Created by Graham Tunnadine.
The British Rail, Main Pavillion at The National Garden Festival, Gateshead, 1990. Agents: Public Art Development Trust.
Holograms, light, radio receiver, electrical circuits, computer, motors, aluminium, glass, plastic
8 x 10 x 10 Metres
Based on the shape of a traditional sundial, the Holographic Clock similarly uses light and shadow to record the time. A computer controls electric motors and lamps whose beams of light act as the clock hands.
There are three distinct structures - for the Seconds, the Minutes and the Hours. The Seconds dial is a 30 Metre circle of numbers which are made of light.
The Minutes are special mirror holograms (or holographic optical elements) which cast shadows when lit. They are suspended in a double spiral; light moves up the first spiral from the base of the back of the clock, and then down to the front of the building via the second spiral.
Just before the hour, the Minute lamps unwind rapidly through all the holograms to arrive back at zero in a way which is equivalent to the hour chime of a traditional clock.
The Hour structure rises at an angle of 45 degrees in the form of a "gnomon" or sundial arm, the 12 hours lit by individual lamps with a light collimator (reflector) for each. The images in these Hour holograms are made of floating, achromatic (mixed colour/white) and diffracted light.
The British Rail Holographic Clock is extremely accurate, receiving the time signal directly from the Atomic Clock at Rugby, England. It took approximately 6000 hours to build.