Lots of attention has been paid to the Mayan calendar lately, but the Mayans actually had many scientific achievements, including astronomy, agriculture, and this week's activity, sundials. Even Max Murphy could handle this one!
This guest post was written by one of my very favorite people, Laura Cotts. Laura has taught math, physics, and astronomy courses and labs at Southern Utah University and gave me my very first job as a TA. (Aww!) But my favorite thing Laura does is an amazing array of science activities and demonstrations each year at a local children's jubilee. Take it away, Laura, and thank you!
What if we had no clocks and no compasses?
We could use the sun to help us tell time and
to find directions!
We have heard that the sun rises in the
east and sets in the west. But does this mean EXACTLY east and
west? And does the sun ALWAYS rise in the same place?
This is a project you can do several
times during the year. The most interesting ones to compare are done in
December and June, with one more in either September or March.
Here's what you'll need to do to make your sundial:
1.
Get a large piece of cardboard or foam board and glue a golf tee, flat
side down, near the center.
2. Pick a sunny Saturday or holiday, for you will
want to visit your board about once an hour, all day long. Find a place that will be in the sun the whole day and tape your
board down so it won't blow away, and so it will always be sitting the same
way.
3. Starting early in the morning, go out
and look at the shadow of your golf tee. How long is it?
In which direction is it pointing? Draw a line along the shadow, to its
very end, and beside it write the time. Pay attention to the
location of the sun.
4. Visit your board about once
every hour and draw a line along the shadow. Has
the shadow changed? If so,
how?
Where is the sun?
5. At the end of the day you will
have many shadow lines. What pattern do they make? How did they
change? When was your shadow line the shortest?
The longest? Can you think why?
If your board stayed in the same
place, could it help you tell the time on another day? You have made a very
simple sundial!
Did your
changing shadows sweep along a curve?
Could this be why our round clocks and watches run
"clockwise"?
If you set the board out a month or two
later, will the shadows match your times again, or will there be a
change?
The shadows come from the
sun--will the sun have changed its
path?
Try it!
June
It will be the most fun to try this
activity again in June.
- Do you think the picture will be the same as
December or March?
- How are your June shadows
different from the December shadows?
- How would a March
pattern differ from either? What has caused the changes?
- Does the sun always
rise and set in the same places? What evidence do you have?
- Can the shadow patterns tell us about the different paths
that the sun traces across the sky?
Sundials
The sundial you have made would only tell
fairly accurate time for a few weeks.
As the seasons change the sun's path changes.
Sundials use the shadow of a stick,
called a gnomon. To make a more accurate sundial, the
gnomon should be at an angle that matches your latitude.
Directions for a simple sundial can be
found
here. This sundial will tell
time most accurately for a mid latitude in March and September.
For more activities with the sun and the
seasons, visit
here or
here. For very complete information on sundials try the
British Sundial Society.
Thank you, Laura! I told you she was wonderful. We'd love to have your questions or comments below!