背誦為王第三冊第25課

Power
There is not enough petrol in the world for everybody now. And each year there is less.So what are we going to do when it finishes? Perhaps we will go back to horses and carriages and bicycles. In the second world war, some people did not use petrol in their cars. They need gas from wood and plants instead. And then they put it in big bags on top of their cars. The cars did not go fast, but it was better than nothing. We cannot cut down all our trees to make gas. We need them for other things too. Besides gas, we can also use electricity for our cars. But first, we must make the electricity. Some countries have coal and they make electricity with that. But we will not always have coal. Other countries have great rivers which turn turbines and generate electricity more easily and cheaply. We are also able to get power from the tides. We put turbines in the mouth of a river, then when the tide comes up, it turns the trubines and when it runs back towards the sea, it turns them again. We know that the waves of the sea can also turn turbines when they go up and down. Will all of these things generate our electricity in the year 2050?