Cooling To Absolute Zero Mathematically Outlawed After a Century (newscientist.com)

After more than 100 years of debate -- which at one point even elicited interest from Albert Einstein and Max Planck, physicists have finally offered up mathematical proof of the third law of thermodynamics, which states that a temperature of absolute zero cannot be physically achieved because it's impossible for the entropy (or disorder) of a system to hit zero. While scientists have long suspected that there's an intrinsic 'speed limit' on the act of cooling in our Universe that prevents us from ever achieving absolute zero (0 Kelvin, -273.15 C, or -459.67 F), this is the strongest evidence yet that our current laws of physics hold true when it comes to the lowest possible temperature. From a report on NewScientist: Now Jonathan Oppenheim and Lluis Masanes at University College London have mathematically derived the unattainability principle and placed limits on how fast a system can cool, creating a general proof of the third law. "In computer science, people ask this question all the time: how long does it take to perform a computation?" says Oppenheim. "Just as a computing machine performs a computation, a cooling machine cools a system." So, he and Masanes asked how long it takes to get cold. Cooling can be thought of as a series of steps: heat is removed from the system and dumped into the surrounding environment again and again, and each time the system gets colder. How cold depends on how much work can be done to remove the heat and the size of the reservoir for dumping it. By applying mathematical techniques from quantum information theory, they proved that no real system will ever reach 0 kelvin: it would take an infinite number of steps. Getting close to absolute zero is possible, though, and Masanes and Oppenheim quantified the steps of cooling, setting speed limits for how cold a given system can get in finite time.

Comments

Wow

[Anonymous Coward]

Thats really cool!

Re:Wow

[Anonymous Coward]

You're lucky, I couldn't quite finish reading it...

Re:Wow

[SeaFox]

Thats really cool!

Not as cool as it theoretically could be.

Re:Wow

[syntotic]

Hotly inspired a few days ago?

Zeno's Paradox

[Oxygen99]

Isn't this just Zeno's paradox applied to really good fridges?

Re:Zeno's Paradox

[swillden]

Isn't this just Zeno's paradox applied to really good fridges?

It would be if each additional half-distance traveled required more work and more time than was expended to travel the first half.

Re:Zeno's Paradox

[Daetrin]

I had the same thought, and this is actually the rare case where it might apply!

In real life as far as movement goes you're never actually trying to get to an exact point. For one thing, because of uncertainty in measurements you can't ever get to an _exact_ point. You can't even tell _exactly_ where something is. On top of that (literally in this case) objects take up space, even individual atoms, so if you move an object to a point it won't be exactly at that point, it will be overlapping that point to some degree. So no matter how precise you're trying to be you're always overshooting at least a little bit. Which means that even ignoring the problem of calculus Xeno's paradox has a hole in it. You're never trying to get exactly to a point, you're actually trying to get to a little past the point and just stopping once you're close enough/sufficiently overlapping. It's effectively the same as starting out trying to run twice the distance, getting halfway, and declaring yourself done.

The difference in this case is twofold, one: there's no "past the point" you can aim for. The whole idea of absolute zero is that it's the lowest you can go. Two: they seem to be saying that there is no quanta of temperature. You can never remove the last bit, you can only remove a portion of what is there.

Assuming that the second part is correct (i'll leave the proof or disproof of that to actual scientists =) the first part makes it impossible to ever arrive at actual zero.

Re:Zeno's Paradox

[aicrules]

infinite steps means it would never actually reach 0 because there are always more steps. Genius....

Re:Zeno's Paradox

[mark-t]

Actually, 0.999... *is* equal to 1.... in real life. They are simply two different ways of describing the exact same number.

I'll give you benefit of the doubt and assume that you are not somebody who thinks that they have a clear understanding of why they should be different and would ignore any proofs to the contrary, but here is one of probably a dozen proofs that should be readily understandable by anyone who knows how to compute the decimal expansion of a fraction.

