# Quantum Gas Temperature Drops Below Absolute Zero **URL:** \ **Category:** In My Humble Opinion\ **Created:** [January 4, 2013, 5:05pm UTC](https://boards.straightdope.com/t/quantum-gas-temperature-drops-below-absolute-zero/646078 "2013-01-04T17:05:44Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![drewtwo99](https://avatars.discourse-cdn.com/v4/letter/d/d07c76/32.png) [@drewtwo99](https://boards.straightdope.com/u/drewtwo99)\ **Post date:** [January 4, 2013, 5:05pm UTC](https://boards.straightdope.com/t/quantum-gas-temperature-drops-below-absolute-zero/646078/1 "2013-01-04T17:05:44Z")
[Article Here](http://www.wired.com/wiredscience/2013/01/below-absolute-zero/) Is this a major scientific discovery? Or is this just some vague quantum physics thing that doesn’t really change any paradigms or contribute much. The article is woefully vague on what it even means to really be below absolute zero, other than that it is actually a higher energy state. So… can someone break this down for me? ---
**Author:** ![QuickSilver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quicksilver/32/7832_2.png) [@QuickSilver](https://boards.straightdope.com/u/QuickSilver)\ **Post date:** [January 4, 2013, 5:35pm UTC](https://boards.straightdope.com/t/quantum-gas-temperature-drops-below-absolute-zero/646078/2 "2013-01-04T17:35:04Z")
I read about this in The Disappearing Spoon. The author stated that noble gasses at sufficiently low temps will transition to liquid form, change from insulators to super conductors and behave in this manner - flowing up a vertical surface in seeming defiance to gravity. Unfortunately the author didn’t go into any more details. So yeah, it would be interesting to know more. ---
**Author:** ![Simplicio](https://avatars.discourse-cdn.com/v4/letter/s/c37758/32.png) [@Simplicio](https://boards.straightdope.com/u/Simplicio)\ **Post date:** [January 4, 2013, 6:14pm UTC](https://boards.straightdope.com/t/quantum-gas-temperature-drops-below-absolute-zero/646078/3 "2013-01-04T18:14:00Z")
Its not temperature in the usual sense (the average kinetic energy), which indeed can never be negative. Its in the thermodynamic sense, the derivative of energy with entropy. So they made a system whose entropy decreases with increasing energy. The usual way of doing this is creating a system where there are limited numbers of states at high energies, so that by increasing the average energy, you force more particles into a smaller number of available states. More of a stat-mech thing then a quantum thing, at least as far as the theory goes. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [January 4, 2013, 7:02pm UTC](https://boards.straightdope.com/t/quantum-gas-temperature-drops-below-absolute-zero/646078/4 "2013-01-04T19:02:09Z")
> [@QuickSilver](#): > > I read about this in The Disappearing Spoon. The author stated that noble gasses at sufficiently low temps will transition to liquid form, change from insulators to super conductors and behave in this manner - flowing up a vertical surface in seeming defiance to gravity. That’s [superfluidity](http://en.wikipedia.org/wiki/Superfluid). Not superconductivity. ---
**Author:** ![QuickSilver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quicksilver/32/7832_2.png) [@QuickSilver](https://boards.straightdope.com/u/QuickSilver)\ **Post date:** [January 4, 2013, 8:36pm UTC](https://boards.straightdope.com/t/quantum-gas-temperature-drops-below-absolute-zero/646078/5 "2013-01-04T20:36:30Z")
> [@Der\_Trihs](#): > > That’s [superfluidity](http://en.wikipedia.org/wiki/Superfluid). Not superconductivity. Superbad! 😃 ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [January 4, 2013, 9:29pm UTC](https://boards.straightdope.com/t/quantum-gas-temperature-drops-below-absolute-zero/646078/6 "2013-01-04T21:29:38Z")
> [@Simplicio](#): > > Its not temperature in the usual sense (the average kinetic energy), which indeed can never be negative. Its in the thermodynamic sense, the derivative of energy with entropy. So they made a system whose entropy decreases with increasing energy. > > The usual way of doing this is creating a system where there are limited numbers of states at high energies, so that by increasing the average energy, you force more particles into a smaller number of available states. > > More of a stat-mech thing then a quantum thing, at least as far as the theory goes. Thermo wasn’t my best class, but that jibes with my understanding from reading one article. A good general intuitive understanding of temperature is how much energy atoms and molecules have to bounce around – the more energy, the higher temperature. But that’s not a very precise definition, so physicists came up with a precise definition of temperature that (for normal materials) matches the intuitive understanding\*. But remember any physics that talks about temperature is a tiny bit imprecise because it’s all about statistical averages, not basic foundations of physical law. Now someone has managed to set up a system where the intuitive understanding doesn’t match the physics definition. But it’s a very artificial situation that takes a whole lot of machinery, effort, and ridiculous cryogenic cooling to set up (and carefully drawing an imaginary line around parts of the system), so it really doesn’t say anything interesting or useful about the world. Maybe the engineering is impressive, but there’s no real new physics there as far as I can tell. ---
**Author:** ![pancakes3](https://avatars.discourse-cdn.com/v4/letter/p/ba9def/32.png) [@pancakes3](https://boards.straightdope.com/u/pancakes3)\ **Post date:** [January 4, 2013, 10:00pm UTC](https://boards.straightdope.com/t/quantum-gas-temperature-drops-below-absolute-zero/646078/7 "2013-01-04T22:00:02Z")
Isn’t the point of this discovery that these supercooled atoms reached nanokelvins, some lost enough energy to exhibit behaviors unexplained like “antipressure” where they were attracted rather than repulsive? I’d find that to be “new physics”-y. ---
**Author:** ![drewtwo99](https://avatars.discourse-cdn.com/v4/letter/d/d07c76/32.png) [@drewtwo99](https://boards.straightdope.com/u/drewtwo99)\ **Post date:** [January 5, 2013, 6:52am UTC](https://boards.straightdope.com/t/quantum-gas-temperature-drops-below-absolute-zero/646078/8 "2013-01-05T06:52:42Z")
Interesting. Thanks for the info all. Yes I never did very well in my stat mech classes… it was all so difficult for me. But I am familiar with the thermo definitions of temperature in regards to entropy and energy, so that helps clear things up.