The Bible says that this beautiful Earth on which we live was created by God for Adam and Eve to live in and those we are the descendants of Adam and Eve. For centuries many philosophers in the East and in the West including the Greek philosopher Aristotle believed that earth is the centre of this universe.
It was left to Galileo, a prominent mathematician of Padua University to announce his discovery on January 17, 1610 that the Earth is a planet just like other planets revolving round the Sun, which is a star. It was also established that the sun due to its gravitational pull attracts all these planets which revolve round it.
Apart from the Earth there are some other planets which go round the sun. These planets, however, vary in size and also in their distance from the sun. They have their own orbits, and the period of rotation also varies in each case. Some of these planets have satellites called moons, varying in number. Some do not have any satellites. Normally, if they do not have a counter pull, they should have been dragged into the sun by the gravitational pull. These gravitation pulls of the sun and the counter pulls of the planets are called centrifugal forces. The planets revolve round the sun in their own specific orbits.
These planets could be arranged in an order based on their distance from the sun. The nearest to the sun is Mercury and the next is Venus. Third comes the Earth. Later in the same order come Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Pluto is the most distant planet.
If the are arranged in the order of size, the order would be ;
1. Jupiter, 2. Saturn, 3. Neptune, 4.Uranus, 5. Earth, 6. Venus, 7. Mars, 8. Pluto and 9. Mercury. The solar system has a diameter of 17,900 million kms. The nine planets can be grouped into two groups: 1. Small but high density planets – Mercury, Venus, Earth and Mars and 2. big but low density planets – Jupiter, Saturn, Uranus, Neptune and Pluto.
Some of these planets have sub-planets or satellites called moons. Mercury and Venus have no moons. They are also very hot as they are very near the sun. The Earth has one moon, and Jupiter has as many as twelve. The number of moons varies in each case.
The Earth is at a distance of 149 million kms. Away from the sun and Pluto is at a distance of 5793 million kms. away. In the solar system the sun is the biggest and accounts for 99.86% of the matter in the system. The sun is a massive burning star. Its surface temperature is 60000C. Mercury which is the nearest planet to the sun is 4900 km away from it.
The Earth revolves on it sown axis and also goes around the sun in an elliptic orbit, which is 941.4 million kms. The Earth takes 365-1/4 days to go round the sun once. Earth takes 24 hours to turn found once on its axis. The polar diameter of the earth is 12713 kms and the diameter at the equator is 12756 kms. The atmosphere consists of 20% oxygen and about 80 nitrogen. The moon which is a satellite to Earth is about 3,85,000 kms. away from the Earth and takes roughly 15 days to go round the Earth once.
Except the Earth, no other planet can contain life on account of extreme temperature conditions. This beautiful planet the Earth has a major part covered by seas and oceans. Compared to the area covered by water, the land mass is less.
Compared with the universe which has many suns like ours, the earth on which we live is a tiny speck. In this tiny space there are many continents. Billion of people live on earth. Earth is a part of the great universe.