Classwork Series and Exercises {Geography – SS 1}: The Earth as a Planet

Content

1. The shape of the Earth
2. The size of the Earth
3. Evidence/ proof of the Earth’s sphericity

The shape of the Earth

The earth is not flat. The earth has a spherical shape and slightly flattened at the poles to give a nearly spherical shape. The earth’s shape is better described as a geiod which means, the earth’s shape.

The size of the Earth

The earth is the fifth largest planet in the solar system. The surface area of the earth is approximately 443 million square kilometres (97million square miles). Other important dimensions of the earth are:

• Equatorial circumference = 40,085km
• Equatorial diameter= 12,762km
• Polar circumference = 39,955km
• Polar diameter = 12, 722km

Evidence/ proof of the earth’s sphericity

There are many ways to prove or show that the earth is spherical. These include:

1. Circumnavigation of the Earth: it is possible to go round the earth by air, land and sea and return to the starting point as carried out by Ferdinard Magellan and his crew 1519 and 1522, if the earth is flat, one would come in contact with an abrupt edge and fall off
2. Sunrise and Sunset: As the earth rotates from west to east, places the in the east experience the sun earlier (sunrise) than places in the west. Also places in the west see the sun later (sunset) than places in the east. The whole earth would experience sunrise and sunset at the same time if the earth is flat
3. The circular horizon: when one views a distance horizon from any point of the earth. The shape is always circular. And as one climbs higher, the circular horizon widens this type of feature is seen only on a spherical body.
4. Ship’s visibility: when a ship, approaching a port viewed, the top of the mast is seen first before the hull and later the rest of the ship’s body. If ship leaves a habour, it disappears gradually, if the earth is flat, the ship from a distant view would appear and disappear at once
5. Planetary bodies: when the sun, moon, stars and other planetary bodies are viewed from any angle, they are all circular in outline. So, the earth cannot be an exception.
6. Driving poles of equal length on the earth: three poles of equal length driven at the same depth in a level ground were found to have the centre pole projected slightly above the poles at either side because of the curvature of the earth. If the earth is flat, all the poles would have the same height.
7. The lunar eclipse: during lunar eclipse, the earth casts a circular shadow on the moon. Only a sphere, like the earth can cast such a circular shadow.
8. Aerial photographs: pictures of the earth taken from high altitudes by rockets clearly sow the curve edge of the earth. This is the most recent proof of the sphericity of the earth.

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