First of all, the cosmic environment of the earth.

The cosmic environment in which the earth is located refers to the cosmic environment centered on the earth, which can be understood from both macro and micro levels. Macroscopically, it refers to the position of the earth in the celestial system, that is, the earth-moon system-solar system-galaxy-total galaxy; Microscopically, it refers to the position of the earth in the solar system. In the infinite space, the earth is just a drop in the ocean, in an endless movement.

Second, the characteristics of the earth

1, its own composition characteristics

(1) Internal structure: The internal structure of the earth can be divided into three layers: crust, mantle and core. Under the action of the earth's gravity, a large number of gases gather around the earth to form a blanket, which is the earth's atmosphere.

(2) Period of motion: The earth is like a gyro, rotating from west to east along its axis of rotation. Her rotation period is 23 hours, 56 minutes and 4 seconds, which is about 24 hours. At the same time, the earth revolves around the sun, and its orbit is elliptical, with a half-length of 149597870 km. One revolution takes 365.25 days, which is one year.

2. Universality and particularity

The earth is an ordinary and special planet in the solar system. Among the nine planets in the solar system, the earth is only an ordinary member in mass, volume and motion, but the existence of life, especially advanced intelligent life, makes the earth a special member of the solar system.

(1) universality

One of the nine planets in the solar system. The earth does not occupy a prominent position in the solar system, but because human beings have settled down on the earth, they have to seek a deeper understanding of it. It is a planet earth. According to the order from near to far from the sun, the earth is the third planet, and its average distance from the sun is 654.38+49.6 million kilometers, which is called an astronomical unit. Among the eight planets in the solar system, the mass, volume, average density and revolution rotation of the earth are nothing special compared with other planets, especially with terrestrial planets. According to the distance between the eight planets and the sun, the earth is in the third place; Compared with mass and volume, the earth ranks fifth. The rotation and revolution speed of the earth is neither the fastest nor the slowest among the eight planets, and the average density is similar to that of other terrestrial planets. So, from these aspects, the earth is really an ordinary planet.

(2) Particularity

Self-condition: The earth is just an ordinary planet. But because the earth is the only planet with hydrosphere and biosphere in the solar system, its atmosphere is also unique. It has the basic conditions for life: sufficient moisture, suitable atmospheric thickness and composition, suitable solar illumination and temperature range. , and produced the only known advanced intelligent life on earth-human beings. In this sense, the earth is a special planet in the universe.

External environment: The cosmic environment in which the earth is located has the following two advantages: (1) The sun has not changed significantly in the past five billion years, and will remain in this state for five billion years, which makes the earth have stable lighting conditions and the evolution of life from low to high has not been interrupted. (2) The planets and most asteroids in the solar system orbit around the sun in an approximate circular orbit, which are not only in the same direction, but also on the same plane, each of which goes its own way and does not interfere with each other, so that the earth is in a relatively safe cosmic environment.

Third, the earth is our home for human survival.

It's beautiful. We should love and protect her.