Dark matter has long frustrated researchers. It seems to make up most of our universe, yet it barely interacts with that universe. And despite a plethora of active experiments hunting for dark matter, so far they’ve all turned up empty.

That has some researchers turning to the next best thing: other dark particles. Our world of normal matter has lots of different particles, so perhaps there’s a whole dark world of particles as well. To be clear, no one’s found these either, and there’s ev