Even the most casual observers note the changes in the phase of the Moon as it goes from crescent to half to full and back again with a "monthly" cycle. (See Glenn Simonelli's PUMAS submission "Modeling the motions of the Earth, Sun and Moon" [PUMAS Example 03_10_04_1].) Their observations, or what is "common knowledge", lead them to believe the Moon does loops around the Earth. But is this true? A comparison of the gravitational forces of the Sun and Earth on the Moon hints at the answer to this question and a simple demonstration refutes the loop-view.
Stephen J. EdbergDate Accepted: 2005-10-21 Grade Group: High School (9-12) Benchmarks: M3.4.1 M3.4.5 S13.4.6 S14.4.1 S14.4.2 Keywords: gravitation force moon sun earth tides inverse square law Microsoft Word: 08_19_05_1.docx PDF Document: 08_19_05_1.pdf