Wednesday, May 07, 2025
3:00-4:30pm
Humanities 1, Room 210
On Wednesday May 7th, join Science & Justice Visiting Scholar Jaco de Swart for a talk, “Dark Matter, Dirty Xenon, and the Limits of Laboratory Experiments.”
Laboratory sciences crucially depend on experiments being clean. But what is clean? In this talk, I open up versions of clean relating to different ontological registers, and trace the material practices of cleaning as they are attuned to experimental specificities. My case is the XENONnT experiment in the Gran Sasso Mountains of Italy which is meant to detect dark matter in the form the hypothetical WIMP – the Weakly Interacting Massive Particle. This experiment is clean when it is ‘free from signals that mimic dark matter’. In practice, such cleanliness has been difficult to achieve – soaps may be radioactive, steel may spread electronegativity, and humans are altogether dangerously filthy. And because, at least thus far, dark matter remains elusive, it is impossible to tell whether the meticulously cleaned detector is adequately clean. Additional cleaning efforts will make the detector sensitive to neutrino particles: a background that cannot be cleaned away. As the experimenters dread the possibility that this means their experiment will end in limbo, other physicists are now trying to detect other hypothetical dark matter particles with other kinds of experiments, requiring other kinds of cleanliness. The XENONnT experiment itself, meanwhile, has had to ensure that it does not interfere with environmental
This work is done in collaboration with Annemarie Mol (University of Amsterdam).
Jaco de Swart is an AIP Helleman Postdoctoral Fellow at MIT’s Program in STS and Department of Physics, and a visitor at UCSC’s Science and Justice Research Center. He received his PhD at the Institute of Physics at the University of Amsterdam, was a postdoctoral researcher at the Amsterdam School for Social Science Research, and has held visiting positions at Princeton University and the Institute for Advanced Study. His research focuses on historical and anthropological studies of open problems in cosmology and he is currently writing a book on the history of dark matter under contract with MIT Press. De Swart is also a member of several physics collaborations to help develop social and environmental responsible research practices. He has a passion for science communication—appearing in PBS NOVA’s Decoding the Universe—and is bassist in the band X Raiders.