The satellite of the Earth from prehistoric times attracted the attention of people. The moon is the most noticeable object of the sky after the Sun, and therefore it has always been attributed to it as significant properties as the daylight. Centuries later, worship and simple curiosity were replaced by scientific interest. The waning, full and growing Moon is today the objects of closer scrutiny. Thanks to the research of astrophysicists, we know a lot about the satellite of our planet, but a lot remains unknown.
Origin
The moon is a phenomenon so familiar that there is practically no question of where it came from. Meanwhile, the origin of the satellite of our planet is one of its most significant secrets. Today, there are several theories on this subject, each of which boasts both the presence of evidence and arguments in favor of its failure. The data obtained allow us to distinguish three main hypotheses.
- Moon and Earth formed from one protoplanetary cloud.
- The fully formed Moon was captured by the Earth.
- The collision of the Earth with a large space object led to the formation of the Moon.
Consider these versions in more detail.
Joint accretion
The hypothesis of the joint origin (accretion) of the Earth and its satellite was recognized in the scientific world as the most plausible until the beginning of the 70s of the last century. It was first put forward by Immanuel Kant. According to this version, the Earth and the Moon were formed almost simultaneously from protoplanetary particles. At the same time, cosmic bodies were a binary system.
The first began to form the Earth. After it reached a certain size, particles from a protoplanetary swarm began to circle around it under the action of gravity. They began to move in elliptical orbits around the nascent object. Some particles fell to the Earth, others collided and stuck together. Then the orbit gradually began to approach more and more circular and from the swarm of particles the embryo of the moon began to form.
Pros and cons
Today, the hypothesis of co-origin has more rebuttal than evidence. She explains the same oxygen-isotopic ratio of two bodies. The reasons for the different composition of the Earth and the Moon put forward as part of the hypothesis, in particular, the almost complete absence of iron and volatile substances on the latter, are doubtful.
Guest from afar
In 1909, the hypothesis of gravitational capture was put forward by Thomas Jackson Jefferson C. According to her, the moon is a body formed somewhere in another area of the solar system. Its elliptical orbit crossed the trajectory of the Earth. At the next approach, the Moon was captured by our planet and became a satellite.
In favor of the hypothesis, scientists cite fairly common myths of the peoples of the world, telling about a time when the moon was not in the sky. Also indirectly, the theory of gravitational capture is confirmed by the presence of a solid surface on the satellite. According to Soviet studies, a moon without an atmosphere, if it has been spinning around our planet for several billion years, should have been covered with a multimeter layer of dust falling from space. However, today it is known that this is not observed on the surface of the satellite.
The hypothesis can explain the small amount of iron on the moon: it could form in the zone of giant planets. However, in this case, it should have a large concentration of volatile substances. In addition, according to the results of simulation of gravitational capture, its possibility seems unlikely. A body with such a mass as that of the Moon would most likely collide with our planet or be expelled from the orbit. Gravity capture could occur only in the case of a very close passage of the future satellite. However, in this embodiment, the destruction of the moon under the influence of tidal forces becomes more likely.
Giant collision
The third of the above hypotheses is today considered the most plausible. According to the theory of a giant collision, the Moon is the result of the interaction of the Earth and a rather large space object. The hypothesis was proposed in 1975 by William Hartman and Donald Davis. They suggested that the young Earth, which managed to gain 90% of its mass, collided with a protoplanet called Theia. Its size corresponded to modern Mars. As a result of the blow that came to the “edge” of the planet, almost all of Tei’s substance and part of the earth’s were thrown into outer space. From this "building material" the moon began to form.
The hypothesis explains the current speed of the Earth's rotation, as well as the angle of inclination of its axis and many physical and chemical parameters of both bodies. The weak point of the theory is its reasons for the low iron content on the moon. For this, before the collision in the bowels of both bodies, a complete differentiation had to occur: the formation of an iron core and silicate mantle. No evidence has been found to date. Perhaps new data on the Earth's satellite will clarify this issue. True, there is a possibility that they may refute the hypothesis of the origin of the moon, accepted today.
main parameters
For modern people, the Moon is an integral part of the night sky. The distance to it today is approximately 384 thousand kilometers. This parameter changes somewhat as the satellite moves (range - from 356,400 to 406,800 km). The reason lies in an elliptical orbit.
