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Dark Matter and Dark Energy Mysteries: Do Neutrons

Hold the Key?

By Charles Q. Choi, Space.com Contributor | April 30, 2014 07:01am ET

Neutrons bouncing in Earth's gravity are helping to shed light on two of the

greatest mysteries in the universe, dark matter and dark energy, researchers say.

Dark matter is an invisible substance thought to make up five-sixths of all matter in

the universe. The strength of its gravitational pull apparently helps keep galaxies

from spinning apart at the speeds at which they whirl.

Dark energy, on the other hand, is the mysterious stuff that scientists believe is

pushing the universe apart, driving up the rate at which the cosmos expands.

Investigators suggest dark energy could make up about 70 percent of the universe.

[The Strangest Things in Space]

Altogether, the particles known to science make up just about 5 percent of the mass

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Credit: Karl Tate,

SPACE.com Infographics

Artist


Astronomers know more

about what dark matter is

not than what it actually is.

See what scientists know

about dark matter in this

SPACE.com infographic.

and energy of the universe. What dark matter and dark energy actually are remains a mystery, but physicists have suggested

many potential explanations for both.

One candidate for dark matter is a set of particles known as axions. Theoretical physicists originally proposed axions to help

solve a puzzle regarding the strong nuclear force, which binds protons and neutrons together into atomic nuclei.

A potential explanation for dark energy involves quintessence theories, named after Aristotle's "quintessence," a fifth element

in addition to the four classical elements of air, fire, earth and water. These theories suggest that an unknown field that interacts

with matter permeates seemingly empty space. Prominent quintessence candidates include "chameleon fields" that grow weaker

around relatively dense objects such as planets and stars, potentially explaining why investigators have not detected these

fields.

If new kinds of particles or additional forces of nature exist, researchers might be able to observe them anywhere, including on

Earth. Neutrons are perfect for this kind of research; since they carry no electric charge, they are generally influenced only by

gravity, and possibly by additional, currently unknown, particles and forces.

Scientists developed an extremely sensitive instrument to monitor the movement of neutrons in Earth's gravitational field. This

method relies on neutrons cooled to minus 423 degrees Fahrenheit (minus 253 degrees Celsius), gathered from the strongest

continuous source of ultra-cold neutrons in the world at the Institut Laue-Langevin in Grenoble, France.

The neutrons move at speeds of less than about 17.9 mph (28.8 km/h) in a vacuum between two horizontal plates made of a

well-polished glass that reflects the particles. The researchers make the "mirrors" vibrate 280 times per second, imparting the

neutrons with specific amounts of energy.


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Credit: TU Vienna


The gravity

resonance

spectrometer at the Vienna

University of Technology

used to study neutron

behavior to glean insights

into dark matter and dark

energy.

A neutron detector analyzes the energy of the neutrons as they exit from between the mirrors. The scientists know how much

energy the neutrons should have while they experience the gravity of the Earth . If the scientists find any discrepancy in the

energy of the neutrons, this may come from dark energy or dark matter interacting with those neutrons.

"It's like watching a bouncing ball fall and, with a new quantum technique, looking for any effects dark energy or dark matter

scenarios could have," said study author Hartmut Abele, an experimental physicist at the Vienna University of Technology.

The researchers measured the effects of gravity on neutrons with a sensitivity 100,000 times greater than in previous

experiments. They did not detect any deviations from Newton's well-established law of gravity.

These findings "cut off about half the parameter space" or potential scenarios that scientists have to examine involving

chameleon fields, Abele told Space.com. The results also placed significant limits on how much the axion might interact with

matter, Abele said.

Improving the sensitivity of these experiments could help confirm whether or not chameleon fields exist. The researchers

plan to increase the accuracy of their device by another few orders of magnitude, Abele said.

The scientists detailed their findings online April 16 in the journal Physical Review Letters.

Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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Kent Nebergall · Top Commenter · Judson University

I love the pure science of this. Neutrons are not impacted by electrical fields. Dark matter is dark(relatively unobservable) because it also lacks such interactions. So flock the birds we understandwith the ones we don't understand, and measure them against the "wind" (force) that impacts both(gravity). And they are not looking for anything more profound so far than to expand theobservable limits, and do observation within those limits, to see if there is signal in the noise.Note that with various secondary particles from cosmic rays and so on, they will never get a fully,fully pure signal. But they can get as close as the universe allows, and know the difference. Sowhile the experiment still has to deal with the world we have (noisy), the science itself, like puremath, can stay above the fray. Just beautiful.

Reply · Like · · 11 hours ago2

Jeffrey Patten · Top Commenter · Research Assistant at Law Offices

I agree. Also, many people have been complaining that most of the articles onSpace.com are "dumbed down" for too broad of an audience; Well, this article (and thearticle on black hole atoms posted at about the same time) are both quitesophisticated. Moreover, the comments posted by many people are way over myhead, which I LOVE; it challenges me to read up and learn more. Keep it up, guys.

Reply · Like · 7 hours ago

Bryan Swift · Top Commenter

Always push the envelope Jeffrey. Wish many others would do the same. I've beenable to teach myself more than anyone has been able to teach me. Sorry all you"teachers" in my past. You did very little for me.


David Carlson · Top Commenter

Solved?!

Bok globules as dark-matter reservoirs of luminous matter: Bok Globules = Dark Matter

Scientists assume Bok globules are 'proto-protostars' in the process of formation which is hard tosupport since Bok globules are the coldest objects in the natural Universe, so maybe we'relooking at them through the wrong end of the telescope—

What if Bok globules condensed a majority of the matter in the early Universe following the DarkAges by phase-change nucleations in galaxy-sized atomic-hydrogen aggregates, endothermicallyclamping the temperature as atomic hydrogen reverted to plasma, promoting gas densificationinto globules.

As the coldest objects in the sky, Bok globules are invisible and thus dark except when highlightedinside glowing nebulae or when they sprout cometary tails evaporated by nearby OB supergiants.

A... See More


Stacy Fisher · Top Commenter · Writer/Proofreader/Photographer at Mountain Valley

Living Magazine

It has the hallmarks of a viable hypothesis. A theory needs to be based on factsderived from experiment and a confirmation process.

Reply · Like · · 10 hours ago2

Jeffrey Patten · Top Commenter · Research Assistant at Law Offices

Stacy Fisher - ...so one would have to come up with observations that would confirmor refute the hypothesis. If there are any stars close enough to observed Bok globulesto be affected by their gravity, we could measure their movement over time to see ifthe gravity of the Bok globules is what is predicted by current theories, or if they havegreater gravitational attraction consistent with Cartson's hypothesis.


David Carlson · Top Commenter

Jeffrey PattenWe know their individual masses (2-50 stellar masses). What we don't know is their


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dark matter and dark energy mysteries_ do neutrons hold the key_ _ space

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