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Physicists Observe 'Negative Mass' (bbc.com) 117

Physicists have created a fluid with "negative mass," which accelerates towards you when pushed. From a report on BBC: In the everyday world, when an object is pushed, it accelerates in the same direction as the force applied to it; this relationship is described by Isaac Newton's Second Law of Motion. But in theory, matter can have negative mass in the same sense that an electric charge can be positive or negative. Prof Peter Engels, from Washington State University (WSU), and colleagues cooled rubidium atoms to just above the temperature of absolute zero (close to -273C), creating what's known as a Bose-Einstein condensate. In this state, particles move extremely slowly, and following behaviour predicted by quantum mechanics, acting like waves. They also synchronise and move together in what's known as a superfluid, which flows without losing energy.
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Physicists Observe 'Negative Mass'

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  • Last Post (Score:5, Funny)

    by Big Hairy Ian ( 1155547 ) on Thursday April 20, 2017 @09:04AM (#54269321)
    I'll get my coat
    • This negative mass effect looks a lot like the usual negative mass effect to describe some collections of holes/electrons. One can explain some of the phenomena of these as acting like they have a negative mass or negative (negative) charge. But they are mathematical fictions since they only arise as apparent behaviours on a fictional individual represeting the effective forces created by the correlated motions of a large ensemble. One can do something similar with magnetic monopoles. There are not (su

    • Pics or it won't happen!

  • by Headw1nd ( 829599 ) on Thursday April 20, 2017 @09:12AM (#54269389)
    This sounds actually groundbreaking. Does anyone have more details? Were the authors trying to generate negative mass or was this an unexpected side effect? Obviously this is going to require some replication, but I'm excited.
    • Maybe this bit of information will be useful information towards creating anti-gravity propulsion?? Who knows.. There's a lot of stuff out there we don't know.
    • Re:Wow (Score:5, Interesting)

      by Baloroth ( 2370816 ) on Thursday April 20, 2017 @10:10AM (#54269885)

      This sounds actually groundbreaking. Does anyone have more details? Were the authors trying to generate negative mass or was this an unexpected side effect? Obviously this is going to require some replication, but I'm excited.

      That's because the headline is some of the worst sensationalistic tabloid journalism level garbage I've ever read. They did not observe "negative mass". They created a system wherein, under specific circumstances, part of the system behaved as if it mathematically had negative mass. Note that the entire system and every part of it individually still has positive mass: however, because of the way the system interacts with itself, when you do very specific things to it, parts of it can act (when taking very specific behavior) as if they had negative mass.

      The headline and summary are the equivalent of saying "man travels through space safely without spacesuit on!", without mentioning he's inside a spaceship.

      • Re:Wow (Score:5, Interesting)

        by TeknoHog ( 164938 ) on Thursday April 20, 2017 @11:01AM (#54270321) Homepage Journal
        Yup, this sounds just like the reports of negative temperature. There, the distribution of particles was governed by a term like B*c*T, where B = external magnetic field strength and T = temperature. The field was suddenly reversed, but the particles didn't change their configuration immediately. The system looked like B*c*T for a while, but the field was now -B. So if you wrote the term as (-B)*c*(-T), it looked like the long-term equilibrium state at field -B and temperature -T. Of course, the system wasn't at equilibrium, so the math didn't really apply.
        • Re:Wow (Score:5, Informative)

          by Baloroth ( 2370816 ) on Thursday April 20, 2017 @01:27PM (#54271491)

