New Gravity



  • Very interesting. I've always thought that dark matter was an ugly kludge which would eventually be discarded like epicycles.

    Actual paper here.

    Using insights from string theory, black hole physics and quantum
    information theory we argue that the positive dark energy leads to a thermal
    volume law contribution to the entropy that overtakes the area law precisely at
    the cosmological horizon.

    So...does this also herald potential confirmation of string theory?


  • area_can

    @boomzilla said in New Gravity:

    Very interesting. I've always thought that dark matter was an ugly kludge which would eventually be discarded like epicycles.

    In that it's basically a placeholder, yeah


  • Winner of the 2016 Presidential Election

    @boomzilla said in New Gravity:

    I've always thought that dark matter was an ugly kludge

    Yeah, it's never sat right with me. When you have to propose that 80% of all mass is hidden out there with Russel's Teapot to explain a theory that's all about mass, it starts to look suspicious.

    Does this suggest a route to combining gravity and quantum physics as well?


  • Winner of the 2016 Presidential Election

    I'd have to read into it a bit more. The article is a bit clunky, going on about Newton's theory of gravity (which basically explains nothing and we just use it as a "close enough" mathematical model when applicable) and mentions general relativity just in passing.

    Also, from what little it said in there I don't see how it completely blows general relativity out of the water anyway. If spacetime can be quantized into distinct "units of information" there's no reason to immediately say that the current explanation of gravity wells doesn't work any more - instead of a rubber sheet analogy it might just as well be a chainmail-like structure, with individual loops being the "units of information" as proposed here.

    Yes, I know the analogy isn't perfect, but neither was the rubber sheet one anyway.



  • @Onyx said in New Gravity:

    Yes, I know the analogy isn't perfect, but neither was the rubber sheet one anyway.

    I'm holding out for the car analogy of gravity.



  • @boomzilla said in New Gravity:

    the car analogy of gravity.

    But is it a compact or a truck?


  • Grade A Premium Asshole

    @boomzilla said in New Gravity:

    I've always thought that dark matter was an ugly kludge

    Me too. It always seemed like some physicists looked at the end of the equation, thought "If we make this number a minus...it all works out right, but I have no clue why".


  • Grade A Premium Asshole

    @Luhmann said in New Gravity:

    @boomzilla said in New Gravity:

    the car analogy of gravity.

    But is it a compact or a truck?

    It is a Tesla. It occasionally steers in to large objects and kills everyone.


  • Discourse touched me in a no-no place

    @boomzilla said in New Gravity:

    Very interesting. I've always thought that dark matter was an ugly kludge which would eventually be discarded like epicycles.

    Dark energy is the truly ugly kludge, dark matter is the “oh, we can't seem to see everything required to explain the layout of the universe” kludge that is a heck of a lot less nausea-inducing since at least it doesn't involve flipping the sign on gravity. That there is some stuff out there that is truly difficult to detect isn't very controversial, but just how much and what it is is rather complicated; by contrast, dark energy is so crazy that people were really hoping that it was some sort of weird epicycle due to current theory being wrong.

    Personally, I've been wondering what effect a fractal distribution of matter would have, since then you'd have interesting matter distribution without violating the Cosmological Principle (that we're nowhere special). However, I also know that I've not got the math skills to work that out.



  • @dkf said in New Gravity:

    I also know that I've not got the math skills to work that out

    It's not completely implausible that nobody ever will have those skills.

    Even a simply specified three-body Newtonian model has no analytical solution.

    It pleases me to think of our best current theories as rare shining little lights embedded in the unimaginable volume of Dark Ignorance.


  • Discourse touched me in a no-no place

    @flabdablet said in New Gravity:

    It's not completely implausible that nobody ever will have those skills.

    I don't mean an exact solution. ;) I meant that I can't even see far enough through the problem to know if a fractal matter distribution would make the sort of difference that actually substantively changes things; I know that it would be consistent with the Cosmological Principle on the grounds that at least some fractals have no meaningful edge and no particular special configuration. (Alternatively, the fractal might actually be in some sort of inverse space, rather analogous to a fourier transform or stereographic projection.)

    But marrying the whole business of fractals with string theory (two quite different areas of mathematics AIUI) is a really tall order; totally beyond my skills. Then there are the more exotic MOND-like theories which would need this sort of thing doing too and it all needs a professional mathematician to make any progress, and that's definitely not me.



  • You heathens and your "science".

    God created Adam and Eve not Atoms and Strings.


  • sockdevs

    @Bort said in New Gravity:

    You heathens and your "science".

    God created Adam and Eve not Atoms and Strings.

    s/Atoms/Adams/g

    s/Strings/Eves/g

    there. fixed it for you.



