1. On average, the moon is 238,750 miles (384,400 km) from Earth, or about 30 Earth widths away.^b
2. Most scientists believe the moon formed as a result of a “Giant Impact,” or “Giant Whack.” According to this theory, a Mars-sized planet struck a glancing blow to early Earth. The impact “splashed off” rocks and debris into space, forming a huge ring around Earth that later clumped together to form the moon.^b
3. Not all full moons are the same size. Their size varies depending on whether the moon is at its apogee (far away) or perigee (nearby). The moon is generally 14% bigger when at its perigee.^d
4. When the moon is at its apogee (farthest from Earth), the tides and weather tend to be more predictable. When the moon is at its perigee (closest to Earth), the increased gravitational pull can create larger tides and more unstable weather.^d
5. The moon has had a violent history. It underwent what scientists call a Late Heavy Bombardment (LHB) or “lunar cataclysm” period somewhere between three and four billion years ago. During this time, the moon (and, most likely, Earth) was bombarded with meteorites.^h

The moon is more egg-shaped than round

6. The moon is not round—it is shaped like an egg.^e
7. The moon’s core is 2-4% of its mass, whereas Earth’s core is about 30% of its mass.^b
8. Moonquakes, which originate several miles below the moon’s surface, may be a result of Earth’s gravitational pull. Engineers say these quakes could become a factor if lunar bases are ever built on the moon.^d
9. When the moon formed 4.6 billion years ago, it was 14,000 miles (22,530 km) from Earth. Now it’s more than 280,000 miles (450,000 km) away. The moon looked three times larger when it was closer to Earth.^d
10. Because the moon has no atmosphere, its temperature ranges from less than -200° F to more than 200° F.^e
11. The largest crater in the solar system is found on the moon. Called the South Pole-Aitken, this giant crater is on the far side of the moon and is 1,550 miles (2,500 km) in diameter. The largest crater visible to Earth (on the near side of the moon) is the Bailly Crater, with a 183-mile diameter.^e
12. The moon’s diameter is 2,159 miles (3,475 km), roughly four times smaller than Earth’s, which is 7,926 miles (12,756 km).^b
13. If Earth were one big ocean, the tidal bulge would travel once around Earth in 24 hours and 50 minutes. That’s the time of one moonrise to the next.^e
14. The moon’s gravity has slowed the speed of Earth’s rotation. Long ago, it was much faster and days were much shorter.^e
15. The six Apollo crews came back to Earth with a total of 850 pounds (385 kg) of the moon.^e
16. Approximately 49 moons could fit into Earth.^e
17. The moon is 400 times smaller than the sun, but it is also 400 times closer to Earth—so from Earth, the moon and the sun look about the same size.^d
18. The entire surface of the moon is covered in a layer of crushed and powdered rocks called regolith (from the Greek rhegos = blanket + lithos = rock). The dust is a result of millions of years of bombardment from space by tiny micrometeorites.^h

An astronaut’s footprint can last millions of years on the moon

19. Because the surface of the moon has no wind or water, an astronaut’s footprint could last for millions of years.^e
20. A solar eclipse happens every one or two years, but total eclipses can be seen by those within the moon’s shadow only every few hundred years. The shadow cast by the moon races across Earth at hundreds of miles per hour, so the eclipse is over within a couple of minutes.^d
21. A lunar eclipse, when Earth passes between the sun and the moon, lasts longer than a solar eclipse because Earth’s shadow is so much larger.^d
22. An annular eclipse occurs when the moon is too small to block the whole sun and leaves a ring of light visible. This eclipse happens because the moon’s orbit is not a perfect circle, so when the moon is farthest away from Earth, it appears smaller in the sky.^d
23. A full day on the moon, from one sunrise to the next, lasts about 29 Earth days on average.^d
24. From the moon, Earth is almost four times the size of a full moon from Earth, and it never moves across the moon’s sky.^d
25. Moonquakes reach a peak roughly every 14 days, which is when the moon is closest to and farthest away from Earth. This is also when the tidal forces produced by Earth’s gravity reach their peak.^h
26. Because there is no atmosphere on the moon, there is no twilight before nightfall.^e
27. Unlike the rising sun, which moves along the horizon in the same pattern every year, the rising moon follows a complex 18.6-year cycle. Ancient civilizations understood this complex cycle and built monuments that tracked the moon’s movement.^c

