资料题：Why does the witter use the example of the Greek scientist who calculated the distance around the world（　）。

In the opinion of many Americans and Europeans, we began to really explore our world only in the sixteenth century.According to them, the sailors of the ancient world did not explore distant parts of the word; they did not have the necessary knowledge or skill for long sea journeys.However, the people who have this opinion are forgetting two important facts of history.First, sometimes early scientists have an idea which is correct, but scientists in later centuries do not believe it.For example, about 270 B.C..a Greek scientist had an idea which we all believe today: The earth moves around the sun.But for the following 1 ,600 years scientists did not: believe this.In their opinion, the sun clearly moved around the earth.They discoveredthe truth again only in the fifteenth century!The second fact of history that many people forget is this: Ancient does not mean primitive.For example, the ancient Egyptians knew a great deal about the stars; they used this knowledge to find their way across the oceans.Two thousand years ago a Greek scientist who lived in Egypt calculated the distance around the earth.The results of his calculations were close to the actual distance we know today! So the ancients had a great deal of scientific knowledge.They also had skills which equaled the skills of today.For example, 1 ,300 years ago and before, fishermen in Ireland built their boats of wood and leather.Today some fishermen in Ireland still make boats of the same design.They use tools and materials which are not very different from the tools and materials which their ancestors used.Why? The ancient design of the boats is good, and with skilful sailors, these boats can sail in all kinds of weather.Clearly, long before the sixteenth century, people had the skill, the knowledge, and the equipment which were necessary for long journeys by sea.The world did not have to wait until the sixteenth century for its first explorers!