Everything about moon

Moon

The Moon is Earth's only permanent natural satellite. Twelve people landed and walked on it in the 1960s and 1970s. They collected and brought back rocks that were studied to find more about the Moon.

How big is the Moon?

The Moon is 3,476 km wide. This is just over a quarter of Earth's diameter. That makes the Moon a relatively large one. Most other planets are much larger than their moons. Because of this, the Earth and the Moon had been called a double planet.

What is its surface like?

The Moon does not have any air or liquid water. There is no life on the Moon. During the day it becomes very hot. At night it grows icy cold. A person going to the Moon needs an air supply and a special suit.

The Moon has many craters. The largest one is the South Pole-Aitken Basin that is on the far side and in thesouth hemisphere. It is 2,240 km across. Some of the craters have bright rays around them. They were made by material thrown up by the impacts that made the craters. Those craters are the younger ones. The bright rays of older craters faded because of impacts of tiny meteors over millions of years.

There are dark areas called maria. They are soldified lava flows that filled up large craters long ago. Most maria are on the near side and there are only a few on the far side. There are also lighter-colored highlands. The surface is covered by dust called regolith. It is thinner on the maria and thicker on the highlands. The Moon's regolith was made by pieces of rock that got thrown up by impacts.

There might be water ice in the floors of craters near the south pole. The bottoms of those craters are always dark because they are in the shadows of the crater rims. The ice came from comets that hit the Moon.

How long is a day and a year on the Moon?

It takes the Moon 27.3 Earth days to rotate once and to make one orbit. So, the Moon always keeps the same side faced towards Earth. That side is called the near side. It is the side with lots of maria. The other side is the far side. Nobody saw the far side until it was photographed in 1959 and first seen by astronauts in 1968.

What are the phases of the Moon?

The Moon looks different at different times. This happens because the Sun lights up different parts of the Moon as the Moon moves in its orbit. This is called the phase of the Moon.

When the Moon is between Earth and the Sun, the side facing away from Earth is light up and the side we see is dark. This is called a new moon because people in many cultures used it to mark the beginning of a new month. When it is behind the Earth, the side we see is light up. This is called a full moon.

When the Moon is halfway between new moon and full moon, we see one quarter of the Moon. This phase is called the first quarter. When the Moon is halfway between full moon and new moon, we see a quarter of the Moon again, but the opposite quarter from what we see at first quarter. This phase is called the third quarter because the Moon had gone three quarters the way around its orbit from the new moon position.

When the Moon is between either one of the quarter phases and new moon, it is in a crescent phase. It is shaped like a banana or a cow's horns. When the Moon is between either one of the quarter phases and full moon, it is in a gibbous phase. The unlit part as seen from Earth is crescent shaped.

The cycle of phases does not match the Moon's 27.3 Earth day orbit. This is because the Moon makes one orbit in 27.3 days if you use the faraway stars to keep track of the Moon's position. The Earth is moving in its orbit around the Sun. While the Moon makes its orbit, the Earth moves ahead of it. The Moon needs extra time to catch up with the Earth and complete the cycle of phases. The complete cycle of phases takes 29.5 days. This is why we use 30 days, not 27 days, as the average length of the month.

An interesting thing happens sometimes when the moon is a crescent phase. The Earth can reflect enough sunlight to the Moon to make the noramlly unlit part be dimly light. This is called earthshine. If that dim lighting cannot be seen, it could be viewed by letting a camera collect enough light to make the dim part look brighter in the picture.

What are eclipses?

Why can we see the full moon if it is behind the Earth as seen from the Sun? Why can we get sunlight at new moon if it is between the Sun and the Earth? The Moon doesn't always get blocked out by Earth's shadow at full moon and it doesn't always block the Sun at new moon because the orbit of the Moon is tilted. This tilt usually makes the Moon be above or below the Sun at new moon or the Earth's shadow at full moon.

But sometimes when things are lined up right, eclipses happen. There are two main kinds of eclipses. When the Moon does block the Sun, it is called a solar eclipse. They can be viewed with special filters to keep people from hurting their eyes. Unfortunately, when a solar eclipse occurs, only a few people can view a total eclipse, as the part of the Earth that is dark from the eclipse is only in a small area of the world.

