Temperature in a gas can reach below absolute zero thanks to a quirk of quantum physics.
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From Nature magazine
It may sound less likely than hell freezing over, but physicists have created an atomic gas with a sub-absolute-zero temperature for the first time. Their technique opens the door to generating negative-Kelvin materials and new quantum devices, and it could even help to solve a cosmological mystery.
Lord Kelvin defined the absolute temperature scale in the mid-1800s in such a way that nothing could be colder than absolute zero. Physicists later realized that the absolute temperature of a gas is related to the average energy of its particles. Absolute zero corresponds to the theoretical state in which particles have no energy at all, and higher temperatures correspond to higher average energies.
However, by the 1950s, physicists working with more exotic systems began to realise that this isn't always true: Technically, you read off the temperature of a system from a graph that plots the probabilities of its particles being found with certain energies. Normally, most particles have average or near-average energies, with only a few particles zipping around at higher energies. In theory, if the situation is reversed, with more particles having higher, rather than lower, energies, the plot would flip over and the sign of the temperature would change from a positive to a negative absolute temperature, explains Ulrich Schneider, a physicist at the Ludwig Maximilian University in Munich, Germany.
Peaks and valleys
Schneider and his colleagues reached such sub-absolute-zero temperatures with an ultracold quantum gas made up of potassium atoms. Using lasers and magnetic fields, they kept the individual atoms in a lattice arrangement. At positive temperatures, the atoms repel, making the configuration stable. The team then quickly adjusted the magnetic fields, causing the atoms to attract rather than repel each other. “This suddenly shifts the atoms from their most stable, lowest-energy state to the highest possible energy state, before they can react,” says Schneider. “It’s like walking through a valley, then instantly finding yourself on the mountain peak.”
At positive temperatures, such a reversal would be unstable and the atoms would collapse inwards. But the team also adjusted the trapping laser field to make it more energetically favourable for the atoms to stick in their positions. This result, described today in Science, marks the gas’s transition from just above absolute zero to a few billionths of a Kelvin below absolute zero.
Wolfgang Ketterle, a physicist and Nobel laureate at the Massachusetts Institute of Technology in Cambridge, who has previously demonstrated negative absolute temperatures in a magnetic system, calls the latest work an “experimental tour de force”. Exotic high-energy states that are hard to generate in the laboratory at positive temperatures become stable at negative absolute temperatures — “as though you can stand a pyramid on its head and not worry about it toppling over,” he notes — and so such techniques can allow these states to be studied in detail. “This may be a way to create new forms of matter in the laboratory,” Ketterle adds.
If built, such systems would behave in strange ways, says Achim Rosch, a theoretical physicist at the University of Cologne in Germany, who proposed the technique used by Schneider and his team. For instance, Rosch and his colleagues have calculated that whereas clouds of atoms would normally be pulled downwards by gravity, if part of the cloud is at a negative absolute temperature, some atoms will move upwards, apparently defying gravity.
Another peculiarity of the sub-absolute-zero gas is that it mimics 'dark energy', the mysterious force that pushes the Universe to expand at an ever-faster rate against the inward pull of gravity. Schneider notes that the attractive atoms in the gas produced by the team also want to collapse inwards, but do not because the negative absolute temperature stabilises them. “It’s interesting that this weird feature pops up in the Universe and also in the lab,” he says. “This may be something that cosmologists should look at more closely.”
This article is reproduced with permission from the magazine Nature. The article was first published on January 3, 2012.
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65 Comments
Add CommentThis 'sub-absolute-zero' seems a semantics trick to me. This is a superheated gas with minimum entropy. They use the low-entropy part of it to refer to absolute zero, but how is it BELOW zero Kelvin, when its particles have such high energy?
Reply | Report Abuse | Link to thisDang, I'm confused =P
Even if it's not a semantic 'trick' what would happen to such exotic material developed in the lab when brought up to room temperature?
Reply | Report Abuse | Link to thisIt's not a semantic trick. As explained in the article, the original, 19th Century definition of 'absolute' zero did not take quantum mechanics into account, because it wasn't described yet.
Reply | Report Abuse | Link to thisI find the possible connection to dark energy intriguing. Perhaps I'm jumping the gun, but are there any aspects to this laboratory energy-inversion technique that would inherently mask the state of the sub-absolute system from observation - say, if it were found out in the far reaches of space?
It does seem like a trick but perhaps it is similar to the effect of an aerosol can, such as the ones with air used to clean dust from a computer. If you get one, hold the trigger down, the air coming out of the can is high energy but the can itself gets cold in your hand because of all the energy effectively leaving instantly with the air.
