6 ms·

There is also a recent hypothesis that doesn't require anything 'dark' > It is shown that reduction of the gravitational mass of the system due to emitting gra

by lstodd 9y ago

There is also a recent hypothesis that doesn't require anything 'dark' > It is shown that reduction of the gravitational mass of the system due to emitting gravitational waves leads to a repulsive gravitational force that diminishes with time but never disappears. This repulsive force may be related to the observed expansion of the Universe. https://arxiv.org/abs/1608.01541 https://arxiv.org/abs/1608.01541 Published in MNRAS https://doi.org/10.1093/mnras/stw1517 https://doi.org/10.1093/mnras/stw1517 In their other work they try to explain the EM-drive as a crude detector of high-frequency (GHz range) gravitational wave background.

eli_gottlieb 9y ago
Sounds kooky. But... the Royal Astronomical Society is publishing it?
- lstodd 9y ago
  The math in the original article is more or less solid, no errors were found since publication in 2016. The EM-drive idea is an attempt at an experiment to prove/disprove that the math has any relation to the reality. edit: inventing undetectable dark this or dark that sounds way more kookier than this.
  - acqq 9y ago
    From the 1608.01541 (2016) paper you linked: "We hope that our theoretical prediction about decreasing acceleration of the Universe can be verified by observations." But the observations actually see the opposite, the increasing acceleration, verified enough that five years before that paper, the 2011 Nobel Prize in Physics was for that discovery of the increasing acceleration, based on the measurements of Ia supernovae: https://www.nobelprize.org/nobel_prizes/physics/laureates/2011/press.html https://www.nobelprize.org/nobel_prizes/physics/laureates/20... "What will be the final destiny of the Universe? Probably it will end in ice, if we are to believe this year's Nobel Laureates in Physics. They have studied several dozen exploding stars, called supernovae, and discovered that the Universe is expanding at an ever-accelerating rate. The discovery came as a complete surprise even to the Laureates themselves."
    - lstodd 9y ago
      I'm not a scientist. I can only post links and say "let's see, this might have some merit". The authors (or at least N. Gorkavyi) recently (12th Sep) announced a new paper (literally "it's in print" whatever that means) that as far as I understand tackles the question. A crude translation of the announcement: > In the second article, (in print) we show that the reverse process - growth of the black holes by consumption of high-frequency gravitational waves - is the cause of the currently observed increasing acceleration of the expansion of the Universe. We have even got the correct value of the cosmological constant, solving the problem which is about a hundred years old. Might be the hope that you quoted was about surviving long enough to witness the acceleration to cease increasing. edit: spelling
      - acqq 9y ago
        Looking at who cited the paper you gave, I've found only one, and there is actually one rebuttal of the paper that cited the former: https://arxiv.org/abs/1708.00799 https://arxiv.org/abs/1708.00799 The authors of the rebuttal of that paper write: "Since those early years, a discussion took place on the different geodesics that can be written using local or non-local coordinates. Large accounts were published on this debate [10, 12–14]. Two sort of claims are recurring. Ignoring previous literature, there is a long list of scholars who pretend having discovered repulsion. They are listed in [10, 12–14]. The other concerns the attribution of physical consequences in the local environment of the falling body. For dismantling the latter claim, we follow the analysis by Cavalleri and Spinelli [15, 16]." "It is a coordinate effect appearing to an observer at a remote distance from the black hole and when coordinate time is employed. Repulsion has no bearing and relation to the local physics of the black hole, and moreover it cannot be held responsible for accelerating outgoing particles. Thereby, the