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Group Activities

  1. Have your partner walk ten paces away from you. With your hand, measure the angle between your partner and a distant landmark like a radio tower. Move two steps to your left and repeat the measurement. The difference in angles you measure is the parallax of your partner. Have your partner walk ten paces farther away and repeat your angular measurements. Now have your partner make the angular measurements with you at distances of ten and twenty paces. Try to deduce the relationship between parallax and distance. Compare your result with Equation 16.1.
  2. Travel with your group to a dark spot on a clear, moonless night. By counting the number of stars that can be seen in one quadrant of the sky (for example, all stars between the horizon and the zenith with azimuths between due south and due west), have each member of your group estimate the total number of visible stars in the sky. If you have at least four members of your group, be sure to include all four quadrants of the sky. Average the estimates to get an overall estimate of the number of visible stars. Repeat the observations at the time of full Moon. Compare the results and have the group discuss what the results imply about the number of stars that can be seen near cities, near small towns, and far from cities and towns.

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