Human Sundial

Our Human Sundial: 875 North 200 East, Logan, Utah

What is a sundial?Sundials measure time of day based on the relative position of the sun in the sky.

How do sundials work?

The sun appears to move across the sky because earth spins on its axis. Sundials mark the time of day based on the apparent postion of the sun in the sky. Because earth's axis is tilted, and thanks to Standard and Daylight Saving time, creating an accurate sundial becomes a little complicated.

Sundials have a stick or rod of some type (called a gnomon) that creates a shadow which falls on numbers representing the time of day. If the gnomon is vertical, the time will not remain accurate throughout the year because earth's axis is tilted and the earth moves around the sun. This causes the North Pole to tilt away from the sun during winter and towards the sun in summer, altering the location of sunrises and sunsets on the horizons as well as the height of the sun in the sky at noon. To compenstate for this variable, the gnomon must be parallel to earth's axis. This can be accomplished by tilting the gnomon at an angle equal to your latitude.

Our sundial is interctive. Students become the gnomon. Since it is difficult to lean at a 41 degree angle (our latitude) without falling over, we compensate for the tilt of the axis by changing where a student stands throughout the year in order to reveal the accurate time. During winter for example, when the North Pole is tilted away from the sun, we adjust by standing further away (unlike most sundials our gnomon is not fixed in place) from the number stones during winter and gradually moving forward (on the month stones) as the seasons progress towards summer.

To overcome the problem posed by switching from Standard time to Daylight Saving time in the spring and fall, we have created two rows of time stones, which are colored to match the appropriate month stones. For our clock to read most accurately, the student (gnomon) should stand as close to the center line of the month stones as possible.

Construction

Work on the sundial began during the 2003-2004 school year in conjunction with the Solar Calendar project. Both were funded by a grant from the Logan City School District Foundation. These projects unfolded based on a constructivist model of learning. The basic idea being that we all learn by creating meaning from experiences. Part of the sixth grade state curriuculum requires that I teach students why we have seasons and night and day. The solar calendar and sundial allowed students to discover the answers to these questions by collecting and analyzing real data.

Logan Memorials and Brown Monuments both gave us a break on the sandblasting and laser etching of the month stones and explanation plaque. John Westenskow's ceramics classes here at Mount Logan Middle School made the time stones. Students surveyed and plotted the location of the stones and also provided the physical labor which entailed digging holes and pouring cement.

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