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Space Science

The Paradoxes That Threaten To Tear Modern Cosmology Apart 231

KentuckyFC writes Revolutions in science often come from the study of seemingly unresolvable paradoxes. So an interesting exercise is to list the paradoxes associated with current ideas in science. One cosmologist has done just that by exploring the paradoxes associated with well-established ideas and observations about the structure and origin of the universe. Perhaps the most dramatic of these paradoxes comes from the idea that the universe must be expanding. What's curious about this expansion is that space, and the vacuum associated with it, must somehow be created in this process. And yet nobody knows how this can occur. What's more, there is an energy associated with any given volume of the universe. If that volume increases, the inescapable conclusion is that the energy must increase as well. So much for conservation of energy. And even the amount of energy associated with the vacuum is a puzzle with different calculations contradicting each other by 120 orders of magnitude. Clearly, anybody who can resolve these problems has a bright future in science but may also end up tearing modern cosmology apart.
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The Paradoxes That Threaten To Tear Modern Cosmology Apart

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  • by Anonymous Coward

    > What's more, there is an energy associated with any given volume of the universe. If that volume increases, the inescapable conclusion is that the energy must increase as well. So much for conservation of energy.

    ???
    Why cant the energy just be less dense?

    • by Anonymous Coward on Wednesday January 21, 2015 @08:14PM (#48870903)

      The vacuum seems to have energy, so if space itself expands, the vacuum left has to either not have any energy whatsoever or drain the energy from nearby space. And since the energy of the vacuum seems to be constant, the conclusion is that the expansion is creating vacuum with its own energy

      • How can we definitively tell if the vacuum over there has the same energy density as the vacuum over here?

        Further, how can we tell if the energy we think we find in vacuum here isn't energy that arises from particulate contamination? Or, for that matter (ha) is coming from somewhere else? Has someone managed to (a) create a perfect vacuum and (b) measure its energy and (c) determine that whatever was measured as appearing at X, definitely hadn't disappeared from all the possible Ys? Somehow, I doubt it. If

        • Re:Seems... facile (Score:4, Informative)

          by Anonymous Coward on Wednesday January 21, 2015 @10:47PM (#48871947)

          How can we definitively tell if the vacuum over there has the same energy density as the vacuum over here?

          Measurements of expansion rate from distances and from the CMB closely match models that have a constant energy density per unit volume. That is about as simple as it gets for the moment. Until there is good justification for why we would expect the energy to be different at different places, whether from large scale measurements, or theories about small scale things like QFT, there is no basis to assume things are different. But there is always the possibility things are more complicated than they seem.

          • Perhaps the energy is being diluted as it expands. But since the measuring stick being used to measure it is part of the system that is expanding/diluting, it appears constant.
        • Re:Seems... facile (Score:4, Interesting)

          by mattpalmer1086 ( 707360 ) on Thursday January 22, 2015 @05:40AM (#48873551)

          IANAP, but my admittedly also very shallow understanding, is that when we're talking about the energy of the "vaccuum", we mean "energy associated with space itself".

          A vaccuum is typically defined by the absence of matter in a volume of space (but not necessarily light or other energy). But let's exclude those too - there is no matter or electromagnetic radiation at all.

          Even with those exclusions, at a fundamental level space appears to be a seething maelstrom of quantum particles popping in and out of existence. There seems to be some energy associated with "empty" space.

            Some people posit that the vaccuum (i.e. space as we know it) may be "unstable" - that the particular energy it possesses could be lower than it is - and that we're just caught on a local bump in the energy landscape. If the vaccuum ever "fell off" that bump to a lower level, it would apparently spread at the speed of light across the entire universe from wherever it started, destroying everything that currently exists, and leaving behind... I don't know what. More vaccuum, but with a much lower energy associated with it, and with lots of new matter and energy created by the release of the vaccuum energy. Probably.

          Anway, happy for a real physicist to correct me on some or all of the above - that's just my very lay understanding of what is meant by vaccuum energy.

