This applet has been designed to help students visualize the concept of solar and lunar eclipses. Students will use the applet to display graphics depicting the alignments of the Sun, Moon and Earth that produce the different kinds of eclipses.
From the initial screen, students will select one of three possible types of solar eclipses (2). The guiding text (3) comments that eclipses depend on the correct alignment of the Sun, Moon and Earth.
After selecting a type of eclipse, the graphics change to indicate how the Sun's rays (4) cast shadows on the Earth. The resulting shadows on Earth produce the eclipse we observe (5). Students can use the other toggle buttons (2) to observe and compare the alignments producing the different kinds of eclipses. At any point, students can click on the "Tell me more" button (3) to learn more about the alignments of the Sun, Moon and Earth.
After clicking on the "Tell me more" button, the graphics change to show both the Moon's orbit around the Earth (4) and the Earth's orbit around the Sun (3). Students should note that the Moon's orbit around the Earth (4) is tilted with respect to the Earth's orbit around the Sun. At this point, students have the opportunity to view when the Earth, Moon and Sun line up or when they do not (3).
Once students have selected the alignment scenario they wish to observe, the graphics are changed yet again. This time, the graphics depict the three-dimensional orientations of the Sun, Moon and Earth. Students can then use the controller buttons (2) to play the animation. As the animation progresses, the Moon continues its orbit around the Earth (5) and the graphic at the bottom left (4) indicates what observers on Earth would see. The buttons shown at the top left (3) enable students to return to previous sections of the applet or to view the other alignment scenario. For more information about the controller buttons, see below.