  • @Bort said in New Gravity:

    God created Adam and Eve not Atoms and Strings.

    Indeed. If God had created Strings, Adam and Eve wouldn’t have had to make clothes for themselves out of Fig Leaves.



  • I've never understood the irritation that dark matter seems to engender. I see so many geeks call it an obviously wrong kludge and that seem to think it's a conspiracy among physicists to keep the idea alive (not accusing anyone here, mostly Slashdot and blog commentators). I mean, if dark matter is a new kind of particle, cool! If it's a wrinkle in the dynamics of spacetime, cool! I don't understand people who seem personally offended at the theory.

    Dark matter isn't even the first such theory. Neutrinos were a kludge to preserve momentum and energy conservation in nuclear reactions; it took 26 years to actually detect them. Neptune was a kludge to explain the fact that Uranus was moving weirdly (pre-:giggity: ); actually seeing Neptune took 25 years.

    Then again, the planet Vulcan was a kludge to explain why Mercury was moving incorrectly. Turns out a modified gravity was the answer: General Relativity.

    I'm going to attempt to read the paper, but as a physics grad school dropout, I'm not expecting much detailed understanding.


  • :belt_onion:

    @boomzilla said in New Gravity:

    @Onyx said in New Gravity:

    Yes, I know the analogy isn't perfect, but neither was the rubber sheet one anyway.

    I'm holding out for the car analogy of gravity.

    Car analogies are the Cadillac of analogies.



  • @MZH I personally find dark matter an awesome idea, in hope for it to be something interesting.

    After Mars and that comet were revealed to be boring as fuck, I can dream they find life made of dark matter or something.



  • @MZH said in New Gravity:

    I don't understand people who seem personally offended at the theory.

    I'm not offended, I just never bought it as anything more than a kludge that was unlikely to stand the test of time.



  • @boomzilla Ever since I saw the pictures of the Bullet Cluster, showing that the apparent distribution of dark matter can be independent of normal matter, I've been convinced that dark matter is an actual material thing. But, I'm not involved in any of the research (astronomical or direct detection), so I'm just watching the science play out. New physics or new kinds of matter are both cool.



  • @dkf said in New Gravity:

    Dark energy is the truly ugly kludge

    Here's a bucket for shit we don't know but have an equation that works.



  • Fuck your "new" ideas. My roux + drippings has worked perfectly until now, and will keep working perfectly. MAYBE a hint of cayenne or black pepper, but that's as far as I'm willing to go.



  • @Lorne-Kates said in New Gravity:

    My roux + drippings has worked perfectly until now, and will keep working perfectly.

    Feed me or it didn't happen!



  • @boomzilla said in New Gravity:

    @Lorne-Kates said in New Gravity:

    My roux + drippings has worked perfectly until now, and will keep working perfectly.

    Feed me or it didn't happen!

    I'll crank up the oven and get a rib roast ready.

    All you have to do is come to Canada. You should be able to find the place easily enough. Just follow the hoards of fleeing Americans.

    (Complete sidenote: I wonder if anyone has ever done a study of America -> Canada emigration after an election/proposition? Or is it all just talk?)



  • @Lorne-Kates said in New Gravity:

    Or is it all just talk?

    No one actually wants to move to Canada.



  • @boomzilla said in New Gravity:

    @Lorne-Kates said in New Gravity:

    Or is it all just talk?

    No one actually wants to move to Canada.

    True. Our country is made up 100% of people who aimed for America and missed.

    And that's why they invented The Compass.

    But Canada's population started to decline, so every year we slightly shift the magnetic North Pole-- to ensnare just enough weary oceanic travelers.



  • @Lorne-Kates said in New Gravity:

    But Canada's population started to decline, so every year we slightly shift the magnetic North Pole-- to ensnare just enough weary oceanic travelers.

    The Northwest Passage seems much more sinister to me now.



  • @Lorne-Kates Gumbo is hard to cook just right.

    But I was surprised at how easy etouffee is in comparison even though the principle is the same.


  • :belt_onion:

    @Lorne-Kates said in New Gravity:

    @boomzilla said in New Gravity:

    @Lorne-Kates said in New Gravity:
    I wonder if anyone has ever done a study of America -> Canada emigration after an election/proposition? Or is it all just talk?)

    Americans hear talk about free poutine and get excited. But it doesn't last.


  • Impossible Mission - B

    @MZH said in New Gravity:

    I've never understood the irritation that dark matter seems to engender. I see so many geeks call it an obviously wrong kludge and that seem to think it's a conspiracy among physicists to keep the idea alive (not accusing anyone here, mostly Slashdot and blog commentators). I mean, if dark matter is a new kind of particle, cool! If it's a wrinkle in the dynamics of spacetime, cool! I don't understand people who seem personally offended at the theory.

