Global communications are making physical distances between research collaborators ever more irrelevant. Our analysis of 39 million authors' addresses in research publications indexed in Thomson Reuters' Web of Science for 1980–2009 reveals some surprising exceptions to this trend.

We found that collaboration in the natural sciences over this period spanned the longest distances, with the medical and life sciences catching up fast. Collaboration was most confined for the social sciences and humanities, but this too has been extending rapidly over the past decade. Overall, the average collaboration distance increased more or less linearly from 334 kilometres in 1980 to 1,553 km in 2009.

Countries in the Southern Hemisphere, such as New Zealand and Australia, and several developing countries in the tropics contributed to some of the higher scores. Turkey, Iran, India and most eastern European countries are among the least globalized in terms of long-distance scientific collaboration. Surprisingly, some of the countries with rapid growth in scientific-publication output, such as China and Brazil, show hardly any increase in globalization, or even a slight decrease.

Researchers are in a better position than ever before to engage in long-distance collaborations. This, combined with the increasingly dispersed location of research centres across the globe, could account for the 5.4% annual growth in collaboration distances.