Physicists have long suspected that there might be a mysterious type of matter in the universe unlike that of our own physical world. Dark matter, as it’s known, is estimated to make up somewhere between twenty-five and eighty percent of all the matter and energy in the universe, depending on which physicist you ask.
Dark matter gets its name from the fact that it does not interact with light or other forms of radiation like electromagnetism. Although this mysterious cosmic building block has never been directly observed, its presence is inferred from background radiation and gravitational interference.
To help search for this strange ‘missing ingredient’ of the universe, scientists built an unbelievably high-tech research facility a mile beneath the Black Hills mountain range of South Dakota called the Sanford Underground Research Facility. The main instrument used in this search is a supersensitive tank of liquid xenon that emits small bursts of light and electricity when struck by subatomic particles. To protect against interference from any forms of outside energy or radiation, the xenon tank is housed in a vast 72,000-gallon tank of water.
A twenty-month-long research project called the Large Underground Xenon (LUX) dark matter experiment that took place in the subterranean lab concluded this year. The results from this search were recently presented at the 2016 International Dark Matter Conference in Sheffield, U.K.
Unfortunately for hopeful physics nerds everywhere, the results were inconclusive. According to Rick Gaitskell, physicist at Brown University and co-spokesperson for the LUX experiment, despite the lab equipment having performed marvelously, the results were highly disappointing:
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. It would have been marvelous if the improved sensitivity had also delivered a clear dark matter signal. However, what we have observed is consistent with background alone.
Even though this experiment was inconclusive, researchers are still hopeful. Simon Fiorucci, physicist at Lawrence Berkeley National Laboratory and science manager for the experiment, believes the inconclusive data at least demonstrates the viability of the lab:
The result is unambiguous data we can be proud of and a timely result in this very competitive field—even if it is not the positive detection we were all hoping for.
Most scientists believe the Large Hadron Collider (LHC) at CERN has the best chances of discovering dark matter particles due to the sheer scale of the instruments there, although further experiments are already being planned at LUX to keep the search for elusive dark matter alive.
While this experiment hasn’t conclusively turned up any evidence of dark matter, there is still much data to process and the LUX instruments are now fine-tuned and calibrated for future experiments. So chin up, physics nerds: the search for dark matter goes on.