How is gravity useful for us? The uses of gravity in our life. What would happen if there were no gravity?
Wherever you go on the earth’s surface, the sky is always above you and the earth beneath you. You already know why this is true. The earth is shaped like a ball, or sphere. But because the earth is so big, its surface does not seem to curve. Even if you travel all the way around the earth, you cannot tell that you are on a curved surface. When objects are dropped at any place on this surface, they fail toward the earth. That is, they fail down.
While you were very young, you discovered that objects fall down unless they are held up in some way. Later on, you learned why this happens. All objects in our world are attracted by the earth, which pulls down ali the time on matter everywhere. This attraction by the earth is called gravity. The weight of anything is actually the force with which gravity pulls down on it. So whenever anything is lifted, the resistance of gravity must be overcome. Much work is done and much energy used in overcoming this resistance.
However, you know that gravity does not always resist our efforts. We often use its force to good advantage. Besides holding us to the earth, gravity is useful in many other ways. Gravity helps as whenever we want to slide or roll anything down a slope. Every time we weigh something, we are really measuring how hard gravity pulls down on it. Gravity also makes rain and snow fail to the earth. Then, because of gravity, water from the rain and melted snow sinks into the ground or runs downhill into streams and lakes.
When we turn a faucet on, water usually pours out. So most of us take a supply of water for granted. We hardly ever think about it unless there is a shortage of water. Yet, in almost every community, providing a supply of water is a big problem. For water is one of the few things that we all must have to stay alive. We also use a great deal of water for sanitation, fire fighting, and many other purposes. The water comes from streams and lakes or from the ground. But wherever the water comes from, gravity plays an important part in keeping us supplied with it.
Of course, gravity is useful in other ways though perhaps you have never thought much about them. In fact, you may not even realize that they have anything to do with gravity. From all your experiences with gravity, you expect its downward pull to make things move toward the earth. You can hardly imagine something being pushed up because of gravity. Yet this often happens, and you have seen it many times.
Whether you suck lemonade through a straw or pump water from a well, gravity makes the liquid move upward. Gravity also drives dirt from a rug up into a vacuum cleaner. Did you ever lift a big stone under water? As soon as you got it out of the water, it felt much heavier. The weight of the stone did not really change. But while the stone was in water, gravity helped you lift it. You know that boats float in water and that balloons and dirigibles float in air. They do this because of gravity.