        • Well, there are Cassimir effect experiments done in a vacuum that show energy is coming from somewhere. Someplace we can't see. Is it from repository universes that contain the building block materials for this universe that leak through the aether/ether of space? Is that what dark matter/energy really is? Is it's radiation the fundamental particles we see now? I don't know, but what I do know is that it isn't facile.
      • by robi5 ( 1261542 )

        Nah, it's much simpler. The universe is floating in a sea of vacuum, which seeps through the pores of the universe, i.e. it's statistically unlikely but the energy balance is zero. You can immediately grasp the concept if you think of a squashed sponge ball, which as it expands, it soaks up air from its neighborhood. And of course if physicists are happy to buy into the idea that the Universe just sprang out of nothing, why not think that it sprang out like a sponge ball compressed (or nanoprinted) into a t

      • The vacuum seems to have energy, so if space itself expands, the vacuum left has to either not have any energy whatsoever or drain the energy from nearby space.

        But if cosmological constant [wikipedia.org] is greater thanzero, then our normal intuition of gravity is simply incorrect: what we perceive as gravitational potential is simply the crater at the top of a mountain of infinite height. No conservation law is being broken here, the universe simply contains a built-in wellspring of endless energy that's paying for the

    • by Strangely Familiar ( 1071648 ) on Wednesday January 21, 2015 @08:16PM (#48870933) Homepage
      I think it is because vacuum energy is calculated on the basis of the field theory, which in turn depends on constants like the charge of the electron. I am pretty certain that calculations of the vacuum energy do not depend on the size of the universe. Puzzles like these are really important so that people can think of new questions to ask based on problems they didn't previously realize existed. These puzzles challenge our notions of space and time, which to me, are pretty tenuous notions.
      • by fyngyrz ( 762201 )

        I am pretty certain that calculations of the vacuum energy do not depend on the size of the universe.

        I am pretty certain the idea's never been tested. And may not even be testable. So you might want to adjust your confidence level a bit. At least until we can go everywhere and measure everything. Breath-holding doesn't seem to be called for.

    • by Baloroth ( 2370816 ) on Wednesday January 21, 2015 @10:15PM (#48871779)

      > What's more, there is an energy associated with any given volume of the universe. If that volume increases, the inescapable conclusion is that the energy must increase as well. So much for conservation of energy.

      ??? Why cant the energy just be less dense?

      The FLRW metric [wikipedia.org] (which is what the equation that governs the cosmological expansion of spacetime) has a cosmological constant term in it, initially placed there by Einstein to maintain a steady state universe, but which we now know drives an accelerating expansion of the universe. This constant term is exactly that: a constant (negative) energy per volume of space. More space means more total energy.

      However, TFS and TFA (I've only scanned the referenced paper, but that looks much more reasonable) are absolutely wrong about why this is a problem. It is a problem, but only in the sense of figuring out where it comes from (i.e. what exact mechanism drives the creation of this energy). The fact that energy is not conserved violates no law of physics: in fact, general relativity doesn't conserve energy anyways, and the expansion of the universe certainly does not (even without the non-conservative nature of gravity).

      See, the conservation of energy is a result of Noether's theorem [wikipedia.org], which states that for any differentiable symmetry of the action of a physical system, there is a corresponding paired conservation law. For time symmetry, this is the conservation of energy. However, time on the scales of the universe is not symmetric. There was a beginning to the universe (which alone breaks the symmetry: you can't shift backwards in time more than ~13 billion years), and the universe as it is now looks nothing like it did 10 billion years ago. So we don't expect energy to be conserved in the universe as a whole (even if it is on local scales).

      • by Anonymous Coward on Wednesday January 21, 2015 @10:56PM (#48871991)

        in fact, general relativity doesn't conserve energy anyways,

        GR does conserve energy, but in a very messy way with a lot of subtleties that means it gets skipped over in the grad level intro courses. Especially when dealing with an expanding metric, it is possible to formulate a contrived analogy to potential energy.

