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Schoolyard Sundial

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

Objectives

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

What You Do

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!

Assessment

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.

Extensions
  • 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.

corner corner
  What You Need
  • Tall vertical object in a sunny area
  • Semi-permanent objects to serve as time and date markers

Optional Materials:

  • Weather-resistant web-enabled camera
  • Photographic camera
 
corner corner

Resources
  • Maestro, Betsy. (1999). The story of clocks and calendars: Marking a millennium. New York, NY: Lothrop, Lee, & Shepard Books.
Vocabulary
  • Solstice
  • Equinox
Credits

ASU Mars Education Program
Keith Watt, M.A., M.S.
Mars Space Flight Facility
Arizona State University
marsed@asu.edu
(480) 965-1788