What if you want to talk right now to a friend who lives far away? The answer is simple. You pick up your telephone and press some buttons. Next, you hear a ringing sound—one, two, three rings. Then you hear your friend’s voice say, “Hello.” Making a phone call seems so easy. But did you ever think about what makes it possible?

When you pick up your phone, it instantly hooks up with a vast, worldwide telephone network. The network has millions of miles of wire. It has cables that run under the oceans.