Simple Sundial Experiment

Increase your homeschooler’s understanding of concepts, including time, seasons, and the relationship between Earth and the sun by building a simple sundial. Start with helpful background information from Home Science Tools about how we use the sun to tell time. Then, head outside to conduct your own experiment.

Helpful Vocabulary
Axis: An imaginary line about which an object, such as Earth, rotates.

Equator: An imaginary line that circles Earth exactly half way between the North Pole and the South Pole, dividing the Northern Hemisphere from the Southern Hemisphere.

Meridian: One of many imaginary circles on Earth’s surface that pass through both the North and South Poles.

Prime Meridian: The meridian that measures zero degrees, from which longitude east and west is measured. It passes through Greenwich, England.

Latitude: A distance north or south of the equator that is measured in degrees (up to 90).

Longitude: A distance east or west of the prime meridian that is measured in degrees (up to 180).

Gnomon (pronounced noh-mon): The portion of a sundial that casts a shadow.

Items Needed
Rectangular piece of cardstock
Scissors
Straw
Strong tape
Magnetic compass
Watch or clock
Ruler
Pencil

Instructions
1. Choose one of the long edges of your rectangular cardstock to be the base of your sundial. Use the scissors to make a small hole in the page that sits approximately two inches from the bottom and near the middle.

2. Create three tabs, equal in width, at one end of the straw by using the scissors to cut three half-inch slits up its side. Bend the tabs outward.

3. Feed the uncut end of the straw through the hole in the cardstock until the tabs sit flush against the paper.

4. Tape the tabs securely to the bottom of the cardstock.

5. Head outside shortly before noon and find a hard, flat surface in the sun where you can place your sundial. Be sure the spot receives sunshine all day long.

6. Using your compass, position the cardstock so the shadow from the gnomon (straw) points north. Use the tape to secure the cardstock in place.

7. When your clock or watch strikes noon, use the ruler and pencil to draw a straight line that marks the edge of the gnomon’s shadow. Label the line with the number 12.

8. Repeat step seven at the top of every hour until the sun sets, labeling each line with the number that corresponds to the time it was recorded.

9. Beginning at sunrise the next day, repeat step seven at the top of every hour until noon. Be sure to label each line with the number that corresponds to the time it was recorded.

Discussion Points
By tracking the shadow cast by the straw at the top of every hour, you’ve created a simple sundial that can tell accurate time for your specific location and time of year. In order to be accurate all year round, the gnomon of your sundial must sit parallel with Earth’s axis. In other words, the tilt of the gnomon would have to equal the latitude of your current location. Find your current latitude.

Source:
Home Science Tools