Atoms at negative absolute temperature: The hottest systems in the world

Jan 04, 2013
Fig. 1: The Boltzmann distribution can be illustrated with balls that are distributed on a hilly landscape, which provides both a lower and upper bound for the potential energy of the balls. At positive temperatures (left figure), as they are common in everyday life, most balls lie in the valley around minimum potential energy. They barely move and therefore also possess minimum kinetic energy. States with small total energy are therefore more likely than those with large total energy – the usual Boltzmann distribution. At infinite temperature (central figure) the balls spread evenly over low and high energies in an identical landscape. Here, all energy states are equally probable. At negative temperatures (right figure), however, most balls wander on top of the hill, at the upper limit of potential energy. Also their kinetic energy is maximal. Energy states with large total energy are occupied more than those with small total energy – the Boltzmann distribution is inverted.

(Phys.org)—In cold regions on earth, negative temperatures on the Fahrenheit or Celsius scale can often occur in winter; in physics, however, they were so far impossible. On the absolute temperature scale that is used by physicists and also called Kelvin scale, one cannot go below zero – at least not in the sense of getting colder than zero Kelvin. According to the physical meaning of temperature, the temperature of a gas is determined by the chaotic movement of its particles – the colder the gas, the slower the particles. At zero Kelvin (-460°F or -273°C) the particles stop moving and all disorder disappears. Thus, nothing can be colder than absolute zero on the Kelvin scale. Physicists of the Ludwig-Maximilians University Munich and the Max Planck Institute of Quantum Optics in Garching have now created an atomic gas in the lab that has nonetheless negative Kelvin values (Science, Jan 4, 2013).

These negative absolute temperatures lead to several striking consequences: Although the atoms in the gas attract each other and give rise to a negative pressure, the gas does not collapse – a behavior that is also postulated for in cosmology. Also supposedly impossible heat engines can be realized with the help of negative absolute temperatures, such as an engine with a thermodynamic efficiency above 100%.

In order to bring water to the boil, needs to be added to the water. During heating up, the increase their kinetic energy over time and move faster on average. Yet, the individual molecules possess different kinetic energies – from very slow to very fast. In , low- are more likely than high-energy states, i.e. only a few particles move really fast. In physics, this distribution is called Boltzmann distribution. Physicists around Ulrich Schneider and Immanuel Bloch have now realized a gas in which this distribution is exactly inverted: Many particles possess large energies and only a few have small energies. This inversion of the energy distribution means that the particles have assumed a negative absolute .

"The inverted Boltzmann distribution is the hallmark of negative absolute temperature; and this is what we have achieved," says Ulrich Schneider. "Yet the gas is not colder than , but hotter. It is even hotter than at any positive temperature – the temperature scale simply does not end at infinity, but jumps to negative values instead." The underlying principle can best be visualized with an illustration (see Fig. 1): If one starts at positive temperatures (left figure) and increases the total energy of the balls by heating them up, the balls will also spread into regions of high energy. If one heated the balls to infinite temperature (central figure), each point in the landscape would be equally probable, irrespective of its energy. If one could add even more energy and thereby heat the balls even further, the balls would preferably gather at high-energy states (right figure) and would be even hotter than at infinite temperature. The Boltzmann distribution would be inverted, and the temperature therefore negative. At first sight it may sound strange that a negative absolute temperature is hotter than a positive one. This is, however, simply a consequence of the historic definition of absolute temperature; if it were defined differently, this apparent contradiction would not exist.

