Particle Dark Matter in the 1980s and 1990s

Abstract

In 1980, the Universe was made of stars, cosmology was the province of less than 100 astronomers, the Hubble constant was only known to within a factor of two, and the hot big bang was the ``the standard model of cosmology.'' Particle physics was a thriving enterprise concerned with the inner space of quarks, leptons and the strong, weak and electromagnetic interactions. The Standard Model was newly established and the aspirations were for a ``grand unification'' of the forces and particles. By 2000, the agendas of inner space and outer space were inextricably linked, and $\Lambda$CDM with its inflation, particle dark matter and dark energy -- and a Hubble constant reliably known to better than 10\% -- was the new standard model. The big questions connecting inner space and outer space included the origin of ordinary matter, the identity of dark matter, the nature of dark energy, and an understanding of the origin of space, time and the Universe. Particle dark matter, the idea that the bulk of the mysterious dark matter is a new, long-lived or stable elementary particle, played a central in bringing together inner space and outer space, and today is still a hot topic in both fields.

Comments: Talk presented at the 4th International Symposium on the History of Particle Physics (November 2025, CERN), to be published by Cambridge University Press