Can you get negative kelvin

Therefore, an ideal gas must have a positive temperature. Now let's look at the Einstein solid case in more detail. In general, unless the kinetic energy is somehow bounded, the presence of a kinetic term implies a positive temperature as I understand it.

To create a negative temperature system, you would need the appropriate bounds on the Hamiltonian. In negative-temperature systems, if you increase the total energy, you decrease the entropy - and by our statistical definition of temperature, the system must have a negative temperature. This doesn't mean that the average energy per particle in the system has a negative energy ; therefore, it's not useful for creating something like an Alcubierre drive.

There are some interesting consequences to this. In the absence of performing work as is the case in a refrigerator, where work is performed to cool your food , when two objects with positive temperatures are placed in contact, heat will flow from the one with the higher temperature to the one with the lower temperature. On the other hand, if one object has a negative temperature and the other has a positive temperature, heat will always flow from the negative-temperature object to the positive-temperature object.

In this sense, an object with negative temperature is always hotter than an object with positive temperature. As I've stated above, we need to separate the notion of temperature from the notion of kinetic energy. From this, you'd think that a negative temperature corresponds to a negative kinetic energy - but as the sort of negative-temperature systems we're talking about don't involve billiard ball-like particles moving around classically, it's not really correct to say that they have negative energies.

Consider iron. Fusion of elements lighter than iron gives off energy and heat the stars. Fusion of iron and elements heavier absorbs energy and so cools the star, ultimately making it either fade or explode. Actually fusion of some lighter isotopes also absorbs energy as well which might be good for the story if iron fusion seems trite. In any case: people in your world have figured out how to do muon catalyzed fusion, inducing fusion without extreme temperatures and pressures.

That is where they get their energy. Induced fusion of heavy elements is endothermic, absorbing energy. If this spooky muon tech is used to cause fusion of iron nuclei but the need of this matter for energy is greater than what can be met in the surroundings, the resulting matter goes into debt - a temperature lower than absolute zero, because all ambient energy has been absorbed and additional input energy disappears into trying to complete formation of the heavy element product of the fusion.

The problem is that we barely scratched the surface in these fields. They work with uncertainty in their principles even, allowing for things to basically teleport across barriers, or at the same time be, not to be and any combination thereof. Incredibly simplistic: Temperature is basically a way to say how fast the molecules are moving around.

Kelvin is measured from when molecules have stopped moving completely. It isn't possible to get lower than not moving. They did discover these negative Kelvin degrees in a quantum gas or similar, but how they derive it's lower than 0 Kelvin is lost on me. Negative density is something else however. It is not just the absence of mass, but negative mass.

I really don't understand either further than these definitions. Temperature is a property of mass and it seems unlikely to me it can create negative mass. A parrellel to this is like if a bowling ball is rolling at you, you can strike if halfway with another bowling ball, of equal and speed, and this effect will cancel the bowling ball comming at you and cancel the motion.

Laser cooling takes this same effect, instead shooting waves of light with wavelengths that are almost matching the jitterering of the molecules the gas is hitting.

So it cancels the motions and therefore reducing the temperature. Wolfgang Ketterle. Reprints and Permissions. Merali, Z. Quantum gas goes below absolute zero. Nature Download citation. Published : 03 January Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative. Advanced search. Skip to main content Thank you for visiting nature. Download PDF.

Subjects Condensed-matter physics Quantum physics. Absolute zero, or 0 degrees Kelvin, is the temperature where all motion stops. It's the lowest limit on the temperature scale, but recent news articles have heralded a dip below that limit in a physics lab.

Is absolute zero less absolute than we thought? Read on to find out. A Bose Einstein condensate is made up of atoms that can occupy the same state. They put these atoms in an optical dipole trap. They then used a tunable three-dimensional optical lattice that acts like a crystalline structure for the potassium atoms to reside in and creates an associated energy band structure.

The optical lattice consists of a bunch of laser beams set to create a standing wave that acts like a lattice structure for the potassium atoms to be in. The potassium atoms in this lattice structure remain in their lowest internal energy state, but they have an associated band structure.

The lattice confines the motional states of the atoms to this lowest energy band; however, this band consists of many states momenta states for each atom. The researchers observed that the atoms could all be in their lowest energy band level and very near to the lower edge of that energy band level. Consequently, the system was extremely ordered the amount of order is key to this and, as you might expect, very cold.

Keeping the atoms in this low-energy state led to a temperature of only a few billionths of a Kelvin. This is akin to turning a stable valley into a stable hill.

In this situation the atoms are very ordered, cannot go to another energy level, and have a negative temperature value! Below is an image of the momentum distribution at negative temperatures of the potassium atoms in the optical lattice. The momentum is proportional to the kinetic energy motion energy of the atoms, and the peaks show the maximum kinetic energy.

This means that the atoms exert a negative instead of a positive pressure. As a consequence, the atom cloud wants to contract and should really collapse — just as would be expected for the universe under the effect of gravity.

But because of its negative temperature this does not happen. The gas is saved from collapse just like the universe. Materials provided by Max-Planck-Gesellschaft.

Note: Content may be edited for style and length. Science News. Journal Reference : S. Braun, J. Ronzheimer, M. Schreiber, S. Hodgman, T. Rom, I. Bloch, U. Science , ; : 52 DOI: ScienceDaily, 4 January