Negative Mass, Phlogiston and the State of Modern Cosmology

A graphical representation of something or other.

I’ve noticed a modest amount of hype – much of it gibberish – going around about a paper published in Astronomy & Astrophysics but available on the arXiv here which entails a suggestion that material with negative mass might account for dark energy and/or dark matter. Here is the abstract of the paper:

Dark energy and dark matter constitute 95% of the observable Universe. Yet the physical nature of these two phenomena remains a mystery. Einstein suggested a long-forgotten solution: gravitationally repulsive negative masses, which drive cosmic expansion and cannot coalesce into light-emitting structures. However, contemporary cosmological results are derived upon the reasonable assumption that the Universe only contains positive masses. By reconsidering this assumption, I have constructed a toy model which suggests that both dark phenomena can be unified into a single negative mass fluid. The model is a modified ΛCDM cosmology, and indicates that continuously-created negative masses can resemble the cosmological constant and can flatten the rotation curves of galaxies. The model leads to a cyclic universe with a time-variable Hubble parameter, potentially providing compatibility with the current tension that is emerging in cosmological measurements. In the first three-dimensional N-body simulations of negative mass matter in the scientific literature, this exotic material naturally forms haloes around galaxies that extend to several galactic radii. These haloes are not cuspy. The proposed cosmological model is therefore able to predict the observed distribution of dark matter in galaxies from first principles. The model makes several testable predictions and seems to have the potential to be consistent with observational evidence from distant supernovae, the cosmic microwave background, and galaxy clusters. These findings may imply that negative masses are a real and physical aspect of our Universe, or alternatively may imply the existence of a superseding theory that in some limit can be modelled by effective negative masses. Both cases lead to the surprising conclusion that the compelling puzzle of the dark Universe may have been due to a simple sign error.

For a skeptical commentary on this work, see here.

The idea of negative mass is no by no means new, of course. If you had askedk a seventeenth century scientist that question and the chances are the answer would  have involved the word phlogiston, a name derived from the Greek  φλογιστόν, meaning “burning up”. This “fiery principle” or “element” was supposed to be present in all combustible materials and the idea was that it was released into air whenever any such stuff was ignited. The act of burning separated the phlogiston from the dephlogisticated “true” form of the material, also known as calx.

The phlogiston theory held sway until  the late 18th Century, when Antoine Lavoisier demonstrated that combustion results in an increase in weight implying an increase in mass of the material being burned. This poses a serious problem if burning also involves the loss of phlogiston unless phlogiston has negative mass. However, many serious scientists of the 18th Century, such as Georg Ernst Stahl, had already suggested that phlogiston might have negative weight or, as he put it, `levity’. Nowadays we would probably say `anti-gravity.

Eventually, Joseph Priestley discovered what actually combines with materials during combustion:  oxygen. Instead of becoming dephlogisticated, things become oxidised by fixing oxygen from air, which is why their weight increases. It’s worth mentioning, though, the name that Priestley used for oxygen was in fact “dephlogisticated air” (because it was capable of combining more extensively with phlogiston than ordinary air). He  remained a phlogistonian longer after making the discovery that should have killed the theory.

The standard cosmological model involves the hypothesis that about 75% of the energy budget of the Universe is in the form of “dark energy”. We don’t know much about what this is, except that in order to make our current understanding work out it has to act like a source of anti-gravity. It does this by violating the strong energy condition of general relativity.

Dark energy is needed to reconcile three basic measurements: (i) the brightness distant supernovae that seem to indicate the Universe is accelerating (which is where the anti-gravity comes in); (ii) the cosmic microwave background that suggests the Universe has flat spatial sections; and (iii) the direct estimates of the mass associated with galaxy clusters that accounts for about 25% of the mass needed to close the Universe.

A universe without dark energy appears not to be able to account for these three observations simultaneously within our current understanding of gravity as obtained from Einstein’s theory of general relativity.

I’ve blogged before, with some levity of my own, about how uncomfortable this dark energy makes me feel. It makes me even more uncomfortable that such an enormous  industry has grown up around it and that its existence is accepted unquestioningly by so many modern cosmologists.

Isn’t there a chance that, with the benefit of hindsight, future generations will look back on dark energy in the same way that we now see the phlogiston theory?

Or maybe, as the paper that prompted this piece might be taken to suggest, the dark energy really is something like phlogiston. At least I prefer the name to quintessence. However, I think the author has missed a trick. I think to create a properly trendy cosmological theory he should include the concept of supersymmetry, according to which there should be a Fermionic counterpart of phlogiston called the phlogistino..


21 Responses to “Negative Mass, Phlogiston and the State of Modern Cosmology”

  1. “I’ve blogged before, with some levity of my own, about how uncomfortable this dark energy makes me feel. It makes me even more uncomfortable that such an enormous industry has grown up around it and that its existence is accepted unquestioningly by so many modern cosmologists.”

    The reason is that it is the only sensible theory that explains all the data. If you find another one, let us know. Going back a few years, fans of dark energy were a small minority, often considered fringe. (As you know well yourself, not that long ago this was also true of those who believed that Omega_m was less than 1.) The reason that believers in the cosmological constant (as I prefer to call it) are now the majority is because of observations, cosmology now being a data-driven science, no longer an armchair science (for which IKEA products are indeed suitable).

