Why does the Moon not always look the same to us? Sometimes it is a big, bright, circle, but, other times, it is only a tiny sliver, if we can see it at all. The different shapes and sizes of the slivers of the Moon are referred to as its phases, and they change periodically over the course of a lunar month, which is twenty-eight days long. The phases are caused by the relative positions of the Earth, Sun, and Moon at different times during the month.

Students work in teams of two to discover the relative positions of the Earth, Sun and Moon that produce the different phases of the Moon. Groups are each given a Styrofoam ball that they attach to a pencil so that it looks like a lollipop. In this acting-out model exercise, this ball on a stick represents the Moon, the students represent the Earth and a hanging lightbulb serves as the Sun. Students move the "Moon" around them to discover the different phases. They fill in the position of the Moon and its corresponding phase in a worksheet.

Video description:  Join NASA to learn more about solar eclipses, especially the awe-inspiring phenomenon of total eclipses. Find out about the unique geometry and the distances and sizes of the sun and moon as seen from Earth that allow us to witness the sun's corona or actually be in the path of totality.  Video length:  7:15. NASA eClipsTM is a suite of online student-centered, standards-based resources that support instruction by increasing STEM literacy in formal and nonformal settings.  These free digital and downloadable resources inform and engage students through NASA-inspired, real-world connections.NASA eClips Launchpad videos focus on NASA innovations and the technology that take us into the future.  These segments support project-based and problem-based learning experiences in science, mathematics, and career and technical education classrooms.

Video Description:  What causes the phases of the Moon? From New Moon to Full Moon, the Earth-Sun-Moon system is responsible for the Moon’s changing phases. Learn more about rotation, revolution and this repeatable pattern. Video Length:  3:13. NASA eClipsTM is a suite of online student-centered, standards-based resources that support instruction by increasing STEM literacy in formal and nonformal settings.  These free digital and downloadable resources inform and engage students through NASA-inspired, real-world connections.NASA eClips Our World videos (grades 3-5) help students understand the differences between science (the natural world) and engineering (the designed world).  These video segments supplement elementary learning objectives not only in science, technology, engineering and mathematics, but also in reading, writing, visual and performing arts.