Circa is a light sculpture that represents the circannual cycle of light levels on earth’s surface in West Sussex. It is divided into twelve physical elements (circles) that each represent one month of the year.
The total circumference of each circle represents a twenty-four hour day, the amount of daylight hours are displayed through the percentage of the circumference that is lit up. For example for an average of eight hours of daylight over the month of January only one third of the circumference will be lit up.
Light is the primary zeitgeber (time giver), its presence and absence is essential in regulating overt rhythms in biochemistry, physiology, and behaviour throughout an organism.
The installation also makes visible the simple oscillations and feed-back loops that have been found to give plant life their internal clocks and circadian rhythm.