What happens when Newton's third law is broken?

May 15, 2015 by Lisa Zyga feature
In the new experiments, two layers of microparticles levitating at two different heights above an electrode have allowed researchers to investigate the statistical mechanics of nonreciprocal interactions, which violate Newton’s third law. Credit: A. V. Ivlev, et al. CC-BY-3.0

Even if you don't know it by name, everyone is familiar with Newton's third law, which states that for every action, there is an equal and opposite reaction. This idea can be seen in many everyday situations, such as when walking, where a person's foot pushes against the ground, and the ground pushes back with an equal and opposite force. Newton's third law is also essential for understanding and developing automobiles, airplanes, rockets, boats, and many other technologies.

Even though it is one of the fundamental laws of physics, Newton's third law can be violated in certain nonequilibrium (out-of-balance) situations. When two objects or particles violate the third law, they are said to have nonreciprocal interactions. Violations can occur when the environment becomes involved in the interaction between the two particles in some way, such as when an environment moves with respect to the two particles. (Of course, Newton's law still holds for the complete "particles-plus-environment" system.)

Although there have been numerous experiments on particles with nonreciprocal interactions, not as much is known about what's happening on the microscopic level—the —of these systems.

In a new paper published in Physical Review X, Alexei Ivlev, et al., have investigated the statistical mechanics of different types of nonreciprocal interactions and discovered some surprising results—such as that extreme temperature gradients can be generated on the particle scale.

"I think the greatest significance of our work is that we rigorously showed that certain classes of essentially nonequilibrium systems can be exactly described in terms of the equilibrium's statistical mechanics (i.e., one can derive a pseudo-Hamiltonian which describes such systems)," Ivlev, at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, told Phys.org. "One of the most amazing implications is that, for example, one can observe a mixture of two liquids in detailed equilibrium, yet each liquid has its own temperature."

One example of a system with nonreciprocal interactions that the researchers experimentally demonstrated in their study involves charged microparticles levitating above an electrode in a plasma chamber. The violation of Newton's third law arises from the fact that the system involves two types of microparticles that levitate at different heights due to their different sizes and densities. The in the chamber drives a vertical plasma flow, like a current in a river, and each charged microparticle focuses the flowing plasma ions downstream, creating a vertical plasma wake behind it.

Although the repulsive forces that occur due to the direct interactions between the two layers of particles are reciprocal, the attractive particle-wake forces between the two layers are not. This is because the wake forces decrease with distance from the electrode, and the layers are levitating at different heights. As a result, the lower layer exerts a larger total force on the upper layer of particles than the upper layer exerts on the lower layer of particles. Consequently, the upper layer has a higher average kinetic energy (and thus a higher temperature) than the lower layer. By tuning the electric field, the researchers could also increase the height difference between the two layers, which further increases the temperature difference.

"Usually, I'm rather conservative when thinking on what sort of 'immediate' potential application a particular discovery (at least, in physics) might have," Ivlev said. "However, what I am quite confident of is that our results provide an important step towards better understanding of certain kinds of nonequilibrium systems. There are numerous examples of very different nonequilibrium systems where the action-reaction symmetry is broken for interparticle interactions, but we show that one can nevertheless find an underlying symmetry which allows us to describe such systems in terms of the textbook (equilibrium) statistical mechanics."

While the plasma experiment is an example of action-reaction symmetry breaking in a 2D system, the same symmetry breaking can occur in 3D systems, as well. The scientists expect that both types of systems exhibit unusual and remarkable behavior, and they hope to further investigate these systems more in the future.

"Our current research is focused on several topics in this direction," Ivlev said. "One is the effect of the action-reaction in the overdamped colloidal suspensions, where the nonreciprocal interactions lead to a remarkably rich variety of self-organization phenomena (dynamical clustering, pattern formation, phase separation, etc.). Results of this research may lead to several interesting applications. Another topic is purely fundamental: how one can describe a much broader class of 'nearly Hamiltonian' nonreciprocal systems, whose interactions almost match with those described by a pseudo-Hamiltonian? Hopefully, we can report on these results very soon."

