72. Saving the World A student is talking to her teacher. S： I hear that scientists are planning to study asteroids and meteors， right？ T： Yes. They want to determine whether Earth is in danger of being struck by such a rock. S： What if they discover that a big one is coming straight for us？ T： In that case， there are two things they can do. They can launch rockets to push the rock off its course. S： So that it will miss Earth， right？ T： Right. And if that fails， we can try destroying the rock with nuclear missiles. S： Wow！ I never thought that nuclear weapons could save the world instead of ending it！