Stimulating Understanding of Computational science through Collaboration, Exploration, Experiment, and Discovery for students with Hearing Impairments
a collaboration of the Shodor Education Foundation, Inc., Eastern North Carolina School for the Deaf, Barton College, the National Technical Institute for the Deaf, and Interpreters, Inc.

For Teachers!

Orbital Speed Extension

Extension
All of these calculations are nice but what evidence do we have that will validate our conclusions? First, how can we verify that the moon's orbit isn't circular? People like to take pictures of the moon. If you take a picture of the moon every day for a month and compare the pictures, the size of the moon changes. This is because the moon appears larger when it is closer to the earth and smaller when it is farther away. The website "inconsistent moon" has animated the pictures to demonstrate the process. http://www.minervatech.u-net.com/moon/not_libr_ac.htm

Second, if the speed of the moon, and also the earth, changes then the timing of  events like full moons should be affected. Because the earth moves forward as it orbits the sun, it takes the moon extra time to move opposite the sun for a full moon. This makes a synodic month longer than a sideral month.  On average, full moons are  about 29.53 days apart. Because of the shape of the orbits and the resulting speeds of the earth and moon, the actual time between full moons may range from about 29.27 to about 29.83 days. The US naval observatory  gives tables of the phases of the moon. Your students can pick a full moon date from this data and use it as the starting date to predict future full moons. Have them put the date in a spreadsheet and make an algorithm that predicts future dates from it; see sample Excel spreadsheet. When they compare their predictions with the actual times, they will find a difference of a few hours. Have them calculate the range of error of their predictions. Then have them determine if their knowledge of the moon's varying speed can explain their inaccuracy.

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This project is supported, in part, by the National Science Foundation Opinions expressed are those of the authors and not necessarily those of the National Science Foundation.