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# Human Sundial

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.

• 60 to 90 Minutes
• ## Directions

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. Students 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. Bring students to a large, safe outdoor area to draw a human sundial, which will give students 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. Students stand on the center mark in the morning when the sun is out. A classmate traces where the shadow falls on the sundial. Inside the traced shadow, write the time of day. Keep recording the results throughout the day to see how the shadow moves around the sundial. Use different colors for each recorded time.
6. Ask students how accurate they think their sundial is? Why?
• ## Standards

LA: Ask and answer questions to demonstrate understanding of a text, referring explicitly to the text as the basis for the answers.

LA: Use information gained from illustrations (e.g., maps, photographs) and the words in a text to demonstrate understanding of the text.

LA: Read and comprehend informational texts, including history/social studies, science, and technical texts, in the grade level text complexity band proficiently, with scaffolding as needed at the high end of the range.

LA: Participate in shared research and writing projects.

LA: Participate in collaborative conversations with diverse partners about grade level topics and texts with peers and adults in small and larger groups.

SCI: Record and share observations of locally occurring natural events to identify patterns that are cycles and those that have a clear beginning and end.

VA: Use visual structures of art to communicate ideas.

VA: Select and use subject matter, symbols, and ideas to communicate meaning.

Possible classroom resource: Sundials: Their Construction and Use by R. Newton Mayall

With the assistance of adults, students work in small groups to investigate teacher-selected electronic sites focused on how a sundial works and how they are built. Students identify information that is important from the electronic sources. Using their own words, the groups will document the most important information contained in the reading.

Student groups record shadows at various times in the year. Have changes recorded. Students brainstorm why these changes may have occurred.

Students discuss the limitations of using sundials as timekeepers. How can the limitations be handled?

Student teams investigate what adjustments need to be make in various time zones.

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