This is a pretty simple question, right? If you are asked that question you can give your address. Or you can describe the relation of your home or your town to a major landmark such as a lake, river, ocean, or mountain range. If you live in a small town, you might describe your home in relation to a larger town that more people might know. Or, if you want to get really technical, you could describe your latitude and longitude, to give your exact position on the earth's surface. But what if you were living several thousand years ago and got asked this question? Would it have been such an easy question then?

Well, you could certainly have named your town, nearby landmarks, and any larger towns close to you. But you wouldn't have been able to describe your location on the earth, because, back then, people didn't really have any idea what the earth was like. They knew the lands and waters near them, but didn't have any idea - or any maps - about what lay beyond the horizon.

Was the earth flat? Was it round? Was it a cylinder? Did the sun, moon and planets go around the earth? Or were they all standing still while stars farther away provided a moving background? Of course, the earth itself didn't move, did it?

These questions were all very important, particularly for explorers and traders who wanted to travel to other lands. How could they think about and picture the Earth and relate the picture to their travels? How could they know what to expect when they traveled?

About 2,000 years ago, Greek philosophers theorized that the Earth was round. They also theorized that the earth would be warmer near its center - nearer the sun - and colder near the poles, at the top and bottom. Of course, they also thought the earth was standing still while the sun paraded around it, but at least they got part of the equation right!

Based on these theories, they classified different parts of the Earth into zones and used those zones both to help travelers find their way and to give them an idea of the type of climate they might find in different places.

The Torrid Zone or hottest zone, is located just to the north and south of the equator. It includes the Tropic of Cancer north of the equator and the Tropic of Capricorn south of the equator. (Aristotle, one famous Greek philosopher, believed that the Torrid Zone was too hot for people to live! We know that's not true, but we also know that, in general, the climate in the Torrid Zone is the warmest on earth.)

North and south of the Torrid Zone were the Temperate Zones, where the climate was expected to be moderate and not extreme.

And at the very north and south of the Earth are the Frigid Zones, where, Greek philosophers thought it would be too cold for people to live. (They were wrong again, but the areas north and south of 66-1/2º latitude are, in general, the coldest places on the planet.)

Within these zones, mapmakers traced lines of latitude that circle the earth's surface. Information about latitude combined with the longitude lines that crisscross the globe in the other direction give travelers a great deal of information about where they are and where they are going - both travelers who think only the sun is moving and those who know that the Earth is moving as well!

Study questions:

1. The zone system gives a very rough description of the types of climates to expect in different parts of the world. A more exact system to map the climate was developed by Wladimir Peter Köppen. See if you can learn more about him and his system. Write a one-page paper about what you learn.

2. Use your classroom map or globe to identify at least one city in each zone: the north Frigid zone, the north Temperate zone, the Torrid Zone, the south Temperate Zone, and the south Frigid zone. Are there cities to be found in all five zones?

Check out past Trade Topics entries!