Reply | Report Abuse | Link to thisThe scientist used the theory of moving from a valley to a mountaintop instantly. Sure the particles at the top of the mountain have a lot of energy, having just moved there but the space the particles left in the valley is what the scientist is claiming has the -Kelvin temperature and presumably the few particles left in the space also have the same -Kelvin temperature.
Still your point is valid, it seems to all be statistical math more than actually measuring the below absolute zero temperature. At least with the aerosol can, you can feel the cold in your hand.
Reply | Report Abuse | Link to this'Sub-zero phenomena "mimics" dark energy'
I don't think so.
Dark energy is associated with accelerated expansion.
The non-collapse of the excited sub-zero atoms is more a maintenance a static configuration.
But hey, in the postmodern pseudo-science of unobserved strings, sparticles, quarks and wimps, I guess it's close enough in that they both resist collapse (albeit for very different interactions).
But then again so does the hot air in a balloon. So does hot air "mimic" dark energy?
Sure! With pseudo-science anything goes. And sells nicely to the credulous.
Robert L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Fractal Cosmology
Sounds to me like they simply need to redefine the Kelvin scale to take quantum physics into account so that Absolute Zero really is absolute. Because, if I'm reading this correctly, they have not really entered some kind of "inverse temperature" domain with no limit, but simply found incrementally smaller values due to the weirdness involved in QM. That means they should just move the observational definition of zero.
Reply | Report Abuse | Link to thisI don't understand your need to belittle points made in various articles. If you have a disagreement with them, why not just state it in a professional manner? I've seen you carry on conversations in a respectable manner, but when you respond like this, it makes people less inclined to listen to anything you have to say.
Reply | Report Abuse | Link to thisWhat in particular makes you disinclined to believe this? What in the paper(s) do you find fault with, and do you have an alternative explanation for it?
There is undoubtedly some real science of interest being done by Mr. Schneider's group but Mr. Oldershaw is detecting hype in the suggestion that stability of an ultracold system is somehow related to dark energy, as do I. The suspicion is that "dark energy" is really being mentioned only because it is currently a fashionable topic -- a sexier mystery than a tiny decent below absolute zero.
Reply | Report Abuse | Link to thisAs a car mechanic I have to assume that your opinions have been statistically validated however, I do believe that absolute zero varies in time-space and, also has different values in different universes. Technically, it should go down to an infinite value in a infinite size universe void of any mass/radiation. However, I need to go back and work on a customers auto transmission for now. Thank you for sharing your interesting opinions.
Reply | Report Abuse | Link to thisHypothetically, suppose a closed system contains only one atom of any gas say potassium in some experiment as indicated in the Article. In such situation, is there any relevance of absolute zero or sub absolute zero? At sub absolute temp, there shall be reversal of energy. Does reversal of energy carries any meaning on physical paradigm?
Reply | Report Abuse | Link to thisNothing can be colder than absolute zero, another law that has been shattered. What they are going to find out is that they are tapping into the Higgs bosonic field which also is the effect we call dark matter. Remember photons are bosons tooooooo.....
Reply | Report Abuse | Link to thisSee "The Indivisible Atom - The Theory of Everything," here: http://shineinnovations.com/101012.html
Why don't we just re-define the Kelvin scale and what Absolute Zero is and problem solved.
Reply | Report Abuse | Link to this
Reply | Report Abuse | Link to thisThank you for your supporting comment, Adam.
I believe that there has been far too much hype coming from theoretical physics over the last few decades. String theory has been the "only game in town" for 44 years solely on the basis of unjustified hype. Not a single scientific prediction.
Scientists who care about the integrity of science feel a responsibility to identify and discourage the hype.
This does not make them popular, but such individuals are definitely not hoping for the Miss Congeniality Prize.
While this research is fascinating, the conclusions of both the paper and this article are incorrect.
Reply | Report Abuse | Link to this(1) The slope of the energy population distribution function can be used to determine the temperature only if the system is in equilibrium.
(2) This system is not in equilibrium. Therefore, you can't use the slope of the energy distribution function to determine the temperature.
(3) For systems that are not in equilibrium, you must go back to a more basic definition of temperature.
Temperature is the ratio of the total energy to the total entropy. Therefore, temperature can only be negative if either the total energy or the total entropy is negative. (And not both at the same time)
(4) But the total energy and the total entropy of a system are both positive quantities, which is why temperature is always positive.
