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The Moon – Facts, Phases, Surface, Eclipse

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Celestial bodies include planets, stars, the moon, and other celestial bodies. Astronomy is a field of science concerned with the study of heavenly bodies and their phenomena. One of the findings of celestial bodies that we may create is the shift in the appearance of the moon every day. 

  • The full moon day is the day when the whole disc of the moon is visible, while the new moon day is the day when the whole disc of the moon is visible. The full moon day is when the whole disc of the moon is apparent.
  • The new moon day is when only a small part of the moon is visible. The phases of the moon are the various outlines of the light portion of the moon seen over the course of a month.
  • The time gap between the full moon and new moon day is of 15 days only.

Since we can only see the aspect of the moon that projects the Sun’s light towards us, the phases of the moon exist.

Celestial Objects 

Celestial bodies are all-natural bodies seen in the sky outside the earth’s atmosphere. Eg, stars, planets, and their moons, as well as comets, asteroids, etc. The moon is the celestial body closest to Earth.

Stars are celestial bodies that emit their own light. Our sun is a star as well.

The Moon

The moon is a natural satellite of the earth that orbits around it in a fixed orbit, as we all know. Other planets in the solar system, including Earth, have their own moons or natural satellites. Furthermore, the moon does not emit any light of its own but rather mirrors the light that falls on it from the sun.

The motion of the Moon around the Earth and the Sun

Some important facts to know about the moon

  • At one-quarter the diameter of Earth it’s the most important natural satellite, and therefore the fifth largest satellite within the system overall.
  • Orbiting Earth at a mean lunar distance of 384,400 km or about 30 times Earth’s diameter, its gravitational influence is that the main driver of Earth’s tides and slightly lengthens Earth’s day.
  • The Moon is assessed as a planetary-mass object and a differentiated rocky body and lacks any significant atmosphere, hydrosphere, or magnetic flux.
  • Its surface gravity is about one-sixth of Earth’s; Jupiter’s moon is that the only satellite within the system known to possess a better surface gravity and density.
  • The Moon’s orbit around Earth features a sidereal period of 27.3 days and a synodic period of 29.5 days. The synodic period drives its lunar phases, which form the idea for the months of a calendar.

However, as the moon orbits the earth, the part of the Moon that faces the sun becomes illuminated, while the rest remains dark. As a result, the moon takes on various forms in the sky. The ‘Phases of the Moon‘ are the patterns of the illuminated portion of the Moon.

Phases of the Moon

The phases of the moon are the different images of the illuminated portion of the moon as seen from Earth. It takes about 29 days to cycle from a full moon to a new moon to another full moon. 

The moon does not emit its own light, but rather mirrors the Sun’s. Various parts of the moon’s atmosphere are illuminated and different shapes are seen every day as it orbits around the earth.

Phases of the Moon

As seen in the diagram above, there are eight main moon phases.

  1. Full Moon Day: A Full moon day occurs when the whole moon is observed in the sky. For this very day, the moon is bathed in sunshine. As the moon rotates and shifts its shape, the area exposed to sunlight reduces, giving the illusion that the moon is becoming smaller.

  2. New Moon Day: Due to its location behind the Earth, the moon becomes totally transparent on the 15th day of a Full Moon, so no sunlight falls on it. This is known as a New Moon Day. 

  3. Crescent Moon: The image of the moon observed as the first quarter or the third quarter is called as Crescent moon. This is observed on the next day the moon that appears in the sky is known as a crescent moon. From this day, the moon starts growing larger until the 15th day when it reaches its full shape, that is, the Full Moon Day comes.

  4. Waning phase of the moon: Waning is the phase of the Moon in which it decreases in size. The waning moon can be of two types: Waning Gibbous Moon and Waning Crescent Moon. 

  • The Waning Gibbous Moon is the next intermediate Moon period. During this time, the illumination of the apparent part of the Moon decreases.
  • During the Waning Crescent Moon period, the Sun illuminates less than half of the apparent portion of the Moon, and earthshine can be seen on the remainder of the Moon at the end.

  5. Waxing phase of the moon: Waxing is the phase of the moon in which it increases in size. The waxing moon can be of two types: Waxing Gibbous Moon and Waxing Crescent Moon. 

  • After the New Moon, the first intermediate period, the Waxing Crescent Moon, begins as a small sliver of the Moon becomes apparent.
  • Waxing Gibbous Moon is the second intermediate phase, which lasts until the next main phase. Waxing indicates that it is growing in size. Gibbous refers to the Moon’s shape, which is larger than a semicircle but smaller than a complete circle at First Quarter.