Explore further: Model system used to illustrate phase transition of a mixture of active and passive particles

More information: A. V. Ivlev, et al. "Statistical Mechanics where Newton's Third Law is Broken." Physical Review X. DOI: 10.1103/PhysRevX.5.011035

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mytwocts
2.3 / 5 (3) May 15, 2015
If the 3d law is violated, momentum is not conserved ;-).
DarkLordKelvin
4.6 / 5 (18) May 15, 2015
From the article:
(Of course, Newton's law still holds for the complete "particles-plus-environment" system.)


Soooooo ... the title of the article is blatantly egregious click-bait then, because of course, a fundamental law of physics (conservation of momentum) was actually NOT broken in this experiment.
docile
May 15, 2015
This comment has been removed by a moderator.
Returners
3 / 5 (4) May 15, 2015
The "Opposite" part is easy to prove. The "Equal" part not so much, because the second law is also involved in everything, and I don't believe it's "really" possible for the system to conserve momentum while losing kinetic energy, the way the on-paper formulas work out. The reason I say this is because such a scenario eventually results in an object which has macroscopic momentum, but zero kinetic energy, which is ridiculous.

First of all, in order for kinetic energy to radiate away, such as heat waste, it must carry away momentum. Which is to say the momentum of the Entropy Carrier, in this case an infrared photon, must remain balanced too. If you imagine a scenario where the object emits photons one forward and one backward the momentum must be conserved, but if the object is moving then the photons pass through the environment with different wavelengths as seen by a stationary observer, which means they have different momenta, which is still a contradiction.
DarkLordKelvin
4.2 / 5 (15) May 15, 2015
The "Opposite" part is easy to prove. The "Equal" part not so much, because the second law is also involved in everything, and I don't believe it's "really" possible for the system to conserve momentum while losing kinetic energy, the way the on-paper formulas work out.
This is basic physics. There is no law of "conservation of kinetic energy", while there *is* a law of conservation of momentum. In fact, kinetic energy is ONLY conserved in perfectly elastic collisions, which are imaginary and can only be approximated by physical systems.
The reason I say this is because such a scenario eventually results in an object which has macroscopic momentum, but zero kinetic energy
Why do you think that? Can you give an example?
First of all, in order for kinetic energy to radiate away, such as heat waste, it must carry away momentum.
This doesn't happen in a concerted way though .. the energy is stored in internal modes of the "target" (e.g. vibrations) in an intermediate step.
DarkLordKelvin
3.3 / 5 (7) May 15, 2015
Which is to say the momentum of the Entropy Carrier, in this case an infrared photon, must remain balanced too. If you imagine a scenario where the object emits photons one forward and one backward the momentum must be conserved, but if the object is moving then the photons pass through the environment with different wavelengths as seen by a stationary observer, which means they have different momenta, which is still a contradiction.
That's just not right .. momentum is conserved in all reference frames simultaneously. In your example above, you mention that the object is moving with respect to a stationary observer .. this means that the center of mass for the emission of the "matched" forward and reverse photons is moving, so the stationary observer will just interpret their different wavelengths/momenta as arising from the expected Doppler shift. There is no contradiction.
DarkLordKelvin
3.7 / 5 (9) May 15, 2015
Shawyer's/NASA EMDrive is said to violate the Newton's third law (as verified by Chinese and others). Howewer, the http://www.nasasp...m-drive, that the vacuum drag similar to aether drag observed during M-M experiment can be detected, i.e. the forward momentum of drive is still balanced with reactive momentum of vacuum in form of warp/scalar wave field.

I am pretty skeptical of this drive .. I know NASA says there might be something to it, but their results have not been peer-reviewed, nor have the claims of the Chinese groups. Even peer-reviewed claims can be wrong, such as the supposed gravity-wave detection from BICEP2 that was proved to be an artifact from cosmic dust, and the supposed "faster-than-c" neutrinos, which were tracked to a timing-error in the network setup. The old maxim "extraordinary claims require extraordinary evidence" is in play here, and I haven't seen anything that I would call convincing.
visual
4.2 / 5 (5) May 15, 2015
Shawyer's/NASA EMDrive is said to violate the Newton's third law (as verified by Chinese and others).

