Friction in the vacuum?

February 20, 2017 by Lisa Zyga, Phys.org feature
The friction-like change in momentum discovered in the new study can be modeled by a moving device that emits photons in opposite directions. An observer can measure the photon frequencies, and using the Doppler effect, will calculate a change in momentum but no change in velocity. Credit: Sonnleitner et al. ©2017 American Physical Society

(Phys.org)—When three physicists first discovered through their calculations that a decaying atom moving through the vacuum experiences a friction-like force, they were highly suspicious. The results seemed to go against the laws of physics: The vacuum, by definition, is completely empty space and does not exert friction on objects within it. Further, if true, the results would contradict the principle of relativity, since they would imply that observers in two different reference frames would see the atom moving at different speeds (most observers would see the atom slow down due to friction, but an observer moving with the atom would not).

Writing in Physical Review Letters, physicists Matthias Sonnleitner, Nils Trautmann, and Stephen M. Barnett at the University of Glasgow knew something must be wrong, but at first they weren't sure what.

"We spent ages searching for the mistake in the calculation and spent even more time exploring other strange effects until we found this (rather simple) solution," Sonnleitner told Phys.org.

The physicists eventually realized that the missing puzzle piece was a tiny bit of extra mass called the "mass defect"—an amount so tiny that it has never been measured in this context. This is the mass in Einstein's famous equation E = mc2, which describes the amount of energy required to break up the nucleus of an atom into its protons and neutrons. This energy, called the "internal binding energy," is regularly accounted for in nuclear physics, which deals with larger binding energies, but is typically considered negligible in the context of atom optics (the field here) because of the much lower energies.

This subtle but important detail allowed the researchers to paint a very different picture of what was going on. As a decaying atom moves through the vacuum, it really does experience some kind of force resembling friction. But a true friction force would cause the atom to slow down, and this is not what's happening.

What's really happening is that, since the moving atom loses a tiny bit of mass as it decays, it loses momentum, not velocity. To explain in more detail: Although the vacuum is empty and does not exert any forces on the atom, it still interacts with the atom, and this interaction causes the excited atom to decay. As the moving atom decays to a lower energy state, it emits photons, causing it to lose a little bit of energy corresponding to a certain amount of mass. Since momentum is the product of mass and velocity, the decrease in mass causes the atom to lose a little bit of momentum, just as expected according to the conservation of energy and momentum in . So while the atom's mass (energy) and momentum decrease, its velocity remains constant.

This picture resolves both of the earlier problems: There are no forces acting between the vacuum and the atom, and two observers in different reference frames would both see the atom moving at the same constant speed, even though the atom would lose momentum due to decaying.

"In principle, the physics underlying our work has been known for a long time, so our result is of rather conceptual importance: We showed that the very successful model generally used to describe the interaction between and light can give this strange friction-like change in momentum," Sonnleitner said. "This result can only be explained when we include the equivalence between mass and energy. But since one would not expect that this aspect of special relativity (E = mc2) actually plays a role in atom-light interactions at these low energies, this has not been included in the model. So this puzzle showed how some piece of special relativity unexpectedly enters a well-studied and very successful model from (non-relativistic) quantum optics."

The effect is probably the first time that an atom's internal binding energy has made such a significant difference in a quantum optical context. The physicists emphasize that the effect is not limited to the spontaneous emission of a photon, but that it occurs whenever an atom changes its internal energy, such as when emitting or absorbing a photon. But in these cases, the atom will also see real velocity-dependent forces, which would hide the effect discussed here. For the time being, experimentally measuring the effect is not likely, since the involved is roughly three orders of magnitude smaller than what can be detected by today's most precise measurement techniques.

In the future, the researchers plan to investigate what impact this effect may have on the conventional model of atom-light interactions.

"We will try to extend the successful model currently used to describe atom-light interactions to include the possibility of a changing ," Sonnleitner said. "Of course this will only be a rather small correction, but it should help to complete the picture. It is never wrong to revisit, rethink and, if necessary, tweak an established theory."

