The EOR will also provide an unprecedented test for the current best model of cosmic evolution. Although there is plenty of evidence for dark matter, nobody has identified exactly what it is. Signals from the EOR would help to indicate whether dark matter consists of relatively sluggish, or ‘cold’, particles — the model that is currently favoured — or ‘warm’ ones that are lighter and faster, says Anna Bonaldi, an astrophysicist at the Square Kilometre Array (SKA) Organisation near Manchester, UK. “The exact nature of dark matter is one of the things at stake,” she says.
Radioastronomers look to hydrogen for insights into the Universe’s first billion years.