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Seasons activity
Explore the causes of the seasons
Kit contents: Globe, 2 golf tees (tape to the globe before class), tape, flashlight
Key concepts:
Science Standards:
Student knows that the tilt of the Earth on its own axis as it rotates and revolves around the Sun causes changes in
season, length of day and energy available (SC.E.1.2.1).
Student knows that a model of something is different from the real thing, but can be used to learn something about
the real thing (SC.H.1.2.5).
Basic Procedure
1.
You’ll need five students for this activity. One student takes the
flashlight and plays the Sun. The other four students will play Earth
during each of the four seasons of the year.
2.
The four season students should evenly space themselves around
the Sun students.
3.
Using the diagram, the season students should pass the globe
around the Sun.
4.
As the Earth makes its orbit around the Sun, make sure the tilt
always remains the same and that the Earth remains in the same
position. For each stop, students should determine what season it
is in each hemisphere.
5.
Repeat the activity, but have students determine the season for
Florida at each of the four positions.
Key Knowledge
Vocabulary
sun - the star at the center of our solar system
rotate - spin on an axis
axis - imaginary line that passes through the North and South Poles
revolve - travel in a path around
orbit - the path taken in a revolution
equator - imaginary line going all the way around Earth halfway between the North and South Poles
Key Concepts
The cycle of day and night occurs because the Earth rotates around its axis.
A year is the length of time it takes the Earth to revolve around the sun. Seasons are caused by the tilt of the Earth's
axis. During the summer, the Northern hemisphere is tilted toward the sun, resulting in more hours of daylight and
more direct sun rays. In the winter, the opposite is true.
The day when the amount of daylight is the greatest is called the summer solstice (June 20 or 21, in the Northern
Hemisphere). The day when the amount of daylight is least is the winter solstice (Dec 21 or 22). The equinoxes are
when the hours of daylight and darkness are about equal, and the sun rises in the east and set in the west
(September 22 or 23, March 20 or 21).
Seasons Data
Key: Daylight Hours Across the Globe
Time is indicated as number of hours (h) and number of minutes (m)
City
1–Jan 1–Feb 1–Mar 1–Apr
1–May
1–Jun 1–Jul 1–Aug 1–Sep 1–Oct 1–Nov 1–Dec
Miami, Florida
10h
34m
11h
00m
12h
18m
12h
25m
13h
07m
14h
18m
14h
24m
14h
00m
12h
40m
12h
35m
11h
11m
Nome, Alaska
4h
53m
7h
02m
10h
03m
13h
35m
17h
36m
21h
17m
22h
09m
18h
04m
15h
16m
11h
19m
8h
5h 31m
36m
Singapore
12h
04m
12h
04m
12h
05m
12h
07m
12h
50m
12h
51m
12h
11m
12h
10m
12h
08m
12h
06m
12h
04m
Seattle, Washington
9h
12m
10h
15m
11h
04m
13h
31m
15h
18m
15h
42m
16h
34m
15h
36m
13h
22m
11h
41m
10h
9h 24m
39m
Vostok, Antarctica
24h
00m
24h
00m
19h
01m
14h
40m
0h
00m
0h
00m
0h
00m
0h
00m
7h
14m
15h
14m
24h
00m
24h
00m
Brisbane, Australia
14h
31m
13h
22m
13h
20m
12h
29m
11h
04m
11h
11m
11h
05m
11h
29m
11h
32m
12h
20m
13h
49m
14h
24m
Punta Arenas, Chile
17h
32m
15h
27m
13h
33m
11h
22m
10h
03m
8h
32m
8h
17m
9h
27m
11h
22m
12h
46m
14h
53m
16h
33m
Cape Town, South
Africa
15h
03m
13h
45m
13h
20m
12h
24m
11h
26m
10h
03m
10h
36m
11h
07m
11h
23m
12h
24m
14h
08m
14h
14m
Nairobi, Kenya
12h
12m
12h
10m
12h
08m
12h
06m
12h
04m
12h
03m
12h
03m
12h
04m
12h
05m
12h
07m
12h
09m
12h
09m
Axial tilt of major celestial bodies
Moon
Object Axial tilt (°)
11h
20m
12h
03m
1.5424
Jupiter
3.13
Pluto
119.61
26.73
Eris
unknown
Mercury ~0.01
Mars
25.19
Saturn
Venus
177.36
Ceres
~4
Uranus 97.77
Earth
23.439
Pallas
~60
Neptune 28.32
Monthly Normal and Record High and Low Temperatures for Pensacola
Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Rec High °F
80
82
86
96
98
101
106
107
98
92
86
81
Norm High °F 61.2
64.4
70.2
76.2
83.4
89.0
90.7
90.1
87.0
79.3
70.3
63.4
Norm Low °F
42.7
45.4
51.7
57.6
65.8
72.1
74.5
74.2
70.4
59.6
51.1
44.7
Rec Low °F
5
15
22
33
48
56
61
60
43
32
25
11
Rainfall
(inches/mm)
5.3/135 4.7/119 6.4/163 3.9/99 4.4/112 6.4/163 8.0/203 6.9/175 5.8/147 4.1/104 4.5/114 4.0/102
Science Background
Why does the Earth tilt?
