The Cosmic Ray Extremely Distributed Observatory (CREDO) project is testing one of the many theories for what this dark matter could be – supermassive particles born in the early universe. If this theory is correct, we can’t see the supermassive particles themselves, but we should be able to detect what is left when these particles come to the end of their lives, or "decay". From experiments with high-energy particles carried out on the Earth we know that the interactions with other particles is likely to result in lots of lower-energy photons being produced in a large "cascade". CREDO refers to these cascades as super-preshowers and they have the potential to be widely distributed across both space (an area larger than the Earth) and time (reaching different parts of the Earth at different times). To identify these widely distributed showers we’d need a detector the size of the Earth which is clearly not possible! However, what we can do, with your help, is have lots and lots of little detectors spread out across the Earth’s surface. CREDO detector smartphone application: The app uses your smartphone camera (while your phone is charging and the camera is covered) to look for the bright pixels caused by the impact of a high-energy particle on the CCD detector in the camera. A small "thumbnail" centered on this detection along with the time and date it occurred and where your smartphone was is sent to the CREDO servers. Whether you have a smartphone or not there are still many ways you can get involved in CREDO: With a large number of smartphones detecting particle impacts its important to filter through these images to determine the type of particle detected and also to look out for any unexpected detections. Eventually, a lot of this analysis will be carried out by computers but we need to train the computers to do this. You can therefore use the Private Particle Detective Experiment here (under development) to start to follow your particle detections (if you also have the CREDO app) through the analysis process.