The combined gravity of all the regular and dark matter trapped inside the cluster shown here warps space-time. It also affects light traveling through the cluster toward Earth, distorting images of the remote galaxies behind the cluster.
NASA, ESA, and J. Lotz and the HFF Team (STScI)
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NASA, ESA, and J. Lotz and the HFF Team (STScI)
The combined gravity of all the regular and dark matter trapped inside the cluster shown here warps space-time. It also affects light traveling through the cluster toward Earth, distorting images of the remote galaxies behind the cluster.
NASA, ESA, and J. Lotz and the HFF Team (STScI)
Physics has a bit of a messy problem: There’s matter missing in our universe.
Something is there that we can’t see, but scientists can detect.
“When we look at how stars move in galaxies, they move as if there is a lot of matter there that we can’t see,” says Chanda Prescod-Weinstein, a theoretical particle physicist at the University of New Hampshire.
This missing matter is often called called dark matter. It makes up over a quarter of the matter in the universe.
Scientists don’t know what it is.
Yet scientists do know that whatever this matter is has to have a few key components:
- It can’t interact with light, meaning it should be essentially transparent or invisible.
- It should move relatively slowly. That’s because, if it moved quickly, it wouldn’t clump together under gravity and help form galaxies.
So what could this mysterious substance be? Some researchers like Prescod-Weinstein think a hypothetical particle called the axion may help make the dark matter problem a little … tidier.
That’s right: hypothetical. Meaning scientists have never seen one, and don’t know if they exist. But if they are detected one day, scientists think they could be the answer to this longstanding mystery.
Fascinated by the mysteries of our universe? Email us at shortwave@npr.org to let us know which mystery we should cover next.
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This episode was produced by Rachel Carlson, edited by Rebecca Ramirez and fact-checked by Tyler Jones. Robert Rodriguez was the audio engineer.