Explore further: Team extends the lifetime of atoms using a mirror

More information: Matthias Sonnleitner et al. "Will a Decaying Atom Feel a Friction Force?" Physical Review Letters. DOI: 10.1103/PhysRevLett.118.053601

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KeithBrianJohnson
not rated yet Feb 20, 2017
Even had they not found their solution, there would not have been a conflict with special relativity, would there? After all, the observer moving with the atom would not have been in an inertial reference frame--if the atom were slowing down, he would be, too.
Ben D
1 / 5 (2) Feb 20, 2017
"The vacuum, by definition, is completely empty space and does not exert friction on objects within it."

Huh? I thought that all scientists understood that the so called vacuum is not in fact a vacuum, but consists of zpe, what am I missing?
Da Schneib
4.7 / 5 (3) Feb 20, 2017
So in other words, no, no friction in the vacuum. It's a change in mass/energy and thus in momentum, not a change in speed.
Chris_Reeve
Feb 20, 2017
This comment has been removed by a moderator.
humy
4.2 / 5 (5) Feb 20, 2017
Chris_Reeve

NO, if the evidence is overwhelming so to make the contrary have a negligible vanishingly small probability, it is settled. And then you would be a complete moron to either pretend or, worse, believe it isn't settled and bring back the aether or the flat-Earth. The Earth is not flat but round; it is settled.
big_hairy_jimbo
3.7 / 5 (3) Feb 20, 2017
I'd often wondered if an atom undergoing electron transitions and losing energy would be considered to have lost mass. So which "part" of the atom has lost the mass? The electron that underwent the transition??? I know the article suggested that they cannot "measure" this mass loss with current apparatus, but surely you could only ever INDIRECTLY measure this mass anyway. So from this an ION of an atom would have a lower mass too? A highly excited atom would have a greater mass than a ground state atom? Could you use e=hf of the emitted photon combined with e=mc^2, to deduce the amount of MASS lost from the Atom? Do those ENERGIES have the same units? If I recall correctly DeBroglie's wavelength and momentum come into play here too.
Ben D
1 / 5 (1) Feb 20, 2017
But it is plain logic that the reality represented by concept 'zpe' means precisely one and the same reality represented by the concept 'aether'...there is no actual vacuum.
434a
3.3 / 5 (7) Feb 20, 2017
There seems to be a never-ending stream of observations at the quantum level which could be interpreted by an aether....etc etc


I have met people in your position in the past, they seem to have a need to be seen as exceptional. However, they knew they would never achieve this through natural talent and lacked the necessary determination to achieve it through hard work, such was their nature.
Then, for those with the least moral courage, they saw an opportunity to fulfil the gratification they craved. It's a well trodden path, charlatanism. History's pages are filled with its stench and like a putrid smell it is instantly recognisable to one who has been exposed before. Usually they ply their trade in the markets of the untutored or unskilled, you sir are interesting. You walk into the lion's den and flaunt your deceit for all to see. May be it is a form of masochism, self flagellation as a form of atonement for what you know you should have been and failed to become.
retrosurf
5 / 5 (4) Feb 20, 2017
BHG:

1) The atom lost mass equal to the mass equivalent of the photon that was lost in that electron transition. 1a) No part: the atom as a system has lost mass, not just the electron.
2) A positive ion has increased in mass, and a negative ion has been reduced in mass, relative to the uncharged atom (by the masses of the electrons either gained or lost).
3) Highly excited atom? Yes, it has higher mass than the ground state atom. Don't forget nuclear isomers, too.
4) Yes, you could use those equations.
5) Okay, now you're just lazy. A joule, from e=hf, is 10 million ergs, from E=MC**2

I'm happy to receive any corrections on my responses.
Chris_Reeve
Feb 20, 2017
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big_hairy_jimbo
5 / 5 (3) Feb 20, 2017
Thanks RETROSURF, but I speculate that your got point 2 the wrong way around. I would have thought a positive ION, would have a decreased mass, given it has lost an electron. I'm sure that is what you meant.

yeah I was being lazy on point 5, but I left it more are as a thought experiment for those less knowledgeable, so they could get the idea that UNITS have to match in order to make an equivalence between equations.