Blue Moon

Every month, there is usually one New Moon. In certain months, though, there might be two new moons in a row. The Blue Moon is the second New Moon in a month. The phases of the Moon are significant in Indian society and culture because various festivals are observed in India according to the phases of the Moon.

How do we see the Moon?

  • We can see the Moon because it reflects the sunlight to us from its surface. During a month, the Moon circles once around the Earth. If we could look down on our system, we might see that half the Moon facing the Sun is usually lit. But the lit side doesn’t always face the world! Because the Moon circles the Earth, the quantity of the lit side we see changes. These changes are referred to as the phases of the Moon, and it repeats during a certain over and over.
  • A new phase of the moon, the Moon is lined up between the world and therefore the Sun. We see the side of the Moon that’s not being lit by the Sun in other words, we see no Moon in the least because the brightness of the Sun outshines the dim Moon. When the Moon is strictly lined up with the Sun as viewed from Earth we experience an eclipse.
  • As the Moon moves eastward far away from the Sun within the sky, we see a touch more of the sunlit side of the Moon each night. A couple of days after the new phase of the moon, we see a skinny crescent within the western evening sky. When half the Moon’s disc is illuminated, we call it the primary quarter moon. This name comes from the very fact that the Moon is now one-quarter of the way through the moon. From Earth, we are now watching the sunlit side of the Moon from off to the side.
  • The Moon continues to wax. Another time than half the disc is illuminated, it’s a shape we call gibbous. The gibbous moon appears to grow fatter each night until we see the complete sunlit face of the Moon. We call this phase the complete moon. It rises almost exactly because the Sunsets and sets even as the Sun rises subsequent day. The Moon has now completed one-half the moon.
  • During the last half of the moon, the Moon grows thinner each night. We call this waning. Its shape remains gibbous at now but grows a touch thinner each night. Because it reaches the three-quarter point in its month, the Moon once more shows us one side of its disc illuminated and therefore the other side darkly. However, the side that we saw dark at the primary quarter phase is now the lit side. Because it completes its journey and approaches a new phase of the moon again, the Moon may be a waning crescent.

The Surface of the Moon

  • The moon’s surface is barren, sandy and empty of water. It has a lot of big craters and tall mountains.
  • The gravity on the moon is six times heavier than on Earth. It doesn’t have any environment because it’s so weak. That is why we can’t hear on the moon’s surface.
  • The Moon’s atmosphere is devoid of vegetation and completely coated with gravel.
  • Throughout the Moon’s surface, there are craters or bowl-shaped cavities.
  • On the Moon, there are many steep and high mountains. Any of the mountains are as tall as the world’s tallest mountains. On the earth, there is no water and no wind.

Lunar Eclipse

When the moon, the Earth, and the Sun are together very close to each other, and the earth is right in the centre between the moon and the sun, a lunar eclipse happens. As a result, the earth’s shadow appears on the moon. Due to this, during a lunar eclipse, the moon reflects the light it absorbs from the earth rather than the light it receives from the sun. So, the moon takes on a reddish hue. As a consequence, during a lunar eclipse, the moon becomes reddish in color.

Lunar Eclipse

Sample Problems

Problem 1: Why does the sun look bigger than all other stars?


The sun looks bigger than all other stars because we see it from the earth, and it is the star that is nearest to the earth.

Problem 2: What things made the moon?


The composition of the Moon is a bit of a mystery. Although we know a lot about what the surface of the Moon is made of, scientists can only guess what the internal composition of the Moon is. Like the Earth, the Moon has layers. The innermost layer is the lunar core. It only accounts for about 20% of the diameter of the Moon. Scientists think that the lunar core is made of metallic iron, with small amounts of sulfur and nickel. Astronomers know that the core of the Moon is probably at least partly molten.

Problem 3: What makes the moon stay in its orbit?


The Moon, Earth’s natural satellite, seems to hover in the sky, unaffected by gravity. However, the reason the Moon stays in orbit is precise because of gravity – a universal force that attracts objects.

Problem 4: How craters are made on the moon?


Craters on the Moon are caused by asteroids and meteorites colliding with the lunar surface. The Moon’s surface is covered with thousands of craters. It also has very little geologic activity (like volcanoes) or weathering (from wind or rain) so craters remain intact for billions of years.

Problem 5: Why do astronauts float on the moon?


Gravity on the Moon is 1/6th the gravity on the Earth. That is why things can travel a much larger height on the Moon, and do not experience that much gravity, giving them the illusion that they’re floating. But eventually, they do fall to the surface, just like on Earth.

Last Updated : 12 May, 2021
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