Cycles in the Sky. Teacher Guide: Cycles in the Sky Page 1 of Discovery Communications, LLC

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1 Cycles in the Sky What is a Fun damental? Each Fun damental is designed to introduce your younger students to some of the basic ideas about one particular area of science. The activities in the Fun damental provide essential background knowledge that students need before they move on to the more difficult concepts that are presented in other parts of Discovery Education Science. In Cycles in the Sky, students are introduced to some of the basic ideas behind the causes of day and night, the cycle of Earth s seasons, and phases of the moon. All Fun damental activities encourage active exploration. Students should try different choices and combinations within each activity. Some responses will be correct, and the student will receive an explanation of why the response is correct. Some responses will not be correct, and the student will receive an explanation of why the response is incorrect. In online activity learning, incorrect responses are often more valuable for learning than correct responses. The Fun damental can be used by individuals, small groups, or as a whole class demonstration. The home page offers two choices: Earth and Sun in which students look at the astronomical causes of Earth s cycles of day and night; years; and seasons, and Moon Phases in which students examine the cycle of moon phases. The Home button at the top of the screen will always bring students back to this home page. Clicking the speaker button at any time will activate the text reader to read the text on that screen. Earth and Sun How the Fun damental Works The first part of the Cycles in the Sky Fun damental is Earth and Sun. In this part, students do activities designed to familiarize them with the following content objectives: The sun is a star. It produces energy, including heat and light. Some of the sun s energy travels through space to Earth. Earth spins or rotates like a top. The imaginary line in the center of that top is Earth s axis. The axis runs through Earth s North and South Poles. Teacher Guide: Cycles in the Sky Page 1 of Discovery Communications, LLC

2 The spinning of Earth on its axis causes the cycle of day and night. Earth rotates one full turn around its axis in 24 hours. At any given time, one side of Earth is facing the sun and the other side is not. The side facing the sun is experiencing daylight; the side facing away from the sun is in the dark and experiences night. Like other planets, Earth revolves around or orbits the sun. The time it takes for a planet to complete one orbit around the sun is what we call a year. For Earth, that is equal to about 365 days. Earth s axis is not straight up and down. It is tipped or tilted. Earth s axis always points in the same direction even as Earth orbits the sun. There are points in Earth s orbit where Earth s axis is pointing directly toward the sun, directly away from the sun, and exactly in between. These points mark the beginnings of seasons. The cycle of seasons marks the cycle of the year. The first part of Earth and Sun opens with a series of short interactive screens. Students click through diagrams and animations showing how only one side of Earth at a time is lit by the sun, how Earth rotates on its axis, and how these two things combine to cause the cycle of day and night. Next, students do an activity in which they look down on Earth s Northern Hemisphere from above and are allowed to rotate Earth in either a clockwise direction or a counterclockwise direction. Students choose one of four Northern Hemisphere cities to examine: Seattle, New York, London, or Moscow. The location of the chosen city is indicated on Earth by a red dot. As the students rotate Earth, they will see two things happen: 1) the city s location will change, and 2) the local time for that city will change. Naturally, Earth only rotates in one direction, which is counter clockwise. Students should be able to see that if they rotate Earth counter clockwise (i.e., backwards), it causes the clock to move backwards in time. Teacher Guide: Cycles in the Sky Page 2 of Discovery Communications, LLC

3 In the second part of Earth and Sun, students first click through diagrams and animations to see that a year is determined by how long it takes for a planet to complete one orbit/revolution around the sun. In the activity, students choose to compare one complete revolution of Mercury, Venus, Earth, or Mars with what happens to the other planets during the same time period. The activity shows the length of the chosen planet s year in Earth years and Earth days. Expect to spend some time discussing the concept of Earth years and Earth days with your students as you examine the length of years on Mercury, Venus, and Mars. Elementary students are able to understand that it takes less time for Mercury or Venus to orbit the sun than it takes for Earth. Mars has a larger orbit and must take more time to orbit the sun than it takes for Earth. The challenge for your students is to describe the length of a year for another planet using units based on what happens on Earth. You may want to run the activity as an in class demonstration where you can point out the positions of the planets and discuss the implications of the numbers. Teacher Guide: Cycles in the Sky Page 3 of Discovery Communications, LLC

4 In the third part of Earth and Sun, students examine the position of Earth in its orbit around the sun relative to the beginning of the four seasons in the Northern Hemisphere. Students drag labels for the beginning of the seasons from a one year timeline to one of four possible position of Earth in its orbit. Correct matches result in screens showing larger versions of Earth s tilted axis relative to the sun and text discussing why this combination results in that season beginning in the Northern Hemisphere. Student Worksheets Check In: Earth and Sun The Check In: Earth and Sun worksheet is an excellent way for your students to remain on task and to record useful, relevant information. You should print out the Check In worksheet and provide it to your students before they attempt to do the Fun damental. Have your students read the focus questions next to the notebook icons, as well as the Overview and Think About This sections. There are three places within the Earth and Sun activity where the student needs to record data on the Check In: Earth and Sun worksheet. First, students are asked to draw the location of New York City on a diagram of Earth for four different times. Second, students are asked to record the lengths of one revolution around the sun (in Earth years and Earth days) for Venus, Earth, and Mars. Third, students are asked to fill in the Northern Hemisphere seasons on a diagram of Earth orbiting the sun. In all three cases, recording observations on the Check In worksheet helps students focus their attention on the details of these sometimes easily confused concepts. Teacher Guide: Cycles in the Sky Page 4 of Discovery Communications, LLC

5 Check Out: Earth and Sun Here are examples of possible student responses to the questions on the Check Out: Earth and Sun worksheet: 1. What is Earth s axis? Earth s axis is an imaginary line running through the North and South Poles. Earth spins or rotates on its axis. 2. Is the half of Earth where it s nighttime facing toward the sun or away from the sun? The half of Earth facing away from the sun is the half where it is night. 3. Let s say that it s noon right now where you live. Where on Earth do you think it s midnight? It would be midnight on the other side of Earth, exactly opposite from where I am now. 4. Look at your Check In sheet for the locations of New York City at different times. Based on those locations, which direction do you think Earth rotates: clockwise or counter clockwise? Explain. Earth rotates counter clockwise. The location of New York City moves clockwise going from midnight to 3 a.m. to 6 a.m. to noon. 5. What is a year? A year is the length of time it takes for a planet to complete one orbit around the sun. 6. How long (in Earth days) is a year on Earth? How long is a year on Venus? A year on Earth is about 365 days. A year on Venus is 225 Earth days long. 7. Why is a year on Venus shorter than a year on Earth? Venus has less distance to travel in its orbit around the sun. The orbit of Venus is a smaller circle. 8. At the beginning of summer in the Northern Hemisphere, is Earth s northern axis tipped toward the sun or away from the sun? Earth s northern axis is tipped toward the sun when summer begins in the Northern Hemisphere. 9. At the beginning of summer in the Northern Hemisphere, what season is beginning in the Southern Hemisphere? For the Southern Hemisphere, the southern axis is tipped away from the sun at the same time the northern axis is tipped toward the sun. This is the beginning of winter for the Southern Hemisphere. Moon Phases The second part of the Cycles in the Sky Fun damental is called Moon Phases. In this part, students do activities designed to familiarize them with the following content objectives: The moon orbits Earth. The time it takes for the moon to complete one orbit around Earth is 28 days. When seen from Earth, the moon seems to change shape depending on where it is in its orbit. The changing shapes of the moon are called moon or lunar phases and occur in a regular pattern or cycle. Teacher Guide: Cycles in the Sky Page 5 of Discovery Communications, LLC

6 In Moon Phases, students examine the cause of moon phases and how those phases are perceived during the monthly calendar. After looking at introductory animations and screens describing the cause of moon phases, the students proceed to the moon phases activity. In the activity, students fill in calendars for two months with the moon phases observed each day. As the students click through the days of the calendar, a small version of the moon s phase is placed into that day s square in the calendar. A large version of the moon s phase for that day is visible to the right of the calendars. Students can move their cursor over the moon phase key squares to see each moon phase highlighted on the completed part of the calendars. Student Worksheets Check In: Moon Phases The Check In: Moon Phases worksheet is an excellent way for your students to remain on task and to record useful, relevant information. You should print out the Check In worksheet and provide it to your students before they attempt to do the Fun damental. Have your students read the focus questions next to the notebook icons, as well as the Overview and Think About This sections. The Check In worksheet gives students two blank calendars corresponding to the October and November 2007 calendars in the moon phases activity. Students are asked to use these blank calendars to draw pictures of the moon phases they observe in the activity. Students should also make notes as to which days are new moons and full moons. Students will use these calendars to count the days between phases. Teacher Guide: Cycles in the Sky Page 6 of Discovery Communications, LLC

7 Check Out: Moon Phases Here are examples of possible student responses to the questions on the Check Out: Moon Phases worksheet: 1. How many days were there between the October 2007 full moon and the November 2007 full moon? There were 28 days between the two full moons. 2. How many days were there between the October 2007 new moon and the November 2007 new moon? There were 28 days between the two new moons. 3. The moon phase is determined by where the moon is in its orbit around Earth. How long does it take for the moon to complete one orbit around Earth? It must take 28 days for the moon to complete an orbit around Earth. 4. How many days are there between a quarter moon and the closest full or new moon? It is seven days between quarter moons and the closest full or new moon. 5. If you see a quarter moon where the right side of the moon is lit, would you expect that the moon will soon be full or new? Explain. The moon will be full in about 7 days after you see a quarter moon where the right side of the moon is lit. When you see a quarter moon with the left side lit, the moon is moving toward the new moon phase. 6. Is it possible to have two full moons in one month? If so, how does that happen? A full moon happens every 28 days. A month usually has 30 or 31 days. If you have a full moon in the first two or three days of the month, there should be another full moon at the very end of the month. In the Classroom As a Teacher Demonstration Using a teaching station computer with projection device, you can use the Fun damental to demonstrate basic principles to the entire class. For example, use the animations in the Earth and Sun activity to start a class discussion about the difference between rotation and revolution. Take class time to use the Earth rotation activity to discuss how rotation and the relative positions of Earth and the sun affect time. This is a hard concept for students and one you may want to cover as a group. Distribute the Check In worksheet before any demonstration and use it to guide student participation. When you finish, pass out the Check Out worksheet and ask students to work in pairs as they complete it. With Small Groups Students can also use the Fun damental in small groups. Have the groups complete the Check In and Check Out sheets as a team. When they finish, have each group summarize its findings in a chart in the front of the room. When all groups have finished the Teacher Guide: Cycles in the Sky Page 7 of Discovery Communications, LLC

8 activities, have the class discuss the chart. Then review the answers to the Check Out sheet. Students Working Alone or in Pairs If students work alone or in pairs with the Fun damental, make sure that they have the Check In worksheets and that they understand how the Fun damental works. You might introduce the topics, such as rotation and revolution, with the entire class before individuals begin their work at the computer. When students finish each part of the Fundamental, have them complete the appropriate Check Out sheet. Tell them ahead of time that they can use their Check In worksheets to do that. Teacher Guide: Cycles in the Sky Page 8 of Discovery Communications, LLC