Students will

The class will need the following:


Complete the Classroom Activity Sheet as a wholeclass project. Instead of completing all seven problems focus on four or five. Students may also enjoy completing the TakeHome Activity Sheet together as a class. 

You can evaluate students using the following threepoint rubric:

How Many Miles Are There in a Light Year? Tell students that we know that light travels at a speed of 186,000 miles per second. Have them use that information to figure out how many miles are in a lightyear. Then have them try to figure out a scaling factor to help make the large distance easier to understand.
Answer: Multiply the speed of light by the length of time in one year. The tricky part, however, is that the speed of light is expressed in miles per second. Because you have to keep the units the same, you must figure out the length of time in one year in seconds. To do that, multiply the number of days in one year (365) times the number of hours in one day (24) times the number of minutes in one hour (60) times the number of seconds in one minute (60). The answer is 31,536,000 seconds. To find out how many miles are in a lightyear, multiply 186,000 miles per second by 31,536,000 seconds. The answer is about 6 trillion miles. To understand what this means, think of Earth, which has a diameter of 8,000 miles, as being the size of a pea, which has a diameter of ¼ inch. Using that scale, a lightyear would be about the distance across the United States.

The Astronomy Café: 365 Questions and Answers from "Ask the Astronomer" Sten Odenwald. W. H. Freeman, 1998. Using a questionandanswer format, the author covers a wide range of information about space. Each chapter is preceded by a short description of the questions most people have about astronomy. Many questions relate to the distances between the stars and planets and their relative sizes. A few color plates, along with charts and graphs, add to the text. Milestones of Science Curt Suple. National Geographic, 2000. Filled with the luscious photographs that are National Geographic's trademark, this title traces the history of science from prehistory to the present. Each chapter covers a particular time span and the development of man’s understanding of the universe. Especially exciting are the chapters that cover the development of modern astronomy, from Galileo to today's space flights. 
Comets and Shooting Stars [PDF] Find information and additional activities on this topic at the Johns Hopkins Applied Physics Lab website. 
astronomical unit Definition:A unit of length used in astronomy equal to the mean distance of Earth from the sun, or about 93 million miles (150 million kilometers). Context:In expressing planetary distances, multiples of the castronomical unit —the average distance from Earth to the sun—are often used. lightyear Definition:A unit of length in astronomy equal to the distance that light travels in one year in a vacuum, or about 5.88 trillion miles (9.46 trillion kilometers). Context:Many astronomers prefer to uselightyearsto measure stellar distances because they are easier to work with than other units. parallax Definition:The angular difference in the direction of a celestial body as measured from two points in Earth’s orbit. Context:After measuring the star’sparallax, astronomers were able to determine that the star was much closer than previously thought. scaling factor Definition:The proportion between two sets of dimensions. Context:The map indicated ascaling factorof 1 inch to every 10 miles. 
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 K12 Education: 2nd Edition and have been provided courtesy of theMidcontinent Research for Education and Learningin Aurora, Colorado. Grade level:912 Subject area:Mathematics Standard: Understands and applies basic and advanced properties of the concepts of numbers. Benchmarks: Understands the properties and basic theorems of roots, exponents (e.g., [b^{m}][b^{n}] = b^{m+n}), and logarithms. Grade level:912 Subject area:Mathematics Standard: Understands and applies basic and advanced properties of the concepts of measurement. Benchmarks: Selects and uses an appropriate direct or indirect method of measurement in a given situation (e.g., uses properties of similar triangles to measure indirectly the height of an inaccessible object). Grade level:912 Subject area:Mathematics Standard: Understands and applies basic and advanced properties of the concepts of measurement. Benchmarks: Uses unit analysis to solve problems involving measurement and unit conversion (e.g., between the metric and U.S. customary systems and in foreign currency conversions). 
Chuck Crabtree, freelance curriculum writer. 
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