Earth's only natural satellite has entranced artists, astronomers, and scientists since the beginning of time. Its effect on the Earth, symbolism in popular culture, and scientific significance cannot be overemphasized.
From its size in relation to Earth and the rest of the solar system, to its complicated composition, here are some amazing facts about the moon.
On this scale, the distance between Earth and the moon would be 7 metre.
Because the moon doesn't orbit in a perfect circle, its distance from Earth fluctuates. The average distance between the Earth and the moon is 384,400 kilometers. At any given time, the moon could be between 28 and 32 Earths away from us.
The moon's gravity exerts a pull on Earth, which is partially responsible for the ebb and flow of ocean tides.
Physicist George Darwin (Charles Darwin's son) discovered that the way the moon's gravity pulls Earth's water is gradually slowing the rotation of Earth. Our day gets longer by about 0.002 seconds each century, which adds up over billions and billions of years. Darwin also concluded that the moon will eventually spiral outward, orbit more slowly, and create a longer month.
The full moon in January is called a "wolf moon" after the howling of hungry wolves in the dead of winter. Other full moon names include the "harvest moon" in September, the "strawberry moon" in June, and the "cold moon" in December. National Geographic gives the Native Americans credit for the full-moon naming system we use in North America.
The moon's orbit isn't perfectly circular; it's elliptical. So, when the moon is at its closest point to Earth in its cycle, it looks 14% larger and 30% brighter to us than when it is farthest away.
There are various theories about how exactly Earth was formed, but the moon is thought to have been created after a Mars-sized object collided with Earth, according to NASA. The debris from that crash began to orbit Earth and eventually coalesced to create the moon.
Given the moon's extremely thin atmosphere and lack of liquid water, it's hard to imagine humans settling there in any permanent fashion.
Recent research, however, has confirmed that there is water ice on the surface of the moon.
"With enough ice sitting at the surface - within the top few millimeters - water would possibly be accessible as a resource for future expeditions to explore and even stay on the moon, and potentially easier to access than the water detected beneath the moon's surface," NASA officials said in a statement, according to Space.com.
The Apollo missions "had a lot of problems with dust," as retired NASA astronaut Peggy Whitson previously described it to Business Insider. Dust on the moon, known as regolith, is a talc-like substance that can severely damage equipment.
There's also an enormous temperature range on the moon. The moon rotates on its axis, making a full turn every 27 Earth days. So, daytime on one side of the moon lasts about 13-and-a-half Earth days, followed by an equal amount of nighttime. When the moon is drenched in sunlight, the temperature can reach 115 degrees Celcius; when it's dark, the temperature can plummet to minus 179 degrees Celcius.
Data from the 1970s led to the discovery in 2006 that the moon is seismically active.
There are deep "moonquakes" caused by small distortions of the entire planet named "solid-body tides," vibrations from the impact of meteorites, and thermal quakes "caused by the expansion of the frigid crust when first illuminated by the morning sun after two weeks of deep-freeze lunar night," according to NASA. Additionally, shallow moonquakes, quakes with unknown causes that occur only 20 or 30 kilometers below the surface, can last up to 10 minutes. If on Earth, the vibration from such a quake could shift heavy furniture. (On Earth, water stops quakes from lasting more than a few minutes.)
In the solar system, there are more than 150 moons orbiting the planets. Earth's is the fifth largest. The largest moon is Ganymede, one of Jupiter's 79 moons.
On July 20, 1969, Neil Armstrong was indeed standing on the moon when he uttered the famous words, "that's one small step for a man, one giant leap for mankind."
Neil deGrasse Tyson has shut down the idea that the landing was a hoax using fuel calculations and common-sense logic. Deniers simply have trouble understanding the scope of technological achievements, he said.
Along with an American flag, astronauts initially left a patch honoring the fallen Apollo 1 crew on the moon, as well as a plaque that reads: "Here men from the planet Earth first set foot upon the moon. July 1969 A.D. We came in peace for all mankind."
Since then, as The Atlantic has reported, astronauts have left approximately 185,000kg of material on the moon. This includes unmanned space vehicles, ascent and descent stations, moon buggies, golf balls, and a family portrait belonging to Charles Duke of the Apollo 16 mission.
Between 1969 and 1972, NASA reported that 2,200 separate samples of "lunar rocks, core samples, pebbles, sand, and dust" from the moon's surface were brought back to Earth over the course of six flights. The samples came from six different lunar-exploration sites.
In 1960, the International Institute of Space Law was created to "promote international cooperation in the space law-making process." They created the Outer Space Treaty, enacted in October 1967, which prohibits a single nation from owning planets, stars, or other space objects. The treaty also says all space exploration must be done for peaceful purposes.
Every lunar eclipse through 2100 has already been calculated by NASA.
There will be one total and one partial lunar eclipse in 2019, and four eclipses in 2020.
The moon is 2,159 miles (3,476 kilometers) in diameter, while China is 2,193 miles (3,530 kilometers) wide.
On December 8, the China National Space Administration launched its Chang'e 4 mission to the moon's South Pole-Aitken basin, on the far side.
The mission's goals include learning about lunar geology, looking for water ice, scanning the night sky for radio bursts, and even experimenting with growing silkworms on the moon.
As Business Insider previously reported, the successful landing "is a major example of China's success in boosting its scientific, technological, educational, and economic standing in the world."
"Maria" is Latin for "seas," since ancient astronomers believed the dark areas were bodies of water on the moon. But these spots were actually once pools of lava that solidified to form basalt, a dark-coloured salt.
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