Cold Hands, Warm Heart
May 8, 2014 11:56 AM Subscribe
"According to the physical meaning of temperature, the temperature of a gas is determined by the chaotic movement of its particles – the colder the gas, the slower the particles. At zero kelvin (minus 273 degrees Celsius) the particles stop moving and all disorder disappears. Thus, nothing can be colder than absolute zero on the Kelvin scale. Physicists at the Ludwig-Maximilians University Munich and the Max Planck Institute of Quantum Optics in Garching have now created an atomic gas in the laboratory that nonetheless has negative Kelvin values. These negative absolute temperatures have several apparently absurd consequences: although the atoms in the gas attract each other and give rise to a negative pressure, the gas does not collapse – a behaviour that is also postulated for dark energy in cosmology. Supposedly impossible heat engines such as a combustion engine with a thermodynamic efficiency of over 100% can also be realised with the help of negative absolute temperatures."
"Matter at negative absolute temperature has a whole range of astounding consequences: with its help, one could create heat engines such as combustion engines with an efficiency of more than 100%. This does not mean, however, that the law of energy conservation is violated. Instead, the engine could not only absorb energy from the hotter medium, and thus do work, but, in contrast to the usual case, from the colder medium as well."
"Matter at negative absolute temperature has a whole range of astounding consequences: with its help, one could create heat engines such as combustion engines with an efficiency of more than 100%. This does not mean, however, that the law of energy conservation is violated. Instead, the engine could not only absorb energy from the hotter medium, and thus do work, but, in contrast to the usual case, from the colder medium as well."
This post was deleted for the following reason: Double. -- mathowie
Reading the article, apparently this negative Kelvin temperature is in actuality HOTTER than absolute zero, and it has negative values due to... um... reasons. Uh. I'll keep reading.
posted by showbiz_liz at 12:03 PM on May 8, 2014 [1 favorite]
posted by showbiz_liz at 12:03 PM on May 8, 2014 [1 favorite]
“The inverted Boltzmann distribution is the hallmark of negative absolute temperature; and this is what we have achieved,” says Ulrich Schneider. “Yet the gas is not colder than zero kelvin, but hotter,” as the physicist explains: “It is even hotter than at any positive temperature – the temperature scale simply does not end at infinity, but jumps to negative values instead.”posted by XMLicious at 12:03 PM on May 8, 2014 [1 favorite]
...
At first sight it may sound strange that a negative absolute temperature is hotter than a positive one. This is simply a consequence of the historic definition of absolute temperature, however; if it were defined differently, this apparent contradiction would not exist.
I'm gonna be honest here: I read the article and I absolutely 100% do not understand a word of it.
Seems pretty cool though!
posted by showbiz_liz at 12:05 PM on May 8, 2014
Seems pretty cool though!
posted by showbiz_liz at 12:05 PM on May 8, 2014
So, if I'm reading this correctly, ice cold is no longer cooler than being cool?
posted by silkyd at 12:10 PM on May 8, 2014 [10 favorites]
posted by silkyd at 12:10 PM on May 8, 2014 [10 favorites]
So is the fact that the article largely unreadable because it might be translated from German, or that it's 100% jibberish? The gist of what I read was that they raised the thermal energy of the particles so high that they "overflowed" into negative territory.
One, if it were true they achieved some sort of "maximum temperature", that would require a ridiculous amount of energy; it would probably be more than the Sun outputs in a year (and I might be vastly understating the total amount). Second of all, the idea seems kind of ridiculous in its face. That doesn't necessarily mean that it's not possible or true. It's just that in this particular case I feel like my BS detector i going off at full tilt right now.
posted by surazal at 12:10 PM on May 8, 2014 [1 favorite]
One, if it were true they achieved some sort of "maximum temperature", that would require a ridiculous amount of energy; it would probably be more than the Sun outputs in a year (and I might be vastly understating the total amount). Second of all, the idea seems kind of ridiculous in its face. That doesn't necessarily mean that it's not possible or true. It's just that in this particular case I feel like my BS detector i going off at full tilt right now.
posted by surazal at 12:10 PM on May 8, 2014 [1 favorite]
A more general, but less intuitive, definition of temperature T is T = (∂E/∂S)V,N (or 1/(∂S/∂E)V,N), the increase in internal energy E with increasing entropy S at constant volume V and amount of stuff N. If you can make a system whose entropy decreases with increasing energy (or vice versa), it effectively has a negative absolute temperature. That's opposite to all bulk materials familiar to us, in which entropy increases as we add energy, and that appears to be what's being exploited here.
posted by Mapes at 12:11 PM on May 8, 2014 [1 favorite]
posted by Mapes at 12:11 PM on May 8, 2014 [1 favorite]
My (rather limited) understanding is that while the "negative" notation of the temperature in Kelvin is in fact merely a consequence of how temperature is defined this nevertheless constitutes a somewhat freaky state of matter that behaves in ways very different from matter at "normal" temperatures.
Also, I think this explains icy hot patches.
posted by Hairy Lobster at 12:11 PM on May 8, 2014
Also, I think this explains icy hot patches.
posted by Hairy Lobster at 12:11 PM on May 8, 2014
we were just trying to turn on Big Head Mode and messed up the Gameshark code, I think Ulrich put in 1F at the end instead of FF, in any case all the music sped up super fast and temperatures are going negative and it is no longer possible to die
posted by theodolite at 12:12 PM on May 8, 2014 [5 favorites]
posted by theodolite at 12:12 PM on May 8, 2014 [5 favorites]
however; if it were defined differently, this apparent contradiction would not exist.
