Seasons and Shadows
Grade Level:
5th
Prepared By:
Total Time Required:
4-6 periods (50 minute each), approximate
Larry Braile, Jenny Daugherty, Helen McNally, Inez Hua, Jenniffer
Dickensheets, Pam Stamm, and Melissa Colonis
Lesson Objectives:
Students will be able to:
1. Explain the tilt, orbit, shape, and motions of the Earth (rotation and revolution) and their
relationship to the reasons for the seasons and variable heating of the Earth.
2. Describe the variations in the length of day throughout the year by graphing the length of
day (from sunset to sunrise) for different latitudes.
3. Design a prototype shade for a picnic table to maximize shade throughout the year given
a scale diagram and specific dimensions.
Indiana Standards:
Content Specific:
 Science 5.2.2 (Physical Science)
Observe and use pictures to record how the sun appears to move across the sky in the
same general way every day but rises and sets in different places as the seasons change.
 Science 5.2.3 (Physical Science)
In monthly intervals, observe and draw the length and direction of shadows cast by the
sun at several chosen times during the day. Use the recorded data as evidence to explain
how those shadows were affected by the relative position of the earth and sun.
1
Concepts and Vocabulary
Science Concepts / Vocabulary:
Term
Defined by a scientist or engineer
Tilt of
Earth’s
axis of
rotation
Rotation of
Earth
Orbit
Plane of
the ecliptic
Scale
Sun angle
(above
horizon)
Solstice
Equinox
Tilt of
Earth’s
axis of
rotation
Rotation of
Earth
The angle between the Earth’s axis of rotation and
a line perpendicular to the plane of the ecliptic;
varies from 22.1 and 24.5 degrees and currently is
about 23.4 degrees.
The rotation (spinning) of the Earth around its
axis. The axis currently points approximately to
the North Star (Polaris; within about 0.7 degrees.
When viewed from above the North pole, the
Earth rotates to the East (counter clockwise).
The gravitationally curved path of an object
around a point in space. Orbiting is also called
revolution. Planetary orbits are generally
elliptical.
A plane described by the Earth’s orbit around the
Sun.
The ratio of a dimension (such as length) of a map,
diagram or physical model to the corresponding
actual measurement (on the Earth or on an object).
Scale is often written as 1:100 (or other number)
meaning that the model (map or diagram) is 100
times smaller than the actual object (on Earth or
size of object).
The angle of the Sun above the horizon at any
time.
When the Sun is highest in the sky as viewed from
the N or S pole. Also, the dates when this occurs –
approximately June 21 and December 21.
Time when nighttime hours are equal at all
locations on Earth. Also, approximately March 21
and September 21.
The angle between the Earth’s axis of rotation and
a line perpendicular to the plane of the ecliptic;
varies from 22.1 and 24.5 degrees and currently is
about 23.4 degrees.
The rotation (spinning) of the Earth around its
axis. The axis currently points approximately to
the North Star (Polaris; within about 0.7 degrees.
When viewed from above the North pole, the
Earth rotates to the East (counter clockwise).
Defined by a 5th grade
student
The angle or tilt.
The spinning of the Earth on
its axis, like the spinning of a
top.
The path that a planet takes
as it goes around the Sun.
A plane described by the
Earth’s orbit around the Sun.
The relative size of an object
(3-D object, geographic area,
etc.) compared to the size of
a model.
The angle of the Sun above
the horizon at any time.
“Beginning of summer or
winter season.”
“Beginning of spring or fall
season.”
The angle or tilt.
The spinning of the Earth on
its axis, like the spinning of a
top.
Equipment, Materials, and Tools
List the quantities of all materials and equipment needed:
Tools/Equipment
Materials
Scissors
Styrofoam blocks or clay
3” styrofoam sphere
X-acto knife
Toothpicks
Print template for 3-D building model
Small saw
Plastic straws
Print template for latitude marks
Electric lamp socket and Fine tip felt pen
Print template for N and S American
light bulb (60 watt)
continents
Metric rulers, protractors Bamboo skewers
30 cm dowels (or equivalent)
Flashlights
Glue
Flat Sticks
Tape
Card Stock
Styrofoam Plates
String
Clay
Poster Board
Foam Board
Pipe cleaner
Science Content
Outline of Activities and Lessons
 Introduction/Overview – The reasons for seasons is an important science concept
involving the movements of the Earth around the Sun and the tilt of the Earth’s rotational
axis. Concepts related to seasons are difficult (see Private Universe video in Web
Resources, below) because they require 3-D visualization of the objects and the motions.
