Big science is a term used by scientists and historians of science to describe a series of changes in science which occurred in industrial nations during and after World War II, as scientific progress increasingly came to rely on large-scale projects usually funded by national governments or groups of governments. Individual or small group efforts, or Small Science, is still relevant today as theoretical results by individual authors may have a significant impact, but very often the empirical verification requires experiments using constructions, such as the Large Hadron Collider, costing between $5 and $10 billion.
While science and technology have always been important to and driven by warfare, the increase in military funding of science following the second World War was on a scale wholly unprecedented. James Conant, in a 1941 letter to Chemical Engineering News, said that World War II "is a physicist's war rather than a chemist's," a phrase that was cemented in the vernacular in post-war discussion of the role that those scientists played in the development of new weapons and tools, notably the proximity fuze, radar, and the atomic bomb. The bulk of these last two activities took place in a new form of research facility: the government-sponsored laboratory, employing thousands of technicians and scientists, managed by universities (in this case, the University of California and the Massachusetts Institute of Technology).
In the shadow of the first atomic weapons, the importance of a strong scientific research establishment was apparent to any country wishing to play a major role in international politics. After the success of the Manhattan Project, governments became the chief patron of science, and the character of the scientific establishment underwent several key changes. This was especially marked in the United States and the Soviet Union during the Cold War, but also to a lesser extent in many other countries.