The Moon has loomed large in the human imagination since…well, many moons ago. Here are some facts to bring it down to Earth.

1. Footprints left on the moon by astronauts could remain undisturbed for centuries. Because there is no liquid water and no atmosphere on the Moon, there is no weather to disturb the footprints or other formations on the surface.

2. On September 14, 1959, the USSR's Luna 2 became the first artificial object to strike the Moon. Ironically, it landed east of the Moon's Mare Serentitatis (Sea of Serenity). Upon impact, the spacecraft scattered its cargo of Soviet emblems around the crash site.

3. Ancient Moon-watchers thought the dark areas on the satellite's surface were oceans--hence the word used for those areas, mare (Latin for "sea"). They believed the lighter areas were continents.

4. The Moon is the main cause for ocean tides. The gravitational attraction of the Moon and the Sun on the Earth's oceans causes the ocean tides to move in and out (from high to low). Because the Moon is nearer to Earth than the Sun is, it has a bigger effect on the Earth's oceans.

5. The Moon's diameter is about 3,480 km (about 2,160 mi)--about one-fourth of the Earth's diameter.

6. A harvest moon is the full moon that occurs closest to the autumnal equinox (that is, the beginning of autumn). It is called the harvest moon because it occurs during harvest season in the temperate regions of the northern hemisphere.

7. Each manned landing on the Moon--Apollo 11, 12, and 14 to 17--brought rock and soil samples back to Earth (the Moon is not made of cheese, as it turns out). The total amount of Moon rock and soil brought back to Earth is 384 kg (847 lb).

8. Temperatures on the surface of the Moon range from 127°C (261°F) to -173°C (-279°F). That's a difference of more than 500° Fahrenheit! Measurements indicate that the internal temperature of the Moon is as high as 1600°C (2912°F).

9. The Moon is about 4.6 billion years old--about the same age as Earth.

10. We always see the same side of the Moon from Earth because the Moon rotates on its axis at the same rate that it rotates around Earth. The world first saw images of the far side of the Moon in October 1959, when photographs made by the Soviet Luna 3 spacecraft were released.

11. A blue moon is the second full moon in a calendar month. The reason it is called a "blue moon" is odd logic: a) the Moon appears blue in color very rarely, b) two full moons in one month is also a rare phenomenon so, c) when a second full moon occurs in a single month, it is called a blue moon.