Calculating Measurements
in Space

	Perhaps you have driven or flown somewhere thousands of kilometers from
home.  On the earth, that distance means a long trip.  However, any distance
you travel on the earth is small, compared to distances in space.  These
distances are so huge, they are measured in units other than kilometers.  
	The astronomical unit, or AU, is one unit for measuring distances in
space.  One AU equals the average distance from the earth to the sun.  The
table gives the distance in AU units from each planet to the sun.
	Use adding machine tape to create a model of the solar system.  Let 1
AU equal 10 centimeters.  Locate the sun at one end of the tape.
	First, add Earth to your model.  Multiply 10 centimeters times the AU
value listed for Earth in the table.

1 AU x 10 cm = 10 cm

Put a dot on the tape 10 cm from the sun to show EarthUs position.  Use the
distances given in the table to find the positions of the other planets.  For
each planet, multiply its distance in AU units times 10 centimeters.  For
planets beyond Mars, you may want to convert your measurements to meters.

Talk About It

1.  What is an AU?
2.  How many times farther from the sun is Pluto than Earth?
3.  Light from the sun reaches Earth in eight minutes.  How long does it take
sunlight to reach Saturn?

				Approximate distance 
Planet			         from Sun (in AU)

Merucury				     0.4
Venus					     0.7
Earth					     1.0
Mars					     1.5
Jupiter				             5.0
Saturn				            10.0	
Uranus				            20.0
Neptune				            30.0
Pluto					    40.0


From Discover Science (1989) textbook, Scott Foresman 
[Excerpt and citation courtesy of a contributor. - mncharity]