- For the founder of the Unification Church, see Sun Myung Moon
A moon is a natural satellite orbiting a planet. The Earth's only moon is known rather unimaginatively as "the Moon". Being the most noticeable object in the night sky, it is a subject of much woo, particularly in astrology where it is usually given a female quality and a high degree of importance in the sky.
 True scientific facts about the moon
 Tides and spins and sides
The Moon's period of rotation around its own axis is equal to its period of revolution around the Earth. As a result, one of the Moon's hemispheres is permanently facing the Earth, though one can actually see more than a half of the Moon's surface due to libration. This synchronization is caused by the gravitational interaction of the Earth and the Moon, in a process known as "tidal locking". This is not unique to the Earth-Moon system, though, and many other moons in the Solar System are tidally locked or near-locked to their parent bodies.
The hemisphere facing the Earth is known as the "near side" and the other one is called the "far side". There is no "dark side of the Moon". Both "sides" experience day and night, which is what causes lunar phases (with a full moon being the result of sunlight illuminating all of the near side; the sun only lighting the far side results in a new moon or no visible moon). The only difference is that on the near side it is a little bit lighter during the night (new moon) due to the illumination provided by the sunlight reflecting off the Earth.
The Moon's gravity causes the tides on Earth. This was independently discovered by many ancient civilizations, including the Maoris and the Babylonians. Later, Isaac Newton showed that tides are a consequence of gravity, but obviously this is only a theory. Noted scientist Bill O'Reilly instead sees the tides as definitive proof of God's direct intervention: tide goes in, tide goes out. Never a miscommunication. You can't explain that.
It is thought that the moon may have been very important in the development of life, as the tidal activity caused by its gravity essentially churned the oceans, mixing up the chemical ingredients that could have caused abiogenesis to occur.
Occasionally the Earth gets between the sun and the moon, temporarily darkening the moon. Sometimes the moon gets revenge for this by preventing some sunlight from reaching the Earth by getting in front of the sun and causing a solar eclipse. (It isn't particularly good at this since only a small part of the planet can see a total eclipse.)
The Moon, as the second most hallowed object in the sky, is honored by having first (or second, depending on your calendric issues) day of the week named after it: Monday.
 Crazy non-scientific claims about the moon
 The moon gives off light
It seems natural enough for pre-scientific cultures to assume that the sun and the moon both give off light. However, this is not true; the moon is a reflector of light, not a generator. A good example of this is Genesis 1:16, in which god creates "a greater light to rule the day" (the sun) and "a lesser light to rule the night" (the moon). So there goes any claim that genesis is scientific I guess.
Bill Nye the Science Guy took the bible to task on this one. It wasn't popular.
 Muhammad: Moon-Smasher
According to the Qur'an, Muhammad broke the Moon. Yes, really. This is a real piece of silliness that basically renders any claim that the Qur'an is science to be utter bullshit. It's total fantasy, like Moses parting the Red Sea on a much grander scale.
Nevertheless, some truly dedicated followers of the "TEH QUR'AN IS TOTES SCIENCE" argument have still tried to prove it. A few of them stoop to using an article proposing that NASA found a crack that ran all the way around the Moon -- this argument is a total fraud, as I'm sure anyone with a non-Qur'an-addled brain can spot.
Many Islamic scholars believe that this verse is best understood as a statement of something to occur at the final judgment. This is supported by the fact that the Surah concerns itself with that judgement, and the references to previous judgements are in the middle part of the Surah, and also that the immediate context of the verse makes a future rather than past interpretation more likley. While there is weak support in the Sunnah for a literal past tense interpretation of the event, even in that case, a plausible interpretation would include the possibility of e.g. a large asteroid impact providing the appearance of the Moon splitting (contemporary writings from India record one such event). It should also be noted that the writing here is poetic, so what exactly "the Moon is cleft asunder" indicates is uncertain and based on the Arabic is just as likely to have a metaphorical meaning. In other words, there is no single interpretation of what exactly this verse refers to. If taken literally it refers to some obvious sign in the moon, figuratively it would likely refer to Islam "tearing assunder" the religious fabric of the Middle East (if past tense) or the world (if end times was meant).
Other muslim apologetics claim that, when Muhammad put the Moon back together, there was no crack because it was joined together perfectly, molecule-to-molecule. This is special pleading on a grand scale and should be ignored.
 The Moon: proof of creationism?
In a word, no. It isn't, although it's been touted as one.
The Moon has been a source of astronomical study for at least three millennia. To say that science has failed to explain key elements of lunar motion, geography, or composition, is to be willfully blind. Nonetheless, many creationists fabricate "errors" in scientific studies of the Moon, and suggest that, since science has failed, the only alternative is creationism. This is gap-filling with God to an absurd degree. Assuming, for once, that science could not explain the Moon, this does not imply that the only explanation is God. Science evolves. Not everything is known now, nor should science be forced to prove the universe to disprove creationism. The standard for evaluating creationist claims about scientific disciplines is the same that applies to all scientific theories: does the claim match the evidence? Regarding creationism, the answer is a resounding, "no!"
 Moon landings and the idiots that claim they are a hoax
Twelve American astronauts landed on the Moon between 1969 and 1972, took pictures, left behind some junk, and came back home. Deal with it.
 Moon cheese!
The moon is quite definitely made of cheese. Wallace and Gromit proved it.
 Pub trivia
Amaze your friends and win free beers for yourself, by taking bets that the Earth has more than one moon. Once everybody is expecting a pint from you, look really smug and say, "What about Cruithne then?" Enjoy your beers. Unless your friends (rightly) point out that 3753 Cruithne is actually an asteroid in orbital resonance with Earth, and then beat you up for not buying the 14 pints you owe.
 See also
- ↑ Pictured here is the near side, which faces Earth constantly and is completely visible during a full moon. The far side doesn't have nearly as much of the darker spots that the "man in the moon" is made of so it's more pale and boring.
- ↑ See the Wikipedia article on Libration. - it has a nice animation showing the libration of the Moon over a month.
- ↑ Conner, Clifford. A People's History of Science: Miners, Midwives, and Low Mechanicks. p. 206. http://books.google.com/books?id=PIzziChYQvoC&lpg=PA208&ots=G9C-8S-u8Q&dq=tide%20moon%20~sailor%20history&pg=PA206#v=onepage&q=tide%20moon%20~sailor%20history&f=false.
- ↑ "Bill O'Reilly thinks the tides are proof of God's existence: 'You can't explain that'". CrooksAndLiars.com. 2011-01-07. http://crooksandliars.com/david-neiwert/bill-oreilly-thinks-tides-are-proof-.
- ↑ Earth's "second" moon