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The Earth's Moon

The Earth may only have one Moon, but it's a big one! The Earth's Moon is the fifth largest in the whole solar system. But it is still smaller than the Earth, so objects weigh less on the Moon than they do here. That's why the astronauts could enjoy bouncing around on the lunar surface.

Even though the Moon has no liquid water, it does have special "seas" and "land" on its surface. There are also many interesting features such as craters, mountain ranges, and lava plains. The interior of the Moon is made up of different layers of rock, some solid and some molten like lava. By studying the Moon's surface and interior, geologists can learn about the Moon's geological history and its formation.

The footprints left behind by the Apollo astronauts will last for many thousands of years because there is no wind on the Moon. The Moon has no atmosphere, so there is no weather to erase the footprints. On the Earth, the atmosphere acts as a blanket, keeping the warmth of the Sun in even at night. Because there is no atmosphere on the Moon, the temperatures there are very hot during the day (100 C) and very cold at night (-173 C).

The Moon doesn't produce its own light, but looks bright because it reflects light from the Sun. Think of the Sun as a light bulb, and the Moon as a mirror, reflecting light from the light bulb. The lunar phase changes as the Moon orbits the Earth and different portions of its surface are illuminated by the Sun.

Last modified October 19, 2005 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF