In our lesson on hemispheres, we learned that a hemisphere is half of the earth.  The equator is the imaginary line that runs all the way around the world, dividing it into two equal halves, the Northern Hemisphere, north of the equator, and the Southern Hemisphere, south of the equator.

We also learned that we can divide the world in half, separating east from west by an imaginary line called the Prime Meridian.  Any place to the left, or west, of the Prime Meridian is in the Western Hemisphere, and any place to the right, or east, of the Prime Meridian is in the Eastern Hemisphere.

Do you remember . . . ?

In what hemispheres our continent of North America is located?

Latitude and Longitude

If you look at a globe, or map of the world, you may notice lots of lines that run up and down and side to side, covering the earth.  These are not real lines, they are grid lines drawn to help us find the location of places around the world.

The lines that run from left to right, or west to east, are called lines of latitudeThe equator is in the exact middle of the latitude lines.  These lines are always the same distance apart, and never cross.  Lines of latitude are also called parallels, as they are "parallel" to the equator.

You may also notice lines that run up and down, or north and south.  These are called lines of longitude.  All of these lines run from the north pole to the south pole.  The distance between lines of longitude is greatest at the equator, and gets smaller as they move towards the poles, where they touch.  This means they are not parallel.  Sometimes lines of longitude are also called meridians.  The Prime Meridian separates the Eastern Hemisphere from the Western Hemisphere.

Lines of latitude, and lines of longitude have numbers on them.  These numbers help us to find exact locations on a map.  They are measured in degrees.  Every place in the world has a certain degree of latitude, and degree of longitude.

Lets take a closer look at a map with these numbers on it.  We know the equator is the line of latitude that separates north from south.  The numbers on the lines of latitude tell us how far north or south, of the equator they are.  The equator is 0° (zero degrees) latitude.  The numbers go up, as we travel both north and south of the equator.  Lines of longitude are also numbered.  We have learned that the Prime Meridian separates east from west.  The Prime Meridian is 0° (zero degrees) longitude.  The numbers on the other lines of longitude tell us how far east or west, or how far away from the Prime Meridian.

Lets look at an example.  We'll find the location of New York State on the map above.  We have learned that New York is on the continent of North America, which is in the Northern and Western Hemispheres. Starting at the equator, we will go north on the latitude lines to the line that is closest to New York.  20° is too far south.  40° looks like it might be close.  Now lets begin at the Prime Meridian and travel west.  20° , 40°  and 60°  are not yet to the United States.  80°  looks too far west.  So, New York must be somewhere between 60° and 80° west latitude.

Now, let's look at the lines of latitude and longitude on the New York map below, and see if we are correct.  On the right hand side of the map, we can see the numbers 44°  N and 42°  N on two of the latitude lines.  As you can see, New York goes north of the 44°  line, and south of the 42° line, but most of the state is between those two lines.  So, we were correct when we guessed that 40°  on the world map was close.

On the bottom of the map we can read two longitude lines.  They are 78°  W 76°  W and 74°  W.  You can see that New York's borders are also west of the 78°  W line and east of the 74 W line.  Were we close guessing on the world map that New York State was between 60°  and 80° west latitude?  Yes, because the 70's are between 60 and 80.

Let's Review:

• Grid lines are drawn on maps and globes to help us find the location of places around the world.

• Grid lines called lines of latitude are also called parallels.

• Lines of latitude run across, west to east.

• Grid lines called lines of longitude are also called meridians.

• Lines of longitude run up and down north to south.

Let's Practice: Click on the globe below to see how well you can do on a practice quiz.

Maps courtesy of www.theodora.com/maps and http://www.nationalgeographic.com/maps

spinning globe courtesy of: http://www.bellsnwhistles.com

Definitions

 equator: an imaginary line that goes all the way around the earth, dividing it into two equal halves, a northern half and a southern half
 Northern Hemisphere: the half of the earth that is north of the equator
 Southern Hemisphere: the half of the earth that is south of the equator
 Prime Meridian: an imaginary line that goes all the way around the earth, dividing it into two equal halves, an eastern half and a western half
 Eastern Hemisphere: the half of the earth that is east of the Prime Meridian
 Western Hemisphere: the half of the earth that is west of the Prime Meridian
 North Pole: the point on the earth which is furthest north
 South Pole: the point on the earth which is furthest south
 lines of latitude: imaginary parallel lines, that run east and west around the earth, also called parallels
 parallels: another name for lines of latitude
 lines of longitude: imaginary lines that run north and south around the earth, they are not parallel, and are also called meridians
 meridians:  another name for lines of longitude

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