Solar Studies : Sundial Savvy

You have probably noticed how the sun seems to change position during the course of the day.   Since the sun is at the center of our solar system, this motion is actually caused by the rotation of the earth. As the earth rotates, it creates the 24 hours of the day, while the earth’s orbit around the sun or revolution creates the different seasons of the year. 

If you locate a tall pole, like a basketball net & pole, tall fence post, light pole or similar object, you will see that it casts a long dark shadow that moves around it base.  When the slender shadows of objects such as these are measured and marked against the times of the day, a “solar day”, they serve as sun dials giving you a rough measurement of time. 

Sundials have a long history that dates to the first or second century in ancient China, but the most notable ancient sun dials are associated with the tall obelisks of ancient Egypt.  The Washington monument in Washington, DC is an obelisk that creates a sundial effect with the U.S. flags that surround it. The long post that creates the shadow for the sundial is called a gnomon.

NASA flickr Image

To complete this activity in the solar badge, you will have a choice of activities to create a sundial and take a photograph to post for credit. 

Activity

To complete this activity in the solar badge, you will have a choice of activities to create a sundial and take a photograph to post for credit.

A. Go to the web site https://www-istp.gsfc.nasa.gov/stargaze/Sundial.htm and print the northern hemisphere sundial on a thick cardstock or printer paper. Follow the directions and construct the sundial. Set it up in the sun near your home and take a photo with a watch or cell phone clock aligning the time to post for credit.

B.  Locate a tall post, flag pole, tether ball post, or any pole with a visible end in its shadow in your neighborhood or school yard, get permission to use chalk or another temporary medium to draw marks on the ground at the top of the hour and bottom of the hour for a four-hour time period. Take a photo of your work with a watch or cell phone clock aligning the time to post for credit.