Science and Technology

What is the moon?

Full moon

The dark night sky seems very pleasant and beautiful due to the presence of twinkling stars on it. A dim light of the stars on the dark sky looks like a diamond on it. The beauty of the whole scene becomes more enchanting due to the presence of the glowing moon. It holds a unique and different beauty. Just like the sun looks attractive for skywatchers during the daytime, the moon presents the same view at night but with some more added beauty. You can’t watch the sun directly without any protective covering on your eyes. But viewing the moon from our backyard gives a sense of peace to wonderers. The interesting fact about it is that it never remains the same in size, shape, and glow. From the start of the month if you will examine it, every day it comes up with a different view.

A full moon with its rocky surface
Full moon

Starting from a thin thread-like appearance it reaches a beautiful whole appearance on the 14th day of the month. On this day its beauty is at peak and then it again starts decreasing at the end of the month. Probably the peace during nights is at its expense. The whole scenario is enchanting but have you ever wondered that why it happens? What exactly does this celestial body is which seem totally different from the rest of the sky? How this increase and decrease in its size and brightness is happening? In this article, we will have a detailed discussion about satellites. Also, we will explain the decrease and increase in its size and shape.


Moon is like a companion of our earth and it accompanies it constantly. It is one of the celestial bodies that you can find in the sky easily. The whole rhythm and phases of the moon that skywatchers observe in the sky, have guided us for decades. Our calendar is based upon it. From the time it appears in the sky till the end it comes like a whole celestial body is associated with sequencing the calendar. However, there are some mysterious facts about the moon. Like how it will be visible in the sky depends upon its position with respect to the earth and Sun.

As it orbits our earth so it is known as a satellite. The diameter is about 2159 miles or 3475 Km.  Also, it is bigger than Pluto. There are four other moons, present in our solar system and they are bigger than our moon. Moon’s size is almost more than the 27% size of planet earth. Obviously, it is a great mess and has a prominent impact on our solar system. Perhaps it is also associated with the formation of the universe as well as making life possible on this planet earth.

How the moon was formed?

There are various theories given by various scientists to know its origin. Recent evidence shows that, due to a large collision, the earth was there in molten form. A small chunk got separated for sending the raw ingredients to form the moon at the end. Scientists have predicted that it was almost 10% mass of the earth. Also, it was equal in size to Mars. As we know the earth and moon are very alike in their composition, so the process have must occur about 95 million years ago.

a molten mass of earth and giant impact of earth to form moon.
Giant impact hypothesis

Our solar system is about 4.5 billion years old. So the formation of the moon was after the formation of the solar system. In this way, it is about 32 million years old. This theory has been supported further in 2015 after finding some more shreds of evidence. Scientists have used planetary orbits to detect its presence. This theory is known as the large impact theory. It is one of the most dominant theories in Astronomy. There are many other ideas such as our earth has captured the moon. Maybe it has stolen the moon from Venus.

Composition of the moon:

There is a very small core at the center of the moon which comprises almost 1% to 2% mass of the whole celestial body. Roughly, its width is 680km or 420 miles. Most of the mass of earth consisted of iron but there are many other important elements such as a large amount of Sulfur is present in it.

A representation of various layers of moon
Moon composition

The moon’s mantle is rocky and 825 miles thick. It is made up of dense rocks which are rich in magnesium and iron. There is a past interesting event about it in which magma which is present inside the mantle made its way to the top surface. As the result, an erupted volcano happened about four billion years ago. The crust of the moon is about 42 miles deep. The outer part of the crust is broken due to large incidences that it had to endure. The outer part is broken or shattered but the inner depth is intact due to the presence of outer protective covering. The intact material is present about 6 miles deep.

There are four innermost rocky planets in our solar system and our moon is a replica. Moon has been impacted by the hitting of various asteroids but as there is no weather on the moon, these craters have not eroded.