(5) Therefore, the conclusions of the paper are incorrect. The authors are studying a really interesting non-equilibrium phenomena, but they are not studying a system with negative temperature...just a system with a negative slope in the energy population distribution function.
(6) There are lots of non-equilibrium systems with local negative slopes in the energy population distribution function. A simple example is a fluorescent light bulb...whose electron energy distribution function (EEDF) has bumps and peaks rather than a perfectly straight line. The temperature of a fluorescent light bulb is not negative. It's a non-equilibrium system, and so you've can't define the temperature to be the slope of the EEDF. You have to use the more basic definition given above (Temp = Total Energy / Total Entropy) You can only use the derivative of the EEDF if the system is in equilibrium.
(7) Making a connection between EDF's with negative slopes and "dark energy" is silly. Dark energy is related to the expansion of the universe. Making a connection between the two topics is like saying that understanding the EEDF of fluorescent light bulbs can provide insight into dark energy. I can think of no connection between EDF's with negative slopes and the expansion of the universe.
If what is said about the reaction of this material to gravity is true, that up is down etc, then perhaps the acceleration of expansion theory of dark energy does in fact apply to particles at negative temperatures and the statement that this is much like dark energy is in fact not that far off.
Reply | Report Abuse | Link to thisPretty much my logic, thank you.
Reply | Report Abuse | Link to thisSo, if I were to hand you a container with this gas, would it burn or freeze your hand? Or if I spray it on you? Seems to me the high energy in the particles would burn - so, how is this ultra-cold?
If they refer to the 'empty valley' left by the particles, it would qualify as vacuum of sorts, right? What temperature is this vaccum, void of anything where you can measure energy/entropy? And in any case, how is it below 0°K?
Sorry, I still fail to see the 'negative scale' here.
And, if there's someone who knows his pseudoscience, it's Dr. "Oooh, it's look fractals all the way down".
Reply | Report Abuse | Link to thisYou (and presumably Mr. Oldershaw) and I read the ending differently, then. I read it as saying, "Something interesting is happening here and if it actually does react to gravity the way we think, then cosmologists might be interested in investigating it because they're investigating something that seems to react to gravity in a similar way."
Reply | Report Abuse | Link to thisVery nice post, which I have downloaded and am studying.
Reply | Report Abuse | Link to thisSo far your arguments look quite convincing.
A voice of reason amid the posers.
this is another trash experiment published on nature
Reply | Report Abuse | Link to thisyou do not need to do this kind of experiments
the physics is well understood
you do not need to waste money or time on such seemingly interesting or fancy experiments
negative temperature is not a big deal as its name suggests.
"Negative absolute temperatures" have been known for many years. Paradoxically, they are "hotter" than positive temperatures. In spin systems (say, two-state systems) once one gets beyond equal populations in the two states with more in the higher energy state (population inversion) then the temperature (as a parameter in the Boltzmann distribution) becomes negative. In thermodynamic terms, T = dE/dS (V constant) is <0 because as the energy increases toward population inversion, the entropy decreases.
Reply | Report Abuse | Link to thisIt sounds to me like a word game in order to make an inflated claim. Maybe I don't properly understand the experiment. But I don't see where they actually went below absolute zero or how they had a negative temperature or even how this resembles dark energy. It just looks like they are playing games with the definition of absolute zero. It looks like all they did was reach a very cold temperature slightly above absolute zero.
Reply | Report Abuse | Link to thisAlso, I thought absolute zero is the absence of all energy and that because of the uncertainty principle you could never actually reach absolute zero.
Re-defining absolute zero as a statisitical thing still doesn't mean you reached absolute zero, let alone a negative temperature, whatever that means. As the old joke goes about the five legged dog, calling the tail a leg doesn't change the fact that the dog still only has four legs.
If temperature of a collection of atoms is related to the relative speeds of the atoms within the group, what then is the temperature of a single atom held motionless in a trap?
Reply | Report Abuse | Link to thisClearly the abstract concept of “Absolute” zero is obsolete and our beloved Laws of Thermal Dynamics is incomplete. I doubt we need to get rid of the Kelvin System just yet, but using the term absolute zero is antiquated at this point. What have to be redefined is just what “Temperature” means and what energy means.
Reply | Report Abuse | Link to thisIn high school texts books the definition means simply the motion of atoms in relationship to each other, so if any of the trillion or so atoms are moving in a dissonant fashion to the rest of them, then you have not achieved absolute zero. However what this article seems to be implying is that energy inside of the atoms should also be included with in the mean temperature. If that is the case, then Kelvin is measured by the motion of atoms + the energy state of the atoms themselves.