        There was a beginning to the universe (which alone breaks the symmetry: you can't shift backwards in time more than ~13 billion years), and the universe as it is now looks nothing like it did 10 billion years ago.

        The beginning of the universe does not need to conserve energy, but things as far as we can tell are conserved after that. The fact that things look different doesn't contradict the type of symmetry needed by Noether's theorem, just as Noether's theorem applies just fine in classical mechanics despite the second law of thermodynamics.

        • by Viol8 ( 599362 )

          "The beginning of the universe does not need to conserve energy, but things as far as we can tell are conserved after that."

          As fas as we can tell beig the important clause there. Besides which - the energy causing the expansion could be coming from outside our universe if one adhers to the multiverse theory , in which case all bets are off.

        • I've always felt like the big bang was an easy out to both explain red shift and allow for creation. Not that I have a problem with creation or the existence of God even; it just seems awfully convenient.

          $1 says we go back to a steady state universe in our lifetime.

          • Enough decades ago, you would have found a great many scientists agreeing with you. Since then, the evidence for the big bang has been piling up, and pretty much everybody who's studied the evidence believes there was a big bang.

            • I also agree with the evidence, and will be shocked if I win that dollar. But I do find the speculation interesting.

              I'll disagree with piling up. We got red shift and the CMB, as far as evidence goes. That's about it.

              Not everything would change with steady state, you'd just have to start with explaining those two things. And yes, a few theories of interest to nerds would change from those changes.

              Here's a thought, the gravitational constant was part of Einstein's steady state universe. He was convinced othe

        • So, I'm definitely not a physicist, but I have a question that your comment seems to be at the root of.

          The beginning of the universe does not need to conserve energy, but things as far as we can tell are conserved after that.

          As far as I understand it, we're trying to figure out what's happening on the edge of the expanding universe, but we have no idea what is outside of our universe that it is expanding into. It could be something that doesn't follow any of our laws of physics and is inexplicable, all we know is that it not this universe. If we know our Universe started in NotThisUniverse, and you mention the beginning of th

      • Your FLRW link does not resolve. Click the first result on this page to get there [wikipedia.org]. "i with a hat" problem...
      • Great post and thanks for the explanation. I do have one nitpick, though

        (which is what the equation that governs the cosmological expansion of spacetime)

        The equation does not govern the expansion, the equation describes or models the expansion. In the same way that the map is not the territory, the math is not the universe.

        --
        JimFive

  • by crioca ( 1394491 ) on Wednesday January 21, 2015 @08:03PM (#48870831)
    The only thing that's tearing cosmology apart is the gradual expansion of space.
  • I don't get it (Score:5, Interesting)

    by slashmydots ( 2189826 ) on Wednesday January 21, 2015 @08:07PM (#48870855)
    If there are no particles moving at all, how does empty space have energy? It's the textbook definition of lack of energy. Empty space cannot impart energy on matter and it can't spontaneously create matter. There's some theory about virtual particles but their net energy is zero when they combine so that's not it. Can anyone explain why empty space has energy?
    • Can anyone explain why empty space has energy?

      Nope, but we have a name for it anyway: Dark Energy.

    • Re:I don't get it (Score:5, Informative)

      by smooth wombat ( 796938 ) on Wednesday January 21, 2015 @08:18PM (#48870949) Journal
      how does empty space have energy?

      That was my question as well until I read Brian Greene's explanation in his book, The Fabric of the Cosmos.

      In short, the Higgs Field. Long answer, think of what we call space as a fabric (hence the title of his book). The Higgs Field is the fabric upon which everything else "sits". Even if there are no particles in a given unit of space, it is not empty because the Higgs Field is still there.