Thank you for your answers :-)
Chris_Reeve
Feb 20, 2017
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Bob Osaka
not rated yet Feb 20, 2017
...as our ability to make measurements more and more precise, more anomalies will almost certainly be observable. As to the concept of the vacuum or empty space...at any random point in the universe, particles and waves may come from any and every direction... see: Casimir effect...we may also find on a specific scale no two particles, within a particular category are precisely the same...the standard model representing groups of similar individuals which nonetheless have distinct and measurable characteristics...
Chris_Reeve
Feb 20, 2017
This comment has been removed by a moderator.
Telekinetic
3 / 5 (4) Feb 20, 2017
"Only the existence of a field of force can account for the motions of the bodies as observed, and its assumption dispenses with space curvature. All literature on this subject is futile and destined to oblivion. So are all attempts to explain the workings of the universe without recognizing the existence of the ether and the indispensable function it plays in the phenomena. My second discovery was of a physical truth of the greatest importance. As I have searched the entire scientific records in more than a half dozen languages for a long time without finding the least anticipation, I consider myself the original discoverer of this truth, which can be expressed by the statement: There is no energy in matter other than that received from the environment." – Nikola Tesla
Benni
4 / 5 (5) Feb 20, 2017
"Although the vacuum is empty and does not exert any forces on the atom, it still interacts with the atom, and this interaction causes the excited atom to decay. "

If the vacuum "does not exert any forces on the atom" how can it be stated "it still interacts with the atom" causing said atom to decay? For this atom to lose mass through the loss of a photon, it cannot interact with absolutely nothing.
Kron
5 / 5 (2) Feb 20, 2017
"There is no energy in matter other than that received from the environment."
Each particles aura spans the entire universe. The manifestation of a particle is the culmination of all of the energy across the cosmos. A particle does not exist in free-space. A particle is a bump in the cosmic field.

Particles are not as solid as our minds interpret them to be. Experiments of the micro-realm have shown us the peculiar behavior of atoms and their subatomic constituents. Matter is just the spike in energy in a particular point in space. These pop in and out of existence freely, but tend to emerge in regions of highest density most. Black holes are a good example. Energy density around them is extremely high, so particles readily emerge in their vicinity. There is no distinction between real and virtual particles. Both are the same.

All particles are field excitations. I think thats what Teslas line boils down to. Particles are disturbances in the Universal field of energy.
arcmetal
3 / 5 (1) Feb 20, 2017
...All particles are field excitations. I think thats what Teslas line boils down to. Particles are disturbances in the Universal field of energy.

This matches up well with the deterministic pilot-wave theories, and the new observations being seen these days.
arcmetal
4.5 / 5 (2) Feb 20, 2017
The higher level of thinking would take the long view -- which means rising above all of the ideological wars that academia has historically waged against this or that idea. Those science wars were fought on the basis of limited information, and their legacy are these textbooks and academic culture which are obviously allergic to admitting mistakes.

This here is so important, yet its ignored by those that seem to have a need to sustain some "settled" dogma. But as time progresses, technology advances and new observations reveal a better view of the truth.
Da Schneib
3.7 / 5 (6) Feb 20, 2017
which suggests that if we are smart, we will realize that the worldview we have going into the situation is shaped more by the historical unfolding of textbook "facts" than the much fuller accounting of the facts of Nature which we would have at some arbitrary time much further in the future.
"God of the gaps" logical fallacy detected.

A Romulan in the Neutral Zone.

Raise deflector shields and arm photon torpedoes.
swordsman
1 / 5 (2) Feb 20, 2017
Total misunderstanding of the dynamics of atom motion. The forces acting on atoms are quite complex. Atoms can both attract and repel one another, depending on location, motion, and other atoms nearby. They are known to attraction one another in the near field and are repelled when too near to one another. What is needed is the electronic model of the atom (Planck model) and and electronic analysis of the complex motions. This cannot be explained in a few words and a simplistic error-prone ridiculous approximation.
Da Schneib
4.3 / 5 (6) Feb 20, 2017
@swordsman, the article is available on arXiv: https://arxiv.org...2264.pdf

Maybe you missed the part about how it's a single atom. They can do that these days, you know. Lotsa progress been made since the 1960s.

