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9-12 > Physical Science
Grade level: 9-12 Subject: Physical Science Duration: One class period
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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

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.
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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.
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Discussion Questions

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.
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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.
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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!

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Suggested Readings

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.

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What secrets does Mars hold?
Did Percival Lowell suffer from Pareidolia when he reported seeing canals on the surface of Mars? Learn some of the mysteries of the red planet here.

Views of the Sky
Plan an evening of observation with your own backyard telescope. From this website you will find several options for generating sky maps that will locate planets, comets and constellations for your time and place (latitude and longitude) on earth.

Clyde Tombaugh’s Blinking Persistence
Find out in detail how a blink comparator is used to find faint objects in deep space.

Welcome to the Bradford Robotic Telescope Observatory site
This is like having an observatory in your classroom.The Bradford Robotic Telescope is located high on the moors in West Yorkshire, England. Anyone on the Internet can register and ask the telescope to look at anything in the northern night sky.

Mars Pathfinder Paper Model
Do your own simulated exploration of Mars by constructing this downloadable model of the Mars Pathfinder.

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Click on any of the vocabulary words below to hear them pronounced and used in a sentence.

speaker    opposition
Definition:A configuration in which a planet or other celestial body is opposite the sun in the sky as seen from Earth.
Context:Planet Mars was rushing toward Percival Lowell. Mars would soon be in opposition, the closest it would be to the Earth.

speaker    observatory
Definition:A building equipped for observation of astronomical phenomena.
Context:Despite its remote location, the Lowell Observatory attracted more pioneers—pioneer astronomers who would forever change our view of the sky.

speaker    interferometer
Definition:An instrument that utilizes the constructive interference of light waves for precise measurements by combining simultaneous images from two or more instruments separated by a given distance.
Context:The most powerful instrument for seeing, a giant interferometer, is a hybrid telescope which should be able to see the surface of distant stars.

speaker    redshift
Definition:A displacement of the spectrum of a celestial body toward longer wavelengths that is a consequence of the Doppler effect or the gravitational field of the source.
Context:It was ultimately realized that the redshifts of distant galaxies were due to the fact that these objects were fleeing from us.

speaker    blink comparator
Definition:A device for comparing two photographic images taken at different times.
Context:The blink comparator enabled the operator to flip the view between two star plates taken months apart. If anything moved it might be an asteroid, a comet, or lint—or an undiscovered planet.

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This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of theMid-continent Research for Education and Learningin Aurora, Colorado.
Grade level:6-8
Subject area:science
Understands the scientific enterprise.
Knows various settings in which scientists and engineers may work (e.g., colleges and universities, businesses and industries, research institutes, government agencies).

Knows that throughout history, many scientific innovators have had difficulty breaking through accepted ideas of their time to reach conclusions that are now considered to be common knowledge.

Grade level:6-8
Subject area:space science
Understands essential ideas about the composition and structure of the universe and the Earth’s place in it.
Knows that many billions of galaxies exist in the universe (each containing many billions of stars), and that incomprehensible distances separate these galaxies and stars from one another and from the Earth.

Grade level:9-12
Subject area:history
Understands the economic boom and social transformation of post-World War II United States.
Understands scientific and technological developments in America after World War II (e.g., the new system of scientific research and development, advances in medical science and how they improved the standard of living and changed demographic patterns, the global influence of the communications revolution ushered in by American technology).

Grade level:9-12
Subject area:space science
Understands essential ideas about the composition and structure of the universe and the Earth’s place in it.
Knows ways in which technology has increased our understanding of the universe (e.g., visual, radio, and x-ray telescopes collect information about the universe from electromagnetic waves; computers interpret vast amounts of data from space; space probes gather information from distant parts of the solar system; accelerators allow us to simulate conditions in the stars and in the early history of the universe).

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Ted Latham, physics teacher, Watchung Hills Regional High School, Warren, New Jersey.
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