What is The earth shape and size ?

• Shape of the earth.

Pythagoras (572-500 B.C.), a Greek philosopher and mathematician, was among the first to suggest that the earth was shaped like a globe.

• The earth is not flat.

If the earth were a flat disc, then the rising sun would have been seen at all places at the same time. But this does not happen. Places in the east see the rising sun earlier.

When a ship approaches land its funnel or mast is seen first and then the hull. If the earth had been flat, the whole ship would have been seen at the same time.

• The earth is a sphere.

The earth is rarely oriented in the same position during successive eclipses but it always casts a circular shadow thus proving that the earth is a sphere. A sphere is the only solid body that will always cast a circular shadow.

At the north pole the pole star can always be observed at 90 degree in the sky, since the star lies in the line with the axis of the earth.

As one travels southwards, the angle of pole star decreases.

At the equator the angle becomes zero degree.

This observation proves that the path of travel is an arc of a circle.

The sun, moon and all the heavenly bodies appears to be spherical when viewed from different positions. It seems logical to conclude that the earth is no exception.

The photographs of the earth taken from the space prove beyond any doubt that the earth is a sphere.

The earth as an oblate spheroid.

Refined measurements of the earth have proved that the true form of the earth resembles a sphere that has been compressed at the poles and made to bulge at the equator. This form is known as an oblate spheroid.

• What are the various factors which make the earth suitable for life to evolve and survive ?

The earth has all the essential elements like carbon (in the form of co2), hydrogen (h2), nitrogen (n2) and oxygen (o2) which as building blocks for the origin of life.

The earth is neither too hot nor too cold. It has the right temperature range for carrying out the life-sustaining chemical reactions.

The earth has a lot of water in the form of lakes, rivers and ocean for the growth and survival of life.

The earth has enough oxygen gas in its atmosphere for the survival of living beings through breathing.

The earth has a protective blanket of ozone layer high up in its atmosphere to save life from harmful ultraviolet radiations coming from the sun.

The earth is the fifth largest planet in the solar system.

29.2 % of the total surface area of earth is covered by continents (land), while 70.8 % is covered by oceans (water).

The total water area of the earth including the oceans, lakes, rivers, ice sheets and the water in the atmosphere is called hydrosphere and it covers about 71 % of the earth’s surface.