It’s believed most of the matter in the universe is invisible. This is the fabled dark matter, a peculiar substance whose gravitational effects we can see in galaxies but we are yet to confirm in labs. A new proposal takes a peculiar new approach to this search – perhaps dark matter can be spotted using a billion tiny pendulums.
The reasoning behind the unconventional idea has to do with the size of dark matter particles. Their proposed range is huge, from something much lighter than an electron to black holes tens of times the mass of our Sun. The pendulum will help probe a middle region of dark matter particles that are roughly the size of a grain of salt.
While dark matter doesn’t interact with light, its mass pulls things in with its gravity. That means a particle of dark matter flying past a pendulum would give it a little pull. Now, the pull is very small and a single pendulum would be influenced by environmental noise, so it would get lost. Luckily there’s strength (and a solution) in numbers.
The team suggest the use of a billion tiny pendulums. The passage of dark matter particles should then become apparent when all these motions are considered together. As reported in Physical Review D, the design they have in mind will be sensitive to masses between 1/5,000th of a milligram and a few milligrams.
Current dark matter detectors are looking for much smaller particles and focus on very rare interactions that might exist between regular matter and dark matter. This setup instead only cares about the gravitational pull, so the sole unknown is the mass of the dark matter particle.
If dark matter is found with this method, it would be amazing. If it isn’t, we can confidently remove a large chunk of potential masses from the playing field. Some preliminary tests with this general approach have already been conducted.
The technology for this might come from the smartphone industry and, if so, could have applications beyond dark matter. It could be used to study phenomena like distant seismic waves as well as some cool particle physics detections.