Students will build a sundial and record observations from it.
This activity introduces students to various topics associated with the revolution of the earth around the sun and the earth’s rotation on its axis with respect to the sun.
Preparation and Set Up:
Gather the necessary materials.
Arrange students in pairs.
Distribute necessary materials.
A sundial can record one of two things. Either the sun’s position in the sky can be recorded at various stages throughout the day or the length of the shadow cast can be monitored at the same time everyday for a period of weeks or months. The lesson can be used to target either of these principles.
Gnomon – The object which casts the shadow.
Solstice – The day of the year that is has either the longest or shortest amount of daylight depending on the sun’s position in the sky (in the northern hemisphere the winter solstice is the shortest day and the summer solstice is the longest day).
Equinox – The two days of the year that fall midway between the Summer and Winter solstices. Day and night are almost equal.
Start with an introductory discussion about seasons as determined by the sun. The summer and winter solstices, and the fall and spring equinoxes.
Sundials support this theory by demonstrating that the sun’s rays are most indirect in the winter, when the sun is lowest in the sky and the day is the shortest. The shadow cast the the gnomon is the longest.
The summer is the opposite. The shadow cast is the shortest.
Introduce the idea of the Earth’s rotation.
To us, it appears that the sun moves across the sky, but it is actually the revolution of the Earth on its axis.
When the sun rises in the East it cast a shadow that can be tracked all day long as the sun moves from East to West.
To make a sundial:
Draw two perpendicular lines on the back of a paper plate that cross at the center.
Designate one line to be north.
Draw in a compass rose to label all the directions.
Place a popsicle stick in the center and secure it with tape on the underside of the plate.
You can either demonstrate with a flashlight how the sundial works or bring them outside.
Have students mark where the dial is at a particular time of day (use a compass to orient the sundial).
Let students go outside at different times of the day to test their sundial (be sure to always use a compass to orient the sundial).
Do this activity over a month/year to see how the length of the shadow changes with the seasons.