The Earth

Earth is a beautiful planet inhabited by human beings, animals, and plants. When seen from the space, astronauts frequently get the feeling that the Earth is small with a thin, brittle layer of atmosphere. Our planet is known as 'Blue Planet' because it looks blue from above. Earth is the third planet from the Sun at a distance of about one hundred and fifty million kilometers. It takes 365days for the Earth to travel around the Sun. The atmosphere of the Earth is composed of 78 percent nitrogen, 21 percent oxygen, and percent other constituents. Earth's atmosphere protects us from meteors, most of which blaze up before they can hit the shell.

The atmosphere surrounding the Earth protects us by blocking out harmful rays coming from the Sun. The oxygen is necessary for the existence of life because it allows us to breathe. The ozone layer filters out the Sun's harmful rays. The human beings have also disturbed the Earth's atmosphere due to the greenhouse effect caused by gases, like carbon dioxide that is emitted from the industries. This carbon dioxide traps heat from being radiated from the Earth Scientists believe that the atmosphere is unable to balance the greenhouse effect.

Our planet has one natural satellite, the Moon. It is more than one-quarter the size of Earth. Due to its smaller size, the Moon's gravity is one-sixth of the Earth's gravity. Most food chains on Earth begin with plants or some other life forms that get their energy from the Sun through the process of photosynthesis. The animals called herbivores eat the plants and then other carnivore animals eat the herbivores and the food chain continues. Earth is the single planet in the solar system known to have life forms. From our astronomers, we have come to know much on the subject of our home planet. The first American satellite, Explorer 1, discovered a powerful radiation zone, now called the Van Allen radiation belts! Our planet is filled with beautiful flora and fauna. There are beautiful mountains, rivers, lakes, small brooks, hills on its surface. Some of the places are spellbinding. Apart from this, we get many types of gemstones, minerals from the Earth's interior. We live in a beautiful place called Earth.

Scientists do not know how the Earth was formed but several theories have been put forward. The most accepted theory is that the Sun and its planets were formed at the same time from a huge cloud of dust and gases. The Sun was the center of this cloud and all the planets moved around the Sun. As the Earth was in its formation state, heavy iron and nickel settled at its solid core. Above this core formed the outer core made up of hot liquid. The next layer was the mantle and on the top layer was the crust.