In recent years, historians have debated the prospect of offering new ‘transnational’ or ‘global’ perspectives in their studies. This paper introduces the reader to this special issue by analysing characteristics, merits and flaws of these approaches. It then considers how historians of science have practised transnational history without, however, paying sufficient attention to the theoretical foundations of this approach. Its final part illustrates what benefits may derive from the application of transnational history in the field. In particular, we suggest looking at the construction of transnational networks in science, and discuss some of the methodological consequences of adopting this approach.

The ‘how’ and the ‘why’ of knowledge circulation is explored in a study of the encounter between American and British nuclear scientists and engineers who together developed a gas centrifuge to enrich uranium in the 1960s. A fine-grained analysis of the transnational encounter reveals that the ‘how’ engages a wide variety of sometimes mundane modes of exchange in a series of face-to-face interactions over several years. The ‘why’ is driven by the reciprocal wish to improve the performance of the centrifuge, though this motive is embedded in the asymmetric field of the ‘special relationship’ in nuclear matters between the United Kingdom and the United States. The result of the encounter is co-produced, hybrid knowledge in which the national provenance of the contributions from each side of the Atlantic is at once diluted and a contested site for the affirmation of national power.

This essay analyses discussions of national versus international or transnational science, with an emphasis on the journal Osiris from 1986 to 2009, including the concepts of national science, national styles and characters in science, scientific internationalism, transfer of science and scientists from one nation to another, and comparison of different national examples. The author argues that perceiving science as a ‘national’ activity has not only been persistent, it is also perhaps inevitable. This special issue on transnational histories of science raises the question of what is gained and lost by such an approach. First of all, what is the distinction between ‘transnational’ and ‘international’? The dictionary defines the latter as something existing, occurring, or carried on between two nations, while the former extends or operates across national boundaries. Thus ‘international’ implies some sort of commerce. In contrast, transnational is a loosely defined term.

Between 1860 and 1880, scientists in the United States, Argentina and Russia accompanied military expeditions on the northern Great Plains, in Patagonia, and in northeastern Asia. The extent to which the scientists were able to remain at arm's length from the slaughter of war is seen in the publications resulting from their travels. In the context of consolidating or extending national territory during the modern age, military patronage did not invalidate the research findings of attentive naturalists, who adhered to transnational disciplinary norms. There is only weak evidence to suggest that local prejudice determined the form of natural knowledge stemming from the expeditions.

We argue that industrial hazards have remained an integral feature of the international and ‘global’ economy since the early modern period, and invite historians of science into the study of their history. The growth and dissemination of knowledge about these hazards, as well as the production and trade that generate them, continue to generate deep inequalities in just who is exposed to them, as illustrated by the shifting impact of the asbestos-related disease plague in the past half-century. Exposure levels in poorer countries have risen as those in affluent societies have fallen, the latter due as much to popular protest and media exposure as to scientific expertise. We suggest that the best way to understand the formation of knowledge about these hazards is not to return to the epistemological battlegrounds of the ‘science wars’ of the 1990s but to seek more interdisciplinary integration of the multifaceted ways that material bodies, environments and interests contribute to an understanding of such hazards and injuries. We propose the framework of ‘industrial-hazard regimes’ as an avenue into the ways in which knowledge about risks and dangers at work are created, translated and contested in different countries and times. While urging a return, in some respects, to the early models of ‘progressive enlightenment’ devised by radical commentators and pioneering historians of the industrial hazard in the early twentieth century, we would revise these early approaches, and also offer some sceptical commentary on the difficulties raised, more recently, by narratives of ‘heroic populism’ or ‘anti-science epidemiology’. The critical standpoints for which we argue recognize the diverse social and political identities and loyalties not only of past contributors to the controversies on industrial hazard, but also of historians of science and medicine themselves.

When considering the works produced in history of science and transnational history, one is struck by the wide range of issues covered, the profusion of ideas and analyses, the richness and variety of what is proposed. On the other hand, one is also struck by the presence of rather repetitive methodological professions of faith, of declarations of intent about categories and rules that are quite stable over time. This article considers in turn both issues. First, what we have learned in substantial terms, what these historiographical reassessments about science and transnational relations teach us, what has been displaced and what is currently being opened. In the second part, the paper considers what is at stake in these preliminary statements of principle. The article defends the idea that we are facing two major interpretative corpuses that both do count and are heuristically productive, that in practice both are often mixed by historians – but that it is intellectually and politically decisive to consider finely the epistemologies, ontologies and postures that are offered.