Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question on negative matter

  1. Jan 22, 2007 #1
    High energy physics and the standard model have unequestionable come up with all kind of different particles, which are unlike the matter of which our own world exists (well they exist of course in our own world, but ordinary atoms is made of only some of those particles). As for instance the concept of anti-matter, which are existing forms of matter, but are very rare (since they annihilate with normal matter).

    However, all particles are either having a zero mass or a positive mass.

    In which way are particles with negative mass "forbidden" by the standard model and the known laws of physics?
    How would such particles behave, if they could exist?
    (what if similar particles, but one with positive mass and other with negative mass would annihilate? It would not leave any energy, unlike matter - anti-matter annihilation).

    (I assume for instance the negative matter - i.e. matter with a negative mass - are in many ways the same, also excert gravitational force, but only in the interaction with normal (positive mass) matter, they would behave repulsive.)

    I assume that if negative matter could exist, we would sure detect it.

    But what "forbids" nature to have negative mass particles?
    Last edited: Jan 22, 2007
  2. jcsd
  3. Jan 23, 2007 #2
    No response by anyone?

    Is there no scientific explenation to give why particles with negative mass do not arise?
  4. Jan 23, 2007 #3


    User Avatar
    Science Advisor

    In relativity, the relevant quantity is the SQUARE of the mass. Therefore, there is no substantial difference between positive and negative masses. Instead, one can talk about positive and negative - energy. In gravity, negative energy creates negative curvature.
  5. Jan 23, 2007 #4
    Heusdens, there appears to me to be a need for more definition in your question. You have begun by asking about "negative mass," which you later define as having two qualities: one, an annihilation reaction would produce no energy, and two, the "negative mass" would repel "positive mass."

    I think you have coined the term "negative mass" yourself, from a combination of the mathematical operation of subtraction and the physical notion of mass. I would suggest rephrasing your question without this neologism, which may be confusing your inquiry.

    So, taking the liberty to rewrite your question, I would take out the words "negative mass" and replace them with the actual qualities you have defined. Then your question becomes:

    In which way are particles with "the following qualities" "forbidden" by the standard model and the known laws of physics? One, they leave no energy residue upon annihilation, and two, they repel mass.

    It may also be helpful to state this question in a simpler form by asking if they can exist rather than why they cannot exist. So I would restate your question something like the following: Can a particle exist (under the standard model and the known laws of physics) which leaves no energy upon annihilation and which repels mass?

    First, how would we know if such a particle did exist? If it leaves no energy upon annihilation, how would we detect it? And if it repels mass, would it not quickly accelerate to light speed? All the mass in the known universe would be pushing it away from us.

    So it seems you may be asking for a particle which moves at light speed and has no energy...a seeming conflict, not with the laws of physics and the standard model, but internal to itself. Mass moving near light speed would have near infinite energy. The combination is not so much a violation of physics as a violation of the definition of "particle."

    It seems to me then that you are asking if a particle can exist that is not a particle.

    To go further I think you need to ask, "what is gravity?" and "what is energy?" And then, "what is a particle?" These are all behaviors of physical things. Can anything exist which has no physical behaviors?

    I wish you good fortune in your quest.

  6. Jan 23, 2007 #5
    It could be restated as why can charges be positive and negative, but masses only positive.

    Positive and negative charges attrack one another, and positive masses attract each other.

    From that one might conclude that negative masses also attract each other, but a negative and positive mass repell each other.

    General relativity might not explicitly forbid negative mass or energy, but does the Standard Model forbids negative masses?
  7. Jan 23, 2007 #6
    I am no expert on the subject but here is one thing that I have considered:

    If you have a test particle in the gravitational field of a planet, it will experience a "force" that tries to push it away from the planet. However, since it has a negative mass, it will react in the opposite direction of that force. As a result, it will accelerate toward the planet just like a particle with a positive mass. This tells me that whether a particle as a positive mass, a negative mass, or any mass in between (including no mass), it will have the same acceleration in a gravitational field. This seems to me like strong evidence that gravity is the curvature of spacetime itself.
  8. Jan 24, 2007 #7
    One might look at the history of negative numbers for some guidance here. There was a time, not so long ago, when the idea of negative numbers was hotly disputed. One might count the number of objects in a catagory, maybe for example the number of sheep in a flock, but what is the meaning of a negative one sheep? We now rather easily separate the math part from the object part, and think of a "negative sheep" as the effect of removing one sheep from the group. You see that the negative one sheep is not an object, but an operation.

    So for mass, if mass can be counted as we count objects, (say if mass is related to some number of Higgs interactions or some other number of smallest mass reactions), we might think of negative mass not as an object but as an operation, as of removing some of the interactions or reactions from a system.

    I hope you see that I am trying to accept and make some sense of your insistance on using the term "negative mass," even though you have not yet said what you imagine mass to be. It is by no means clear if mass is a countable quantity at all. Are we to think of mass as a collection of little hard objects in some sort of a container, like marbles in a sack? Or may we think of mass in some kind of field terms, where mass is to be thought of as some sort of interaction, such that position can affect mass just as position affects the strength of the force on electric charges? You have noticed of course that magnets attract or push away with more force when they are closer together. Yet we do not think of the amount of charge on an electron changing with its position, but only the strength of the charge interaction.

    Gravitational force has the same property, increasing with position, so should we not also think of gravitational force in terms of a field, where the force changes with position, not with a number of gravitational "charges?" An object close to the surface of the earth experiences more gravitational force, but is not said to have more mass.

    I am trying here to separate the math from the object being counted. There is not an object called a "negative sheep," the idea of which was and still is rightly considered absurd. Yet you seem to be insisting that there should be an object, a particle, a negative mass particle, which can be counted as if it were a pebble. Yes, a handful of pebbles has more mass than a single pebble (where all are about the same size and density anyway), but neither the single pebble nor the handful has more or less mass by virtue of its position.

    I must ask you again, if you insist on carrying this conversation futher, to define mass in some way that can resolve the particle/field duality. Your question cannot be answered until you do so, or rather, it can be answered either way, depending on your resolution.

    You have an ability to think about these abstract things, and an ability to communicate your thoughts, and that is good. But really you must be more careful of your logic. Start with the definitions, and then work on the relationship between the defined objects.


  9. Jan 24, 2007 #8
    I agree with the remarks given that a "negative" mass concept is very strange indeed. I do not hold it possible that such exists.
    Yet intuition might be wrong sometimes, since neither would I hold it possible that negative energy densities could exist, or repulsive gravity, for instance.
    Yet these latter are notions which are hold to exist and manifest themselves in the early universe.

    It is also a remarkable fact that, while other properties of matter, like (electric or color) charge, exists in both positive and negative quantities, mass on the other hand does not have this feature.
    At least not that we have ever detected.

    There are more strange feautures. A monopole (a particle with only one magnetic pole or magnetic charge) would be equally strange, and has never been found. Yet, there are theories that allow for the existence of monopoles (so they are not theoretically excluded), and in fact some theories would give rise to their existence as an artefact of the early universe.

    So, although I don't hold it possible for mass to be negative, it is not much stranger imo as having monopoles.
    What disallows (within he theoretical framework of the Standard model) particles for having a negative mass?
    And supposing that particles could exist, just like normal material particles, with the only difference that they contain a negative mass, in what way would they react differently?
    As argued above, they would not even be repelling each other, since although the force between a positive mass and a negative mass would yield a negative force, at the same time this negative force yields a positive acceleration.
    On the other hand however, the gravitational interaction between negative masses, would yield a positive gravitational force, and this would yield a negative acceleration. Which means negative masses repel each other.
    If all other interactions would be the same as for positive mass, atoms of negative matter could be possible as well as objects bound by the electrical force, but larger gravitationally bound objects could not exist.
    And unlike anti-matter, which would annihilate with normal matter and would convert to energy (E=mc2), an annihilation of positive mass and negative mass particles would have a zero sum mass, and would not convert to energy. Which would mean, neither would it cost energy to create a positive mass particle and it's negative mass anti-particle...
    If that were so, we would be literally drowned in them...

    So, it's not likely they could exist.
    Last edited: Jan 24, 2007
  10. Jan 24, 2007 #9
    Again, Heusdens, I think you are confusing mathematics with physics. For example, you speak of 'negative' acceleration as if it were somehow qualititatively different from 'positive' acceleration.

    In the old days people spoke of acceleration as opposed to deceleration. This is no longer the fashion. There is no difference between acceleration and deceleration. In this case the negative mathematical term merely is an indicator of direction in space. As you probably know, the known laws of physics all operate the same no matter which direction you choose to point your apparatus.

    It is a logical inconsistancy, not a physical or mathematical one, to assert that there is a category (I use that term loosely because I have not had the honor of becoming acquainted with Catagory theory) which contains a definable object called 'negative mass' which can be said to exist, or to not exist.

