Date: 1992

Grade: 4, 5, 6

Subject(s):

• Science/Astronomy

1. Explain the workings of the solar system.
2. Construct a model of the solar system.
3. Diagram the phases of the moon.

At the end of week six you will be planning a trip to some place in space. You will work with 3 to 4 other students. You will be asked to justify your choice of destination. You are to plan your trip taking into account as many factors as possible. Begin thinking of places in space that you would like to go.

Note to Teacher:

The assessment of the Online Discovery - Astronomy unit will be the completion of an authentic task whereby groups of 4 to 5 students will plan a trip to a location in space. This task will take 2 to 3 class periods to complete. See week 6 for details.

Introduction

Earth

Everything in space moves. It goes at its own speed and direction. This includes the planet on which we live, Earth. Spinning is one way that the planets, sun, and stars move. They spin around an axis. On Earth the ends of the axis are known as the North Pole and the South Pole. These aren't real poles stuck through the earth but it is easier to think of the movement if you imagine the earth as a ball spinning around a pole.

Rotation is spinning around the poles. No matter where you are on earth you are moving on the rotating planet. This rotation gives us our daytime and nighttime. One full rotation is a 24 hour day.

The earth also spins around the sun. This is called revolution. Revolve means to orbit around a central point. The earth's orbit is the path it takes around the sun. One full orbit around the sun is a revolution. The earth takes one year or about 365 days to make one revolution.

The other planets also revolve around the sun. Some of the other planets have smaller orbits than the earth because they are closer to the sun. Others have larger orbits because they are farther from the sun. The length of a year on another planet is different from the length of a year on earth.

Have you noticed that the sun seems to shine at a different angle at the same time of day in the winter than in the summer? This is because the earth's axis (our imaginary poles) is not straight up and down. The earth is tilted. In the summer the northern part of the earth gets more direct sunlight than the southern part. In the winter the southern part of the earth gets more direct sunlight than the northern part.

Assignment:

On pages 20-23 of your Student Resource Book add the following words to your astronomical vocabulary dictionary: axis, rotation, revolution, and orbit. Remember to give their pronunciations, definitions, and your definitions.

Student Investigation: Why There is Day and Night?

Procedure:

1. Obtain a flashlight, a knitting needle, a clay ball or styrofoam ball. In what way do you think the ball is like the earth?
2. Push the knitting needle through the ball. Darken the room. Let the flashlight shine on the ball. In what way is the flashlight like the sun?
3. Stick a pin in the ball to represent the place where you live. Turn the globe slowly to the sunlight side.

1. Which side of the ball is having night?
2. Which side is having day?
3. What tells you that the sun is always shining somewhere on the earth?
4. Using the ball, how would you make night come to the place you live?
5. What time of day is it when your pin is on the same side as the sun?
6. What time of day is it when the pin is away from the sun?
7. What would happen if the earth didn't turn?

The Moon

Our moon revolves around the earth. It is really shaped like a ball but its shape seems to change from night to night. These different shapes are called phases. When the moon appears as a full circle this phase is called a full moon. As the moon continues to revolve around the earth, a part of the dark side of the moon faces the earth. Each day more of the dark side faces the earth so we see less and less of the moon. The moon slowly changes from a circle to a half circle. When people see the half circles they are seeing half of the lighted side and half of the dark side of the moon. This phase is called the half moon.

After a while, only the dark side of the moon faces the earth. We can't see the moon in the sky. This phase of the moon is called the new moon. The moon is just beginning a new set of phases. The changes from a full moon, to a new moon, and back to a full moon take 291/3 days. This is the length of time it takes the moon to revolve around the earth once.

Class Activity: Observing the Moon During the Day

Note to the teacher: To schedule this activity, check a newspaper or calendar to find out the date of the next full moon. Schedule this activity to begin three or four days after the full moon. During this part of the cycle, the moon will be visible most of the day. It is preferable to schedule the observation during the morning when there is a better view of the full moon. You don't need to observe at the same time every day. You will want to go outdoors and find the moon before the first observation session to make sure it is not obscured by trees or buildings. If it is cloudy, begin on the first clear day.

Materials:

• For the class:
  1. 2 sheets of white butcher paper
  2. a felt tipped marker
  3. roll of masking tape

• For the student:
  1. pencil
  2. Student Resource Book
  3. calculator (optional)

You will begin to observe the moon for a month. Gather in a spot where you can see the sun and the moon. Describe the shape of the moon, and notice if the curved part faces toward or away from the sun. Then draw the sun and the moon just as they appear in the sky on page 34 of your Student Resource Book. Remember to date these sketches.

Measure the distance between the sun and the moon in fists. To do this hold one hand over the sun to shield your eyes. (You could also stand in the shadow of a building so the sun is just barely hidden.) Make the other hand into a fist, and hold your arm out straight. Hold it so the wide part points toward the sun. Move your fist toward the moon one fist width at a time. Count as you go. With practice you will become consistent. Measure three or four times until you get about the same number. Write the number of fists next to the drawing of the moon. Put these drawings into your Student Resource Book.

Go outdoors every other day to make a new drawing of the sun and moon. Each drawing should show how the sun and moon appear in the sky, the distance between them in fists, and the date. If it is cloudy for a day or two, go out on the next clear day. After each session discuss how the moon has changed shape, and its distance from the sun. Was the curved part of the moon facing toward or away from the sun?

After about ten days the moon will no longer be visible in the morning. Begin to summarize your data. Place a large sheet of butcher paper on the wall. For the first day's observations, tally the observations for the number of fists between the sun and the moon. Average these responses.

Draw the sun and the moon as they appeared on that date. Write the date and the average number of fists next to the moon. For each day's observations add one more drawing of the moon, the date, and the number of fists.

Try to describe the pattern and observations.