Globes

If you start heading east from the Prime Meridian you show it like this: 45° E, 90° E and so on. If you cross the other side of the earth at 180° and keep going, you change from using east to using west. Most maps show degree lines every 15 or 20 degrees. If you drew a line for every degree, you would have 360 lines running from north to south and 180 lines running parallel to the Equator. You would have lines all over the place. Having that many lines on a globe or map is not necessary. On the map showing the Prime Meridian and Equator you can see more lines.

Super Brain Question: Can you tell how many degrees there are between the lines in this picture? Click on the picture to get the answer.

Well, the geographers are now happy. They have a northern half, a southern half, a western half and an eastern half. Or, they have a Northern Hemisphere, a Southern Hemisphere, a Western Hemisphere, and an Eastern Hemisphere. And, they have a numbered grid to tell location.

By the way, the Equator and all the lines running around the earth from the North Pole to the South Pole are called lines of latitude. And, the lines running east and west from the Prime Meridian are called lines of longitude. Longitude lines are also called meridian lines.


	A globe is a model of the Earth. It is shaped like a ball or sphere. If you were in the space shuttle looking down on Earth, the Earth would look like a globe. I don't think you would see the names of the continents written on the Earth, however.
	A globe shows the continents on Earth without distortion. This means the continents look very close to how they really are. Flat maps have distortion. When you make a round object flat, shapes get a little twisted. Even though maps have distortion (are a little twisted), they are easier to work with. It is simple to find the continents on a globe. There are 7 of them. They are North America, South America, Europe, Africa, Asia, Australia and Antarctica. We'll talk more about continents later. Oceans cover most of the earth. There are 5 oceans - Pacific, Atlantic, Indian, Southern, and Arctic. When Professor Nibble was a kid, I was taught there are 4 oceans. But, in the year 2000, the Southern Ocean was named. More about oceans later.
	A globe has a top and a bottom. The top of the earth is called the North Pole. The bottom of the earth is the South Pole. The earth is not straight up and down as it travels through space. That's why most globes show the earth with a tilt. Because the earth is tilted, we have seasons and different lengths of days throughout the year. The two views of earth at the right are shown looking down at the north pole and up at the south pole. This is what the earth looks like from these angles. Do you see the Arctic Ocean and the Southern Ocean in darker blue? A geographer (person who studies the earth and the cultures of the people who live on it), needs a way to explain the earth and the distances from one place to another. Geographers decided that we should create an invisible line half-way between the North Pole and South Pole. This line divides the earth into a northern half and a southern half. The invisible line is called The Equator. You can see the equator on the globe above.
	If you set a globe on a table and look at it from a few feet away, you can only see half of it at a time. Half of a sphere is called a hemisphere. Hemi means half. You have to walk around the table or spin the globe to see the other half, or the other hemisphere. A hemisphere could be very confusing. There could be many of them. It all depends on where you are when you look at the globe. Geographers don't like things to be confusing. They had already divided the earth into a Northern Hemisphere and a Southern Hemisphere by making the equator line. They needed to decide where to draw another invisible line. This time the line would go from the North Pole to the South Pole. They could have decided on any location, but they agreed to draw the line through a town in England called Greenwich. The geographers named the line the Prime Meridian. Anything to the left of the Prime Meridian is west. Anything to the right of the Prime Meridian is east. The North Pole is almost always at the top of a globe or map.
	Here is a picture of the two main imaginary lines. The Prime Meridian goes north and south. The Equator goes east and west.
	Now we have the Earth divided into 4 hemispheres. This will help us tell direction. But knowing what is north, south, east and west is not good enough. It is a start. The geographers decided they needed more invisible lines to make a grid. And, they decided the lines should be numbered. The first thing they did was give the Equator the number 0. We say the Equator is 0 degrees. From the Equator, lines were drawn all the way up to the North Pole. The North Pole is 90 degrees north or 90° N. The South Pole is 90 degrees south or 90° S. So, from the North to the South Pole is a total of 180 degrees. As you may have figured out by now, degrees is a unit of measurement. We aren't talking temperature here. We're talking about the measurement of a sphere. Oh, there are about 70 miles between latitude lines.

	Now for the Prime Meridian. It was also given a number of 0 degrees. There are 360 degrees in a circle. There are 180 degrees in half a circle. So if you start heading west from the Prime Meridian, you will be on the opposite side of the globe when you reach 180 degrees. Anything from 0 to 180 west is shown like this: 90° W, 120° W and so on.
	If you start heading east from the Prime Meridian you show it like this: 45° E, 90° E and so on. If you cross the other side of the earth at 180° and keep going, you change from using east to using west. Most maps show degree lines every 15 or 20 degrees. If you drew a line for every degree, you would have 360 lines running from north to south and 180 lines running parallel to the Equator. You would have lines all over the place. Having that many lines on a globe or map is not necessary. On the map showing the Prime Meridian and Equator you can see more lines. Super Brain Question: Can you tell how many degrees there are between the lines in this picture? Click on the picture to get the answer. Well, the geographers are now happy. They have a northern half, a southern half, a western half and an eastern half. Or, they have a Northern Hemisphere, a Southern Hemisphere, a Western Hemisphere, and an Eastern Hemisphere. And, they have a numbered grid to tell location. By the way, the Equator and all the lines running around the earth from the North Pole to the South Pole are called lines of latitude. And, the lines running east and west from the Prime Meridian are called lines of longitude. Longitude lines are also called meridian lines.


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