Consider that the decimal expansion of 1/9 is 0.111.... repeating forever, and it is clear that if you multiply this decimal expansion of 1/9 by any one-digit number, there are no carryovers in the multiplication, so 0.111... multiplied by 9 would therefore equal 0.999... repeating forever, but we also know that 1/9 multiplied by 9 is 1, and thus 0.999... must be equal to 1... They look different, but they are actually the same. This is not simply the result of some series converging on the number 1, it literally is the exact same number. It is simply an alternative representation that arises out of the ways that we are permitted to describe numbers in mathematics.

Re:Zeno's Paradox

[Anonymous Coward]

That's was what people thought in the 5th century BC, but it turns out that you can actually reach 0 if the time taken by each step forms a convergent series.

Re: Zeno's Paradox

[Lisandro]

0.9999... Is exactly 1.

Re:Zeno's Paradox

[K. S. Kyosuke]

Acoolees and the tort-ice?

Re:Zeno's Paradox

[thinkwaitfast]

Hey! I'm a real physicist writing from my own cozy house. I just sit back and eat popcorn through most of these things....

Re:Zeno's Paradox

[ChrisMaple]

You are denying that an open interval and a closed interval are different things.

Re:Zeno's Paradox

[Lisandro]

There are several ways of proving 0.999... = 1. Two very easy ones:

1) If 1/3 is 0.333..., what is 1/3 * 3?
2) What is the difference between 1 and 0.999... ?

Re:Zeno's Paradox

[Agent0013]

Like getting to the end of a race track cannot ever happen. To get to the end you first have to get 1/2 the way there. To get to the half way point, you first must get to the 1/4 point. To get there, you must first get to the 1/8 point. You have an infinite number of steps to get from the start to the end so there are always more steps between and you can never complete it. This is one of Zeno's Paradoxes and it is shown to be false basically because of calculus.

So saying you cannot complete an infinite number of steps in a finite amount of time is wrong!

Re: Zeno's Paradox

[hackwrench]

You appear to be confusing numbers with physics. I suppose however somone could come up with a universal universe editor that works like a rom hacking tool and edit in an object with the property of being at absolute zero, but conventional methods of cooling things will not get an object to absolute zero

Re:Zeno's Paradox

[vux984]

Like getting to the end of a race track cannot ever happen. To get to the end you first have to get 1/2 the way there. To get to the half way point, you first must get to the 1/4 point. To get there, you must first get to the 1/8 point. You have an infinite number of steps to get from the start to the end so there are always more steps between and you can never complete it

This is one of Zeno's Paradoxes and it is shown to be false basically because of calculus.

"Basically because of calculus" is the most hand-wavy excuse. The REASON you can reach the end of a race track is that the time to complete 'each 1/2 step' converges to zero. What if we added some 'overhead' so the time per step didn't converge to zero... then what happens? Say we add the requirement that you stop for 0.1 seconds each time you traverse another "1/2 of the remainder", now how long will it take to cross the finish line?

Answer: You won't finish. Now it WILL take infinite time.

So saying you cannot complete an infinite number of steps in a finite amount of time is wrong!

If the iterations converge to requiring zero time to complete then maybe you can complete an infinite series of them in a finite amount of time. Otherwise... nope. Forget it.

Re: Zeno's Paradox

[rtb61]

You could get an object to absolute zero, you are unlikely to achieve by cooling but by forcing through stasis to cease to exist. Though of you cause it to cease to exist, has to ever really achieved absolute zero.

Re: Zeno's Paradox

[Daetrin]

So are you saying you can accurately measure a point to a precision greater than that of Planks length? I'm not a physicist so I can't say with any certainty one way or the other, but that seems unlikely to me given what i know about it.

Re:Zeno's Paradox

[Trogre]

Try to follow this:

1 / 3 = 0.333...
0.333... x 3 = 0.999...

(1 / 3) x 3 = 1

ergo 0.999... = 1

Re:Zeno's Paradox

[Altrag]

I'm pretty sure Zeno's paradox applies regardless of measurement precision. The problem is that, since you're assuming constant velocity, moving the first 50% takes 50% of the total time.. moving the next 25% takes 25% of the time and so forth. Basically you have two infinities "cancelling" each other out (which happens surprisingly/scarily often in physics!)

