Cloud of atoms goes beyond absolute zero

It looks like absolute zero isn't so absolute any more. Absolute zero on the Kelvin scale is supposed to be the lowest temperature possible as it is the temperature at which all atomic movement is supposed to stop. It was thought impossible for anything to be colder than that. But now they are saying they have produced negative temperatures on the Kelvin scale.

SOURCE

Nothing is colder than absolute zero, so it seems nonsensical to talk about negative temperature – but now there is a substance that must have just that. The revelation could shake up our ideas about temperature and help us understand strange entities such as dark energy, as well as the interactions of subatomic particles.

On the kelvin scale, temperature is determined by the kinetic energy of particles, so a gas of slow particles is colder than a gas of fast-moving ones. Absolute zero corresponds to the point at which particles stop moving completely, which is why nothing can be colder.

Schneider's team then turned this positive temperature system negative by doing two things. They made the atoms attract and adjusted the lasers to change the atoms' energy levels, making the majority of them high-energy, and so flipping the valley into an energy hill. The result was an inverse energy distribution, which is characteristic of negative temperatures.

reply to post by happykat39


Very interesting article! A bit head-nipping to understand but fascinating all the same. Thank you for that

Think of this as a metamaterial-like solution.

Building a metamaterial structure, no one part of it has negative permeabilities or whatnot, but the behavior of the entire structure is as if it did.

In this case, no one atom in the aggregate is below absolute zero. However, the experimenters have engineered the characteristics of a group of them to have "unnatural" behavior as a group, in this case the group behaves as if it's below absolute zero in some regards.

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So does that mean dark energy and tempertures with gases out in space is more difficult to move through, like a space vehicle and needs more energy to move?

Very cool, pun intended

So if absolute zero K is the coldest temp possible then how cold is something below absolute zero?

Apparently objects at a neg temps behave as if they were hotter than objects at any positive temps. source

Hmm, interesting...

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