From Joseph Silk at Nautilus:
The strongest tool for discovery of dark-matter particles would be a new particle collider. Fast-forwarding some three decades from now, physicists plan to build a collider with seven times the power of the LHC. Studies are underway both in China and in Europe. Crudely scaling up from the LHC, it would cost $25 billion in today’s dollars. Shared among nations and spread over the decades, that might just be feasible. But it is probably the limit. Even if physicists had unlimited resources, nothing would be gained by building anything larger. At that point, any unknown particle would have to be so massive that, were the particle produced in the same way as its lighter counterparts, the big bang would not have produced it in sufficient quantity.
Despite these immense efforts, we may not find any signals. That would be a gloomy prospect. Maybe there is no dark matter. We keep looking for deviations from general relativity. So far we have found none. On the contrary, the detection of black holes in 2016 by gravitational waves has bolstered Einstein’s theory—and its corollary, the existence of dark matter.
But look on the bright side. There could be immense mysteries and revelations about the dark side of nature that we will never glimpse unless we search. For now, we keep looking for particles. We can do nothing else but press on.
Well, pressing forward beats pressing backward or standing still. But it would sure help if anyone anywhere found some dark matter somewhere instead of theorizing about it.
See also: Are dark energy and dark matter the same thing, really?