The theoretical physicist Steven Weinberg once famously captured the traditional image of what physics is all about. Writing in a 1963 document that was designed to garner public support for what was eventually to become the Fermi National Accelerator Laboratory in the US, the future Nobel laureate likened scientists to “members of an expedition sent to explore an unfamiliar but civilized commonwealth whose laws and customs are dimly understood”. While these explorers may find it “exciting and profitable…to establish themselves in the rich coastal cities of biochemistry and solid-state physics”, the most vital work, he implied, was carried out by those who continue “up river, past the portages of particle physics and cosmology, toward the mysterious inland capital where the laws are made”.

Weinberg was portraying the central thrust of physics as a specific kind of risky quest: to explore and understand the ultimate constituents of matter and the basic forces that govern them — the simplicity frontier, one might call it. In this traditional image, physics is a solitary quest, generally pursued by physicists without significant collaboration with scientists from other disciplines. As the US historians Lillian Hoddeson, Adrienne Kolb and Catherine Westfall write in their new book Fermilab: Physics, the Frontier, and Megascience, “The image of frontier exploration has helped physicists express their identity as pioneers who boldly pursue the limits of our understanding of nature.” Indeed, Fermilab itself is strongly linked with the frontier motif — manifested by everything from the testimony of its directors at Congressional hearings to the bison allowed to roam on the laboratory grounds.

But physics is changing, and Weinberg’s simplicity frontier no longer captures the central thrust of physics. Physicists are still working at a frontier, but they are not doing so alone, moving towards a mysterious, uninhabited inland territory that they will take possession of themselves. Rather, they are working at the frontier with tribes of other scientists in the process of building new interdisciplinary cities. Those physicists who are still trying to work their way up river by themselves towards the traditional frontier have found it ever more expensive and impractical to do so. The most symptomatic illustration of this trend over the last 20 years was the cancellation, in 1993, of the Superconducting Super Collider by the US, and the contrasting success of the Large Hadron Collider at CERN — a largely European project but involving scientists from many nations, including the US.

In the October special 20th anniversary issue of Physics World, Robert P Crease discovers how physics is gradually fragmenting into tighter subdisciplines while fusing with other fields.

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