  The ongoing globalisation of science has undisputedly a major impact on how
and where scientific research is being conducted nowadays. Yet, the big picture
remains blurred. It is largely unknown where this process is heading, and at
which rate. Which countries are leading or lagging? Many of its key features
are difficult if not impossible to capture in measurements and comparative
statistics. Our empirical study measures the extent and growth of scientific
globalisation in terms of physical distances between co-authoring researchers.
Our analysis, drawing on 21 million research publications across all countries
and fields of science, reveals that contemporary science has globalised at a
fairly steady rate during recent decades. The average collaboration distance
per publication has increased from 334 kilometres in 1980 to 1553 in 2009.
Despite significant differences in globalisation rates across countries and
fields of science, we observe a pervasive process in motion, moving towards a
truly interconnected global science system.
