Chemical Galaxy is a new representation by Philip Stewart of the periodic system of the elements, better known in tabular form as the periodic table, based on the cyclical nature of characteristics of the chemical elements (which depend principally on the valence electrons). Even before Dmitri Mendeleev produced the first satisfactory table, chemists were making spiral representations of the periodic system, and this has continued ever since, but these were usually circular in outline.
John Drury Clark was the first to present a spiral with an oval outline. His design was used as a vividly coloured two-page illustration in Life magazine for 16 May 1949. In 1951, Edgar Longman, an artist, not a chemist, painted a large mural, adapting the Life image by making the shape elliptical and tilting it to produce a dynamic effect. This inspired Stewart, then 12 years old, with a love of chemistry. Having just read Fred Hoyle's book The Nature of the Universe, he had the idea that Longman's design resembled a spiral galaxy. He returned to the idea many years later and published a first version of his "galaxy" in November 2004. His design seeks to express the link between the utterly minute world of atoms and the vastness of the stars, in the interior of which the elements were forged, as Hoyle was the first to demonstrate in detail.
Chemical Galaxy is intended primarily to excite an interest in chemistry among non-chemists, especially young people, but it is fully accurate scientifically in the information that it conveys about relationships between the elements, and it has the advantage over a table that it does not break up the continuous sequence of elements. A revised version, Chemical Galaxy II, introduces a new scheme, inspired by Michael Laing, for coloring the lanthanides and actinides, to bring out parallels with the transition metals. The design was translated into digital form by Carl Wenczek of Born Digital Ltd.