The moon, so unpredictable yet so predictable. We know it will be there every night but then, it disappears every once in a while. Sometimes, it appears extra-large, sometimes a bit too small. It adorns the night sky with its unparalleled beauty. Why is it that the moon appears smaller or bigger every day? Why does it change shape? Does it have something to do with its revolution around the earth? How long does it take for the moon to revolve around the earth? Do the phases of the moon and the time it takes to revolve around the earth have some relation to each other? All your questions will be answered in the article to follow. So, stay tuned!
How Long Does It Take For The Moon To Revolve Around The Earth?
To complete one revolution around the Earth, the moon takes 27.3 days in absolute terms. This is called the sidereal period. But, since the earth rotates in the counter-clockwise direction and the moon revolves around the earth in the same direction, there is a bit of overlap between the two. Thus, the relative synodic period amounts to 29.5 days. These 29.5 days constitute a lunar month or one complete cycle of the moon, in which we witness the full moon, new moon, crescent moon, etc.
The Lunar Month
The Lunar month or the 29.5 days have two phases – the waning phase and the waxing phase. The waxing phase is when the moon keeps on growing in size while the waning phase is when the moon keeps getting smaller after the full moon night. When the moon falls between the Sun and Earth during the course of its revolution around the earth, it is called a new moon, as the moon is not visible due to no reflection on sunlight. When the earth lies exactly between the Sun and moon, it is a full moon and we can see the moon in its full glory.
Fun Fact:
The Hindu calendar is based on the lunar month. All Hindu origin festivals follow the lunar cycle and are celebrated on specific days depending on the phase of the moon. Also, Muslim festivals like Eid follow the lunar cycle and fall specific lunar phases.
Moon’s Revolution Around The Earth
The Moon revolves around the earth in an elliptical orbit. The interesting thing about this orbit is that it doesn’t follow a straight path, rather it is inclined with respect to the equator of the earth. This is the reason that the moon appears bigger or smaller on certain days. These are known as supermoons or micro moons. A supermoon and micro moon might vary by about 30% in brightness and 14% in their sizes. The supermoon is seen at the Perigee position of the lunar orbit when the moon is closest to earth in the orbit whereas the micro moon appears at the Apogee positions when the moon is farthest from Earth in its orbit. These correspond to the extreme ends of the minor and major axis of the elliptical orbit, respectively.
What is more interesting is that along with the revolution of the moon in its orbit, the orbit itself also rotates. This is the reason that we see the difference in sizes on the moon, not just the phases. This is also the reason for the continuous flux in the position and size of the moon. This is what keeps the moon fascinating to us no matter how many times we look up at it in the night sky. The orbit takes around 8.85 years to complete one full rotation. So, we can expect the lunar behaviors to repeat every 8.85 years.
Why Is The Moon’s Revolution Significant?
As discussed above, many of the religions follow lunar cycles to set dates for festivals and auspicious occasions. Also, in Hindu mythology, a person’s birth and the position and phase of moon and planets determine their whole lifetime. This is up for speculation but is nonetheless believed by horologists and astrologers. Apart from all this, the moon’s revolution gives rise to the full moon, new moon, and eclipses which form the basis of many of the fictional and supernatural beings that we read about. Wouldn’t life be boring without the touch of these fantasies? And this fiction would not exist without the qualities of the moon as they are due to its revolution.
It is thus fascinating to read and study about the moon because it never fails to amaze us. It is ever-changing and keeps us hungry for more knowledge. It keeps us on our toes to know more about the various tales associated with it. If you have any queries regarding how long the moon takes to revolve around the earth, let us know in the comment below.
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