The average composition of the moon:

By weight our moon consists of 20% silicon, 43% oxygen, 19% magnesium, 3% calcium, 10% iron, 0.42% chromium, 0.12% manganese and 0.18% titanium. A spacecraft that is orbiting around our moon has given us various pieces of information such as the presence of water there. Probably, it has been originated from deep underground. There are several pits and scars on the surface. It seems that these pits can provide room for researchers to stay on it for the long term. There is ongoing research by LRO which shows that on the south pole of the moon, there is abundant water. This water quantity is comparable with the dry desert. A recent study in 2017 shows that in the interior of the moon there may be abundant water as compared to the poles.

Is there is any atmosphere on the moon?

Yes, there is an atmosphere on the moon but it is very thin. It is a thin layer of dust that is so thin that if there is a footprint on the surface of the moon it can stay for centuries. As there is no atmosphere, so no heat is constricted near the surface. As the result, temperature varies widely. During day time, the temperature is very sunny and it reaches up to 273 degrees. On the other hand, nights are extremely cold and the temperature reaches up to minus 153 degrees.

How do tides occur when the moon orbits our earth?

In order to understand the concepts first consider some of the statistics from NASA.

  • The average distance of moon from our earth is 384, 000 km.
  • The closest approach to earth is 363, 300 km.
  • The farthest distance from the earth is 405, 500 km (Perigee).
  • The circumference of the orbit is 2,413,402 km (Apogee).
  • The mean velocity of the orbit is 3, 680.5 kph.

The rise and fall in the sea level are because of the moon’s gravity pull at the earth. It is known as tides. Tides also occur in the atmosphere, lakes, and earth crust to a small extent. In high tide, the water level comes up to the earth’s surface, and in the lower tide, the water level drops. The site of the earth which is near to the moon faces high tide and lower tide occurs at the other site which is farthest from the moon.

earth tide due to gravity of moon.
Earth’s tide

Tidal braking:

The tidal braking is also because of the tides. The gravitational pull of the moon is slowing down the rotation of the earth around its own axis. As the result, there is an increase in the day length by 2.3 million seconds per century. So e of the energy of the earth is lost in this process and captured by the moon. It increases the distance of the moon from earth. It means that it goes away by 1.5 inches per year. The gravitational pull of the moon has also made life to be possible on planet earth. It moderated the wobble in the earth’s axial tilt. As the result, there is a stable climate for billions of years and life is likely to flourish on this planet.

Is there is any season on the moon?

As we know the earth is orbiting around the sun. But earth is not present in an aligned manner rather it is tilted away from or towards the sun about 23.5 degrees. As the result, solar radiations reach the earth’s surface differently and we will see various seasons around the year. But in the case of the moon, the tilt is only 1.5 degrees. So there are no noticeable seasons on the moon. One side of the moon experiences radiations and the other side remains in shade.

How does lunar eclipse occur?

For a lunar eclipse to happen the earth, moon and sun align in a perfectly straight manner. During rotation when the earth is exactly between earth and moon, it causes an eclipse. An earth’s shadow is cast on the surface of the moon. It can only occur when the moon is full rather than half or quarter.

A beautiful representation of moon due to earth's shadow
Lunar eclipse

Why moon increase or decrease in size?

It does not actually change its size. Rather it is only the part of the moon that is visible to us from the earth as it orbits the earth.

Wrapping up/ Conclusion:

Moon is one of the most prominent celestial bodies in the sky. It is a permanent companion of our earth and orbits around it. The outer crust of the moon is rocky and has experienced various cracks from various past events. There is a very thin atmosphere on the moon so a footprint on the surface of the moon can stay for a century even. Also, the tilt of the moon is very less as compared to the earth so you will not experience a remarkable variation in seasons over there. A lunar eclipse is also one of the interesting events in which the earth, moon, and sun are aligned in a perfectly straight manner. The earth’s shadow is cast on the surface of the moon and skywatchers will observe the lunar eclipse.

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