Particle Physics / The Cosmos


What is Dark Matter? A New Clue

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.

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Greg Kestin

    Greg Kestin holds a faculty position at Harvard University, where he conducts theoretical physics research, teaches, and produces educational online content. He earned his physics Ph.D. from Harvard, as a member of The Center for the Fundamental Laws of Nature, focusing on theoretical particle physics and quantum field theory. Over his career, he has also conducted research in nuclear physics, fusion energy, and gravitational wave physics. For over a decade he has been involved with innovative educational outreach endeavors, bringing science to both students and members of the public through his writings, videos, lectures, and multimedia.