WHY THE SATELLITES ARE NOT FALLING DOWN ON US?

A fast running bi-cycle hit by an object may not fall down. It gets stabilized due to gyroscopic effect. A boat or ship tilted by the strong wind will not turn turtle because it is so designed to stabilize itself. A space station orbiting around the earth may get hit by a rock. It may slow down. But it will not plummet to the earth. It automatically get stabilized. Let see how.

A satellite is taken by the rocket and pushed into the orbit. The satellite is given a preciously calculated velocity called 'orbital velocity'. If the velocity is slightly less than the orbital velocity, it will fall down on the earth pulled by gravity. If the velocity is more, it will fly away from the earth or earth's gravity.

Any orbiting or rotating body have what is called "angular momentum'. given by the formula
Angular momentum = mass * velocity* radius of orbit
This quantity is always remain constant and conserved. As the radius increases, the velocity has to increase to keep the momentum constant. Consider a spinning dancer. As the dancer brings the stretched arms close to her body, she spins even faster.(The distance decreases, speed increases).

If the space station or satellite is hit by a rock accidentally, its speed will decrease, and it will start falling down. But immediately, the principle of conservation of angular momentum comes into play. That is, the space station's speed will get increased as the distance decreases. The station will get back the required speed and will stay in the orbit. Hence "angular momentum" plays the main role in orbital stability.

The earth goes around the sun in slightly elliptical orbit. When the earth is close to the sun, it moves fast. When it farther from the sun, it slightly slows down. All because of angular momentum principle.
It seems that, nature has given laws to stabilize our vehicles. And the nature's intent is not to destabilize our life.

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