To call it verified is laughable. The miniature thrust they detected is smaller than if they used the input energy for a photon drive. It is clear to anyone with a common sense that If it really provides any thrust, it is certainly not reactionless but must be due to directed radiation.
Returners
2.6 / 5 (5) May 15, 2015
How do you explain conservation of momentum when Energy isn't conserved?

That suggests everything must eventually decay to infrared photons, because photons are the only thing that can have momentum without kinetic energy, and even then they have "energy" it's just not "kinetic energy," neverthess some photons have different ratios of momentum to energy because one is linear while the other is quadratic. This is a problem.

"Kinetic Energy" is not an actual substance, but a fictitious artifact of the reference system, that would be the only way to make sense of the scenario, as far as I can tell.

That's fine by me, I am in favor of measuring "energy" in terms of "momentum potentials" rather than (1/2)Mv^2
DarkLordKelvin
3.5 / 5 (8) May 15, 2015
How do you explain conservation of momentum when Energy isn't conserved?
That never happens.
That suggests everything must eventually decay to infrared photons, because photons are the only thing that can have momentum without kinetic energy
What is your basis for the notion that something must eventually have "momentum without kinetic energy"? Unless you are talking about the limit of the "heat death" of the universe, in which case maybe so .. I haven't thought about it carefully.
some photons have different ratios of momentum to energy because one is linear while the other is quadratic.
No. All photons obey E=pc.
"Kinetic Energy" is not an actual substance, but a fictitious artifact of the reference system
Sort of, it's relative, but not really "fictitious", because it is a non-negative quantity, and has a minimum value for any given system .. specifically, the KE with respect to the center of mass of a given system is minimized.
Mimath224
5 / 5 (1) May 15, 2015
@DarkLordKelvin Hi again...yeah, sorry to bother you Ha! I know very little about this topic except when I've read about the Casimir effect. I've got a couple of questions which I hope you can help me with.
1. Does the Derjaguin proximity force theorem apply here and if so do you think A. Ivlev considered it during the experiment?
2. On a completely simplistic level it would seem to me that the upper layer would be more prone to lose/disperse energy through some kind of 'plasma torque' [my wording...is there such a thing?] or tunneling of energy from one point to another?
Thanks in advance.
My thought is that when investgating established 'laws' and the breaking of symmetry thereof experiments need to be done in various orientations (and of course follow ups by others) but my interpretation here is that this wasn't done...perhpas it doesn't matter in this situation.
DarkLordKelvin
3 / 5 (4) May 16, 2015
1. Does the Derjaguin proximity force theorem apply here?
I doubt it .. I have only seen Derjaguin applied for van der Waals forces in colloids, larger electrostatic forces dominate here.
2.On a completely simplistic level it would seem to me that the upper layer would be more prone to lose/disperse energy through some kind of 'plasma torque' [my wording...is there such a thing?] or tunneling of energy from one point to another?
You may well be right .. I haven't thought about it too much. I got irritated at what I felt was a clear attempt to engage in "creative accounting" of the force balance to be able to claim a "3rd law violation" (which clearly isn't). I got as far as wondering why the particle "wake", which arises from the interaction of the *plasma* with a given particle, was counted as part of the net force particles in different layers exert on each other. Even in their own diagram, the direct interparticle force vectors balance; only the "wake" forces don't.
swordsman
not rated yet May 16, 2015
Planck's "...action of the electron upon itself" as it approaches the speed of light must be taken into consideration for microparticles.
Mike_Massen
3 / 5 (4) May 16, 2015
swordsman claimed
Planck's "...action of the electron upon itself" as it approaches the speed of light must be taken into consideration for microparticles.
What is this speed in reference to ?

You know 'relativity'; is the electron on a train, on an airplane, on a satellite, in or out of Earth's gravitational field - where ?

