[HN Gopher] Neutron Stars Hint at Another Dimension
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Neutron Stars Hint at Another Dimension
Author : dnetesn
Score : 116 points
Date : 2025-04-06 11:41 UTC (11 hours ago)
(HTM) web link (nautil.us)
(TXT) w3m dump (nautil.us)
| p_ing wrote:
| If anyone wants a super approachable lecture on Neutron stars,
| this was released just a couple of weeks ago -
| https://youtu.be/I12SQ7YOebY
| superjan wrote:
| That was a great watch, thanks!
| echelon wrote:
| To what degree are these Nautilus stories based off of the work
| of a single researcher or lab that does not have broader
| consensus amongst the research community?
|
| What's a good way for a layperson to tell if this is a new
| scientific consensus arrived at after hundreds of researchers
| come to the same conclusion or a breakthrough result that has
| shocked the entire research community?
| flufluflufluffy wrote:
| > "In 1999, theoretical physicists Lisa Randall and Raman
| Sundrum proposed a wild restructuring of the cosmos"
|
| > "The brane-bulk model is a speculative idea for sure, but a
| fun one."
|
| I feel like it's communicated pretty clearly that it isn't some
| breakthrough finding that everybody agrees on. You could google
| the mentioned researchers/theories and find out more
| information if you still weren't sure.
| patcon wrote:
| Agreed. Yes, a bit roundabout, but it's pretty wild that we
| live in a spot in the universe where the distance we need to
| travel to "confirm plausibility" of a "deep truth of the
| universe we just heard about" is just to type a few glyphs
| into a magic box and decide if the person speaking the
| purported truth has a reputation in the relevant human
| thought-stuffs.
|
| The world we live in is crazy. To know such a thing so easily
| at an earlier time, would be unfathomable :)
| superjan wrote:
| This is not consensus. There are lots of anomalies in what we
| observe in the cosmos. Here someone links two of those to a
| speculation about extra dimensions. It would get interesting if
| they have predictions that can be checked.
|
| A promising new theory should fit known observations, explain
| previously unexplained phenomenon, and predict something
| testable. That will be difficult to judge as a layperson.
| the__alchemist wrote:
| > Gravity, the thinking goes, can escape our brane and extend
| into the bulk. That explains why it's so weak. All the other
| forces must play in only three spatial dimensions, while gravity
| can extend itself out to four, spreading itself much too thin in
| the process.
|
| Wouldn't this cause gravitational force to fall off with distance
| using something other than an inverse-square law? I think this
| explanation would be a better fit for the weak force than gravity
| for this reason. Thoughts?
|
| More broadly: inverse-square behavior (Gravity, EM etc) strikes
| me as an intrinsic property of 3D geometry; more so of a tell of
| dimensionality than the magnitude of the force. (I believe the
| article is inferring higher dimensionality from relative
| magnitude, vice distance falloff)
| ktrask wrote:
| Yes, exactly. That is why we think the extra dimensions might
| be small, und the inverse square law is only violated at and
| below the size of the extra dimensions. This is also why we are
| using the Yukawa Potential to constrain that possibility,
| because it has a length scale and a strength of a potential
| deviation from the inverse square law. See also:
| https://en.wikipedia.org/wiki/Fifth_force
| mnky9800n wrote:
| Why does the extra dimension need to be small?
| addaon wrote:
| Because gravity will be observed to decay with distance
| cubed for distances on the scale of the extra dimension,
| and distance squared beyond that; and we have not found a
| scale where we see gravity decay faster than distance
| squared (but it gets harder and harder to measure at small
| scale, so the error bars grow).
| ben_w wrote:
| If it was big, you could see it.
|
| IIRC experimental gravity data rules out any compactified
| dimension bigger than 50mm, but a question I keep coming
| back to is "surely the pictures of atomic bonds taken by
| electron microscopes rules compactified dimensions larger
| than 1A?"
| cmrx64 wrote:
| interesting question. my (somewhat naive) thought about
| it is that bonds are maintained by the EM force, which is
| so strong that it swamps out any contribution from
| gravity.
| moralestapia wrote:
| Not necessarily, 2D cannot easily see 3D, etc...
| baxtr wrote:
| How can a dimension be smaller compared to other dimensions?
| codethief wrote:
| It could be a compact[0] dimension, i. e. of finite length.
| In the simplest case you might imagine it as a circle
| attached to every point in our 3-dimensional Euclidean
| space. The aforementioned length scale would be the
| circumference of that circle.
|
| [0]: https://en.m.wikipedia.org/wiki/Compact_space
| taneq wrote:
| Trying to wrap my head around this explanation and I'm
| picturing a looping gif. You have your normal x and y
| dimensions and then time through the gif. If the loop
| length is very short then distance between any two pixels
| will mostly only depend on x and y. Is that right?
| 317070 wrote:
| Yes, that sounds right.
| codethief wrote:
| In the simplest case, yes. Though, once curvature
| (gravity) enters the picture, it could (in theory) become
| more complicated, as the additional dimension could get
| stretched or compressed.
| jiggawatts wrote:
| The classic example is a garden hose seen from afar looks
| like a line, but up close it is a cylinder that can be
| walked "around" by an ant.
| moralestapia wrote:
| And yet that circle has as many "points" as any other
| 1-dim independent axis, so ...
| mariusor wrote:
| I wonder if a higher dimension could also be the explanation
| for extra mass in the universe instead of dark matter. It's
| outside our perceptible space, but it still exists as mass,
| poking through into black holes or gently resting on the skin
| of our 3d volume.
| PaulHoule wrote:
| The weird thing about it though is that whatever the dark
| matter is it has to be spread out. It couldn't be little
| planets or brown dwarfs or burned out stars (in a hidden
| dimension or not) because we'd see more gravitational lensing
| events than we do
|
| https://en.wikipedia.org/wiki/MACHO_Project
| the__alchemist wrote:
| After digging a bit into astromy, computationally myself...
| There are some heavy assumptions used in the functions that
| maps pixels to mass densities. Outsider's 2c, but I assess
| a misalignment between CDM confidence in papers, and this
| mapping.
| geysersam wrote:
| Interesting. It would be extraordinary if many of the
| discrepancies dark matter is required to explain are
| actually caused by some flaw in the data analysis. It
| seems unlikely, but not impossible.
|
| I'm not familiar with the topic. Did you have any
| particularly suspect assumptions in mind?
| whatever1 wrote:
| Far from expert in the field, but assuming that gravity is acts
| in a 3+ND and we observe it in our 3D world, shouldn't we observe
| weird peculiarities with it rather that just its amplitude?
|
| Think that you live on a line, and you see projections of a 2d
| object doing circles on top of you. You would see the shade
| moving and changing sizes in a non-explainable manner to you.
| mystified5016 wrote:
| We do observe really weird gravitational effects. Dark matter,
| for instance. Under Newtonian and Einsteinian physics, galaxies
| shouldn't be able to form in the way we observe. The way
| galaxies and their contents move makes no sense with our
| present understanding of gravity-- unless we assume there's a
| lot more mass. So we invented dark matter as a sort of
| placeholder variable to make the math make sense.
|
| More anomalies: simply being _near_ a large gravitational field
| alters the flow of time. Frame dragging around black holes
| (spacetime itself twists into a rotating spiral). The final
| parsec problem (co-orbiting black holes bleeding energy as
| gravitational waves). And don 't forget the gravitational
| singularity of a black hole.
|
| But perhaps the most important thing to know is that we've only
| just gained the ability to examine gravitational waves. Once we
| build more detectors (especially LISA), we'll probably discover
| a _lot_ more is wrong with our understanding of gravity.
| nathan_compton wrote:
| > More anomalies: simply being near a large gravitational
| field alters the flow of time. Frame dragging around black
| holes (spacetime itself twists into a rotating spiral). The
| final parsec problem (co-orbiting black holes bleeding energy
| as gravitational waves). And don't forget the gravitational
| singularity of a black hole.
|
| These are not really anomalies per se - they are predicted by
| the relatively well tested theory of GR and (except for the
| singularity part) also experimentally observable. They are
| weird from our point of view, but not weird to contemporary
| physics.
| mrkstu wrote:
| From recent discussion though it seems as though the time
| dilation effects or that time itself moves differently in
| different patches of spacetime- that could remove the need
| altogether for dark energy/dark matter:
|
| https://www.theguardian.com/science/2024/mar/09/controversi
| a...
| khazhoux wrote:
| > The way galaxies and their contents move makes no sense
| with our present understanding of gravity-- unless we assume
| there's a lot more mass
|
| Explain for a layman? I don't know what it means for movement
| to not make sense.
| rini17 wrote:
| Being able to precisely calculate movement of planets in
| Solar system and also calculate their mass was a huge
| triumph of physics. The problem is the same math doesn't
| work with visible stars orbiting in galaxies nor galaxy
| clusters. Simplest explanation is there's much invisible
| mass - dark matter. Or the laws are different at these
| scales.
| tekla wrote:
| We know that in a vacuum everything falls that ~9.8m/s
| acceleration on earth.
|
| We get a ball made up of something, and for some reason
| only it accelerates at 10m/s for no discernible reason.
| idiotsecant wrote:
| The more distance along your 4th dimension you allow, the more
| strange geometric effects you will observe. If you let a 4th
| dimension be very, very, very small (imagine a 2d universe that
| actually has a third dimension, it's just subatomic in scale)
| the geometric effects are negligible.A 3d volume can exist in
| that 2d + 1 tiny dimension, in the technical sense, but not in
| any macroscopic sense. Your 3rd dimension curls around to where
| it started nearly immediately.
| Ygg2 wrote:
| > The force of gravity is weak. And not just a little bit weak.
| It's so much weaker than the other three fundamental forces--
| electromagnetism and the strong and weak nuclear forces--that
| it's almost impossible to provide analogies.
|
| Nothing in nature prevents gravity from just being super weak.
| Some forces could just be super weak.
|
| The unspoken premise of gravity being weaker than other forces is
| that all forces were unified at some point. So iff you assume all
| forces in nature were once one force, then gravity being weak is
| an anomaly.
| deadbabe wrote:
| If you could orient something along a higher dimension in the
| correct way could we conceivably create some kind of anti gravity
| or artificial gravity?
| pk-protect-ai wrote:
| God, so many words to cover only one phrase with a "possible
| hint" at an extra mass coming from imaginary source ...
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