    It seems to me that you have tried to define an object which cannot logically be itself. If I may paraphrase, it is as if you have said: 'Aristotle is a man. All men are located inside the orbit of Mars. Aristotle lives on Io, a moon of Jupitor.'

    If you know your solar geometry, you will see immediately that one or more of the statements above has to be false. I think it is the same with your attempt to define a particle which cannot be a particle. The qualities which make a particle are contrary to the amphigory which you describe. It is internally inconsistant to talk about a particle which travels at the speed of light. Such a particle would have to have infnite energy, not zero energy as you describe.

    What you have done, imo, is to set up a paradox and then challenge passers by to explain why it cannot be so. Paradox is not flawed thinking, it is, formally, not thinking at all. Can an object be larger than itself? I challenge you to prove that there is no such object.

    I don't think I can explain this any more clearly.

    Keep thinking.

  11. Jan 24, 2007 #10


    User Avatar
    Homework Helper

    In your particle/anti-particle example, let's say e- and e+ each with mass m_e are annihilated. giving just a some photons which are MASSLESS. So, where has the mass gone? ok, so we say mass has been turned into kinetic energy. now, negative mass idea seems more subtle, cancellation of this type is not what you really mean by negative mass (as you said) but what do you actually mean? you said you want cancellation of energy!

    common sense says if A+B =0 then A = -B, so in the annihilation example, you could in a sense interpret it as anti-particle having a negative mass... but we all know that that's wrong because +ve mass simply means +ve energy. So, if you insist that you talk about negative mass (in your definition), then negative energy must come in somewhere... but unfortunately no one really know what's negative energy is... perhaps some new physics is needed!
  12. Jan 24, 2007 #11
    Unfortunately, the intuition that something with negative mass would have negative energy is not necessarily true.
    Afterall, according to relativity, E^2 = m^2c^4 + p^2c^2, which simply reduces to E = mc^2 at rest. This says nothing about what it would mean to have negative mass. If something would have negative mass then, it could still have positive energy and simply act differently as far as gravity and inertia are concerned.
    On the other hand, according to GR (though I do not know why since I have not studied GR. This is only what I've read), a particle with negative energy would necessarily move at superluminal speeds (i.e. be a tachyon). These have never been observed (nor do we know if it would be possible to observe them if they would exist), and in most theories, the existence of them would cause the entire theory to break down. Therefore, if negative mass would necessarily yield negative energy, the existence of it would cause the majority of modern theories to break down.
  13. Jan 24, 2007 #12
    See this link:
    Where it is stated:
    "The conclusion that we can draw from all of this is that Einstein's general theory of relativity does seem to have a loophole which would allow for the possibility of negative gravity from an object with a negative mass."

    "Fortunately for this discussion general relativity was used in the late 1950's by the British physicist Sir Hermann Bondi to investigate the effects of negative mass. Bondi pointed out that when general relativity is considered purely as a theory of gravity, mass never actually appears. It first appears when the equations are solved in a way devised by the German physicist K. Schwartzschild. Then mass appears as a constant of integration. Bondi noticed that this mass constant could be made either positive or negative. He was able to show that when m is made negative, both the inertial and the gravitational mass effects are reversed. The results of Bondi's calculations can be summarized in a few words: a positive mass attracts all nearby masses whether positive or negative; an negative mass repels all nearby masses whether positive or negative."

    Hermann Bondi, "Negative Mass in General Relativity", Reviews of Modern Physics 29, 423 (1957).
  14. Jan 24, 2007 #13


    User Avatar
    Homework Helper

    mmm... you have E = mc^2 wouldn't -ve m then gives -ve E? :smile:

    anyway, I wasn't talking in those lines at all. I was simply referring to the original poster's comment on what he may think negative mass should behave... namely, annihilation of +ve and -ve mass gives no energy... ie.. energy is somehow destroyed! such bizzare phenomenon is analogous to the having "negative energy" object annihilate some "positive" energy object. that's all. But one must be very careful when trying to interpret what negative energy really means.
  15. Jan 24, 2007 #14
    No, when p=0 the equation is E^2 = m^2c^4, which is completely ambiguous as far as the sign of energy.
  16. Jan 24, 2007 #15


    User Avatar
    Homework Helper

    I am aware of that... that's why the :smile:
  17. Jan 24, 2007 #16
    Rade, this link took me to an article by John G. Cramer in Analog Science Fiction and Fact magazine. He references "Hermann Bondi, "Negative Mass in General Relativity", Reviews of Modern Physics 29, 423 (1957)” His Wiki Bio. is here:


    It seems he died in September 2005, and was responsible for the steady state theory of the universe. There is also a link to sites where his papers may be found. Here is one which offers the referenced paper:


    Here is a link from the above site which offers the paper in PDF:


    It appears the paper is not available to the general public. You need a username and password from the organization. They do offer to sell you a copy for $60.00.