Hot minus temperatures: At a negative absolute temperature the energy distribution of particles inverts in comparison to a positive temperature. Many particles then have a high energy and few a low one. This corresponds to a temperature which is hotter than one that is infinitely high, where the particles are distributed equally over all energies. A negative Kelvin temperature can only be achieved experimentally if the energy has an upper limit, just as non-moving particles form a lower limit for the kinetic energy at positive temperatures -- physicists at the LMU and the Max Planck Institute of Quantum Optics have now achieved this. Credit: LMU and MPG Munich

This inversion of the population of energy states is not possible in water or any other natural system with moving particles, as the system would need to absorb an infinite amount of energy – an impossible feat! However, if the system possesses an upper bound for the energy of the individual particles, such as the top of the hill for the potential energy in Fig. 1, the situation will be completely different. The researchers around Immanuel Bloch and Ulrich Schneider have now realized a gas of atoms possessing such an upper energy limit in their laboratory, following theoretical proposals by Allard Mosk and Achim Rosch.

In their experiment, the scientists first cool around a hundred thousand atoms in a vacuum chamber to a positive temperature of a few billionth Kelvin and capture them in optical traps made of laser beams. The surrounding ultrahigh vacuum guarantees that the atoms are perfectly isolated from the environment. The laser beams create a so-called optical lattice, in which the atoms are trapped in a perfectly ordered array of millions of bright light spots emerging from the interference between the laser beams. In this lattice, the atoms can still move from site to site via tunneling, yet their kinetic energy is limited from above and therefore possesses the required upper energy bound. Temperature, however, relates not only to kinetic energy, but the total energy of the particles, which in this case includes interaction and potential energy. The system of the Munich and Garching researchers also sets a limit to both of these. By suddenly turning a valley into a hill (and changing the interaction), the physicists then take the atoms to the upper boundary of the total energy – thus realizing a negative temperature, at minus a few billionth Kelvin.

"If balls possess a positive temperature and lie in a valley at minimum potential energy, this state will apparently be stable – this is nature as we know it. If the balls are located on top of a hill at maximum potential energy, they will usually roll down and thereby convert their potential energy into kinetic energy. If the balls are, however, at negative temperature, their kinetic energy will already be so large that it cannot increase further. Therefore the balls cannot roll down and stay on top of the hill. The energy boundary therefore renders the system stable!" explains Simon Braun, PhD student in the group. The negative temperature state in their experiment is indeed just as stable as a positive temperature state. "That way, we have created the first negative absolute temperature state for moving particles," he adds.

Matter at negative absolute temperature leads to a whole bunch of astounding consequences: With its help, one could create heat engines with an efficiency above 100%. This does not mean that the law of energy conservation is violated. Instead, the machine could not only absorb energy from the hotter substance, but, in contrast to the usual case, also from the colder. The work performed by the engine could therefore be larger than the energy taken from the hotter substance alone.

The achievement of the Munich physicists could additionally be interesting for cosmology. Concerning its thermodynamic behavior, negative temperature states exhibit parallels to the so-called dark energy. Cosmologists postulate dark energy as the elusive force that accelerates the expansion of the universe, although the cosmos should in fact contract because of the gravitational attraction between all masses. There is a similar phenomenon in the atomic cloud in the Munich lab: The experiment relies upon the fact that the atoms in the gas do not repel each other as in a usual gas, but instead interact attractively. This means that the atoms exert a negative instead of a positive pressure. As a consequence, the atom cloud wants to contract and should usually collapse – just as is expected for the universe under the influence of gravity. But because of its negative temperature this does not happen. The gas is saved from collapse just like the universe.

Explore further: Thermoelectric power plants could offer economically competitive renewable energy

More information: Braun, S. et al., Atoms at negative absolute temperature - the hottest systems in the world, Science, 4 January 2013. www.sciencemag.org/content/339/6115/52

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Lurker2358
1.2 / 5 (18) Jan 04, 2013
This does not mean that the law of energy conservation is violated. Instead, the machine could not only absorb energy from the hotter substance, but, in contrast to the usual case, also from the colder. The work performed by the engine could therefore be larger than the energy taken from the hotter substance alone.


Forum Mafia is going to have a field day with this one.

This would require a re-write of the so-called "Laws" of Thermodynamics, which by the way, would mean that perpetual motion, or nearly perpetual motion machines can in fact be made.

Imagine automobiles that get 500 miles per gallon equivalent with this negative absolute temperature!