With the freezing, as I understand (and its well possible that I don't,) you remove 50% in one unit of time, then the next 25% in another equal unit of time and so on. The difference being that you only have one infinity to deal with (the number of temperature halvings) and therefore an impossibility.

Reaching light speed has similar issues. Every unit of additional energy you put toward your acceleration results in an ever-decreasing boost to velocity as you get closer and closer to c. Which makes you wonder if there's could be some temperature equivalent to Lorentz' transformations. (If there was, I assume smarter people than me would have noticed it by now of course.. but its fun to consider!)

Re: Zeno's Paradox

[Altrag]

Not always.

Though you need to get into some pretty advanced math before you'd care about number systems where 0.999... != 1.

Re:Zeno's Paradox

[haruchai]

Nice try but you pulled the V=5 completely out of your ass and it contradicts IV=4 since you defined I=0.9999999999....

Re: Zeno's Paradox

[mark-t]

You can easily prove that 1/9 = 0.111... using long division for the base step to get the first digit of the expansion, and apply proof by induction

Re:Zeno's Paradox

[Zeroko]

IV=4 & V=5 as Roman numerals (as is 0.999...=I)...the derivation appears to be a math pun of sorts.

Re:Zeno's Paradox

[mark-t]

I wasn't suggesting it was... only that the above poster's comment that 0.999... is not equal to 1 is false. The proof that they are the same is inconsequential to physics because the equality is not derived from any real world phenomenon.

Re: Zeno's Paradox

[mark-t]

Uh... no.

Re: Zeno's Paradox

[mark-t]

Do you have any specific reason for believing that is not how math works, or are you one of the aforementioned people who thinks that their inituive understanding math alone puts them in a position to dispute any well-reasoned (or even allegedly well-reasoned) conclusions without actually having rigorously studied it? If you see a flaw in the proof I gave, point it out... otherwise, you only come across as someone who is, to put it rather bluntly, too ignorant about the subject to even know what it is that you don't know.

Re:Zeno's Paradox

[david_thornley]

In real life, I type 1 and that's it. On the other hand, I could type 0.9999999, continuing the sequence until my fingers got tired, and it still wouldn't be equal to 1. Mathematically, what I'd get if I typed an infinite number of 9s is simple and understandable, but that can't be represented in the real world without additional notation (such as an ellipsis).

Re: Zeno's Paradox

[david_thornley]

If you're at an exact point with no uncertainty, you can't know anything about your momentum. Since there's limits to momentum in the physical Universe, you can't be at an exact point with no uncertainty.

Re: Zeno's Paradox

[david_thornley]

Which is why Heisenberg never wanted anyone to tell him the momentum of his car keys.

Re:Zeno's Paradox

[ArmoredDragon]

It would be if each additional half-distance traveled required more work and more time than was expended to travel the first half.

Then how do you travel half of the Plank length?

Re:Zeno's Paradox

[swillden]

It would be if each additional half-distance traveled required more work and more time than was expended to travel the first half.

Then how do you travel half of the Plank length?

You don't. When you're within a Planck length, your atoms are already interacting with the atoms of the target, i.e. you're already touching. Any further movement isn't movement toward the target, it's into it.

Re:Zeno's Paradox

[ArmoredDragon]

So then in effect, if you're one Planck length unit away, then moving half of the distance means you're there. Would that also be the same as saying if we're one Planck temperature unit away from zero entropy, then the next step, no matter how small, would be absolute zero? And if so, doesn't that mean we can reach absolute zero?

Re:Zeno's Paradox

[swillden]

So then in effect, if you're one Planck length unit away, then moving half of the distance means you're there.

No, if you're one Planck length away, you're already there.

Re:Zeno's Paradox

[ArmoredDragon]

Ok what about two then?

Re:Zeno's Paradox

[swillden]

Ok what about two then?