The ancient Chinese believed a dragon was swallowing the sun during an eclipse

28. Before astronomers realized solar eclipses were caused by the moon, the Chinese thought an enormous dragon swallowed the sun, and they made as much noise as possible to scare the dragon away.^h
29. The moon was worshipped by many cultures as a goddess. The ancient Greeks and Romans even had three lunar goddesses to represent the moon’s changing phases. Artemis (Diana) was the new moon, Selene was the full moon, and Hecate was the dark side of the moon.^h
30. The first person to draw a map of the moon as it appears through a telescope was British astronomer Thomas Harriot (c. 1560-1621).^e
31. The Earth is 81 times heavier than the moon.^e
32. A 13,000-year-old eagle bone found in France appears to have served as a counting stick to track the phases of the moon.^c
33. The oldest known map of the moon, about 5,000 years old, was found carved into a rock in a prehistoric tomb at Knowth, County Meath, in Ireland. Before this was discovered, the oldest known lunar map was by Leonardo da Vinci, which was created around 1505.
34. The first probe to reach the moon was the Soviet space probe Luna 2. It crash-landed on the moon in 1959. The first probe, Luna 1, missed the moon by 3,000 miles (5,000 km).^h
35. The Soviet Luna 9 was the first soft landing on the lunar surface, proving that a stable landing on the moon was possible. Until then, astronomers worried that spacecraft might sink into the lunar surface.^e
36. Aristotle and Pliny the Elder believed that a full moon affected the water in a human’s brain, causing insanity or irrational behavior.^f
37. On November 17, 1970, the Soviet robot Lunokhod 1 was the first vehicle to travel on the moon.^e
38. On July 20, 1969, the Apollo II lunar module (named Eagle) landed on the moon. Neil Armstrong became the first person to set foot on the moon. The last person to stand on the moon’s surface was Eugene Cernan in 1972.^e
39. At full and new moon, the moon and sun line up with Earth. The extra pull of gravity makes higher tides, called “spring tides” (which has nothing to do with the season). At the moon’s first and third quarters, when the sun and moon form a right angle with Earth, the tides are weaker and are called “neap tides.”^h

The high jump record on the moon would be around 50 feet

40. The moon has just one-sixth the gravity of Earth. This means that the astronauts' suits that weighed 178 pounds on Earth weighed only about 30 pounds on the moon. The high jump world record is about 8.2 feet (2.5 m)—on the moon, that would be 50 feet (15 m).^e
41. The same side of the moon always faces Earth because the moon takes the same length of time to rotate once as it does to travel all way around Earth.^e
42. From Earth, only 59% of the moon is visible.^e
43. Earth rotates 1000 miles per hour. The moon rotates much slower at 10 miles per hour.^e
44. The phrase “once in a blue moon” traditionally refers to an impossible event or an event that rarely happens. The term “ blue moon” has its roots in the Old English word belewe or “betrayer” because an extra full moon before Lent was viewed as a “betrayer moon.” Scholars believe that belewe eventually morphed into the word blue. In the mid-twentieth century, the Farmer’s Almanac by Sky and Telescope magazine mistakenly defined a blue moon as a second full moon in a calendar month. The moon can actually appear blue if there are particles in the air that are larger than red light wavelength (.7 micron), which can occur during volcanic eruptions or forest fires.^d
45. Looking down from its north pole, the moon orbits counterclockwise, from west to east.^h
46. Driving a car to the moon would take 130 days. A rocket would take 13 hours. Traveling by the speed of light would take 1.52 seconds.^e
47. An average desktop computer holds five to 10 times more computing power than was used to land a man on the moon.^e
48. The volume of Earth’s moon is the same as the volume of the Pacific Ocean.^e
49. Easter is calculated based on the moon. The holiday is the first Sunday after the first Saturday after the first full moon after the equinox. Interestingly, as archetypal symbols of the feminine, fertility, rebirth, and the lunar cycle, rabbits have been associated with the moon in many mythic traditions.^c
50. According to the Outer Space Treaty, the moon is under the same jurisdiction as international waters. The treaty also says the moon can be used for peaceful purposes by all nations, and it prohibits weapons of mass destruction or military bases of any kind on the moon.^d
51. There are two basic types of terrain on the moon: bright and dark. The bright terrain is called “highlands” because it is higher in elevation. The dark terrain is called the lunar “maria” (Latin for “seas”) and is lower in elevation. The highlands are typically older than the maria.^e
52. Scientists are unsure why the maria, which make up 16% of the moon, is concentrated on the near side of the moon.^e
53. The gravitational force of the moon in relation to Earth slows Earth’s rotation by about 1.5 milliseconds per century and raises the moon into higher orbit by about 3.8 centimeters or 1.5 inches per year.^e
54. In approximately 15 billion years, the moon and Earth’s gravitational pulls on each other would stabilize. But in approximately 7 billion years, the sun will have become a red giant star, completely engulfing and incinerating the moon and Earth.

