Unit D: Atmosphere and Solar System
1. Get Set to Explore
- atmosphere: The mixture of gases that surrounds Earth.
- electromagnetic wave: Waves of energy that can travel through a medium or through a vacuum; light, for example, travels as electromagnetic waves.
- If the weather is expected to be clear a few days before you will do the simulation, assign students to go outside with an adult in their family at night and look at stars. Encourage students to make careful observations of the stars–their brightness, color, twinkling, movement, etc. They should also observe weather conditions, such as clouds, haze or mist, humidity, and temperature. Tell students to take notes. Hold a class discussion for students to share their observations of the stars and of the weather on nights that they observed. Record students' observations on the board.
- Introduce or review the vocabulary words and go over the definition of each word.
- Explain that astronomers sometimes give a star's location by noting its distance, in degrees, above the horizon at a particular time. Pass out protractors and refer students to the degree markings along the curve. Ask: Which star would be higher in the sky, one that is 70° above the horizon or one that is 40° above the horizon? (The closer a star is to 90° above the horizon, the higher it is in the sky.)
- Encourage students to share any more observations or ideas they have about the twinkling of stars. Then present the Discover! question.
2. Guide the Exploration
- Direct students to launch the Discover! Simulation and to listen to the question. Let students pose possible answers, referring them to the hints the simulation gives.
- Give students copies of the Three-Column Chart for taking notes. As students do the simulation, tell them that they can move their cursor over different parts of the diagram for two more hints. They should click each of the three buttons near the stars to learn how starlight reaches the location marked on the globe. Have students review the information, related to angles, about star locations above the horizon.
- When students have completed Step 2, have them discuss their ideas about what makes stars twinkle. Record them on the board.
- Go over Step 3's Wrap-Up text with the class. Explain that the movement of the air in Earth's atmosphere causes the light rays from the stars to jiggle. That is what causes stars to appear to twinkle.
- Pose the Extension question, and let students work in groups to formulate an answer. Guide the class to realize that a number of local conditions would alter the appearance of light rays traveling through the atmosphere, causing the stars to appear to twinkle more.
If time permits, present students with the following questions:
- Inquiry Skill Ask Questions What questions do you have about stars and starlight? Work with a classmate to come up with three or more questions. Answer: Topics students might consider include why some stars appear brighter than others, how scientists determine the distance of stars from Earth, the gases that make up stars, or name stars. All questions related to stars or starlight are acceptable. Encourage students to use library or Internet resources to try to answer more of their questions.
- Critical Thinking Apply Imagine traveling down a road on a clear, hot day in summer. Ahead of you, you see what appears to be a puddle on the road in the distance. When you reach the spot where the puddle seemed to be, the pavement is dry and another puddle appears in the distance. How is this mirage of a puddle similar to the twinkling of starlight? Answer: The shimmering puddle is the light reflected off the pavement and traveling through the atmosphere. The air along the ground has hot spots and cool spots; since hot air rises and cool air falls, the light traveling through the moving air appears to jiggle, making the mirage.
4. Reaching All Learners
On Level: Visual Learners
Have visual learners make drawings to show how starlight travels different distances through the atmosphere with stars at different heights in the sky. They should use a large sheet of paper, making the atmosphere a band 2 to 5 inches wide, so that the differences in distances will be apparent. They should use a protractor to draw and label at exactly 79°, 50°, and 39° above the horizon, as in the simulation. They can then use a ruler to measure the differences in distance that the starlight from these stars travels through the atmosphere.