Boosting the force of empty space

Jul 22, 2014
Two atoms exchanging a virtual photon. Empty space around them is not as empty as one might think.

Vacuum fluctuations may be among the most counter-intuitive phenomena of quantum physics. Theorists from the Weizmann Institute (Rehovot, Israel) and the Vienna University of Technology propose a way to amplify their force.

Vacuum is not as empty as one might think. In fact, empty space is a bubbling soup of various virtual particles popping in and out of existence – a phenomenon called "vacuum fluctuations". Usually, such extremely short-lived particles remain completely unnoticed, but in certain cases vacuum forces can have a measurable effect. A team of researchers from the Weizmann Institute of Science (Rehovot, Israel) and the Vienna University of Technology has now proposed a method of amplifying these forces by several orders of magnitude using a transmission line, channelling virtual photons.

"Borrowing" Energy, but just for a Little While

If you park your car somewhere and later it is gone, that is most probably not due to vacuum fluctuations. Objects do not disappear or reappear, that would violate the law of energy conservation. In the world of , however, things are a bit more complicated. "Due to the uncertainty principle, virtual particles can come into existence for a brief period of time", says Igor Mazets from the Vienna University of Technology. "The higher their energy, the faster they will disappear again."

But such virtual particles can have a measurable collective effect. At very short distances, vacuum fluctuations can lead to an attractive force between atoms or molecules – the Van der Waals forces. Even the ability of a gecko to climb flat surfaces can in part be attributed to vacuum fluctuations and virtual particles. The famous Casimir effect is another example of the power of the vacuum: The physicist Hendrik Casimir calculated in 1948 that two parallel mirrors in empty space will attract each other due to the way they influence the vacuum around them.

Atoms and Photons

Two atoms close to each other will also change the local vacuum around them. If one of them emits a virtual photon, which is almost instantly absorbed by the other, then on any timescale larger than the brief moment of the photon's existence, nothing much has happened – the total energy is conserved. But the fact that virtual particles can be exchanged modifies the vacuum around the atoms, and this leads to a force.

"Usually, such forces are very hard to measure", says Igor Mazets. "This is partly due to the fact, that such a photon may be emitted into any direction, and the chances of the second atom absorbing it are very small."

But what if the virtual particle has a little help to find its way? Ephraim Shahmoon, Gershon Kurizki (Weizmann Institute of Science) and Igor Mazets calculated what happens to vacuum forces between atoms when they are placed in the vicinity of an electrical transmission line such as a coaxial cable or a coplanar waveguide (a device used in cavity quantum electrodynamics experiments as an open transmission line), cooled to very low temperatures. "In that case, the fluctuations are effectively confined to one dimension", says Igor Mazets. The will be forced to go into the direction of the other atom.

In that case, the fluctuation-mediated attraction between the atoms becomes orders of magnitude stronger than in free space. Usually, the force decreases rapidly with increasing distance between the . Due to the , it falls off with one over the distance cubed, instead of one over the seventh power of the distance, as in the usual case.

The researchers believe that their proposed enhancement of the power of can have profound implications for understanding Casimir- and Van der Waals forces and it may even be used for applications in quantum information processing and other emerging quantum technologies.

Explore further: Physicists find simple solution for quantum technology challenge

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User comments : 25

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daggaz
4.6 / 5 (11) Jul 22, 2014
"At very short distances, vacuum fluctuations can lead to an attractive force between atoms or molecules – the Van der Waals forces."

That's a highly inaccurate and misleading statement if I ever saw one. Van der Waals forces have nothing to do with vacuum fluctuations, and occur in fact only in the presence of matter, being a manifestation of momentary imbalances in the electrical dipole moments of molecules.
Dr_toad
Jul 22, 2014
This comment has been removed by a moderator.
Tektrix
5 / 5 (5) Jul 22, 2014
Agreed. The article is vague, maybe due to poor translation, and almost nothing is said about the "transmission line" properties and other salient bits.

