The cosmos should be ringing with dark sound, according to a recent model of dark matter that says some of the elusive particles can form unseen atoms. Now efforts to eavesdrop are refining our picture of this "shadow universe".
Dark matter is believed to make up about 80 per cent of the matter in the universe, based on its gravitational effects on visible matter. The leading candidates for the elusive stuff are weakly interacting massive particles (WIMPs), which would only interact with normal matter via gravity and the weak force.
Most models suggest that WIMPs don't interact with themselves to build larger structures, the way that normal matter does. But earlier this year, scientists proposed a model in which 15 per cent of dark matter can build dark atoms and larger structures, including shadow versions of galaxies.
If so, we should be able to see evidence for dark matter interactions in the large-scale structure of the universe, says Francis-Yan Cyr-Racine at the Jet Propulsion Laboratory in Pasadena, California. In the heat of the very early universe, matter existed as dense, soupy plasma. As things cooled, denser regions started to collapse, which set the gas ringing.To read more, click here.