Do you know or have you ever thought through whats means by "Inertial Reference Frames" ?
http://en.wikiped...eference

And just WHY claiming something reaches the speed of light without referring to something is NOT a way to describe or even offer a question re motion, it is completely pointless, even Planck knew that !
MaxwellsDemon
1 / 5 (2) May 16, 2015
Here's a much more interesting way around Newton's third law, called "swimming in spacetime" (Jack Wisdom, MIT 2002):
http://dspace.mit...quence=2

Wisdom discovered an elegant and ingenious method of propulsion that sneaks around conservation of momentum: by executing a series of deformations in a gravitational field, a body can sorta climb or swim from one position to another without any reactive forces or momentum transfer.

Apparently the effect may actually be 16 orders of magnitude greater than Wisdom calculated, opening it up to practical applications (Longo, 2003):
http://vigo.ime.u...br/S.pdf

This concept was later generalized by Harte (2007):
http://arxiv.org/...09v2.pdf
MaxwellsDemon
2.3 / 5 (3) May 16, 2015
@visual
The miniature thrust they detected is smaller than if they used the input energy for a photon drive.

I'm very skeptical of the EM Drive reports as well, but let's keep our math honest.

Photon drives obey the simple equation F = W/c. The NASA experiments used under 100W, and the expected thrust of a photon drive at that power is 100W/c = 3.33e-7N. They've informally reported a thrust in a hard vacuum of 5e-5N, more than 100 times greater than a photon drive. The Chinese paper reported a far higher disparity (.72N at 2.5kW, 90,000 times greater than the 8e-6N one would expect from a 2.5kW photon drive).
docile
May 16, 2015
This comment has been removed by a moderator.
RealityCheck
3 / 5 (4) May 16, 2015
Hi Mike_Masson.
swordsman claimed
Planck's "...action of the electron upon itself" as it approaches the speed of light must be taken into consideration for microparticles.
What is this speed in reference to?
That was a disingenuous evasion of his obvious point of comparison to light speed. Just picture a source emitting electrons and photons simultaneously in same direction. The electron has a certain speed compared to the photon speed as the 'light speed standard' referent; and will hit co-located/co-moving respective detectors at different times depending on speed differences within the common frame of reference of overall 'source and detectors' lab setup . No need to bring spurious/irrelevant "compared to what" remarks/considerations into swordsman's 'speed of light' comparison case; it is obvious what he compared it to, Mike. Ok? :)
Moebius
not rated yet May 17, 2015
Strange, the temperature differentials in the experiment sound like the suns hot layer.
bluehigh
not rated yet May 17, 2015
What happens when Newton's third law is broken?


It's not been broken.
Just bent.

Details, that perhaps lead to new understanding.

.
PhysicsMatter
5 / 5 (1) May 17, 2015
The break down of Newton laws in microcosm has been known at least since works of L.Boltzmann on statistical theory of rarefied gases. His entropy and H-theorem violate symmetry of Newtons laws including the third law. In simplest words assumed molecular binary collisions are not equivalents to collision or interactions of macroscopic bodies. Also QM does away with Newton mechanical notions.

An interesting take on science, misinterpretations of science and scientists' motivations can be found at:
https://questforn...ibility/

mytwocts
not rated yet May 17, 2015
@PhysicsMatter: "QM does away with Newton mechanical notions. "
What do you mean? The QM momentum density is conserved, which fact constitutes the field theoretical equivalent of Newton's third law.
mytwocts
not rated yet May 17, 2015
"How do you explain conservation of momentum when Energy isn't conserved?"
Why should anyone attempt that?
Energy and momentum conservation are quite independent of each other.
Neither one implies the other.
PhysicsMatter
not rated yet May 18, 2015
@mytwocts
Clarification. What I meant was doing away with NEWTONIAN mechanical notions, not mechanical notions as a whole in a sense of field theory and continuity of condensed matter which deals with fields, densities and fluxes and considers not micro but MACRO forces as a energy field gradients and and not motion of separate molecules since L.Boltzmann proven lack of equivalency of such approach to Newtonian notions of motions and collisions.