This part intrigues me, though: "Due to the transmission line, it falls off with one over the distance cubed, instead of one over the seventh power of the distance, as in the usual case."

Why the seventh power?


If this works like it does with magnets, then the force of the particle measured in isolation falls off as one over the distance cubed. This is combined with the the fall-off of force *between* the atom and particle, which is one over the 4th power of the distance, so the total resulting force falls off as one over the seventh power. The transmission line effectively creates a standing wave between the virtual particle and the atom, removing the "inverse 4th power" term. Just a guess.
George_Rajna
Jul 22, 2014
This comment has been removed by a moderator.
Dr_toad
Jul 22, 2014
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antialias_physorg
5 / 5 (3) Jul 22, 2014
method of amplifying these forces by several orders of magnitude


Usually, the force decreases rapidly with increasing distance between the atoms. Due to the transmission line, it falls off with one over the distance cubed, instead of one over the seventh power of the distance, as in the usual case.

That's not just 'orders of magnitude', that's exponential - which is a much more awesome critter
TheGhostofOtto1923
2.3 / 5 (6) Jul 22, 2014
Nazis figured how to extract the unglaubliche Energie of the vacuum decades ago.
http://en.wikiped...e_Glocke

-Dont mind me I'm fishing for 1s today.
MrVibrating
1 / 5 (1) Jul 22, 2014
method of amplifying these forces by several orders of magnitude


Usually, the force decreases rapidly with increasing distance between the atoms. Due to the transmission line, it falls off with one over the distance cubed, instead of one over the seventh power of the distance, as in the usual case.

That's not just 'orders of magnitude', that's exponential - which is a much more awesome critter

Eh? But any positive or negative number can be an exponent, such as 1, or even 0.00001! Whereas an order of magnitude only means a tenfold exponent, hence the description is satisfied after 3 distance increments along the cubed gradient.
Burnerjack
4 / 5 (1) Jul 22, 2014
Excuse my ignorance, but what is the difference between a virtual particle and a 'real' particle that has a very short lifespan? Have virtual particles actually been observed or is this theoretical?
Burnerjack
4 / 5 (4) Jul 22, 2014
Nazis figured how to extract the unglaubliche Energie of the vacuum decades ago.
http://en.wikiped...e_Glocke

-Dont mind me I'm fishing for 1s today.

Mission success.
MrVibrating
1.3 / 5 (3) Jul 22, 2014
Nazis figured how to extract the unglaubliche Energie of the vacuum decades ago.
http://en.wikiped...e_Glocke

-Dont mind me I'm fishing for 1s today.


Presumably you know that red mercury can only be extracted from the pituitary glands of live Lapland reindeer (hence Rudolf's red nose), and sasquatch testes. Unsurprising that this matters not to our resident Nazi sympathiser. My God, you're worse than Goebbels...

Per Godwin i now declare myself official winner of this thread, so continuing the theme of questionable exponents if everyone just awards me a 1 i'll know you really mean a whole-order higher of 10, what with five being the maximum (ie. a 1 being equal to two fives (but only for this winning post, and not the runners up above).

Admins you may now close this thread, thanks!
MrVibrating
not rated yet Jul 22, 2014
@burnerjack

The vacuum has roughly zero energy, but with an uncertainty of +/- almost-infinity, owing to Heisenberg's ignorance principle. This fundamental ambiguity means there's a non-zero chance of virtual photons having any wavelength between twice the Planck length and 6.85^e9 LY instantaneously existing at all possible locations, and the effective vacuum energy is billions of times greater than the total thermodynamic energy of the universe (which also happens to be roughly zero, eventually). And since this is generally regarded as the biggest mistake in physics it's probably worth forgetting anyway.

