Overview:
Students explore a model of the earth’s daily rotation and
its annual revolution around the sun. They try to figure out at
which point each season occurs in their part of the world. This
lays the groundwork for understanding the reasons for seasons
and for making sense of Mystery Class clues.
Preparation:
Prepare a simulation of the Earth-Sun system by placing a lamp
on the floor to represent the sun. Use a globe to represent the
earth. It will spin (rotate) on its axis and revolve around the
sun. Cut a star shape out of paper, label it the North Star, and
place it on the board. Orient the North Pole of the globe so it
points toward the star. Finally, place 4 Xs of masking tape on
the floor on each side of the lamp.
Laying
the Groundwork
Ask
a student to find your city or state on the globe and tape a
small paper circle on it. Challenge them to keep an eye on this
location – and the light it receives – as they explore
how the Earth and sun interact!
Exploration
- Discuss
the terms rotation and revolution.
Have a volunteer demonstrate rotation with his or her body
and then with the globe. (You might reveal that spinning
is another word for rotation.) Next, let them know that
the Earth rotates counterclockwise on its axis. Have a volunteer
demonstrate this. Ask students to notice what happens to
the light hitting your globe's school location. Ask, What
do you think each rotation represents? Explain your thinking.
(Each represents a 24-hour day during which every location
has daylight and nighttime.)
- Ask
another volunteer to show how the Earth moves (revolves)
around the sun (also counterclockwise). Explain that the
Xs represent different seasons and that the Earth is not
up and down on its axis, but always tilted (23.5 degrees)
with the North Pole facing the North Star at all times.
As the student walks around the sun slowly to represent
the earth’s revolution, remind him or her to spin
the globe quickly to also represent days passing. Ask, What
do you think one complete revolution represents? (A
year or 365 ¼ days.)
- Invite
a volunteer to stand at one of the Xs and rotate the earth
to show two days coming and going. Have another student
take the globe and move counterclockwise to the next X and
do the same, and so on with each season. Remind them to
keep the North Pole pointing to the North Star as they revolve
around the sun from season to season. As they do so, ask
students to pay close attention to the sun's relationship
to their hometown during each season.
Making
Connections
- Challenge
small groups to discuss which X they think is which season.
You might prompt them to focus on their hometown and discuss
characteristics of each season there: temperature, sunlight,
and so on. They may want to again examine the relationship
between their hometown circle and the lamplight on the globe.
Also share this clue with them: the first days of spring
and fall are called the equinox, which is related
to the word equal.
- Have
each group write a label for each of the four seasons and
place the labels face down on what they think is the appropriate
X. Then season by season, turn over the labels and ask each
group to explain its thinking. Conflicts in labels should
spark fertile discussions! Rather than confirm answers at
this point, you might want to conduct the next couple of
activities and revisit students’ ideas at the end.
Alternatively, you can pass out and discuss the Earth,
Sun, and Seasons drawing.
Assessment
Older
Students: Have students draw diagrams showing the relationship
between the earth and the sun as it would be on the day they
are doing this activity. Then have them sketch North and South
America on their "earth" and place a small x in the
approximate location of their hometown.
Younger Students: Give students this challenge
question: One day, a boy in Massachusetts is going skiing with
his family. What might a girl in Australia be doing?
Related Activities
Digging Deeper
Set up a model of the earth's annual revolution around the sun
in the classroom and keep it active all school year. Put the
sun in the center and create an Earth with the proper tilt.
Mark a pathway the Earth will follow on its 360-degree revolution.
Mark both equinoxes and solstices along the path. Try to make
the model large enough so each week's changes are visible. Once
each week, have students move the earth to its proper position
in relation to the sun.
