My Science School

 

          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

 

          Many planets in the solar system have natural satellites. But Earth and its natural satellite share a special relationship.

          The Moon is Earth’s only natural satellite. Though our Moon is small when compared to the moons of Jupiter or Saturn, its size in relation to that of Earth is quite large.

          Along with revolving around the Earth, the Moon also revolves around the Sun in sync with the Earth. They look more like two sister planets than a planet and its satellite.

          Therefore, together, the Earth and the Moon are considered as a double planetary system.

Picture Credit : Google

 

          The Moon has a near side and a far side. The side that permanently faces the Earth is known as the near side while the side that faces away is known as the far side. Though these sides are so, the amount of sunlight they receive is almost the same.

          The surface of the near side differs from the far side; the near side is covered by large patches of dark areas. Early scientists proposed that these dark areas were seas with water. The dark patches are still known as seas. The far side does not have such seas. The crust here is thicker than the side facing the Earth.

Picture Credit : Google

 

 

          The Earth takes 24 hours to complete one rotation. But the Moon’s rotation is not that short; it takes 27 days, 7 hours and 43 minutes for the Moon to complete one rotation.

          The Moon’s axis is similar to that of the Earth; it is tilted towards one side. The Moon completes one round in its orbit around the Earth in almost the same time taken for one spin.

          Since the time taken for both movements are the same, the Moon always keeps the same side facing the Earth. This means that we get to see only one side of the Moon.

Picture Credit : Google

 

          The Moon’s orbit is elliptical; it is shaped like a flattened circle. Because of this shape, the distance between the Moon and the Earth is different at different positions and it varies as it moves around the Earth.

          When the Moon is closest to the Earth on its orbit, it is said to be at perigee. The word perigee is of Greek origin and means ‘near Earth’. At perigee, the Moon is 356,400 kilometres away from the Earth.

          The word apogee comes from a Greek word that means ‘far from Earth’. When the Moon is at the farthest point from Earth in its orbit, it is said to be at apogee. At apogee, the Moon is 406,700 kilometres away from the Earth.

Picture Credit : Google

          The Moon is the biggest and brightest object that one can spot on the night sky. It appears quite large because it is the closest celestial body to Earth.

          The equatorial radius of the Moon is around 1737 kilometres and the equatorial diameter is about 3472 kilometres. It is almost one-fourth the size of Earth. You can roughly fit in four moons inside the Earth. The Moon’s surface is as big as North and South America put together. According to NASA, “if Earth was the size of a nickel, the Moon would be about as big as a coffee bean.”

          The Moon is not a perfect sphere, just like the Earth. It is slightly flattened towards the poles. The diameter of the Moon from pole to pole is lesser than its equatorial diameter.

Picture Credit : Google

          Poets often describe the silvery moon. But, the Moon doesn’t always appear silvery; it is sometimes white, sometimes yellow, grey or even red at times.

          When the Moon is low in the sky, it is closer to the horizon. The light that travels through the air scatters near the horizon as it passes through a thick layer of atmosphere. As a result, the Moon looks yellowish or orange at times. When the Moon is high in the sky, the scattering effect is much lesser and it appears whitish. During a total lunar eclipse, the Moon appears to be red; this too is caused by the scattering of light. The colours of the Moon give us clues about the minerals present on its surface.

Picture Credit : Google