FWIW QED says virtual photons are what manifests the magnetic force (AKA EMF & voltage). Moving charges co-opt them from the ambient vacuum. Ditto spontaneous pair production (tho Feynman implicated time). And no, they can't be directly measured - they're implied by the quantised nature of ambient momentum, exchanged between virtual photons and real charges in units of h-bar.
ralph638s
1 / 5 (1) Jul 22, 2014
how can you tell the difference between existence and observability? ie, is the particle really coming in and out of existence or just momentarily becoming observable?
MrVibrating
not rated yet Jul 22, 2014
ETA: when i say "Feynam implicated time" i refer to his original comments that the energy required for spontaneous pair production was "borrowed from the future", and then repaid when they near-instantaneously mutually self-annihilate. IIRC some prefered to invoke the past instead of the future. But either way, this view's fallen into disfavour in light of modern developments.. It's now virtual photons what done it, and they're basically the 'stuff' of the vacuum energy, as regards its interactions with the more corporeal stuff.

If that's clear as mud then i'm done...
TheGhostofOtto1923
1 / 5 (1) Jul 22, 2014
Presumably you know that red mercury can only be extracted from the pituitary glands of live Lapland reindeer
No I thought it was the blood of a hind.
(hence Rudolf's red nose)
Rudolf? Rudolf Hess? He's in argentina with die Glocke you know.
MrVibrating
not rated yet Jul 22, 2014
how can you tell the difference between existence and observability? ie, is the particle really coming in and out of existence or just momentarily becoming observable?

Virtual photons have no objective existence beyond the moment of energy exchange between the thermodynamic realm and vacuum. We tend to only consider direct interactions between charges, but in reality charges cannot directly interact - the EM interaction is really a menage a trois, with the vacuum acting as an intermediary between moving charges, per SR. Virtual particles are like potential energy, which also has no objective reality besides a charge separation or whatever. A virtual photon (or rather the momentum assigned to it) is simply a unit of vacuum energy, with no more embodiment than a Joule or calorie.
Burnerjack
not rated yet Jul 22, 2014
Thank you MrVibrating. I think? Sounds like it is all conjecture based on uncertainty. My logic tells me that because something is uncertain, it doesn't make it a reality, just that it cannot be proven false. Clear as mud. Yup, we're done. Think I'll go for a walk now and mumble to myself...
Arties
4 / 5 (1) Jul 22, 2014
what happens to vacuum forces between atoms when they are placed in the vicinity of an electrical transmission line such as a coaxial cable or a coplanar waveguide
Technically blocks of mica or graphite are held only with Van der Waals forces. And graphite sheets are perfectly conductive in addition. The difference in strength of mica and graphite isn't very large though (both they're a minerals of Mohs hardness bellow 1).
antialias_physorg
5 / 5 (3) Jul 23, 2014
But any positive or negative number can be an exponent, such as 1, or even 0.00001

An exponent of as 'insignificant' 1.00001 will outpace ANY orders of magnitude (read: fixed factor) increase eventually. And quite drastically.

but what is the difference between a virtual particle and a 'real' particle that has a very short lifespan?

The way I understand it: The sumtotal of energy of virtual particle pairs in a vacuum is zero (otherwise you'd get a photon when they recombine due to energy conservation). A real particle has a positive energy (i.e. you can turn it into a photon).

That's why you need one of a particle pair to be swallowed up by a black hole to get Hawking radiation (in this case the part that carries the 'negative energy').
Torbjorn_Larsson_OM
5 / 5 (4) Jul 23, 2014
Interesting vaccuum relationship between van der Waals forces and Casimir forces. Fluctuations will have dipole moments as well as other particle field characteristics, and reasonably that is part of the displayed behavior.

@Burnerjack: "what is the difference between a virtual particle and a 'real' particle that has a very short lifespan? Have virtual particles actually been observed or is this theoretical?"