energy boost of cosmic rays cannot be produced by repulsion." The rebutted paper doesn't have the same topic as the one you cite, so it doesn't have to mean too much or anything. But it hints about the way the "repulsion" claims can be problematic: "The main shortcoming of [17] is the assumption that repulsion, type i), is a physical effect and not just a coordinate effect. In other words, repulsion is only present when coordinate time is adopted and cannot explain phenomena local to the source, and ruled by proper time." However the lack of other responses to the paper you cite is so big at the moment that I don't expect much of it. Is there any response to the paper you cite, by any scientist, that you are aware of? But I see that the guy is productive, and produced dubious papers before, so much that he doesn't list them himself but that could be found: http://adsabs.harvard.edu/abs/2005AAS...206.4904G http://adsabs.harvard.edu/abs/2005AAS...206.4904G The Pioneer anomaly is currently considered solved, https://en.wikipedia.org/wiki/Pioneer_anomaly https://en.wikipedia.org/wiki/Pioneer_anomaly and definitely not the way he attempted to do, just like now he mentions then "a total energy of relic high-frequency gravitational radiation in our Universe" etc. So I'm not holding my breath for his next paper. Edit: thanks for the link to his Russian blog. It seems even weirder than I could imagine, I haven't tried Google translate, but just looking, it appears that in one post he first writes about the EM drive stuff and only then he mentions that he apparently solved all the cosmological problems? Wow, he has his priorities. A typical troll, the way I see him.
  - spullara 9y ago
    I dropped out of my physics phd program so take it with a grain of salt but I have never been a fan of dark matter or really any of the new theories that attempt to explain the expansion of the universe or propose things far outside the standard model (like string theory). These measurements are super interesting as they can falsify so many crazy ideas.
    - philipov 9y ago
      I'm a fan of Penrose's idea that inflation is actually the image of the infinite time boundary of a previous universe, and that there was no big bang at all, just a sequence of nested time domains. [0]: https://www.youtube.com/watch?v=npmDbbGbSoE https://www.youtube.com/watch?v=npmDbbGbSoE
    - wallace_f 9y ago
      As an outside observer the mystery of dark matter is interesting, but I can agree that the theories are not always so fun. My entirely uneducates idea is that dark matter probably is some by-product of what's going on in that place of the universe we know nothing about: inside black holes--maybe spacetime curvature can only be so deep and hits a floor, spreading out in a halo around galaxies? This would be consistent with dark matter hanging out around galaxies, but not interstellar dust clouds, and also being proportional to the size of the galaxies, which is proportional to their central supermassive blackholes. Anyways this is just a wildly uneducated "arm-chair" hypothesis, but it just possibly seems when comparing this to some of the wild theoties out there, that it would be more likely a product of a known-unknown (interior of black holes), and not an unknown-unknown (new particles, new laws of physics). In that sense, if it's not ruled out already (it probably is, someone else must have thought of it), it's less crazy than modified gravity apparently was.
  - Florin_Andrei 9y ago
    > inventing undetectable dark this or dark that sounds way more kookier than this It's not really "invented". People get stuck on names way too much, forgetting these are simply placeholders, stopgap measures for a still incomplete, but evolving, understanding of nature.
    - lstodd 9y ago
      You are right, 'inventing' the wrong word, and the same can be said about 'kooky'. Still, gravitation waves were detected, while darks were not.
    - KGIII 9y ago
