Models have many different functions. In this chapter we used drawings and physical models to help explain aspects of the earth-sun-moon system. Scientists often use models to make and test predictions. Models may consist of a series of equations or lines of computer code. In this chapter we learned that the earth-sun-moon system is responsible for tides. Questions 1. Scientists can use computer models to predict the times and heights of tides well into the future.
2. Who would find this information useful? Can you think of any other scientific predictions that provide useful information in everyday life?
Chapter Summary
1. The sun is the star at the centre of our solar system. 2. Earth is one of eight planets in our solar system and the moon is a natural satellite of Earth.
3. Day and night are caused by the rotation of Earth around its own axis. 4. Seasons result from the tilt of Earth’s axis. 5. The moon appears bright because it reflects the light of the sun. 6. As the relative position of the moon changes, the amount of illuminated moon you are able to see changes. These changes are called phases of the moon.
7. The lunar cycle is the time it takes the moon to complete a full orbit of Earth. 8. A waxing moon is when the illuminated area of the moon is increasing. 9. A waning moon is when the illuminated area of the moon is decreasing.
10. Tides are caused by the attractive forces of the gravitational fields of the sun and moon. 11. A solar eclipse occurs when the moon blocks out the light of the sun from Earth. 12. A lunar eclipse occurs when Earth casts a shadow on the surface of the moon.
Questions and Exercises K C
Key Concepts Rewrite the following sentences in your copybook and fill in the blanks. Night and day occur on Earth because Earth rotates on its ______________________ . Seasons occur on Earth because its axis is ______________________ . When the moon is waxing the illuminated area appears to be ___________________ . When the moon is waning the illuminated area appears to be ___________________ .