          Negative temperatures are actually a pretty well-defined and real thing, but that's just because of the way we define "temperature" in thermodynamics, which is not always exactly the same as what we think of as temperature in everyday life. The short explanation is that temperature (T) is the rate of change of energy (E) with respect to entropy (S) (in math: T=dE/dS). If I have a system that is bounded from above in energy (i.e. a maximum energy the system can reach), I can get negative temperatures. Simple example: let's say I have a system of particles, each of which can be in two states, a state with more energy, and a state with less energy. The entropy is the number of different states the *entire* system can be in, so if the system is in a minimum energy state (i.e. every particle is in the lower energy state) I have a minimum entropy system (every particle in the same state means I only have 1 possible state for the entire system). Likewise, in a *maximum* energy state, all the particles are also in the same state (the higher energy state), so I also have minimum entropy. Maximum entropy occurs when the energy is right in the middle between these: half the particles are in the higher energy state, half are in the lower energy state, so the entire system has the most possible configurations. So, if the system is in that state, and I add a bit of energy to it, I decrease the entropy (as there are fewer particles in the lower energy state and therefore fewer possible configurations). That means dE/dS is negative (since S goes down, so dS is negative, while dE is positive), so you get negative temperature.

          In every day life, systems typically aren't bound from above, and also any particles in higher energy states like that will fall into lower energy states and release energy (this is exactly how a laser works, incidentally), so you only get negative temperature in carefully constructed systems.

          The negative mass term in this case, however, is a negative effective mass (not a real mass) term that occurs in a group velocity (which is not the real velocity of particles in the system) dispersion relationship. Not to say the results aren't interesting: they are, they're just... well, not really negative mass at all.

      • They did not observe "negative mass". They created a system wherein, under specific circumstances, part of the system behaved as if it mathematically had negative mass.

        Man, you are gonna be angry when you find out about negative temperature [youtube.com].

      • That's because the headline is some of the worst sensationalistic tabloid journalism level garbage I've ever read. They did not observe "negative mass". They created a system wherein, under specific circumstances, part of the system behaved as if it mathematically had negative mass.

        Thanks for the clarification. While they may not have created actual negative mass, it's good to know that they've created something that the public will confuse for the real thing, since if there's one question I love hearing over and over again, it's "When will we have Jetsons-style flying cars and hoverboards?".

      • The headline and summary are the equivalent of saying "man travels through space safely without spacesuit on!", without mentioning he's inside a spaceship.

        Man travels through space safely without spacesuit on! Fetched another beer from the kitchen....

  • Nice trick (Score:5, Informative)

    by ByteSlicer ( 735276 ) on Thursday April 20, 2017 @09:13AM (#54269405)

    But if it truly had a negative inertial mass, it should spontaneously move upwards, because there already is a force pulling it downwards (gravity).

    As it is, it just behaves like a negative inertial mass under certain strict conditions, which is somewhat interesting, but not a ground breaking discovery. That said, go science!

    • by Anonymous Coward

      Not quite. When one mass is negative, the attractive force result from gravity between two objects is negative, but a negative force applied to a negative mass results in a positive displacement. So it will still fall toward the earth, but in the process it provides a minuscule push on the earth away from itself.

      It is mathematically valid for two equal and opposite masses in an otherwise featureless infinite vacuum to accelerate with no additional energy added to the system. The positive mass would be fa

      • While you are technically correct (which is the best kind of correct), there still would be a measurable upward component, meaning the condensate would accelerate less when released from the laser trap.
        This was not what they found in the experiment, instead they found differences in expansion rates of different regions of the condensate, perpendicular to the direction of gravitational acceleration, an effect caused by a different external force.

  • by Baron_Yam ( 643147 ) on Thursday April 20, 2017 @09:14AM (#54269411)

    It's analogous to negative mass (if such a thing could actually exist) in that some of the observed behaviours map to those calculated for negative masses.

    This is an important difference, much like when we saw pop science reporting on 'table top black holes'. They weren't actually black holes.

  • ... and sell it as a weight-loss drink.
  • So, would this be considered antimatter?
    • Re: (Score:2, Insightful)

      by Anonymous Coward

      Anti-matter has positive mass and inertia. The Higgs particle is its own anti-particle.

