Classroom Demonstration Guidelines
(Planetary Orbit Simulator)
The following sequence of directions are steps an instructor might choose to follow in
demonstrating the Planetary Orbit Simulator in a classroom situation. We provide these
suggestions with appropriate questions (shown in bold italics) to pose to the class as an aid in
promoting interactivity. We encourage instructors to adapt these suggestions to their particular
educational goals and the needs of their class.
Animation Demonstration Directions Interactive Questions
Start the applet in its default configuration. 1. What shape is this?
You will be on the Kepler’s First Law tab After the eccentricity was changed to 0,
viewing an ellipse with a = 1 AU and e = 0.4. the shape turns into a perfect circle.
First change the eccentricity to e = 0. 2. What is this distance called?
The distance is called the major axis.
Answer questions 1-2
3. Is the sun still at the center of the
ellipse? No, the sun is more towards
Change the eccentricity back to e = 0.4. the left side of the circle.
What is at the center?
Click show center. At the center, there is the midpoint of the line
connecting the foci.
Click show radial lines. 4. If I increase eccentricity what will
happen? If the eccentricity is
It is useful at this time to drag the planet increased, then the circle shape would
around to illustrate that the sum is 2a. become more towards looking like a
line, because when the eccentricity is 1,
Answer questions 3, 5-6 it is a completely straight line.
5. When eccentricity is varied does the
semi-major axis change?
Click show semimajor axis. No, the semi major axis isn´t changing.
Answer question 7
6. Does the Earth’s orbit look very
elliptical? No, the Earthś orbit isn´t
Use the set parameters for menu to select the very elliptical as the eccentricity is
Earth and click OK. The earth’s orbit will now close to zero, it is 0.017, so it looks
be illustrated the main window. more of a circle
Answer 8
Use the set parameters for menu to select 7. Does Pluto’s orbit look very elliptical?
Pluto and click OK.
Answer 9
NAAP –Planetary Orbit Simulator – Classroom Demonstration Guidelines 1/2
Pluto´s orbit doesnt look elliptical as the
eccentricity is also close to zero, so it
looks more like a circle.
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