Quantum gas goes below absolute zero

[rpm]

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 time1. 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.

http://www.nature.com/news/quantum-gas-goes-below-absolute-zero-1.12146

 

[Chemical]

Some more information on this : http://www.space.com/19127-atoms-colder-than-absolute-zero.html

New kinds of engines

Negative temperatures could be used to create heat engines — engines that convert heat energy to mechanical work, such as combustion engines — that are more than 100-percent efficient, something seemingly impossible. Such engines would essentially not only absorb energy from hotter substances, but also colder ones. As such, the work the engine performed could be larger than the energy taken from the hotter substance alone.

 

[bekdik]

Does this mean that entropy decreases in this system?

 

[Chemical]

Does this mean that entropy decreases in this system?

According to the article, yes.

Another odd consequence of negative temperatures has to do with entropy, which is a measure of how disorderly a system is. When objects with positive temperature release energy, they increase the entropy of things around them, making them behave more chaotically. However, when objects with negative temperatures release energy, they can actually absorb entropy.

 

[The_Unbeliever]

Can I have some of that? It is hot here, and I need something for an airconditioner.

 

[3WA]

The only thing I remember from first-year chemistry is now wrong.

 

[guest2013-1]

still no cure for cancer... ****!

 

[K3NS31]

I'll just leave this here:

http://mybroadband.co.za/vb/showthr...bsolute-Zero?p=9581016&viewfull=1#post9581016

 

[K3NS31]

The only thing I remember from first-year chemistry is now wrong.

So according to what I posted above - negative Kelvin is actually very hot. So don't worry, it's still impossible to get colder than zero Kelvin, as that would be the temp at which atoms don't vibrate, and you can't make things vibrate any less than "not moving at all"

Here's a really good simplification from the Reg comments (author: John Savard):

"Think of a plastic cylinder containing marbles.

If it just sits there, they're all at the bottom.

If you shake it back and forth a small distance, the marbles will bounce up and down. The faster you shake it, the more often a marble will hit the top of the cylinder.

You could work out a mathematical formula for how much it's being shook randomly based on the logarithm of the ratio between the density of marbles at the top and bottom. As the amount of random shaking approaches infinity, the number of marbles at the top and the bottom would approach equality.

Now jerk the whole cylinder down quickly instead of shaking it. The marbles will go to the top. So the formula will give a negative logarithm, but that means more than infinite shaking instead of less than no shaking."

 

[Picard]

The only thing I remember from first-year chemistry is now wrong.

You're like the Stig from Top Gear ...

He knows only 2 facts about ducks ... and both of them are wrong.