By the way, what happens if an ordinary atom gains a large amount of kinetic energy from the so-called "Negative energy" which is observed in some laboratories and theoretical physics?

Are these guys sure they haven't made a "negative energy battery"?
antialias_physorg
4.6 / 5 (15) Jan 04, 2013
This would require a re-write of the so-called "Laws" of Thermodynamics,

Nope. If you had read the entire article before posting you would have noticed this part:
"This does not mean that the law of energy conservation is violated."

and maybe also this part:
"Temperature, however, relates not only to kinetic energy, but the total energy of the particles, which in this case includes interaction and potential energy."

and maybe also this part
The experiment relies upon the fact that the atoms in the gas do not repel each other as in a usual gas, but instead interact attractively.


All of which means that you can do freaky stuff with the temperature - but at the expense of other types of energy (which in itself is just business as usual. )

The negative temperature thing is, however, awesome.

(As an aside: a substance with inverted Boltzman distribution is normally useable as a laser medium. But in this case the distribution is stable. That's freaky.)
Lurker2358
1.7 / 5 (12) Jan 04, 2013
A_P:

I did read the entire article, and extracting work by moving energy from a cold reservoir to a hot reservoir (i.e. making one sink behave as both a hot sink and a cold sink simultaneously,) does violate the Second Law.
Tektrix
5 / 5 (2) Jan 04, 2013
Modernmystic
1 / 5 (6) Jan 04, 2013
Could this provide an avenue to extract vacuum energy?
Rob
4 / 5 (4) Jan 04, 2013
By suddenly turning a valley into a hill (and changing the interaction), the physicists then take the atoms to the upper boundary of the total energy – thus realizing a negative temperature, at minus a few billionth Kelvin."

Is it that far of a stretch to think that changing the optical lattice changes the energy of the larger system in such a way that no violation is seen? If you don't see this then go ahead and design your perpetual motion machine that runs on 120V AC.
Lurker2358
1.6 / 5 (14) Jan 04, 2013
Yeah, it's that bad.

If their results and interpretation is correct, there's no good reason you wouldn't be able to make an ion engine (or maybe a photon engine,) that could do nearly infinite work using 1 atom's worth of energy.

Of course, there are other theoretical ways to get infinite work out of a single photon, by using two mirrors in space, but that one is already known and it's too complicated because the photon will eventually get misaligned.

The piont is, this "findings" are almost too silly to be true.

You could take the excess heat from AGW and move it into the "negative" reservoir and viola, no climate change.

You could extract energy from the cold sink (such as your own coolant on a rocket,) and use that energy to produce thrust...ouch...

You could make an engine that runs just by moving ambient heat around, and probably wouldn't even need fuel at all.
Tektrix
5 / 5 (10) Jan 04, 2013
Two things here: 1- The system in use has upper and lower bounds for the atomic degrees of freedom. In this context, the idea of "infinite" becomes highly relative- as for instance, the top of a hill being the absolute height one can reach on that hill.

2 This is a statistical phenomenon- it is a *statistical hill*- and the system context is a statistical distribution within an ensemble of several thousand *isolated* atoms. The isolation is critical- to do the entropic trick this rig does, it has to be cut off from any outside source of energy. Not only kinetic, but interaction, and potential energy too. This isolation requirement is what lets the system seem to fly in the face of thermodynamics #2. In reality, you can only take it so far and then you run out of *work*. Once you open the system to the outside world, everything re-equalizes. Within this context then, they are altering the distribution of energetic atoms to become the inverse of what is normally observed.
SincerelyTwo
4.4 / 5 (5) Jan 04, 2013
It's not perpetual motion which defies the laws of physics, it's the production of infinite free energy. The two ideas are often merged together but are actually two entirely different things.

A super conducting coil is in fact a perpetual motion system, electrons will continue to flow forever so long as the coil remains in a superconducting state.

An object in motion indefinitely does not defy the laws of physics, period.

