Heat energy leaps through empty space, thanks to quantum weirdness
phys.org
phys.org
Normally, you feed a cavity resonator with E&M radiation (for example, your microwave), but the Casimir effect is a recognition of a factoid from quantum field theory: Photon fields have an energy of (N + 1/2) \hbar\omega, where N is the number of photons in the mode, and omega is the frequency of the mode. The strange factoid is that even for N=0 (no photons) there is still energy in the mode. This energy goes by the name "zero-point energy", because there is still energy in the vacuum for zero photons.
When you change the width W of the cavity, there is a change in the allowed modes, so there is a change in the total zero-point energy. The Casimir force then makes sense: Since the zero-point energy changes with the distance between the metals, there is a force pushing the system from the higher-energy configuration to a lower-energy configuration.
Edit: Since this has gotten attention, my one-sentence summary of the article from below:
Phonons cause a microscopic change the distance between the two plates, which by the Casimir force, then allows transmission of phonons across the vacuum gap.
https://en.wikipedia.org/wiki/Casimir_effect
It's not a strong force, decaying like the 4th power of distance as I recall. Measuring it is not easy:
It would be interesting to know how they think the heat is being transferred: are the two plates exchanging electrons which are able to quantum tunnel across the gap, or are they trying to say that there's a more fundamental quantum effect going on?
The Casimir effect is an effect between two conducting plates separated by only a vacuum. Strange as it may sound, there is a force generated between the two plates which is dependent on the distance between them.
My quick take on the article is that phonons cause a microscopic change the distance between the two plates, which allows transmission of phonons across the vacuum gap.
If I understand correctly, there is a repulsive force on the matter on either side of the gap that is a consequence of vacuum fluctuations within the gap, and I gather that in this case, it is the electromagnetic fluctuations (the formation and dissolution of virtual photons) that is the dominant source (despite this being electromagnetic, it is not black-body radiation from the matter on either side of the gap.) The force is a function of the width of the gap, as virtual photons with a wavelength greater than the gap cannot form, so as the gap narrows, a growing spectrum of photons are excluded, and the repulsive force decreases[1]. Consequently, any motion of one side of the gap results in a varying force on the other. In this case, the motion is from thermal fluctuations, but it could also be the result of sound, so they are also saying sound could travel through a vacuum.
Given the difficulty of demonstrating the additional heat flow experimentally, I am skeptical that it will have "profound implications for the design of computer chips and other nanoscale electronic components where heat dissipation is key", at least until we are working at even smaller scales.
[1] As the effect is usually presented, with two plates close together, the force on the gap side of the plates is less than that on the open sides, so the net force acts to pull the plates towards one another.
https://en.wikipedia.org/wiki/Casimir_effect#Dynamical_Casim...
We are. The current cutting edge for microchip fabs is 7 nanometers and TSMC is planning a 5 nm one for 2020 and a 3 nm one for 2022.
And according to wikipedia: "at separations of 10 nm the Casimir effect produces the equivalent of about 1 atmosphere of pressure" they say it is the dominant force on submicron scales between conductors.
I don't know where MEMS are nowadays, but understanding this force is probably something that will help them miniaturize even more.
So apparently feature sizes are around 40 nm even in "7" or "10 nm" processes.
- The results were discovered "surprisingly", but later that they were "long theorized".
- "Heat is usually conducted in a solid through the vibrations of atoms or molecules, or so-called phonons—but in a vacuum, there is no physical medium". Heat is usually conducted in a solid? I haven't heard it defined like that before.
- Their discovery "opens up unprecedented opportunities for thermal management". The style sounds a little too promotional for scientists doing basic research.
- Saying you can now "shout" in a vacuum with no qualifying words? Don't see how it's not a purely hyperbolic statement.
- Referring to his PhD defense 25 years ago having no forethought of these by himself or his professors?
Is that because quantum mechanics wasn't being taught 25 years ago or because they simply were not thinking deeply about that particular topic at the time?
After Wheeler discussed quantum foam in the 50's how many years was it before others in the field could at least imagine the possibility of results like this?
How have you heard it defined?
>Don't see how it's not a purely hyperbolic statement.
Obviously. And I do believe it was meant to be taken as such.
>Is that because quantum mechanics wasn't being taught 25 years ago
I took my first quantum course about 20 years ago, and it didn't seem like it was something new.
> or because they simply were not thinking deeply about that particular topic at the time?
They were talking about an anecdote about shouting through a vacuum. You, yourself determined it was hyperbolic in nature, so I don't see how questioning the "depth" of their thinking on the subject makes any sense.
Usually something like: Heat moves via matter or energy. For example, air, water, electromagnetism...
It seems to add no value to arbitrarily say "mostly solids" rather than just say it moves via a medium. At worst it's misleading, especially when said directly by scientists, not simply written by pop-sci journalists.
>>...[it's a purely hyperbolic statement]
>Obviously. And I do believe it was meant to be taken as such.
Hyperbole is part of language, but it's used more often by politicians. I consider it counterproductive for researchers to speak this way relating to their results. Others seem to agree: https://wattsupwiththat.com/2015/12/30/study-hyperbole-is-in...
>>Is that because quantum mechanics wasn't being taught 25 years ago >[20 years ago it didn't seem like something new]
Right, that was a rhetorical question. The high level concepts behind it haven't been new to PhD level physicists, even more than 25 years ago (Wheeler).
>They [used] an anecdote...shouting through a vacuum...[you said] it was hyperbolic, [so how does it make sense to question the "depth" of their thinking]
No, I said their present day quote was hyperbole, not the PhD defense. During the latter, I would not consider it professional for the panel to ask hyperbolic questions or for them to be answered that way. Not in the context of academic research, when potentially years of work and someone's future may be on the line.
I get that they want press, attention, maybe investment. Indeed, hard work yielding good results deserve recognition. However in my opinion that kind of self promotion and exaggeration is better served from unattributed copy and PR initiatives, rather than by direct quotes from the lead researchers.
In an alternate universe, investigative journalists reveal that this research was secretly funded by George Lucas to disprove all the naysayers who said the Death Star explosion wouldn't have made any noise.
Audio is a high-bandwidth data channel built into the human brain, there's no way military craft would not take advantage of it to convey information to the pilot. (Such as whether enemy ships are flying towards or away from you...)
The volume of the sound decays exponentially, so you can hear anything unless you are very close like the membranes in this experiment (0.0004 millimeters = 0.00016 inches = 2 small virus).
If you can hear the sound of the Death Star though vacuum, you are going to crash very soon (specially when it is exploding).
Here is an readable, blog-style rebuttal of the claim that zero point energy is harnessable as an infinite energy source:
https://scienceblogs.com/principles/2011/05/11/the-real-poin...
And here is a video debunking:
The results suggest another interesting experiment with dissimilar heat conductors separated by vacuum. Perhaps a heat pump on a small scale could be built.