Astronauts Neil Armstrong and Buzz Aldrin landed in the Sea of Tranquility on the moon during the Apollo 11 mission in 1969.
People have invented a number of myths about the moon over the years. But Apollo 11's historic trip to the lunar surface in 1969 helped to debunk many of them, as it deepened humanity's understanding of Earth's natural satellite.
Take a look at how Apollo 11 helped to dispel several familiar and interesting myths about the moon:
Myth 1: The moon is made of green cheese
The idea that the moon is made of green cheese originated from fables in which the reflection of the moon in a pool of water was mistaken for a wheel of cheese. Though scientists never considered the moon a dairy product, the idea permeated popular culture. [Apollo 11 Moon Landing 45th Anniversary: Complete Coverage]
Apollo 11, along with the lunar exploration that prepared for it, put the idea to rest with its studies of the composition of the moon. In addition to examinations of the surface by satellites, Apollo 11 and other missions returned a total of 842 lbs. (382 kilograms) of moon rocks that were clearly inedible.
Although science had ruled out the possibility that the surface of the moon could be green cheese long before the Apollo 11 mission, the lunar landscape remained mysterious. Craters from meteorite strikes suggested that the landscape contained dust, but the thickness of the dust remained uncertain. Some scientists suggested that the finely powdered dust could swallow up spacecraft that landed on the surface. The successful landings of five robotic NASA Surveyor craft in the late 1960s revealed that such worries were unwarranted.
Myth 2: There are moon bunnies on the lunar surface
Many cultures studied the light and dark regions of the moon, and surmised that the darker areas formed what looked like a giant rabbit. From Asia to South America, the folklore abounds about how, in various ways, a rabbit's image had been imprinted on the lunar surface. Other myths discuss the presence of rabbits on the moon. [The Moon: 10 Surprising Lunar Facts]
Shortly before Apollo 11 reached the moon in 1969, the following conversation took place between mission control in Houston and Michael Collins, the astronaut who remained in the lunar orbiter while Neil Armstrong and Buzz Aldrin explored the moon's surface.
Houston: Among the large headlines concerning Apollo this morning, there's one asking that you watch for a lovely girl with a big rabbit. An ancient legend says a beautiful Chinese girl called Chango-o has been living there for 4,000 years. It seems she was banished to the moon because she stole the pill of immortality from her husband. You might also look for her companion, a large Chinese rabbit, who is easy to spot since he is always standing on his hind feet in the shade of a cinnamon tree. The name of the rabbit is not reported.
Michael Collins: OK. We'll keep a close eye out for the bunny girl.
Needless to say, the astronauts didn't find any rabbits, or lovely banished women, on the lunar surface.
Myth 3: The moon has a dark side
The moon's rotation syncs with the Earth in such a way that the same face is always pointed toward the planet. As a result, nearly 40 percent of the lunar surface remains unseen by most human eyes, leading many people to refer to the back of the moon as its "dark side". However, when the moon shines during the day, its unseen or far side points toward the sun, bathing it in light.
The first people to observe the far side of the moon with their own eyes were Apollo 8 astronauts Frank Borman, Jim Lovell and Bill Anders. After the famous moonwalk, Apollo 11 astronauts rejoined the orbiting Columbia and passed behind the moon on their journey home.
Myth 4: The moon's distance from Earth is set
Though the moon is a familiar object in the sky, its distance from Earth is constantly in flux. When Neil Armstrong and Buzz Aldrin landed on the moon, they set up the lunar ranging experiment, which remains in place today. The astronauts set up a lunar laser ranging reflector, a mirror designed to reflect pulses of lasers fired from Earth. Three more mirrors have since been left on the moon for similar purposes, set by astronauts from Apollo 14 and 15 and one French-built reflector placed by the unmanned Soviet Lunokhod 2 rover.
Here's how the laser ranging reflector works: Scientists on Earth send a laser beam through an optical telescope to hit the reflectors. By measuring how long it takes the beam to travel through space to the moon and back, they can calculate the distance to the moon with an accuracy of better than one part per 10 billion. That's equivalent to determining the distance between Los Angeles and New York to a precision of one hundredth of an inch.
As a result, scientists have determined that the moon is spiraling away from the Earth at a rate of 1.5 inches (3.8 centimeters) per year. [The Apollo Moon Landings: How They Worked (Infographic)]
Myth 5: The moon is a perfect sphere
Although the full moon appears as a perfectly circular disc in the night sky, it is actually asymmetrical. Its crust is thicker on the far side, while unusual mass concentrations show up on the near side.
Optical observations made from the orbiting spacecraft during Apollo 11, as well as several other Apollo missions, provided very accurate locations for 31 craters, suggesting that the center of mass of the moon did not lie at the center of its sphere, but rather was slightly displaced. Further studies demonstrated that the moon bulges slightly on its Earthward side.
Myth 6: The moon contains life
Although the idea may seem preposterous today, when Apollo astronauts first headed toward the moon, there was a concern that life in some form may exist on the lunar surface. Materials and equipment to be deployed on the lunar surface were sterilized to prevent contamination from Earth. At the same time, the returning astronauts were put through time-consuming quarantine measures to prevent bringing home potentially hazardous lunar life forms.
A study of the samples from the moon revealed no trace of past or present life on the lunar surface. A careful study was made for carbon, since life on Earth is carbon-based, but scientists found only a few dozen parts per million of the element that was native to the moon, much of which had been injected by solar wind. None of the carbon appeared to come from life processes. Minerals from the moon also lacked significant traces of volatile elements. Astronauts found no sandstone, shale or other minerals that require water to form.
The surface of the moon is simply too hazardous for life to form. The airless surface lacks a substantial atmosphere to shield growing life from radiation from the sun, and temperatures swing from minus 255 degrees Fahrenheit (minus 160 degrees Celsius) to 250 F (120 C) over the course of a month.
Myth 7: The moon is a hollow spacecraft
In 1901, science-fiction writer H.G. Wells wrote "The First Men in the Moon," a novel that depicts the interior of the moon as the home of an alien species. Other science-fiction stories followed suit. Science even got in on the act, with two Soviet scientists proposing that the moon is actually a shell-like alien spacecraft.
However, the Apollo 11 mission investigated the thickness of the moon's crust, mantle and core. One of the experiments set up by astronauts was the Passive Seismic Experiment, built to detect moonquakes over the course of three weeks. Although the experiment revealed that the moon does occasionally shake, it also showed that the vibrations are less powerful than those found on Earth over the corresponding period.
If three or more seismometers detect an event, scientists can calculate its origin. This, in turn, led to a deeper understanding of the lunar layers, revealing that the moon is not hollow.
Other Apollo missions deployed more advanced seismometers that helped further scientists' understanding of the moon's composition.