LHC restart could help with dark matter
The restart of the Large Hadron Collider (LHC) is now under way for the first time since 2013.
It's the world's biggest experiment and scientists hope will lead to a deeper understanding of how the universe works.
For the last two years, physicists have been working on an upgrade to the giant machine.
The LHC is a 16-mile-long tunnel, which sits 100m below ground on the border between France and Switzerland.
Tim O'Brien is a professor of astrophysics from the Jodrell Bank observatory. He says the most exciting discovery could be dark matter.