Access to dark matter - a sign inside Boulby Potash mine
A group of British scientists is currently working at the bottom of Boulby Potash mine, hoping to be the first people in history to find dark matter.
They use a super-sensitive detector called Zeplin III, which they hope will be able to detect the dark matter and prove its existence.
They chose the spot, well below the sea bed just off the Cleveland and North Yorkshire Coast, as it's far from any background radiation, that would interfere with their tests.
What's it all about?
In short, if you do the maths on the universe, something strange happens. No matter how many times you check the figures, the answer always comes out the same... the Universe should weigh a lot more than it does.
Two scientists working in the mine, looking for dark matter
The best explanation scientists can come up with is that there is a lot of "stuff" in the universe that we can't see or hear or touch, but which makes up for that extra weight. They call this stuff "dark matter".
The trouble is, if you can't see or hear or touch it - how do you prove it is there?
Experiments at CERN
You may have heard of dark matter in the news, as the team running the Large Hadron Collider at CERN (the European Organization for Nuclear Research) are also looking for it.
They're looking for it in a very different way - by using their huge particle accelerator to smash atoms into each other and artificially create dark matter.
But the British team, who are looking for the naturally occurring stuff, think they'll find it first.