      Start on page 254 of his book and work your way through as he describes the field and how it (supposedly) permeates everything.
    • by Bengie ( 1121981 )
      Virtual particles do impart force. My understanding is that it is a net of zero, Universe wide, but maybe not locally. Virtual particles can push two plates together, and create torque issues with nano-structures.
  • by khchung ( 462899 ) on Wednesday January 21, 2015 @08:08PM (#48870863) Journal

    Perhaps the most dramatic of these paradoxes comes from the idea that the universe must be expanding. [...] yet nobody knows how this can occur.

    Since when did "paradox" became a synonym for "unknown"?

    Yeah, nobody knows how space expands, but how does that make it a "paradox"?

    • by Dastardly ( 4204 ) on Wednesday January 21, 2015 @08:28PM (#48871027)

      Paradox - "a statement or proposition that, despite sound (or apparently sound) reasoning from acceptable premises, leads to a conclusion that seems senseless, logically unacceptable, or self-contradictory."

      The paradox is that energy is supposed to be conserved, but space has energy and is increasing. So, we have a logically unacceptable a conclusion.

      Just because it is a current paradox doesn't mean it can never be resolved. We find an energy source, or figure out the laws of physics which in this case allow for the creation of energy and is stops being a paradox.

      Quantum physics calculations say the vacuum energy is one value while measurements of the curvature of the universe say it is a different value. That is a paradox especially when both Quantum physics and the physics involved in measuring the curvature of the universe seem to both be right in other respects such that making changes to resolve this paradox causes them to stop describing other things accurately. So, we have logically unacceptable conclusion.

      The red shift thing doesn't look like a paradox, but a really cool test of our understanding of cosmological red shift.

      And, the homogeneity problem could be a paradox linearity of expansion says the universe is homogenous, observations say it is not. But, they don't mention whether observations have done a reasonable job of determining the dark matter distribution of the universe.

      There are paradoxes in the article, but it does drift into one topic that is not a paradox and another that is borderline.

      • There are things called paradoxes in relativity, which tend to be people thinking in Newtonian terms part of the time.

        The twin paradox: Harold stays on Earth, while George (separated at birth) travels at relativistic speeds for a while and then turns around and comes back. Despite the fact that from George's point of view Harold and the Earth went away and came back, George is nevertheless younger. (Harold's using the same frame of reference all the time, being unaccelerated - and we ignore general re

    • It's a paradox because everything we know says it can't happen.

      In other words, if a paradox is a contradiction, then here we have all the evidence that shows something can't happen, plus evidence that shows it is happening.
      • by sjames ( 1099 )

        It just means there's something we don't know. The energy comes from something, much like potential energy can become kinetic energy.

        • Indeed, that is the answer to almost every paradox.
          • by sjames ( 1099 )

            True, but paradox is a rather strong word to use in this case. Usually a paradox involves a careful chain of logic that inexorably leads to an absurd conclusion. Particularly when the flaw of reasoning eludes careful examination.

    • If an unknown paradox fell on top of a tree falling in the woods, but no philosophers could debate the paradox since it was unknown, would it affect whether the tree makes a sound?
    • Agreed. Also, if you someone is worried about conservation of energy you have to worry about the big-bang - where everything suddenly appears.

      We don't yet have a good theory that includes quantum mechanics and gravity - and that seems to be central to all of these unknowns. Likely we will figure one out eventually.

      Most of the issues with quantum gravity occur at scales that are not accessible in the laboratory. Every experiment we can do is predicted by existing theories, and we can't reach the conditions w

  • Coming up with better explanations is what science is for.

    Summary: headline is sensationalist clickbait, Slashdot editors are whores, Netcraft confirms Slashdot is dying.

  • by Paul Fernhout ( 109597 ) on Wednesday January 21, 2015 @08:39PM (#48871085) Homepage

    http://www.simulation-argument... [simulation-argument.com]

    But, that does not make it any less real-seeming to all of us being simulated...

    And of course, the universe simulator could be simulated, etc....

    It might be simulated turtles all the way down. :-)

    • by fyngyrz ( 762201 )

      It might be simulated turtles all the way down.

