Ever notice that your shadow’s length changes in size? Determining the length of a shadow on a surface is as easy as using a measuring tape or yardstick to measure the shadow. But did you know that your shadow also can help calculate your area’s local noon?  

Solar noon is the time of the day when the sun reaches its highest point in the sky, commonly referred to as local noon. Usually, this does not equal noon (12 pm) on your clock. The relationship between clock noon and solar noon depends on your location within your time zone and the time of year.  

The summer solstice, in June, is one of the longest days of the year. Let’s celebrate outside and measure when the sun is highest in the sky in your neighborhood. Use your mathematical skills to calculate your local solar noontime.

Tools:  

• Measuring Tape (preferably), yardstick, or ruler

• Chalk (optional)

• Paper and Writing Utensil 

• Sun stick, an object whose shadow will be measured 

 Steps: 

Step 1: Discover, potentially over a week's time, when the sun is highest in the sky (solar noon) in your area. Keep a record of these times to help with this activity. For reference, use this site to give you input of sunrise, sunset, and daylength to estimate a 2-3 hour solar noontime window.

Step 2:  When you have identified the solar noon window, let the experiment begin! Pick a tall object to use as your “sun stick”. You will be measuring the shadow of that "sun stick” so make sure the object is tall enough to see the change in length of the shadow. Ideas include a stop sign or flagpole.

Step 3: Measure and record the identified object’s height and initial shadow length. Be sure to also record the time when you measured that shadow. Additionally, if wanted, use chalk to record the length and time.

Step 4: Every 10-20 minutes, record the time and length of the shadow. As time progresses, the shadow will get shorter, so be sure to continue to measure until your records show the shadow getting longer again — then you know your solar noon has passed!

Step 5: Looking at the data, what was your longest shadow? When was the shortest shadow? Was your solar noon close to the same time as actual noon (12 pm) on your clock?  

To Do or Learn More: 

• Build your own portable sundial!

• Calculate when local noon is without measuring shadows.

• Continue your math skills by calculating the noon sun angle!

• Introduction to Solar Orientation video.

• Learn more about the summer solstice and other seasons.