A compass would not work on the moon

55. A compass would not work on the moon because it has no global magnetic field.^e
56. The moon’s rotation appears to wobble a bit so that a little of the far side can sometimes be seen. However, most of the far side was completely unknown until the Soviets photographed it in 1959 with Luna 3.^e
57. Although a full moon seems bright, it is actually reflecting just 7% of the sun’s rays.^e
58. Strange colored lights have sometimes been seen briefly on the moon’s surface. Scientists believe these lights are made by gases that leak from deep inside the moon.^e
59. The word “moon” comes from the Latin word luna, which means “glowing” or “bright.” The words “month” and “menstruation” are related to the word “moon.”^h
60. The moon’s phases have historically been linked with madness, and the word “lunatic” comes from this association.^f
61. Apollo 11, the first manned mission to the moon, took about four days and six hours to get to the moon.^e
62. Mercury and Venus are the only planets in our solar system that have no moon.^b
63. Even though moons in the solar system are very different from one another, they have at least two things in common: (1) they orbit a planet and (2) they only reflect light from the sun.^b
64. There are three kinds of moon rocks: basalt (dark), anorthosite (light), and breccia (a mixture of several rocks). These types of rocks are also found on Earth.^b
65. The moon is the fifth largest satellite in our solar system. It is the largest moon in relation to the size of its planet. It is the second densest moon after Jupiter's moon Io.^b
66. The “dark side” or far side of the moon is actually not always dark. It reflects light as often as the near side, once per lunar day, during the new moon phase (when the Earth-facing side is completely dark).^e

Moon dust smells like spent gunpowder

67. Moon dust is said to smell like spent gunpowder.^g
68. Earth’s moon doesn’t orbit around Earth’s equator, like many other planets’ moons. It’s inclined 20-30°.^e
69. Tidal drag between the moon and Earth eventually would lead Earth to match the speed of the moon. However, before that would happen, the sun would have become a red giant, engulfing and incinerating Earth.^d
70. In 500 million years, the moon will be 14,600 miles farther away than it is right now. When it is that far, total eclipses will not take place.^e
71. Only 12 people have been on the moon: the astronauts on the Apollo missions from 1969 to 1972.^h
72. It wasn’t until 1665 that scientists realized that other moons orbited other planets. Earth’s moon’s official name then became a capitalized “Moon.”^h
73. A full moon is about five times brighter than a half-moon.^e
74. In November 2009, NASA declared that it had discovered water on the moon that could allow for the development of a space station on the moon. The water is billions of years old, which could give scientists clues into the history of the solar system.^l
75. The moon’s crust is thicker on the far side. Scientists are unsure why, though they speculate that the near side feels more gravity from Earth.^a
76. In astrology, the moon represents the inner nature of a person. The moon sign reveals a person's emotional and subconscious state. In Western astrology, the moon is associated with the maternal, while the sun is associated with fatherhood.^d
77. According to many stories across cultures, the “man in the moon” was placed in the moon for stealing. Different cultures offer various descriptions of what he stole, ranging from a hedgerow to sheep to trying to steal the moon itself.^e

-- Posted June 5, 2010

References

^a Beatty, Kelly. “Moon’s Puzzling, Thick-Skinned Far Side.” Sky & Telescope. Accessed: April 26, 2010.

^b Chong, S.M., et. al. 2002. Photographic Atlas of the Moon. New York, NY: Cambridge University Press.

^c Duncan, David Ewing. 1998. The Calendar. London, UK: Fourth Estate, Ltd.

^d Furness, Tim. 2001. Spinning through Space: The Moon. New York, NY: Raintree Steck-Vaughn Publishers.

^e Graham, Ian. 1999. The Best Book of the Moon. New York, NY: Kingfisher Chambers Inc.

^f Lilienfeld, Scott O. and Hal Arkowit. “Lunacy and the Full Moon.” Scientific American Mind. February 2009. Accessed: April 26, 2010.

^g “The Mysterious Smell of Moondust.” NASA. January 30, 2006. Accessed: April 26, 2010.

^h Sparrow, Giles. 2001. Exploring the Solar System: The Moon. Chicago, IL: Heinemann Library.