February 20, 2017 feature
Friction in the vacuum?
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 special relativity. 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 atoms 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 energy 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 mass," 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."
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User comments
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?
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.
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.
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.
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 :-)
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.
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.
This matches up well with the deterministic pilot-wave theories, and the new observations being seen these days.
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.
A Romulan in the Neutral Zone.
Raise deflector shields and arm photon torpedoes.
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]
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.
You're right. Damn that Ben Franklin.
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.
So frakking what? Science has moved on since then. Thornhill and his cabal of scientifically illiterate groupies haven't.
Did he really say that?
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.
http://www-outrea...ndex.htm
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! :)
......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.
Oliver Heavyside, not Albert Einstein. please stop giving credit to Einstein for an other persons hard work.
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.
He's the Tesla of Britain.
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