This activity is designed to help middle school students understand that planets travel in nearly circular orbits around the sun, and that planetary motion obeys laws defined by Kepler and Newton. Students will explore interactive web sites demonstrating orbital motion and complete a series of modeling activities.
In this activity the learner will:
Building Background: Observing, Communicating, Comparing, Relating
1: Have students draw a simple picture of an orbit on paper.
Use these illustrations and their understanding of orbits to begin a unit-long
and start a guided discussion. Some sample questions might
Extensions: Go to NASA's Windows to the Universe Solar System Formation web site. Click on the small image of our solar system to get one that fills the screen. Then ask students, "What story does this picture tell?" Direct students to list observations that can be made about the solar system by looking at the diagram and images.
Repeat the activity with the following sites:
1) The Solar System Live: Students can examine a different view of the solar system. Point out the orbits of each of the planets shown on the diagram. Ask the students the following questions:
Students can look at a partial view of the solar system that includes actual photographic images taken by the Voyager probe.
Orbits are paths that describe dynamic phenomena. It is hard to deduce the shapes of planetary orbits from our moving Earth, but in some cases we can directly observe objects that are orbiting the planets. The following extension activities may be helpful.
There are commercial solar system simulators available as shareware. One such (for PC's) is PlanetWatch. Try downloading this simulator and watching as the planets (inner and outer) move around their orbits. The sizes of the orbits and the orbital periods are correctly proportioned in this package.
Ask students if they have observed satellites moving overhead and, if so, to describe to the class what they have seen.
Have your students examine the pair of photos showing the moons of Uranus. The two images were taken 90 minutes apart by NASA's Hubble Space Telescope. Ask students to list their observations. Why don't we have similar images of, for example, the orbiting moons of Jupiter?
The rings of Saturn consist
of particles orbiting the planet. Students should view the movie
(from Voyager) of the rings. What can they observe here?
Observing, ( Recording ), Communicating , Comparing, Organizing, Relating, Inferring
Have the class complete the playground ellipse activity. Direct students to write what they did and why they believe they got the shape they did.
Activity 3: Introduce students to Kepler and Newton with a short discussion of their lives, using information found in the Scientific Background Information.
Newton suggested a model for planetary orbits based on conic sections. To help the students visualize this concept, complete the conic section classroom activity.
Activity 4: 1. Kepler's third law (the Harmonic Law), relates the planets' orbital periods to their mean distances from the Sun. Ask students to complete the Harmonic Law activity.
2. The ellipse is the shape of a planetary orbit. We describe how "squashed" an ellipse is by giving a number, between 0 and 1, called its eccentricity. An eccentricity of 0 corresponds to a circle; however, if the eccentricity is close to 1, the ellipse is very flattened.
(a) NASA has an online
orbit simulator. Ask students to explore
the simulator at this site to learn about Kepler's laws of planetary
motion, and have student groups discuss their findings.
Have students complete the KWL chart from the beginning of the lesson by filling in the "What We Learned" section (sample below).
Encourage students to reflect and report on how their knowledge changed.
What were the understandings that students had when they completed the "What We Know" section of the KWL chart?
How did their perspectives change? Do they think their views may change again? Why or why not?
WHAT DID WE LEARN? (Sample)