After secretly orbiting the earth for three years, "Earth moon" was finally discovered. What is its ending?

After secretly orbiting the earth for three years, the moon "Earth" was finally discovered. What is its ending? It can be said with certainty that the earth currently does not have a second natural satellite. We don’t know how many satellites have orbited the Earth in the past 4.6 billion years, but as of now, the only natural satellite that is still orbiting the Earth is the moon. Although we can often see the moon when we look up, not many people actually know about this planet. For example, why does the moon show different phases at different times, why does the moon always face us with the same side, or why does the moon gradually move away from our earth, etc.

About the Moon

It is undeniable that, unlike other celestial bodies in the solar system, the moon should be the satellite that people on earth pay most attention to. Although it is not as dazzling as the sun during the day, nor is it like the stars in the sky at night that always seem to blink at us. Whether it is ancient myths or poems and songs that have been immortalized for generations, there are many contents closely related to the moon, which also proves that the moon has occupied a different position in human hearts from ancient times to the present.

As early as decades ago, humans have set foot on the moon many times. We not only brought back lunar dust from there, but also learned that the "lunar sea" we once thought was just some low-lying plains. ; Through the placement of seismometers, we learned that "earthquakes" often occur on the moon, and thus gained a clear understanding of the moon's internal structure.

So, which came first in the universe, the earth or the moon? Why does the earth look like a sphere from any angle, but the moon we see with our eyes takes on various shapes at different times? This seemingly complex series of issues actually revolves around the core information about the birth and evolution of the moon and the earth. Of course, it also involves the sun, the central celestial body of the solar system.

About age - the earth? came first? the moon? came last?

The moon and the earth are both in the solar system. They will be affected by the gravity of the sun, and among the three The interaction has continued since its birth. Up to now, the nebula hypothesis is a generally accepted view in the speculative theory of the formation of the solar system. Whether stars, planets, or satellites, they all began with the collapse process of giant molecular clouds about 4.6 billion years ago.

As for the birth time of the Earth, we generally define it as about 4.6 billion years ago, and its age is estimated to be between 4.0 and 4.6 billion years old. The formation time of the moon is relatively less certain than that of the earth (about 4.5 billion years ago), but scientists believe that the formation time of the moon is later than the formation time of the earth. If the birth time of the two planets is described by first come first, then the earth will appear in the solar system earlier than the moon.

The formation of the moon - from the split theory to the big collision theory

There are four theories about the formation process of the moon. Their differences are: split theory, capture theory and The theory of homology is the main view held by scientists in the past, while the theory of giant collision is based on several previous views and the results of new research.

Schism theory:

Although many people know Darwin's theory of evolution, most people know very little about his son. Don't be surprised, the split theory of the birth of the moon was actually proposed by George Darwin in 1989. Simply put, this hypothesis holds that the moon was originally part of the earth. The reason why it could fly away from the earth and become an independent satellite later was just because the earth was rotating too fast at that time.

The Pacific Ocean is regarded as a large crater, which becomes evidence of the hypothesis that the earth lost the moon's material. However, this first proposed hypothesis was opposed by many people, because it is difficult to explain how fast the earth must be to throw such a large amount of material from the moon out of the planet. Moreover, judging from subsequent detection data, the material composition of the moon is also very different from that of the earth. If they were one body, theoretically they should have extremely similar material compositions.

Homology theory:

The general idea of ??this hypothesis is actually to express that both the moon and the earth were born from the nebula material diffused in the solar system. Moreover, the birth time and process of these celestial bodies in the solar system are all synchronized. Everyone has to accrete and rotate in this area, but the types and sizes of the celestial bodies formed in this process are different.

Although, the homology theory believes that the earth is older than the moon because the accretion efficiency of the earth was higher during the formation process. However, this claim has been questioned since the Apollo spacecraft brought back rock samples from the moon. Because the test results of lunar rock samples are not what everyone thinks. The chemical composition of the rocks on the moon and the earth is very different, and the age of these rocks is even older than the rocks on the earth.

What is the Big Collision?

In the big collision hypothesis, the Earth was not formed in one go. Instead, the primitive Earth was first formed through the collision and accretion of planetesimals. During the later stages of evolution, the primitive Earth gradually developed the internal structures (metallic core, shell and mantle) possessed by terrestrial planets (silicate).

However, since the distance between the original Earth and the other planet was not far away, and there was a mass disparity between the two, when the two planets collided, their orbits changed.

For example, the Earth's axis of rotation began to tilt, and the dust and gas flying away from the Earth during the impact did not completely escape the influence of the gravitational pull caused by the Earth's mass. They combined again through accretion and eventually formed an almost molten moon. This hypothesis gained more acceptance because it explained the density differences, composition differences, and age differences between the moon and the Earth.

Why does the moon have various shapes in your eyes?

As we all know, the moon and the earth both have a spherical appearance, but the earth's surface is relatively smooth, while the moon's surface is bumpy. But this does not prevent many people from understanding why the moon that everyone sees at night often has different shapes. This is why people have joys and sorrows, and the moon waxes and wanes. However, the moon has never been missing any part, it is just a matter of the changing phases of the moon.

To put it simply, the reason why the moon in our eyes is rarely round is essentially caused by the position changes between the three celestial bodies of the earth, moon and sun. Since the moon is a satellite and cannot emit heat itself, the moonlight we usually see is actually the sun illuminating the moon. The so-called moon phase is actually the part of the moon that reflects sunlight when it is illuminated by the sun.

I believe everyone knows that these celestial bodies in the universe are not stationary and have their own established orbits. The reason why we cannot see the full moon often is not because the sunlight is blocked by the earth ( This is a lunar eclipse in astronomy), but because the sun only illuminates that part of the moon, the remaining non-luminous part is the shadow of the moon. In short, the size of the area where the moon reflects sunlight is mainly related to the relative position between the moon and the sun (the ecliptic longitude difference).

In fact, in addition to bringing us different visual experiences, the moon phases are also closely related to our lives. For example, the lunar calendar in the calendar actually arranges the calendar based on the cycles of the moon phases. One month is when the moon completes one revolution around the earth; and the tides of the earth's hydrosphere are also related to the moon phases. We will find that whenever the moon phase is During a full moon, the ocean usually experiences high tides caused by the moon's gravity. Moreover, due to the dimensional difference of the earth, people living in the northern and southern hemispheres will see completely opposite phases of the moon.