Jupiter's Moons and the Pull of Gravity

Use the light travel time sheet to set the scale, then the Jupiter sheet as a graphing lab. Finish with the gravity rule sheet and its real planet data.

Find orbit lengths and speeds for Io, Europa, Ganymede and Callisto and graph period against distance. The directions on the page read: Read the text and fill in the table. Days and hours are each moon's period. Plot period against distance, starting at (0, 0). Circle the words in item 1. An answer key is included.

Yes, both. We made it for 8th grade Earth and space, and it works the same at home or at school. At home, a student can work through it alone and then go over it with you, which shows quickly what is solid and what needs another look. In class it works as independent practice, homework or a warm-up, and you can print one copy or a full set.

A light year is the distance light travels in one year, about 9.5 trillion km. Light from an object 4.2 light years away takes 4.2 years to reach us. Scale the Universe in Light Travel Time compares objects from the Moon to the Andromeda galaxy.

Gravity is stronger close to the planet, so a close moon must move fast to stay in orbit. On the Jupiter sheet, Io orbits in 1.77 days while Callisto takes 16.69 days. Students calculate each moon's speed.

Gravity between everyday objects is far too weak to feel. A pull large enough to notice needs at least one mass as huge as a moon or a planet. The gravitational pulls sheet asks students to explain this.