Physicists Propose Reviving 1773 Cavendish Experiment to Search for Millicharged Dark Matter

Peter Graham at Stanford University and his colleagues propose reviving an experiment run by Henry Cavendish in 1773 to search for millicharged particles as dark matter candidates. The 18th-century setup measured the electric potential at the surface of two nested metal shells.

The new version would apply voltage to the outer shell and measure the voltage difference with the inner shell to detect the presence of the tiny-charged particles.

The proposed experiment includes an accumulator device that collects charged particles from the room and brings them into the setup, Harikrishnan Ramani at the University of Delaware said. Millicharged particles could be extracted from the Cavendish device and studied afterwards. “You could store and gift people millicharged particles,” Ramani said.

The estimated cost of the proposed experiment is under a million dollars, a thousandth of operating a particle accelerator for a year. The researchers’ calculations show the experiment could be more sensitive than some future particle accelerator experiments. 1103/83fd-mnpk.

Kevin Kelly at Texas A&M University says the researchers’ estimates are probably conservative. The proposed experiment could be between 100 and 10,000 times more sensitive than past methods. This would allow detection of millicharged particles with charges even tinier than previously assumed.

Christopher Hill at the Ohio State University says the technique could be better than some of the things that he and others are already doing. Hill estimates that the experiment could be built and completed much more quickly than a particle accelerator experiment. “It would be a big step to understanding what much of the universe is made of, and how it works,” Hill said.

Harikrishnan Ramani says the experiment could happen as soon as two or three years. The team are now ironing out the details of building and securing funding for the experiment. If successful, the approach would offer a cheaper and faster route to probing one candidate for the invisible matter that makes up more of the universe than ordinary matter.

Henry Cavendish’s original experiment was designed to explore electromagnetism. Graham and his colleagues focused on millicharged particles because their slight electric charge makes them a good match for the nested-shell design. Dark matter remains unknown despite decades of searches using colliders and underground detectors.