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.
Last Post (Score:5, Funny)
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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.
Not new? (Score:3)
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
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no it's a ficitonal mass.
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Pics or it won't happen!
Wow (Score:3)
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Re:Wow (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.
Re:Wow (Score:5, Interesting)
Re:Wow (Score:5, 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.
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Thanks!
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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].
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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?".
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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)
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!
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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
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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.
Re: Nice trick (Score:1)
In what sense? Gravity certainly applies a force to objects. In fact it always does, we don't have the ability to prevent it. So whether gravity is waves, or particles, or both, or just a change in the shape of space-time, the end result is it applies a force.
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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.
We know how Gravity behaves but not what is is. (Score:1)
Isn't it actually a case where gravity behaves like a curvature of space and time? Seems like we can describe the effects of gravity and make analogies of those effects, but do we really have any idea how it actually causes those effects?
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Different physicists will give you different answers on this one. Some will say what you say: that all this spacial curvature stuff is just a model of how the force works, but in reality, space is flat. Others will so no, flat spacetime requires additional axioms to construct (angles of triangles add to 180, or straight lines remain parallel forever), so curved spacetime is by definition more natural - and besides, these axioms make predictions about reality (angles in triangles add to 180, parallel lines
About gravity being the curvature (Score:2)
I've always viewed gravity as being the mass interacting force that warps space-time, ie: the curvature is an effect of gravity rather than gravity itself.
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You feel a "force" because you are living in an accelerated frame of reference. That acceleration is being provided by the ground, which is exerting just enough upwards force to keep you accelerating at about 10m/s^2 in that direction. If you want a non-accelerated frame of reference try a satellite or free-fall and note the complete absense of any "force".
Another viewpoint: the really weird thing about gravity as a force is that the "force" applied is proportional to the the inertial mass of the object i
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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.
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IMO.. If you think of gravity as a warp in space-time and strong positive gravity is represented the shape of space-time around a black hole, then a white hole would have warped space-time around it that represents "negative gravity". I think.
Maybe the big bang is a white hole location in space-time. So you can imagine that negative gravity is everywhere you look into the far distance just beyond what you can see.
It's not actually negative mass (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.
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TFA doesn't have enough detail to really say what was observed. From the minimal description, I can think of a few reason you might see an effect like this. If they are releasing a liquid cooled to near absolute zero from a laser trap I would imagine they are not just tossing it on the floor for safety sake so pressure in what ever they are using to contain it could cause a similar effect when it rapidly expands.
Bottle it... (Score:2)
Antimatter? (Score:2)
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Anti-matter has positive mass and inertia. The Higgs particle is its own anti-particle.
I remember reading about this in theory... (Score:2)
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
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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
Needed for Warp Drive (Score:2)
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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).
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Oh, FFS. Shouting in all caps and all and I forget the critical 'NOT'.
They have NOT created negative mass.
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negative *effective* mass (Score:1)
yea, right (Score:3)
Unfortunately ... (Score:3)
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If I had points, you'd get +1Funny
wow..? (Score:1)
Interesting. So in theory you could create thrust inside a sealed container? Sounds like troll physics to me.
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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.
Hmmm... (Score:1)
I bet negative mass engines are just around the corner too... ;-)
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Cool, if you had one tank of fuel with positive mass, and one with negative mass, you could decelerate by just switching fuel!
Observation vs. experience.. (Score:2)
I gots lots of negative mass experience.... *&%@!##*11
Sounds more like a tractor beam to me... (Score:2)
Like described in this /. story back in 2014...
Let me correct that headline (Score:5, Insightful)
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."
Just another BEC experiment? (Score:2)
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?
A bit late to the party, eh? (Score:1)
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.)
Slashdotters fall for this one weird trick (Score:1)
Next: Phlogiston and magnetic monopole phenomena discovered!
Sadly (Score:1)
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If pushing it causes it to want to move towards you, then it is going to want to occupy the same space as your hand. But since two objects cannot both exist in the same place at the same time, it should move no where. Thus, we have the immovable object.
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You haven't met many assistant professors, have you?
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Acceleration is a change in velocity. Velocity is a vector, comprising speed and direction. Change either of those and you're accelerating.
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Falling towards the Earth is a form of accelerating towards the Earth.
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My initial reaction was that AC couldn't be right; a satellite and a ray of light starting out in the same direction would diverge in space, and they couldn't both be straight lines. But that was my misunderstanding. They would not both follow straight lines in *space*, but they would in *space-time*. There's a useful explanation here: http://curious.astro.cornell.e... [cornell.edu]
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if it was not accelerating then it would move in a straight line. That it changes direction should be a clue.
Angular velocity is not velocity, it's more like a metaphor.
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