Clea Home Page  JUPITER'S MOONS AND THE SPEED OF LIGHT  Please sign our mailing list and let us know which of our exercises you are using in your classes

A Description of the Lab: 

Purpose: To illustrate the classic experiment of 1676 in which Ole Roemer first determined the finite speed of light using timings of eclipses of Jupiter's moon Io.

Jupiter's Moons and the Speed of Light, uses a version of Project CLEA's Jupiter's Moons software.. Students view a simulated telescopic view of Jupiter and its satellites. After identifying Io, they record the precise time when the moon enters Jupiter’s shadow at a date about two months after conjunction. Using the recorded time of this eclipse and the known period of Io, students predict the time of an eclipse near opposition and then record the observed time of that eclipse. The discrepancy between the predicted and observed times, along with the difference in the distance between Earth and Jupiter at the two eclipses yields a value of the speed of light accurate to about 10%.  Software provided with the exercise enables students to calculate predicted times and Earth/Jupiter distances, as well as to analyze the time discrepancy and to visualize the logic of the analysis.   A student manual, including historical and scientific background of the exercise is provided. 

Required Windows Software

The Speed of Light Exercise uses a version of the Jupiter's Moons software, Click Filename to Download (using left mouse button to "Save Link As") This  is a zip file that contains an .exe file that will  install itself when you run it on your computer, producing two icons, one for the Roemer Speed of light exercise, and one for the Mass of Jupiter exercise (see the CLEA listing and manuals for the Mass of Jupiter exercise by cllicking here).


You will also need the manual---downloadable from the link below or from our manuals page (where it is available in both .doc and .pdf formats): take a look and see what the exercise entails!

Student manual For the Roemer experiment(MS Word format)

Overview of Software   Overview of Manuals CLEA Home Page