The model Sun and Earth and activities presented here represent an effective approach
that enhances visualization, utilizes inquiry, and promotes understanding of the causes
and effects of seasons on Earth. The models really work because students can see the
variations in solar heating through the annual Earth orbit, and the effect of tilt of the axis
of rotation; and, students can manipulate the model to discover and test effects and
hypotheses.

Demonstrations with the model to develop understanding of rotation and revolution,
heating of the atmosphere and Earth’s surface as a function of latitude, the effect of tilt,
and the reasons for seasons. Exploring shadows that are related to Sun angle (height of
the Sun above the horizon at any time of day or season) aids in understanding of the
variations in Sun angle, variable heating of the Earth caused by seasons and the latitude
effect (spherical shape of the Earth).

Length of day and average monthly temperature data at selected latitudes provide practice
with graphing and helps illustrate effects of seasons – data from Internet, mini-lessons
on adding and subtracting times, graphing and comparing the results.

Science background and construction and use of the model. Constructing the tabletop Sun
and Earth models (construct before beginning Seasons and Shadows activity) and
background information.

Extending the design task – can we design a more effective awning (or other approach) to
make the passive solar energy saving more efficient for any day of the year and time of
the day.

Resources and references.

Student work pages.

Example graphs.

Engineering design task: Design an awning or shade for a picnic table using Sun angle
data.

Extension activities: Implement passive solar (energy conservation; heating and cooling)
by designing an awning for south-facing windows of a building, using Sun angle data.
Lesson Plan #1
Guiding Question – How does the Earth move in relation to the Sun
(rotation and revolution)??
Time: One 50 minute class period (plus teacher time to construct the Sun-Earth model)
1. Initial discussion
Ask the students about:
1. What is different with our weather, length of day, and position of the Sun in the sky
during summer and winter?
2. What happens during spring and fall?
3. Are these changes the same no matter where we are on Earth?
4. What happens in the southern hemisphere?
As a follow-up to the discussion of Sun angle, discuss shadows. Many 5th grade students
have probably experienced the “draw the shadow of a fellow student” activity in which the
shadow is drawn at three times during the day – morning, noontime and mid afternoon.
1. What is the relationship between the length of a shadow and the Sun angle (height of
the Sun above the horizon)?
2. Sun angle changes during the day. Does it also change with the seasons?
3. Is it the same at every location (latitude) on Earth?
Ask the students to describe what causes the seasons?
Discuss the main topics in the science background (below) – 3-D visualization and scale,
Earth’s rotation, tilt (Earth’s north rotational axis is pointed toward the North Star) and orbit
(revolution).
2. Initial demonstrations with the Sun-Earth Model
Use the physical model in the following demonstrations and explorations (see Figure 10, left,
in the science background section – the light bulb is placed at the middle of a table, the Earth
is placed about 30-40 cm away and moved in a circle around the light bulb to simulate the
Earth’s orbit; the North arrow on the base of the Earth model always points in the same
direction; the height of the center of the light bulb and the center of the Earth model should
be the same – this can be adjusted by adjusting the length of the straw or by sliding a book or
sheets of paper under one of the models; turn off all lights and shade windows if possible so
that the light from the model Sun is the only light in the room).
1) Earth’s tilt (inclination of the axis of rotation) – note the 23 degree tilt of the Earth’s axis.
Also show the daily rotation of the Earth; counterclockwise when viewed from above the
North polar axis of rotation (North Pole). Note that this rotation will occur continuously
365 times during one Earth orbit although we will not be able to continuously show the
rotation during demonstration of the yearly orbit.
2) Axis of rotation points to Polaris (the North Star in the constellation Ursa Minor) – see
Figures 6 and 7 in the science background section, below, and web animations listed in
the resources section, below.