So this whole article isn’t just about “Semantics”, it is more about the failure of the original definition. In my perspective this is a much bigger aspect to this whole story then quantum properties of potassium gas at ultra-cold temperatures. These little sematic gaps in physics are reasons we do not have a Grand Unified Theory yet.
I am an independent cosmologist, living in Almere, the Netherlands. I theoretically predict the reverse gravitational effect in a range above and below the absolute zero point. It is described in my 'set of equations' in one of my 'papers' hosted in the Vixra-archive' and belonging to the framework of a new cosmology, the 'Double Torus hypothesis' of dark energy and dark matter. A (new) formula of dark energy is presented there, consisting of the lowest Newton gravity-force in product with a dark matter force (+ and -). Visit my website (www.darkfieldnavigator.com .). I challenge Scientific American-journalists to write an article about that. reactions to dan.visser@planet.nl
Reply | Report Abuse | Link to thisIf you can really get to absolute zero, where there is no energy of particles, do you have anything at all.
Reply | Report Abuse | Link to thisAlthough the potassium atoms have been immobilized in a magnetic/laser lattice, have the protons, neutrons, and electrons become immobilized?
You still have atomic structure, which is maintained by the energy of the atomic structure, protons/neutrons/electrons, presumably made of quarks and other sub-proton and sub-neutron particles.
Perhaps there is a clue to dark energy/matter here.
Does dark energy have any atomic or nuclear structure.
Is is some form of matter that doesn't have enough energy to generate quarks and other subatomic particles?
I don't mean to degrade the experiment, in fact it is quite incredible, an incredible achievement, and may be a harbinger of new frontiers, studying subatomic particles at sub-kelvin temperatures, and sub-atomic energies.
Robert L. Oldershaw, you are my hero. Your common sense approach to physics is both refreshing and delightful.
Reply | Report Abuse | Link to thisSmall minded people often feel the need to decry theory simply because it has yet to be observed experimentally. There was a time when many physicists considered Einstein's theories of special and general relativity in much the same fashion, this is not to mention his use of Planck's quantum theory to explain the photoelectric effect. Even Einstein simply could not accept the uncertainty principle or quantum entanglement.
Reply | Report Abuse | Link to thisAs you may be aware, all of these have been proven to be fact. This does not mean that string theory will be as well but I'll bet long odds on quarks...
Paramadman
This might be meaningful if "commonsense" had any place in quantum mechanics...
Reply | Report Abuse | Link to thisParamadman
I think we're better off trusting Kelvin; sounds to me like some people want something special they can't have, so they're rationalizing.
Reply | Report Abuse | Link to this(In connection to what LoPan say)
Reply | Report Abuse | Link to thisI immediately reached the same conclusion.
And it may have nothing to do with QM.
If we reached the zero point working with ideal gas model we may have simply made an error and now we are moving the zero a little downward.
But who knows we need to study QM to fully understand what they say.
I hope nobody gets offended because we are discussing the subject matter without a full understanding of QM.
But I think it is valid to do so in this forum.
We are interested in science. Seriously.
It has never occurred to me about negative Kelvin temperatures.
If we reach a point in which there is no movement at all,no electrons moving around the atoms, nothing, then we should reach real absolute zero.
And we need no QM to reach a conclusion like that.
I just discover the formula for OneWave. OneWave is related to the Big Bang, i believe the empty space is not empty and there are plenty extremely weak electromagnetic waves exist in it. Before explaine OneWave, let look at an atom, an atom could be divided into proton, neutron and electron. These sub-particle could be further divided into quarks like bosons and Fermions, but how if we further and further divide the Fermions and bosons? According to classical physics and pratical physics, fermions and bosons are too hard to be further divided again, but i believe fermions and bosons can be further and further divided into the same electromagnetic waveforms, which energy level is extremely weak and just not yet to equal to zero and i call it OneWave.
Reply | Report Abuse | Link to thisAt the present, physicists try their best to combine the theory of general relativity with theory of quantum mechanics to complete the uncompleted quantum physics but they face one major problem i.e. they failed to unify the electromagnetic force with gravity force. i believe OneWave will be the vital key to solve the problem. Hawking had explaine the universe was born after a Big Bang and assumed and calculate a great matter in a very small space but nobody had explaine where is the great matter came from. Hawking had said that there is a rule underlying all the laws of physics and governs the universe, the rule is very simple but not yet known by human beings.....
