Does dark matter hold our universe together?

So far no one knows … not even what it is …

If you go outside on a dark night, in the darkest places on Earth, you can see as many as 9,000 stars. They appear as tiny points of light, but they are massive infernos. And while these stars seem astonishingly numerous to our eyes, they represent just the tiniest fraction of all the stars in our galaxy, let alone the universe. The beautiful challenge of stargazing is keeping this all in mind: Every small thing we see in the night sky is immense, but what’s even more immense is the unseen, the unknown. I’ve been thinking about this feeling — the awesome, terrifying feeling of smallness, of the extreme contrast of the big and small — while reporting on one of the greatest mysteries in science for Unexplainable.

It turns out all the stars in all the galaxies, in all the universe, barely even begin to account for all the stuff of the universe. Most of the matter in the universe is actually unseeable, untouchable, and, to this day, undiscovered. Scientists call this unexplained stuff “dark matter,” and they believe there’s five times more of it in the universe than normal matter — the stuff that makes up you and me, stars, planets, black holes, and everything we can see in the night sky or touch here on Earth. It’s strange even calling all that “normal” matter, because in the grand scheme of the cosmos, normal matter is the rare stuff. But to this day, no one knows what dark matter actually is.

“I think it gives you intellectual and kind of epistemic humility — that we are simultaneously, super insignificant, a tiny, tiny speck of the universe,” Priya Natarajan, a Yale physicist and dark matter expert, said on a recent phone call. “But on the other hand, we have brains in our skulls that are like these tiny, gelatinous cantaloupes, and we have figured all of this out.”

The story of dark matter is a reminder that whatever we know, whatever truth about the universe we have acquired as individuals or as society, is insignificant compared to what we have not yet explained. It’s also a reminder that, often, in order to discover something true, the first thing we need to do is account for what we don’t know. Link

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