3) Demonstrate rotation and revolution (also counterclockwise) of the Earth around the Sun
(determine which direction is North in your classroom and always keep the Earth
oriented so that the tilted axis of the Earth is inclined toward the North).
4) Introduce the concept of seasons related to the position of the tilted Earth in its orbit.
5) Illustrate position of the Earth during winter, spring, summer, and fall in the northern
hemisphere. Note the lighting of the polar regions during the seasons and the angle of the
Sun’s rays that impact the Earth in the different seasons and at different latitudes.
Discuss Solstice and Equinox. Show that similar seasons exist in the southern
hemisphere but at opposite times as compared to the northern hemisphere.
6) Use the demonstration in Figure 1 to illustrate why the solar heating of the atmosphere
and the Earth’s surface is reduced at high latitudes (both N and S of the equator) and how
this effect is amplified by the tilt of the Earth and resulting seasons. This is one of the
main concepts of the reasons for seasons – near the equator, the Sun is always “high in
the sky” (overhead) so the energy in the Sun’s rays travels through the atmosphere and
hits the surface of the Earth in a nearly perpendicular direction. However, at high
latitudes (both North and South), the energy in the Sun’s rays hit the Earth at a low angle
so that the energy is spread out over a larger area resulting in less heating of the surface
of the Earth and the Earth’s atmosphere. See Figures 1 and 2 in the Design Activity 1,
below, for illustrations of Sun angle at different latitudes for summer and winter.
Figure 1. Use a hole punch to put a hole into two index cards. Mount the cards vertically (use
Styrofoam block and paper clip, as shown, or clay, for base). Left – position the hole such that
the lighted region is over the 23 degrees N latitude line for the Earth model in northern
hemisphere summer position. Right – next, position the hole so that the lighted region is over the
60 degrees N latitude line for the Earth model in northern hemisphere summer position. Note
that the lighted area is now an ellipse with a significantly larger area (less solar energy hitting
the Earth and atmosphere per unit area). Be sure that the punched hole to lighted are distance
is the same for both demonstrations. The effect on area of the lighted region is even greater for
more northern latitudes (for the Earth model in northern hemisphere summer position).
7) You can illustrate this concept with another effective demonstration using a flashlight.
Shine a flashlight directly at a flat surface (table, floor or wall). Hold the flashlight about
30 cm from the flat surface. Note that the lighted area is approximately circular. Explain
that the light in that circular area represents a fixed amount of energy (from the battery
and the bulb of the flashlight). Then, shine the same flashlight at the surface so that the
angle of the flashlight is about 45 degrees or smaller relative to the flat surface. Be sure
that the distance from the flashlight to the surface (measured along the raypaths from the
center of the flashlight to the surface) is the same as you used previously, so that the
difference in lighting will not be primarily due to a difference in distance. Note that the
lighted area is now an elliptical shape and is larger, so the same amount of energy is
spread out over a larger area, representing less light or heating of the surface per unit
area.
Lesson Plan #2
Guiding Question – How does the Earth move in relation to the Sun
(rotation and revolution) and what is the cause of seasons? (continued)
Time: one 50 minute class session
Procedures / Steps:
1. Review the information and main concepts of the previous lesson and ask students some
questions to determine how much they understood and remember about the Earth’s motions
relative to the Sun and the Earth’s inclination as a cause of seasons.
2. Science background (continued) – Repeat the modeling (using the Sun-Earth model) of the
differences in the angle of approach of the Sun’s rays during daylight hours for the northern
hemisphere at different times of the year and further explore the variable heating related to
latitude (because the Earth is a sphere), the variations caused by the tilt angle, and the effect
on length of day.
1) Encourage the students to manipulate the model and to describe what is happening
(position of Earth with respect to the Sun; show rotation and revolution; What season is
it? What part of the Earth has Sun’s rays hitting the Earth at a high angle [“high Sun
angle”] during much of the daylight hours? What part of the Earth has Sun’s rays hitting
the Earth at a low angle [“low Sun angle”] during much of the day?)
2) Illustrate the position of the Earth during winter, spring, summer, and fall in the northern
hemisphere. Show that similar seasons exist in the southern hemisphere but at opposite
times of the year as compared to the northern hemisphere.
