The history of the earth is very long. According to the radiocarbon dating results, the solar system was formed about 65.008 billion years ago, while the primitive earth was formed about 65.004 billion years ago. Theoretically, the formation of the sun began with the gravitational collapse of a huge hydrogen molecular cloud 6.5 billion years ago, and most of the collapsed mass was concentrated in the center, forming the sun.

The rest are squashed while rotating, forming protoplanetary disks, and then forming planets, satellites, asteroids, comets, meteoroids and other small celestial bodies in the solar system.

According to the nebula hypothesis, the asteroids that formed the earth originated from a mass with a diameter of one to ten kilometers formed by the accretion and collapse of gas, ice particles and dust. After 1000 to 20 million years of growth, these substances finally formed the original earth. The new earth's surface is an "ocean" composed of magma.

The moon was formed about 4.53 billion years ago, and the research on the origin of the moon has been inconclusive. The most popular is the big collision hypothesis. According to this hypothesis, a celestial body named Teia collides with the Earth, the size of which is about Mars, and its mass is 10% of that of the Earth. The collision triggered a huge explosion, and the explosive material flew into space, forming the moon through accretion, and part of Teia's mass melted into the earth.

During the period from about 46,543.8 billion to 3.8 billion years ago, earth-moon system entered the late stage of the big bombing, and numerous asteroids hit the surface of the moon, which caused great changes on the surface of the moon. It can be inferred that the earth suffered many impacts at that time.

Since Archaean, the surface began to cool and solidify, forming hard rocks, and the gas released by volcanic eruption formed a secondary atmosphere. The initial atmosphere can be composed of water vapor, carbon dioxide and nitrogen. The evaporation of water vapor accelerates the cooling of the surface. After it completely cooled down, the rainstorm lasted for thousands of years, and the rain filled the basin and formed the ocean. Heavy rain not only reduced the water vapor content in the air, but also washed away a lot of carbon dioxide in the atmosphere.

Besides, water and ice on asteroids, protoplanets and comets are also one of the sources of water. The dark sun paradox points out that although the early sunshine intensity was only about 70% now, the greenhouse gases in the atmosphere were enough to keep the liquid water in the ocean from freezing. About 3.5 billion years ago, the earth's magnetic field appeared, which helped to prevent the atmosphere from being stripped by the solar wind. Its outer layer cools and solidifies, and the crust is formed under the action of atmospheric water vapor.

There are two models that can explain the formation of land, one is that land keeps growing, and the other is more likely to form land rapidly in the early history of the earth, and then keep it today. The internal heat is continuously lost, which pushes the plate tectonic movement to form the continent. According to the continental drift hypothesis, after hundreds of millions of years, supercontinent experienced three times of separation and integration.

About 750 million years ago, Rodinia, the first supercontinent to be tested, began to split, then merged into Pangea 600-450 million years ago, and finally split about 65438+800 million years ago. The earth was in the Pleistocene Great Ice Age, which began 2.58 million years ago. The high latitude region experienced several rounds of freezing and thawing, and it circulated once every 400 years to 1 10,000 years. The last time the mainland was frozen was about 10000 years ago.

Future evolution

15 to 4.5 billion years later, the inclination of the earth's axis may change by as much as 90 degrees. It is speculated that the development of complex life on the earth's surface is still very young, and the activity can continue to reach its peak, lasting about 500 to 10 billion years, but if the nitrogen in the atmosphere disappears completely, this time will be extended to 2.3 billion years.

The fate of the earth in the distant future is closely related to the evolution of the sun. With the continuous nuclear fusion of hydrogen in the sun's core to generate helium, the brightness of the sun will continue to increase slowly, 1 100 billion years later, and will increase by as much as 40% after 3.5 billion years. The speed at which the sun releases heat will also continue to increase.

According to the climate model, the earth's surface will eventually be exposed to rising solar radiation, which will have serious consequences. At first, it will only be in the tropics, and then it will reach the polar cap. Over time, the ocean will evaporate and disappear.