The ancients carefully tracked the movement of the Sun over the course
of the year because so much of their lives and livelihood depended upon
keeping track of the seasons. Early civilizations needed to know when
to plant their crops, when to harvest them, and when to prepare for
winter. Failure to do any of these activities at the right time would
mean disaster for the entire village. Religious celebrations, often
tied to these agricultural events, were also extremely important to
early peoples. Being able to predict when these events would occur was
a crucial ability, and served as the basis for the very earliest of
civilizations.
Few of us today notice the movement of the Sun. Even many adults are
unaware that the Sun is lower in the sky during the winter than it is
during the summer. The seasons we experience are a direct result of
this fact (the tilt of the Earth’s axis is what makes the Sun
appear lower in the sky; the resulting shorter days and less direct
sunlight mean less solar heating and therefore colder temperatures), yet
many believe that the seasons arise because the Earth is closer to the
Sun in the summertime (the Earth is actually closest to the Sun near the
first of January – mid-winter for the Northern Hemisphere).
Unfortunately, the apparent movement of the Sun and the changes it
causes are so slow that it is difficult to convey this effect to
students so that they understand it at an intuitive level. In order to
truly understand the motion of the Sun, it is necessary to go back to
the techniques of the ancients.
One of the most fun ways to do this is to build a schoolyard sundial.
This sundial does not require any calculations or measurements, hence is
appropriate for all ages, even the very youngest students. Instead,
this sundial is created the same way the ancients created theirs: by
marking the shadow cast by the Sun as it changes position over the
course of the year. By making and recording observations over the
course of the year, students will gain this intuitive understanding of
the Sun’s motion that has been slowly disappearing from our
technological society.
Grade Levels: K-8
Time Frame: Year-long project
Educational:
Students will gain an intuitive understanding about the apparent motion
of the Sun in the sky over the course of a day and a year, and will
better understand what causes seasons on Earth.
Real World Application:
Students will participate in a project that has both a science as well
as an art component. While learning about science, they can take pride
in making their school a more beautiful and interesting place to be.
National Science Education Standards:
Standard D: Earth in the Solar System
The procedure for this activity is very simple. Choose a prominent
vertical object in your school yard that casts an easily-followed
shadow. A flagpole works well, but a basketball goal or other
playground equipment can work as well. The sundial will serve as both
a clock and a calendar. Over the course of a single day, have your
students mark the position of the shadow fairly close to the central
pole exactly on the stroke of every hour. The idea is to have hour
markers that the shadow will pass through no matter what time of year it
is. Place a marker labeled with the time. These markers should be
something semi-permanent and not likely to be knocked over or erased by
weather or children playing. Depending upon your circumstances, you
could use:
- Concrete blocks
- Buckets filled with sand or concrete
- Stakes or posts driven into the ground
- Paint (for concrete or asphalt surfaces)
Next, your students will place markers at the tip of the shadow at a
specific time and at regular intervals throughout the year. Noon is the
traditional time to mark the shadow, but you could do it at any time, so
long as the same time is used for each observation. Times closer to noon
will generally work better than early morning or late afternoon because
the shadow length will be shortest at this time.
Over the course of the year, the length of the shadow will vary as the
Sun reaches higher and lower points in the sky. Make sure each marker
is labeled with the date. You will want to make an observation once a
week or once a month (depending on the amount of space you have
available and the kind of markers you use), but you may also want to
mark significant dates on the school calendar, such as holiday breaks,
graduation, and the end of the school year. Astronomical events such as
the equinoxes and solstices are good choices, too. Birthdays and other
anniversaries could be marked and commemorated as well – the
possibilities are endless! It is very important, however, that the
“standard” marks occur at regular intervals, as they form
the calendar portion of the sundial.
As some practical advice, look for an object that has a great deal of
room on its south side (in the Northern Hemisphere; north side in the
Southern Hemisphere). A marking area that is easily visible, but is out
of the main flow of traffic, is ideal. While schoolyard sundials can
be made from any existing equipment you have outside your school, this
project can be turned into a very attractive art project as well,
incorporating sculpture and paintings for the markers. You will find
students will take a great interest in using their creativity in
designing such a project, and will have more pride in their school and
in themselves as a result!
The key to this project is dedication and commitment. The students must
be ready to mark the shadow on the specific time and date. Test your
students’ understanding of the solar motion by asking them to
predict where the shadow will be on certain dates or at certain times.
Ask them when the shadow will shortest (both during the day and during
the year). When will it be the longest? Additionally, you could
evaluate the artistry and creativity that they bring to the project, if
you choose to add that aspect to the activity.
- Instead of marking positions of the shadow on certain dates, you
could record the date when the shadow touches prominent objects in the
schoolyard, such as planters, other playground equipment, etc.
- Set up a web-enabled camera to broadcast real-time pictures of your
sundial across the Internet.
- Take photos of the sundial at different times and dates and post
them inside the classroom.