3) Demonstrate that the seasonal variations change depending on latitude. For example in
the tropical regions (near the equator), seasons do exist but the Sun is “high in the sky”
during much of the day throughout the year and the length of day does not change
markedly. However, in the polar regions (greater than about 50 degrees latitude, both N
and S), the Sun is relatively “high in the sky” only during summer (for that hemisphere)
and is very “low in the sky” (or may not even rise above the horizon for latitudes above
63 degrees, N and S) in daylight hours during winter. In addition, the length of day
varies greatly with season in the polar regions so that there can be up to 24 hours of
daylight in summertime in polar regions and as few as zero hours of daylight in
wintertime in the polar regions.
4) Discuss Sun angle (for summer and winter solstice, northern hemisphere) for different
latitudes as illustrated in Figures 1 and 2 in the Design Activity 1. Note the variation of
angles of approach of the Sun’s rays and angle of the Sun above the horizon for different
latitudes and for summer and winter solstice. These angles are also listed in Table 1 in
the Design Activity 1. We will use these same latitudes and angles in the engineering
design activity.
5) Finally, place the model Earth sphere on the 90 degree base (no tilt of the Earth’s axis of
rotation). Demonstrate (and allow the students to explore) rotation and revolution. What
is the effect on seasons, and on length of day? Will there still be differences in angle of
the Sun’s rays and heating of the atmosphere and the Earth’s surface with latitude? Will
there be differences between the northern and southern hemispheres?
6) If your students have not done the draw the shadow of another student activity
(http://www.cgtp.duke.edu/~plesser/outreach/kenan/Activity%204%20Shadow%20Traci
ng.pdf), you could do the activity (or describe and demonstrate it in the classroom) so
that the students understand the relationship of Sun angle and length of shadows. Sun
angle changes throughout the day due to Earth’s rotation. To illustrate Sun angle and
shadows over seasons and for different latitudes, we will consider only the noontime
(maximum Sun angle for the day) Sun angle. Sun angle is illustrated in Figure 2.
Shadow length for a given Sun angle is illustrated in Figure 3. With a model building,
we can simulate any Sun angle using a flashlight and protractor as shown in Figure 3 and
the photos in Figure 5.
Figure 2. Illustration of the Angle of the Sun above the horizon for an observer at any location
on Earth. The angle of the Sun (As) will depend on the observer’s latitude (as well as time of
day). In this illustration, the time of day is approximately noon and the Sun is at its maximum
angle for this day of the year. Note that the angle and the perspective (frame of reference) of the
observer will be different than another observer at a different latitude, such as in the southern
hemisphere, near the equator or nearer to the pole.
Figure 3. Illustration of the relationship between angle of the Sun (above the horizon) and
length of a shadow. Note that as the Sun angle (As) is larger, the shadow is shorter, and as the
Sun angle is smaller, the shadow is longer.
7) Shadows at different latitudes (and for different times of the day) can be demonstrated
with the Sun-Earth model using short (~2 cm) toothpicks inserted into the Styrofoam so
that the angle with the surface of the sphere is 90 degrees. Examples of shadows for the
Sun-Earth model are shown in Figure 11 (in the science background section) and in
Figure 3 in Design Activity 1.
Lesson Plan #3
Design Challenge – Shading a Picnic Table
Time: one-two 50 minute class sessions
Procedures / Steps:
1. Review the information and main concepts of the previous lesson and ask students some
questions to determine how much they understood and remember about the Earth’s motions
relative to the Sun and the Earth’s inclination as a cause of seasons.
2. Science background (continued) – Repeat the modeling (using the Sun-Earth model) of the
differences in the angle of approach of the Sun’s rays during daylight hours for the northern
hemisphere at different times of the year and further explore the variable heating related to
latitude (because the Earth is a sphere), the variations caused by the tilt angle, and the effect
on length of day.
3. Break up the class into teams – one team for each latitude and Sun Angle; see Table 1 in the
Design Activity brief. Provide each of the six teams with copies of the Design Activity brief
and related materials and work pages. A copy of the picnic table drawing can be used as
their model to design a shade structure or awning.
