MIDDLE SCHOOLYARD EARTH-SUN SYSTEM OBSERVATORY

Major improvements can be made in teaching the earth's place in the solar system in Middle School with far-reaching benefits to understanding seasons, climate cycles, and the Scientific Method in general. Rather than showing pictures of the heliocentric solar system and merely informing students that the earth's rotation axis is tilted 23 degrees, I describe here a hands-on analytical model and experimental method that can transform student's understanding of the physical world around them and in so doing, key features of the solar system are rediscovered by students including the tilt angle of the Earth. Central to the Middle Schoolyard Earth-Sun System Observatory I describe is the construction and use of a new optical instrument I have designed that allows Middle School age students to make accurate yet safe measurements of the geocentric position of the Sun as a function of time and date in terms of Sun azimuth (angle with respect to true geographic north) and inclination or altitude (angle above the horizontal. This photometric solar compass inclinometer (PSCI) uses electronic devices to safely align the unit directly at the Sun and sustain this alignment long enough to accurately read azimuth and inclination from the attached compass and plumb bob compass. All the components are visibly functional so students can understand their role. Since the angular size of the Sun at the distance from the Earth is 32 arc minutes or 0.53 degrees and one rotation of the earth takes 24 hours, students have about 4 minutes to make a measurement accurate to about 1 degree. The graphical analytical model developed requires that a few math concepts normally taught in later years be introduced earlier in either Sixth or Seventh grades whenever earth science is the focus. In particular, polar coordinates and some aspects of right triangles are necessary to the construction. However, since science and math is often taught by the same teacher these vital math concepts become tractable and are taught naturally within their scientific context. Classes can share their measurements of the tilt angle with classes at other schools and show that once the local latitude is included in the model, the tilt angle is the same. Long-term variation of tilt over time can be introduced as a key part of global climate cycles.