Using the superconducting coil as an example, once electrons are removed and used for power, there is nothing to replenish those electrons, more have to be added to the system.

This is starting to sound familiar, isn't it? It's called a battery. That's what perpetual motion comes down to, storing energy without leaking it. Perpetual motion occurs when your energy efficiency == 100%, you're breaking laws when you claim > 100%, we usually deal with < 100% efficient systems.
ValeriaT
1 / 5 (15) Jan 04, 2013
In AWT the magnetic field makes the vacuum foam more thick in similar way, like the soap foam during shaking. This dense foam expels the light objects, i.e. it acts against gravity field. Analogously we could compress the cold gas at 0 K - its thermodynamical temperature would be negative, after then. The negative energy waves are scalar Tesla waves: the massive objects shield them at their proximity, but another massive objects shield this shielding, which leads into areas of undercooled vacuum: the dark matter.
Could this provide an avenue to extract vacuum energy?
Yes, I presume the energy provided with vacuum fluctuations for spontaneous demagnetization of magnetic domains is the basis of many ZPE overunity devices presented on the web. These devices work like the magnetic refrigerator - just at room temperature.
frajo
5 / 5 (4) Jan 04, 2013
the balls would ... be even hotter than at infinite temperature.

I don't like this confusing kind of playing with words and their differing semantics in macro and quantum physics.
Moreover, mathematically, there is nothing "hotter" than "infinitely hot" as ["infinity" plus N = "infinity"].

"Balls" are objects with many degrees of freedom. Therefore, their temperature has the colloquial meaning. But "balls" is not a valid term to describe atoms in a quantum system.
"Hot" is a word that has meaning only in a colloquial context. "Hot" is not a term defined in physics.

"Infinite temperature", however, is a term that has meaning only in the context of quantum systems with artificially reduced numbers of degrees of freedom and does not describe a macroscopic temperature.

Thus, the words "ball", "hotter", and "infinite temperature" must not be used as if they were attributable to the same context.

More information: http://en.wikiped...perature
AWaB
4.8 / 5 (4) Jan 04, 2013
http://www.nature...-1.12146

The above link is far more comprehensible than the phys.org article.
Pressure2
1 / 5 (6) Jan 04, 2013
What proof do they have that these atoms that are attracting each other are below absolute zero? Close to absolute zero atoms would stop repelling each other in a gas because they only repel each because they have motion and collide with each other. They could be moving so slowly that two atoms might be hooking up electromagneticlly.
Lurker2358
1 / 5 (11) Jan 04, 2013
1 photon plus 2 mirrors = double infinite energy,

...and it doesn't violate conservation laws.

At least, that's apparently possible given the way solar sails work.
RealityCheck
2 / 5 (8) Jan 04, 2013
From article....
The laser beams create a so-called optical lattice, in which the atoms are trapped in a perfectly ordered array of millions of bright light spots emerging from the interference between the laser beams. In this lattice, the atoms can still move from site to site via tunneling,
So each atom is effectively a separate isolated 'system' because each light lattice 'spot' is effectively an 'individual container' for its respective atom. Atoms may 'tunnel' between 'container lightspot' positions, but they are effectively NOT part of a 'statistical whole' gaseous system anymore, but only 'fixed arrangement' of atoms controlled by laser lightspot 'pattern'.

So if the atoms are not part of a statistically dynamic (temperature context) system anymore, but only individually contained atoms that randomly 'tunnel' AS ISOLATED ATOMS between fixed lightspot 'containers', then atoms do not 'collide' with one another, and hence 'temperature' term/concept not applicable. :)
packrat
1 / 5 (4) Jan 04, 2013
It may sound silly but after reading the various articles on it all I can see is they are not completely sure where '0' is. Either the atoms have stopped moving or they haven't. Maybe different atoms have slightly different '0' temps when stopped?
ValeriaT
1.1 / 5 (8) Jan 04, 2013
Due the quantum noise (Brownian motion of the vacuum) the atoms are moving even at zero temperature (for example, the liquid helium never freezes at room temperature just because of it). So there is still space for some cooling, when you orient the atoms with external magnetic field...
Pressure2
1 / 5 (4) Jan 04, 2013
Due the quantum noise (Brownian motion of the vacuum) the atoms are moving even at zero temperature (for example, the liquid helium never freezes at room temperature just because of it). So there is still space for some cooling, when you orient the atoms with external magnetic field...