How about 10^20? 10^20 Planck lengths is the diameter of a proton. The atoms are interacting chemically and/or bouncing off one another long before you're even that close.

Re: Zeno's Paradox

[Bengie]

but V = 5

is wrong. V is 4.

0.999... = I (I = 1)
IV = 4 (1*4 = 4) (V = 4)
V = 4/I (4 = 4/1)
V = IR (4 = 1 * R) (R = 4)
I = V/R (1 = 4/4)
V = 4R/V (4 = 4*4/4)
R = V^2/4 (4 = 4^2/4)
but V = 5 (WRONG, it was defined as 4 by the second line)

But "Mr.Z of the LotFC" points out "IV=4 & V=5 as Roman numerals (as is 0.999...=I)...the derivation appears to be a math pun of sorts."

Re: Zeno's Paradox

[mark-t]

I think you may have intended then to respond to someone else... since the aforementioned proof you quote was not provided by myself.

Wrong!

[whoever57]

All they need to do is to heat it to below absolute zero and then let it warm up a little.

Re:Wrong!

[Anonymous Coward]

Nope.. .Still wrong.

As an atom spins it gives off infrared energy. The slower it spins, the less infrared energy it will give off also contracting in size.

Since EVERYTHING in the known universe gives off infrared energy, it is near impossible to shield infrared energy from reaching the atom and it is highly unlikely for it ever to reach absolute zero.

Absolute zero is the point that the atom will no longer spin. They are correct that absolute zero will never be attainable from an object of mass.
BUT...

The problem nobody talks about is that object of mass doesn't need to stay an object of mass. At absolute zero it will return to the energy that it was before it became mass, AND absolute zero is attained because photons do not give off heat.

But then again, it is no longer mass., so who cares?

Nathan

 

Re:Wrong!

[doctorfaustus]

I don't think so. If it has energy, then that energy can be transferred, and heat is the transfer of energy. Absolute zero is an energy-less state....

Re:Wrong!

[Anonymous Coward]

The only problem I have with your proposal is that you seem to be suggesting that the possession of some amount of temperature (enthalpy) by an atom is an intrinsic requirement to maintain the atom's existence.

I don't know of any mechanism that makes that possible, but regardless of the mechanism, would you expect this process to be symmetric? If so then to turn energy into matter (the reverse of what you wrote) then the process has to take place at a location with zero temperature, or, that once the atom has been created is starts its life without zero energy - but what stops this process from immediately reversing?

Since absolute zero has never been observed, yet there have been many examples observed of the exchange between matter and energy, in both directions, and under various conditions, I don't see how you can make the claim that absolute zero has some role to play in those processes.

Finally, I don't see how this theory can reconcile with Gibbs. What if the atom has zero enthalpy but what energy it possesses is all "assigned" to its entropy?

I guess as a prediction "matter decays into energy at absolute zero" could be either right or wrong, but for me it belongs in the same category as "black holes are wormholes to other universes".

Re:Wrong!

[omnichad]

The only problem I have with your proposal is that you seem to be suggesting that the possession of some amount of temperature (enthalpy) by an atom is an intrinsic requirement to maintain the atom's existence.

I think that is the core question that's raised. What is an atom?

I guess as a prediction "matter decays into energy at absolute zero" could be either right or wrong, but for me it belongs in the same category as "black holes are wormholes to other universes".

What energy? I'd think you have to entirely remove all energy from a closed system in order to reach absolute zero - no energy, no matter.

Re:Wrong!

[ChrisMaple]

Something doesn't seen right here. Isn't energy quantized? If so, then an inability to get to absolute zero (quantum state zero) means that quantum state number one is the lowest possible energy level. Wouldn't quantum state number one then be absolute zero?

What prohibits something from being at quantum state zero? If two things at quantum state #1 interact, might not one of them subsequently be at state zero and the other at state 2?

Does temperature actually have a meaning in the context of single atoms?

This isn't my field. What am I missing?

Re:Wrong!

[painandgreed]

I don't think so. If it has energy, then that energy can be transferred, and heat is the transfer of energy. Absolute zero is an energy-less state....