4. The shading of the picnic table for various Sun angles can be tested using the flashlight held
at different angles above the horizontal (horizon). Each team should try to design a shade for
their latitude that meets the goals and constraints of the design challenge. Use the flashlight
to illuminate (as the Sun’s rays would) the shaded table and to measure the angle of the light
relative to the vertical direction as illustrated in Figure 5.
5. Have each team share their shade information and designs with the entire class and
demonstrate that they work (according to the design goals) for their latitude.
Figure 5. Left – Use of a flashlight to illuminate a model. Right – The angle of the flashlight (90
- As ) can be measured and the flashlight angle adjusted using a protractor taped to the
flashlight as shown here.
Design Activity 1
Shading a Picnic Table
The company that you work for has contracts with cities for construction of facilities for city
parks. Recently, several picnic tables were constructed and installed in city parks at several
locations around the world (cities at different latitudes). These cities have now asked your
company to design structures to provide shade for some of these tables (sometimes it is
uncomfortably hot to sit in the Sun at the table). The structure must provide shade during
noontime (maximum Sun angle for that location) in both summer and winter (summer and winter
solstice). You will have to use what you have learned about seasons, shadows and Sun angles to
create an effective and affordable structure.
During this lesson you will:
 Design a structure that will provide the picnic table (lunch area, table and benches) with
shade. A scale model drawing of the picnic table is shown below.
 Use the information from your understanding of seasons, shadows and Sun angles (see
Table 1) to create an effective model as a prototype of the actual structure that will be
constructed.
 Test your model using a flashlight to imitate the Sun’s rays.
Design Requirements:
 The structure should shade the entire picnic table and bench area at noontime at your
latitude for both summer and winter solstice (see Sun angles for your latitude in Table 1),
but should allow some Sun at early and late hours of the day (low Sun angles).
 The structure should be at least 2 meters tall (20 centimeters for your model).
 Must stand up on its own, but can be fixed (permanent location) or moveable depending
on season.
 Must be affordable (low cost). The list below shows the materials available and the cost
of each item.
Materials (most can be cut to size) and prices
30 cm dowels (or equivalent)
Flat Sticks
Tape
Card Stock
Styrofoam Plates
String
Clay
Poster Board
Foam Board
Pipe cleaner
$1.00 each
$0.50 each
Free
$1.00 per sheet
$2.00 each
$0.05 per cm
$3.00 per strip
$0.05 per square cm
$0.10 per square cm
$0.05 each
North
1 meter
2 meters
Picnic
Table
Figure 1. Illustration of Sun’s rays (angle of approach and angle above the horizon) for
different latitudes at approximately noon on summer solstice for the northern hemisphere. The N
or S in parentheses next to the angle of approach (also the angle above the horizon) indicates
that the viewer is looking up and to the north (N) or south (S) to view the Sun.
Figure 2. Illustration of Sun’s rays (angle of approach and angle above the horizon) for
different latitudes at approximately noon on winter solstice for the northern hemisphere. The N
or S in parentheses next to the angle of approach (also the angle above the horizon) indicates
that the viewer is looking up and to the north (N) or south (S) to view the Sun.
Table 1. Summer and winter maximum Sun angle at selected latitudes.
Maximum Sun Angle (~Noon,
Maximum Sun Angle (~Noon,
June 21, Summer Solstice,
December 21, Winter Solstice,
Latitude
Northern Hemisphere (and
Northern Hemisphere (and
direction of view to horizon*)
direction of view to horizon*)
o
o
- **
75 N
38 (S)
60o N
53o (S)
7o (S)
40o N
73o (S)
27o (S)
23o N***
90o (Z)
44o (S)
20o N
87o (N)
47o (S)
0o (Equator)
67o (N)
67o (S)
23o S***
44o (N)
90o (Z)
40o S
27o (N)
73o (N)
* (S) = At this latitude, data and time, view to the Sun is toward the South (above horizon).
* (N) = At this latitude, data and time, view to the Sun is toward the North (above horizon).
* (Z) = At this latitude, data and time, view to the Sun is directly overhead (at the Zenith).
