After analyzing the movements of the earth and the consequences it has for us, we will analyze the movements of the moon. The moon is our natural satellite and it also orbits and rotates on itself. The different types of movements it has and the closeness or distance of its position with respect to planet Earth determines the time interval of the day, days, weeks, months and even the year and largely affects the tides, as you can see in the article about the tides and the moon.
Therefore, in this article we are going to study in depth what are the movements of the moon and what consequences it has for life on Earth.
What movements does the moon have?
Since there is a gravitational attractive force between the moon and the Earth, there are also natural movements of this satellite. Like our planet, it has two unique movements known as rotation on its own axis and translation in an orbit around the Earth. These movements are those that characterize the moon and are related to the tides and moon phases.
During the different movements he has, he takes some time to finish them. For example, a complete translation lap takes an average of 27,32 days. This makes, curiously, the moon always shows us the same face and seems to be totally fixed. This is due to numerous geometric reasons and another type of movement called lunar libration that we will see later.
When the Earth revolves around the Sun, the Moon also revolves around the Earth, eastward. The distance from the Moon to the Earth during its movements varies greatly. The distance between the planet and the satellite is 384 km. This distance varies completely depending on the moment it is in its orbit. Since the orbit is quite confusing and at times remote, the Sun has a considerable influence with its gravitational force.
The nodes of the moon are not fixed and move 18,6 light years away. This makes the lunar elliptical non-fixed and the perigee of the moon occurs for every 8,85-year turn. This perigee is when the moon is in its full phase and is closest to its orbit. On the other hand, the apogee is when it is farthest from orbit.
Moon rotation and translation
The movement of our rotating satellite is synchronized with that of translation. It lasts 27,32 days, so we always see the same side of the moon. This is known as the sidereal month. During its rotational movement It forms an angle of inclination of 88,3 degrees with respect to the plane of the elliptical of translation. This is due to the gravitational force that forms between the moon and the Earth.
During its translational motion around Earth, it is tilted about 5 degrees with respect to the ecliptic. It takes the same amount of time to complete a complete revolution as it does around itself. This movement around the planet is what forms the different tides we have today, something you can explore in more depth in the article on storm surges.
The other movement that the moon makes is that of revolution. It is about the rotation that the moon has on the Sun. This movement is done in conjunction with our planet, as it rotates on itself and moves in orbit around the Earth.
Consequences of the movements of the moon
As a result of these lunar movements, we have some types of months that you may have heard mentioned but that you do not know very well. We are going to explain them one by one.
- Sidereal month. It is the one that lasts 27 days, 7 hours, 43 minutes and 11 seconds. This month occurs when the phase of the moon has completed a complete circle. The hour circle is the maximum on the celestial sphere.
- Synodic month. It is the time it takes to pass two equal phases and usually lasts 29 days. It is also known by the name of lunation.
- Tropic month. It is about the time where there are two steps followed by the moon by the circle of the point of Aries. It usually lasts 27 days.
- Anomalistic month. It lasts 27 days and 13 hours and is when there are two consecutive phases in the perigee.
- Draconic month. It is the time it takes from one phase to another of the moon to pass through the ascending node. It lasts 27 days and 5 hours.
Lunar libration
It is a movement that the moon has by which we can only see 50% of its surface or the same face always. There are, in turn, three types of libration. We are going to analyze them in depth.
- Libration in latitude. It is related to the inclination between the orbit of the moon and the plane of the elliptical. This makes it possible to only see the north and south of the moon at the same time. The point of the plane of the equator of the moon is above and below the plane of the orbit. This guarantees us that there is more surface to observe from the opposite polar region.
- Daytime libration. In this part it has a lot to do with the position where the observer is when capturing the image of the moon. There are many geometric aspects to consider.
- Libration in length. It is due to the fact that the rotation movement of the moon is totally uniform, while the translational movement is not. This makes the perigee the part where the moon moves the fastest and the apogee the slowest. Something similar happens with the Earth and its orbit around the sun when it is in the aphelion and perihelion. As a consequence of this movement we have a swing towards the West, making it possible for us to only see a single face in the eastern and western regions of the moon.
It can be said that the lunar libration is the point that is located on the surface of the moon and is where the 3 types of libration occur. Apparently it causes it to move in a spiral fashion and does not return to its original position.
I hope this information helps you to know more about the movements of the moon.
