4 ms·

This feels under-described. Why are they implying that radiant heat (photons) don’t travel hundreds of nanometers? Is it an energy/wavelength mismatch issue?

Diggsey 7y ago
The article explains that the heat transfer is too great to be explained by the black body radiation for the given temperature. 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?
- mannykannot 7y ago
  It helps to look into the Casimir effect, and in particular the dynamic aspect of it. 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_Casimir_effect https://en.wikipedia.org/wiki/Casimir_effect#Dynamical_Casim...
  - Iv 7y ago
    > at least until we are working at even smaller scales. 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.
    - Retric 7y ago
      Those nm scales are just marketing at this point, they don’t describe feature sizes.
      - Iv 7y ago
        Oh, I did not know that. Sigh why do journalists accept to go along with these lies? (No, don't answer, that's rhetorical). So apparently feature sizes are around 40 nm even in "7" or "10 nm" processes.
        mannykannot 7y ago
        Even so, ~1 atmosphere for a gap that is order-of-magnitude comparable to current technology is interesting, and higher than I would have guessed. On reflection, there's a correspondence between the frequency of the light needed in fabricating features of this size by photolithography, and the cut-off frequency for the Casimir effect in those features.
- jpmattia 7y ago
  It's the latter, ie 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.
WhitneyLand 7y ago
And maybe over promoted and/or inconsistent. It's said - 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?
- wuliwong 7y ago
  > Heat is usually conducted in a solid? I haven't heard it defined like that before. 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.
  - WhitneyLand 7y ago
    >How have you heard [heat] defined [other than "mostly through a solid"]? 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-increasing-in-science/ 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.

Diggsey 7y ago

The article explains that the heat transfer is too great to be explained by the black body radiation for the given temperature. 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?

mannykannot 7y ago
It helps to look into the Casimir effect, and in particular the dynamic aspect of it. 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_Casimir_effect https://en.wikipedia.org/wiki/Casimir_effect#Dynamical_Casim...
- Iv 7y ago
  > at least until we are working at even smaller scales. 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.
  - Retric 7y ago
    Those nm scales are just marketing at this point, they don’t describe feature sizes.
    - Iv 7y ago
      Oh, I did not know that. Sigh why do journalists accept to go along with these lies? (No, don't answer, that's rhetorical). So apparently feature sizes are around 40 nm even in "7" or "10 nm" processes.
      - mannykannot 7y ago
        Even so, ~1 atmosphere for a gap that is order-of-magnitude comparable to current technology is interesting, and higher than I would have guessed. On reflection, there's a correspondence between the frequency of the light needed in fabricating features of this size by photolithography, and the cut-off frequency for the Casimir effect in those features.
jpmattia 7y ago
It's the latter, ie 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.

WhitneyLand 7y ago

And maybe over promoted and/or inconsistent. It's said - 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?

wuliwong 7y ago
> Heat is usually conducted in a solid? I haven't heard it defined like that before. 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.
- WhitneyLand 7y ago
  >How have you heard [heat] defined [other than "mostly through a solid"]? 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-increasing-in-science/ 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.