Researchers propose updating a 1773 experiment by Henry Cavendish to detect millicharged particles, a potential dark matter candidate. The design uses nested metal shells and could be 10,000 times more sensitive than past methods. The setup promises to be cheaper and faster than particle accelerators.
In 1773, British scientist Henry Cavendish conducted an experiment with two nested metal shells to study electromagnetism by measuring electric potential differences. Now, Peter Graham at Stanford University and colleagues suggest adapting this setup to search for millicharged particles (mCPs), exotic particles with tiny charges that could form dark matter, which outweighs ordinary matter in the universe but remains unidentified. The team plans to apply voltage to the outer shell and measure voltage differences with the inner one, detecting any mCPs present due to their charge. An accumulator device would draw charged particles from the room into the apparatus, as explained by team member Harikrishnan Ramani at the University of Delaware. The experiment's cost is estimated under a million dollars, far less than running a particle accelerator for a year. Calculations indicate it could surpass the sensitivity of upcoming accelerators. Kevin Kelly at Texas A&M University called the sensitivity estimates conservative, potentially 100 to 10,000 times better, enabling detection of even tinier charges. Christopher Hill at Ohio State University praised the approach, noting it could be built much faster than accelerators and lead to a major discovery about the universe's composition. He is considering a similar setup with his team. The researchers are refining details and seeking funding. Ramani said success could come in two or three years, allowing mCPs to be extracted and studied afterward.