A new telescope could detect decaying dark matter in the early universe

Hydrogen is the most abundant element in the universe, by far. More than 90% of the atoms in the universe are hydrogen. Ten times the number of helium atoms, and a hundred times more than all other elements combined. It's everywhere, from the water in our oceans to the earliest regions of the Cosmic Dawn. Fortunately for astronomers, all this neutral hydrogen can emit a faint emission line of radio light.