• 2005
• Domain
• Exhibit map

The galaxy-like map of science was created using a multi-step process from the citation patterns in 800,000 scientific papers published in 2002. Each dot in the galaxy represents one of the 96,000 research communities active in science in 2002.

A research community is a group of papers (9 on average) that are written on the same research topic in a given year. Over time, communities can be born, continue, split, merge, or die.

The galaxy map was generated by calculating a disciplinary map based on journals, and then overlaying research community positions on the disciplinary map. The disciplinary map was calculated from normalized journal-to-journal bibliographic coupling coefficients and consisted of some 7300 journals that formed 671 clusters.

Journal cluster positions were calculated using the VxOrd layout algorithm. Research community memberships were calculated from normalized bibliographic coupling coefficients between papers, VxOrd for layout, and a modified single-link clustering routine. Research community positions were then calculated based on the journal distribution within each community. Thus, for example, communities with all papers in biochemistry journals show up in the biochemistry section of the galaxy map, while communities evenly split between biochemistry and chemistry journals show up midway between the biochemistry and chemistry areas of the map.

Description of Unique Features: This is the most comprehensive (and in the authors' opinion, the most accurate) literature map ever generated.

Visual Perception or Design Principles Applied: Full (large) map on left allows viewer to identify major disciplines and learn a disciplinary framework. Smaller maps on right allow viewer to mentally overlay topical information on the disciplinary framework. Colors tie text passages (stories) with map labels.

Cognitive Principles or Metaphors Employed: Galaxy plot uses a starfield metaphor, where black indicates open space. Proximity, concentration of, and distance between dots and clusters indicate distance between fields, size of fields, and levels of interdisciplinary activity. Labels are also sized to scale to the size of each discipline (cubed root).

Data Used: Combined Science Citation Index and Social Science Citation Index, file year 2002.

Data Analysis Techniques Applied: index based on bibliographic coupling counts at the paper level.

Spatial Layout Techniques Applied: VxOrd (force-directed graph layout).