The goal was to find the first light that ever existed in the universe: the moment the first stars “turned on” and the universe went from dark to light. After a decade of searching, a team of radio astronomers finally found the signal—a dip in an absorption spectrum—set off by these first stars. This discovery, if confirmed by outside experiments, is momentous in itself.
But there was something else.
The signal was more than double what models predicted, suggesting that gas at the dawn of the universe was colder than anyone expected. The culprit? Possibly dark matter—bumping against the gas, cooling it down.
If true, this could be the first evidence that dark matter—which scientists know little about—is made of particles. Now, decades since dark matter was discovered through the effects of its gravity, this may help researchers figure out how to search for it.