Human Sundial

Human Sundial lesson plan

What does the shadow know? If it’s a shadow across a sundial, it knows the time of day. Experiment with shadows and timekeeping with Crayola Giant Sidewalk Chalk.

  • 1.

    Sundials have been used since ancient times to mark the time. They were even used to check the accuracy of early mechanical clocks. Sundials work because as the Earth rotates around the sun, the sun’s place in the sky changes. Do more research about sundials and their operation.

  • 2.

    You will find that shadows are created by a central stick or triangle set perpendicular to the base plate of a sundial. This "shadow stick" is called a gnomon.

  • 3.

    Ask an adult to help you locate a large, safe outdoor area to draw your human sundial, which will give you an idea of how a sundial works. Make sure it is in full sun.

  • 4.

    Using Crayola Giant Sidewalk Chalk, draw a large circle. Make evenly spaced marks around the outside edge for each hour of the day. Figure out where the center of the circle is located and mark that, too.

  • 5.

    Stand on the center mark in the morning when the sun is out. Ask a classmate to trace where your shadow falls on the sundial. Inside the traced shadow, write the time of day. Keep recording your results throughout the day to see how the shadow moves aroun

  • 6.

    How accurate do you think your sundial is? Why?

Benefits

  • Students research how sundials work and identify different types of sundials.
  • Students create a kinetic experiment to demonstrate the function of a sundial.
  • Students record their color-coded findings on a replica sundial.

Adaptations

  • Try recording shadows at different times of the year. Does anything change? If so, why?
  • Start a collection of sundial photos. There is a sundial bridge in California. Students share pictures of any sundials they have seen with the class.
  • Brainstorm some of the limitations of using sundials as timekeepers. How can these be handled?
  • Older students could explore astronomical elements that must be overcome to get accurate timekeeping with sundials. These elements are the Earth’s tilted axis and the Earth’s elliptical orbit around the sun. There is a mathematical equation to apply. Also the lines on the sundial need to be adjusted in different time zones.
  • Assessment: Did students accurately record shadows at different times during the day? Were students able to extrapolate from experiment to better understand Earth’