What's Your Slant?
Sun and Shadows:
Have you ever heard the expression, It's been a long day?
So, what makes a day so long? Is everybody's day as long?
Did you ever wonder where the term High Noon came from?
Is everybody's high noon as high?
And why will Randy and Janice be so much colder than we are?
Most of our questions above can be answered
by understanding how our planet and our Sun relate to each other.
The shape of our planet, the way it rotates, and its position
in relation to the Sun all have something to do with our questions.
Our planet is a spherical shape, that is, it is almost round
like a ball. Sunlight radiates to the earth. This radiation
provides light, heat, and other types of electromagnetic energy.
While the sunlight radiates, the earth is moving (revolving)
around the Sun. Earth, while revolving, also rotates on
an axis. The earth's axis is tilted in relationship to the Sun.
(The axis is neither parallel nor perpendicular to the Sun.)
All of these things are major factors in understanding long days,
high noon and why Randy and Janice will be shivering at the South Pole.
II. WATCH OUT!
Never look directly at the Sun.
III. WHAT'S UP?
How does the Earth's rotation, revolution, and tilt effect the angle
of sunlight at different locations?
IV. WHAT DO YOU THINK?
State your prediction and support it with reasons.
VI. JUST DO IT
- manila folder
- different colored pens, pencils, markers or crayons
- 1 toothpick - use the round pointed type (6.5 cm)
- grape-size ball of clay
- directional compass
- Open your folder and with a pen and ruler, draw a line down the
crease on the folder. This will be called the crease line. Label one
end of the crease line "N" to indicate the compass direction of North.
- At the other end of the crease line about 2 cm from the edge, draw
a second line parallel to the long edge and perpendicular to the line
down the crease.
- Place the center of the penny where the two lines cross.
- Take the folder outside and place it on a flat surface. Make sure
this is a place where you can leave the folder undisturbed or determine
a way to mark the location so that you will be able to place the folder
exactly in this same location later. Also make sure that no large objects
such as buildings will block out the Sun during the day (i.e. that there
are few obstructions to the south).
- Use the compass to orient the folder so that the N faces north.
- Take the grape size ball of clay and stick the toothpick through
the center of the clay so that the clay is in the middle of the toothpick.
- Stand the toothpick with one end in the center of the circle where
the lines cross.
- Holding the toothpick vertical, perpendicular to the folder, push
the clay down so that it rests against the folder and supports the
toothpick. Together the folder, toothpick and clay form what will
be called a Shadow Apparatus.
- Every hour, on the hour, for 6 hours, starting at 9 am, use a pen
to trace the length of the toothpick's shadow on the folder (e.g.
- Label the time of day on the shadow.
- Measure and record the length of the shadow. Lift the clay and
measure from the center of the circle where the lines cross to the
end of the shadow.
- Use the protractor to measure the angle between the toothpick's
shadow and the crease line.
VII. SCORE BOARD
- Record the angle on the Scoreboard
- Using the shadow apparatus, repeat steps 9 through 13 for as many
days as possible between December 14 -20, the days that Janice and
Randy are at the Pole. Use a different colored pen for each day's
- Post your Scoreboard data on the web.
Create a table like the one below and record your data.
Your Latitude (if known):__________________
Your Longitude (if known):_________________
Date that the data were taken:_____________
Shadow Length (millimeters)
| || ||
| || ||
VIII. DO YOU SEE WHAT I SEE?
- Describe what has happened to your shadow length during
the course of the day. Why did this happen?
- Describe what has happened to your shadow angle during the course of
Why did this happen?
Also, please submit the results of your experiment to us! As we collect
data from students around the world we'll post the results here.
To contribute your data simply fill in the blanks below
and hit the "Submit" button.
IX. ONE STEP BEYOND
- Compare your data with other locations posted on the web page for
- Are there data sets that match yours? What is the location of those areas?
- Are there data sets that are different than yours? What is the
location of those areas?
- Get a globe or a world map. Mark the various locations for which
there is sun shadow data available on the web page. Now look at the
data for each marked location. Is there a pattern for similar data?
for different data?
X. TWO STEPS BEYOND
To be done after data from different latitudes is posted.
- On the folder that has your sun shadows, create a fish tail design
by drawing lines to connect the ends of the shadows.
- Using posted data, make fish tail designs for latitudes in
continents in the Northern and Southern Hemisphere. Do this by
measuring the shadow lengths and angles for each latitude's data
information on a sheet of paper. Then, connect the ends of the
shadows and label the design with its latitude.
- Arrange the fish tails from largest to smallest. Which latitude's
fish tail came first?
The fish tails can be used to create a model of the earth on a
bulletin board or poster board. Instead of continents on the
earth model, use the fish tails to indicate latitude positions.
CARA's research and education programs are supported in
part by the National Science Foundation under a cooperative
agreement, grant number NSF OPP 89-20223.
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Antarctica. This copyright applies to all web pages and
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Last modified Monday, 04-Dec-2000 16:35:07 CST