Deep inside an abandoned iron mine in northern Minnesota, physicists may have spotted the clearest signal yet of dark matter, the mysterious stuff that is thought to make up 90 per cent of the mass of the universe.
The Cryogenic Dark Matter Search (CDMS) collaboration has announced that its experiment has seen tantalising glimpses of what could be dark matter.
The CDMS-II experiment operates nearly three-quarters of a kilometre underground in the Soudan mine. It is looking for so-called weakly interacting massive particles (WIMPs), which are thought to make up dark matter.
The experiment consists of five stacks of detectors. Each stack contains six ultra-pure crystals of germanium or silicon at a temperature of 40 millikelvin, a touch above absolute zero. These are designed to detect dark matter particles by looking at the energy released when a particle smashes into a nucleus of germanium or silicon.
The problem is that many other particles – including cosmic rays and those emitted by the radioactivity of surrounding rock – can create signals in the detector that look like dark matter. So the experiment has been carefully designed to shield the crystals from such background "noise". The idea is that when the detector works for a long time without seeing any background particles, then if it does see something, it's most likely to be a dark matter particle.
The Cryogenic Dark Matter Search (CDMS) collaboration has announced that its experiment has seen tantalising glimpses of what could be dark matter.
The CDMS-II experiment operates nearly three-quarters of a kilometre underground in the Soudan mine. It is looking for so-called weakly interacting massive particles (WIMPs), which are thought to make up dark matter.
The experiment consists of five stacks of detectors. Each stack contains six ultra-pure crystals of germanium or silicon at a temperature of 40 millikelvin, a touch above absolute zero. These are designed to detect dark matter particles by looking at the energy released when a particle smashes into a nucleus of germanium or silicon.
The problem is that many other particles – including cosmic rays and those emitted by the radioactivity of surrounding rock – can create signals in the detector that look like dark matter. So the experiment has been carefully designed to shield the crystals from such background "noise". The idea is that when the detector works for a long time without seeing any background particles, then if it does see something, it's most likely to be a dark matter particle.