Earth

                               Earth

The Earth is the only planet known to have existence of life in it. It is the third planet from the Sun and the largest rocky planet Mainly the Earth has four layers- The inner core, the outer core, the mantle and the crust. The inner core contains iron and nickel and has a temperature of 4,000°C The iron and nickel are molten in the outer core. The third layer is the mantle which consists mostly of solid silicate material of iron and magnesium. The outermost layer is the crust of silicate rock called the lithosphere. The crust contains large quantity of different kinds of elements. Earth's atmosphere contains a mixture of many gases like nitrogen, oxygen, carbon dioxide, helium, ozone etc. The atmosphere helps to filter out most of the deadly rays from the Sun, traps enough warmth to prevent extreme cold and stops meteorites from entering Earth's surface. The Earth takes 23.56 hours to rotate once on its axis. It takes 365.26 days to complete one revolution. The only satellite of Earth is the Moon which is as big as the Earth.

                      Day and Night

The Earth rotates on its axis while orbiting around the Sun. When it rotates, one side faces the Sun and the other side is away from the Sun. The side towards the Sun gets direct sunlight and it is the day. The other side is darkened due to the lack of sunlight and it is the night. Gradually the portion getting sunlight moves to darkness and the dark portion moves to sunlight. Thus the rotation of the Earth on its axis causes day and night.

                         Blue Planet

Earth is a hydrosphere. About 70% of the total surface of Earth is covered with water. Earth is the only planet which has water in it in liquid form, and so called a watery planet. The distance between the Earth and the Sun is suitable to keep the water in liquid form. When viewed from space, the Earth seems as a cloudy blue coloured sphere So the Earth is known as blue planet.

                            Seasons

The Earth revolves round the Sun while spinning on its axis. The axis tilts 23.4° from the vertical. Seasons occur due to the tilt and revolution of the Earth. When the northern part of the Earth faces the Sun it has summer. At the same time the southern part is away from the Sun and it has winter. In a period of six months the southern part comes towards the Sun and gets summer, and the northern part that goes far away from the Sun gets winter. Thus the seasons change all through the year.

                             Geold

The shape of the Earth is not exactly like a sphere. It is bulged at the centre and flattened at the poles. The speed of rotation is lower at the poles than at the equator. Because of the

irregularity in shape the Earth is called a geoid by the scientists.

                        The Earth

Distance from the sun in km: 149.6 million Diameter at equator in km: 12,756.32 

Diameter at the poles in km: 12,713.54

Period of revolution: 365.26 days 

Period of rotation: 23 hours and 56 minutes

Temperature: -89.6°C to 58°C

Age: About 4.6 billion years 

Satellites: One (the Moon)