The LHC , a 27km ( 17 mile ) particle accelerator , is ready to fire up again after a two-year upgrade . After nailing down the elusive Higgs boson particle in 2013 , physicists are now on the trail of dark matter . Dark matter has never been observed , but it makes up about 85 percent of all the matter in the universe .
The LHC , a 27km ( 17 mile ) particle accelerator , is ready to fire up again after a two-year upgrade . After nailing down the elusive Higgs boson particle in 2013 , physicists are now on the trail of dark matter . Dark matter has never been observed , but it makes up nearly 85 percent of all the matter in the universe .