
Science Standards:
Nature of Science and Patterns of Change
Objectives:
Materials:
Directions:
1. Construction and alignment of sun dial. Set a toilet plunger
on the sidewalk or on a poster board and trace the circular bottom with
chalk so that it can be returned to its original position. It works best
to set the plunger on the south side of the walk or poster board. Mark
the position of the very top of the shadow with an "x" or a sticker. Note
the exact CLOCK time that the "x" was marked. Continue marking the top
of the shadow every 30 minutes.
2. Measure local noon. First, connect the "x"s with a curved, smooth line. The point that informed closest to the gnomen is when the Sun is directly in the south, local noon. Interpolating between the times of the known "x"s, determine the time of local noon.
3. Calibrate the sundial. Using the known "x" times, carefully scale the arc to indicate 9, 10, 11, 12, 1, 2, and 3 pm. The tip of the shadow will point be on the west side of the paper or sidewalk during the morning. Note how the length of the shadow changes over the day. How might it be different in another season?
4. Calculate the altitude of the Sun. The altitude of the
sun is determined by finding the inverse tangent of the gnomen height divided
by the shadow length.
5. Alterations. Using masking tape, place a large "x" on a south facing window such that there is a shadow of the "x" cast on the floor. Using more masking tape, mark the shadow on the floor every hour as it moves easterly across the floor; label the time and date for each mark. The arc that is created will vary everyday, getting larger in the summer and shorter in the winter (shortest arc on Dec. 21). This "masking tape sundial" can be used to keep track of solstices and equinoxes.