Now i try to introduce the Theory Of OneWave, before the event of Big Bang, the empty space had no any particles, however, the empty space is fully filled with a kind of extremely weak electromagnetic waveforms which enegy level is just not yet zero. To create the universe, God have to lead a great number of OneWaves to a single pointed space (He just behave like a super great laser). Then, let the below formula to explaine the creation:
NWo
------- = HsM
Sp
where N ------------> infinity
Wo -----------------------------------> 0
Sp ----------------> 0
N is the number of waveforms which is approach to infinity
Wo is the energy level of OneWave which is extremely close to zero and just not yet zero
Sp is the pointed space which is approach to zero
M is the matter produced and is depend on the number of OneWaves. M = f (NWo)
Hs is a variable and is depend on 1 / Sp, i.e. the smaller the value of Sp, the greater the value of Hs. Hs = g (1/Sp)
It looks like you are opening the door to us to unknown territory, weird worlds.
Reply | Report Abuse | Link to thisBut it is a territory worth exploring of course.
There is still much to be done.
Sometimes it seems (and I think I have mention this before)we have got to get back to square one.
It is understandable it is a complex Universe.
It seems we are just scratching the surface.
Yes, it seems like we may be beginning to understand dark matter.
And diverting from the main course, if I may say, I have always think something like a "negative gravitation" could be created so we can be expelled by a gravitational field instead of been attracted. I say this entirely on intuition.
Read ether=gravity=dark energy theory of gravitoethertons. Negative entropy is possible and a transformation to antimatter is key to the situation. Read balloon inside balloon theory of matter and antimatter on opposite entropy path producing gravitoethertons at common boundary by annihilation and injected into both the universes as graviton and anti graviton and recently we have found these force carriers as two HIGGS BOSONS AT CERN. All these observations can be explained from a paper published in ASTRONOMY.NET in year 2002 --paper is Misjudgement by Newton and Einstein. The problem is entropy we have not properly understood.
Reply | Report Abuse | Link to thisI just got done with a class in thermal, so I figured I'd throw my hat into the ring to explain this. What's going on is that the technical definition of temperature is the reciprocal of the derivative of a system's entropy with respect to the system's energy. Entropy is defined as Boltzmann's Constant times the log of the number of states available to the system. This number is finite because of quantum mechanics. So, for a positive temperature, you need a system whose entropy increases with energy. This is the case with many systems (atomic energy levels, quantum oscillators, particles in 3-D boxes, etc.) One of the consequences of the 3-D particle in a box is you get the familiar relationship between the kinetic energy and temperature of a gas. To get a negative temperature, you need a system whose entropy decreases as the system's energy increases. I think the simplest example is a laser. In a laser, as you increase the lasing medium's internal energy (done using an electric field, more lasers, whatever) you force more atoms into an excited state. The energy of the excited states is bounded by the energy of whatever is exciting the medium. For an example of this, see: http://en.wikipedia.org/wiki/Photoelectric_effect So, as more atoms are excited, the high energy states start to fill up and you'll reach a point where adding energy decreases the number of avaiable states, thus decreasing entropy, thus negative temperature. To make a (poor/forced) analogy between the laser and what these folks did, the lattice energy is like the excited states and the lasers are like the exciter of the lasing medium. See also http://en.wikipedia.org/wiki/Negative_temperature
Reply | Report Abuse | Link to thisI thought cold was a concept that measured the absence of heat...some, more, or in this case, even more. Doesn't this just redefine absolute cold?
Reply | Report Abuse | Link to thisExactly what I wanted to suggest, tiny differences do not suggest that there is no absolute zero. They should rather just redefine the limit. Thanks for your contribution, I enjoyed it immensely
Reply | Report Abuse | Link to thisthe connection with dark energy is based on the rigidity of the potassium atoms in the artificial laser lattice, so like the expanding universe not collapsing on its own gravity, the atoms stay at their boundary. Some people don't seem to be understanding this from the article. Although it seems an extremely distant relation from the scientists. Maybe they should consider their results in a different way.
Reply | Report Abuse | Link to thisThis is a semantic exercise and I expect that the claims will be overturned in a year. The connection with dark energy is just another over reach among the dark energy community to try to bolster one side of the argument.
Reply | Report Abuse | Link to thisThere are some very insightful comments here (including especially yours and "hairy_cheese" among others, as well as some of those posted to the linked "Nature" article (ignoring even more silliness found there).