I think you mean helium never freezes near absolute zero. One cannot assume that helium would not freeze at absolute zero. After all helium is an extemely neutral electromagneticly atom.
Q-Star
2.5 / 5 (8) Jan 04, 2013
For historical reasons (the temperature measurement systems) have left us with the Kelvin scale,,,,, had temperature quantification been based on the beta constant instead, the article would seem much less counter intuitive. But that relationship came after every one was already comfortable with hotter being larger numbers. Boltzmann tried but everyone resisted.
Q-Star
3.2 / 5 (11) Jan 04, 2013
the liquid helium never freezes at room temperature


Well I for one agree with you on that,,,, and I'm very pleased that it does not.
Lurker2358
1 / 5 (8) Jan 04, 2013
If you have a kilogram of water at close to absolute zero, and you add 4200 Joules worth of "negative energy" what will the new temperature be?
boater805
4.5 / 5 (8) Jan 04, 2013
A_P:

I did read the entire article, and extracting work by moving energy from a cold reservoir to a hot reservoir (i.e. making one sink behave as both a hot sink and a cold sink simultaneously,) does violate the Second Law.

The Laws of thermodynamics are prefaced by "for a CLOSED SYSTEM" .. The system described is NOT closed .. energy has been extracted FROM it and removed from the system. Energy is input to the system via the Photonic lattice trap which is completed powered by laser external to the system. You analysis of thermodynamics is ignoring all these NON closed system energy sources that moot your observation. After expanding the "system" to include all this requisite apparatus, the Local variation is well within the statistical thermodynamic laws.
Q-Star
2.2 / 5 (10) Jan 04, 2013
It's not perpetual motion which defies the laws of physics, it's the production of infinite free energy. The two ideas are often merged together but are actually two entirely different things.


You quibble over words? All matter is acted upon by an external force however small it may be. Any matter that moves perpetually with constant motion must be able to overcome the external forces (however small) that act upon it. That is why perpetual motion is impossible, you must always be adding something to the system.

Perpetual motion would only be possible in a universe that contained only ONE single point-like particle and only THAT one.
D_Rouge_Physicist
2.3 / 5 (6) Jan 04, 2013
This is seriously the funniest physics discussion I have ever read on the internet....Putting this one into the x-file drawer.
VendicarD
4.3 / 5 (6) Jan 04, 2013
"Putting this one into the x-file drawer." - D_Rouge

Forgive them Gawad for they know not what they say.

Watching this thread is like watching a random diffusion of ignorance.

This is how the U.S. congress makes it's decisions.

It is how trial by ordeal was logically arrived at.

They use the same logic used to conclude that bad smells create disease.

VendicarD
4.4 / 5 (7) Jan 04, 2013
The definition of temperature is..

T = k*(d(Entropy)/d(Energy))**-1

k is positive.

Therefore, if the rate of change of energy or entropy have opposite signs, then the absolute temperature of the system is negative.

Normally if you add energy to a system it's entropy also increases, and hence it's temperature increases.

If you can contrive a situation in which entropy decreases as you increase a aystem's energy... ie., the system becomes more ordered as you add energy then it's Absolute temperature is negative.

It all comes down to definition, and how precise definitions do not necessarily map expectations exactly onto real world behaviour.

There is nothing magic here. No extraction of energy from the vacuum, or from alternate universes, or violation of the principles of thermodynamics.

All of that mumbo jumbo above is just pure ignorance.

Alexander Riccio
not rated yet Jan 04, 2013
Mind. Blown.
Silverhill
5 / 5 (2) Jan 04, 2013
@Lurker2358
1 photon plus 2 mirrors = double infinite energy,

...and it doesn't violate conservation laws.