One of the unique things about the Earth's Moon is that the apparent size (how big you see something when you look up into the sky) of both the Moon and the Sun are almost identical. This results in some very spectacular views when this occurs, especially when you are in the part of the world where the eclipse is total. In addition to seeing eruptions of gases from the sun called prominences, you can also see the corona of the sun. This is a region of very hot gasses that are escaping from the sun and form the solar wind. This particularly interesting because normally the photosphere of the Sun keeps you from being able to see the corona, and many astronomers try to do scientific measurements of the corona during an eclipse.

When the Moon does go through the Earth's shadow, it is called a lunar eclipse and it can be viewed with the eyes. Because the Earth is so much larger than the Moon, a lunar eclipse can usually be viewed by just about half of the people on the Earth when they occur, and happen about twice a year. Before and after the moon enters the shadow of the Earth, it turns to a reddish color. This is due to the fact that the blue colors of sunlight are scattered in the atmosphere and the red light is able to go through much more air. This is exactly the same as what you see during a sunset or sunrise, except on the moon this is light that is going through the Earth's atmosphere.

Other planets with moons can have eclipses too. Shadows of moons have been seen on the surface of other planets, and those moons go into the shadow of those planets as well. When a planet goes between us and the Sun, it is called a transit. These usually are not noticed by anybody due to sunlight dimming (unlike an eclipse of the Moon), but can be seen with telescopes that have special filters to keep the sunlight from hurting your eyes.

How does the Moon cause tides?

The ocean tides are caused by gravity. The closer you are to the Moon, the stronger the pull of gravity. The ocean facing the Moon is closer than the middle of the Earth. It is pulled more strongly by gravity. The ocean is pulled into a bulge called a tide. The places where the ocean bulges is a high tide. In between is the low tide.

The other side of the world feels the weakest pull from the Moon. Here the Earth is pulled more strongly than the ocean. The Earth moves away from the water. This makes the ocean bulge out on this side as well. In between these two bulges, the oceans of the world are lower.

Both the Moon and the Sun cause tides, but the moon's is much stronger. This is because the Moon is much closer to the Earth, so it's gravity changes more quickly from strong to weak on the opposite sides of the Earth. The Sun, being much further away, has a less variable gravity strength. As the Earth turns, the tides always point toward the Moon and Sun.

The biggest tides happen when the Earth, Moon, and Sun line up. These are called spring tides. They occur at the new moon and the full moon. In between the tides are lower. The weakest tides are called neap tides. Here the pulls of the Moon and the Sun cancel each other out.

What is the moon made of?

The silicate crust is about 60 km thick on the near side and 100 km thick on the far side. It is thinner under the maria and thicker under the highlands. It is thought that the near side has more maria than the far side because the thinner crust made it easier for lava to flood craters. There is a silicate mantle and a small core 600 to 850 km across.

No one knows exactly how the Moon was made, although scientists have several theories. Some scientists think that the Moon was made very early in the life of Earth (when the earth was about 50 million years old). A planet about as big as Mars hit the young Earth. The collision had so much energy that the Mars-sized planet was completly destroyed. Also much of the earth's crust and mantle was vaporised. Some of the debris formed a ring around the earth and eventually was pulled together by gravity to form the moon. The rest of the colliding planet and young Earth merged to became the modern Earth.

All this happend billions of years ago. The idea was suggested by things like the small size of the Moon's core and comparisons of what the Moon and Earth are made.

How much would the Moon's gravity pull on me?

If you were on the Moon, it would pull you down with a force about one sixth as strong as the force of Earth's gravity. This allowed the people who visited the Moon to lift rocks that they could not lift as easily if they were on Earth.

Who is moon named after?

Moon and Month both come from the same old Greek word Mene for the moon. Monday follows Sunday as the Moon follows the Sun. Interestingly the Latin name Lunar is used in many languages so Lundi is french for Monday.

Other names had been used for the Moon such as Selene and Luna. Selene is the Greek goddess of the Moon. Luna is the Roman name of the same Goddess. Diana is also usually associated with the moon.