Write on a board or a sheet of chart paper the terms latitude and longitude. Let students share what they know about the terms. Write down information that students share. Correct any misconceptions they might share.

Explain that the lines of latitude and longitude (see sidebar for tricks to help students remember the difference) comprise an imaginary grid that has been placed over the globe.

·         The lines that run across the grid -- the flat lines -- are lines of latitude. The Equator is an example of a line of latitude. The Equator is the latitude line that divides Earth into two hemispheres, the northern hemisphere and the southern hemisphere. The Equator is the 0 point of latitude. Latitude lines North of the Equator are referred to as North latitude; latitude lines South of the Equator are referred to as South latitude.

·         The lines that run up and down on the grid -- the tall lines -- are lines of longitude. The lines of longitude are also called meridians. The Prime Meridian, which passes through Greenwich, England, is the longitude line that divides Earth into two hemispheres, the eastern hemisphere and the western hemisphere. The Prime Meridian is the 0 point of longitude. Longitude lines East of the Prime Meridian are referred to as East longitude; longitude lines West of the Prime Meridian are referred to as West longitude.

Help students further understand the concepts by giving them some hands-on practice. First, determine the latitude and longitude coordinates for your students city and state.

If you are not sure of the coordinates, you can use this tool, the Latitude and Longitude Finder, to find your local coordinates. Just type in your City, State.

Write the latitude and longitude of your location on a board or chart. Help students use the Equator and Prime Meridian, and the lines of latitude and longitude, to find the location that matches the coordinates given. Students should land on their town!

Next, provide the following coordinates and have students use a map to identify the location that is identified by each set of coordinates:

·         48 degrees () North latitude, 2 degrees () East longitude (France)

·         19 degrees () North latitude, 154 degrees () West longitude (Hawaii)

·         40 degrees () North latitude, 116 degrees () East longitude (China)

·         12 degrees () South latitude, 77 degrees () West longitude (Peru)

·         33 degrees () South latitude, 151 degrees () East longitude (Australia)

·         43 degrees () North latitude, 79 degrees () West longitude (Canada)

·         20 degrees () South latitude, 50 degrees () East longitude (Madagascar)

When most students seem to grasp the concepts of latitude and longitude, provide the Where in the World? work sheet as longitude and latitude practice. See the Assessmentsection below for work sheet answers.

Extend the Lesson

·         Create a set of cards, one card per student. On each card write the coordinates of a location someplace in the world. (You might use this list as a source.) Pass a card to each student and have them find and indentify the location on a world map.

·         Create a Coordinate BINGO game. Provide a list of 24 country names around the world for which you have coordinates (source). Have students write the name of each country in a block on their BINGO game card. Then call out the coordinates of one of the 24 countries. Players X the name of the country that matches those coordinates. The first player to get five Xs in a row is the winner.

2.4 Celestial Coordinates

• We describe the celestial sphere using a similar geographical notation:
• The North Celestial Pole is the point on the celestial sphere directly above the Earth's North Pole.
  
  Similarly, the South Celestial Pole is directly above the Earth's South Pole.
• The star Polaris, in the constellation Ursa Minor, is located very close to the North Celestial Pole.
  
  Polaris is therefore also called the North Star.
  
  Question: can you identify Polaris in the photo of the polar skyabove?
• The celestial equator is directly above the Earth's equator.
   
• Positions on the celestial sphere can also be measured relative to these markings, although different names are used besides latitude and longitude.
   
• Declination corresponds to latitude, and is measured in the same way, but relative to the celestial equator (0° dec).
  
  The north celestial pole is at 90° north declination (+90° dec). The south celestial pole is at 90° south declination (-90° dec).
  
  Circles of constant declination are all parallel to the celestial equator.
   
• For any position on the surface of the Earth, the point on the celestial sphere that is directly overhead is called the zenith.
  
  Since the Earth and the celestial sphere are concentric, simple geometry shows that the zenith will always have a declination equal to the latitude of the observer (such as for Atlanta in the picture).
   
• A star's position along a circle of constant declination is described by a second number called right ascension.
  
  Right ascension corresponds to longitude, but different units are used.
  
  Instead of 360°, a circle is broken into 24 hours of right ascension.
  
  So, 360° = 24 h R.A., 15° = 1 h R.A., and 1° = 4 min R.A.
  
  Note that hours of right ascension is a unit of angle, not time, although there is an obvious connection due to the daily rotation of the celestial sphere.
   
• Right ascension is measured from the celestial meridian, chosen to be 0 h R.A. (which is also the same as 24 h R.A.)
  
  The celestial meridian is a semicircle connecting the celestial poles and passing through a particular point on the celestial equator called the vernal equinox (defined below).
  
  Question: to what position on Earth is the vernal equinox analogous?
  
  Right ascension increases from west to east (note that we are looking at the exterior of the celestial sphere in the above picture).
   
  
  
• With the two numbers of declination and right ascension, the position of any object in the sky can be precisely described.
  
  Question: what is the approximate position of the galaxy shown?
  

Whole-class discussion

Listen in order to comment or ask genuine questions