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This physical model simulates the Sun’s tracks across the sky at
summer solstice, winter solstice,
and the spring and fall equinoxes. pdf 
A bead simulates the Sun moving from rising along the eastern horizon to setting on the western. The bead can be moved from track to track to demonstrate the solstices and equinoxes. The model is made to accurately represent the user’s latitude.
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This device, and the educational material around it, constitutes a single-purpose teaching machine with analogies to the second of the Programming Paradigms.