APRIL is the cruelest month, breeding
Lilacs out of the dead land, mixing
Memory and desire, stirring
Dull roots with spring rain.
Winter kept us warm, covering
Earth in forgetful snow, feeding
A little life with dried tubers. –T.S. Eliot
Why do we have different seasons? Why is it cold in the winter and warm in the
summer? What factors are at play? The Earth tilts 23.5 degrees. How might this affect
the seasons? In this lab, we will investigate these things and try to understand why we
have our 4 seasons.
Seasons Simulator
http://astro.unl.edu/naap/motion1/animations/seasons_ecliptic.swf
Daylight Hours Explorer
http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html
Problem:
How does the tilt of the Earth and its position in its orbit around the Sun affect
the seasons?
Procedure:
1. Write down some of your ideas about why we have seasons.
2. Open the Seasons Simulator and the Daylight Hours Explorer in different tabs.
3. Look in the Seasons Simulator and you will see three windows. In the upper right
hand window, there is a model of the Earth with a tiny person on the surface.
Click on the person and drag it to 40 degrees North latitude (that’s where we are
located). Also, click the box marked labels.
4. Click the start animation button in the lower right hand corner and observe the
Seasons Simulator animation as it goes through the whole year, before logging
any data.
5. Run the animation again, but this time, stop the animation at the correct dates
and record the angle of the sun’s rays in the corresponding boxes. You will do this
for each month.
6. Set the latitude to 40 degrees N. latitude in the Daylight Hours Explorer.
7. Note the hours of sunlight for each date and fill in that information in the correct
box on your data table. Use the same dates as you did for the first set of data
(slide the tab in the upper right).
8. Plot the angle of the Sun’s rays and the hours of sunlight on the correct line
graphs provided in the lab.
9. Notice any trends or patterns, and any correlations between the two graphs.
10.Think about what this information means and discuss it with your partner.
11.Answer the questions.
12.Complete a CER which will include your claim, at least 2 pieces of evidence, and
your reasoning. This will be completed as homework and handed in the day
following the lab.
Data for 40 degrees North Latitude
Date (month/day)
January 20
February 20
March 20
April 22
May 21
June 21
July 22
August 20
September 23
October 21
November 23
December 22
Angle of Sunlight
(Sun’s Altitude)
Hours of daylight
Line Graph of Angle of Sun’s Rays at 40 Deg. N. Latitude
90
80
70
60
Angle
of
Rays
50
40
30
20
10
0
Jan.20 Feb.20 Mar.20 Apr.22 May 21 June 21 July 22 Aug.20 Sept.23 Oct.21 Nov. 23 Dec.22
Date
Line Graph of Hours of Sunlight at 40 Deg. N. Latitude
15
14
13
12
11
10
Hours of
Sunlight
9
8
7
6
5
4
3
2
1
0
Jan.20 Feb.20 Mar.20 Apr.22 May 21 June 21 July 22 Aug.20 Sept.23 Oct.21 Nov. 23 Dec.22
Date
1. Which date has the most hours of sunlight? What is the angle of the Sun’s rays on this date?
A. Is there anything notable about this date? What is this date called?
B. On this date, are the most direct rays of the sun falling on the Tropic of Capricorn, the Tropic of
Cancer, or the Equator?
2. Which date has the least hours of sunlight? What is the angle of the Sun’s rays on this date?
A. Is there anything notable about this date? What is this date called?
B. On this date, are the most direct rays of the sun falling on the Tropic of Capricorn, the Tropic of
Cancer, or the Equator?
3. On what dates are there nearly equal amounts of sunlight and darkness? What are the terms for these
dates?
A. Is there anything notable about these dates? What are these dates called?
B. For each of these dates, are the most direct rays of the sun falling on the Tropic of Capricorn, the
Tropic of Cancer, or the Equator?
4. Now, move your little person to 90 degrees N. latitude (the North Pole) on the Seasons Simulator and
watch the animation. Then set the latitude on the Daylight Hours Explorer to 90 degrees N. latitude. Note
the hours of sunlight and the angle of the sun’s rays. Record your observations.
5. Move your little person to 40 degrees S. latitude on the Seasons Simulator and watch the animation. Then
set the latitude on the Daylight Hours Explorer to 90 degrees S. latitude. Note the hours of sunlight and the
angle of the sun’s rays. Record your observations.
6. Finally, set your little person to 0 degrees (The Equator) on the Seasons Simulator and watch the animation.
Then set the latitude on the Daylight Hours explorer to 90 degrees N. latitude. Note the hours of sunlight
and the angle of the sun’s rays. Record your observations.
7. Why is it coldest at the poles?
8. Why is it warmest nearest the equator?
9. What do you think would happen if the Earth had no tilt? Think a moment and describe what it might be
like in terms of temperature, sunlight and the seasons. What about if the Earth’s axis was pointed directly
at the sun? What would it be like on Earth then?
Vocabulary
Tropic of Cancer –
Tropic of Capricorn –
Equator –
Tilt –
December (Winter) Solstice –
June (Summer) Solstice –
March (Spring or Vernal) Equinox –
September (Autumn) Equinox –
North Pole –
South Pole –