back to article Feel guilty for scoffing Easter chocolate? Good news: Scientists have made NEGATIVE mass

A team of physicists from around the world have created a fluid they claim has negative mass. This strange matter has peculiar properties: when it is pushed, it moves in the opposite direction. In other words, pushing the fluid away only brings it closer. Newton's second law states that the acceleration of an object is …

  1. Little Mouse

    Pushing back

    Reminds me of that scene from The Wire, when the two cops are trying to shift a desk wedged into a doorway.

    I'm paraphrasing from memory here, but after much fruitless straining, their conversation went something like:

    1st cop: "It's no good. We're never gonna get it in."

    2nd cop: "IN???"

    1. Chris Tierney

      Re: Pushing back

      https://www.youtube.com/watch?v=_yncfY_hrX0

  2. Yesnomaybe

    Negative mass?

    Or a state that imitates ONE characteristic of negative mass?

    1. Sir Sham Cad

      Re: Negative mass?

      More "a state that displays a characteristic that can be explained by having a negative mass property" if I read the article correctly.

      1. Charlie Clark Silver badge

        Re: Negative mass?

        Talking about mass here definitely muddies the water. The effect seems to be one of negative acceleration but presumably the energy required for the change in direction is provided by manipulating the spin of the atoms?

    2. Schultz
      Boffin

      Re: Negative mass?

      Negative mass for some definition of mass.

      'What definition of mass', you ask? Not any definition that will ever affect the physical reality you are concerned about.

      Just like 'Quantum Teleportation' never teleported a physical object in any sense the layman would consider relevant, this 'negative mass' will never help you build the anti-gravity drive.

      Laws of physics ... you may not like them but we haven't found better ones yet.

  3. Michael H.F. Wilkinson Silver badge

    If all the 100,000 rubidium atoms truly were turned into a system with negative mass, how does that chime with mass (or energy) conservation? The loss of the mass of the rubidium atoms, plus the absolute value of negative mass of the resulting system must be compensated somehow. Even if only a small part of the system was converted to negative mass, the original mass of that part must be stored somewhere, or be released as energy in some way.

    Interesting effect, nonetheless

    1. Rol

      Can't help thinking about the effect of throwing a rock into a pond.

      Water splashes up.

      Is that negative mass, or the energy rebounding in a constricted space?

  4. Gordon Pryra

    Would this mean that we can see black holes?

    Unless there is also negative gravity pulling in all that pesky negative mass?

    Maybe this means that my mates negative round is also a valid concept, he WAS in fact telling the truth when he insisted that the "round worked out even, and was fair by the end of the night", I should stop hassling him to buy when he has already done so, its my pint glass, being positive that its the issue?

  5. Your alien overlord - fear me

    And what about the force of gravity on this experiment? Surely everything should have floated up if it reacted against the force of gravity pulling it down?

    1. james 68

      This was also my first query.

      Along the lines of: Why do they need a second set of lasers to apply a force to see the fluids opposite reaction? Surely gravity is already acting as a force and the liquid should be trying to achieve orbit without further interference?

    2. Bill Gray

      I briefly thought it might float up. But such is not the case.

      The gravitational force between the "negative mass" and the earth is proportional to the product of their masses. Normally, that force (GMm/r^2) would be a positive quantity. Here, it would be a negative quantity.

      The _acceleration_ produced by that force would be what you get when you divide force by mass. For the negative mass, that divides out to be a positive quantity, and the atoms in the experiment fall to the floor at the usual 9.8 m/s^2.

      The only odd thing here is that the earth is pushed away, admittedly very gently, by the negative mass. In theory, if you got a big mass m and a corresponding object with mass -m and put them next to each other, the one with mass m would be repelled by the negative mass and the one with mass -m would get attracted, and they'd go rushing off across the cosmos. I was about to say that I don't see where the energy would come from... but come to think of it, the one with positive mass gains energy mv^2/2, and the negative mass guy ends up with "negative energy" -mv^2/2. All of which seems very weird. But if one stipulates the concepts of negative mass and energy, it seems to be mathematically and physically consistent, albeit weird.

      1. DropBear
        Joke

        Well who'da thunk it - Cyrano's moon craft was real after all, only it didn't work with magnets...

      2. james 68

        @Bill Gray +1 for answering the question and not being condescending.

        But...

        The acceleration would be a positive even if the object were being pushed away from the positive mass just as it would be if it were attracted as it is accelerating in space not decelerating, it is direction which is changed (I could well be wrong, but this is how I view it).

        The application of a force shown in the experiment, a positive pushing force, caused the object to be attracted, so why would the inverse also not be true? If gravity is acting as a pulling force why would the acceleration not be sending it away from the earth?

        Serious question.

        1. Bill Gray

          @james 68 Sorry, just got 'round to noticing this!

