More than 4.5 billion years ago, this rocky planet was originally just dust floating in space, which originated from the big explosion of a huge ancient star at the end of its life.
From its formation to the present, the earth can also be divided into five generations: Archean, Proterozoic, Paleozoic, Mesozoic and Cenozoic. Some generations are further divided into several "times". For example, Paleozoic is divided into Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian from far to near; Mesozoic is divided into Triassic, Jurassic and Cretaceous; Cenozoic is divided into tertiary and quaternary. This is the roughest division of the earth's historical period, which we call "geological age". People in different geological ages have different characteristics.
Archaean, 2.4 billion years ago, primitive lithosphere, hydrosphere and atmosphere were formed on the earth's surface. But at that time, the crust was unstable, volcanic activity was frequent, magma was everywhere, the ocean was vast, and the land was covered with bare mountains. This is an important era of iron ore formation, and the lowest primitive life began to appear.
Proterozoic 2.4-600 million years ago. At this time, most of the earth is still covered by oceans. Later, a large area of land appeared on the earth. "Proterozoic" refers to the primitive era, when algae and marine invertebrates appeared.
600-250 million years ago was Paleozoic. "Paleozoic" refers to the era of ancient life. At this time, thousands of animals appeared in the ocean, and marine invertebrates flourished unprecedentedly. Later, fish-like animals appeared, and fish multiplied in large numbers. A fish crawling on its fins appeared and landed on land, becoming the ancestor of terrestrial vertebrates. Amphibians also appeared. Ferns appear on the land in the northern hemisphere, some of which are as high as 30 meters.
Mesozoic, from 250 million years ago to 700 million years ago, lasted about 65.438+0.8 billion years. This is the era of reptiles, dinosaurs once dominated, and primitive mammals and birds appeared. Pteridophytes are declining and being replaced by gymnosperms. The lush plants and huge animals in the Mesozoic era later turned into many huge coalfields and oil fields. Many metal deposits were also formed in Mesozoic.
Cenozoic is the latest stage in the history of the earth, with the shortest time, only about 70 million years. At this time, the appearance of the earth is basically the same as today. The new generation angiosperms developed greatly, and all kinds of herbivorous and carnivorous mammals flourished unprecedentedly. The great development of natural life eventually led to the emergence of human beings, and the ancient apes gradually evolved into modern people. It is generally believed that human beings appeared in the Quaternary, about 2.4 million years ago.
The earth where human beings live has evolved step by step to the present and gradually formed today's face.
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Why is the earth round?
The earth is round, so are other planets. The water droplets we see in the air are round, and so are the bubbles.
Due to the surface tension of liquid, bubbles and water droplets are round.
Why the earth is round, we should start with the birth of the earth. The original universe was a high temperature, high energy and high density substance. Because of the big bang, all kinds of planets were produced. At that moment, all the planets were liquid at high temperature, and they were round because of surface tension. After hundreds of billions of years of cooling, the surface temperature of some planets gradually decreased, and then the protein gradually came into being, resulting in life. This planet is the earth. Nothing makes it the other in various sports in the future.
How to prove that the earth is round?
Magellan's voyage around the world is a great achievement in the history of world navigation, which was realized by the expedition fleet led by Portuguese explorer Magellan in September 15 19- 1522. Magellan's successful voyage around the world not only opened up new routes, but also proved that the earth is round through his expedition fleet.
How big is the earth?
The earth, the planet where human beings live, is one of the eight planets in the solar system. Its average distance from the sun is 149597870 km (1 astronomical unit), ranking third among the planets. Its equatorial radius is 6378.2 kilometers, ranking fifth among the planets in size.
The equatorial radius of the earth is (a) 6378+040 km.
The radius of the earth's pole is (b) 6356.755km.
The average radius of the earth is r (3a2b) 6371.004km..
Equatorial circumference (2лa)40075 km
The earth's area is (4лR2)5 10 100934 square kilometers.
The volume of the earth is 4 π R311082 billion cubic kilometers =1.083207 3x1kloc-0/2km3.
Soil quality: 5.9742×10.24 kg.
Average density: 55 15.3kg/m3.
Equatorial surface gravity acceleration: 9.780 1 m/s 2 (0.997 32g).
The temperature of the earth
The core temperature is about 6880℃, which is higher than the surface temperature of the solar photosphere (6000℃). The highest temperature on earth occurs when a hydrogen bomb explodes. One explosion can reach 10000000℃, which is 16667 times of the surface temperature of the sun and 1400℃ higher than the core temperature of the sun. The "cold pole" in the northern hemisphere is located in Oymyakan in eastern Siberia, and the lowest temperature in 10 is–71961℃. The "cold pole" in the southern hemisphere is located in the Antarctic continent. The temperature on August 24th, 1960 was–88.3℃.
Earth's electricity
negative charge
Reason: The earth rotates from west to east, and the outer side of the geomagnetic field points from the magnetic south pole to the magnetic north pole (that is, the north pole points to the south pole). The annular current formed is opposite to the rotation direction of the earth, so it is negatively charged.