The satellite of our planet moves through space at a speed of 1.02 km / s. It completes a complete revolution around our planet in about 27.32 days (sidereal or stellar month). Interestingly, the attraction of the Moon by the Sun is 2.2 times stronger than the Earth. This and other factors affect the movement of the satellite: a decrease in the sidereal month, a change in the distance to the planet.
The axis of the moon has a tilt of 88 ° 28 '. The rotation period is equal to the sidereal month and that is why the satellite is always turned to our planet on one side.
Reflective
It can be assumed that the Moon is a star very close to us (in childhood, such an idea could come to many). However, in reality, it does not have many parameters inherent in such bodies as the Sun or Sirius. So, the moonlight glorified by all romantic poets is just a reflection of the sun. The satellite itself does not emit.
The phase of the moon is a phenomenon associated with the absence of its own light. The visible part of the satellite in the sky is constantly changing, passing through four stages in succession: a new moon, a growing month, a full moon and a waning moon. These are the stages of the synodic month. It is calculated from one new moon to another and lasts an average of 29.5 days. The synodic month is more sidereal, since the Earth also moves around the Sun and the satellite has to make up some distance all the time.
Many faces
The first phase of the moon in the cycle is the time when for the earth observer there is no satellite in the sky. At this time, he is facing our planet with a dark, unlit side. The duration of this phase is one to two days. Then a month appears in the western part of the sky. The moon is just a thin sickle at such a time. Often, however, one can observe the entire satellite disk, but less bright, colored in gray. This phenomenon is called the ash color of the moon. The gray disk next to the bright sickle is the part of the satellite illuminated by the rays reflected from the surface of the Earth.
Seven days after the start of the cycle, the next phase begins - the first quarter. At this time, the moon is lit exactly half. A characteristic feature of the phase is a straight line separating the dark and illuminated area (in astronomy it is called the “terminator”). Gradually, it becomes more convex.
On the 14-15th day of the cycle, the full moon sets in. Then the visible part of the satellite begins to decrease. On the 22nd day comes the last quarter. During this period, ashy color can also often be observed. The angular distance of the Moon from the Sun is becoming less and less and after about 29.5 days it again completely disappears.
Eclipse
A few more phenomena are associated with the features of the satellite’s movement around our planet. The lunar orbital plane is inclined to the ecliptic by an average of 5.14 °. This situation is not typical for such systems. As a rule, the satellite’s orbit lies in the plane of the equator of the planet. The intersection points of the trajectory of the moon of the ecliptic are called ascending and descending nodes. They do not have an exact fixation, they constantly, although slowly, move. In about 18 years, nodes pass through the entire ecliptic. In connection with these features, the Moon returns to one of them after a period of 27.21 days (it is called the dragon month).
With the passage of the satellite at the points of intersection of its axis with the ecliptic, a phenomenon such as an eclipse of the moon is associated. This is a phenomenon that rarely pleases (or upsets) us, but has a certain periodicity. An eclipse occurs at the moment when the full moon coincides with the passage of the satellite of one of the nodes. Such an interesting “set of circumstances” arises quite rarely. The same is true for the coincidence of the new moon and the passage of one of the nodes. At this time, a solar eclipse occurs.
Observations of astronomers have shown that both phenomena are cyclical in nature. The length of one period is slightly more than 18 years. Such a cycle is called saros. During one period, 28 lunar and 43 solar eclipses occur (13 of them total).
The influence of the night luminary
Since ancient times, the moon was considered one of the rulers of human destiny. According to thinkers of that period, it influenced character, attitudes, mood and behavior. Today, the effect of the moon on the body is studied scientifically. Various studies confirm that the dependence of certain behavioral and health features on the phases of the night luminary exists.
For example, Swiss doctors, who have been monitoring patients with problems with the cardiovascular system for a long time, have found that the growing moon is a dangerous period for people with a heart attack. Most of the attacks according to their data coincided with the appearance of a young month in the night sky.
There are a large number of similar studies. However, the collection of such statistics is not the only thing that interests scientists. They tried to find explanations for the revealed patterns. According to one theory, the Moon has the same effect on human cells as it does on the entire Earth: it causes ebbs and flows. As a result of the influence of the satellite, the water-salt balance, membrane permeability, and the ratio of hormones change.
