14 DAY TRIAL // Dark matter is accepted as fact these days, but we haven't been able to observe it directly, since its very nature makes it unobservable. We have seen its effects on the universe though and we know that it's a huge chunk, more than a quarter, of what the universe is made up of.
But we're now seeing the first actual hints of its existence, the initial results from the Alpha Magnetic Spectrometer experiment are in line with predictions, which would suggest the existence of dark matter and that provides some idea of its properties.
The Alpha Magnetic Spectrometer experiment is bolted to one side of the International Space Station. It's been there for the past couple of years collecting data.
Scientists believe that dark matter particles, WIMPs (weakly interacting massive particles) are their own antiparticle and as such annihilate each other when they collide.
This annihilation should result in a steady source of gamma rays or particle-antiparticle pairs of Standard Model particles.
The AMS is designed to detect such positron-electron pairs and so far it counted some 400,000 positrons hitting its detectors.
These types of pairs can be created by other phenomena in the universe, but the AMS has seen them come from all around not from one particular direction indicating that they are the result of dark matter collisions.
But the data gathered so far is too little to draw a conclusion, physicists can't say WIMPs exist no more than they can say they don't exist, based on what's been observed so far. What they can say is that they could exist.
The data does show an excess of positrons, consistent with predictions, over the 0.5 to 350 GeV energy spectrum the AMS is designed to detect.
But scientists are looking for a very distinct pattern in the energy distribution, they should see a fast increase in positron numbers around a certain energy level, indicating a WIMP's mass, and then a sharp decrease past that energy level.
This hasn't been observed and it may take a few more years of observations before the pattern emerges, if indeed it is there.