below absolute zero

[dragon]

Hum cool

Physicists have created a quantum gas capable of reaching temperatures below absolute zero, paving the way for future quantum inventions.


The chilly substance was composed of potassium atoms which were held in a lattice arrangement using a combination of lasers and magnetic fields. According to a news report in the journal Nature, by tweaking the magnetic fields the research team were able to force the atoms to attract rather than repel one another and reveal the sub-absolute zero properties of the gas.

“This suddenly shifts the atoms from their most stable, lowest-energy state to the highest possible energy state, before they can react,” said Ulrich Schneider of the Ludwig Maximilian University in Munich to Nature. “It’s like walking through a valley, then instantly finding yourself on the mountain peak.”

Schneider’s findings were published Jan. 3 in Science.


Previously absolute zero was considered to be the theoretical lower limit of temperature as temperature correlates with the average amount of energy of the substance’s particles. At absolute zero particles were thought to have zero energy.

Moving into the sub-absolute zero realm, matter begins to display odd properties. Clouds of atoms drift upwards instead of down, while the atomic matrix’s ability to resist collapsing in on itself echoes the forces causing the universe to expand outwards rather than contracting under the influence of gravity.

The ability to produce a relatively stable substance at several billionths of a Kelvin below absolute zero will allow physicists to better study and understand this curious state, possibly leading to other innovations.

“This may be a way to create new forms of matter in the laboratory,” said Wolfgang Ketterle, a Nobel laureate at MIT, commenting in Nature on the results.

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[jwl]

Sounds interesting, but isn't a gas meant to occupy zero volume at absolute zero? What does it occupy at below that? Negative volume?

[AMX]

Sounds interesting, but isn't a gas meant to occupy zero volume at absolute zero?

Only under Charle's law, which assumes constant pressure.

Since it is impossible to maintain constant pressure when the volume approaches zero, Charle's law does not apply.

[Simon_Jester]

Er... I'm just going to say, "negative temperature" is a complicated idea. At room temperature when we talk about 'hot' or 'cold' we're usually thinking of something like energy density- pumping more energy into the particles that make up a system makes them move around more and gets them hotter.

At near absolute zero, you have to be careful talking about such things, because temperature is formally defined as a relation of entropy and energy. A "negative temperature" would most easily be obtained by creating a system that (under certain conditions) gets less entropic when you pump more energy into it. Which is mostly a matter of quirks and details about how the system operates, not about some kind of absolute, abstract universal "this is the temperature here and it is negative eight degrees Kelvin" thing.

[Questor]

Er... I'm just going to say, "negative temperature" is a complicated idea. At room temperature when we talk about 'hot' or 'cold' we're usually thinking of something like energy density- pumping more energy into the particles that make up a system makes them move around more and gets them hotter.

At near absolute zero, you have to be careful talking about such things, because temperature is formally defined as a relation of entropy and energy. A "negative temperature" would most easily be obtained by creating a system that (under certain conditions) gets less entropic when you pump more energy into it. Which is mostly a matter of quirks and details about how the system operates, not about some kind of absolute, abstract universal "this is the temperature here and it is negative eight degrees Kelvin" thing.

Which, according to a more detailed article, is exactly what they did.

http://www.theregister.co.uk/2013/01/05 ... lute_zero/

[Molyneux]

Er... I'm just going to say, "negative temperature" is a complicated idea. At room temperature when we talk about 'hot' or 'cold' we're usually thinking of something like energy density- pumping more energy into the particles that make up a system makes them move around more and gets them hotter.

At near absolute zero, you have to be careful talking about such things, because temperature is formally defined as a relation of entropy and energy. A "negative temperature" would most easily be obtained by creating a system that (under certain conditions) gets less entropic when you pump more energy into it. Which is mostly a matter of quirks and details about how the system operates, not about some kind of absolute, abstract universal "this is the temperature here and it is negative eight degrees Kelvin" thing.

Which, according to a more detailed article, is exactly what they did.

http://www.theregister.co.uk/2013/01/05 ... lute_zero/

Trick of definitions (and the pitfalls of applying laymans' definitions to extremely technical experiments) aside, this still blew my mind a little bit when I read it. I hadn't known that absolute negative temperatures were possible, much less achievable in modern-day labs.

[Prannon]

What blows my mind is the analogy made to the expansion of the universe, which isn't entirely explained yet, when particles are induced to reach this temperature. I'm curious to know if this discovery will lead to further understanding of that phenomenon. Given the huge scale of the universe, I wouldn't be surprised if something this small could be extrapolated.