Personally, I love that the whole of thermodynamics including the third law has been derived from more fundamental principles. To prove the third law, the physicists used ideas from computer science and quantum information theory. There, a common problem is to determine the amount of resources required to perform a certain task. When applied to cooling, the question becomes how much work must be done and how large must the cooling reservoir be in order to cool an object to absolute zero 0 Kelvin, The physicists showed that cooling a system to absolute zero requires either an infinite amount of work or an infinite reservoir.
This finding is in agreement with the widely accepted physical explanation of the unattainability of absolute zero: As the temperature approaches zero, the system's entropy disorder approaches zero, and it is not possible to prepare a system in a state of zero entropy in a finite number of steps.
The new result led the physicists to a second question: If we can't reach absolute zero, then how close can we get with finite time and resources?
It turns out that the answer is closer than might be expected. The scientists showed that lower temperatures can be obtained with only a modest increase of resources. Yet they also showed that there are limits here, as well. For example, a system cannot be cooled exponentially quickly, since this would result in a negative heat capacity , which is a physical impossibility.
One of the nice features of the new proof is that it applies not only to large, classical systems which traditional thermodynamics usually deals with , but also to quantum systems and to any conceivable type of cooling process.
For this reason, the results have widespread theoretical implications. Cooling to very low temperatures is a key component in many technologies, such as quantum computers, quantum simulations, and high-precision measurements. Understanding what it takes to get close to absolute zero could help guide the development and optimization of future cooling protocols for these applications. Explore further. More from Other Physics Topics. Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page.
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The information you enter will appear in your e-mail message and is not retained by Phys. You can unsubscribe at any time and we'll never share your details to third parties. From the engineer's perspective To cool something to zero kelvin, first you'll need something that is cooler than zero kelvin.
Edit 2 : I've got an issue with the 'no molecular motion' notion that I seem to find everywhere including Ivan's fantastic answer but I can't seem to get cleared. At absolute zero, all molecular motion stops.
As we decrease the temperature, the vibration decreases and decreases until, at absolute zero, there is a minimum amount of motion that atoms can have, but not zero. Remember that when a crystal is cooled to absolute zero, the atoms do not stop moving, they still 'jiggle'. If they stopped moving, we would know were they were and that they had they have zero motion, and that is against the Uncertainity Principle.
We cannot know where they are and how fast they are moving, so they must be continually wiggling in there! So, can anyone account for Feynman's claim as well? To the not-so-hardcore student of physics that I am high-schooler here , his argument seems quite convincing. There was a story in my days about a physical chemist who was asked to explain some effect, illustrated by a poster on the wall.
He did that, after which someone noticed that the poster was hanging upside down, so the effect appeared reversed in sign. Undaunted, the guy immediately explained it the other way around, just as convincingly as he did the first time. Cooking up explanations on the spot is a respectable sport, but your teacher went a bit too far. What's with that Charles' law? See, it is a gas law; it is about gases. And even then it is but an approximation.
To make it exact, you have to make your gas ideal, which can't be done. As you lower the temperature, all gases become less and less ideal. And then they condense, and we're left to deal with liquids and solids, to which the said law never applied, not even as a very poor approximation. Appealing to this law when we are near the absolute zero is about as sensible as ruling out certain reaction mechanism on the grounds that it requires atoms to move faster than allowed by the road speed limit in the state of Hawaii.
The energy argument is even more ridiculous. We don't have to remove all energy, but only the kinetic energy. All that being said, there is no physical law forbidding the existence of matter at absolute zero. It's not like its existence will cause the world to go down with error It's just that the closer you get to it, the more effort it takes, like with other ideal things ideal vacuum, ideally pure compound, crystal without defects, etc.
If anything, we're doing a pretty decent job at it. Using sophisticated techniques like laser cooling or magnetic evaporative cooling , we've long surpassed the nature's record in coldness. Absolute zero is a tricky concept, particularly once you start getting precise about it. Thermodynamics and quantum mechanics is a tricky business! I'll try to avoid the precise parts, and see if I can give you an answer which is more intuitive than a pile of equations.
The first question is what does it mean to "attain a temperature of absolute zero. In this context, we are interested in bulk objects that have a uniform temperature. We can quickly see that if there is any heat transfer between an object "at absolute zero" and any object not at absolute zero, then the first object will be warmed as thermal energy from the warmer object flows into it.