  • A long time ago, I recall reading about the theory of negative mass, and if I recall correctly, it should allow for the creation of pseudo-reactionless drives. Technically, it isn't reactionless because it's obeying all the laws of reaction drives, it's just that f=ma gets weird when m0.

    So if you have a ship that contains equal parts mass and negative mass, its "total mass" will be 0, and any force applied to it will instantly accelerate it to lightspeed.

    It's always been one of those things I assumed would

    • by Tighe_L ( 642122 )
      I think that it would rip itself apart as soon a force where applied.
      • That's what I thought too. Maybe this could be mitigated if your equal parts mass and anti-mass were evenly distributed throughout every material in the ship.
    • There's a better version. Take a lump of something (A) with m = -1 and chuck it at a lump of something (B) with m = 1. B is attracting A due to gravity, but A is repelling B due to gravity - and you have perpetual motion because B keeps being pushed away from A as fast as A falls toward it.

      But personally my bet is that they would simple bounce around a bit until they reach a point where the repellent effect of B and the attractive effect of A cancel out and then stop in a dead balanced state there - not al

  • One of the fundamental "flaws" in Warp drives is need for exotic states of matter like negative mass. One step closer to FTL travel! Only 2000 years more of technology development needed!
    • And this is why I hate this article... THEY HAVE CREATED NEGATIVE MASS. They've created something that behaves sort of like you'd expect negative mass to behave if it were possible.

      Actual negative mass is not possible, which is just one of many reasons a warp drive is not possible (which I personally find disappointing, but it's still true).

      • Oh, FFS. Shouting in all caps and all and I forget the critical 'NOT'.

        They have NOT created negative mass.

    • by mark-t ( 151149 )
      No. Only a little less than half of that
  • by Anonymous Coward
    Not really negative mass. We like often to model some behavior in the "effective" counter behavior in case of negative. E.g. model electron holes.
  • by frovingslosh ( 582462 ) on Thursday April 20, 2017 @10:03AM (#54269817)
    Take a group of atoms, remove heat, and suddenly they change from having positive mass to negative mass. Children, what have we been telling you about critical thinking and not buying into obvious bullshit?
  • by PPH ( 736903 ) on Thursday April 20, 2017 @10:14AM (#54269919)

    ... the negative mass fluid was lost when a scientist set the beaker on a table and it spilled out all over the ceiling.

  • Interesting. So in theory you could create thrust inside a sealed container? Sounds like troll physics to me.

    • So in theory you could create thrust inside a sealed container? Sounds like troll physics to me.

      You wuldn't believe how many people here seem to think the EM drive works.

  • I bet negative mass engines are just around the corner too... ;-)

    • Cool, if you had one tank of fuel with positive mass, and one with negative mass, you could decelerate by just switching fuel!

  • I gots lots of negative mass experience.... *&%@!##*11

  • Like described in this /. story back in 2014...

  • by caffeinated_bunsen ( 179721 ) on Thursday April 20, 2017 @03:23PM (#54272231)
    No They Didn't, You Bloody Idiots

    Reporters at the BBC discovered today that reporting on scientific experiments without basic background knowledge can result in wildly inaccurate headlines. The reporters' usual technique of absentmindedly skimming someone else's account of an event, copying a few juicy-sounding words, and filling in the rest with fluff turned out to completely misrepresent the actual science.

    When asked for comment, a BBC spokesman said, "Piss off, egghead. You clicked on it, didn't you? Mission fucking accomplished on our end."
  • Okay, so we know by now that this isn't actually negative mass.

    Would any physicists here care to chime in on whether this particular experiment is any different from the dozens of others that have resulted in Bose Einstein Condensates and, if so, what sets this one apart?

  • Pfft. Negative Catholics have been observing Negative Mass for centuries.

    (Well, to be fair, most are non-observant and only show up for Negative Easter.)

  • Next: Phlogiston and magnetic monopole phenomena discovered!

  • Sadly, I had a girlfriend like that.

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