Proving an aspect of the AB effect: when Newton's Third Law doesn't work

December 4, 2007 By Miranda Marquit, feature
Adam Caprez
University of Nebraska-Lincoln graduate student Adam Caprez fires up the pulsed electron laser used to test the no forces aspect of the Aharonov-Bohm effect. Credit: Herman Batelaan

An action doesn’t always result in a reaction.

One of the interesting phenomena present in quantum mechanics is the Aharonov-Bohm (AB) effect. The AB effect predicts that a charged particle, usually an electron in experiments, shows effects from electromagnetic fields in regions where the particle is excluded. This leads to the interesting fact that, in electromagnetism, Newton’s Third Law of Motion doesn’t always hold true.

Herman Batelaan explains to “If you want to move anything in the world around you, you need forces. But in the Aharonov-Bohm effect, the electron reacts without any forces. There is no force, but something happens.”

Batelaan, a scientist at the University of Nebraska-Lincoln oversaw an experiment done by graduate student, Adam Caprez, and Brett Barwick to demonstrate the absence of forces in the AB effect. A description of the experiment, and their results, is available in Physical Review Letters: “Macroscopic Test of the Aharonov-Bohm Effect.”

“The interesting thing,” Batelaan says, “is that experimentally scientists have detected evidence of this effect, and it is mentioned in textbooks. But nobody had shown that no forces are there.” The experiment performed at the University of Nebraska-Lincoln constitutes the first demonstration of a lack of forces. “We know the effects, and this is expected.” Batelaan continues. “Theoretically, scientist predicted this, but we want to see this. Now we have it.”

Experimental demonstrations of the AB effect usually include carefully controlled electrons using a distant electromagnetic field. “We understand the physics of this, such that we can take electrons and control them so well that we can see quantum mechanics happening,” Batelaan says. In order to perform the current experiment, the team used a pulse laser to hit a metal needle, a method developed at Stanford.

“You have a pulsed electron source,” Batelaan explains, “and you have something you can time.” Batelaan says that if a force is present there will either be a delay, or an early arrival. The experiment showed no time delay, and this demonstrates that the AB effect lacks forces, even though something is clearly happening with the electrons.

Caprez said that what he found most appealing is that, “we have a rare example where quantum mechanics, electromagnetism and relativity are all working at the same time.”

As far as immediate applications are concerned, Batelaan admits that there isn’t much about this experiment that will be useful on a practical level right now. But, he insists, “This is very fundamental quantum mechanically. It is helpful in terms of a better understanding on the quantum level.” He points out that devices are reducing in size at a rapid pace, and that as science and technology shrink, “we will need to understand the interplay between quantum mechanics and electromagnetic fields as deep as possible.”

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3.4 / 5 (5) Dec 04, 2007
Hype, and bad reporting.
Newton's 3rd says that momentum is conserved. The "effect" is a phase shift, not a change in momentum. So, if the electron did feel a force, that would be a violation of Newton's law. He showed that there is no violation, the opposite of what the article says.
3.7 / 5 (3) Dec 04, 2007
Is this "off the top of the head" type of reporting? Sure would rather get a review of what is found out a day or two later with accuracy than up to the minute fantasies. Physics.org_fantacies
3 / 5 (2) Dec 04, 2007
Ah thanks for that LearmSceince (I had to try and spell that name 3 times before I got it righ... wrong). I went 0_o while reading this article, but I hadn't heard of the Aharonov-Bohm Effect, and the article didn't bother to explain itself, so I didn't want to outright dismiss it. Now I'll go look it up. Well, I would have done that anyway I guess.

This author needs to go work for NewScientist. They'd appreciate her skills there:P. Misleading title, misleading article, and borderline wrong "facts". Yup, definitely NS material.
2.2 / 5 (5) Dec 05, 2007
Non-causal action-at-distance in the experiment implies the existence of quantum forces that are not operative through space and time. The non-locality of a single electron confirms that physical matter has both universal and particular aspects. An atom is the intimate coherence of these two fundamental characteristics common to all physical phenomena.

This is not consistent with linear causality either in the Newtonian or Relativity sense. The continuous field concept in the sense of matter embedded in a preconceived a priori space-time is faulty. Einstein himself wrote: I consider it quite possible that physics cannot be based on the field concept, that is, on continuous structures. Then nothing remains of my entire castle in the sky, including the theory of gravitation, but also nothing of the rest of modern physics. (In a letter to Michele Besso in 1954, the year before he died.) In a discontinuous universe a different picture emerges that is consistent with the evidence and with common sense.

