The dark matter pelting your body right now: A guide

The Week's Editorial Staff
The Week

Groundbreaking new research suggests that the universe's most mysterious substance is hitting the human body at a much higher rate than previously thought

Particles known as dark matter are flying through your body as often as once per minute, claims new research. Old theories suggested that these particles collided with particles in our body maybe once in a lifetime, but now, a team of experts are arguing that the previous estimates were way too low. Here's what you should know:

What is dark matter?
Think of dark matter as the invisible glue that holds the cosmos together, allowing things like fast-spinning galaxies to retain their shape. Evidence of dark matter's existence first emerged in the 1930s, when researchers tried to calculate the total mass of far-off solar systems by analyzing their rotation rates. Physical things, like planets and stars, were accounted for in the formula. But when all that visible stuff was tallied, the total mass didn't quite add up. That's where dark matter comes in, which physicists use to fill in mathematical gaps. The mystery particles are thought to comprise as much as 80 percent of the universe around us.

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And the particles are hitting us?
That's correct. The Earth is currently flying through a sea of dark matter. Here's the thing, though: No one has been able to pinpoint exactly what dark matter is, says Jason Major at National Geographic. Out of known particles, there are a few that scientists think may comprise dark matter. One particle group — known as Weakly Interactive Massive Particles, or WIMPs — is the likely culprit according to new computer models that suggest these WIMPs "are streaming through Earth and its inhabitants every second."

How did they figure that out?
Normally, WIMPs don't interact much with normal matter, and usually "zip straight through most of the stuff in the universe, including people," says National Geographic's Major. But sometimes wayward WIMPs collide with other particles, releasing energy that scientists can quantifiably measure. Experts used to think that perhaps a WIMP particle collided with something in the human body, like an H2O molecule, just once in a person's lifetime. In this new experiment, however, scientists found that hundreds of thousands of WIMPs collide with our body annually. It might even be "as many as one per minute," Katherine Freese, one of the researchers tells

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Is that bad for us?
Not at all. Even though "WIMPs are clearly a source of radiation," says Freese, the energy released from these impacts is unlikely to cause cancer. "Other naturally occurring sources of radiation, from radon and cosmic rays, are a much larger problem for us." In other words, don't fear the dark matter. 

And scientists really believe in dark matter?
The concept of dark matter was deemed ludicrous for a long time. But by the 1980s, "the vast majority of scientists were on board with the idea, nutty though it may seem," says Michael D. Lemonick at TIME, "and there they've remained ever since."

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Sources: National Geographic,, Technology Review, TIME

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