Reply | Report Abuse | Link to thisI haven't attended any physics classes, but I think the analogy between collapsing particles and classical gravitation as an 'attractive force' are really a stretch. IMO, the repulsion and attraction of charged particles in a magnetic field does not adequately represent any actual physical effects of gravitation.
However, if it's considered that general relativity accurately describes the effects of gravitation as localized distortions of dimensional geometry using an abstract system of spacetime coordinates, it can be inferred that they must physically represent some characteristic property of spacetime - perhaps vacuum energy density distributions (not to be confused with any material ether).
In this case the interaction between universal expansion and local contraction of mass-energy temporally redistributes mass-energy, producing the observed very large scale material structure that includes enormous regions devoid of mass-energy (B.T.See - even so long after the initial condensation of matter from vacuum energy).
The voided regions might be considered 'absolutely' cold as a result of their being no matter to reflect the effects of energy, yet continuing to globally expand at potentially increasing rates (being unaffected by gravity) as relative vacuum energy density increases. It seems the flow of detectable thermal energy should generally be directed from the voids to the material structures...
This, at least I think, is a process that might in general better represent the physical effect of apparently universally accelerating spacetime expansion than some peculiar unidentified 'dark energy'...
Okay what the problem with grasping this article is that low temperature does not necessarily mean low levels of energy. The best example of this would be weather on the planet Neptune where the atmosphere’s temperature is 55 Kelvin while the wind speed relative to its axis can reach 1,200 miles per hour. One can imagine that if someone was stationary (relative to the axis of the planet) in that environment, the last thing they would describe is a low level of energy.
Reply | Report Abuse | Link to thisMy complaint here is that there are various energy states that are being combined here for sematic and mathematical convenience that fit nicely at room temperature, but break down once we reach the quantum levels using the Kelvin scale.
So this would be my guess at what is happening here;
Reply | Report Abuse | Link to thisThe “Energy” isn’t going anywhere because equilibrium is achieved, what might be happening is that at that temperature the atoms have a tendency to rearrange themselves in a equidistant lattice, much like water does when it freezes. What causes this might be something similar the weak force or some other type of energy being emitted from the atoms that isn’t strong enough to be noticed at higher temperatures.
There are a lot of misunderstandings in these posts and a few in the Article.
Reply | Report Abuse | Link to thisFirst, they have not reached Absolute Zero. That cannot be done. There is always some energy in the quantum states.
What this research group has done is to create a quantum inversion in the electron state. Normally, electrons move from a lower energy state to a higher one in the orbitals. This experiment created conditions where a very cold gas was trapped, and some atoms were influenced to have a condition where the electrons were in a higher state, and could only move to a lower state. Negative temperatures act just like positive temperatures do to the atoms energy state, but, when you combine the two, the energy appears to disappear, and the resultant gas has a lower overall temperature. The energy is actually transferred between the electron states in the atoms.
This corresponds to a negative temperature. Combine a gas with a negative temperature with a gas with a positive temperature, and the resultant gas will have a lower temperature. Thus, the temperature IS negative.
This is not an easy thing to do on a large scale. I wouldn't expect to see any products based on this sort of technology for several decades.
The experimenter didn't pass Absolute Zero as much as by pass it. Lasers and magnets were used to change the state of a small number of atoms.
If the effect can be stabilized, then adding (subtracting) energy to the system will reduce the temperature still more. It would mean some interesting things, such as apparently allowing more than 100% efficiency in heat engines. However, the total overall energy would still be less than that because of the work involved in creating the negative temperature gas in the first place.
This work opens up several interesting areas for research, but, is not what the Author of this Article thinks it is.
If no one had predicted this behavior, then my guess is that this phenomenon is a little more important than this article leads us to believe. So shooting from the hip...
Reply | Report Abuse | Link to thisThere is a possibility that this “Force” might be what causes The Second Law of Thermal Dynamics. Some type of “Field” with in the atoms pushes them into a equidistant arrangement, however most of the time this tendency isn’t noticed because of other affects like momentum, gravity and various forms of radiation.
Well obviously there is a breakdown in communications between the scientists, technical writers and laymen. I grasp the concept about combining to gasses and the energy state of the electrons. I am just trouble shooting from the hip here.
Reply | Report Abuse | Link to thisSecond shot from the hip...
Reply | Report Abuse | Link to thisThere are several factors that might be causing this phenomenon and one of them just might be the energy from the lasers and magnets in the first place. With so much energy be placed on the atoms, once the atoms reach a certain equilibrium then either the magnetic field or photons from the lazars might just be pushing the elections into a higher energy state and thereby causing the outward pressure.