This mean our object at absolute zero can only remain there if it is in thermal isolation. There is no known way to do this especially when it comes to radiative heating , unless your object at absolute zero is completely surrounded by other objects at absolute zero. This forms a sort of tower of babel that eventually falls when some outside objects must be subjected to the 3K background radiation. Empty space is "warmer" than absolute zero.
What if we consider the world of non-equilibrium thermodynamics. This is the study of systems that are not currently at equilibrium. This is a strange place where some things can occur which don't make sense at first sight. One of them is negative temperatures. However, in non-equilibrium thermodynamics, we can consider strange compounds that are metastable. You can think of them like a ball perfectly at the top of a smooth hill.
If the ball is tapped in any direction, it will roll down the hill to the bottom. However, at the top, it can theoretically stay motionless temporarily. We have corralled atoms into traps, and cooled them until they were very very cold a few billionths of a kelvin. Then, we flipped a switch which turned the trap around.
Suddenly a position that was very stable became an unstable equilibrium. If you run the math on this weird state, it turns out that this implies a negative temperature!
Now this would suggest that, since a temperature went from positive to negative, it must have crossed through 0K, proving that we created something at absolute zero. However, this is not the case. What actually happens is that the temperature rushes towards positive infinity, reaches a discontinuity, and then wraps around to negative infinity.
It then approaches its negative temperature from negative infinity. So even in this case, we can't reach absolute zero. Quantum mechanics also poses an issue in that you could never prove you attained absolute zero if you tried. Thermal energy is kinetic energy, which is related to momentum.
Let's say you found a hypothetical approach to reach absolute zero. When you go to prove your findings, you must prove the momentum is also 0. However, by proving that to be true, with no error, the uncertainty principle states that you can know nothing about the position of those particles. They might be anywhere in the universe! Leaving quantum mechanics aside it gives me a headache the second law of thermodynamics prevents absolute zero from being reached in practice.
To cool something down, its heat must be transferred to something cooler than it. Since nothing can be cooler than absolute zero, one cannot cool something to absolute zero. Your teacher's explanation is, as Ivan points out, based on the ideal gas law and there is no such thing as an ideal gas, especially not close to absolute zero.
The usual answer is that it's unattainable because absolute vacuum is unattainable because the ground state of spacetime itself has non-zero energy. This ground state occasionally condensing is what creates the virtual particles. Plus, apart from this fundamental reason of the lowest energy level of spacetime itself being non-zero, you have lots of neutrinos everywhere, which you can't really shield yourself from.
A massive galaxy-sized sphere of gold might do that to some degree, but unfortunately you can't build such a thing because of general relativity i. Numbers extremely close to zero are just as hard to get to as their inverse, i.
Absolute zero can definitely exists see the later edit , and there is at least one theory, that says that absolute zero will kind of be the norm in the universe at one point. The second rule is known as the unattainability principle, which states that absolute zero is physically unreachable because no system can reach zero entropy.
The first rule was proposed by German chemist Walther Nernst in , and while it earned him a Nobel Prize in Chemistry, heavyweights like Albert Einstein and Max Planck weren't convinced by his proof, and came up with their own versions of the cooling limit of the Universe.
This prompted Nernst to double down on his thinking and propose the second rule in , declaring absolute zero to be physically impossible. Together, these rules are now acknowledged as the third law of thermodynamics, and while this law appears to hold true, its foundations have always seemed a little rocky - when it comes to the laws of thermodynamics , the third one has been a bit of a black sheep.
In order to test how robust the assumptions of the third law of thermodynamics actually are in both classical and quantum systems , Masanes and his colleague Jonathan Oppenheim decided to test if it is mathematically possible to reach absolute zero when restricted to finite time and resources.
Masanes compares this act of cooling to computation - we can watch a computer solve an algorithm and record how long it takes, and in the same way, we can actually calculate how long it takes for a system to be cooled to its theoretical limit because of the steps required to remove its heat. You can think of cooling as effectively 'shovelling' out the existing heat in a system and depositing it into the surrounding environment. How much heat the system started with will determine how many steps it will take for you to shovel it all out, and the size of the 'reservoir' into which that heat is being deposited will also limit your cooling ability.
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