    Almost 4 years ago, I was at a conference where the topic was alternatives to LambdaCDM. Almost everyone there worked on non-standard stuff, so it is not the case that there is a standard-model monoculture. At one point, George Efstathiou set the bar low by saying that if anyone had an alternative theory which did nothing more than explain currently known data as well as the standard model, he would give them a job in Cambridge. I don’t think that he has hired anyone as a result.

    • telescoper Says:

      Yes, but I don’t think just putting it in a box marked `dark energy’ really explains very much. It’s really just a placeholder until we have an idea of its physical origin.

      • Of course, it is on the left-hand side of the Einstein equation, so it is no more mysterious why Lambda is non-zero than it is why G is non-zero.

      • telescoper Says:

        So why is G non-zero?

      • telescoper Says:

        And does it have to be on the left? Nowadays people call it dark energy so it lives inside the energy-momentum tensor on the right!

      • To elaborate: Yes, if it is some “stuff” with w = -1 then perhaps one might want to know “what it is”. But if it is on the left-hand side of the Einstein equation, it is really just a constant, like G is a constant. We don’t know why G< is non-zero, we don’t know why it has the value it does, we don’t know why active gravitational mass should be proportional to inertial mass (GR explains why passive gravitational mass is proportional to inertial mass), why gravity manifests itself as an acceleration, etc. So, to be fair, you should say as well that “gravity” is just a placeholder for our ignorance.

      • telescoper Says:

        Fair point, but I think `gravity’ accounts for a greater range of phenomena than the Lambda addition does.

      • My point is that both constants are on the same footing. There is an entire industry trying to explain away Lambda since some people don’t understand it, but no-one trying to explain away G.

      • “Nowadays people called it dark energy so it lives inside the energy-momentum tensor on the right!”

        Bad journalism does not a theory make. 🙂 “Dark energy” is almost as bad as “God particle”. As Sean Carroll pointed out, many things are dark and everything has energy, so it’s really a bad name. A name which he suggested, but which never caught on, which is more descriptive, is “smooth tension”.

      • Anton Garrett Says:

        Phillip: the inverse square law is well known to be a consequence of quantum field theory with a zero-mass mediating particle.

        And I am convinced that the correct gauge theory of gravity is not GR but Einstein-Cartan-Kibble-Sciama theory, which is a particular torsional generalisation of GR with bulk aligned fermionic spin density being the source of the torsion field (so it predicts identically to GR in all tests to date). Unlike GR it is mediated not exclusively by a massless spin-2 boson but also by massive spin-0 and spin-1 bosons. That suggests both attractive and repulsive forces, aha! Unfortunately there does not appear to be bulk *aligned* fermionic spin density in the universe, so this does not seem to solve the dark energy problem. (ECKS theory is also nonrenormalisable, just like GR.) But I consider it a step forward, at least.

      • Phillip Helbig Says:

        “so it predicts identically to GR in all tests to date”

        What about future tests?

        Of course, there is no evidence that gravitons exist. Many people assume, of course, that gravity can be described by a field theory, but there is no actual proof that gravitons exist.

      • Anton Garrett Says:

        When the mass-energy is fermionic then the source term in the gravitational field equations has to be operator-valued since the 1-particle Dirac equation is inconsistent. So the gravitational field has to be operator-valued to match. And gravitational waves have been observed. Therefore…

  2. I thought it quite a nice article, and was struck by the way that, as so often, something Einstein mentioned in passing at the dawn of modern cosmology might be useful.
    My main caveat was the lack of references to historical work. When mentioning Einstein’s early changing view of the cc , the author could have referred to many studies of this (including our own).Similarly, when mentioning Einstein’s reported “biggest blunder” comment, the author could have cited recent studies (including our own). I sometimes wonder why I bother with this historical stuff – when physicists make reference to history, they typically ignore historical studies in a way they would never ignore technical work

  3. […] post from Friday about negative mass in cosmology reminded me of my days at Queen Mary and discussions I had at that time with Bill Bonnor, who […]

  4. Peter: in modern times (post 2005) Luc Blanchet has also worked/written papers in dark matter models involving negative mass. Its strange that this work is not cited in that paper.
    Also, Rovelli has pointed that the cosmological problem is complete hype. (see the discussion at

    • Indeed. I’ve mentioned that paper here many times. You can find it on arXiv. The version on arXiv is not properly published anywhere since it is an extended (and hence better) version of a Nature paper which was part of a debate with, IIRC, Rocky Kolb and allies.

      The Foundations of Physics paper linked to above (which also mentions my paper on the topic) is a similar deconstruction of the flatness problem.

      • As I wrote on another blog:

        Their arXiv paper is the one you should read. A shorter version was published in Nature, along with an opposing viewpoint courtesy of Rocky Kolb (who, not that long ago, was telling us that Omega_matter was 1—draw your own conclusions).

  5. […] Coles (@telescoper), “Negative Mass, Phlogiston and the State of Modern Cosmology,” In The Dark, 07 Dec 2018; entre […]

  6. If instead of negative mass, it is the energy of a graviton fluid (plasma, condensate?), and if the physical analog of continuous production is emission/jetting of gravitons from galactic SMBH, then this makes a lot of sense.

    It then follows that if the energy of the graviton fluid changes based on the “mass” of nearby matter, and that permittivity and permeability of the graviton fluid are based on energy, then GR’s narrative is falsified, and the math needs recasting, but is ok, until near the scale of gravitons.


    weak force = graviton electric field
    strong force = gravioton magnetic field

    and so on. See my blog posts here:

    J Mark Morris

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