Research on action-at-a-distance theory continues at UNL

It's hard to imagine a world without Newton's Third Law — one where every action is not met with an equal and opposite reaction. It seems like the stuff of magic, conjuring images of a magician sliding objects across a table with nothing more than a few gestures.

Yet, according to Herman Batelaan, an associate professor of physics and astronomy at the University of Nebraska-Lincoln, that law may not hold true — at least not in the realm of quantum mechanics.

A 2007 experiment by Batelaan's group, which was featured on the most recent cover of Physics Today, showed that it is possible to move electrons with electromagnetic potentials, instead of the traditional way of meeting force fields.

The effect is called action-at-a-distance, a theory first proposed in 1959 by theorists Yakir Aharonov and David Bohm, which theorized particles can be influenced without an outside force.

"Think about a satellite in space," Batelaan explained of action-at-a-distance. "It looks like gravity from Earth is interacting instantaneously with the satellite … Now suppose you had a gravitational field and felt its effects somewhere with no gravitational field. With the Bohm effect, you have the effects of an electromagnetic field somewhere where there is nothing."

The original experiment, built on work conducted by Japanese researcher Akira Tonomura in 1986, involved creating an electromagnetic field to show that waves of electrons could be deflected without directly contacting it.

"You have to show that field is not at the electron itself," Batelaan said. "What we did for our part was measure if that electron is actually deflected or delayed. If there's wind, bullet deflects. Wind is force … If there is no force, there is no deflection. But still, something happens, and it's something that you can only see in quantum systems. You can see mag field acting somewhere that it's not."

The mysterious phenomenon grabbed the interest of the physics community. In addition to the cover of Physics Today, more than 2,500 published papers have commented on the two at-a-distance experiments.

Still, the practical applications remain uncertain. The effect could allow for easier detections of electromagnetic fields. Batelaan predicts possible uses in detecting mine fields. Yet, research is not far enough along to come to a consensus.

"It's hard to tell with things like that," said Adam Caprez, a UNL graduate student in computer science and engineering who worked on the experiment.

"It could be nothing more than a pure research problem," he said. "(It) could have no practical applications at all other than pure research.

"On the other hand, if there's something there – if we're understanding that system – we can push our knowledge further in other systems, and it's hard to predict what applications could come out of further understanding of quantum mechanics. Nowadays everything, including cell phones and GPS, relies on quantum mechanics."

Whatever the applications, research into action-at-a-distance continues, both at UNL and at other institutions.

"Physics people like puzzles, so that's a large part of the interest there," Caprez said.

iansacks@dailynebraskan.

iansacks@dailynebraskan.com