earth

EARTH The Earth, man's home, is a planet. The Earth has special characteristics, and these are important to man. It is the only planet known to have the right temperature and the right atmosphere to support the kind of environments and natural resources in which plants and man and other animals can survive. This fact is so important to man that he has developed a special science called ecology, which deals with the dependence of …

…history, these changes have been small compared to the changes that created mountains or the vast expense of the prairie. But the recorded history of man covers only a short period of the Earth's history. Scientists believe that the Earth has existed for about 4.5 billion years. Man's recorded history extends back only about 6 000 years, or 0.0000013 percent of the Earth's age. There is ample evidence that the Earth's surface has changed greatly since its original formation.