"Nature plays the tricks that it knows how to play over and over again," said Nagel, the Stein Freiler Distinguished Service Professor in Physics at Chicago. Nagel and Jaeger co-authored the paper, along with Xiang Cheng, a graduate student in physics at Chicago; German Varas, a graduate student in physics at the University of Chile; and Daniel Citron, a Chicago undergraduate in physics.
Scientists have attained a good understanding of equilibrium phenomena, which are governed primarily by temperature or pressure. But what about phenomena that have been pushed far beyond their equilibrium states, like a jet of sand" What about quark-gluon plasma, the mixture of subatomic particles that existed for perhaps a few millionths of a second after the big bang"
"We really don't know what the right concepts are to describe this," Nagel said. "We love the physics of granular material because it allows us entrée into this question in relatively simple experiments."
In designing their tabletop experiment, the Chicago team addressed a fundamental question about equilibrium: Under what conditions does a collection of molecules, sand grains or other particles behave like a liquid" Macroscopic and subatomic particles sometimes behave in similar ways. The particles in the Chicago experiment are large enough to allow scientists to track under precisely controlled conditions, an option not available on the subatomic scale.
A paper published in 1883 that described the water-bell phenomenon inspired the granular-stream experiment. The paper reports how a stream of water hitting a narrow, flat, circular target becomes transformed into the thin, hollow shape of a bell. Would a stream of granular materials do likewise"
Cheng, the Chicago graduate student, performed an experiment to find out. He blasted globs of glass and copper beads through a tube into a flat target. "The answer is you can in fact see those bells," said Jaeger, a Professor in Physics. "Specifically, we find that the rapid collisions of densely packed particles produce the liquid state that we can then observe afterward, when everything flies apart and produces these beautiful envelope structures."
Scientists have seen similar structures in the quark-gluon plasma experiments conducted at Brookhaven National Laboratory with the Relativistic Heavy Ion Collider. The $500 million RHIC smashes gold atoms into each other at nearly the speed of light. The tabletop Chicago experiment launches jets of granular materials into a flat target at no more than 12 miles an hour.
"There couldn't be anything farther apart than our experiments and those at RHIC," Nagel said. For that very reason, the Chicago team conducted their test under a variety of conditions to ensure that interactions between the granular particles and the air did not affect the experimental result. "The key ingredient is the high density of rapid collisions," Jaeger said.
The similarity between the granular-jet and RHIC experiments are surprising because scientists would expect quantum physics to dominate the results of the latter. Quantum physics typically rules the atomic and subatomic world. Classical physics, meanwhile, applies to the much larger objects of everyday life.
Nevertheless, the RHIC scientists have interpreted their results in a classical way. "They say it's like a liquid. That's a classical concept. Then they ascribe to this liquid such things as viscosity. Well, that's a classical concept," Nagel said. "Some of these phenomena that appear at this very microscopic, quantum scale echo phenomena that occur on the classical scale.
Source: University of Chicago
Related stories:
Solar Wind Challenge: Two BU Astronomers Research Profs Will Debate Differing Theories Of Origin
The solar wind -- a stream of electrically-charged particles and magnetic fields that blows outward from the sun and streams past Earth and through the solar system in all directions at speeds of a million miles per hour -- continues to baffle scientists 50 years after its initial discovery.
Physicists: After 30 years of study, rare particle confirms prediction
High-energy physicists devoted to recreating the conditions at the beginning of the universe have for the first time observed a new way to produce those basic particles of atoms, protons and neutrons.
Brain waves pattern themselves after rhythms of nature
The same rules of physics that govern molecules as they condense from gas to liquid, or freeze from liquid to solid, also apply to the activity patterns of neurons in the human brain. University of Chicago mathematician Jack Cowan will offer this and related insights on the physics of brain activity this week in Boston during the annual meeting of the American Association for the Advancement of Science.
COUPP experiment tightens limits on dark matter
Scientists working on the COUPP experiment at the Department of Energy’s Fermi National Accelerator Laboratory today announced a new development in the quest to observe dark matter. The Chicagoland Observatory for Underground Particle Physics experiment tightened constraints on the “spin-dependent” properties of WIMPS, weakly interacting massive particles that are candidates for dark matter. Their results, combined with the findings of other dark matter searches, contradict the claims for the observation of such particles by the Dark Matter experiment (DAMA) in Italy and further restrict the hunting ground for physicists to track their dark matter quarry.
Revolution in understanding of ion channel regulation
A study at Rush University Medical Center in Chicago published this week in the online version of
Biophysical Journal proposes that bubbles may control the opening and closing of ion channels. This new understanding of the channels that control much of life in health and disease provides a vital piece of the molecular puzzle.
Radiation flashes may help crack cosmic mystery
Faint, fleeting blue flashes of radiation emitted by particles that travel faster than the speed of light through the atmosphere may help scientists solve one of the oldest mysteries in astrophysics.
Can this experiment identify dark matter?
"The key question we want to tackle," Gianfranco Bertone tells
PhysOrg.com, "is what dark matter is."
Physics world shifts focus to Switzerland
Scientists at Fermilab in Illinois are racing to find the elusive Higgs boson particle before a giant new Swiss lab opens next year.
