new bits of antimatter can be created within our galaxy in certain kinds of events. One way is if two particles of dark matter collide.Dark matter emits and absorbs no light, and interacts with ordinary matter in a ghostly fashion, primarily through gravity. Dark matter affects the way galaxies move; they rotate in a manner that suggests that they are carrying some unseen load of matter.In the past two decades, other experiments and detectors have bolstered the notion that dark matter is far more abundant than ordinary matter. What it is, exactly, remains unclear. The AMS, however, has picked up signals from more than 400,000 positrons, and they came into the detector from all directions, with no variation over time. That is consistent with the idea that they are coming from collisions of particles of dark matter that saturate the galaxy.The other possible origin is that positrons are emitted by rapidly rotating, ultra-dense stars called pulsars, which are scattered throughout the galaxy. Ting said Wednesday that his results cannot rule out that possibility.