At least, that's apparently possible given the way solar sails work.
One photon bouncing between two *perfect* (i.e., non-realizable) mirrors could bounce forever (provided there was no interaction with a wandering virtual particle), but it would not represent infinite energy (much less "double infinite energy").

Solar sails do not work by bouncing photons between mirrors. They bounce photons from a single mirror, reversing the photons' momentum and giving an equal-but-opposite momentum to the mirror.
Silverhill
not rated yet Jan 04, 2013
@Q-Star
Any matter that moves perpetually with constant motion must be able to overcome the external forces (however small) that act upon it. That is why perpetual motion is impossible, you must always be adding something to the system.
If there are *no* (net) external forces, the matter has nothing to overcome. In the supercurrent condition, the electrons experience zero resistance, so they can indeed move perpetually without energy loss. This is an example of "perpetual motion of the third kind"**, where there are no losses, but there is also no way to extract work from the system without diminishing its energy. There is a supercurrent in a lead ring at MIT that has been circulating undiminishedly for decades.

** first kind: creates energy (> 100% efficiency)
** second kind: can be tapped for doing work, but does not increase global entropy
rah
1.7 / 5 (6) Jan 04, 2013
It said that one example was heated to infinity, then it said heat it further. This don't make no sense to me..
lomed
5 / 5 (6) Jan 05, 2013
Negative temperature is not a revolutionary concept, any undergrad thermal physics course should cover it. What is of interest is a realization of such a system in an experiment. In particular, the abstract mentions that this is the first time such a system has been realized using properties of the effective kinetic energy/momentum (it was achieved long ago in magnetic systems, for which the experiment is much easier to set up).

None of the laws of thermodynamics are violated by this setup (nor does it imply that they could be) (see VendicarD's post above).
ValeriaT
1 / 5 (7) Jan 05, 2013
I think you mean helium never freezes near absolute zero.
I wanted to say, the helium never freezes at room pressure. In dense aether model it's an analogy of the Brownian motion of pollen grains dispersed in water - the impacts of vacuum fluctuations keeps the atoms in neverending quantum motion. It's the simplest explanation of this mysterious phenomena and evidence of dense aether model at the same time.
after reading the various articles on it all I can see is they are not completely sure where '0' is
This is just the temperature, at which the (motion of) atoms aren't affected with another atoms (directly or indirectly trough photons) - only with density fluctuations of the vacuum itself. But it doesn't mean, these atoms will be at rest during absolute zero temperature. If we would constrain their motion artificially, we could achieve the negative temperatures rather easily.
ValeriaT
1 / 5 (8) Jan 05, 2013
From thermodynamical perspective our life in space-time is analogous to life in the blast furnace at the surface of molten iron. At the moment when the surface of iron will be kept completely still, it will form a mirror-like flat surface - this is an analogy of the absolute zero temperature. Of course this temperature could be lowered - the "only" problem is, how to do it, if we are surrounded with molten iron all the time?
Lurker2358
1 / 5 (6) Jan 05, 2013
Solar sails do not work by bouncing photons between mirrors. They bounce photons from a single mirror, reversing the photons' momentum and giving an equal-but-opposite momentum to the mirror.


That's why the two mirrors will accelerate away from one another forever. they will in fact have infinite energy; well, unless light horizons actually exist, in which case there is a finite limit when they are about 15 billion light years away from one another.

Ah, but you thought I was just sticking two mirrors on a shelf and watching the fun.

Nope. Hehe.

In the thought experiment they are in space. We're using two solar sails to accelerate ships in opposite directions using just one photon.
antialias_physorg
5 / 5 (5) Jan 05, 2013
That's why the two mirrors will accelerate away from one another forever.

