is thought that they were made from ancient lava flows. They are also called "seas" since that is what they looked like to early astronomers and since maria is the Latin word for sea. Craters are large circular depressions made by meteor impacts. They range in size from microscopic to hundreds of kilometers in diameter. Rays are light colored lines radiating out from craters. Rilles are long winding valleys. They are fissures or narrow channels on the moon's surface that might have been formed from rivers of lava.


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Half of the moon is always lighted and half is shadowed. During a new moon the moon is between us and the sun, so we only see only the shadowed half. There isn’t a solar eclipse every month because the moon’s orbit is tilted, so we only have an eclipse when the Earth, Sun, and moon are even. Total solar eclipses occur somewhere on Earth every 3-5 years.

During a full moon the Earth is between the sun and moon, so the lighted side of the moon faces us. When the sun, Earth, and moon line up so that the moon is in Earth’s shadow, then we have a lunar eclipse. These occur somewhere on Earth a couple times per year on average.

The rest of the phases are simply what portion of the lighted half of the moon we see from Earth. See the diagram at the right to see how they work. When half the lighted side of the moon faces Earth we have a quarter moon (first quarter is when the light is on the right, last quarter is when the light is on the left) Gibbous moons are when more than half but less than full lighted half of the moon faces Earth. Crescent moons are when the moon is between New and Quarter. It takes 29.5 days to complete one full set of moon phases.



Tides:
Tides occur because of the gravitational pull of both the sun and moon, but the moon's gravity has a much bigger influence on our tides. High tides happen because the moon is pulling on the Earth. The water near the moon is pulled slightly, causing a high tide. The moon also pulls on the Earth itself, so the Earth pulls toward the moon on the other side causing a high tide there as well. There are 2 high tides and 2 low tides on a point on Earth every 24 hours and 50 minutes.

Spring tides and Neap tides are special high tides and two of each occur every month. Spring tides happen every new and full moon. Since the Sun and moon are lined up at that time the pull is stronger than usual, so the high tides are extra high. At the same time the low tides are extra low. Neap tides happen at first quarter and third quarter. The Sun and moon are 90 degrees apart, so the gravity of the sun and moon are working against each other. The tides are reduced.

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The Apollo Program:
Between 1966 and 1972, there were 17 Apollo missions. Neil Armstrong, Buzz Aldrin, and Michael Collins were on Apollo 11 which, on July 20, 1969, was the first successful manned moon landing. Neil Armstrong was the first person to set foot on the moon. All together, 12 men have walked on the moon during six manned moon landings.



The Future:
Regarding the future, NASA wants to establish a long term base on the moon.
The base would allow people to live on the moon, and from there we could launch missions to Mars, because the moon’s gravity is only 1/6 as strong as Earth’s.
There is ice at the poles of the moon. Astronauts could use it for fuel and air. No one said they would use it for water, but maybe that’s just given.






Written /researched by Laurel Markert, Kaitlyn Jacobs, and Pete Idema
Edited by Pete Idema Dec. 2010
Unless indicated, images are from howstuffworks.com

References:
http://en.wikipedia.org/wiki/Moon
http://www.nasa.gov
http://science.howstuffworks.com/moon4.htm
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