Thrilling hints of elusive dark matter particles are starting to fade

For more than 20 years, an experiment buried beneath a mountain in Italy has spied a strange signal that the researchers running it believe to be a sign of elusive dark matter particles. Now, a smaller but otherwise nearly identical experiment in Spain has failed to find this signal, leading scientists to question whether the Italian detector really saw anything at all.

Both detectors are designed to search for weakly interacting massive particles (WIMPs), a front-runner to explain the effects of dark matter. These particles are hypothesised…