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Winds
And
Weather
by Jonas Ramoth and Sidney Stephens
Activity Series 4- Heating the Earth*
| Summary |
In this series of activities, students explore how the angle of sunlight
affects the Earth's temperature and seasons and then apply this understanding
to their local situation. |
| Background |
We live on a moving planet that is heated by the sun. The Earth moves
in two important ways: (1) it rotates on its axis causing day and night
in a 24 hour cycle and: (2) it revolves (or orbits) around the sun in a
365 day annual cycle creating the seasons. Each season has its distinctive
temperature range which influences weather patterns. For example, in summer
when the northern hemisphere is tilted toward the sun, daylight increases
to 13-24 hours and the rays of sunlight shine almost straight down, heating
the ground much more effectively than in winter when the rays hit Earth
at a shallow angle. Together, longer daylight hours and more direct heating
of the Earth create characteristically warm summer days. In winter the opposite
is true. This heating of the Earth drives both winds and the water cycle. |
| Activity 4a
Materials |
Per Group: 5cm diameter Styrofoam ball, turkey skewer,
5cm x 5cm square of wood in which a hole has been drilled at a 24° angle,
socket-type light fixture
|
| Procedure
Gear-up |
1. Ask each student to write down on a piece of paper what they think
causes seasons. After individuals have recorded their ideas, have them
share their ideas with members of their cooperative group. Record the
ideas of the different groups about the cause of seasons. Check things
on which they all agree and circle ideas on which they disagree. Remind
the students that during the following investigations they will want to
watch for data that will support or refute their ideas. During the investigations
you will want to check with students to see how their concepts might be
changing.
|
Explore/
Generalize: |
2. Challenge the students to set up a model of the
Earth and Sun which will explain both seasons and the changing day
length. Tell students
that
the Earth is tilted on its axis approximately 24 ° from vertical.
Give each cooperating group a 5 cm diameter Styrofoam ball that will
be used as a model for the Earth. Have the students insert a
wooden turkey skewer through the center of the ball to mark the model
Earth's axis. Provide each cooperating group with a 5 x 5 cm square of
wood in which a hole the size of the diameter of the turkey skewer has
been drilled. The hole should be drilled at a 24 ° angle. Have the
students put one end of the turkey skewer into the hole. This will keep
the model Earth at the correct tilt.
3. Tell the students that as the Earth revolves around the Sun, the Earth's
northern axis is always pointed toward the Polaris, the North Star. Locate
a spot on the ceiling that will serve as a model North Star. As the students'
construct their model to demonstrate seasons, remind them to keep the
North Pole of the model Earth always pointing towards North Star.
4. Provide each cooperating group with a socket type light fixture that
they will use to simulate the model Sun. Remind the students as they are
working on their models, to rotate the model Earth on the turkey skewer
to see what impact the Earth's position to the Sun has on day length.
(For example, when the model Earth's Northern Hemisphere is tilted toward
the model Sun, the North Pole is illuminated during an entire rotation
of the Earth.) Remind the students to look at the position in which the
direct rays of light from the Sun strike the Northern Hemisphere. At what
position do the rays from the Sun strike the Northern Hemisphere at the
greatest angle? How might the angle at which light strikes a region affect
the temperature of that region?
|
| Activity 4b
Materials |
Per Group - black construction paper, 3 thermometers, books
|
| Procedure
Gear-up |
1. Ask how the angle of sunlight affects the Earth's temperature? At
what time of day is the heat from the Sun's rays the most intense? (At
local solar noon or the time when the sun appears to have reached its
highest point in the sky during the day. It occurs halfway between sunrise
and sunset.) What is your explanation for this observation? During what
time of day does the Sun appear to be directly over head? At what time
of day will rays from the Sun strike us the most directly? At what times
during the day will the rays from the Sun strike us at a slant? (When
light rays strike head-on the heat intensity is much greater than when
the light rays strike at a slant and the light rays are dispersed over
a bigger area spreading out the warmth)
|
| Explore |
2. Have student groups make three black envelopes by folding pieces of
black construction paper into thirds, folding up the bottom end and taping
closed. Insert a thermometer into each black envelope. On a sunny window
sill prop up the envelope clad thermometers at different angles.
Thermometer One: Using a book, prop an envelope-covered thermometer
against the book so that the thermometer faces away from the sun. Sun
light should barely touch the flat part of the envelope.
Thermometer Two: Place the second thermometer in its black envelope
flat on top of a book. The sun should strike the envelope at an angle.
Thermometer Three: Prop the third thermometer in its envelope
against two books. Adjust the envelope so the sun's rays strike it directly.
At the end of five minutes read the temperature on all three thermometers.
|
 |
| Generalize |
3. Which registers the highest temperature? The lowest? How
does the angle at which the Sun's rays strike the envelope affect the temperature
reading? How would this explain why temperatures tend to be warmer around
noon? How would this explain why temperatures in summer tend to be warmer
than temperatures in winter? How would this explain winter temperatures
in the far north are so cold? |
|
Activity 4c:
Materials
|
Per Group: hollow cardboard tube, a flashlight and a piece of cardboard
|
| Procedure
Gear-up: |
1. Ask students how much more area does light at a slant cover than head-on
rays?
|
| Explore |
2. Give each cooperating group a hollow cardboard tube, a flashlight
and a piece of cardboard.
3. Insert the flashlight into one end of the tube. Hold the tube about
four inches directly above the cardboard. Turn on the flash light and
trace around the illuminated area on the cardboard. Now, still hold the
tube four inches from the cardboard but slant the tube so that the light
rays strike the cardboard at an angle. Trace around the illuminated area
made by the slanted light rays.
|
| Generalize |
4. The same amount of light passed through the tube. In which
case did the light cover the bigger area? If the same amount of light is
spread out more over a bigger area, how will this affect the heat absorbed
from the light? |
| Apply/Assess: |
5. During what time of day are rays from the Sun spread out
the most? The least? During what time of the day light hours is the Earth's
surface usually the warmest? Usually the coolest? |
 6. In what season
do the rays from the Sun hit the Earth the most directly? At the greatest slant?
What affect does this have on the Earth's temperature at these times?
7. Around June 21, what part of the Earth gets sunlight head on? Around December
21 ? How does the angle at which light strikes the Northern Hemisphere compare
on March 21 and September 21? How is this likely to affect the temperature of
the Northern Hemisphere at these times of year?
* Adapted from Barr, B. (1994)
Standards
Section I - Observing Locally
Section II - Understanding Wind
Section III - Connecting
Globally
Appendix A - Selawik Weather Information from
Jonas Ramoth
Appendix B - Assessment
Appendix C - Weather Resource
List
Appendix D - Interdisciplinary Integration
Handbook
for Culturally Responsive Science Curriculum by Sidney Stephens
Excerpt: "The information and insights contained in this document will be
of interest to anyone involved in bringing local knowledge to bear in school
curriculum. Drawing upon the efforts of many people over a period of several
years, Sidney Stephens has managed to distill and synthesize the critical ingredients
for making the teaching of science relevant and meaningful in culturally adaptable
ways." |