No one knows why the Earth's axis is tilted by 23.5 degrees. Some astronomers think that about 5 billion years ago,
when the Earth was still very young, it was struck by a Mars-sized planet. This colossal impact could have tipped our
planet over. Whatever the reason, it's a good thing - if the Earth did not tilt, countries near the poles would be cold
and dark all year round. If it tilted too much, the seasons would be very extreme – like on the planet Uranus. Here the
winter lasts for 42 years in total darkness!
Using the sun to determine the size of the Earth
In 200 B.C. Eratosthenes was the head librarian in Alexandria, Egypt. He received a letter from a friend in Syene,
which lies on the Tropic of Cancer. His friend passed on the remarkable fact that on the summer solstice the sun
would climb to be directly overhead at midday. The sun would shine to the bottoms of the deepest wells, and the
buildings would have no shadows.
In Alexandria, the sun was not directly overhead on the summer solstice. It did not shine to the bottoms of wells and a
vertical stick had a shadow. How could this be? Eratosthenes figured that if the earth were flat, shadows would be the
same everywhere. So the surface must be curved: a sphere.
The next year he went out and measured the midday shadow of a long vertical pole on the summer solstice in
Alexandria and it measured 7.2 degrees. There are 360 degrees in a circle. He divided 360 by 7.2 and found that 7.2
degrees was about one-fiftieth of a circle. He then had beatimist, surveyors trained to walk with equal steps, measure
the distance between Syene and Alexandria. Multiplying the distance between Syene and Alexandria by 50, his
calculated the circumference of the earth to be 24,662 miles. This is only 200 miles off of the actual circumference of
the earth
Temperature and seasons
Summer solstice is called, in temperate climates, the first day of summer. The reason for the delay between
maximum heating and maximum heat (temperature) is that it takes time to warm up the ground and water.
Differences between temperatures at different places at the same latitude are related to nearby geographic features,
particularly water, which exerts a moderating effect, slowly taking up heat and slowly releasing it.
Length of day vs angle of sunlight
There are two contributors to the warmth of the seasons, the length of the day and the angle that the sunlight hits the
Earth. The rays of the summer sun, high in the sky, arrive at a steep angle and heat the land much more than those
of the winter sun, which hit at a shallow angle. At steep angles, sunlight hits the ground more directly, concentrating
the radiation in a narrower spot. At shallow angles, that same amount of radiation is spread further, resulting in less
heating at any given spot. Although the length of the day is an important factor in explaining why summers are hot
and winter cold, the angle of sunlight is probably more important. In the arctic summer, even though the sun shines
24 hours a day, it produces only moderate warmth, because it skims around the horizon and its light arrives at a low
angle.
Greek mythology
Persephone is the daughter of Zeus and Demeter, goddess of the harvest. Persephone was such a beautiful young
woman that everyone loved her, even Hades wanted her for himself. One day, when she was collecting flowers on
the plain of Enna, the earth suddenly opened and Hades rose up from the gap and abducted her. None but Zeus, and
the all-seeing sun, Helios, had noticed it.
Broken-hearted, Demeter wandered the earth, looking for her daughter until Helios revealed what had happened.