Oh, I see, it's the old Kenobian "from a certain point of view I didn't lie to you" argument.
posted by flaterik at 12:15 PM on May 8, 2014
Oh, I see, it's the old Kenobian "from a certain point of view I didn't lie to you" argument.
posted by flaterik at 12:15 PM on May 8, 2014
So, if I'm reading this correctly, ice cold is no longer cooler than being cool?
That hasn't been true since the early 80s.
posted by The 10th Regiment of Foot at 12:15 PM on May 8, 2014
That hasn't been true since the early 80s.
posted by The 10th Regiment of Foot at 12:15 PM on May 8, 2014
Ok, physicist here; I haven't read the article, but I can maybe clear up some of the confusion about negative temperature.
Basically, by historical accident, we use T instead of beta to measure temperature. Now, beta is just 1/T with a constant thrown in to make the units nicer. So now, the temperature scale goes from really high positive beta (near absolute zero T) to low positive beta (high T) all the way to negative beta (negative T). The whole thing is upside down (high beta is colder), but the transition near beta=0 is--hopefully--less mysterious.
posted by lozierj at 12:16 PM on May 8, 2014 [4 favorites]
Basically, by historical accident, we use T instead of beta to measure temperature. Now, beta is just 1/T with a constant thrown in to make the units nicer. So now, the temperature scale goes from really high positive beta (near absolute zero T) to low positive beta (high T) all the way to negative beta (negative T). The whole thing is upside down (high beta is colder), but the transition near beta=0 is--hopefully--less mysterious.
posted by lozierj at 12:16 PM on May 8, 2014 [4 favorites]
surazal: "It's just that in this particular case I feel like my BS detector i going off at full tilt right now."
That was my first reaction as well but the Max Planck Institutes are not really known to be hotbeds of science news BS.
Anyhow, I'll stop threadsitting now.
posted by Hairy Lobster at 12:16 PM on May 8, 2014 [1 favorite]
That was my first reaction as well but the Max Planck Institutes are not really known to be hotbeds of science news BS.
Anyhow, I'll stop threadsitting now.
posted by Hairy Lobster at 12:16 PM on May 8, 2014 [1 favorite]
These articles always remind me why I really really did not enjoy stat mech.
posted by kiltedtaco at 12:18 PM on May 8, 2014
posted by kiltedtaco at 12:18 PM on May 8, 2014
We've done this before. I wrote out a long description of negative temperature, what it means, and why it's a perfectly cromulent description of certain unusual physical systems, and does not break physics. Read it here.
posted by physicsmatt at 12:18 PM on May 8, 2014 [8 favorites]
posted by physicsmatt at 12:18 PM on May 8, 2014 [8 favorites]
A while ago I made up a way to explain where all the science fiction "elements" are on the periodic table -- there was an elaborate explanation as to how atoms could have a fractional number of protons, opening up the periodic table to a third dimension.
This kind of sounds similar on the face of it. :\
posted by edheil at 12:20 PM on May 8, 2014
This kind of sounds similar on the face of it. :\
posted by edheil at 12:20 PM on May 8, 2014
physicsmatt, thanks. The article broke my brain. Your explanation was much more understandable
posted by zarq at 12:21 PM on May 8, 2014
posted by zarq at 12:21 PM on May 8, 2014
So the article, and its pullquote in the FPP, starts by describing one definition of temperature, but then introduces a concept of negative temperature that only applies when using a different definition of temperature.
This is interesting but not nearly as interesting as they are making it sound.
posted by rocket88 at 12:21 PM on May 8, 2014 [1 favorite]
This is interesting but not nearly as interesting as they are making it sound.
posted by rocket88 at 12:21 PM on May 8, 2014 [1 favorite]
When this was announced last year, I tried my hand at explaining "negative temperature" through a convoluted analogy, with middling success; the results are here. Short answer: this wasn't anything new, and while real, the hype was overblown. Still very interesting, though.
On preview: physicsmatt beat me to the punch!
posted by freelanceastro at 12:22 PM on May 8, 2014
On preview: physicsmatt beat me to the punch!
posted by freelanceastro at 12:22 PM on May 8, 2014
Oh, man. Totally misread the year as 2014.
FPP fail :(
I guess it's a double then?
*sigh*
*hides in corner*
*cries*
posted by Hairy Lobster at 12:25 PM on May 8, 2014
FPP fail :(
I guess it's a double then?
*sigh*
*hides in corner*
*cries*
posted by Hairy Lobster at 12:25 PM on May 8, 2014
Are the promises of >100% thermodynamic efficiency even real? I suspect the answer is a resounding 'no' based on the misleading nature of the rest of the article.
posted by rocket88 at 12:25 PM on May 8, 2014
posted by rocket88 at 12:25 PM on May 8, 2014
rocket88: No, they are not real. From a technical point of view, maybe, but you're not gonna get something for nothing with this kind of system.
posted by freelanceastro at 12:27 PM on May 8, 2014
posted by freelanceastro at 12:27 PM on May 8, 2014
We've done this before. I wrote out a long description of negative temperature, what it means, and why it's a perfectly cromulent description of certain unusual physical systems, and does not break physics. Read it here.
Eventually, your comments will be numerous enough to comprise a textbook and you will be rich!
Or, well, I'll be smarter anyway. Thanks much!
posted by Pogo_Fuzzybutt at 12:30 PM on May 8, 2014
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pepsi bluecold fusionposted by j_curiouser at 12:01 PM on May 8, 2014