      I'm pretty sure the two names of 'dark matter' and 'dark energy' have caused more confusion than anything else in modern science. They were horrible choices that were worse than even the 'god particle.' Horrible. Explaining they are placeholders has actually eaten up a fair amount of my time. I'm betting I've probably spent days, if we total the hours up, explaining just that. (I like to go make science simple for people. Having to explain that it is a placeholder doesn't make it easy. So much wasted time.)
      - Florin_Andrei 9y ago
        I agree that the name choices were unfortunate.
  - magicalist 9y ago
    > inventing undetectable dark this or dark that sounds way more kookier than this Just because something doesn't interact with light doesn't mean it's undetectable. The reason we posit it's there is because we detect it. Agree with Florin_Andrei. If they had just named it skotonic matter or something, no one would have these objections. It's a working model with growing evidence to support it. That's it. And if weird types and states of matter that we haven't been able to detect directly is really an issue, I have bad news about virtually all our knowledge of particle and stellar physics...
  - enraged_camel 9y ago
    Dark matter may not have been detected yet, but we don't need to detect things directly to prove their existence. Sometimes, enough circumstantial evidence is sufficient. For example, if you see a human-shaped shadow around the corner, you can safely assume that it's probably a human, even if you can't see them directly. It may of course turn out to be something else (maybe a scarecrow!) but that's okay. Black holes are similar: we can't observe them directly but we can detect their gravitational effects, such as the way they bend light around them.
- acqq 9y ago
  One relevant reaction to this paper (especially because there was no direct agreement with the article by any scientist) is here: https://arxiv.org/abs/1608.07136 https://arxiv.org/abs/1608.07136 "Every now and then some confused authors use wrong, non-covariant, definitions of velocity, acceleration and gravity, based on their vague Newtonian intuitions and hidden in a superficial, often purely semantic, relativistic disguise. A recent example of such a confusion (Gorkavyi & Vasilkov, 2016) is discussed at the end of this Note." It concludes: "The paper by Gorkavyi & Vasilkov (2016) is not even wrong, it is simply a nonsense. The only question that may be of interest here is — how such a paper could possibly slip into the Monthly Notices of the Royal astronomical Society? I may offer just one explanation. I was told a story, perhaps apocryphal, about a famous referee report (many years ago) by Jim Pringle: “The paper is so obviously wrong that it should be published as it stands”." Regarding Gorkavyi's linking of EM drive and his hypotheses, he tried the same with the Pioneer anomaly, but the anomaly was eventually explained completely without that, so it really seems that he looks for anything "unexplained" at the moment to popularize himself, knowing enough formulas to casually appear as he knows what he talks about, but inventing his new semantic out of thin air.
- gfody 9y ago
  depends how you calibrate kooky. how do you feel about plasma cosmology?
acqq 9y ago
Even if you wrote in your later replies here that (your words follow) "the math in the original article is more or less solid, no errors were found since publication in 2016" that statement seems quite dishonest, as you also wrote later, as you communicated with me, that you are aware of the direct rebuttal, which was published shortly after the article appeared, which I link here and quote the abstract if full: https://arxiv.org/abs/1608.02882 https://arxiv.org/abs/1608.02882 "We show that a recent assertion [arXiv:1608.01541] that gravitational wave emission can lead to a repulsive force explaining the accelerated expansion of the Universe is totally unfounded." I think it can't be shorter and more precise. I also thank you here for the information about that rebuttal article, as well as about another article which mentions how wrong the Gorkavyi's article is https://arxiv.org/abs/1608.07136 https://arxiv.org/abs/1608.07136 both of which I haven't been aware of before the communication with you.