** No Sun, 24 hours of night.
*** 23o N and S latitudes not shown on Figures.
Figure 3. Noontime (local time) shadows from toothpicks (like very tall buildings) at 40o S, 0o
(equator), 23o N, 40o N, and 60o N in northern hemisphere summer (left) and northern
hemisphere winter (right). Note that there is no shadow at 23o N in the northern hemisphere in
summer indicating that the Sun is directly overhead. Also, the shadows lengthen in higher
latitudes and are affected by the seasons.
Assessment
Students should be able to use the Sun-Earth model to demonstrate their understanding of
seasons and be able to describe the variable heating and seasonal effects for any latitude and at
any season.
The student teams should be asked to explain their engineering design and how and why it
works. They should have accurately accounted for the latitude (and therefore Sun angle) and
seasonal effects as listed in the Design Challenge.
Science background and construction and use of the Sun-Earth Model
1. Science background – provides some information about the movements of the Earth relative
to the Sun (rotation and revolution) and the tilt of the Earth.
a. Three-dimensional visualization and scale – The Sun, Earth and solar system are threedimensional (3-D) objects and their movements are in a 3-D space. We are very familiar
with 3-D objects (desks, buildings, people, etc.). However, when we attempt to view or
represent 3-D objects that are very large (or very small), they are commonly represented
in two-dimensional diagrams or images. Physical models provide an additional approach
to visualizing 3-D objects. When using physical models, it is important to consider the
scale of the models. In any case, the visualization of 3-D objects is an important skill for
science, engineering and mathematics.
The scale of a diagram or a physical model is defined as the model size (length, width,
etc.) of the object divided by the actual size of the object. It is usually written as 1:X
(“one to X”) where X is the scale factor. For example, for the solar system, we could use
a scale model with a 1:1 billion scale to represent the sizes of the Sun and the planets. As
seen in Table 1, this representation results in a scale model that is about 6 km in length –
a scale that could be used (and has been) for an outdoor model but is not possible for a
classroom, or a tabletop model. The difficulty with choosing a scale for a classroom-size
solar system model for illustration of seasons on Earth, is that a single, consistent scale
factor isn’t practical for application to both the diameters and the distances of the model.
For example, if we chose a larger scale factor, say 1 to 1,000 billion (the same as 1:1
trillion), the Sun-Earth distance in our model would be almost 1.5 m, but the diameters of
the model Sun and Earth would be 0.139 cm and 0.00127 cm, respectively. At this scale,
which would work for the Sun-Earth distance (~1.5 m), the model Sun would be a tiny
sphere of only a little more than a millimeter in diameter, and the model Earth would be
smaller than a tiny grain of sand. So, the model that we will use will not be “to scale.”
Table 1. Scale of the solar system – distances and diameters (actual and at 1:1 billion scale)
Scaled Distance
Scaled
Sun or
Distance From
Diameter
From Sun (m)
Diameter (cm)
Planet
Sun (km)
(km)
(1:1 Billion)
(1:1 Billion)
Sun
0
0
1,392,000
139
Mercury
57,900,000
57.9
4,880
0.49
Venus
108,200,000
108.2
12,100
1.21
Earth
149,600,000
149.6
12,756
1.27
(Earth's Moon) 400,000 (from Earth)
0.4 (from Earth)
3,476
0.35
Mars
227,900,000
227.9
6,794
0.68
Jupiter
778,300,000
778.3
143,000
14.3
Saturn
1,427,000,000
1427
120,000
12.0
Uranus
2,871,000,000
2871
51,800
5.18
Neptune
4,497,000,000
4497
49,528
4.95
Pluto*
5,914,000,000
5914
2,330
0.23
* Pluto is classified as a dwarf planet. We include it here, in the list of planets, as a
representative of the many dwarf planets that have now been discovered in the solar system.
