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The Moon, Earth's Nearest NeighborThe moon is Earth's nearest cosmic neighbor, but it is more than just a big pretty light in the sky.
Here are 10 cool, and sometimes surprising, facts about Earth's nearest neighbor: the moon.
FIRST STOP: How the Moon was Made
Making of the MoonSlide 2 of 21
Making of the MoonThe moon was created when a rock the size of Mars slammed into Earth, shortly after the solar system began forming about 4.5 billion years ago, according to the leading theory.
NEXT: Locked in OrbitSlide 3 of 21
Locked in OrbitSlide 4 of 21
Locked in OrbitPerhaps the coolest thing about the moon is that it always shows us the same face. Since both the Earth and moon are rotating and orbiting, how can this be?
Long ago, the Earth's gravitational effects slowed the moon's rotation about its axis. Once the moon's rotation slowed enough to match its orbital period (the time it takes the moon to go around Earth) the effect stabilized. Many of the moons around other planets behave similarly.
What about phases? Here's how they work: As the moon orbits Earth, it spends part of its time between us and the Sun, and the lighted half faces away from us. This is called a new moon. (So there's no such thing as a "dark side of the moon," just a side that we never see.)
As the moon swings around on its orbit, a thin sliver of reflected sunlight is seen on Earth as a crescent moon. Once the Moon is opposite the Sun, it becomes fully lit from our view — a full moon.
NEXT: Moon...trees?Slide 5 of 21
Apollo Moon TreesSlide 6 of 21
Apollo Moon TreesMore than 400 trees on Earth came from the moon. Well, okay: They came from lunar orbit. Okay, the truth: In 1971, Apollo 14 astronaut Stuart Roosa took a bunch of seeds with him and, while Alan Shepard and Edgar Mitchell were busy sauntering around on the surface, Roosa guarded his seeds.
Later, the seeds were germinated on Earth, planted at various sites around the country, and came to be called the moon trees. Most of them are doing just fine.
NEXT: More Than One Moon?Slide 7 of 21
Earth's Sister MoonsSlide 8 of 21