by lstodd 9y ago

eli_gottlieb 9y ago

Sounds kooky. But... the Royal Astronomical Society is publishing it?

lstodd 9y ago
The math in the original article is more or less solid, no errors were found since publication in 2016. The EM-drive idea is an attempt at an experiment to prove/disprove that the math has any relation to the reality. edit: inventing undetectable dark this or dark that sounds way more kookier than this.
- acqq 9y ago
  From the 1608.01541 (2016) paper you linked: "We hope that our theoretical prediction about decreasing acceleration of the Universe can be verified by observations." But the observations actually see the opposite, the increasing acceleration, verified enough that five years before that paper, the 2011 Nobel Prize in Physics was for that discovery of the increasing acceleration, based on the measurements of Ia supernovae: https://www.nobelprize.org/nobel_prizes/physics/laureates/2011/press.html https://www.nobelprize.org/nobel_prizes/physics/laureates/20... "What will be the final destiny of the Universe? Probably it will end in ice, if we are to believe this year's Nobel Laureates in Physics. They have studied several dozen exploding stars, called supernovae, and discovered that the Universe is expanding at an ever-accelerating rate. The discovery came as a complete surprise even to the Laureates themselves."
  - lstodd 9y ago
    I'm not a scientist. I can only post links and say "let's see, this might have some merit". The authors (or at least N. Gorkavyi) recently (12th Sep) announced a new paper (literally "it's in print" whatever that means) that as far as I understand tackles the question. A crude translation of the announcement: > In the second article, (in print) we show that the reverse process - growth of the black holes by consumption of high-frequency gravitational waves - is the cause of the currently observed increasing acceleration of the expansion of the Universe. We have even got the correct value of the cosmological constant, solving the problem which is about a hundred years old. Might be the hope that you quoted was about surviving long enough to witness the acceleration to cease increasing. edit: spelling
    - acqq 9y ago
      Looking at who cited the paper you gave, I've found only one, and there is actually one rebuttal of the paper that cited the former: https://arxiv.org/abs/1708.00799 https://arxiv.org/abs/1708.00799 The authors of the rebuttal of that paper write: "Since those early years, a discussion took place on the different geodesics that can be written using local or non-local coordinates. Large accounts were published on this debate [10, 12–14]. Two sort of claims are recurring. Ignoring previous literature, there is a long list of scholars who pretend having discovered repulsion. They are listed in [10, 12–14]. The other concerns the attribution of physical consequences in the local environment of the falling body. For dismantling the latter claim, we follow the analysis by Cavalleri and Spinelli [15, 16]." "It is a coordinate effect appearing to an observer at a remote distance from the black hole and when coordinate time is employed. Repulsion has no bearing and relation to the local physics of the black hole, and moreover it cannot be held responsible for accelerating outgoing particles. Thereby, the energy boost of cosmic rays cannot be produced by repulsion." The rebutted paper doesn't have the same topic as the one you cite, so it doesn't have to mean too much or anything. But it hints about the way the "repulsion" claims can be problematic: "The main shortcoming of [17] is the assumption that repulsion, type i), is a physical effect and not just a coordinate effect. In other words, repulsion is only present when coordinate time is adopted and cannot explain phenomena local to the source, and ruled by proper time." However the lack of other responses to the paper you cite is so big at the moment that I don't expect much of it. Is there any response to the paper you cite, by any scientist, that you are aware of? But I see that the guy is productive, and produced dubious papers before, so much that he doesn't list them himself but that could be found: http://adsabs.harvard.edu/abs/2005AAS...206.4904G http://adsabs.harvard.edu/abs/2005AAS...206.4904G The Pioneer anomaly is currently considered solved, https://en.wikipedia.org/wiki/Pioneer_anomaly https://en.wikipedia.org/wiki/Pioneer_anomaly and definitely not the way he attempted to do, just like now he mentions then "a total energy of relic high-frequency gravitational radiation in our Universe" etc. So I'm not holding my breath for his next paper. Edit: thanks for the link to his Russian blog. It seems even weirder than I could imagine, I haven't tried Google translate, but just looking, it appears that in one post he first writes about the EM drive stuff and only then he mentions that he apparently solved all the cosmological problems? Wow, he has his priorities. A typical troll, the way I see him.
- spullara 9y ago
  I dropped out of my physics phd program so take it with a grain of salt but I have never been a fan of dark matter or really any of the new theories that attempt to explain the expansion of the universe or propose things far outside the standard model (like string theory). These measurements are super interesting as they can falsify so many crazy ideas.
  - philipov 9y ago
    I'm a fan of Penrose's idea that inflation is actually the image of the infinite time boundary of a previous universe, and that there was no big bang at all, just a sequence of nested time domains. [0]: https://www.youtube.com/watch?v=npmDbbGbSoE https://www.youtube.com/watch?v=npmDbbGbSoE
  - wallace_f 9y ago