          I think the issue is that the earth's gravity would attract a "normal", positive mass, but would repel this exotic "negative" mass. (F=GMm/r^2; G=gravitational constant, M=earth's mass, and r=distance from the center of the earth are all positive, both for a "normal" mass and this "exotic" one; but the latter has opposite sign, causing the sign of F to flip.)

          So the earth's gravity causes a repelling force on the negative-mass object... which causes it to be attracted. It is, effectively, a double negative cancelling out.

          You're right that it's a serious question, in the added sense that the answer is (to both of us, and I'm pretty sure to physicists in general) unclear and may remain that way until an actual experiment is done.

          Come to think of it... when I suggested that a positive mass would attract a negative mass, which would in turn repel the positive mass, so that they would accelerate across the universe, I figured it wouldn't help for spacecraft propulsion unless you got (say) moon-sized masses of each. But if you take a spacecraft and add a matching amount of negative mass, so that their net mass is zero, and you push it... does the acceleration (force/mass) tend toward infinity as the mass approaches zero? Inquiring minds _definitely_ want to find out!

  6. taxythingy

    Up next: Study replication refutes results

    And at least as likely is someone else finding rubidium atoms being kicked out the other end, generating an opposing force. But that will fall in the 'Hmm, that's interesting' department, rather than 'Lose weight with this one, weird, 0.1K frozen (let it go!), laser-blasting, physics-defying-gravity trick.

  7. Alan Johnson

    Negative masses in this sense very old and well known

    Holes in a semiconductor act as if they have a positive mass because in this situation electrons behave as if they have a negative mass in exactly the sense described in the article. This is ancient physics. Yes a new area, Yes very interesting and impressive but not new.

    https://en.wikipedia.org/wiki/Effective_mass_(solid-state_physics)

    1. Paul Kinsler

      From the abstract: "condensate whose dispersion features a region of negative mass"

      AJ is correct, although here they are claiming a hydrodynamic version of the effect; but there seem to be a fair number of (admittedly unsurprising) approximations to get to the hydrodynamic model, so perhaps "hydrodynamic-like" version might be a better phrase.

      This is essentially a dynamic effect: i.e. if you wobble the condensate in the right way it reacts as if it has negative mass - but given a long continuous push, it will not. In fact very mearly all "negative" mass/poisson-ratio/ permittivity/ refractive-index/ etc claims are of this dynamic type.

  8. John Brown (no body) Silver badge
    Coat

    So, they invented...

    ...Cavorite?

    1. Charlie van Becelaere

      Re: So, they invented...

      Either that or they have a working tractor beam.

      1. Orv Silver badge

        Re: So, they invented...

        Nah, we already have those. https://en.wikipedia.org/wiki/Tractor_beam#2010s

  9. danR2

    limited context

    If you read the paper, you'll see the narrowly circumscribed limits under which they 'push' (a word that appears nowhere in the publication) the condensate. Words like 'quasimomentum', and the simple logic that something cannot go toward the pushing force, if the force is applied with a stout finger (supercooled, of course), should be a clue.

    1. Trigonoceps occipitalis

      Re: limited context

      Cutting edge physics:

      "When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean—neither more nor less."

      Alas for the Newtonian Universe.

  10. Captain DaFt

    Help me out here

    So, if I'm designing an artificial gravity, should I put a mass generator in the floor, or a negative mass generator in the ceiling?

    Or both!?

    1. IT Poser

      Re: Help me out here

      Why not do both? That way when one system is on the fritz you still have half-gravity.

      While you're at it can you put some generators in the bulkheads? I see no reason why we couldn't use this technique to make inertial dampers. Want to do a 10G burn? The only thing shaken is your martini.

      1. Pompous Git Silver badge

        Re: Help me out here

        "The only thing shaken is your martini."
        A proper martini is stirred, not shaken. Also much better made from chilled gin and vermouth. Ice is a diluent.

  11. michael cadoux

    This is scarcely even negative INERTIAL mass. We don't know whether negative mass in the sense of bending space in the opposite way from ordinary mass (i.e. gravity) is possible. Which is a shame, as it's a necessity for the Alcubierre drive.

  12. Anonymous Coward
    Anonymous Coward

    "Feel guilty for scoffing Easter chocolate?"

    NOPE

  13. Anonymous Coward
    Anonymous Coward

    If I have this straight..

    to lose mass by eating chocolate, I have to buy kit to cool said chocolate down to a temperature a smidge above 0K, get severe frostbite by then applying tongue to choccy to make it push its way into my mouth which then also gets severe frostbite (when talking chocolate and I, we are NOT talking small quantities, so the thermal inertia of the choccy is likely to be significant), at which point my lower face probably cracks and falls off, so the question of whether and how I manage to swallow the stuff becomes moot?

    I think I'll pass!

    Interesting boffinry, though...

    (reaches for regular bar of favourite vanilla-flavoured white choccy)

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