Then after that we can talk about the, you know, real quantum physics calculations on page 1 (second column) and all of page 2.

This isn't a very revolutionary paper. What the writers are pointing out is what anyone who had the interest and gumption to actually do the calculations would have found out. So when you question whether it's worth spending money on science, this is just the stuff that beancounter 'crats like you obstruct that otherwise we'd've known thirty years ago.

[contd]
Da Schneib
4.3 / 5 (6) Feb 20, 2017
[contd]
Science is like building a skycraper; you can't really get along when you leave little details out. This is real, basic theoretical science. Not flashy, not groundbreaking, just filling in the details. In twenty years this will turn out to be incredibly important to a theory we haven't even imagined yet.

Meanwhile, your strategem of incoherence, by trying to introduce extraneous influences that do not exist in the real experiment is transparent to the merest adolescent; humans are evolved to detect deception over millions of years. Gorillas and chimpanzees can detect deceit and will react violently to it. It's not very friendly.
retrosurf
5 / 5 (3) Feb 21, 2017
>but I speculate that your got point 2 the wrong way around.

You're right. Damn that Ben Franklin.
katesisco
1.8 / 5 (5) Feb 21, 2017
Seems like what W Thornhill has been describing in his theory of energy to mass and back in the process of electricity being transferred from anode to diode in the stellar configurations.
There is after all the granite shell of planet earth explained by plasma into water vapor creating minerals.
jonesdave
3.9 / 5 (7) Feb 21, 2017
Seems like what W Thornhill has been describing in his theory of energy to mass and back in the process of electricity being transferred from anode to diode in the stellar configurations.
There is after all the granite shell of planet earth explained by plasma into water vapor creating minerals.


Thornhill isn't qualified to find his own arse with both hands. Fact.
Chris_Reeve
Feb 21, 2017
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Chris_Reeve
Feb 21, 2017
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jonesdave
3.5 / 5 (8) Feb 21, 2017
Few people today appear to realize that there was a strong push in the early 1900s....


So frakking what? Science has moved on since then. Thornhill and his cabal of scientifically illiterate groupies haven't.
Chris_Reeve
Feb 21, 2017
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Da Schneib
5 / 5 (7) Feb 21, 2017
"Anode to diode?"

Did he really say that?
jonesdave
4.1 / 5 (9) Feb 21, 2017
By 1904 the electromagnetic view of the world had taken off.....blah blah


And in 1917 Rutherford split the atom. No more need for theories such as electric suns. In later decades, remote and in-situ observations of comets removed the need for silly ideas based on electric woo, etc, etc. And yet these goons still believe such nonsense. Go figure.
Benni
1.7 / 5 (6) Feb 21, 2017
Chris, the problem with so much of what passes for Astrophysics these days is nothing less than a cornucopia of Perpetual Motion. It's become part of the Culture we live in, that there can be free stuff not only on planet Earth but everywhere, and does it ever show up here in this chatroom.

Benni
1 / 5 (3) Feb 21, 2017
And in 1917 Rutherford split the atom.
......no, blokey guy he didn't, that didn't happen until shortly before the first atomic bomb test.
jonesdave
4 / 5 (8) Feb 21, 2017
And in 1917 Rutherford split the atom.
......no, blokey guy he didn't, that didn't happen until shortly before the first atomic bomb test.