Jesus Christ. Every time I think you can't show any more misunderstanding of the most basic of highschool physics you prove me wrong.
What do you think happens when a photon impacts on a mirror and transfers momentum/energy? Guess what: it gets reemitted as a photon with a greater wavelength (less energy). The total momentum that will be transferred to two such free floating mirrors will not be infinite. It will just be equal to the total momentum the the photon initially had (h/lambda).

Man. You really need to pick up a textbook. And I mean one that starts with "See Spot..."
frajo
2.3 / 5 (3) Jan 05, 2013
In the supercurrent condition, the electrons experience zero resistance, so they can indeed move perpetually without energy loss. This is an example of "perpetual motion of the third kind"**, where there are no losses, but there is also no way to extract work from the system without diminishing its energy. There is a supercurrent in a lead ring at MIT that has been circulating undiminishedly for decades.

"Perpetually" means forever. But the supercurrent won't flow forever as the setting needs cooling. It is not a closed system.
ValeriaT
1 / 5 (6) Jan 05, 2013
We know about room-temperature superconductors too (BTW Joe Eck is the most successful SC researchers all the time - not surprisingly he lives completely out of the mainstream). Inside of small metallic rings the electrons are revolving even at the room temperature.
Q-Star
2.5 / 5 (13) Jan 05, 2013
If there are *no* (net) external forces, the matter has nothing to overcome.


All particles, EVERY SINGLE PARTICLE IN THE UNIVERSE, experiences an external force. The only, ONLY, exception is the entire universe considered as a single particle. A single proton, feels a force from every other proton in the universe,,,, there is no truly closed system except the universe as a whole.
VendicarD
4 / 5 (4) Jan 05, 2013
False.

"A single proton, feels a force from every other proton in the universe,,,," - Q-Star

If I create a proton/antiproton pair, the resulting charge polarization wave that moves through space does so at a finite speed of c. So if the creation event occurs at time t, then anything beyond a distance of ct is unaware of the existence of the proton/antiproton pair.
VendicarD
5 / 5 (2) Jan 05, 2013
Wrong.

"That's why the two mirrors will accelerate away from one another forever. they will in fact have infinite energy;" - Lurker

The transfer of energy to the mirrors reduces the energy of he reflecting photon.

With each reflection, the photon vanishes a little bit more.

Since reflection is a quantum event, it will vanish entirely in short order.
Q-Star
3 / 5 (10) Jan 05, 2013
False.

If I create a proton/antiproton pair,


They will feel the forces that pre-exist them in the space they emerge into. But even they didn't,,,,,

They will each feel a force from the other. There is no such thing as a truly closed system unless you define the universe as such.

That's why we call the "conservation of energy" a fundamental principle.
Q-Star
3 / 5 (10) Jan 05, 2013
If I create a proton/antiproton pair, the resulting charge polarization wave that moves through space does so at a finite speed of c. So if the creation event occurs at time t, then anything beyond a distance of ct is unaware of the existence of the proton/antiproton pair.


And how would create a proton-antiproton pair in isolation? Without the input of some matter-energy? It will win you a Nobel when you discover that.
frajo
2 / 5 (2) Jan 05, 2013
So if the creation event occurs at time t, then anything beyond a distance of ct is unaware of the existence of the proton/antiproton pair.

Sorry, but in order that ct be a distance t has to be a time interval.
brt
1.8 / 5 (5) Jan 05, 2013
So this whole thing basically boils down to: this is negative temperature...because they've highly restricted the parameters of the system and the definition of temperature. This is better described as an artificial negative temperature. It's using semantics and abusing mathematics in the presence of those who aren't well versed in the subject; Like saying that time is slower on earth than it is on the moon.
antialias_physorg
4.2 / 5 (5) Jan 05, 2013
Like saying that time is slower on earth than it is on the moon.

Which it is, because on Earth you are in a deeper gravity well than on the Moon (hence more time dilation). And this has been established via experiment. (it's also a piece of knowledge without which GPS wouldn't work at all)

because they've highly restricted the parameters of the system and the definition of temperature.