I think that's sort of the point, you can't have a energy-less atom. Otherwise the electrons would merge with the protons and you end up with neutrons. You could take a lone neutron and declare it at absolute zero compared to the rest of the universe, but that would be trivial. I'm sure trying to cool a hypothetical neutronium substance would also have difficulties. You can say that heat just deals with systems but the system will be the sumation of the energy of the system will be at least that of one atom. Still, that there are electrons around the nucleus of an atom indicates energy in the system and some minimum amount of energy and wobble and therefore heat. I seem to remember calculating such for a hydrogen atom early in undergrad quantum mechanics class. I seem to remember it being 5/3K or some nice fraction like that, but that was 30 years ago and I may just be imagining things.

Re:Wrong!

[Altrag]

Energy states are quantized, yes. And there is a lowest state for any particular particle which, as far as anybody knows, you cannot drop below while still remaining that particle. For example if an electron gets dropped into energy state "0", its effectively joined the nucleus and one of your protons becomes a neutron -- its a gross oversimplification but basically that's what happens to form neutron stars.

Free energy on the other hand is not quantized (or at least our best models don't show it to be such.)

As for temperature having meaning in the context of single atoms uhh.. sort of but not really? What we measure as "temperature" is the average energy of the system. So in the context of a single atom you'd kind of be "averaging" across one thing. And digging in much deeper than that ends up at questions like "what is energy?" which nobody can answer. You get lots of descriptions of what energy does or what we can use it for but nobody knows or even has a theory about what it is, on a fundamental level. At least not a scientific one (I'm sure there's lots of philosophical and religious answers..) Its just there.

Exactly the sort of burdensome regulations

[rsilvergun]

our new president was elected to repeal. We're going to make America Cool again!

Re:Exactly the sort of burdensome regulations

[npslider]

Does this mean I can get a HUGE government discount on an Air Conditioner?

If we all buy one, we can export all our extra heat overseas... fix the trade inbalance, and create more Jobs here... I'm thinking A/C repairman...

It's gonna be great!

Re:Exactly the sort of burdensome regulations

[roman_mir]

If being absolutely cool is outlawed then only the Outlaws will be absolutely cool.

Re:Exactly the sort of burdensome regulations

[grcumb]

our new president was elected to repeal. We're going to make America Cool again!

We're tired of being cool.

signed,
The Dakotas.

"Lisa, get in here!"

[Anonymous Coward]

"In this house we obey the laws of thermodynamics!"

Re: "Lisa, get in here!"

[ChrisMaple]

Your mindset condemns you and nobody else.

Would?

[xession]

Would this also be a property of time? That you can't reach absolute zero because doing so, would be akin to stopping time, if only for that specific single point in space?

Now that has me wondering about the singularity in a black hole. And now my brain hearts a little as so many things seem to conflict with all of this.

Re:Would?

[bill_mcgonigle]

Would this also be a property of time? That you can't reach absolute zero because doing so, would be akin to stopping time, if only for that specific single point in space?

Now that has me wondering about the singularity in a black hole. And now my brain hearts a little as so many things seem to conflict with all of this.

Read Hawking's "A Brief History of Time" - it's from the 80's but he deals with this and related concepts elegantly. Time never gets to zero - as soon as you try you're back to where you started. cf. Alice's Adventures.

I think the proof in this case is a bit different, though. If a system had zero energy, you couldn't even interact with it (i.e. observe it). And there's the quantum noise of everything in the universe; it probably isn't possible to stop the soup without removing space from the universe, and fields will always be interacting with matter no matter how hard a scientist wishes otherwise.

Unless we develop technology to create voids in the universe or to exclude fields we're going to have vibrating matter.

Re:Would?

[Anonymous Coward]

This is a great line of Thinking. I suggest "Leonard Susskind's Modern Physics course concentrating on Classical Mechanics".. In a different talk (Leonard Susskind on The World As Hologram) he describes the bet he "won" with Steven Hawking about information being persevered in black holes.
I'm going to wing it here so bear with me
We know the first 3 laws of physics as newtons laws of motion. There is another more fundamental law called the "Zero" law that describes entropy. The entropy of a a particle contains its "information" and that brings us to the "negative one" law. The information of a participle can not be destroyed even by a black hole.

