Category Man and the Moon

          The Moon does not appear in the same shape every day, it is ever changing. On some days, it looks like a shining disk, on some days it looks like an elongated C. These different shapes of the Moon are called the phases of the Moon.

          The orbiting of the Moon around the Earth is the secret behind the different phases of the Moon. We already know that the Moon has no light of its own. As the Moon moves around the Earth, different parts of it are lit by the Sun, thus causing different phases. In a fortnight’s time, the Moon goes from full moon to new moon.

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          The Apollo astronauts placed instruments known as seismographs on the Moon to study about its interior. What we know about it now comes primarily from their studies.

          The Moon is made up of different layers like any other celestial body. It has an outer crust, an inner mantle and an innermost core. The outer crust is hard, dry and dusty. It is almost 60 kilometres thick in the near side while it is almost twice as thick in the far side.

          The mantle has a thick layer of rock at the exterior and is semi-rigid in the interior. The mantle runs down almost 800 kilometres. The Moon’s core is constituted of rocks rich in iron.

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          Scientists have special terms to indicate each scientifically relevant object around us. At times, these words may confuse an ordinary person as scientists often use big words that are difficult for a common man to understand. For instance, the scientific term for dry skin is xerosis. Similarly, lunar soil is known as lunar regolith among scientists.

          Lunar regolith is formed as a result of comets or meteorites that fall on the surface of the Moon. It is rich in oxygen and various metals. The thickness of the regolith varies from one place to another; it is three to five metres thick in the Maria, while the thickness in the highlands is ten to twenty metres.

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          The temperature on the Moon is not constant; it varies from boiling hot to freezing cold, depending on the position of the Sun. The Moon has no atmosphere to either trap the heat or to insulate its surface.

          A day on Earth is 24 hours. Daytime on the Moon is thirteen and a half Earth days long. A long night of thirteen and a half days follows a Moon’s day. When sunlight hits the surface of the Moon during the day, the temperature can go up to 127 degree celsius. In contrast, the temperature on the Moon can drop to minus 173 degree celsius during the night.

          The temperature at the Moon’s core is much higher than its surface temperature. However, there are regions on the Moon that never receive sunlight. This is because of the slight tilt of its axis. Unlike Earth, the Moon doesn’t have different seasons either.

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          If you take a compass to the Moon, it would not point northwards. It is not because your compass is faulty. A compass shows directions in alignment with the Earth’s magnetic field. We already know that the Moon has a very weak gravitational field. It does not have a strong magnetic field either. To understand this better, let us take a look at how the Earth’s magnetic field is formed.

          The core of the Earth is filled with hot liquid iron. This molten iron swirls as our planet rotates, thus producing the Earth’s magnetic field. The Moon’s core is less dense than the Earth. Therefore, the Moon’s core may contain only a little amount of metal; this might not even be heavy iron. On the Moon, the fluid motion of the conducting material is either very less or not present at all. As a result, the Moon has a weak magnetic field compared to that of Earth. It is around one hundredth of the Earth’s magnetic field.

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          The Moon has a dark side. Don’t worry; we are not talking about anything evil here. The side that faces away from the Earth is known as the Moon’s dark side. This is because of the shape of the lunar orbit.

          We know that the lunar orbit is elliptical. As a result, the Moon travels at different speeds at different points. Because of this, we can see more than half of the Moon’s surface. This phenomenon is known as libration. About 59 per cent of the Moon’s surface is visible from the Earth because of this phenomenon. Johannes Hevelius studied librations in detail and published his findings in 1647. His work was titled Selenographia.’

Picture Credit : Google