    Dark matter isn't even the first such theory. Neutrinos were a kludge to preserve momentum and energy conservation in nuclear reactions; it took 26 years to actually detect them. Neptune was a kludge to explain the fact that Uranus was moving weirdly (pre-:giggity: ); actually seeing Neptune took 25 years.

    That's just the thing: neutrinos and Neptune were eventually found.

    The theory of Dark Matter is literally "the vast majority of matter out there is stuff that will never be found because it can never be found, because it doesn't interact with the observable world in any way at all except for gravitation, because that's the only way we can explain why observed gravitational effects don't track at all with observable matter in the universe."

    And that offends a lot of people's sensibilities.

    @fbmac said in New Gravity:

    After Mars and that comet were revealed to be boring as fuck, I can dream they find life made of dark matter or something.

    Read Schlock Mercenary sometime. (Warning: enormous archive binge. It's a daily strip. The author started in 2000. He has never missed a single update! But it's been consistently funny for 16 years, and the quality just keeps getting better as it goes along. It's widely regarded as one of the best webcomics around.)

    A few years in, there's a major plot arc dedicated to a clash with "dark matter entities" that ends up reshaping the entire future of the galaxy.



  • @MZH I read a relatively hard scifi novel that touched on the idea at one point, and like to think of it their way, whether or not it's quite accurate, but it worked kind of like this:

    Our galaxy acts like a disk. For the most part, things in it move like they would etched on a disk, rather than just free-floating. And that's kind of weird, because the way they move would require a disk made of ten times as much matter as we can observe, and maybe the anchor points are the centers of stars?

    I sure hope that someone has defined it better than that.



  • @masonwheeler said in New Gravity:

    That's just the thing: neutrinos and Neptune were eventually found.

    The theory of Dark Matter is literally "the vast majority of matter out there is stuff that will never be found because it can never be found, because it doesn't interact with the observable world in any way at all except for gravitation, because that's the only way we can explain why observed gravitational effects don't track at all with observable matter in the universe."
    And that offends a lot of people's sensibilities.

    The important word being eventually. Also, nobody says that dark matter can't interact with anything except through gravity. Gravity is just the most obvious and easiest to observe interaction. Here are two candidates for the identity of dark matter:

    • WIMPs: Weakly Interacting Massive Particles that also feel the weak nuclear force. A more massive neutrino (aka, a sterile neutrino) would fit here quite nicely. Current searches involve large scintillating detectors in deep underground mines waiting for the occassional dark matter particle to bump into an atom of germanium or xenon.
    • Axions: theoretical particles that came out of studies of the strong nuclear force and electromagnetism. Current searches involve strong magnets that cause modulations of electromagnetic radiation due to their presence. Effects might also be seen in Josephson junctions and topological insulators.

    The method of detecting dark matter particles depends on what kind of particle it is, so there is no one experiment that can rule out the existence of dark matter, just individual candidate types. The search for WIMPs and axions involve very different experiments, and each experiment searches a different parameter space (mass vs. interaction strength, for example). I can't think of a Michelson-Morley type experiment that would rule out the entire idea in one go. Perhaps, eventually, after decades of null results, physicists will give up on the idea of dark matter. But that is a long way away. It was 44 years in between the first Higgs boson papers and its discovery in the LHC. Physicists are used to waiting a long time for experiments to catch up with theory.

    Getting back to the original topic, I find it interesting that string theory, which has had no connection with experiment since its inception, gets a lot less grief than dark matter.



  • @MZH said in New Gravity:

    I find it interesting that string theory, which has had no connection with experiment since its inception, gets a lot less grief than dark matter.

    Does it? I've always gotten the impression that it was the other way around, though I'm certainly a layman and and outsider to the sorts of people who would know. But I'm aware that a lot of physicists think string theory is bad.

    I've never really heard of any similar "professional" push back on dark matter.



  • @boomzilla You're right, there's little disagreement among professionals about dark matter. Even modified gravity proponents have to include some sort of dark matter in their models to fit the wide variety of astronomical data. It's among laymen where I see the most opposition--including all the "kludge" and "epicycle" comments here.

    There's a lot less laymen commentary on string theory due to its highly technical and mathematical--bordering on esoteric--nature. Most wide press coverage it gets focus on the 11 or 26 dimensions of space it requires, along with analogies of particles as vibrating stings like musical instruments. I think most mainstream press coverage stopped in the late 90s.

