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Physicists Observe 'Negative Mass' (bbc.com)

Posted by msmash on from the breakthrough dept.

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.

19 of 117 comments (clear)

  1. Last Post by Big+Hairy+Ian · · Score: 4, Funny

    I'll get my coat

    --

    Build a Man a Fire, and He'll Be Warm for a Day. Set a Man on Fire, and He'll Be Warm for the Rest of His Life.

    1. Re:Last Post by Sir+Holo · · Score: 2

      In anti-matter universe, negative score predict you.

      Antimatter has mass. In fact, a given antiparticle has the same mass as its counterpart particle. Like, say, an antiproton and a proton.

  2. Wow by Headw1nd · · Score: 2

    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.

    1. Re:Wow by Baloroth · · Score: 5, Interesting

      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.

      --
      "None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
    2. Re:Wow by TeknoHog · · Score: 5, Interesting

      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.

      --
      Escher was the first MC and Giger invented the HR department.
    3. Re:Wow by Baloroth · · Score: 4, Informative

      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.

      --
      "None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
    4. Re:Wow by Areyoukiddingme · · Score: 2

      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....

  3. Nice trick by ByteSlicer · · Score: 5, Informative

    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!

    1. Re: Nice trick by Khashishi · · Score: 2

      In general relativity, gravity is a curvature of spacetime. It does not produce any proper acceleration of a test object, so it can be regarded as a fictitious force, like centrifugal force. In other words, we can choose coordinates in which there is no acceleration in the test object.

      Of course, this is just one way to look at it. In other physical contexts, we can view gravity as a force. It's not wrong to do so, since the meaning is context sensitive.

    2. Re:Nice trick by jellomizer · · Score: 2

      Still we are taught that force of gravity is in relationship of the mass. I would like to find out if Anti-Mass produces anti-gravity. or it may not, but checking the gravitation observed force may bring light into how gravity works.

      --
      If something is so important that you feel the need to post it on the internet... It probably isn't that important.
    3. Re:Nice trick by ByteSlicer · · Score: 2

      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.

  4. It's not actually negative mass by Baron_Yam · · Score: 5, Informative

    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.

  5. Re:Antimatter? by Anonymous Coward · · Score: 2, Insightful

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

  6. yea, right by frovingslosh · · Score: 2

    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?

    --
    I'm an American. I love this country and the freedoms that we used to have.
  7. Unfortunately ... by PPH · · Score: 2

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

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    Have gnu, will travel.
    1. Re:Unfortunately ... by budgenator · · Score: 2

      If I had points, you'd get +1Funny

      --
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  8. Re:wow..? by serviscope_minor · · Score: 2

    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.

    --
    SJW n. One who posts facts.
  9. Not new? by goombah99 · · Score: 2

    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 (supposedly) magnetic monopoles but if you stack dipoles end to end then one can get two very well separated poles that behave as though they were independent monopoles.

    Maybe I'm wrong, but Ive seen this negative mass explanation before so I'm guessing this is similar, not a new effect.

    --
    Some drink at the fountain of knowledge. Others just gargle.
  10. Let me correct that headline by caffeinated_bunsen · · Score: 4, Insightful

    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."

    --

    Bugrit! Millenium hand and shrimp!