• Assess students’ prior knowledge about satellites during the warm-up activity.
• Check for understanding based on students’ answers to the question on the Satellites handout and the discussion questions after the video.
• Observe students during the hands-on activity and have them use vocabulary terms to describe their models.
• Collect and check the Earth-Moon-Sun worksheet and the Moon Math worksheet.

Day 1

Open the lesson by having students write one fact they know about satellites and one thing they would like to know. Assess prior knowledge by having them share what they know about satellites.

Give students copies of Satellites (S-7-9-2_Satellites.docx). Have them read the selection, and write an answer to the “Check Your Understanding” question. Then, discuss the answer to the question with the class.

Define the following terms and have students write the definitions in their notes: gravity, inertia, orbit, planet, revolution, rotation, satellite.

Use a projector to show students the 2-minute video, “Why Doesn’t the Moon Fall Down?” at www.teachersdomain.org/resource/ess05.sci.ess.eiu.moonorbit/. Ask follow-up questions to check for understanding:

• “What would happen to the Moon’s motion if it were moving faster through space?” (The Moon could escape Earth’s gravity and travel away from Earth into space.)
• “What would happen to the Moon’s motion if it were moving more slowly through space?” (The Moon could be pulled into the Earth by Earth’s gravity.)
  • “How could we cause a human-made satellite to orbit the Sun but not the Earth?” (We could launch it into space with enough velocity to travel beyond the inward pull of Earth’s gravity so that it orbits the Sun instead.)

Have students work in pairs to model the motion of the Earth, Moon, and Sun. Give each group three foam balls of different sizes. Have them determine which balls will represent the Earth, Moon, and Sun. Then, have them move the balls to show the rotation and revolution of the Moon around Earth, and the Earth around the Sun. Visit each group and have them use vocabulary terms to describe their models.

Give students copies of the Earth-Moon-Sun worksheet (S-7-9-2_Earth-Moon-Sun Worksheet and KEY.docx). Have them answer the questions and make a diagram that shows the motion of the Earth, Moon, and Sun due to gravity. Go over the answers with the class and draw the diagram on the board.

Day 2

Explain to students that we can calculate our age and weight on the Moon. First, demonstrate how to use a conversion factor to calculate weight on the Moon. Explain that weight is a measure of the amount of gravity pulling on an object, so our weight can change depending on our position in space. Ask students,

• “Which has a stronger force of gravity, Earth or the Moon? Why?” (Earth, because it has more mass.)
• “What if the Moon was more massive than Earth?” (Earth would be the moon that orbits the Moon!)

Tell students that the Moon’s gravitational pull is only 1/6 of Earth’s, or 0.16. To find weight on the Moon, multiply the Earth weight by 0.16.

Example:

Rex the cat weighs 12 pounds on Earth. How much does he weigh on the Moon?

12 pounds × 0.16 = 1.92 pounds.

Rex weighs less than 2 pounds on the Moon!

Then, demonstrate how to use a conversion factor to calculate age on the Moon. Ask students, “Which takes longer to make one ‘lap’ around its larger orbiting body, the Moon around the Earth, or the Earth around the Sun? In other words, which one has a longer period of revolution?” If students are not sure, have them refer to the Moon and Earth Comparison Chart (S-7-9-1_Moon and Earth Comparison Chart.docx). The Earth’s period of revolution is 365 1/4 Earth days, but the Moon’s period of revolution is only about 27 Earth days, so Earth’s period of revolution is about 13 times longer than the Moon’s. That means the Moon’s year is 0.075 as long as an Earth year. To find age on the Moon, multiply the Earth age by 0.075.

Example:

Rex the cat is 10 years old on Earth.

10 Earth years × 0.075 = 0.75 Moon years

Rex is only 9 months old on the Moon.

Hand out the Moon Math worksheet (S-7-9-2_Moon Math and KEY.docx) and have students practice the conversions on their own.

Extension:

• Students who might need an opportunity for additional learning can read The Three Little Piggy-back Satellites Web site, and check their understanding by playing the Nanosat Flingman game at http://spaceplace.nasa.gov/en/kids/st5/flingman.shtml#.
• Students who may be going beyond the standards can play the “Missions to Planet Earth” game, which focuses on how NASA uses satellites to learn about Earth, available at http://spaceplace.jpl.nasa.gov/en/kids/earth/card-game/#.
• Students who may be going beyond the standards can read more about NASA’s Clementine Mission or Lunar Prospector Mission, and write a brief description of the mission and its objectives (see Related Resources for suggested Web sites).
• Students who might need an opportunity for additional learning can circle unfamiliar terms on the Satellites handout as they read. They can practice using the new vocabulary terms by writing meaningful sentences with those words.
• Walk students, who might need additional practice, through the modeling activity step-by-step.