When
we look at the Moon from Earth, we always see the same side. Until Lna 3 sent
back photos in 1959, no-one knew what the other side looked like. - The
Moon is nearly twice as big as the planet Pluto.
- The
"Man in the Moon" isn't always seen as a man. People from India see an old woman
with a spinning wheel. People from Mexico see a rabbit!
- The
Moon is not that small compared to the Earth. Sometimes
the Earth and Moon together are called a binary or double planet system.
| | |  | | | The
Moon is our nearest neighbour in space. | | |
How
big is the Moon?
Comparison
of the size of the Moon and the Earth Most
of the planets in the Solar System are much bigger
than their moons. The Moon is just under 3,500 kilometres (km) wide. This means
the Moon is not very small compared to Earth. So the Earth and Moon together are
sometimes called a binary or double planet system. What
is the distance from the Earth to the Moon?
The Moon is
approximately 238,800 miles from earth.
What
is the Moon's surface like?
Astronaut
Harrison Schmitt collecting rocks from the Moon during the Apollo XVII mission. The
Moon does not have any atmosphere. It also doesn't have any liquid water on its
surface. During the day it becomes very hot, but at night it is icy cold. A person
visiting the Moon needs an air supply and a special suit. The
Moon has many craters on its surface. The largest one is called the South
Pole-Aitken Basin and is 2,250 km across. That means it's about the same size
as the European Union! It is the biggest crater known in the Solar System. We
think nearly all the craters on moons or planets were made by huge rocks hitting
them a long time ago. They are called impacts. Some
of the craters on the Moon look as if they have rays coming out of them. These
rays are rocks thrown across the Moon by the impacts that made the craters. Some
of the craters around the bottom of the Moon may have ice in them. There
are also darker areas called maria (said "MARR-ee-ah"). These are large
pools of lava that cooled a long time ago. Most maria are on the side of the Moon
we see from Earth. The lighter areas on the Moon are highlands. Although
it is thought that the earth and moon have common origins, the density of the
earth is 5.52 grams per cubic cm while the density of the moon is 3.34 grams per
cubic cm. Where
did the moon come from? One
early theory was that the moon is a sister world that formed in orbit around Earth
as the Earth formed. This theory failed because it could not explain why the moon
lacks iron. A
second early idea was that the moon formed somewhere else in the solar system
where there was little iron, and then was captured into orbit around Earth. This
failed when lunar rocks showed the same isotope composition as the Earth. A
third early idea was that early Earth spun so fast that it spun off the moon.
This idea would produce a moon similar to Earth's mantle, but it failed when analysis
of the total angular momentum and energy involved indicated that the present Earth-moon
system could not form in this way. The
current theory states that when Earth formed 4.5 billion years ago, a Mars-sized
planet smashed into it. The impact melted the Earth's mantle––a young and delicate
mantle––and the debris from both planets headed off into space. Eventually that
debris coalesced into the Moon. How
long is a day on the Moon?The
Moon takes just over 27 Earth days to rotate (spin around) once. How
long is a year on the Moon?The
Moon also takes just over 27 days to orbit (move around) the Earth. This
is why we always see the same side of the Moon when we look from the Earth. We
call this side the near side. The other side we call the far side.
In 1959 a probe sent back pictures of the far side. That was the first time anyone
saw what it looked like. What
is the Moon made of?The
surface of the Moon is made of rocks and dust. It is about 70 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. There may be more maria on the near side because
it was easier for lava to flow into craters. We
think the Moon has a small core (center) about 300 km across. How
much would the Moon's gravity pull on me?If
you were on the Moon, it would pull you down about 1/6th as much as the Earth.
(That's why it was much easier for the astronuats visting the Moon to pick up
rocks there.) Who
is it named after?
The
goddess Diane, the goddess of the Moon in Roman mythology The
names "Moon" and "month" both come from the ancient Greek name for the Moon, "Mene".
There have been other names for the Moon, like "Selene" and "Luna". Selene was
the Greek goddess of the Moon. Symbol
for the Moon
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