To test that last hypothesis all’s one would have to do is increase either the magnetic field or the energy from the lazars; then the atoms should start loosing electrons.
Reply | Report Abuse | Link to thisYes, I think this makes about as much sense in the real world as hell freezing over.
Reply | Report Abuse | Link to thishairy_cheese, you are exactly right; "population inversion" was the first thought to pop into my mind as I read the article. I wonder when the researchers will try to see if their setup can be made to lase...
Reply | Report Abuse | Link to thisQuite interesting indeed!
Reply | Report Abuse | Link to thisAbsolute zero on Kelvin scale may be some arbitrary reference point on temperature scale. Otherwise on the physical realty level, there should be no meaning of zero temp. since a zero temp. of any system shall imply zero energy. No system can be with zero energy ( in realty on physical ground level) since some energy shall always be required for the sustenance of the quantum system. In the absence of some minimum energy level, atoms and their quantum system shall collapse. In view of non-feasibility of zero energy in any system, zero temp. in realty is also a hypothetical situation. This may be some mathematical construct only.
Reply | Report Abuse | Link to thisWhen zero values of energy and temp. are mathematical constructs depending upon benchmarked value of " zero", negative energy and negative temp. should also be some mathematical constructs or semantics as some commentators have pointed out. There is no absolute meaning of positive or negative value of any physical quantity say energy or temp. or any other quantity. All it depends upon the arbitrarily chosen reference point of "zero". On changing the value of arbitrary reference value of "zero", positive may become negative and negative may assume positive
These days most Scientific American articles on their web site are incomprehensible. If this article is true then this is revolutionary, but it is impossible to understand what was done here from the awful write-up which uses conflicting concepts in parallel repeatedly without even acknowledging that they conflict. How can dark energy which forces expansion be a parallel effect to molecules being more attracted to each other? Just one of many things which make absolutely no sense in this piece of writing. I'm sure there is a good scientific explanation, but you won't find it at Scientific American.
Reply | Report Abuse | Link to thisMaybe the problem is all the endless reprints of other sites' articles that we are getting nowadays. Standards have fallen into non-existence. Get the particle physicists on it; maybe they can locate SciAm's science reporting standards with the Large Hadron Collider.
Reply | Report Abuse | Link to thisIn case the criticism is correct, or partially correct,is Scientific American in print any better?
Reply | Report Abuse | Link to thisUsed to be fantastic.
Do you recommend Scientific American in print to keep ourselves up-to-date about what is going on and at the same time have access to top level articles with discussions in depth?
What can be done to improve SA on line if it really requires repair as some of you, gentlemen, suggest?
Laroquod, Plain-2009 - I empathize with your sentiments, but in this case the SA article is a 'reprint' of a "Nature" article reporting on research published in "Science" - please see:
Reply | Report Abuse | Link to thishttp://www.nature.com/news/quantum-gas-goes-below-absolute-zero-1.12146
S. Braun, et al., (2013), "Negative Absolute Temperature for Motional Degrees of Freedom",
http://www.sciencemag.org/content/339/6115/52
Back in 'the good old days', SA was published by Scientific American, Inc. More recently it has been published by Nature. As 'Plain-2009' asks, the print version comes off a little better than the web site, since it contains less 'filler' material from non-scientific web content sources, but still not meeting the standards set in the past, IMO...
(JTDwyer)
Reply | Report Abuse | Link to thisThank you very much.
I read the references.
Now I understand better what is going on (with respect to negative Kelvin temperatures).
We should also consider that a specialist in a certain field has two or three magazines more focus in his/her field that allow him to keep up to date or to write if he has something to say besides SA.
I think it is still a good idea to subscribe to the printed (or paid on line if it exists)version of SA.
In this way we can also help SA to stay up and running and return to the standards it used to have if some decline has really occurred.
I hope we can get the entire collection of SA since the better beginning in digital format at an affordable but fair price.
You are very kind and I fully appreciate your purpose.
"For instance, Rosch and his colleagues have calculated that whereas clouds of atoms would normally be pulled downwards by gravity, if part of the cloud is at a negative absolute temperature, some atoms will move upwards, apparently defying gravity."
Reply | Report Abuse | Link to thisCould this be the Holy Grail of anti-gravity? Sounds about right. Always looked like it would have something to do with very low K's.
What "new forms of matter"?
