Dark matter is to scientists what Moby Dick is to Captain Ahab: they know it's out there, yet, despite spending copious amounts of time searching, they just can't obtain what they're seeking.
Granted, Ahab did die after finally finding his white whale, but it's unlikely scientists will suffer a similar fate upon finding their own. With that said, however, whatever happens after scientists do find dark matter remains unknown, since their latest effort to find it has ended in failure.
The ongoing search for dark matter, the plentiful stuff that helps galaxies like ours form, has been a tale of intrigue and "failure." Despite the invisible substance making up more than four-fifths of the universe's matter, scientists — who have been on the hunt for the substance using the LUX dark-matter detector — have yet to find it.
Unfortunately, today (July 21) marked their latest failure, when researchers who had spent time underground from 2014 to 2016 in a former gold mine in Lead, S.D., announced at the 11th Identification of Dark Matter Conference in England, that they failed to directly observe dark matter despite using equipment that exceeded technological goals in a project that cost $10 million to implement.
"LUX has delivered the world's best search sensitivity since its first run in 2013," Rick Gaitskell, a physicist at Brown University and spokesman for LUX, said in a statement. "With this final result from the 2014 to 2016 search, the scientists of the LUX Collaboration have pushed the sensitivity of the instrument to a final performance level that is four times better than the original project goals."
LUX, short for the Large Underground Xenon dark-matter experiment, is suspended in a 72,000-gallon tank of purified water, while a six-foot-tall titanium tank holds one-third of a ton of frigid liquid xenon. The goal is for the xenon to light up when a dark matter particle collides with one of its atoms, while the water and rock surrounding the area prevent anything else from getting in and potentially tampering with it.
The experiment was designed to look for weakly-interacting massive particles or WIMPs, which is one of the key theories behind dark matter particles. Simply put, WIMP theory suggests dark matter particles emerge following a process called supersymmetry — where every particle has a partner particle to accompany it.
The result? Nothing with the right properties to excite the xenon made it through.
"It would have been marvelous if the improved sensitivity had also delivered a clear dark-matter signal," Gaitskell added. "However, what we have observed is consistent with background alone."
However, just because LUX didn't detect any dark matter, that doesn't mean the experiment itself was a wasted effort — just that researchers failed on their initial objective. The results of this experiment suggest that dark matter doesn't have mass or an effect on ordinary matter within a certain range, and narrows down the possible characteristics of the substance to consider during future of experiments.
There is no doubt that there will be future experiments. Scientists are already starting to make adjustments to the South Dakota mine site for an improved version of the LUX, called LZ, which will be 70 times more sensitive. Operations for that should start in 2020, according to Brown University's Richard Gaitskell, another scientific spokesman for LUX.
In the meantime, there are experiments at other sites that also aim to grab ahold of dark matter — albeit through different methods, such as the one at Large Hadron Collider, which has a chance to create dark matter and then detect its signal.