http://www-outrea...ndex.htm
Chris_Reeve
Feb 21, 2017
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jonesdave
4.1 / 5 (9) Feb 21, 2017
^^^^^WRONG. As seen by countless pieces of confirming evidence. Contrasted to the complete lack of such for alternate hypotheses.
Chris_Reeve
Feb 21, 2017
This comment has been removed by a moderator.
Chris_Reeve
Feb 21, 2017
This comment has been removed by a moderator.
Chris_Reeve
Feb 21, 2017
This comment has been removed by a moderator.
AmritSorli
Feb 22, 2017
This comment has been removed by a moderator.
SiaoX
not rated yet Feb 22, 2017
further, if true, the results would contradict the principle of relativity
But why? It's not actually explained here. Because of the Doppler effect, a photon emitted in the same direction of travel as the atom would be blue-shifted, having its frequency, and therefore its momentum, increased; whereas a photon emitted in the opposite direction would be red-shifted and have its momentum decreased. The atom would therefore experience a net force proportional to its momentum but in the opposite direction – effectively, it would experience friction from the vacuum. But such force is difficult to interpret like the friction at all - it's merely classical Compton recoil. The vacuum friction has nothing to do in similar way, like the Compton scattering was never interpreted like the result of vacuum friction.
SiaoX
not rated yet Feb 22, 2017
a true friction force would cause the atom to slow down, and this is not what's happening
The net force acting to atom nuclei due to Doppler shift applies only during moment, when the atom nuclei accelerates during radioactive decay. This is not how the friction behaves - the friction force applies during whole its path. But I think, that this net force should still exist there due to another effect: radiation of gravitational wave during acceleration of massive bodies, which transfers mass and momentum out of system. If this effect would be fully compensated with loss of mass (as the above study implies), then no gravitational wave would be released, which is also in contradiction with relativity - just general one this time. So I think, that the situation of atom recoil during radioactive decay would require more thorough analysis.
RealityCheck
1 / 5 (2) Feb 22, 2017
Hi SiaoX. :)

Excellently observed and explained...as well as polite and to the point! Thanks. Much appreciated. :)

PS: I would add my own observation that the vacuum permeability and permittivity for EM field perturbation/transmission (propagating EM radiation) determines/limits 'max speed', due to 'resistance' to transition between space-energy location 'quantum states', of all EM radiations (and possibly of Gravititational field radiations too; in the latter case I view such things as 'neutrinos' as Gravitational field type radiations rather than EM type radiations)...and they too would add/subtract from total inherent energy budget of the 'moving/accelerating' em-grav 'hybrid-field' body/feature.) Thanks again for an excellently put observation/explanation, SiaoX! :)
Benni
not rated yet Feb 22, 2017
The current solar model was perfectly appropriate for a universe where stars are separated by an empty vacuum. But, we've known that's not the case now since 1958, when we sent the first rockets to space.


......and get this Chris, cosmologists are now convinced the Oort Cloud extends at least a full light year beyond the Sun, some are suggesting up to three. That's a lot of material to hopscotch around on.
swordsman
not rated yet Feb 27, 2017
@Da Schneib

You jump to unwarranted conclusions. From the article: "....as the atom decays...". What, exactly does this mean? What makes the atom decay? Is it radioactive? If it is radioactive, then loss of energy implies loss of mass. Quite a different conclusion from that of the article. If the atom is moving in an electric or magnetic field, then a "magnetic potential" is created in the transverse direction ("cross-vector"). This would produce some transverse movements that could slow the atom. These types of systems can and have been analyzed in the past and thoroughly documented. I do not see any indication that these investigators are aware.

baudrunner
3 / 5 (1) Feb 27, 2017
Not one mention of the influence of gravity in experiments of these kind done at 1G, vacuum notwithstanding. Also, theorizing based on these observations is premature. Beware the theory trap, for example, inflation theory developed to possibly explain isotropic nature of CMB radiation. Now it is a fundamental theory all on its own!
habermacher
5 / 5 (1) Feb 28, 2017
"This is the mass in Einstein's famous equation E = mc2, which describes the amount of energy required to break up the nucleus of an atom into its protons and neutrons,"

Oliver Heavyside, not Albert Einstein. please stop giving credit to Einstein for an other persons hard work.

Da Schneib
not rated yet Feb 28, 2017
Heaviside is not given nearly enough fame and credit outside the scientific and engineering communities and even within them.

He was also responsible (in collaboration) for the formulation of the Maxwell Equations that is taught today in both science and engineering courses, and is therefore the widely used form of them.
Da Schneib
not rated yet Feb 28, 2017
Here's one that just about everyone will get: Heaviside patented the first coaxial cable.

He's the Tesla of Britain.
nikola_milovic_378
Mar 08, 2017
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nikola_milovic_378
Mar 08, 2017
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