YOU TRY IT! Eratosthenes’s Experiment

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WHAT YOU NEED

  1. Half of an 8x10 picture frame that forms an L shape
  2. A friend in another location with the same thing, same size
  3. Measuring tape or a ruler
  4. Phone

WHAT TO DO

  1. On a day that is sunny at both your location and your friend’s, call your friend.
  2. Both of you should go outside and place the picture frame on something flat, such as a windowsill or a patio. It is very important that the surface is level so one arm of the frame points straight up.
  3. Turn the bottom part of the L until the shadow of the upright piece falls along it.
  4. At the same moment, both of you measure the length of the shadow using the ruler.
  5. Compare your measurements.

There will be a difference in the length of the two shadows because of the curve of the Earth. The farther away you are from each other, the better.