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The force is with them

Physics experiment may help explain expansion of the universe

Associate Professor of Physics Roberto Onofrio works to understand the forces in action in the universe due to quantum theory. In a paper published in the November issue of Physical Review A, he outlined an experiment that may reveal the origin of those forces. Onofrio and his co-investigators, Michael Brown-Hayes and W.J. "Andy" Kim (both graduate students), D.A.R. Dalvit of the Los Alamos National Laboratory and F.D. Mazzitelli of the Universidad de Buenos Aires, propose an experiment that may show that the energy causing the universe to expand at an accelerating rate comes from the properties of quantum vacuum.

Roberto Onofrio and graduate student Michael Brown-Hayes
Roberto Onofrio (left) and graduate student Michael Brown-Hayes with the vacuum chamber they are using to measure the Casimir force. They hope the results will lead to answers about the forces propelling the expansion of the universe. (Photo by Joseph Mehling '69)

Quantum theory is based on the principle that matter and energy have the properties of both particles and waves, and that fluctuating particles and fields are present everywhere. One current challenge of quantum theory is finding a way to explain how the universe is both expanding and accelerating and to discover the source of the energy needed for that acceleration.

Onofrio and his team plan to use a phenomenon known as the Casimir effect, first predicted in 1948 by Dutch physicist Hendrik Casimir. The Casimir effect holds that two surfaces in a vacuum will be mutually attracted to each other due to minor fluctuations that occur. The study published in Physical Review A describes an apparatus Onofrio and his team recently developed to obtain more precise measurements, in a larger range of distances, of this attractive force, known as the Casimir force. By measuring the Casimir force with greater precision than ever before, Onofrio hopes to show that quantum fluctuations within a vacuum account for the apparent introduction of the energy that seems to propel the expanding universe. Also working with Onofrio and his team is physics major Scott Middleman '06.

The apparatus for measuring the Casimir effect is housed within a controlled environment - a vacuum chamber with every possible form of interference removed. The hope is that in this airless, empty space, the most fundamental forces in the universe will reveal themselves and, from a tiny chamber in a Dartmouth physics lab, the engine of the accelerating universe will make itself known.

Onofrio, who reported on this experiment at the workshop QFEXT'05 held in Barcelona in early September, called the experiment "a step forward to observe the effects of quantum vacuum with table-top experiments, with all the related cosmological implications due to the accelerating universe." The final steps of the experiment are scheduled to begin in the coming months.

By GENEVIEVE HAAS


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Last Updated: 12/17/08