      It's virtual turtles, you insensitive clod!

    • by radtea ( 464814 )

      The simulation argument is nonsense that is only plausible to people who either haven't given it any thought or don't know any physics: http://www.tjradcliffe.com/?p=... [tjradcliffe.com]

      • As with many cosmological argument, that essay called "Imaginary Arguments" by TJ Radcliffe does not prove anything about a potential infinity of nested infinite universes. There is a key hedge there of "given what we currently know of physics". Much of physics (for example the Heisenberg uncertainty principle) is in essence a theory of what we could conceivably learn about the universe and beyond, not actual information on the universe and beyond. Likewise for saying we can see up to a certain distance of

  • by Burz ( 138833 ) on Wednesday January 21, 2015 @08:58PM (#48871225) Homepage Journal

    As entropy in the universe increases, so does the amount of space.

  • The expansion of the universe is fueled by a continuous transition to lower-energy vacuum states. Unlike the normal "false vacuum" model, though, there are a lot of these lower-energy states, which become closer and closer together until they reach a limiting value.

    The graph of these states would probably look familiar - it's similar to the electron transitions for the hydrogen atom, only with the orbitals replaced with "time since the Big Bang". The net result matches the lower value of the vacuum energy

  • Those aren't paradoxes. So space is created. How is that a paradox? Did someone say space is not allowed to be created?
    So energy is created. That violates conservation of energy, but conservation of energy is simply a law that we formulated from experience, and later proved using Noether's theorem by assuming that the laws of physics are time-invariant. Well, it's not valid to extrapolate from our small-scale experiences to the universe, and the laws of physics probably aren't time-invariant at cosmological

    • There is a paradox in that the laws of physics simultaneously say that energy is being created and it can't be created.

      Well, it's not valid to extrapolate from our small-scale experiences to the universe, and the laws of physics probably aren't time-invariant at cosmological scales.

      And therein lies the source of the paradox: it arises because our understanding is incomplete.

  • by As_I_Please ( 471684 ) on Wednesday January 21, 2015 @09:20PM (#48871403)

    It has been known for quite some time that energy is difficult to define rigorously in General Relativity. A good explanation can be found in this post by CalTech physicist Sean Carroll [preposterousuniverse.com]. Key point:

    The point is pretty simple: back when you thought energy was conserved, there was a reason why you thought that, namely time-translation invariance. A fancy way of saying “the background on which particles and forces evolve, as well as the dynamical rules governing their motions, are fixed, not changing with time.” But in general relativity that’s simply no longer true. Einstein tells us that space and time are dynamical, and in particular that they can evolve with time. When the space through which particles move is changing, the total energy of those particles is not conserved.

    As a simple example, imagine a photon traveling through an expanding universe in a region with no other matter or energy (dark or otherwise). The expansion of space stretches the wavelength of the photon (cosmological redshift, which is distinct from Doppler redshift), causing it to lose energy. The photon loses energy with nothing around it gaining. Energy is lost because spacetime itself is changing, so Noether's theorem doesn't apply.

    • Note that the linked blog post was in response to another Arxiv Blog article that makes the same mistake.

    • Re: (Score:2, Interesting)

      by Anonymous Coward

      When the photon's wavelength is integrated over the entire, expanding volume, is the energy still non-conserved? Sure, the kinetic energy depends only on the wavelength, but doesn't the photon also have a gravitational field whose source (energy) now occupies more space? Is the associated gravitational energy the integrated deformation of the space-time in which it resides? The deformation density has decreased with decreased kinetic energy density, but the deformation now exists over a larger region of

      • Read the blog post I linked to above. There's no way to consistently assign an energy density to spacetime curvature. Quoting Prof. Carroll:

        [U]nlike with ordinary matter fields, there is no such thing as the density of gravitational energy. The thing you would like to define as the energy associated with the curvature of spacetime is not uniquely defined at every point in space. So the best you can rigorously do is define the energy of the whole universe all at once, rather than talking about the energy of

    • by PJ6 ( 1151747 )

      As a simple example, imagine a photon traveling through an expanding universe in a region with no other matter or energy (dark or otherwise). The expansion of space stretches the wavelength of the photon (cosmological redshift, which is distinct from Doppler redshift), causing it to lose energy. The photon loses energy with nothing around it gaining. Energy is lost because spacetime itself is changing, so Noether's theorem doesn't apply.