    There has been grumbling amongst professional physicists regarding string theory. At first, it was mostly about how string theory gets most of the grant money and graduate students in theoretical physics at the expense of other areas, then about its empirical barrenness. Lately, there are some string theorists advocating for redefining science to include non-empirical evidence for theories, including mathematical elegance and simplicity. This has not sat well with most physicists. There was an interesting conference on this issue back in December: Why Trust a Theory? Now that the lecture videos are up, I should give this conference another look.



  • CalTech physicist Sean Carroll talks about dark matter and dark energy, including the paper mentioned in the OP.




  • :belt_onion:

    @boomzilla said in New Gravity:

    @MZH said in New Gravity:

    I find it interesting that string theory, which has had no connection with experiment since its inception, gets a lot less grief than dark matter.

    Does it? I've always gotten the impression that it was the other way around, though I'm certainly a layman and and outsider to the sorts of people who would know. But I'm aware that a lot of physicists think string theory is bad.

    I've never really heard of any similar "professional" push back on dark matter.

    String theory has been around for a long time and people have gotten tired of ridiculing it. Dark Matter is now the new kid on the block.



  • @Onyx Correct me if I am wrong, but wouldn't a quantized model of space be at odds with the entire foundation of Newton's model (and by extension, Einstein's), because it would imply that motion is not a smooth integral, but a discontinuous series? I'm not a physicist, but when I asked a physics professor about quantized space-time, he dismissed it as being incompatible with inertia, because inertia requires a smooth motion. Whether he was wrong, or misunderstood me, or I misunderstood him, I don't know, which is why I ask if that would present a problem.

    Filed Under: On the plus side, it would imply that we live in a Fullerian geometry universe, and can discard all that messy business about real units and stick to whole number ones. In principle, anyway.


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    @ScholRLEA said in New Gravity:

    I'm not a physicist, but when I asked a physics professor about quantized space-time, he dismissed it as being incompatible with inertia, because inertia requires a smooth motion.

    At which level, though? It's a long standing theory that electron's energy levels in an atom, for example, are quantized, not continuous. Now, I know inertia and electron energy levels don't have any direct links (that we know of, at least), but it shows that the concept isn't unheard of in physics.

    We can simulate motion in a computer pretty damned well without any particular tricks, despite floating point imprecision. I don't see why the same thing couldn't be possible in a physical space. After all, we still can't measure stuff at Planck length, let alone anything smaller. A grid might be there, just too small for us to see.

    Of course, this is all ramblings of a madlayman, but hey, it's fun! :P







  • @Onyx @ScholRLEA There was an experiment at Fermilab specifically testing one theory of quantized spacetime that published results in December. A pixelated universe is ruled out for now.



  • @ScholRLEA said in New Gravity:

    I'm not a physicist, but when I asked a physics professor about quantized space-time, he dismissed it as being incompatible with inertia, because inertia requires a smooth motion.

    I'm not a mathematician, but my intuition says that that would depend on the minimum possible spacetime separation between distinguishable events.

    If spacetime has anything like an inbuilt Nyquist limit, then there ought to exist a discrete-spacetime model compatible in every respect with a continuous-spacetime one.

    Which would of course leave the question of whether the Universe is "really" discrete rather than "really" continuous completely open.



  • @flabdablet Hmmn, OK, I wouldn't really be able to judge that myself, from either a physical or mathematical perspective, but that does give me a little bit of a handle on it, I think.


  • Discourse touched me in a no-no place

    @ScholRLEA said in New Gravity:

    Correct me if I am wrong, but wouldn't a quantized model of space be at odds with the entire foundation of Newton's model (and by extension, Einstein's), because it would imply that motion is not a smooth integral, but a discontinuous series?

    Yes. That's exactly why the unification of quantum theory with gravitation is so bloody difficult. It doesn't help that both the Standard Model and General Relativity give such accurate results; it isn't clear what the problem really is.

    String theory makes a bunch of predictions, but nobody knows if any of them apply to this universe…


  • Winner of the 2016 Presidential Election

    @MZH Stupid science, ruining my fun!


    Filed under: Fucking Illuminati


  • Discourse touched me in a no-no place

    @Onyx said in New Gravity:

    Filed under: Fucking Illuminati

    :giggitinati:



  • @Onyx said in New Gravity:

    Filed under: Fucking Illuminati

    Isn't the illuminati all old men?


  • Winner of the 2016 Presidential Election

    @PleegWat Yes! That's why they keep perpetuating the spherical Earth myth! That's the only ball(s) they have left!


    Filed under: I done got derailed it, haven't I?, Sorry!


  • Discourse touched me in a no-no place

    @Onyx said in New Gravity:

    hat's why they keep perpetuating the spherical Earth myth! That's the only ball(s) they have left!

    But at least it's (mostly) blue…



  • @PleegWat said in New Gravity:

    Isn't the illuminati all old men?

    That's what they want you to think.


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