Again you may have model or approximate such SINGLE binary collision with Newton Laws and calculate forces, energy, momentum but in reality after tracking 10e38 such collisions your calculations would be completely off , same say due to "higher order" interactions, in other words it would loose Newton mechanical laws' symmetry because the molecular "collisions" are not Newtonian in their nature. See Loschmidt's paradox.
DarkLordKelvin
2.3 / 5 (3) May 18, 2015
@mytwocts

Again you may have model or approximate such SINGLE binary collision with Newton Laws and calculate forces, energy, momentum but in reality after tracking 10e38 such collisions your calculations would be completely off , same say due to "higher order" interactions, in other words it would loose Newton mechanical laws' symmetry because the molecular "collisions" are not Newtonian in their nature. See Loschmidt's paradox.


I don't think you've got that right. There are molecular dynamics computer simulations that model microscopic statistical thermodynamics, such as the organization of solvent molecules around a larger molecule (i.e. water around a protein), using only Newton's laws to represent molecular interactions. These give accurate predictions of experimental observables (enthalpy, entropy, free energy, temperature, critical phenomena, etc.) for systems both at and far from equilibrium.
ubavontuba
not rated yet May 18, 2015
Shawyer's/NASA EMDrive is said to violate the Newton's third law
The miniature thrust they detected is smaller than if they used the input energy for a photon drive.
I'm very skeptical of the EM Drive reports as well
Here's a recent and interesting article on it:

http://www.nasasp...m-drive/

Disclaimer: Even though the above referenced site uses the NASA name, it is not affiliated with NASA.

Vietvet
5 / 5 (1) May 18, 2015
Here's some more on NASA's EM Drive.

http://www.space....asa.html
PhysicsMatter
not rated yet May 19, 2015
I don't think you've got that right. There are molecular dynamics computer simulations that model microscopic statistical thermodynamics, such as the organization of solvent molecules around a larger molecule (i.e. water around a protein), using only Newton's laws to represent molecular interactions. These give accurate predictions of experimental observables (enthalpy, entropy, free energy, temperature, critical phenomena, etc.) for systems both at and far from equilibrium.


These simulations are not self consistent otherwise you would have to solve many-body problem simultaneously (impossible so far) and not in time-step order like in simulation. Of course they would produce good approximation for MACRO observables. But that's not an issue. I was talking about precise trajectories of each of molecule after 10e38 collisions which if measured would be completely off. But in MACRO scale it does not matter where molecule is since it is indistinguishable from one another.
DarkLordKelvin
1 / 5 (2) May 19, 2015
I don't think you've got that right. There are molecular dynamics computer simulations that model microscopic statistical thermodynamics
These simulations are not self consistent
It's not clear what you mean by "self-consistent
otherwise you would have to solve many-body problem simultaneously (impossible so far) and not in time-step order like in simulation
You can't write down an analytical solution, but what's wrong with solving equations numerically?
Of course they would produce good approximation for MACRO observables. But that's not an issue
It is actually, because if Newton's laws were violated in real systems, simulations based on those laws would fail to represent reality
I was talking about precise trajectories of each of molecule after 10e38 collisions which if measured would be completely off
That's due to a combination of chaos, approximations of interparticle potentials, and hardware-level precision errors, not violations of Newton's laws.
DarkLordKelvin
1 / 5 (2) May 19, 2015
I was talking about precise trajectories of each of molecule after 10e38 collisions which if measured would be completely off
That's due to a combination of chaos, approximations of interparticle potentials, and hardware-level precision errors, not violations of Newton's laws
I would add that that this assumes that the mass of the simulated particles are large enough, and the simulation temperature is high enough, that quantum nuclear effects are negligible, which is the case for many systems. It also assumes that we aren't dealing with a pathological case, such as Born-Oppenheimer breakdown, where the quantum effects on nuclei and electrons can no longer be separated.

If you take the simple example of simulating a sample of argon gas at equilibrium at room temperature, and you had a sufficiently accurate model for the potential energy (including many-body effects .. such potentials do exist), an infinitely precise, "ideal" computer would give accurate trajectories.

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