      I wonder if we could add a scale-invariant component, and make the lost energy just a property of measuring it in a non-inflating reference frame.

      Or, I should say, I wonder what contradictions that would lead to.

  • I think it is time to revise the foundations of both our great theories, quantum mechanics and general relativity. This has become more and more evident in the recent decade, but it has been obvious almost from the beginning, since the two theories have been known to be incompatible already since the Solvay conference, if not before, and I think I can see some signs that efforts are being made to move away not only from GR, but also from QM.

    The big problem is of course the inescapeable success of both theor

    • People have been trying to revise the foundations of those theories. The problem is that, while we know they're incompatible, it's apparently really hard to come up with a practical experiment where GR says one thing and QM says another. Given the lack of experimental evidence, about all we can do is come up with ideas on how to make them work together (like string theory), see if they match what we already know, and try to figure out how to get testable predictions from them. The real problem is that w

      • Making more observations is getting harder and harder.

        But that, in a way, is why I think it is necessary to start looking again at some of the things we haven't really got a good enough definition of. I remember Einstein worked at some attempt at defining what a particle is, but I forget which paper; that is the kind of things we need a better understanding of, is my feeling. I think it has always been obvious that 0-dimensional particles are a shortcut, a convenient way of not adrdressing the problem you don't yet have, and the same goes for things like charg

  • What's science's answer to this one?

    1. Any sufficiently advanced civilisation can create a simulation (or more) on a grand scale.
    2. In a simulated world, intelligence and construction may arise, eventually leading to sufficiently advanced simulated civilisations
    3. (... after some thousands of recursions, also recognising that there is plenty of 'time' for that because time is an internal variable of the universe in question...)

    The big Q:

    What is the likelihood that in the vast tree of simulated universes, we

    • This depends on the possible quality and size of a universe simulation. Is it possible to simulate the entirety of a universe using only a finite subset of that universe?

      If yes, then there are (at maximum) an infinite number of simulated universes and and infinite number of recursively simulated universes. Thus the probability of us being the root/real universe is zero ("of measure zero" if you ask a mathematician). Perhaps the holographic principle comes into play to allow the entire universe to be simulat

  • It'a the only discipline where 120 orders of magnitude is a slight disagreement.

  • Looks mostly theoretical.
    https://www.researchgate.net/p... [researchgate.net]

  • by hAckz0r ( 989977 ) on Thursday January 22, 2015 @12:05PM (#48875703)
    The answer to the cosmological problem can be found in thermodynamics, and the same solution simultaneously removes the need for Dark Matter, Dark Energy, and explains the origin of the vacuum energy. By partially defining the photon in physical terms Gravity becomes simply a emergent property of spacetime given the existence of vacuum energy and it's interaction with the spacetime curvature. In my paper I logically present an argument for the thermodynamics as a conclusion, and present a theory based on first principals. I defer the complete definition and the photon and structure of spacetime/matter for a later paper, so I apologize in advance for trying to keep the paper small enough to be readable.

    .
    On The Thermodynamics Of General Relativity.
    http://vixra.org/abs/1412.0270 [vixra.org]

    I have been looking for constructive feedback on these new ideas, so please do so if you have the time. I published this paper simply to get these new ideas out on the table for discussion by the community while I turn my attention to my next paper on solutions to the paradox of Special Relativity, and later the structure of matter and spacetime. The same solution fits all the open issues I know about.
    Thermodynamic Unification Theory https://plus.google.com/u/0/+S... [google.com]

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