ENERGY "How much energy he has," we say when we see a little boy jumping up and down. "What a lot of energy that takes," we say when we see an expressman carrying a heavy trunk up a flight of steps. All work and play take energy. Energy is the ability to make things move.
Green plants make food for themselves. To do so they must have energy. They get it directly from the sun. As sunlight, which is one form of energy, shines on the plants, they are able to put water and carbon dioxide together to make sugar. People and all other animals get their energy from the sun, too, but secondhand. For they eat plants or animals that eat plants. Much of the food animals eat "burns" slowly in their bodies to produce muscular energy and heat, another form of energy.
Water rushing over a dam can turn a big water wheel. It has energy because it is moving fast. A stick of dynamite can blow up a building. It has what we call chemical energy. Electricity, magnetism, and sound are among the other forms of energy. We can use them all to make things move.
We are just beginning to harness still another form of energy—atomic energy. In time we may be using atomic energy to do most of the work of the world
