create a sundial


Often people look up in the sky to guess what time it is by the position of the sun. Your sundial will be accurate on the day you make it. For the next few months it will be fairly correct. After that – don’t count on it at all or you’ll certainly be late!

To make a sundial you need:

  • an aluminum pie plate or a cut out circle of cardboard
  • a plastic straw
  • masking tape
  • a marker
  • a clock or watch
  • a sunny day


  1. Stand the straw straight up in the center of the pie late or cardboard circle.
  2. Tape around the base of the straw to keep it standing up
  3. Put your sundial outside on a sunny day.

By looking at your watch or clock, mark where the shadow of the straw falls on the sundial at either 3, 6, or 12 o’clock. Mark the other hours on the plate, using the first time you’ve recorded as a guide. If you more the sundial just a little from its original location, the time will still be fairly accurate. But if you move your sundial to a different city, it will not tell the correct time.

That’s engineering

  • importance of accuracy in time measurements that are used today in a wide variety of instruments such as cell phones, computers, and GPS navigation systems to synchronize their functions. Improving precision, be it in component size or digital time measurement, is a design criterion that engineers address every day.

Do It
Challenges for you to work on…

  • Build a Portable Sundial – investigate the accuracy of sundials and the discrepancy that lies between “real time” and “clock time.” Track the position of the sun during the course of a relatively short period of time and make a shadow plot, a horizontal sundial, and a diptych sundial.

Learn more…