Scientists may finally shine a light on dark matter

Physicists have puzzled for decades about a form of matter that makes up 90 percent of galaxies, including our own Milky Way, but which they've never seen.

Now they may finally have solved the mystery of this "dark matter." 

The answer may come from Sam Ting, a Nobel laureate in physics who recently said of a forthcoming research paper on the nature of dark matter, likely to be published this month, "It will not be a minor paper."

Physicists who met this past weekend for a dark matter workshop at Texas A&M University certainly hope so.

Many have always been uncomfortable not knowing what - something that heretofore has been invisible and undetectable - accounts for 90 percent of the stuff in the universe.

Scientists know dark matter exists because without it they cannot explain why galaxies, which zip through space at enormous speeds, do not fly apart and instead remain a cohesive unit. Of the matter astronomers can observe, there simply isn't enough gravity to hold galaxies together.

In fact, it's likely that without this dark matter galaxies might never have formed at all. Space is mostly empty. Only in places where there is sufficient stuff - matter - do clumps form and gravitationally attract other matter.

Without dark matter, physicists say, there might not have been enough matter to clump together to form galaxies and stars.

Because of dark matter's centrality to our understanding of the cosmos, it's a bit frustrating for an eminent physicist like Bhaskar Dutta, at Texas A&M, to have to admit, "We still don't know what the nature of dark matter is, nor what the origin of dark matter is."

A large, white can

So, does Sam Ting, an MIT physicist, now have the answer?

In May 2011, a NASA space shuttle installed the Alpha Magnetic Spectrometer to the exterior of the International Space Station. It's not a sexy instrument from the outside. It looks like a large, white can.

But inside this $1.5 billion instrument, which Ting led the development of over a 15-year period, are extremely sensitive magnets and detectors that can collect and sort through millions of cosmic ray impacts a day.

Physicists believe some of these cosmic rays might be the result of collisions by dark matter particles, and it's likely that Ting has found what he believes are the signatures of these collisions. The forthcoming research paper represents the first findings from the instrument.

A matter of perspective

Once Ting publishes his research paper, Dutta said, scientists will seek to rule out other explanations for what Ting has observed. If all other phenomena can be ruled out, then dark matter will be what's left as an explanation.

And while it may be frustrating to scientists that they don't yet understand such a fundamental component of the universe, Dutta offered some perspective.

It's taken humans a long time to understand ordinary matter, he said, referring to the matter we're familiar with - stars and planets.

In ancient times people believed there were four elements, earth, air, fire and water. During the Enlightenment scientists began to discern and describe various elements and developed the Periodic Table of chemical elements. Then, during the 20th century, scientists discovered that individual atoms were not finite, and instead made of smaller components, called quarks, and other mysterious particles.

"It took us many thousands of years to understand the nature of ordinary matter," Dutta said. "I'm hopeful we can understand dark matter in a shorter number of years."

Editor's Note: Bhaskar Dutta is the interim director of the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University.

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