Our Smartmedia series is intended to make kids smarter by explaining the world. If you want to learn all the basic knowledge, this series is perfect for you.
In this episode we discuss the history of our planet.
The Earth was formed about 4.6 billion years ago from gas and dust. It was so hot that it became a ball of liquid rock. As time went by, its surface cooled and formed a hard crust.
Scientists think that over millions of years the shape of the land and climate changed. Some animals died out and others appeared which could survive in the new but always changing conditions.
The hot Earth was covered with thick clouds of steam and gas. As the temperature cooled, it began to rain. It rained for hundreds of years and the seas formed. For the first billion years, there was no life on Earth. During this stormy time, mountains were formed and worn away. The land was covered by the sea and then left dry again.
The first living things on Earth were too tiny to be seen, and lived in the seas. Later, sea plants formed. They gave out oxygen, which the first sea animals needed to breathe. Fish were the first animals with a backbone and a kind of skeleton inside their bodies.
As more land appeared out of the seas, living things spread onto the wetlands. Many plants grew there and animals could now feed on land. Over a long period of time, some types of fish developed lungs. They could breathe out of water, and drag themselves along with their strong fins. These animals, amphibians, could live both on land and in water. Along with many insects, they lived in the warm, steamy swamps covering the Earth.
The climate on Earth grew hotter, and the swamps dried up. Amphibians needed water to lay eggs, so many died out. Animals, called reptiles, developed. They laid eggs on land, and were able to live in the new conditions. Monster reptiles, the dinosaurs, roamed the Earth. Some of them were 30 times bigger than an elephant. Many of them ate plants. Some, called pterosaurs, could fly. Dinosaurs died out about 60 million years ago. Cold-blooded animals are called ectotherms. Warm-blooded animals are called endotherms. Dinosaurs are believed to be in between: mesotherms. They could achieve the benefits of stable, warm body temperatures without having to eat so much. Nowadays animals are either ectotherm (reptiles and most fish) or ectotherm (mammals).
Scientists do not know exactly why all dinosaurs died out, but 150 million years before they did, the first mammals appeared on Earth. We mostly believe now that about 66 million years ago there was worldwide environmental change resulting from the impact of a large celestial object with the Earth and/or from vast volcanic eruptions. These climate and geological changes interrupted the dinosaurs’ food supply. Mammals feed their babies on milk that their mothers produce.They were better protected against the climate change. It was about now that the first flowering plants grew.
The climate grew cold and the Ice Ages began. Only mammals with fur, such as mammoths which lived in the last Ice Age, could survive on the land. About 150.000 years ago, in the last Ice Age, an early type of human lived in caves. They made stone tools and knew how to light fires. Scientists think that in about 5 billion years from now the Earth will end to exist. By then the Sun may have grown to 100 times its size and could burn up our planet.
That was all about our planet!