Traces of 'dark matter' discovered 2,000ft below the ground

Scientists may have caught their first ever glimpse of "dark matter" - the mysterious, invisible substance that makes up three quarters of the matter of the universe.



Traces of two "dark matter particles" were picked up by highly sensitive detectors buried 2,000 ft below the ground at the bottom of an old iron mine, researchers report today.



The scientists say there is a three in four chance that the observations are genuine particles of dark matter, rather than just background noise.

Discovery: Scientists believe they have found particles of 'dark matter', illustrated here in a computer-generated image (the 'dark matter' is in pink)

Dark matter is one of the big mysteries of physics and its discovery would be one of the greatest scientific breakthroughs of the last 100 years.



In the 1930s astronomers first realised that the stars, gas and dust only made up a fraction of the matter of the universe. They concluded that galaxies would fall apart unless they were held in place by the gravitational pull of some vast, invisible substance.



For more than 80 years, scientists have debated what this dark matter could be and why we can't see it.



One of the most likely candidates is a tiny object called a "weakly interactive massive particle" or Wimp which bombards the earth from space.

Researchers have been looking for traces of Wimps for the last nine years at the bottom of a disused Soudan iron mine in Minnesota.



The experiment uses 30 detectors, frozen to minus 273.1C designed to spot the traces of Wimps after they have bounced into an ordinary atom.



The experiment is buried so deep because Wimps - unlike particles from space - can pass straight through the thick layers of earth and rock.

The researchers report in the journal Science that they have spotted two traces of Wimps. However, they need to find more before they can be certain they have found the elusive dark matter particle.



Dr Tarek Saab, from the University of Florida at Gainesville, said: 'Many people believe we are extremely close - not just us, but other experiments. It is expected or certainly hoped that in the next five years or so, someone will see a clear signal.'

But he acknowledged the current evidence was not quite strong enough.

'With one or two events, it's tough,' he said. 'The numbers are too small.'

