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Sventek
05-01-2013, 11:55 AM
Is actually hot, apparently: Boffins create quantum gas with temperature BELOW absolute zero • The Register (http://www.theregister.co.uk/2013/01/05/quantum_gas_below_absolute_zero/)

truewheel
05-01-2013, 12:03 PM
"Boffins at the Ludwig Maximilian University in Munich, Germany have literally turned the Kelvin scale on its head, having produced a quantum gas with a temperature below absolute zero"

and


"Note that this doesn't mean the resulting system is actually cold, however. Nothing can be colder than absolute zero, which is a theoretical state at which particles have no energy at all. On the contrary, a system with a sub-zero absolute temperature is actually hotter (http://www.sciencedaily.com/releases/2013/01/130104143516.htm) than the same system at any positive temperature"

I iz confused.

Stu
05-01-2013, 12:06 PM
Best wait for the actual article in Science.

SIKYSA
05-01-2013, 12:12 PM
That's pretty.... 'cool.'

Ha.

Wedge
05-01-2013, 12:14 PM
If anyone's interested, I highly recommend this documentary on previous efforts.
Absolute Zero | Watch Free Documentary Online (http://topdocumentaryfilms.com/absolute-zero/)

Some really interesting stuff around 1 hour 13 in.

g0zer
05-01-2013, 12:35 PM
interesting idea

sounds like they have a jar (closed system with respect to matter) containing some potassium atoms in gaseous phase at close to 0K then they compress the atoms with their clever laser EM field wizardry, which leaves a relative vacuum everywhere else in the jar where the atoms are not compressed.

i assume they are manipulating http://upload.wikimedia.org/math/5/2/0/5205e29e7201a0b009466036b40a34a6.png

T = temp
S = entropy

so the mean T of the jar is 0.1K (or whatever it is) then they frig with the systems entropy by moving all the atoms so they are not evenly distributed throughout the jar which reduces local entropy (local to the condensed atoms). everywhere else in the jar temperature must drop to compensate for the rise in entropy to balance the equation and they have managed to set their starting conditions so this method can achieve conditions implying negative kelvin.


"Note that this doesn't mean the resulting system is actually cold, however. Nothing can be colder than absolute zero, which is a theoretical state at which particles have no energy at all. On the contrary, a system with a sub-zero absolute temperature is actually hotter (http://www.sciencedaily.com/releases/2013/01/130104143516.htm) than the same system at any positive temperature"

I iz confused.

i dont know what they mean by that either its been over 20y since i did 1st principles on temperature, will need to do some refreshing when i have more time to understand what they mean.

Rorschach
05-01-2013, 01:42 PM
interesting idea

sounds like they have a jar (closed system with respect to matter) containing some potassium atoms in gaseous phase at close to 0K then they compress the atoms with their clever laser EM field wizardry, which leaves a relative vacuum everywhere else in the jar where the atoms are not compressed.

i assume they are manipulating http://upload.wikimedia.org/math/5/2/0/5205e29e7201a0b009466036b40a34a6.png

T = temp
S = entropy

so the mean T of the jar is 0.1K (or whatever it is) then they frig with the systems entropy by moving all the atoms so they are not evenly distributed throughout the jar which reduces local entropy (local to the condensed atoms). everywhere else in the jar temperature must drop to compensate for the rise in entropy to balance the equation and they have managed to set their starting conditions so this method can achieve conditions implying negative kelvin.By distributing the K atoms evenly they're actually increasing entropy though. If the temperature decreases, they should clump together and increase entropy (presumably) as entropy generally increases with temperature, so by moving them further apart you're increasing the disorder/entropy. Having a read through the article now though so could have my wires crossed a bit

Rorschach
05-01-2013, 01:49 PM
Also, looks like they're manipulating the Gibbs Energy. By decreasing entropy (S) they have to increase temperature (T) to maintain the relationship in the Gibbs Free Energy equation dG=-TdS

Phildo
05-01-2013, 01:53 PM
Old news.

Everyone knows that if you piss off the right woman enough, you'll get a stare back that is way colder than zero degrees Kelvin.

g0zer
05-01-2013, 06:06 PM
Nothing can be colder than absolute zero, which is a theoretical state at which particles have no energy at all. On the contrary, a system with a sub-zero absolute temperature is actually hotter (http://www.sciencedaily.com/releases/2013/01/130104143516.htm) than the same system at any positive temperature"


is what they are saying, is that 0K is where atomic motion ceases and when you dip into negative temperatures atomic motion begins again and that motion is greater than a commensurate + value of temperature? if so it makes no sense to me.

Rorschach
05-01-2013, 06:18 PM
Re-read the article. Now makes even less sense to me!

Chaderotti
06-01-2013, 11:48 AM
I read it once then thought I had a grip on it.
Spoke to a mate about it and nope.

thro
06-01-2013, 01:54 PM
Will negative temperature affect time?

mr_andersen
07-01-2013, 01:42 AM
"This strange behavior has everything to do with how energy is spread throughout the atoms in a gas known as the ‘Boltzmann distribution’. A gas at any temperature will have different amounts of energy spread amongst its atoms. In a gas that is cooled, the majority of the particles will have low energy states although a few will have higher energy states."

"When the Kelvin temperatures become negative in the ultracooled gas, the distributions of energy is the opposite way round so that most of the particles have very high energy states while very few have low ones. In this case, the Boltzmann distribution is said to be ‘inverted’ so that the normal state of affairs is reversed."

Beyond 'absolute zero' temperatures get hotter | TG Daily (http://www.tgdaily.com/general-sciences-features/68525-beyond-absolute-zero-temperatures-get-hotter)

So the case where there are more particles in a high energy state than low energy state means the system is hotter than infinity Kelvin and hence is defined as negative temperature.

Arwon
07-01-2013, 07:07 AM
That's pretty.... 'cool.'

Ha.

actually its not........

absolute zero by definition is when all molecular activity stops. So its basically impossible to read with current devices.

SIKYSA
07-01-2013, 07:37 AM
actually its not........

absolute zero by definition is when all molecular activity stops. So its basically impossible to read with current devices.

Dammit.

Para045
07-01-2013, 09:12 AM
That's pretty.... 'cool.'

Ha.

I was actually expecting a "Cool Story Bro" from someone :rolleyes: :lol:

66
07-01-2013, 10:07 AM
Whilst much of this is admittedly above my head, isn't it a quite forward concept that less than absolute zero would be a higher yield? Sure in the wrong direction, but magnitude is magnitude, it can't be negative. Hence the term "absolute" being used in the first place.