9-12 > Physical Science
 Grade level: 9-12 Subject: Physical Science Duration: One class period
 Objectives | Materials | Procedures | Adaptations | Discussion Questions | Evaluation | Extensions | Suggested Readings | Links | Vocabulary | Academic Standards | Credit

Find a video description, video clip, and discussion questions.

Stargazers

Students will understand the following:
 1 Redshift is a displacement of the spectrum of a celestial body, such as a distant galaxy, toward longer wavelengths. 2 Redshift is a consequence of the fact that celestial bodies are fleeing from us. 3 From that fact, scientists draw the conclusion that the universe is constantly expanding.

Your students will need research materials on light and color, in addition to a computer with Internet access. In addition, you should provide the following materials for each group:
 • Shallow pan • Water • Pencil

 1 Review with your students what they have learned about the spectrum and the behavior of light waves. Ask them if they know that what scientists have learned about the properties of light and color has helped them to make surprising and important discoveries about the properties of the universe. 2 Tell students they are going to do a simple experiment that will demonstrate how scientists have used understanding of light waves to make an important inference. Have them prepare by doing some preliminary research to learn the definition of the termredshiftand the implications of the redshift phenomenon. 3 Divide the class into groups, and have each group fill a shallow pan with water. Tell students they are going to use water waves as a model for light waves, in order to model the redshift of light. 4 Instruct group members to tap the surface of the water at the center of the pan with the end of a pencil, tapping with a fairly fast and regular frequency. 5 Students should notice that the waves move away from the pencil with a constant speed and equal wavelengths in all directions. 6 Next, ask students to predict what the waves would look like if the tapper moved the pencil to the left or right while tapping. Groups should discuss reasons for their predictions. 7 Have students test their predictions by moving the pencil to the left or right while tapping the surface of the water. If their observations do not match their predictions, groups should discuss why they do not. 8 Have each student write an explanation of how this demonstration helps us to understand why light from moving galaxies is redshifted, which means that the wavelengths of light coming from the galaxies are longer than expected. Students should include in their explanations why the redshift phenomenon implies that the universe is expanding.

 Provide students with a definition and simple explanation of redshift before they perform their experiment. Afterward, have them write up what they did, what they observed, and what they learned.

 1 When mentioning that Lowell’s observatory is near the Grand Canyon, the narrator points out that “the Grand Canyon is a great place to contemplate ancient events. You can see back across the millennia by looking down, or by looking up.” Discuss how geologists and astronomers look into the past by peering at the rocks on Earth and the stars in the heavens. How are astronomy and geology related and in what ways do their research projects intersect? 2 In modern astronomy, the human eye has been replaced by photographic plates and digital chips peering through modern telescopes. Give examples of how photography and computers have aided astronomers in making discoveries in the past century—discoveries that would not have been possible with eyesight alone. 3 As a young boy, Percival Lowell was awestruck with the natural beauty of Donati’s comet. What wonders of nature have had a lasting impression on your memory? Describe your personal reactions at the time of the observation. How have these experiences affected your life? 4 Name the astronomers and space scientists introduced in “Stargazers” who were directly influenced by Percival Lowell or through their experiences at Lowell Observatory. Describe their contributions to our understanding of the universe. 5 What evidence suggests that the Earth has been hit by “rogue” asteroids in the past, and what do you think is the likelihood that a large asteroid will hit the Earth in your lifetime? Support your opinion with information gathered from “Stargazers” and from a search of related topics on the Internet. 6 Many asteroid and comet discoveries are made by amateur astronomers who devote a lot of time and energy to carefully searching the heavens. Describe how you might use a camera and telescope to do a search for comets, asteroids, nova, and maybe even a new planet. Discuss whether or not you think it’s fair that some amateur astronomers get more public recognition for discoveries than others.

 You can evaluate your students on their explanations using the following three-point rubric: Three points:explanation accurate, complete, clear, and well written  Two points:explanation adequate, but lacking in clarity, and containing some writing errors  One point:explanation vague with some inaccuracies, unclear, with numerous writing errors You can ask your students to contribute to the assessment rubric by determining the best way to explain the redshift phenomenon.

 A Legacy in Flagstaff In the spring of 1894, a young pioneer was heading west to explore a different kind of frontier. Percival Lowell’s dream of proving the existence of life on Mars led him to build his observatory in Flagstaff, Arizona. Lowell’s observatory contributed to some of the 20th century’s greatest advancements in astronomy, from Hubble’s discovery of an expanding universe to the identification of Pluto. Celebrate the Lowell Observatory with a time line for your classroom bulletin board. Have students research the history of the observatory and place important dates on a time line, indicating the people and events that made that date important. Using an Internet search engine, students should find pictures, fascinating facts, and biographies of the people, the observatory, and the events mentioned in their time line. New Planet Discovered—Scientists to Call It_____________! Imagine that you and your classmates are part of a team that has just discovered a new planet. What name will you give the new planet? Find out why Clyde Tombaugh’s newly discovered planet was called Pluto and how the scientific community agreed on that name. List the rules that your class will use for coming up with a name for your new planet. Using those rules, name your planet!

 Stars and Atoms: From the Big Bang to the Solar System Stuart Clark. Oxford University Press, 1995.The concepts and ideas of modern astronomy and cosmology are presented in this clearly worded book which is supplemented with illustrations, charts, and tables. Read and learn about the universe and its fate, the big bang, galaxies and quasars, stars, and planets. The Story of Astronomy Lloyd Motz and Jefferson Hane Weaver. Plenum Press, 1995.Trace the evolution of the great astronomical ideas from their birth as pure speculations in the minds of the great ancient Greek astronomers to the reality of present-day astronomy. Read about Kepler, Tycho Brahe, Galileo, Newton, Gauss, and Einstein and the relationship between astronomy and physics.