Exploring the Astronomy of the Seasons
4: Heating Up
Direct and Indirect Sunlight
#4 of Reasons for Seasons)
By conducting simulations, students explore the effects of direct
and indirect sunlight on heating of the Earth.
If you conducted activity 1, ask, What did our shadow studies
reveal about the angle of the sun at different times of year?
What else do you think the angle of the sun affects as it
hits the Earth’s surface?
Document students’ ideas and have them identify ones they
can explore through direct observations or experiments. If they
mention the Earth’s temperature, ask them to explain their
thinking. Ask, How could we test this idea? Let students
pursue their ideas, or suggest the following.
Part 1: 1 period; Part 2: 1 period
2 pie tins painted black, graph paper, flashlights
two pie tins black. Set both tins out in the sun. Ask, How could
we simulate the sun's rays hitting one tin at an angle (indirectly)?
They might, for instance, place one lying flat so that the sun shines
directly on it and stand the other one up vertically in a piece
of clay so it receives only angled rays.
students to predict which they think will absorb more heat and explain
why they think so. After 10 minutes, have them feel both surfaces.
If possible, place a thermometer in the face of each tin and measure
the temperature difference.
Connections — Journaling and Discussion Questions
differences did you notice?
could you explain them?
do your findings help you better understand the seasons?
Spark students’ thinking about why direct sunlight provides
more heat than angled (indirect) sunlight.
small groups two pieces of graph paper and a flashlight. Ask them
to lay one piece of paper on a surface horizontally to represent
the Earth, shine the flashlight directly on it from about two feet
away, and trace the outline of the light.
students to change the angle of the second piece graph paper (for
instance, by lifting it up a bit) to simulate the Earth’s
tilt in relation to the sun. They should place a notebook or other
hard surface behind it, again shine the light on it from the same
location, and trace the outline of the light.
and Discussion Questions
do you notice about the amount of sunlight hitting each piece of
season do you suppose each piece represents and why?
do these findings, along with your investigations in part one, help
you better understand the seasons?
(When our hemisphere is tipped away from the sun during the winter,
the angled sunlight is spread over a greater area, so it not very
intense and doesn’t provide as much heat as when it hits us
more directly during the summer.)