  Using data from computer databases of scientific papers in physics,
biomedical research, and computer science, we have constructed networks of
collaboration between scientists in each of these disciplines. In these
networks two scientists are considered connected if they have coauthored one or
more papers together. We have studied many statistical properties of our
networks, including numbers of papers written by authors, numbers of authors
per paper, numbers of collaborators that scientists have, typical distance
through the network from one scientist to another, and a variety of measures of
connectedness within a network, such as closeness and betweenness. We further
argue that simple networks such as these cannot capture the variation in the
strength of collaborative ties and propose a measure of this strength based on
the number of papers coauthored by pairs of scientists, and the number of other
scientists with whom they coauthored those papers. Using a selection of our
results, we suggest a variety of possible ways to answer the question "Who is
the best connected scientist?"
