What Direction Does the Earth Rotate?

 

Objective:  Use shadow measurements to determine what direction the earth rotates.

 Materials:  1 meter stick, jar filled with sand for support, level, sidewalk chalk, Playdough, golf tee, compass, beautifully sunny day.

 Procedure: 

  1. Place your 1 meter stick in your jar filled with sand.  Place the jar outside on a macadam surface in the morning of clear sunny day.  Make sure the stick is perfectly vertical using the level. 
  2. At the top of every hour during the day, use the chalk to trace the shadow of the stick.  Use the compass to determine the direction of the shadow from the stick..   Write the time and compass direction next to each traced line. 
  3. At the end of the day, create a data table of times and directions of each shadow.  You may even want to measure the length of each shadow and include that information in your data table.
  4. Attach the golf tee to the globe over your location using the Playdough.  Determine what direction north, south, east, and west would be from your golf tee. 
  5. Turn out the lights in the room and place the globe in front of the light beam of the overhead projector (or other bright light).  Try to orient the globe so that the shadow created by the light and the golf tee is similar to the first shadow your traced in the morning. 
  6. Now try to turn the globe so that the shadow moves exactly like the shadow you recorded on the macadam surface.
  7. Toward which direction is the Earth rotating to recreate your shadows?
  8. Now place a golf tee at a latitude that is the same as yours but on the opposite side  of the equator (place the golf tee along the same longitude). 
  9. Rotate the globe again making sure to replicate the shadows at your location as you measured them.  How is the shadow at the other location the same as your location?  How is it different?
  10. Place another golf tee at a location on the globe where there will be little to no shadow at the “noon” time.  You may have to practice several minutes to create that situation always making sure that the shadows created at your location do not differ from your actual measurement directions.  How does the shadow at this location move differently from the other two locations?
  11. Draw a scientific diagram showing how the shadow changes from (a) the morning, (b) noon time, (c) and afternoon at the three different locations.  Use compass directions when labeling your diagram.  Make sure to make the differences in length easily recognizable.

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