Labs from YSI 95 :
Shadow Observations.

April Whitt
CARA Yerkes Summer Institute, August 1995

This is the staff copy of the lab.


Using a plastic film canister as a gnomon, students will record shadows at specified times during the session. They will compare these with shadows recorded at the same times from different geographical areas. Students will explain the differences among the shadow records.

Materials needed

Students will assemble apparatus as described in the direction sheet below. Shadows will be recorded at 9:30, 10:00, 10:30 and 11:00 AM. Their records will be compared to those of other participants in other locations on Earth. Using an atlas and globe, students will determine the positions of each of the other participants, chart the differences among the shadows and explain them.


Tape the worksheet to the cardboard. Write in the name of your museum or city/state/country in the space labeled "Place where tracing is made". Write in your latitude and longitude, and please put the date you're doing the tracings on the sheet somewhere too. Fill the film canister with sand, put the cap on tightly, and put the canister in the circle marked on the paper.

Take the apparatus outside. Find a flat surface like a sidewalk on which to set up your cardboard and canister. Choose a place where you can either leave the set-up undisturbed for the whole day, or where you can put the cardboard and canister in exactly the same place for each tracing. Determine which direction is north.

The edge of the paper with the film canister on it must line up on an east/west line, with the canister on the south side of the paper (for the northern hemisphere, or on the north side if you're in the southern hemisphere).

At specified times during the day, use a pencil or crayon to trace the shadow the canister makes on the paper. Tracings made every 30 minutes will make a "fan tail" pattern on the paper. For the CARA project August 7-10, 1995, we'll use about five tracing times from 9:30 AM to 11:00 AM.

Each time you trace the shadow, write the time next to it. Make sure the traced outline is clear and dark. When a day's worth of tracings is finished, please FAX a copy to Yerkes Observatory for use in our summer CARA institute. If you'd like us to FAX you copies of all the shadows we receive from around the world, please let us know. And thanks for your help!

If possible, I'd like to try a rehearsal on Friday, August 4. Make the tracings at 9:30. 10:00, 10:30, and 11:00 AM and fax them to Yerkes. Anyone who can participate in this will be greatly appreciated!

A blank data sheet is here; sample filled-out data sheets can be found here and here as part of the YSI 95 on-line.

Important Disclaimers and Caveats: