[HN Gopher] Electromagnetism is a property of spacetime itself, ...
___________________________________________________________________
Electromagnetism is a property of spacetime itself, study finds
Author : egfx
Score : 246 points
Date : 2021-07-24 17:47 UTC (5 hours ago)
(HTM) web link (sciencex.com)
(TXT) w3m dump (sciencex.com)
| gus_massa wrote:
| In particles physics, they have a different explanation of
| electromagnetism that is also very natural, almost inevitable.
| https://en.wikipedia.org/wiki/Quantum_electrodynamics#Mathem...
| The explanation in particle physics is compatible with Quantum
| Mechanics and Special Relativity, but no one is sure about how to
| extend it to General Relativity. I'm not sure how compatible is
| it with the proposal in the article discussed here.
|
| Non technical version (ELI25):
|
| In quantum mechanics the wavefunction Ps is has complex values.
| If you multiply everything in the universe by -1, nothing changes
| because all the physical results use PsPs* (where * is the
| complex conjugation). You can also multiply everything by i or
| -i. Moreover by any other complex number of modulo 1 because
| PsPs* does not change. (The technical term for this is U(1)
| global gauge symmetry.)
|
| But you can be more ambitious and want to multiply each point of
| the universe by a different complex number of modulo 1. PsPs*
| does not change but the derivatives of Ps change and they are
| also important. (When you use the same complex number everywhere,
| the derivatives is just a multiple of the original derivative.
| When you use a different number in each point, it changes.)
|
| The only way to fix the problem with the derivative is to add a
| new field A. When you and multiply each point of the universe by
| a different complex number of modulo 1, then A changes in a
| simple to calculate but not obvious way. The change in A fix the
| problem with the derivatives of Ps.
|
| So now the equations of the universe with Ps and A don't change
| when you make this change. (The technical term for this is U(1)
| local gauge symmetry.) When you write carefully how a universe
| like this look like, the new field A is electromagnetism.
| (Actually, you can get the electric field and magnetic field
| using the derivatives of A.)
|
| This explanation looks more complicated than the explanation of
| the article, but the article is full of technical terms that you
| really don't want to know, like:
|
| > _Riemann curvature tensor is more than just Ricci curvature--
| electromagnetic fields stretch and bend the spacetime_
| ChuckMcM wrote:
| Based on my reading, the particle physics explanation/theory is
| precisely the current consensus. And, given my research into
| electrodynamics in order to understand the propagation of EM
| wave fronts in antenna design, I also think the article has
| some merit (which is, at its core, a call for some
| experiments).
|
| Given that "light" is fundamentally a electromagnetic wave and
| its propagation in spacetime is constant, and this results in
| _time slowing down_ when you go faster to maintain this
| property, it isn 't unreasonable to hypothesize a more
| fundamental basis here.
|
| Personally, I think adding in the time component will be
| essential to completing this puzzle but all in all it makes for
| an avenue of investigation which is interesting.
| Enginerrrd wrote:
| >Personally, I think adding in the time component will be
| essential to completing this puzzle but all in all it makes
| for an avenue of investigation which is interesting.
|
| Not a physicist, but I've often wondered if the basis of QFT
| got off on the wrong foot by making time a privileged
| coordinate instead of a quantum operator like it does for
| position.
| codethief wrote:
| While I sympathize with your unease about making time a
| privileged coordinate, even in conventional quantum
| mechanics an operator for time seems difficult. What would
| that operator measure? The time at which a given object
| "is"? The whole point of physics is to describe the dynamic
| nature of reality, _parametrized_ by time.
|
| Speaking of which, time(-of-arrival) measurements in
| quantum mechanics have recently attracted quite some
| interest: The classic Copenhagen formalism doesn't seem to
| give an answer here (or at least not a unique one - it
| depends on how you perform the calculation). Meanwhile,
| Bohmian mechanics _does_ seem to make a precise prediction.
| It will be interesting to see what experiments will yield.
| goldenkey wrote:
| You just get into a twist of not being able to renormalize
| if you create a dependency chain like that. The same reason
| quantum gravity is such a problem - gravitons emit
| gravitons..
| eigenket wrote:
| Note that light isn't particularly special in this context,
| what is special (very special) is the speed of light. Other
| things travel at the speed of light, indeed everything
| massless is forced to travel at the speed of light. Other
| things that travel at the speed of light include
| gravitational waves and gluons*.
|
| Basically "the speed of light" should be called "the speed of
| massless things" or possibly "the speed of causality" or
| something. We just call it "the speed of light" because light
| is the first thing we discovered that travels at this special
| speed.
|
| *the star is because everything about quantum-chromodynamics
| is terrible so gluons don't really ever exist as particles
| themselves. If they did they would travel at the speed of
| light.
| rolleiflex wrote:
| I've found that this way of phrasing it helps people click:
| Speed of light is infinite*. What we call speed of light is
| the speed of reality.
|
| * not actually infinite, because reality itself propagates
| at a finite speed
|
| (I'd love to know if this is wrong - this is my best
| attempt to make sense of it from college classes)
| codethief wrote:
| If I understand you correctly, you claim that electromagnetism
| follows immediately from quantum mechanics because Born's rule
| exhibits a U(1) symmetry? That doesn't seem right to me.
| gus_massa wrote:
| It's not only the Born's rule. All the equations have a
| similar symmetry. (You may have [?]Ps=VPs, or
| Ps[?]Ps*+[?]PsPs*+PsPs*. See the real examples in the link in
| Wikipedia. But you never have something like PsPs+Ps*Ps* that
| mix the number of times that the linear and the conjugate
| version appears.)
|
| Also, it's not so immediate, because you must be stubborn
| enough to think that a global obvious symmetry "must" be
| extended to a local symmetry. And in any case, it took like
| 40 years a few brilliant persons to discover it.
| hilbert42 wrote:
| _" I'm not sure how compatible is it with the proposal in the
| article discussed here."_
|
| Right. It seems to me that both approaches make sense. Perhaps
| with some cleaver yet-to-be-determined math both ideas can
| finally be mated.
|
| I've never been convinced that the aether doesn't exist. Sure,
| it's been long debunked in the luminiferous aether sense but as
| the article points out _"...the aether hypothesis was
| abandoned, and to this day, the classical theory of
| electromagnetism does not provide us with a clear answer to the
| question in which medium electric and magnetic fields propagate
| in vacuum. "_ It is this aspect of the abolition of the aether
| that has always worried me.
|
| For starters, any new model of the aether would have to exhibit
| Lorentz-invariant properties. Then there's the matter of vacuum
| permittivity _e0_ and and vacuum permeability _m0_ to consider
| as the speed of light /aka 'electromagnetism' is directly
| linked to these physical constants via the expression _c = 1
| /(m0 e0)^0.5._ If one constant were to change then so too would
| the others including _a_ Sommerfeld 's fine structure constant,
| _RK_ the von Klitzing constant, and _Z0_ the vacuum (free
| space) impedance), etc. (Anyway, one would expect them to
| change--not that we 'd ever know as we'd likely not exist if
| they did). ;-)
|
| But I digress a little. We know that _e0_ and _m0_ have actual
| non-zero values and cannot be equated out (as we sort of tried
| to do in the days when we expressed electromagnetism in cgs
| units). In essence, physical constants _e0_ and _m0_ are
| absolutely intrinsic to electromagnetism, and whilst I cannot
| prove the fact, it seems to me they would be just as intrinsic
| to any new definition of the aether. Moreover, similar
| reasoning makes me think that QFT, ZPE /Zero-point
| energy/quantum vacuum state, _e0_ and _m0_ are all inextricably
| linked to GR. It seems to me matters such as whether the
| spacetime manifold is Ricci-flat, etc. are extremely important
| principally from the perspective that when properly dovetailed
| into theory they 'll provide proof thereof (I'm not saying
| they're secondary aspects of the physics, only that they're
| secondary to the proposition).
|
| It seems to me that an equally important question to ask is why
| the constants _e0_ and _m0_ have the values they do given the
| quantum vacuum state. Of course, the same logic applies to both
| _a_ and _c_. Finally, we base just about everything on _c_ it
| being the fundamental immutable constant. The question is it in
| fact so, or is it that underlying physics first determines _e0_
| and _m0_ and thus these constants could be considered more
| fundamental to any new formulation of the aether than that of
| _c_ , it being the consequential resultant of the properties of
| those constants. (Heresy I know, but it would seem to make
| sense to view _c_ in this context if or when we end up with new
| definition for the aether.)
| infogulch wrote:
| So A/electromagnetism is a natural consequence of the universe
| having a free (complex modulo 1) parameter/field in addition to
| just the wavefunction Ps. ?
| KirillPanov wrote:
| >_In particles physics ... very natural
|
| Er, I'm not sure that things like dressed particles [1] and
| off-shell matter [2] violating E=mc^2 [3] could be described as
| even remotely "natural".
|
| Perhaps they are _valid_ theories, but "natural" certainly
| isn't an appropriate description of most of what unavoidably
| follows from particle assumptions.
|
| [1] https://en.m.wikipedia.org/wiki/Dressed_particle
|
| [2] https://en.m.wikipedia.org/wiki/On_shell_and_off_shell
|
| [3] https://en.m.wikipedia.org/wiki/Virtual_particle#Properties
| eigenket wrote:
| Virtual particles are basically just a mathematical trick to
| make doing calculations easier in perturbative quantum field
| theory. You shouldn't take them too seriously.
|
| If you do the calculations in another way (e.g. by
| discretizing stuff on a lattice) no virtual particles appear
| but your calculations become a lot harder.
| goldenkey wrote:
| They are still a trick because they are used to propagate a
| particle exactly where it needs to go in order to exert the
| force of the field. So the field is everywhere, but is
| pretty much invisible except for when virtual particles
| mediate it.. No efficient simulation on a computer could
| operate in such a manner. It's explanatory but not a
| constructive proof. I can't build an efficient simulation
| of our universe based on the virtual particle paradigm.
| namanyayg wrote:
| Thanks for the explanation. If you have the time, can you also
| explain _why_ would we be multiplying "each point of the
| universe with a different complex number of modulo 1?" What
| does it mean in physical reality; why multiply points with any
| number at all?
| ufo_pilot wrote:
| Not GP, or a physicist, but my understanding is that the
| different number at each point you multiply with represents a
| degree of freedom at each point of spacetime, and in this
| degree of freedom is where the electromagnetic field lives.
| tagrun wrote:
| To find out what kind of symmetry a field (as described by a
| Lagrangian) admits. It's called gauge symmetry:
| https://en.wikipedia.org/wiki/Gauge_theory
|
| It's a complex number for QED but in general, it's a unitary
| matrix: a rotation which preserves the magnitude of a
| wavefunction (a complex vector).
|
| In physics, symmetries play a fundamental role.
| cshimmin wrote:
| The simple answer is "because we can". In general, physicists
| have found that we should write down the most general
| mathematical theory compatible with what's observed. A famous
| example of this is Einstein's cosmological constant -- I'll
| leave that one to wikipedia [1] since I'm a particle
| physicist and not an expert on GR.
|
| In the case of gauge theory, the idea that we should consider
| the most general case has been well proven. As GP pointed
| out, all observable phenomena ultimately depend only on the
| absolute modulus of the field Ps, so a theoretical physicist
| naturally wonders, what happens if you allow its complex
| phase to vary. Turns out nothing interesting happens if you
| apply a global phase, but if you allow the phase to vary at
| every point in spacetime, it ends up breaking the theory.
| That is, unless you include an additional field at every
| point in spacetime that precisely cancels out the change
| induced by the gauge freedom.
|
| In other words, the motivation is that we can't simply look
| and "see" whether or not there is a locally varying phase on
| the wavefunction Ps, since we only can measure |Ps|^2. So we
| have to assume there is, until proven otherwise. Since a
| local phase would imply the existence of an extra field to
| cancel it out, we can indirectly check for this scenario by
| looking for the corresponding field. As pointed out by GP, in
| the case of a U(1) gauge, it turns out there is such a field,
| and electromagnetism (and all of its laws) exactly fit the
| bill.
|
| There are other "unmeasurable" symmetries you could apply to
| the wave function as well, beyond just a complex phase. SU(2)
| is a Lie group symmetry which would mean that the measurable
| properties of certain tuples of fields (Ps, ph) are
| indistinguishable under a sort of complex-valued rotation of
| Ps->ph and ph->Ps. Again, if you assume a such symmetry is
| locally varied at every point in spacetime, you end up
| requiring not one but _three_ new fields to cancel out the
| effects on the SM Lagrangian. It turns out that the vector
| bosons W+, W-, and Z, which mediate weak nuclear forces
| exactly fit the bill.
|
| [1] - https://en.wikipedia.org/wiki/Cosmological_constant
| vehementi wrote:
| > That is, unless you include an additional field at every
| point in spacetime that precisely cancels out the change
| induced by the gauge freedom.
|
| Could you elaborate on this a bit? To a layperson this
| sounds like a hack. "Things get screwy when you screw with
| them, UNLESSSSS we add a magic thing that undoes our work".
| Well yeah.
| blablabla123 wrote:
| A really simple example is voltage. What does it even
| mean if one cable is on a potential of 5 V? It's always
| compared with the Ground voltage since the voltage is
| always a difference between 2 electric potentials. That
| means you could add a constant to each potential and
| nothing would change. So in this case _not gauging_ would
| be quite hacky... (This example has nothing to do with
| the phase though, but just to illustrate. Almost always
| when you measure something, some gauging is at least
| implicitly involved.)
|
| So it turns out this happens quite often that there is
| some kind of constant that can be divided out. In case of
| particle physics a whole framework has been developed out
| of it that has really close relations to Lie group
| theory. (The experimentally confirmed parallels are just
| astonishing with group generators and elements
| corresponding to interaction particles and the normal
| particles.)
| Denvercoder9 wrote:
| It turns out that the magic thing we have to add, exactly
| fits the observations we have of electromagnetism. That's
| an indication that we screw with the theory in the same
| way that nature does, and in the end that's the goal of
| physics: understand the way nature behaves.
| cshimmin wrote:
| It's just a mathematical tool of curiosity that we have
| found very useful.
|
| Here's an analogy: You find a box, and you can't see
| inside it. You have no reason to think there's something
| inside it. But also, boxes have stuff in them sometimes.
| So, you shake the box, and hear something clinking
| around. Therefore, you infer there's something in the
| box.
|
| Somebody next to you says "This sounds like a hack. There
| was a box and you had to go shake it until it started
| making sounds that it wasn't making before. UNLESSSSS we
| now magically have to agree that there's something in the
| box."
|
| It's a perfectly reasonable question, and I'm just
| turning your words on you in good faith :)
|
| To take the technical discussion a bit further, it's
| exactly this kind of reasoning that led to the discovery
| of the Higgs boson. Strictly speaking, it's impossible
| for gauge bosons (that's what the particles are called
| that show up when you add these locally-varying
| symmetries) to have nonzero mass. The photon and gluons
| (from the SU(3) strong force) are massless, but the W and
| Z bosons are VERY massive. This was a big problem with
| the Standard Model; the vector gauge bosons had every
| property expected from the gauge theory, except for this
| one point about their mass, which was experimentally
| incontrovertible.
|
| That is, until Brout/Englert/Higgs came along. They said
| "Yeah the vector bosons must be massless UNLESSSSSSSS you
| assume there's this magic additional field that couples
| to every particle's mass, in which case it perfectly
| cancels out all the problems and allows the W and Z
| bosons to be heavy". It took 50 years but we found that
| particle eventually.
| gfodor wrote:
| You're a really great writer on this topic. If you're not
| already, and you have the time, you should seek out ways
| to do this in a way that has more reach. Thank you!
| cshimmin wrote:
| And at the risk of muddying the original point, it turns
| out that strictly speaking the neither the neutral Z boson
| nor the electromagnetic photon can be said to come from
| SU(2) or U(1). Instead, each field is a linear combination
| of some abstract fields (namely the neutral W0 and the weak
| hypercharge B bosons) from the unitary gauge induced by the
| compound symmetry SU(2)xU(1). This is because when both
| symmetries SU(2) and U(1) are present, there are different
| ways you can "mix" the two into the Lagrangian. The mixing
| that gives us the photon and the Z0 boson is known because
| of the experimental confirmation of these particles. This
| is what is meant when it is said that electromagnetism and
| weak neuclear forces are united in a higher-energy theory
| as a single "electroweak" force.
| jasonwatkinspdx wrote:
| Thanks for these comments. This simplified a whole bunch
| of things I had questions about.
| trenchgun wrote:
| Thank you!
| cominous wrote:
| Wow you blew my mind. You need to consider creating YouTube
| videos about this.
| nextaccountic wrote:
| I don't know about quantum mechanics, but when we talk about
| space we should be free to add a quantity to the whole
| universe (like adding 1 to the x coordinate of everything)
| because this just shifts the whole universe, or accordingly,
| shifts the origin - the (0, 0, 0) point - in the opposite
| direction.
|
| The origin is set at an arbitrary point so this "space shift
| invariance" is saying that it doesn't matter what point we
| set for the origin (and mathematically this corresponds to
| the conservation of momentum - see Noether's theorem[0])
|
| Hmm maybe the "zero" for the quantum states is arbitrary, so
| you should be able to add anything to it for the whole
| universe, and this merely changes the zero state in the
| opposite direction.. and since this should be a conversation
| law, pretty sure this is equivalent to the conservation of
| electric charge
|
| https://en.wikipedia.org/wiki/Noether's_theorem
| galaxyLogic wrote:
| I may be starting to get it. The magic numbers we add to
| everything or multiply everything with really represents
| just a change in the viewpoint, origin of the observer. And
| because it should be possible to change the "location" of
| the observer (say the voltage we take to be 0 volts) and
| still get the same theory to hold up, we can discover that
| it can only hold up if we assume the existence of some new
| field. Something like this?
| layoutIfNeeded wrote:
| Yes.
| vecter wrote:
| Is this A you speak of the electromagnetic vector potential?
| bifftastic wrote:
| I'm not the person you're replying to, but yes A definitely
| is the electromagnetic vector potential (from classical
| electrodynamics). In gauge theory A tells you how to relate
| the phase of Ps at nearby points in space/time.
|
| Now that may purely a choice of convention for Ps at
| different points in space/time (a choice of "gauge" in the
| jargon), but where it gets interesting is if your successive
| nearby points in space/time trace out a closed loop. If your
| A is such that the phase of Ps ends up different as a result
| of going round the loop, you have an electromagnetic field!
| ufo_pilot wrote:
| The more correct technical term is "electromagnetic four
| potential", or "four vector".
|
| A is quantum, the electromagnetic potential is classical, so
| they are not really the same thing.
| dataflow wrote:
| Related question: is it settled which one is "real"? A or B?
|
| https://en.wikipedia.org/wiki/Aharonov%E2%80%93Bohm_effect#P.
| ..
| nixpulvis wrote:
| Both?
| dataflow wrote:
| Well I'm glad that's settled!
| cshimmin wrote:
| Actually since it's a spacetime potential, it's a 4-vector
| valued. So it's related to both the (three-)vector potential
| A and the scalar potential V.
| kilodeca wrote:
| I heard people saying the opposite.
| lend000 wrote:
| I like the idea intuitively (the idea that infinite discrete
| photons are required to mediate continuous fields from a single
| electron over infinite distances never sat well with me), so are
| they claiming here that there is a relativity-version of
| Maxwell's Equations? Does it require an additional spatial
| dimension to account for charge, or does it operate it on the
| same spacetime as gravity? Regardless, if I'm understanding this
| nontechnical overview correctly, it's a large claim requiring a
| lot of work. Probably worth a Nobel Prize if it they actually
| pull it off.
| immmmmm wrote:
| just read the abstract, seems meh
|
| wrote two very well cited articles [1,2] on this in the context
| of string theory. but this was just extending kaluza klein, where
| by adding one compact dimensions (with some assumptions) you get
| maxwell out of einstein for free. this result is from 1919, 102
| years old.
|
| i'm glad i can write all gravitation, electromagnetism, yang
| mills and string theory in two equations (1.6 in [2]]) but
| honestly i don't that's a breakthrough.
|
| i might be wrong, yet it smells more like PR than important
| discovery.
|
| btw you can as as well find solutions of GR that are dual to
| navier stokes equs.
|
| [0] https://en.m.wikipedia.org/wiki/Kaluza-Klein_theory
|
| [1] https://arxiv.org/abs/1109.4280
|
| [2] https://arxiv.org/abs/1304.1472
| calin2k wrote:
| this reminds me of
| https://en.wikipedia.org/wiki/Philadelphia_Experiment
| marsven_422 wrote:
| I long for the day they invalidate QM
| orbifold wrote:
| This paper is seriously flawed. I'm surprised it was published.
| curt15 wrote:
| I come from maths, not physics, but their construction
|
| g_{\mu \nu} = A_\mu A_\nu
|
| looks a little weird to me. The left side is a tensor, but isn't
| the electromagnetic four-potential is a gauge field, not a
| tensor?
| al2o3cr wrote:
| For one, it's going to produce a metric where all the diagonal
| elements are positive (or zero) - different from the -+++ or
| +--- signature of "normal" spacetime.
|
| The paper's calculation reminds me of Kaluza-Klein theory,
| which uses a similar construction as part of extending the
| metric from four dimensions to five:
|
| https://en.wikipedia.org/wiki/Kaluza-Klein_theory
| ozankabak wrote:
| I was thinking about the signature issue as well. In flat
| space (i.e. Minkowski metric), this would imply a constant
| four-potential with an imaginary 0'th component, which I can
| not make sense of.
| ajkjk wrote:
| A gauge field is tensor-valued; what's wrong with that?
|
| Although it does seems strange for other reasons. Primarily
| because it seems very unlikely that everyone else who developed
| this field wouldn't have considered the possibility and then
| discarded it.
| curt15 wrote:
| Although a gauge field has multiple components, it transforms
| differently from tensors under a change of coordinates:
|
| A -> O A O^{-1} - dO O^{-1} (O is the Jacobian matrix)
|
| The second term is absent for tensors (such as the left side
| of their equation 4). It also vanishes on a flat spacetime
| where one only considers linear (Lorentz) coordinate
| transformations, but based on my cursory reading they don't
| seem to be making that assumption.
| codethief wrote:
| I'm not sure I'm following. In General Relativity, the
| 4-electromagnetic potential A^m is simply a vector field on
| spacetime, so what's wrong with taking the (symmetrization
| of) the tensor product of A_m with itself to obtain a
| symmetric 2-tensor? (Whether or not that 2-tensor satisfies
| the requirements for a semi-Riemannian metric is another
| question.)
| nilaykumar wrote:
| Why is A_\mu a vector field on spacetime? In the standard
| treatment A is the (pullback to the base of the)
| connection 1-form of a connection on a principal
| U(1)-bundle on spacetime. Technically it's valued in the
| Lie algebra of U(1), but as that can be identified with i
| times the real numbers, we can ignore that here. Does the
| product A_\mu A_\nu happen to transform tensorially?
| Because as the parent pointed out, the transformation
| rule for A involves an extra term, so it's not obvious.
| dr_dshiv wrote:
| "John Wheeler, the famous physicist, put forward the idea that
| all of the material world is constructed from the geometry of the
| spacetime. Our research strongly supports this kind of natural
| philosophy. It means that the material world always corresponds
| to some geometric structures of spacetime."
|
| This is also the Platonic-Pythagorean perspective, that the world
| is literally made of math.
| ajkjk wrote:
| This article is not really coherent. It seems like a bunch of
| random statements about physics, strung together without
| explanation. This paragraph for instance is a bunch of true-ish
| sentences but overall is gibberish:
|
| > The metric tensor of spacetime tells us how lengths determine
| in spacetime. The metric tensor also thus determines the
| curvature properties of spacetime. Curvature is what we feel as
| "force." In addition, energy and curvature relate to each other
| through the Einstein field equations. Test particles follow what
| are called geodesics--the shortest paths in the spacetime.
| LegitShady wrote:
| There's a paper with equations linked at the bottom. I suspect
| it sounds like gibberish because its describing a mathematical
| proof with common language. The paper assumes you have a lot of
| knowledge as well.
| an-allen wrote:
| "metric tensor of spacetime"... When I hear a series of words
| that I feel sound like bullshit I Google them. And, like you I
| felt this paragraph felt like a healthy bit of BS but was
| surprised that this paragraph is pretty much the Wiki
| definition of the phrase "metric tensor of spacetime". I still
| dont understand it however.
|
| https://en.m.wikipedia.org/wiki/Metric_tensor_(general_relat...
| codethief wrote:
| > This paragraph for instance is a bunch of true-ish sentences
| but overall is gibberish:
|
| >> The metric tensor of spacetime tells us how lengths
| determine in spacetime. The metric tensor also thus determines
| the curvature properties of spacetime. Curvature is what we
| feel as "force." In addition, energy and curvature relate to
| each other through the Einstein field equations. Test particles
| follow what are called geodesics--the shortest paths in the
| spacetime.
|
| Could you elaborate on why you think this is gibberish? I mean,
| I agree that the article is giving off a pseudo science vibe
| and the authors should work on their style. (Instead of
| presenting their results in a matter-of-fact manner, they
| should rather dedicate more time to explaining their
| assumptions and their reasoning in a step-by-step manner.) But
| the paragraph you quoted seems perfectly fine.
| ethn wrote:
| I thought we knew this already since Faraday.
| evancox100 wrote:
| I'm nowhere near qualified enough in general relativity to
| evaluate their claims, but when I see something like this:
|
| "This is aesthetically pleasing, as nature seems to strive for
| harmony, efficiency and simplicity."
|
| it makes me think they are not being the most objective
| evaluators of reality.
| wwweston wrote:
| Since we're part of reality and products of reality, we are
| most definitely not independently objective.
|
| On the other hand, some our aesthetics could be founded in an
| adaptive sense for reality.
| dr_dshiv wrote:
| The entire universe is like a free-energy minimization machine.
| Everything is astonishingly optimized.
| KhoomeiK wrote:
| Aesthetics, harmony, and simplicity are the guiding principles
| of mathematical conjecture. This piece is simply hypothesizing
| about a link while calling for further empirical research.
| haskellandchill wrote:
| No, that's just fluff. Occam's Razor is all there is to it.
| catlifeonmars wrote:
| Occam's razor more or less manifests as elegance in
| mathematics.
| enkid wrote:
| Aesthetics should have nothing to do with science. Aesthetics
| is the reason we thought the Earth was at the center of the
| universe and everything outside the orbit of the moon was made
| of perfect spheres. It's why the Soviet Union pushed Lamarckian
| biology instead of Darwinism.
| bullsbarry wrote:
| The earth is at the center of the _visible_ universe.
| mellosouls wrote:
| Only to observers on earth...
| riffraff wrote:
| Also in the Tycho Brahe system Earth is at the center of
| the solar system but it is equivalent to the Copernican
| one, you can just change the coordinates.
|
| https://en.m.wikipedia.org/wiki/Tychonic_system
| enkid wrote:
| And that was a complete mess if a system when you start
| considering moons orbiting around planets orbiting around
| the sun orbiting around the Earth. Not to mention
| anything outside our solar system.
| enkid wrote:
| I don't know what point you are making. That's how
| observation works... The observer is always at the center
| of their own universe.
| golemotron wrote:
| > Aesthetics is the reason we thought the Earth was at the
| center of the universe
|
| Nope, that was hubris.
| kilpikaarna wrote:
| To scholastic thinking it was the heliocentric view that
| was hubris, since it didn't place the Earth at the lowest
| level of creation where it belonged.
| golemotron wrote:
| That makes sense. Hubris is always what the other person
| does.
| enkid wrote:
| Hubris that what humans consider aesthetic is somehow
| important to the Universe.
| March_f6 wrote:
| There are copious amounts of examples showing how Nature is
| attracted to symmetry(a form of beauty). Why wouldn't we use
| this is evidence as a heuristic?
| enkid wrote:
| You just gave a non-aesthetic reason to explore symmetry.
| I'm not saying we should only look at theories that are not
| beautiful, but instead we should not use that to evaluate
| if a theory is worth exploring.
| lalalandland wrote:
| It's a big issue for several fields of science. Sabine
| Hossenfelder Lost in Math: How Beauty Leads Physics Astray
|
| https://aeon.co/ideas/beauty-is-truth-truth-is-beauty-and-
| ot...
| CyberRabbi wrote:
| > it makes me think they are not being the most objective
| evaluators of reality.
|
| Generally in physics and in maths researchers tend to spend
| time evaluating solutions that are symmetrical or otherwise
| elegant. I suppose that does make us biased but we're searching
| for answers in a very large space of possible answers. Beaming
| towards elegant solutions seems like a reasonable heuristic.
| jgrowl wrote:
| Relevant: https://www.pbs.org/wgbh/nova/article/beauty-in-
| physics/
| MichaelZuo wrote:
| There seems to be something tantalizing in the relation between
| the EM and gravity field. Whether this is an accurate description
| of that remains be seen.
|
| Some interesting potential tie-ins
| https://en.wikipedia.org/wiki/Abraham-Minkowski_controversy and
| https://en.wikipedia.org/wiki/Casimir_effect
| ozankabak wrote:
| IIUC the authors are saying that if we associate the metric with
| the four-potential via an outer product, they get a picture
| coherent with the current understanding of how electromagnetism
| "works" in GR under certain circumstances.
|
| I can somewhat see how to interpret the mathematics in free
| space. But what about when there are massive bodies in the
| picture? They will result in a non-flat metric... does that imply
| they create their own electromagnetism?
| kmm wrote:
| I'm not an expert in GR, but the linked paper seems
| nonsensical[0]. It postulates a highly degenerate decomposition
| of the metric tensor, for which they postulate a contrived action
| which then seems to correspond to the Einstein-Hilbert, through
| mathematically unsound manipulations (how can you raise indices
| with the metric being nowhere even close to invertible?).
|
| Besides, how can you talk about unifying general relativity and
| electromagnetism without mentioning Kaluza-Klein theory[1]? And
| what about one of the most beautiful principles in physics, gauge
| invariance[2]?
|
| I don't want to be rude, but I'm very curious as to how this got
| through peer review.
|
| 0:
| https://iopscience.iop.org/article/10.1088/1742-6596/1956/1/...
| 1: https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory 2:
| https://en.wikipedia.org/wiki/Gauge_theory
| codethief wrote:
| > Besides, how can you talk about unifying general relativity
| and electromagnetism without mentioning Kaluza-Klein theory[1]?
|
| No offense but the very first paragraph of the article's
| introduction mentions Kaluza's work:
|
| > The earliest attempts can be reasonably traced back to the
| German physicist Gustav Mie (1868-1957) and the Finnish
| physicist Gunnar Nordstrom (1881-1923). Fruitful efforts came,
| for example, from David Hilbert (1862-1943), Hermann Weyl
| (1885-1955), Theodor Kaluza (1885-1954), Arthur Eddington
| (1882-1944) and of course also from Albert Einstein
| (1879-1955). It is less well-known that, for example, Erwin
| Schrodinger (1887-1961) had such inclinations as well, see [1].
| For a thorough historical review, see [2].
| onhn wrote:
| Are you sure it was peer reviewed at all? It looks like a
| conference proceedings.
| kmm wrote:
| According to this https://iopscience.iop.org/article/10.1088/
| 1742-6596/1943/1/... they're all peer-reviewed. An average
| number of reviews per paper of 1 seem a bit curious though.
| lamontcg wrote:
| Yeah first thought that popped into my head was Kaluza-Klein
| theory, and I'm far from an expert enough to dissect the paper
| but it has that smell of junk science.
| goldenkey wrote:
| Kaluza's work is mentioned in the first paragraph of the paper.
| How can you write such an inflammatory critique without having
| actually read the paper?
| kmm wrote:
| Kaluza's name is mentioned, but not Klein's, and there's no
| mention of their theory whatsoever.
|
| Kaluza-Klein theory is the archetype of expressing
| electromagnetism purely through curvature, and I'd expect any
| paper doing the same to refer to it, as well as explain how
| the work in the paper differs from or expands on it.
|
| The fact that the metric proposed in the paper corresponds to
| the term added to the 4D spacetime part of the Kaluza-Klein
| metric is already suspicious. It makes me think they're
| either repeating Kaluza and Klein's work, or aren't properly
| citing it when they should have.
| trhway wrote:
| mass/energy conversion (in particular to/from photons, i.e. EM
| waves) is a kind of huge hint that there is really only energy
| and spacetime (and with energy being just a configuration of
| spacetime we're left with the spacetime only really). The only
| issue is the nature of electric charge - what is it really, i.e.
| can it be reduced to gravity? can it be just an emergent property
| of energy/spacetime? And in particular the repelling property of
| the charge which at first seems to not exist for gravity - then
| where it comes from? I think it is some spin based effect along
| the lines of the [non-charged] black holes spin-spin interaction
| based repelling effect, something like this
| https://arxiv.org/abs/1901.02894
|
| Another commenter https://news.ycombinator.com/item?id=27943428
| talks what basically looks to me as an emergence of EM field from
| rotation - "to multiply each point of the universe by a different
| complex number of modulo 1" - ie. as an artefact emerging by
| changing the frame to the one where the system is rotating (ie.
| gets a spin). Kind of similar how magnetic field is just emergent
| artefact in the frame where charge is linearly moving.
| [deleted]
| enoreyes wrote:
| This is interesting and if the experimental evidence confirms
| this hypothesis, it bodes well for our future. A universe where
| we can interact with spacetime via engineering is one that allows
| for a lot of creative freedom. They also have another interesting
| article claiming that the imaginary structure of QM is the result
| of stochastic optimization on spacetimes:
| https://www.nature.com/articles/s41598-019-56357-3
|
| Maybe the UAPs really are just secret warp drive tech we made 20
| or 30 years ago.
| LinAGKar wrote:
| >On the other hand, the theory of gravitation is rather well
| understood
|
| I thought it was the other way around. Gravity is not well
| understood.
| Sharlin wrote:
| Gravity is extremely well described by general relativity. What
| we do lack is a quantum version of GR, but that does not change
| the fact that we understand gravity very well, at least in the
| sense of the word that physicists are used to.
| codethief wrote:
| > we understand gravity very well, at least _in the sense of
| the word that physicists are used to_
|
| (emphasis mine)
|
| As someone with a background in mathematical relativity, I
| would like to note that GR actually is not very well
| understood at all. Physicists seem to focus on the few simple
| solutions to Einstein's field equations that people have
| found through educated guessing, but there a ton of questions
| about the field equations that are open to this day.
| codethief wrote:
| I had a quick look at their paper. I haven't understood
| everything and looked into all steps in detail but I think what
| they doing is (roughly) the following:
|
| Let g be the spacetime metric, and A be the electromagnetic
| 4-potential.
|
| 1. Suppose you could write the metric as g_{mn} = A_m A_n, i.e.
| the symmetric product of A with itself.
|
| 2. Conclude that the Einstein-Hilbert action is just the
| electromagnetic action _plus_ a correction term A_m [?]^m [?]_n
| A^n = g(A, grad(div A)).
|
| 3. Assume that J^m = [?]^m [?]_n A^n = grad(div A).
|
| 4. The correction term from step 2 then becomes the usual
| electromagnetic coupling A_m J^m. As a consequence, the Einstein-
| Hilbert action for g is just the usual full (non-vacuum) action
| of electrodynamics on a background curved by g = Sym(A[?]A).
|
| 5. Consider the _vacuum_ Einstein equations and, thus, a Ricci-
| flat spacetime. Show that this is equivalent to [?]2 A^m = J^m
| which are the inhomogeneous Maxwell equations in Lorentz gauge.
| The fact that we 're in a vacuum spacetime but still considering
| electromagnetism seems odd but I guess their idea is that if
| electromagnetism is a purely geometric property of spacetime,
| then the electromagnetic action (including any potential electric
| current) shouldn't appear on the right-hand side of Einstein's
| equations in the first place - because the Einstein equations
| _are_ Maxwell 's equations.
|
| 6. Identify the 4-current J^m with terms involving the
| electromagnetic field tensor and the metric's Weyl curvature.
| (Meaning, once again, that J^m can be non-trivial even though
| we're considering a vacuum/Ricci-flat spacetime.)
|
| 7. Identify the remaining (homogeneous) Maxwell equations with
| the first Bianchi identity for the Riemann tensor.
|
| 8. Impose the continuity equation [?]_m J^m = 0, i.e. assume
| conservation of charge.
|
| 9. Conclude from 3) and 8) that div(A) fulfills a homogeneous
| wave equation.
|
| -----
|
| Comments and observations:
|
| - In step 5, I don't see how Maxwell's equations (18) are
| supposed to follow from equation (17). But it's late, maybe I'm
| just being blind.
|
| - As other comments have already pointed out, step 1 seems
| unreasonable because 1) the metric will no longer be of
| Lorentzian type (with determinant -1) but instead will be
| positive-semi-definite. (To see this, diagonalize the metric at a
| given point => g = (A_m)2 (dx^m)2.) In particular, the metric
| might be degenerate. It seems section 2.1 in their paper is
| supposed to address the signature issue but from my POV it's
| insufficient.
|
| - The paper basically claims that gravity is just the theory of a
| vector 4-potential. That doesn't seem right, given that much
| effort was spent in the past 100 years to find such a theory.
| AFAIK it's pretty much ruled out these days.
|
| - Given step 5 and the fact that the EM field no longer seems to
| contribute to the field equations, I have even more doubts this
| theory could ever turn out to be true. There are lots of
| solutions to the Einstein-Maxwell equations and I'm sure some of
| them have been confirmed experimentally by now. (I'm thinking of
| black hole jets etc.)
|
| - For instance, IIRC there's a paper showing that from Einstein-
| Maxwell's equations it follows that photons move along null
| geodesics (which in the beginning of GR was merely an axiom of
| the theory). I wonder what would happen to this result.
| Hypothetically, photons might no longer move along geodesics in
| this new gravito-electromagnetic theory but the theory might
| _still_ reproduce gravitational lensing. I don 't think that's
| very likely, though.
|
| - More generally, I think their theory is even difficult to
| reconcile with classic electrodynamics in the first place. In the
| absence of strong gravitational and quantum effects, we know that
| Maxwell's equations describe ED very well. However, the equations
| [?]2 A^m = J^m above no longer are the classic (linear!1) vacuum
| Maxwell equations we know - they are now highly non-linear since
| the covariant derivative [?] now also involves the vector
| potential A. To reobtain classic ED in flat space one would
| basically need to ensure that in every-day situations A is
| "constant enough" not to produce any significant curvature
| through g = Sym(A[?]A) but still dynamic enough to reproduce the
| classic wavey nature of light. This doesn't seem likely. Plugging
| any known (experimentally proven) solution to the Maxwell
| equations into the equations here should invalidate the theory.
|
| 1) in the absence of charges, i.e. J^m = 0
| [deleted]
| edem wrote:
| Wait, we know this since QED, no?
| fosk wrote:
| I dream of faster than light travel by bending the space time
| fabric in "U" shape (like pinching a piece of paper) and allowing
| to travel across the two planes of reference.
| psyc wrote:
| Ah, fond memories of A Wrinkle in Time by Madeleine L'Engle.
| cletus wrote:
| This common desire for FTL should be an object lesson in how
| wishful thinking distorts objectivity. We see a constant stream
| of ideas that spring from simply not understanding the domain
| of a function. You can put a negative value into mass or
| energy. That doesn't mean it means anything.
|
| There really is no plausible theory for FTL of any kind. Maybe
| there will be in the future. Personally I'd put everything I
| have on the speed of light being an absolute limit to
| causality.
|
| Look at it this way: if FTL travel were possible we probably
| wouldn't exist. Whoever came first would probably colonize the
| Universe and sterilize it of competition. So there's that.
| ineedasername wrote:
| _if FTL travel were possible we probably wouldn 't exist.
| Whoever came first would probably colonize the Universe and
| sterilize it of competition_
|
| FTL doesn't necessarily mean infinite/instant travel. Also
| the scenario you propose could be part of the Great Filter,
| and we just haven't been culled yet. Or FTL civilizations
| tend to get so large they fracture & turn to in-fighting or
| encounter other resource bottlenecks that limit exponential
| expansion.
|
| Or C is the law and going FTL spawns a cosmic traffic cop
| like the meatball head things in Rick & Morty.
|
| Or FTL is simply impossible, but perhaps not _constant_ and
| various factors impact the local C
| freshhawk wrote:
| Sure, it would take an enormous amount of energy to do it
| though.
|
| Oh yeah, and you'd also be annihilated as you were completely
| turned to energy as you tried to go through it of course. But
| you'd sure fire a hell of a lot of randomized high energy
| particles out the other side after the amount of time it would
| have taken light to get there.
|
| Not my preferred kind of "travel", I'll just freeze myself and
| go the slow way or something.
| amelius wrote:
| What if your neighbor wants to bend space time in the other
| direction?
| swayvil wrote:
| Then we would simply fork reality. Everybody's happy.
| excalibur wrote:
| Everybody but the TVA.
| IgorPartola wrote:
| Everybody is both happy and unhappy.
| koheripbal wrote:
| folding the paper isnt enough. you also need to reform the
| paper to make the hole attach at both ends. ripping apart
| spacetime may not even be possible.
| akomtu wrote:
| Here's about the same idea with formulas:
| http://estfound.org/quantum.htm. TL;DR if we assume that the ds2
| invariant oscillates a bit, and apply the lorentz transforms,
| we'll get the stationary Schrodinger equation. I can't judge the
| math or physical soundness of the approach, but it looks legit.
| drran wrote:
| EM is math. LOL.
| zeteo wrote:
| The idea that strong electromagnetic fields affect the local
| curvature of spacetime is nothing short of revolutionary. Imagine
| the possibilities of that! This may be the beginning of the road
| to a functional warp drive at last.
| nimish wrote:
| Well good news, we've known that for a century as it follows
| from incorporating the electromagnetic stress energy tensor
| into the field equations
| zeteo wrote:
| I can do without the sarcasm. Can you point me to any actual
| experiments?
| amelius wrote:
| What would the EM field of a photon look like if you moved along
| with the photon? Would the magnetic part disappear just like it
| disappears when you move along with a moving electron?
| gary_0 wrote:
| You can't "move along with a photon" because, in terms of
| General Relativity, any particle moving at c doesn't have a
| frame of reference.
| [deleted]
| blamestross wrote:
| Basically, from the photon's point of view, all travel is the
| universe distorting until origin and destination are literally
| the same point. Photon's don't experience movement, the
| universe does an instant jig around them while they sit still.
| avmich wrote:
| > Moreover, electric charge relates to some compressibility
| properties of spacetime.
|
| Wonder if somebody could explain this?
| swayvil wrote:
| Maybe we could take the same motion in air as a metaphor for
| what's happening in spacetime.
|
| Charge becomes an area of higher or lower air-density.
|
| EM Waves become areas of changed air-density, propagated.
|
| This is just pulled fresh from my butt, mind you.
| findalex wrote:
| Maybe something along the lines of regions of charged space
| time resist compression while charged and non charged regions
| more spontaneous compress? Attraction/repulsion?
| zwaps wrote:
| It's really interesting to see other fields trying to explain
| research.
|
| Here, I feel the authors are not entirely clear who the audience
| is supposed to be. At first, they seem to target people who need
| the difference between Einstein and Maxwell explained. The
| section is titled:" Maxwell's equations and general relativity--
| what are these all about?"
|
| Then when they reveal the missing link, the uninformed reader is
| presented with a logical progression that is obviously written
| towards somehow for whom the statement:"the Lagrangian of
| electrodynamics is just the Einstein-Hilbert action" is self
| explanatory. You know, people who say, yes of course, if you
| say:" keep the spacetime manifold Ricci-flat."
|
| Writing about science is hard
| zwaps wrote:
| And all I, the non technical reader, want to know is which of
| these theories give us Warp technology by the time the Vulcans
| pass by the solar system
| lumost wrote:
| Reading the article, this appears to be a speculative rehash of
| past theories claiming to unify electromagnetism and general
| relativity. The article ends on the note that empirical research
| is needed.
|
| I did not see anything novel that would warrant further attention
| - did I miss something?
| yummypaint wrote:
| Electromagnetism is already understood to be a special case of
| the electroweak interaction, which is itself a component of the
| standard model. The paper mentions Maxwell's equations, but not
| these more general models.
| codethief wrote:
| So what? The very first step to unifying GR with quantum
| mechanics and the standard model might actually be to realize
| that _part_ of the standard model can be embedded in GR (at
| least when EM is considered as a classical field theory). I don
| 't think it's a deficiency of the paper that it doesn't present
| a solution to everything.
| avsteele wrote:
| No opinion on this paper but I'll note something related of
| interest:
|
| You can see how _special_ relativity is true by just taking
| Maxwell 's equations seriously. They show the speed of light is
| the same in every reference frame.
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