When it comes to moons, it seems like these are a planet’s must-have accessory. Although Mercury and Venus have no moons whatsoever, Mars has two while the Outer Planets have what seems like an innumerable amount. On the other hand, Earth only has one moon. And while the moons of the other planets were given elaborate names, our moon is simply called The Moon.’
The Origin of the Moon
The Moon has been around for as long as human civilization. And because it is the biggest and brightest body in the night sky, it has become an object of admiration, awe, and even worship. But, how did the moon come to be? Many scientists believe that the moon was formed from ejected material after Earth collided with an object the size of Mars. This material fused together to form the Moon, which went in orbit around the Earth. It has been determined by the radioisotope dating of moon rocks, that this event occurred around 60 million years after the Earth itself, and may show what our planet appeared like in the early stages of its life.
When the Moon was newly formed, it was much closer to the Earth; and was roughly 14,000 miles (22,530 km) away. But with each year, the Moon is distancing itself from the Earth by stealing some of the its rotational energy and using it to propel itself about 3.8 centimeters higher in its orbit. Now, the Moon is situated more than 280,000 (450,000 km) from Earth.
The Moon’s age can be clearly seen with its appearance. In 1610, when Galileo discovered that the Moon had craters on its surface, many people were disgraced because they believed the Moon to be a perfect sphere created by the gods. But the Moon is far from perfect nor actually a sphere. Instead, the moon is shaped more like an egg. This may be a result of when it was formed and its inner liquids went solid, most were pulled towards the Earth, causing it to be heavier on one side and egg-shaped.
Because the Moon has no atmosphere, its surface is susceptible to intense pummeling by space rocks. Most of the objects that invade Earth’s atmosphere burn up before reaching its surface. And without an atmosphere, very little surface erosion occurs and the craters that are visible on its surface today remain everlasting scars dating back to 4.1 and 3.8 billion years ago. The footprints that that were created by astronauts will also remain there for millions of years.
However, this does not mean that the Moon is totally dead (geologically speaking, that is). Sometimes tiny fractures appear at the surface and release gas. This leads many scientists to believe that the Moon probably had a core that is hot and perhaps partially molten, similar to that of Earth’s. However, the data from NASA’s Lunar Prospector spacecraft showed that the Moon’s core is small, and between 2 to 4 percent of its entire mass. Compared to Earth, which the iron core makes up 30 percent of its mass, this is tiny.
The Tides of the Moon
Every object in space, regardless of its size, has gravity and the Moon is no exception to this rule. The Moon’s gravity is about 1/6 of the strength of Earth’s and a person who weighs 100 pounds on Earth would only weigh 17 pounds on the Moon. However, despite its weak gravitational force, the Moon’s gravity still has an effect on the Earth. Along with the Sun, the Moon has an effect on the ocean’s tides. The water, which is fluid, is attracted by the Moon and Sun’s gravitation pull, and this is strong enough to pull it slightly towards it, causing tides. The Earth’s gravity, on the other hand, pulls the water back, creating a never-ending cycle of pushing and pulling.
The highest tides are created when the Sun and the Moon are aligned so they are on the same side of the Earth. This usually occurs when there is a full Moon or new Moon in the Spring, and these tides are appropriately called Spring Tides. The lowest tides, however, are a result of when the Sun is at a right angle to the Moon, and these are called Neap Tides.
Phases of the Moon
If you look up at the Moon at different nights, you may realize that the Moon appears to be changing shapes. However, the Moon does not actually disappear or shrink to the size of a crescent, but this is rather a result of the shadows that are cast upon the Moon. The part of the Moon that is lit depends on the position of the Moon and Earth in relation to the Sun. Because of this, you can always tell what side the Sun is in relative to the Moon. For instance, if the right side of the Moon is lit, the Sun is therefore on the right side of the Moon.
When the Moon is not visible at all, it is called a New Moon. This is because one side of the Moon is always facing us and the Sun is shining directly on the side that we cannot see from Earth. This side is often called the Dark Side of the Moon. However, this is a bit of a misnomer as light from the Sun does shine on it and it isn’t always dark; we just don’t see it. As the Moon gets brighter and gradually progresses to a Full Moon, it is called a Waxing Moon. Then it has finally become a Full Moon, after 14 days, it begins to darken again and this is known as a Waning Moon. As it takes the Moon about a month to go around the Earth, this progress takes about a month as well.
The Moon, a Planet?
Unlike most planet/moon systems, where the moons are substantially smaller than the planet, the Moon and the Earth are relatively close in size. Out moon, which is larger than Pluto, has a diameter of 2,140 miles, 27% of the diameter of the Earth; its mass is 1/81 of the Earth’s mass; and its density is about 3/5 of the Earth’s density. Because of this, many people consider the Earth and Moon to be a double planet system rather than a planet/moon system. The moon also does not actually revolve around the Earth; it revolves around the Sun in concert with the Earth. Pluto, which is the only other planet to have only one moon is also thought to have a double planet system as well.
However, despite this fact, many people will continue to regard our moon as simply the Moon.’