Monday, May 27, 2013
Evidence of the Earth's Sphericity
There are many ways to prove that the earth is spherical. The following are some of them. 1. CIRCUMNAVIGATION OF THE EARTH. The first voyage around the world by Ferdinand Magellan and his crew, from 1519 to 1522, proved beyond doubt that the earth is spherical. No traveller going roumd the world by land or sea has eve encountered an abrupt edge, over which he would fall. Modern air routes and ocean navigation are based on the assumption that the earth is round. 2. THE CIRCULAR HORIZON. The distant horizon viewed from the deck of a ship at sea, or from a cliff on land is always and everywhere circular in shape. This circular horizon widens with increasing altitude and could only be seen on a spherical body. 3. SHIP'S VISIBILITY. When a ship appears over the distant horizon, the top of the mast is seen first before the hull. In the same way, when it leaves habour, its disappearance over the curved surface is equally gradual. If the earth were flat, the entire ship would be seen or obscured all at once. 4. SUNRISE AND SUNSET. The sun rises and sets at different times in different places. As the earth rotates from west to east, places in the east see the sun earlier than those in the west. If the earth were flat, the whole world would have sunrise and sunset at the same time. But we know this is not so. 5. THE LUNAR ECLIPSE. The shadow cast by the earth on the moon during a lunar eclipse is always circular. It takes the outline of an arc of a circle. Only a sphere can cast such a circular shadow. 6. PLANETARY BODIES ARE SPHERICAL. All observations from telescopes reveal that the planetary bodies, the sun, moon, satellites and stars have circular outlines from whichever angle you see them. They are strictly spheres. Earth, by analogy, cannot be the only exception. 7. DRIVING POLES ON LEVEL GROUND ON A CURVED EARTH. Engineers when driving poles of equal length at regular intervals on the ground have found they do not give a perfect horizontal level. The centre pole normally projects slightly above the poles at either end because of the curvature of the earth. Surveyors and field engineers therefore have to make certain corrections for this inevitable curvature, i.e. 12.6 cm to 1 km. 8. SPACE PHOTOGRAPHS. Pictures taken from high altitudes by rockets and satellites show clearly the curved edge of the earth. This is perhaps the most convincing and the most up-to-date proof of the earth's sphericity.