Description:

The third planet from the Sun is our planet Earth. It is the only known object in the universe as far as we know which harbors life. All the other cases where life is supposedly present on another planet are at best good hypothesis or at most figments of imagination.

The diameter of the Earth is 12756 km. It rotates on its axis once in 23 hours 56 minutes 4.1 seconds, with a period of revolution around the Sun of 365.256 days i.e. Earth moves around the Sun at the speed of 29.79 km per second.

There are several dozens of speculations about the formation of the Earth. According to the generally accepted theory, several billions of years ago, the Earth was formed from primitive material called 'Conchites' which were meteoritic in nature. In the beginning, when the Sun was condensing, from a big cloud of gas and dust, small fragments of the cloud started condensing into millimeter sized objects. These started revolving around the large central object which would eventually form our Sun. Their continuous collision in space possibly resulted in the formations of bigger objects. Ultimately, planet sized bodies were formed.

In the primitive stages, the Earth was very hot with lots of gases trapped in between. As time went by, these gases escaped, forming the atmosphere. This happened approximately 4.5 billion years ago, according to this theory. This hot Earth slowly cooled and formed a crust. It has a cool crust which extends from 20 to 50 kms deep. After that a thicker visions mantle and finally the core which is hot and molten, most probably made up of iron-nickel compounds.

There are however other theories and which need not be biased by the above picture which is just one out about 50 exciting theories of the formation of the Earth and the Solar System. The distance between the Earth and the Sun is very unique distance. The Earth is not too far from the Sun so as to be very cold that average temperature go below the freezing point of water, neither it is too close to the Sun for the average temperature to be above the boiling temperature of water. On Earth daytime temperature is maximum 58 degree C and night time below 0 degree C i.e. -88 degree Celcius makes water exist in the liquid form on the Earth. Since oxygen is also there in the atmosphere, temperature being modest in its range of variation and if forming carbon compounds are stable, there conditions subscribe to life - one of their life-forms are human beings- an intelligent form of life. This makes this planet the most beautiful place - anywhere in the Universe. It is believed that the chief constituents of the atmosphere of the Earth about 4 billion years ago where ammonia, methane, carbon dioxide(given in the order of their abundance) to an observer from space the constantly changing weather patterns contrast strongly with the fixed surface features of the continents and the oceans.