Re:Would?

[Whorhay]

I was pondering a similar thought myself. If the universe continues its expansion outpacing the speed of light, shouldn't it eventually be possible for a particle of two atoms to to be the only existent particle within its visible universe. Whatever heat it had at the beginning I would expect it to lose to radiative cooling over time. Since there wouldn't be any other particles in the observable universe there shouldn't be anything to heat our particle by radiating back at it.

Re:Would?

[rcamans]

If you cooled it to absolute 0 you would know the velocity is rpecisely 0. That is a violation of Heisenberg's uncertainty principle.

Re:Would?

[Sumus Semper Una]

Unless we develop technology to create voids in the universe or to exclude fields we're going to have vibrating matter.

My observations have led me to conclude that vibrating matter has a tendency to fill voids in quite interesting ways.

Never been to Canada

[fred6666]

in the winter, pretty sure it's colder than that.

Re:Never been to Canada

[David_Hart]

in the winter, pretty sure it's colder than that.

It's the wind chill factor... (grin)

Re:Never been to Canada

[npslider]

North Pole, Alaska.

Where the weather forecaster accurately predicts when Hell will freeze over.

Re:Never been to Canada

[npslider]

So... if it's not quite absolute zero, but it's high humidity... does it "feel" colder than absolute zero? ;D

Re:No, THE COLDEST

[Anonymous Coward]

Cooling American to absolute zero will be the coldest, it will be so cold, because a lot of people are saying that global warming is a hoax. The Chinese have absolute zero, and they're very unfair to us.

We're going to make America Cool again!

Computing?

[johannesg]

"In the car industry, people ask this question all the time: how fast does the vehicle accelerate?" says Oppenheim. "Just as a computing machine performs a computation, a car can take you to the mall."

No, still doesn't make any sense...

Physicists are such bastards

[Overzeetop]

Blah blah blah...you can't go faster than light.

Blah blah blah...you can't cool to absolute zero.

I'll bet a politician would tell me I could do either one of those if it would my vote. Why can't physicists respect my desires like the nice men in suits do?

Re:Physicists are such bastards

[Shimbo]

If a politician went faster than light would she break her election promises before she got elected?

Reminds me of this engineering joke:

[Anonymous Coward]

Reminds me of this engineering joke:

A mathematician, a physicist, and an engineer were asked to review this mathematical problem. In a high school gym, all the girls in the class were lined up against one wall, and all the boys against the opposite wall. Then, every ten seconds, they walked toward each other until they were half the previous distance apart. The mathematician, physicist, and engineer were asked, “When will the girls and boys meet?”

The mathematician said, “Never.”

The physicist said, “In an infinite amount of time.”

The engineer said, “Well... in about two minutes, they'll be close enough for all practical purposes.”

Re:Reminds me of this engineering joke:

[fisted]

Shouldn't it be the mathematician who answers “In an infinite amount of time.”, and the physicist who answers "never"?
The mathematician may not care, but the physicist "knows" about the eventual entropy death of the universe, which, happening in finite time, will ensure it's actually never going to happen.

Re:Reminds me of this engineering joke:

[tommeke100]

Is it a Theoretical or Experimental Physicist?

not as definitive as it may sound

[ooloorie]

Before quantum mechanics was discovered, people could prove mathematically that no object could jump or tunnel out of a potential well; it was physically impossible. Now we know that this is quite possible since the "laws" of classical mechanics can be violated under certain conditions.

It's no different with quantum mechanics. Well, that's not quite true: it is actually a little different. Before quantum mechanics was discovered, many physicists believed classical mechanics to be complete. But for quantum mechanics, we already know that it is an incomplete theory.

