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AUDIE CORNISH, HOST:

From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish.

ROBERT SIEGEL, HOST:

And I'm Robert Siegel.

Today, an international team of researchers announced that they may have seen hints of something called dark matter. Those hints came from an experiment on the International Space Station. As NPR's Geoff Brumfiel reports, the finding could be a milestone in the long search for the universe's missing material.

GEOFF BRUMFIEL, BYLINE: Only a tiny sliver of the stuff in the universe is visible to scientists. The rest is dark matter. Researchers don't know what it is, but they know it's there. Its gravity pulls on the things we can see. Michael Salamon is with the U.S. Department of Energy. He's part of the team behind the announcement.

MICHAEL SALAMON: We live in a sea of dark matter. Our galaxy is embedded in a huge roughly spherical halo of dark matter particles.

BRUMFIEL: He says that dark matter is beyond anything predicted by current scientific theories.

SALAMON: What that means is if we detect dark matter and learn something about its nature, we will have made a major impact to our understanding of physics and nature itself.

BRUMFIEL: That's a big part of why scientists from 16 countries spent $2 billion building a detector designed to pick up any hint of this mystery material. Their alpha magnetic spectrometer was carried into space two years ago and bolted onto the side of the International Space Station. Today, researchers announced the AMS had detected a large number of high-energy particles. These particles could be coming from collisions of dark matter. Theories suggest that when dark matter particles smash together, they annihilate each other. The enormous energy released creates visible particles, and it's these particles that might be showing up in the detector.

SAM TING: What we have shown today only represents less than 10 percent of the data.

BRUMFIEL: Nobel Prize winner Sam Ting is responsible for the AMS. Speaking from Geneva, he says that this is only the beginning. As the AMS collects more particles, it should be able to tell whether they are coming from dark matter collisions.

TING: I think with AMS, there's no question we are going to solve this problem.

BRUMFIEL: But it's also possible the particles could have come from somewhere else. Gregory Tarle is a physicist at the University of Michigan. Tarle says that the remains of certain dead stars can hurl the same kinds of particles into space.

GREGORY TARLE: The problem with all of these type of measurements is that they are not definitive for the discovery of dark matter annihilation.

BRUMFIEL: AMS leader Sam Ting says more data should help, and the experiment does have time on its side. It is expected to continue recording particles as long as the space station is operating. That's currently until 2020. Geoff Brumfiel, NPR News.

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