Planck's constant indicates a discontinuity in the synchronous projection of particulate matter as in a cosmic movie. The electromagnetic rainbow is sliced across it entire breadth with the recurrent projection of each frame. EM radiation comes to us as a discontinuous series of pulses. The universal component of independently projected atoms regulates their synchronous projection in a series of independent still space frames linked up by light. All relative motion is a series of quantum jumps between these discrete still particle frames. Light is the only activity within each space frame and it is quantized by each space frame, along with space and time. Light comes from inside atoms and has a universal relationship to each atom, accounting for its universal velocity. So light itself defines space. Where there is no light, there is a black hole in space. And obviously physical effects can not be transmitted through the integrated fabric of space-time faster than light if it defines space.

This requires that Newtons Third Law does not apply in a continuous way to quantum events measured over short periods of time, because there is a primary interval of time associated with the synchronous projection of each atomic space frame. Successive space frames are discontinuously assimilated from an integrated timeless quantum frame (called the Void) by the universal characteristic of matter. The Void is a spatially indeterminate energy field orthogonal to the integrated fabric of space-time that we perceive as continuous even though matter is synchronously oscillating between particulate Form and its energy equivalent in the Void. In this way sub-atomic particles remain implicitly and timelessly correlated. So do all atoms. All relative particle action takes place via the integrating quantum frame, called the Void, and this is synchronously timeless.

Relative motions introduce synchronous distortions as a result of relative space frame skipping with a corresponding accumulation of quantum energy equivalents in the Void. This accounts for relativistic effects but also introduces a small family of quantum forces, since accumulated energy must at some point find expression on the space frame side of the movie. These quantum effects are not transmitted as a force through space-time. They can only manifest synchronously with the projection of each space frame, and this is inconsistent with Newtons Third Law on a quantum scale. A new quantum-relativity emerges naturally that also accounts for gravitation. This offers a new and more meaningful methodology to the physical and biological sciences. There is more at
Dec 05, 2007
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Dec 05, 2007
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Dec 05, 2007
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5 / 5 (2) Dec 05, 2007
Put it this way. If this really violated conservation of momentum, it wouldn't be simply casually mentioned in obscure literature here and there over the years. Rather, large armies of scientists would be screaming and pulling their hair out. They aren't, so it doesn't.... (probably)
1 / 5 (1) Dec 06, 2007
The important question seems to be whether the phase shift changes the momentum of the electron. We need to consider the wave equation of the charged particle.

The phase was originally unaffected, but then without force but through the action of magnetic vector potentials, the phase was made to change. If the phase of the electron has changed, it seems sure that the momentum of the electron was, at the very least, momentarily affected.

In the case of the magnetic Aharanov-Bohm effect, it is clear and experimentally verfified that absolutely no force is required to change the phase of surrounding electrons. For instance, a transfomer or electric motor is often shielded so as not to produce large magnetic fields outside the enclosure, however, the magnetic vector potentials are a very fundamental force which do not decay at the same rate as the field.

Where the classical magnetic field has faded to zero, the magnetic vector potentials still exist and change the phase of charged particles. It seems clear that these vector potentials will interact most strongly with transition metals, especially those with only a single valence electron such as copper, silver and gold.

In addition, a highly permeable metal such as nickel will surely endure a change in electronic state. Where our biochemistry is guided by a complex interplay of electron transfer, particularly between transition metals, it begs the question, what effect do the magnetic vectors produce in the real world?
Dec 06, 2007
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1 / 5 (1) Dec 10, 2007
Momentum and energy are conserved on the quantum scale. It's just a matter of considering a 4-vector and an uncertainty principle.
5 / 5 (1) Dec 10, 2007
Ragtime: think of moving something from one place to another on a horizontal surface. Potential energy is the same before and after; kinetic energy is the same (zero) before and after. In the quantum world, you can stop there. In the macro world, consider a frictionless surface and a mechanism which expends energy to start the block moving and then recovers the energy when breaking.

templeghost: Look at the effects of an MRI scan. No side effects whatsoever.
1 / 5 (3) Dec 11, 2007
I thought lightheadedness, a metallic taste, nausea and seeing 'lightning' were side effects.

Has anyone conducted a study to see if multiple MRI scans increase the risk of rare blood cancers?

Why not start with the records of atheletes who frequently have MRI scans for sports related injuries?

They have absolutley no conception of what they are doing! Ask the people who work around intense magnetic fields what fantasies they tend to enjoy, you might be surprised how powerful the side effects are.

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