b. The orbit and rotational axis of the Earth – the Earth orbits the Sun in an elliptical
orbit (nearly circular). The plane described by the elliptical orbit is called the plane of
the ecliptic. For our model Sun-Earth system, we can visualize this plane as being
parallel to the tabletop. An excellent animation illustrating the orbits of the planets can
be found at http://www.gunn.co.nz/astrotour (one can easily control the speed, the size of
the planets and zoom in to emphasize the Earth or inner planets). The Earth’s axis of
rotation is not perpendicular to this plane. It is tilted or inclined about 23 degrees from a
line perpendicular to the plane of the ecliptic. This angle slowly changes over thousands
of years from about 21.5 to 24.5 degrees. However, at present the angle is approximately
23 degrees and the north polar axis of rotation if “fixed” in space such that it points
almost exactly to the North Star (Polaris, in the constellation Ursa Minor – the “Little
Dipper.” This constant tilt can be verified by observing the position of Polaris in the
night sky from any location in the northern hemisphere as illustrated in the time-lapse
photo shown in Figure 6. Further, because Polaris is so far from Earth and the north
polar axis points almost exactly toward Polaris, one can use the angle of Polaris above the
horizon (looking north in the northern hemisphere) to determine one’s latitude (Figure 7)
and this property hold for any location, time and season for the northern hemisphere.
YouTube videos can also be used to illustrate the apparent movement of stars around
Polaris due to the fixed orientation of the Earth’s axis of rotation
(http://www.youtube.com/watch?v=XTTDWhky9HY,
http://www.youtube.com/watch?v=6_8EcKvg3h4).
Figure 6. Time-lapse (several hours) photograph from Earth (northern hemisphere)
showing position of Polaris (“the North star”) and other stars that appear to circle
Polaris (actually due to Earth’s rotation) http://en.wikipedia.org/wiki/Circumpolar_star.
Figure 7. Illustration of the tilt of the axis of rotation of the Earth. Currently, the North polar
axis points toward Polaris (within 0.7 degrees). Note that at a latitude of 40 degrees North, the
angle of Polaris above the horizon is 40 degrees (see triangle AOC which demonstrates that the
angle above the horizon is equal to the latitude. This relationship exists for all location in the
Northern hemisphere.
c. Construct one or more models of the Sun and Earth – For teacher-led demonstrations
and explorations by student groups, construct one or more Sun and Earth models. The
models are not to scale, but work well to illustrate the movements of the Earth (revolution
and rotation), the Sun’s rays hitting Earth at different time of the year, the effect of
latitude on energy received from the Sun, and the effect of the tilt of the Earth. The
model elements are illustrated in Figures 8, 9 and 10, and the captions include
information for construction and use of the models in demonstrations and student
exploration.
Figure 8. Materials for model Sun and Earth. Left – Electric light socket and 60 watt decorator
bulb. Right – Plastic straws, “corn cob” sticks or skewers, 3 inch diameter, smooth surface
Styrofoam ball.
Figure 9. Left – Model Earth with 23 degree tilt of axis of rotation. Right – Styrofoam base,
“corn cob” stick and straw with no tilt – straw is perpendicular to the base.
Figure 10. Tabletop Sun-Earth Model. Left - Sun consists of a 60 watt spherical (decorator,
frosted) light bulb in an electric light bulb socket (available at K-Mart, Walmart, Target,
hardware stores). The Sun-Earth distance on the tabletop is about 30-40 cm. Place the model
Sun in the middle of the table and move the Earth model around the Sun in a circular,
counterclockwise, orbit. Center and Right – Close up of the model Earth showing 23 degree tilt
toward the N – to the right in both views (be sure the center of bulb and the center of Earth
model are at the same height above the table top – adjust by changing the length of the straw or
place a book or other material under either the Sun or the Earth models). Note that the North
arrow is kept in the same direction at all locations (such as pointing to the North wall of your
classroom) in the orbit of the Earth around the Sun. Center – Sunlight (from model Sun light
bulb) for summer in the northern hemisphere (Earth model to the left of the Sun model). Right –
Sunlight (from model Sun light bulb) for winter in the northern hemisphere (Earth model to the
right of the Sun model).
