Jean Richer knew that the length of the pendulum had not changed. Nor had the clock been damaged in shipment. Therefore, the difference in period must have been related to a change in the gravitational attraction of the Earth. Richer concluded that the force of gravity was weaker in French Guiana, near the equator, than in Paris, nearly 5,900 kilometers north of the equator.
Later Isaac Newton suggested a reason for the weaker gravitational attraction at the equator. He said that the Earth bulges at the equator. Newton reasoned that near the equator the rotational speed of 1,600 kilometer per hour particularly overcomes the pull of gravity at the center of the Earth. This force pulling matter away from the center of the Earth is called centrifugal force. Consequently, matter tends to bulge outward around the equator.
In Newton’s law of gravitation, gravitational attraction between two objects becomes less as the distance between the two objects becomes greater. This is another reason that the gravitational attraction for bodies on the Earth’s surface is least at the equator and greatest at the poles.
- Why are astronauts weightless in the space? Is it because they are beyond the pull of gravity?
- Why does a candle flame defy gravity and burn upward? What will happen on lighting a candle in space?
- Why aren’t people at the equator thrown off into space by centrifugal force since the Earth is rotating at a high speed?