Re:not as definitive as it may sound

[Altrag]

Sort of. Under QM, we may already know the theory is incomplete but at the same time, the parts we know well are far more constrained than anything classical physicists could have dreamed of prior to the introduction to QM.

For example, it would be extremely unlikely for any new or competing theory to work around the uncertainty principle and have any hope of being correct. Classical physicists thought they knew it all because they were only thinking about the things they could see. In modern QM, we have not just physical evidence but strong mathematical reasons to know where our limits are and which ones are likely to be broken and which ones aren't.

That's why you usually hear about quantizing gravity rather than smoothing QM -- for all that general relativity seems to work, its still a much weaker theory than QM. GR relies on things like the equivalence principle that are so strongly self-evident that they're generally accepted as fact but actually have no physical basis beyond noticing that gravity happens to act like a standard acceleration if you view it in the correct light. That's a whole level of "hmm" above the fine-tuning issues in QM.

Re:not as definitive as it may sound

[ooloorie]

For example, it would be extremely unlikely for any new or competing theory to work around the uncertainty principle and have any hope of being correct.

It's trivial to construct theories that "work around the uncertainty principle" and are compatible with all existing observations.

. GR relies on things like the equivalence principle that are so strongly self-evident that they're generally accepted as fact but actually have no physical basis beyond noticing that...

And the same is true for all the fundamental assumptions of QM.

Re:not as definitive as it may sound

[david_thornley]

It's trivial to construct theories that "work around the uncertainty principle" and are compatible with all existing observations.

In which case you'd have no problem sketching one out.

Re:not as definitive as it may sound

[ooloorie]

In which case you'd have no problem sketching one out.

Indeed, I don't.

Re:not as definitive as it may sound

[david_thornley]

Would you care to share?

So...

[JustNiz]

even if it wasn't impossible to cool something to absolute zero, wouldn't it be an essentially useless thing to do because once you do anything with it, it would generate some amount of heat so immediately raise its temperature slightly anyway?
(I'm imagining the passing of current on a supercooled wire or computing on a supercooled cpu)

Re:So...

[professorguy]

Technically, processing does not necessarily require power dissipation, only deleting does. So if you make sure you have 2-output gates (so the processing can be reversed--otherwise information is deleted), you can make your processing take as little power as you'd like. But, just as with the underlying problem with achieving absolute zero, the processing can never actually dissipate absolutely zero power.

Re:So...

[Altrag]

There's a big difference between impossible in practice (which lots of things are) and impossible even in theory. The latter is a much much stricter rule and can be used as a basis for other related theories to build upon since we can say for sure that its not just us failing to be clever enough.

Two things

[Anonymous Coward]

One: I think you mean "ruled out" rather than "outlawed." That implies some sort of change in the legality rather than a revealing of a "legality" (which is a somewhat obtuse way of looking at this since science is a system of attempting to describe reality rather than an attempt to describe some sort of human invention or behavior) that already existed.

Two: This has an interesting implication for our universe, I think. It's possible that the entropy eventually reaches 0 in the universe as a whole (since this apparently applies to localized entropy), but if that's actually impossible, it means there will always be *some* sort of entropy in the universe regardless of its size. I would think this to mean that a universe "death" of expansion is preferable to a universe death of collapse, at least from the perspective of life. With no entropy, there isn't really existence.

Re:Two things

[Anonymous Coward]

"Outlawed" is a reasonable word. Nobody breaks the laws of physics and lives to tell about it.

Remember: guns don't kill people; physics kills people.

Properties of matter and energy

[Toe, The]

I don't think you need to bring time into it. Just think about the absolutes of matter.

On the one hand, there is absolute zero.
On the other hand, there is the speed of light.

These are measured as different properties (temperature vs velocity), but they are the two opposite infinite states of matter.

Absolute zero would mean the complete absence of energy. Light speed means matter has transformed into energy.

So by definition, when we're talking about matter, we're talking about the stuff that exists between these two absolutes.

(Do I have this right? I've always wondered if this is common knowledge in physics, or if I am not thinking of it properly.)

