EARTH AS A PLANET
It is the only planet which supports life. From space, the earth looks blue because 70
per cent of its of its total area is covered by water. Hence, it is also called the watery
planet.) The family of the sun is called the Solar System. The members of the solar
system are placed at a certain distance from the sun. The chief members of the solar
system are the planets, the satellites that revolve around the planets and other celestial
bodies called asteroids, comets and meteorites. The planets in order of their distance
from the sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
THE SHAPE OF THE EARTH
The earth is not a perfect sphere. It bulges slightly at the centre and is flattened at the
poles. In the olden days, the earth was considered to be a flat disc with steep edges.
Aryabhatta, the 5th century Indian astronomer and mathematician, believed in the
round shape of the earth. He said that the earth was spherical in shape and rotated on
its axis. In the 6th century, Greek philosopher Pythagoras said the same thing.
Proof that the Earth is Spherical in shape:-
The following are the reasons which prove that the earth is spherical in shape:
(i) Sighting of a ship: While standing at seashore, watching an approaching ship, we
first of all see only its mast. Then, as it comes closer, we can see the deck in the
middle, then its funnel, and finally the hull comes into full view. This can happen only
when the earth's surface is curved. If the earth were flat, the entire ship would have
been seen all at once.
(ii) The Bedford Level Experiment: Almost on similar lines, as described above, an
experiment was carried out in the Bedford Level canal area in England. Three poles of
equal length were fixed at intervals of 5 km. It was ensured that the poles had the same
height above the water in the canal. When the poles were viewed from one end of the
canal, the middle pole looked slightly higher.
(iii) Pole-Star: The Pole star can be seen at an angle of 90° at the North Pole. It lies in
line with the axis of the earth, and its angle decreases towards the Equator. At the
Equator, the angle is 0°. This can happen only in an arc of a circle. If the earth were flat,
the Pole Star would have the same height for all latitudes.
(iv) Satellite Pictures: Jean Baptiste Delambre (1749-1822), the French astronomer,
discovered the flattening of the earth at the poles. In the 20th century, when satellite
pictures of earth were fed into computers, its spherical shape with the flattened poles
was confirmed.
It is the only planet which supports life. From space, the earth looks blue because 70
per cent of its of its total area is covered by water. Hence, it is also called the watery
planet.) The family of the sun is called the Solar System. The members of the solar
system are placed at a certain distance from the sun. The chief members of the solar
system are the planets, the satellites that revolve around the planets and other celestial
bodies called asteroids, comets and meteorites. The planets in order of their distance
from the sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
THE SHAPE OF THE EARTH
The earth is not a perfect sphere. It bulges slightly at the centre and is flattened at the
poles. In the olden days, the earth was considered to be a flat disc with steep edges.
Aryabhatta, the 5th century Indian astronomer and mathematician, believed in the
round shape of the earth. He said that the earth was spherical in shape and rotated on
its axis. In the 6th century, Greek philosopher Pythagoras said the same thing.
Proof that the Earth is Spherical in shape:-
The following are the reasons which prove that the earth is spherical in shape:
(i) Sighting of a ship: While standing at seashore, watching an approaching ship, we
first of all see only its mast. Then, as it comes closer, we can see the deck in the
middle, then its funnel, and finally the hull comes into full view. This can happen only
when the earth's surface is curved. If the earth were flat, the entire ship would have
been seen all at once.
(ii) The Bedford Level Experiment: Almost on similar lines, as described above, an
experiment was carried out in the Bedford Level canal area in England. Three poles of
equal length were fixed at intervals of 5 km. It was ensured that the poles had the same
height above the water in the canal. When the poles were viewed from one end of the
canal, the middle pole looked slightly higher.
(iii) Pole-Star: The Pole star can be seen at an angle of 90° at the North Pole. It lies in
line with the axis of the earth, and its angle decreases towards the Equator. At the
Equator, the angle is 0°. This can happen only in an arc of a circle. If the earth were flat,
the Pole Star would have the same height for all latitudes.
(iv) Satellite Pictures: Jean Baptiste Delambre (1749-1822), the French astronomer,
discovered the flattening of the earth at the poles. In the 20th century, when satellite
pictures of earth were fed into computers, its spherical shape with the flattened poles
was confirmed.