Figure 11. Left - Map of North and South America for transferring to Earth sphere. Right –
Earth model (3 inch diameter smooth, Styrofoam sphere) mounted on Styrofoam block
(approximately 4 x 4 x 1 inch; or other material such as clay). Plastic straw is glued in hole
(drilled or “punched” with wooden “corn cob” skewer at 23 degree angle from vertical, tilted
toward “N”) on base. Short wooden “corn cob” skewers are punched into Styrofoam ball to
form N and S polar axis of rotation. A small piece of a toothpick, inserted perpendicular to the
surface of the sphere can be used to show shadows and represent “frame of reference” for a
viewer at any latitude. Lines of latitude (see Figure 12) are also drawn on sphere. The rotation
of the Earth (counter-clockwise when viewed from above N pole) can also be illustrated (for
viewing day, night, sunrise and sunset; lighted region at different times during the day at any
location for the given obit position and season; shadows; and frame of reference) by turning the
wood skewer at the top of the model Earth. Also, construct one base for the Earth model with no
tilt (see Figure 9) – a vertical hole so that the straw is 90 degrees from the base (pointing
straight up). This base will be used to contrast the tilted Earth cause of seasons with what would
happen if there was no tilt.
Figure 12. Template for marking lines of latitude on the model Earth sphere. Cut out along
dashed edge and along bold line. Place on model Earth sphere so that top edge of cut out
semicircle is at the North pole and bottom edge of semicircle is a the South pole and make a dot
at each intersection of a latitude line (60, 40, 23, 0, -23, -40, -60), then rotate the earth model a
small amount and repeat until dots are all the way around the sphere. Connect the dots with
smooth lines with a fine point marker pen to complete the selected lines of latitude. Label the
latitudes on the sphere.
Figure 13. Example of positioning of protractor for awning length design task (Work Page 2 for
Design Activity 2). Left – Summer Sun angle for 40 degrees N latitude, 73 degrees from the
horizontal (17 degrees from the vertical). Right – Winter Sun angle for 40 degrees N latitude, 27
degrees from the horizontal (63 degrees from the vertical).
Lesson Extensions and Resources
Resources:
Ashmann, Scott; A Sun-Earth-Moon Activity to Develop Understanding of Lunar Phases and
Frames of Reference, Science Scope, v. 35, February, 2012, 32-44.
Braile, S.J., A Journey through the Solar System, Project SPICA: A Teacher Resource to
Enhance Astronomy Education, p. 53-57, Kendall/Hunt Publishing Co., Dubuque, 1994.
(Available from Amazon.com: http://www.amazon.com/Project-Spica-Resource-AstronomyEducation/dp/0840393660/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1332514160&sr=1-1-catcorr)
Gould, Alan; Willard, Carolyn; and Pompea, Stephen; The Real Reasons for Seasons – SunEarth Connections: Unraveling Misconceptions about the Earth and Sun, GEMS, Lawrence Hall
of Science, University of California, Berkeley, 2001, 124 pages. (Available from Amazon.com:
http://www.amazon.com/Lawrence-Hall-Of-ScienceReasons/dp/B004430I6U/ref=sr_1_2?ie=UTF8&qid=1332512186&sr=8-2)
Wiebke, Heidi; Rogers, Meridith; and Nargund-Joshi, Vanashri; Sizing up the Solar System.
Science and Children, v. 48, September, 2011, 36-41.
Wilcox, Jesse; and Kruse, Jerrid; Springing into Inquiry, Science Scope, v. 35, February, 2012,
26-31.
Web Resources:
The Private Universe video that examines science misconceptions, including the reasons for
seasons, is available at: http://learner.org/resources/series28.html?pop=yes&pid=9# Click on the
"VoD" icon - may need multiple tries, must allow pop-ups.
Scale model of the solar system:
http://members.efn.org/~jack_v/teaching.html
http://www.exploratorium.edu/ronh/solar_system/
“Reasons for Seasons” – Earth and Sun orbit, tilt and Sun angle animations:
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0408/es0408page01
.cfm?chapter_no=04
http://www.mathsisfun.com/earth-orbit.html
Khan Academy (http://www.khanacademy.org/) videos (cosmology and astronomy):
Seasons are not caused by closeness of Earth to the Sun:
http://www.khanacademy.org/science/cosmology-and-astronomy/v/seasons-aren-t-dictated-bycloseness-to-sun
How Earth’s tilt causes seasons: http://www.khanacademy.org/science/cosmology-andastronomy/v/how-earth-s-tilt-causes-seasons
http://www.cgtp.duke.edu/~plesser/outreach/kenan/Activity%204%20Shadow%20Tracing.pdf