They're using the standard scientific definition of temperature. If you want to argue that scientific writings shouldn't use the scientifically established definitions but your personal ones then that's just insane.
irjsiq
1 / 5 (5) Jan 05, 2013
who determined the Laws of Physics? . . . It took several 'Decades' for acceptance that the Earth revolved around the Sun'! We see similar 'refusals' to accept 'New'! It was Dozen years to accept 'Bacteria' as the cause of Duodenal/Gastric Ulcers. I may not be bright enough to fathom such postings; but then: "Show me/or state Your Proof that a Divine Intellect, or other, such Conceptual ?Entity? Does No Exist."
Steven Hawking, having concluded that there 'Is no God', awakened me.
VendicarD
5 / 5 (1) Jan 05, 2013

"They will feel the forces that pre-exist them in the space they emerge into." - Qstar

But most of the universe will not experience any force from them since it does not yet exist in their light cone.

And this is true for any proton/antiproton pair arising in the universe.

Most of them you are incapable of detecting since they are too far away.
MRBlizzard
2.6 / 5 (5) Jan 05, 2013
I remember a colloquium in graduate school. SrTiO3 also exhibits negative temperature at 105 K, when it transitions from cubic to tetragonal crystal structure. As I remember it, the recoil free fraction goes to zero at the transition temperature. This leaves behind the non-zero phonon components of the phonon spectrum. With nothing at the bottom of the phonon spectrum, the material has an inverted population.

As I remember it, near the transition temperature, the recoil free fraction becomes very large, which suggests that SrTiO3 may be useful for Mossbauer experiments. However, there were some arguements that the very large zero free fraction was not actual, but a virtual/mathematical artifact and, thus, not real.
brt
2 / 5 (4) Jan 06, 2013
Like saying that time is slower on earth than it is on the moon.

Which it is, because on Earth you are in a deeper gravity well than on the Moon (hence more time dilation). And this has been established via experiment. (it's also a piece of knowledge without which GPS wouldn't work at all)

because they've highly restricted the parameters of the system and the definition of temperature.

They're using the standard scientific definition of temperature. If you want to argue that scientific writings shouldn't use the scientifically established definitions but your personal ones then that's just insane.


Of course time dilation is true you ignorant pompous jackass; what I'm saying is that time isn't really slowing down unless you are experiencing the difference in gravitational force. In the same way, they haven't reached a negative temperature, they've manipulated the interchange of energy.
brt
2.6 / 5 (5) Jan 06, 2013
they haven't reached negative temperature; they've manipulated how the system exchanges energy so that the resulting mathematics say they have produced negative temperatures. The math does not always match the physical action; e.g. infinities do not actually exist in nature.
ValeriaT
1 / 5 (5) Jan 06, 2013
Well, they manipulated the system in such a way, it looses entropy when the energy is added, which is what the negative temperature is, well - thermodynamically. I dunno about infinities, but the zero state is quite common in our fuzzy dull world.
Lex Talonis
1 / 5 (6) Jan 07, 2013
Reminds me of the study...

That assumed on the radiographical analasis (typing in dark here with a no letter keyboard) that the atmosphere would in fact not be set globally on fire, due to atmospheric testing of the Mighty A Bomb.

However in plunging below absolute zero, if THAT ever escapes from the laboratory, it could devastate the entire planet, by flash freezing the entire surface.......

We are doomed! Doomed I tell ye!
Silverhill
5 / 5 (1) Jan 07, 2013
@frajo
"Perpetually" means forever. But the supercurrent won't flow forever as the setting needs cooling. It is not a closed system.
I didn't say that it was a closed system; everything needs an appropriate environment. Imagine a box (to provide shading from even faint starlight) in intergalactic space, with an effective internal temperature of 2.7 K. Put a supercurrent ring inside. The universe at large provides the necessary environment. (This is not physical perfection, but it's as close as we're likely to get.)

@Q-Star
All particles, EVERY SINGLE PARTICLE IN THE UNIVERSE, experiences an external force.
Notice that I said no NET force.

"May the net force be with you."

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