    As an outside observer the mystery of dark matter is interesting, but I can agree that the theories are not always so fun. My entirely uneducates idea is that dark matter probably is some by-product of what's going on in that place of the universe we know nothing about: inside black holes--maybe spacetime curvature can only be so deep and hits a floor, spreading out in a halo around galaxies? This would be consistent with dark matter hanging out around galaxies, but not interstellar dust clouds, and also being proportional to the size of the galaxies, which is proportional to their central supermassive blackholes. Anyways this is just a wildly uneducated "arm-chair" hypothesis, but it just possibly seems when comparing this to some of the wild theoties out there, that it would be more likely a product of a known-unknown (interior of black holes), and not an unknown-unknown (new particles, new laws of physics). In that sense, if it's not ruled out already (it probably is, someone else must have thought of it), it's less crazy than modified gravity apparently was.
- Florin_Andrei 9y ago
  > inventing undetectable dark this or dark that sounds way more kookier than this It's not really "invented". People get stuck on names way too much, forgetting these are simply placeholders, stopgap measures for a still incomplete, but evolving, understanding of nature.
  - lstodd 9y ago
    You are right, 'inventing' the wrong word, and the same can be said about 'kooky'. Still, gravitation waves were detected, while darks were not.
  - KGIII 9y ago
    I'm pretty sure the two names of 'dark matter' and 'dark energy' have caused more confusion than anything else in modern science. They were horrible choices that were worse than even the 'god particle.' Horrible. Explaining they are placeholders has actually eaten up a fair amount of my time. I'm betting I've probably spent days, if we total the hours up, explaining just that. (I like to go make science simple for people. Having to explain that it is a placeholder doesn't make it easy. So much wasted time.)
    - Florin_Andrei 9y ago
      I agree that the name choices were unfortunate.
- magicalist 9y ago
  > inventing undetectable dark this or dark that sounds way more kookier than this Just because something doesn't interact with light doesn't mean it's undetectable. The reason we posit it's there is because we detect it. Agree with Florin_Andrei. If they had just named it skotonic matter or something, no one would have these objections. It's a working model with growing evidence to support it. That's it. And if weird types and states of matter that we haven't been able to detect directly is really an issue, I have bad news about virtually all our knowledge of particle and stellar physics...
- enraged_camel 9y ago
  Dark matter may not have been detected yet, but we don't need to detect things directly to prove their existence. Sometimes, enough circumstantial evidence is sufficient. For example, if you see a human-shaped shadow around the corner, you can safely assume that it's probably a human, even if you can't see them directly. It may of course turn out to be something else (maybe a scarecrow!) but that's okay. Black holes are similar: we can't observe them directly but we can detect their gravitational effects, such as the way they bend light around them.
acqq 9y ago
One relevant reaction to this paper (especially because there was no direct agreement with the article by any scientist) is here: https://arxiv.org/abs/1608.07136 https://arxiv.org/abs/1608.07136 "Every now and then some confused authors use wrong, non-covariant, definitions of velocity, acceleration and gravity, based on their vague Newtonian intuitions and hidden in a superficial, often purely semantic, relativistic disguise. A recent example of such a confusion (Gorkavyi & Vasilkov, 2016) is discussed at the end of this Note." It concludes: "The paper by Gorkavyi & Vasilkov (2016) is not even wrong, it is simply a nonsense. The only question that may be of interest here is — how such a paper could possibly slip into the Monthly Notices of the Royal astronomical Society? I may offer just one explanation. I was told a story, perhaps apocryphal, about a famous referee report (many years ago) by Jim Pringle: “The paper is so obviously wrong that it should be published as it stands”." Regarding Gorkavyi's linking of EM drive and his hypotheses, he tried the same with the Pioneer anomaly, but the anomaly was eventually explained completely without that, so it really seems that he looks for anything "unexplained" at the moment to popularize himself, knowing enough formulas to casually appear as he knows what he talks about, but inventing his new semantic out of thin air.
gfody 9y ago
depends how you calibrate kooky. how do you feel about plasma cosmology?

acqq 9y ago

Even if you wrote in your later replies here that (your words follow) "the math in the original article is more or less solid, no errors were found since publication in 2016" that statement seems quite dishonest, as you also wrote later, as you communicated with me, that you are aware of the direct rebuttal, which was published shortly after the article appeared, which I link here and quote the abstract if full: https://arxiv.org/abs/1608.02882 https://arxiv.org/abs/1608.02882 "We show that a recent assertion [arXiv:1608.01541] that gravitational wave emission can lead to a repulsive force explaining the accelerated expansion of the Universe is totally unfounded." I think it can't be shorter and more precise. I also thank you here for the information about that rebuttal article, as well as about another article which mentions how wrong the Gorkavyi's article is https://arxiv.org/abs/1608.07136 https://arxiv.org/abs/1608.07136 both of which I haven't been aware of before the communication with you.