Activity 73: A Day on Earth
Students propose an explanation for night and day and view a model of Earth’s rotation.
What causes the day–night cycle?
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 scientific explanation for Earth’s day–night cycle and for the apparent movement of the Sun from east to west during the day.
Activity 74: As Earth Rotates
Students complete a reading about Earth’s rotation, day-night cycle, and time.
What effect does the rotation of Earth have on the way people measure time?
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.
Activity 75: Sunlight and Seasons
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.
What do you observe about the length of daylight and the position of the Sun in the sky during the course of a year?
Students consider the decrease in the size of the shadow of
Activity 76: A Year Seen From Space
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.
What causes the yearly cycle of the seasons on Earth?
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
Activity 77: Explaining the Seasons
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.
Why does the tilt of Earth lead to different surface temperatures?
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.
Last Modified on May 7, 2013