Read this year's World's Fair in Japan has a very special attraction in the field of optics: the largest ever built kaleidoscope, built in the form of a tower. Viewers can admire from the entrance hall of a more than 40 -meter-diameter play of colors on the spherical ceiling. A sophisticated mirror arrangement and three large wheels made of colorful glass pieces ensure that constantly new patterns and color combinations are generated. The building, dubbed the "Earth Tower", represents Nagoya's contribution to the World's Fair in 2005. Like many of the well-known kaleidoscopes, which are only a few tens of centimeters long, the building is triangular in plan, but has a height of 47 meters. The sunlight penetrating through the windows of the tower encounters a complex arrangement of mirrors which, after multiple reflections, guide it onto three rotating glass panes.
In this way, as in ordinary kaleidoscopes, an image of a continuous flow of symmetrical patterns can be seen from the entrance hall of the tower. The World's Fair will be open until 25th September 2005.
The invention of the kaleidoscope is attributed to the famous Scottish scientist David Brewster, known for his descriptions of the refraction of light at prisms. Most commercially available models use one or more panes of glass, often filled with beads or gel-like liquids.