Another version focuses on the influence of the moon on the magnetic field of the planet. According to this hypothesis, a satellite causes changes in the electromagnetic impulses of the body, which entails certain consequences.
Experts who hold the opinion of the enormous influence of the night luminosity on us recommend building their activities in accordance with the cycle. They warn: lanterns and lamps that block the moonlight can harm human health, because because of them the body does not receive information about the phase change.
On the moon
After acquaintance with the night luminary from Earth, we will walk along its surface. The moon is a satellite, not protected from exposure to sunlight by the atmosphere. During the day, the surface heats up to 110 º, and at night it cools down to -120 º. Moreover, temperature fluctuations are characteristic of a small zone of the crust of a cosmic body. Very low thermal conductivity does not allow the satellite to warm up.
We can say that the Moon is land and sea, vast and little explored, but with their own names. The first satellite surface maps appeared in the seventeenth century. Dark spots previously mistaken for the seas, after the invention of the telescope, turned out to be low plains, but retained their name. The lighter areas on the surface are “continental” zones with mountains and ridges, often ring-shaped (craters). On the Moon you can meet the Caucasus and the Alps, the Sea of Crisis and Tranquility, the Ocean of Storms, the Bay of Joy and the Swamp of Rot (satellite bays - dark areas adjacent to the seas, swamps - small irregular spots), as well as the mountains of Copernicus and Kepler.
And only after the beginning of the space age , the reverse side of the moon was explored. It happened in 1959. The data obtained by the Soviet satellite made it possible to map a part of the night luminary hidden from telescopes. The names of the greats also sounded here: K.E. Tsiolkovsky, S.P. Koroleva, Yu.A. Gagarin.
Quite another
The lack of atmosphere makes the moon so different from our planet. The clouds here are never covered by clouds; its color does not change. On the moon above the head of the astronauts there is only a dark starry dome. The sun rises slowly and slowly moves through the sky. A day on the moon lasts almost 15 earth days, such is the duration of the night. A day is equal to the period during which the Earth’s satellite makes one revolution relative to the Sun, or the synodic month.
There is no wind and precipitation on the satellite of our planet, and there is no smooth flow of day to night (twilight). In addition, the moon is constantly threatened by meteorites. The regolith covering the surface indirectly indicates their quantity. This is a layer of debris and dust up to several tens of meters thick. It consists of fragmented, mixed and sometimes fused remains of meteorites and lunar rocks destroyed by them.
When looking at the sky, you can see the Earth hanging and still in the same place, always hanging. A beautiful, but almost never changing picture is explained by the synchronization of the rotation of the moon around our planet and its own axis. This is one of the most wonderful spectacles that the astronauts who first landed on the surface of the Earth’s satellite had a chance to see.
Famous
There are times when the Moon is the “star” of not only scientific conferences and publications, but also all kinds of media. Of great interest to a large number of people are some rather rare phenomena associated with the satellite. One of them is super moon. It occurs on those days when the night star is at the smallest distance from the planet, and in the phase of the full moon or new moon. At the same time, the night star becomes visually 14% larger and 30% brighter. In the second half of 2015, the super moon can be observed on August 29, September 28 (on this day the super moon will be the most impressive) and October 27.
Another curious phenomenon is associated with the periodic hit of the night luminary in the earth's shadow. The satellite does not disappear from the sky, but acquires a red color. The astronomical event was called the Blood Moon. This phenomenon is quite rare, but modern space lovers are again lucky. Blood moons will rise above the Earth in 2015 several times. The last of them will appear in September and will coincide with a complete eclipse of the night luminary. This is definitely worth seeing!
The night luminary has always attracted people. A month and a full moon are central images in many poetic essays. As the scientific knowledge and methods of astronomy developed, the satellite of our planet became interested not only in astrologers and romantics. Many facts from the time of the first attempts to explain the lunar "behavior" became clear, a large number of secrets of the satellite were revealed. However, the night luminary, like all objects of space, is not as simple as it might seem.
Even the American expedition could not answer all the questions posed to it. At the same time, every day, scientists learn something new about the Moon, although often the data obtained raise even more doubts about existing theories. So it was with the hypotheses of the origin of the moon. All three main concepts, which were recognized in the 60-70s, were refuted by the results of the American expedition. Soon the hypothesis of a giant collision became the leading one. Most likely, in the future we will find many amazing discoveries related to the night luminary.