After decades of measurements and debate, we are now confident that the overwhelming majority of our universe’s matter – about 84 percent – is not made up of atoms, or of any other known substance.
They’ve built ultra-sensitive detectors, deployed in deep underground mines, in an effort to measure the gentle impacts of individual dark matter particles colliding with atoms.
They’ve built exotic telescopes – sensitive not to optical light but to less familiar gamma rays, cosmic rays and neutrinos – to search for the high-energy radiation that is thought to be generated through the interactions of dark matter particles.
We have searched for signs of dark matter using incredible machines which accelerate beams of particles – typically protons or electrons – up to the highest speeds possible, and then smash them into one another in an effort to convert their energy into matter.
The idea is these collisions could create new and exotic substances, perhaps including the kinds of particles that make up the dark matter of our universe.
Over the past 15 years, for example, experiments designed to detect individual particles of dark matter have become a million times more sensitive, and yet no signs of these elusive particles have appeared.
We had what seemed like very good reasons to expect particles of dark matter to be discovered by now.