Students propose an explanation for night and day and view a model of Earth’s rotation.
Essential Question:
What causes the day–night cycle?
Activity Overview:
This activity introduces the explanation for some of the observations students made
on the apparent motion of the Sun throughout the day. They investigate one characteristic of planetary motion—Earth’s rotation around its axis. Confronting a variety of preconceptions about the cause of daylight length, they analyze observations that contradict or support each explanation. You present a demonstration of the scientificexplanation for Earth’s day–night cycle and for the apparent movement of the Sun from east to west during the day.
Tuesday
Activity 74: As Earth Rotates
Objective:
Students complete a reading about Earth’s rotation, day-night cycle, and time.
Essential Question:
What effect does the rotation of Earth have on the way people measure time?
Activity Overview:
Students read a summary of the effects of Earth’s rotation around its axis. They review the historical use of sun sticks and sundials to tell time and are introduced to the concept of time zones.
Quiz
Wednesday
Activity 75: Sunlight and Seasons
Objective:
Students graph data on the length of daylight and highest angle of the Sun for the 21st of each month and correlate changes in the Sun’s position and day length with the seasons.
Essential Question:
What do you observe about the length of daylight and the position of the Sun in the sky during the course of a year?
Activity Overview:
Students consider the decrease in the size of the shadow of Tyler’s tree from spring to summer. They graph and analyze data on length of daylight and the angle of the Sun during the course of a year and relate the patterns they observe to seasonal changes. They discover the correlation between daylight length and the position of the Sun in the sky, and relate these variables to the seasons. This awareness of seasonal patterns in the Sun’s position and apparent motion prepares them for a discussion of the reasons behind these changes in Activities 76–78.
Thursday
Activity 76: A Year Seen From Space
Objective:
Students use observations of Earth’s position relative to the Sun over a year to develop an explanation of the basis for Earth’s year and seasons.
Essential Question:
What causes the yearly cycle of the seasons on Earth?
Activity Overview:
Students use a computer model to investigate the effects of the revolution of Earth around the Sun and Earth’s tilt on seasonal changes in the Northern Hemisphere. Students use the simulation to observe Earth as it revolves around the Sun and to record data for different seasons. They use their observations to develop an explanation for the cause of Earth’s year and seasons.
Analyzing Data Assessment
Friday
Activity 77: Explaining the Seasons
Objective:
Students explore the effects of direct and indirect sunlight on the solar energy striking Earth’s surface.They learn that the directness of the Sun’s rays is one of two factors that result in hotter summers.
Essential Question:
Why does the tilt of Earth lead to different surface temperatures?
Activity Overview:
Students continue to explore the effect of Earth’s tilt in determining the seasons. Two teacher demonstrations show that light is more concentrated, or less spread out, when it strikes a surface at a 90° angle than at any other angle. Using a photovoltaic cell, students explore how the angle of the sunlight striking it affects the amount of solar energy the cell absorbs.