Yes, virtual particles is part of quantum field theory. You wouldn't understand diverse phenomena as Debye shielding of the native electromagnetic force or Hawking radiation of black holes without it. (Admittedly, both of these are still theoretically constrained rather than observationally, used to get the theory to work. But it's the only theory in town.)
Torbjorn_Larsson_OM
5 / 5 (5) Jul 23, 2014
[ctd]

Virtual particles are excitations, ripples in the field, that are not natural, long-lived resonances as particles is. E.g. they have no definite characteristics such as momenta, charges or energy. As particles propagate they 'disappear' at times because they instead make 'virtual particles' in the fields the particle interacts with; you have to add them together to recoup your particle. (Which reintegration is how the particle travels through the vacuum of fields.)

Here is what Matt Strassler, a particle physicist says:

"The term "virtual particle" is an endlessly confusing and confused subject for the layperson, and even for the non-expert scientist. I have read many books for laypeople (yes, I was a layperson once myself, and I remember, at the age of 16, reading about this stuff) and all of them talk about virtual particles and not one of them has ever made any sense to me. So I am going to try a different approach in explaining it to you.

[tbctd]
Torbjorn_Larsson_OM
5 / 5 (5) Jul 23, 2014
[ctd]

The best way to approach this concept, I believe, is to forget you ever saw the word "particle" in the term. A virtual particle is not a particle at all. It refers precisely to a disturbance in a field that is not a particle. A particle is a nice, regular ripple in a field, one that can travel smoothly and effortlessly through space, like a clear tone of a bell moving through the air. A "virtual particle", generally, is a disturbance in a field that will never be found on its own, but instead is something that is caused by the presence of other particles, often of other fields. ...

[tbctd]
Torbjorn_Larsson_OM
5 / 5 (5) Jul 23, 2014
[ctd]

Exactly the same equations that tell us about photons also tell us about how these disturbances work; in fact, the equations of quantum fields guarantee that if nature can have photons, it can have these disturbances too. Perhaps unfortunately, this type of disturbance, whose details can vary widely, was given the name "virtual particle" for historical reasons, which makes it sound both more mysterious, and more particle-like, than is necessary. "

[ http://profmattst...re-they/ ]
TechnoCreed
not rated yet Jul 23, 2014
BDS
Arties
1 / 5 (3) Jul 27, 2014
In that case, the fluctuations are effectively confined to one dimension. ..The virtual particles will be forced to go into the direction of the other atom. In that case, the fluctuation-mediated attraction between the atoms becomes orders of magnitude stronger than in free space. Usually, the force decreases rapidly with increasing distance between the atoms.
This effect was already observed here and here
Vacuum fluctuations may be among the most counter-intuitive phenomena

In AWT the vacuum fluctuations are simply analogy of Brownian noise in water. They do manifest with neverending motion of atoms, which do behave like the pollen grains inside of water (the liquid helium never freezes at room pressure because of it). So that the fluctuations are counterintuitive only, if you dismiss the aether model.
Arties
1 / 5 (3) Jul 27, 2014
The physicists are already using the dense aether model more consequentially, then I ever did. For example in this peer-reviewed study the space-time is considered composed of quantum loops, which can be compressed only to Planck length wavelength. The vacuum is supposed to remain elastic and bounce back, when the space-time gets compressed more, thus leading into white hole behavior. To be honest, I never considered some upper density limit for aether model with such a naive line of reasoning.
Whydening Gyre
not rated yet Jul 27, 2014
Said it before and I'll say it again.... charge differential.
11791
Aug 22, 2014
This comment has been removed by a moderator.
mikep608
1 / 5 (1) Aug 23, 2014
"Due to the uncertainty principle, virtual particles can come into existence for a brief period of time", says Igor Mazets from the Vienna University of Technology. "The higher their energy, the faster they will disappear again."

This uncertainty principle is a crap explanation for them not being able to explain.
there also is no empty space. Space is a substance called aether. These virtual particles they talk about, are not particles. There are no vacuums between particles, there are just differences in the force of the particles frequency.

https://www.youtu...JPboISF0

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