Hours to Sunset is a glass mosaic sundial 8m wide by 4.6m high mounted on the west wall of the UWA Club. It was constructed to celebrate the University of Western Australia's 100th year.
Normally we measure time relative to midday, the time when the sun is highest in the sky. This sundial is different, it measures time relative to sunset and indicates how many hours of daylight remain in the day.
The sundial is mounted vertically on a wall facing west. A gnomon, projecting horizontally from the top centre point of the sundial, casts a shadow on the wall. During the course of the afternoon the tip of the gnomon's shadow will move from the bottom of the wall up to the top until, at sunset, it is level with the gnomon. The left hand curve of the sundial's markings plots the path of the Sun's shadow during the summer solstice, the middle line is the path during the equinox, and the curve on the right shows its path at the winter solstice. The hour lines are angled to account for the different length of day between summer and winter.
This project originated in 2005 when Susan Marie commissioned Shaun Tan to create a west-facing sundial. My role was the computation of the sundial's lines.
Shaun's transformation of these awkward lines to the final design is breath taking. Ian Middleton, artisan tiler, executed the work. Susan Marie was the project coordinator.
For more information you should visit www.culturalprecinct.uwa.edu.au/about/hours-to-sunset
Here is a timelapse movie of a model of the sundial recorded on 20th May 2012. The movie starts (with a picture of me checking the camera) at about 1.15pm, sunset is at 5.25pm. The camera battery ran out at about 1 hour before sunset.