Science Curriculum Preview Committee Clarification of Learning Results

Curriculum Organizing Questions	What is an axis? How does the earth move on its axis? How long does one rotation take? How does the earth move around the sun? How long does one revolution take? Is the angle of the sunlight always the same?
Elaboration	This is a difficult concept to understand at any age. Students shoud have opportunities to experiment with light to determine how angle can affect the warming effects. They can use a heat lamp and measure temperature variations when the light is directed at different angles. Once they understand how this works, models (globes of the earth and strong flashlights to represent the sun) can be used to show how the angle of sunlight hitting the earth changes as the earth revolves around the sun.
Specific Ideas	The earth's one-year revolution around the sun, because of the tilt of the earth's axis, changes how directly sunlight falls on one part or another of the earth. This difference in heating different parts of the earth's surface produces seasonal variations in climate. SFAA, p. 43
Developmental & Instructional Implications	A common belief at all ages is that distance of the earth from the sun is the cause of the seasons. Many children believed the earth is nearer the sun in summer than in the winter and that this accounts for hotter weather in summer. Driver, p. 173 Most students are told by teachers what causes the seasons and the phases of the moon, and they read about them without understanding. In trying to understand the seasons, students have difficulties regarding geometry and solar radiation. Students need direct experience with light and surfaces -- shadows, reflection, and warming effects at different angles. Benchmarks, p. 66
Examples	Have students use models of earth and sun.  JourneyNorth's Mystery Classes can reinforce this concept.(needs web site)