Science Education Standards: Standard D3:

Most objects in the solar system are in regular and predictable motion. Those motions explain such phenomena as the day, the year, phases of the Moon, and eclipses.

Short Description: The varying appearance of the Moon over the course of a month results from changes in the relative positions of the Earth, Moon and sun. In the first activity, daily observations of the Moon over many weeks allow the phase cycle to be observed and characterized, and an explanation to be hypothesized. The hypothesis is tested in the second activity where students construct a working model of the Earth-Moon-sun system and determine if they can recreate the observed phase cycle. To truly develop a conceptual understanding of the phenomenon, students explore whether the Earth should exhibit a phase cycle as seen from the Moon, and whether an Earth observer should see other planets exhibiting phase cycles.