Demeter was so angry that she withdrew herself in loneliness, and the earth ceased to be fertile. Knowing this could
not continue much longer, Zeus sent Hermes down to Hades to make him release Persephone. Hades grudgingly
agreed, but before she went back he gave Persephone a pomegranate (or the seeds of a pomegranate, according to
some sources). When she later ate of it, it bound her to underworld forever and she had to stay there one-third of the
year. The other months she stayed with her mother. When Persephone was in Hades, Demeter refused to let
anything grow and winter began.
The Zodiac
The signs of the Zodiac represent the constellations that lie in the plane of the ecliptic that the Earth travels as it
revolves around the sun. If we could turn off the sun in its fixed position, then the constellation behind it determines
the particular Zodiac "sign" of that time of year. The shapes and order of the constellations are available at
http://www.jb.man.ac.uk/distance/strobel/nakedeye/nakedeya_files/zodiac.gif.
Script Idea
What we are going to talk about today -- seasons!
What are seasons? While we might think there is a "correct" answer to this question, in actuality it is a vague
question. In addition to winter, spring, summer and fall, here we also have hurricane season. Tropical climates
typically have a wet and a dry season.
People have paid attention to seasons for as long as we have known. They just haven't understood why. Many
cultures have had myths about the reason for the seasons. Share the story of Persephone.
Even with this myth, many Greeks still continued making scientific observations. Share the story of Eratosthenes.
We have some materials here for modeling the seasons. Using the globe and the flashlight, each group should come
up with a model that accounts for the seasons, the annual cycle, and the daily cycle. Explain that the Earth is tilted
slightly with respect to the Earth-Sun axis. Pass out the materials and let the groups create their model.
Ask the groups as you go around what season they are showing, what ideas they have on why it is a particular
season. Make sure that they can demonstrate the equinoxes and solstices.
Attract the students' attention. Ask them what ideas they had about what causes the seasons. They should note the
length of sunlight as well as the angle of sunlight. To demonstrate the angle of sunlight effect, shine the flashlight on
a piece of graph paper (or the chalkboard) at different angles. Explain that the flashlight is giving off constant energy,
but at different angles that energy is distributed over different amounts of surface area. Point out that the arctic
regions get 24 hours of sunlight during the solstices, but you wouldn't expect them to be hotter than Florida.
Ask the students if they know about astrology, what sign they are. Explain the history of the zodiac. What might be
the purpose of the zodiac? To mark the months. Present poster boards (or big post-it paper) with the zodiacs on
them. Ask the students where you should place them so that they can be incorporated into the sun-Earth model. They
should be placed on the walls around the room. Ask the students to demonstrate using their model why there are
some stars that you see in summer and some in winter.
Other challenge questions might be: Why do you see Venus at evening or dawn but never at night but you see Mars,
Saturn, and Jupiter at night? Where is the moon in the model; can they account for moon phases? Where is the North
Star in our model? What would the seasons be on a planet with a different tilt?
Collect the globe and flashlights. Pass out the solar motion demonstrator materials (precut) and glue. Instruct the
students on the assembly.
Explain to the students that the solar motion demonstrator is a way of determining when and where the sun will
appear to rise and set. Stress that it is not the sun travelling in the sky but rather the Earth turning. (By holding the
area that says "Months" steady and turning the rest, they can more accurately reflect this.) Tell the students that we
live at approximately 30 degrees north. What can they tell about the sunrise and sunset during different months?
What about at different latitudes?
Refer to the idea of solstice and equinox. Explain when they fall. What can the students tell about them using their
demonstrator? They should find that the sun is at its highest point in June, that all latitudes have sunrise and sunset
in the due east and west at the equinox, that the North Pole doesn't have its sun set at the summer solstice, among
other things.
Present the daylight hours table. Ask the students to predict the approximate latitudes of the different cities.
Ask the students why July and August are hotter than June when the longest day is June.
Alternate Ideas
Make a Solar Motion Demonstrator. Note that Pensacola is at 30 degrees N. Consider precutting the materials with
an xacto knife to save time. Printing the materials on cardstock is adequate for strength.
Signs of the Zodiac