    It seems the paper has 38 refereed citations, including one by Kip Thorne.

    Cramer's paper is entertaining but I wouldn't rate it for reliability. Note that he says there is a loophole in Einstein's theory...that is somewhere short of trying to determine the existence or non-existence of negative matter. I scanned the article and did not notice any mention of annihilation without release of energy.

    However I will have to retract my thought that the OP had created a neologism. It does appear the idea has been given some serious attention. I still think it is a logical error and belongs at best in the zoo of imaginary creatures.

    Thanks, Rade, for the interesting side track.

    Last edited: Jan 25, 2007
  18. Jan 25, 2007 #17
    Yes, pardon my incorrect statements. But you know that force and acceleration are in fact vectors. So, while positive mass would accelerate in the direction of the applied force, negative mass would accelerate in the opposite direction.

    Which would be quite absurd, I absolutely agree with that.

    The idea that 'negative mass' particles travel with the speed of light, was not implied by me.
    Are photons particles? They do travel the speed of light.
    So, I think your argument would have to state that particles with a non-zero rest-mass can not travel the speed of light.

    That is quite obvious.
    But what in the definition of a negative mass particle is so obvious paradoxical?
    For a property of charge it works perfectly well, we can define a charge to have either negative quantity or positive quantity, without running into any paradoxes.
    If it were for logic, we could also say that magnetic monopoles are absurd, or paradoxical, yet higher energy physics sees these particles as quite possible....(apart from the fact, they have never been observed contrary to their possible existence, which is [or was], if I recall well, some problem for the hot big bang scenario, which has only been fixed by the cosmological inflation scenario which gets rid of these monopoles).

    I think it is (sometimes) more subtle then the paradox you present.

    And be aware of the fact that 'formal logic' has some problems explaining quantum mechanics, if we use our normal sense of formal logic - based on every day experience and macroscopic objects - we must conclude that the quantum world is paradoxical and contradictionary.

    Does that imply that the quantum world is not 'real' because it is paradoxical?

    And pls. be aware, I do not claim that such a thing as negative massed particles can exist, I just wanted to explore the reason why this would not be the case.
    Last edited: Jan 25, 2007
  19. Jan 25, 2007 #18

    This is quite interesting. At least it shows it has been investigated.

    There is one thing lacking, how does a negative and positive mass behave, do they attract or repel each other?

    Well, that has been calculated also, they negative and positive masses would accelerate both in the same direction.

    From the paper: http://www.npl.washington.edu/AV/altvw14.html

    About the mass-energy the paper says:

    (emphasis mine)

    Purely theoretically, if negative mass particles could exist, we would be drowned in them, since it costs no energy to create a positive and negative particle pair.
    As soon as they exist, they would accelerate away with a constant acceleration, and bump into other particles, created in the same way as a pair of positive and negative particles.
    If a positive mass particles bumps into a negative mass particle of the same mass (or vice versa) they would annihilate, leaving no energy.
    In the long run, the particles not bumping into each other would split into portions were positive mass particles reside (which attract each other) while the negative mass particles repell each other, so they would not clutter together but would spread out maximally.
    A pair of positive mass and negative mass of which both would not bump into anything, would go on accelerating, and near the speed of light..
    On the whole, this whole process starts and ends with no nett-energy...

    Of course, this scenario does not account for any of the other forces, so it would be far from realistic....
    Last edited: Jan 25, 2007
  20. Jan 25, 2007 #19
  21. Jan 25, 2007 #20
    The last webpage (http://www.concentric.net/~pvb/negmass.html)mentions effects of gravity on the hypothetical 'negative mass' in earth gravity:

    At least this tells us that - if at all - negative mass particles could exist, we would not find them on macroscopic scales, so there are not 'negative mass' galaxies, stars, planets or even rocks or dust. Maybe not even atoms.

    This is also interesting:

    (emphasis mine)

    So, we can at least theoretically claim that the 'negative mass' concept can be based on something, namely the negative energy of a gravitational field.

    Although, pure speculative, this next page goes into some more detail about the consequences of that speculative thought about 'negative mass' in the form of the gravitational field.

    Last edited: Jan 25, 2007
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Question on negative matter
  1. Matter & Energy (Replies: 7)

  2. Dark matter (Replies: 8)

  3. Dark Matter (Replies: 3)