Reply | Report Abuse | Link to thisUnobserved psuedo-science. You mean like radio waves? Or those electrons moving about in your computer allowing you to post your statements?
Reply | Report Abuse | Link to thisJust because you don't understand it doesn't make it real. Discoveries are constantly being made that seem entirely pointless but over time have real practical application. Provided it can be reliably repeated and independently verified, it is science, not psuedo-science.
Illogical non scientific conclusion. There is no negative temperature!!!!! You should redefine absolute zero Kelvin to make sense and eliminate all uncertainty.
Reply | Report Abuse | Link to thisyes , the very nature of absolute zero is a vacuum . would the magnetic/laser matrix be maintaining the energy levels of the atoms , which would colapse with out it . the airisol is a good vehicle in as much as it show the forces and their competitions . altho if the can is used then a central core area would most approach abszero , but by their collapse they would cause a vacuum and thus the pressure would increase and abszero would be lost .the only way i can see this working to reach the real abszero and maybe maintain it is to have a long cylender with a pressor on one end exerting a force A , with a second pressor pushing on the opposite end with pressure A'pressor A' would have a small outlet which would control the rapidity of the expelled atom . as the rate of expelled atoms reached criticle point of causeing core to approach abszero , then pressor A would increase compression thus keeping a core area at abszero . the question would then be answered as to the true nature of atoms in abszero environ . one could postulate a universal form having a nutral nature which would respond to any input, but would this nutral nature be absolute zero ? if so then all stops and there is no negitive . if not then how could the remnant temp of the big bang be only a few degrees above abszero . yes it is there fore there is no sub zero possible . the biggest take from this is the possibility of using this matrix to hold and study atoms in a state which would help explain their elegance and mystery .
Reply | Report Abuse | Link to thisIt is a quirk of quantum gas to be below zero kelvin temperature. It is a groundbreaking discovery. It is very nice to share such view.
Reply | Report Abuse | Link to thisS. N. Tiwary
Directr
Calling anything Quantum is a misnomer. Quantum physics is a theory which states that all things are non-existent except to the observer. And Quantum Entanglement states that everything is contained within a small space which is nothing more than a holographic image which makes our reality.
Reply | Report Abuse | Link to thisInteresting as it might be, I think it a bit misleading.
Reply | Report Abuse | Link to thisFirst I have a lot of trouble with undergraduate who think there is no energy at absolute zero, and so I was dismayed to read it here:
"Absolute zero corresponds to the theoretical state in which particles have no energy at all, and higher temperatures correspond to higher average energies."
This is absolutely (no pun intended) wrong! There is lots of energy there due to the Pauli Exclusion principle (Fermi energy). What they should have said, and how I correct my students, is to say that there is no kinetic energy at T=0.
Second to say that the absolute scale is breached to negative temperatures is a little like people being confused that time reversal thinking it means going back it time. It does not. It just means that if you reverse time, some dynamic variables are negative and some a positive. It has nothing to do with "back to the future". So it is with negative temperatures which uses entropy in the definition. Then the usual definition of temperature is changed and the Kelvin scale breached, as this article discusses.
Of course this has been known for decades, and anyone who has worked with low temperature spin systems (or any system with a finite number of states) is well aware of all this. The new thing here is the new technology that has shed experimental light on negative temperatures which always opens up new avenues to study.
I am a bit skeptical about the suggestion about dark matter.
Interesting as it might be, I think it a bit misleading.
Reply | Report Abuse | Link to thisFirst I have a lot of trouble with undergraduate who think there is no energy at absolute zero, and so I was dismayed to read it here:
"Absolute zero corresponds to the theoretical state in which particles have no energy at all, and higher temperatures correspond to higher average energies."
This is absolutely (no pun intended) wrong! There is lots of energy there due to the Pauli Exclusion principle (Fermi energy). What they should have said, and how I correct my students, is to say that there is no kinetic energy at T=0.
Second to say that the absolute scale is breached to negative temperatures is a little like people being confused that time reversal thinking it means going back it time. It does not. It just means that if you reverse time, some dynamic variables are negative and some a positive. It has nothing to do with "back to the future". So it is with negative temperatures which uses entropy in the definition. Then the usual definition of temperature is changed and the Kelvin scale breached, as this article discusses.
Of course this has been known for decades, and anyone who has worked with low temperature spin systems (or any system with a finite number of states) is well aware of all this. The new thing here is the new technology that has shed experimental light on negative temperatures which always opens up new avenues to study.
I am a bit skeptical about the suggestion about dark matter.