Reflections of the sunlight

Connecting with other educators who share my interests and help me expand them is one of the benefits of writing for NSTA’s journal and blog. Guest blogger Tom Lough is a contributor to Science and Children and has taught science and science education classes at many levels. He is now a science education consultant in Round Rock, TX.  

Welcome Tom!


Like many, I have unbounded enthusiasm for the 2018 August issue of Science and Children! Well done, NSTA! Did you read the Early Years column, titled “Making Sense of Their World”? Young children soak up their experiences and observations of the world around them, and ask all sorts of questions as they try to put everything together.

The second part of the column reminded me of an activity we are doing with five classrooms at Caldwell Heights Elementary School in Round Rock, TX, observing the apparent motion of the sun.  These rooms all have south-facing windows, meaning that the sun shines into each room all year long.

A small craft mirror glued to a south-facing windowsill.

A small craft mirror glued to a south-facing windowsill.

A reflection of sunlight on the classroom ceiling.

A spot of reflected sunlight on the classroom ceiling.

Instead of observing the sun directly, we are using a small craft mirror glued to a south-facing windowsill to produce a reflection on the classroom ceiling. As soon as the mirror was installed and the spot appeared on the ceiling, the effect was immediate on the children. They were mesmerized by the bright dot. They couldn’t take their eyes away from this new classroom visitor. After a few minutes, someone said, “I think it’s moving!” They were hooked! 

If you decide to try this, from this point on you can expect many questions from the children. It is not necessary, or even preferable, to answer them. Rather, invite them to continue their observations and see if they can find their own answers. Encourage journaling, sketching, or photographing as ways to document their observations. Then they can search for patterns more systematically. 

There are many advantages to this particular activity. One of the most important ones is safety. There is no need to look directly at the sun. Second is its simplicity. Just glue the mirror in place and step away. No moving parts, no further assembly required. And then there are the many different patterns.

Children will be quick to point out the obvious patterns, including when and where the dot appears and disappears each day, which direction it moves across the ceiling, and the degree to which the sky is cloudy or clear. 

As the weeks and months go by, they might notice that the path of the daily movement changes. During the fall months, the path gets farther away from the window, and during the winter/spring months, the path is closer to the window. Older children might figure out that this has something to do with the height of the sun in the sky at different times of the year, which, in turn, is related to the tilt of the earth’s axis.  For example, children might choose to photograph the dot each week. It won’t be long before the movement of the path is obvious, especially if the ceiling is patterned or if it has a grid of tiles for easy reference. 

Window with small circular mirror on the windowsill and the reflected sunlight dot on the ceiling.

Can you spot the mirror on the windowsill and the reflected sunlight on the ceiling?

Within this simple activity is an unexpected level of complexity that can be uncovered with the addition of a simple action by the teacher or other adult. Select a convenient time of day somewhere between 11:00 and 1:00, and use a push pin or piece of tape to mark the location of the dot on the ceiling at that same time once or twice per week. You will need to be consistently punctual about this, down to the minute. Don’t worry, though, because your “little alarm clocks” will remind you! (And use a safe stool or ladder.) 

 Over the course of the school year, the marks on the ceiling will trace out part of a pattern called the analemma, which is the apparent path of the sun in the sky as seen at the same time each day for a year. (To trace the full analemma, someone would have to come in during the summer months to continue marking the dot position at the appointed time.)

Analemma pattern printed on a globe of EarthThe analemma is a pattern that has been known for hundreds of years, and was printed in the middle of the Pacific Ocean on globes some time ago (see photo). Shadows of outside objects outdoors, such as the school flagpole, could also be used to generate an analemma. 

Who knew that something as simple as gluing a mirror to a window sill could produce such a wide range of effects and invite so many questions? 

Note that if you do decide to trace the analemma, be alert to when Daylight Savings Time comes and goes. We suggest keeping the same observation time, so that the children can see the curious effect of the change in path. In other words, if you had selected 11:30 AM as your “dot time” prior to the time change, continue using 11:30 AM after the change, even though the sun will be in a different location. 

Resources

An example of the type of mirror, https://www.joann.com/big-value-mirrors-1-inch-round-25-pc/10232692.html 

Lough, T., & Vanover, C. (2014, October). Find your School’s Analemma. Science and Children, 52(2): 55-59.

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