Re:Properties of matter and energy

[Altrag]

Sort of, but you've described it in a bit of a misleading way. Anything that moves at c is indeed massless, and we can usually take "matter" to mean any particles that have rest mass >0.

The tricky part is that word "transformed." You can't transform matter into energy just by increasing its speed. You have to annihilate it somehow and some of the products of that annihilation will be in the form of light-speed photons (and for a very very brief time if you do it right, gluon jets, which I believe also move at c until they get constrained by color confinement as gluons are massless.) Similarly, adding more and more energy to a system doesn't necessarily force it to "slow down" and coalesce into matter.

Also, there's another difference between these two "absolutes." Stuff can move at c -- namely, light can do so. Whereas nothing can be at 0K as far as we know.

Does this mean

[fredrated]

that anyone cooling anything to absolute zero will be put into Markov chains?

entropy != disorder

[140Mandak262Jamuna]

Entropy is simply the amount of heat transferred divided by the temperature. Amount of entropy lost by the source is less than the entropy gained by the sink. Since it is a non conservative property it intrigued scientists who were very familiar with the conservation of mass, momentum and energy. So someone suggested it could be perceived as the disorder in the system since it seems logical it would/could increase without bounds.

The T-s diagram is quite precise and is used by a few gas turbine designers and millions of students to pass AE303 Gas dynamics II

infinite number of steps isn't a deal breaker.

[140Mandak262Jamuna]

So what if it takes infinite number of steps? There are plenty of infinite serieses with a finite sum. Of course he might have proved the series is not convergent. But I'm stuck with a 2g connection that sucks, giving me a good excuse for but reading the fantastic article.

Re:infinite number of steps isn't a deal breaker.

[Altrag]

There are. But simply counting 1,2,3,... is not one such series.

Asymptotic?

[sbjornda]

Aren't they just saying the behaviour is asymptotic? Or am I missing something?

--
.nosig

Universal Heat Death?

[Khyber]

"a temperature of absolute zero cannot be physically achieved because it's impossible for the entropy (or disorder) of a system to hit zero"

Would that then not imply that our universe is incapable of experiencing heat death?

Re:Universal Heat Death?

[halivar]

"Heath death" is somewhat of a misnomer. Entropy does not go away; it's when the entropy of the universe can no longer increase, due to the universe being at perfect equilibrium under the Third Law. There will still be temperature, and mater; individual particles flying around and never touching (no protons, though; they have long since decayed). We consider this to be an extreme low-energy state, not a complete lack of energy.

Disclaimer: I'm not a scientist. I just get bored and read stuff.

Re:Universal Heat Death?

[ChrisMaple]

Heat death is when there is no temperature differential and no way to make a temperature differential, not that there is a zero temperature.

Re:Universal Heat Death?

[thegarbz]

Would that then not imply that our universe is incapable of experiencing heat death?

Heat death is when there is no practical work to be extracted. This means that temperatures are the same and heat transfer can't take place. To get there we do heat transfer. Note the word transfer. Heat transfers from warm to cold bring both of them closer together.

The universe is already at 5K we can achieve temperatures colder than that in a lab. Any energy i.e. stars only add heat to this background. We may not every achieve absolute zero but we will eventually reach the heat death of the universe, and by that time the universe will be quite a few kelvin warmer than that.

Outlawed

[JustAnotherOldGuy]

"Outlawed"

I do not think that word means what you think that word means.

Proven impossible, proven unattainable, sure...but it wasn't "outlawed".

I mean, if it was then why not just repeal that law and cool stuff to absolute zero?

For the humour impaired....

[whoever57]

The parent comment was meant as a JOKE!.

Unintended Consequence

[Alotau]

If you outlaw absolute zero, only outlaws will have absolute zero.

Not again

[SuperKendall]

Cooling To Absolute Zero Mathematically Outlawed

Is there no end to what Trump will mandate with an executive order???

I'm sure that even now protests are forming around every liquid nitrogen tank in the country.

Re:Not again

[Wargames]

I would argue that "where/when" there is no space, the temperature is absolute zero.

Re:Not again

[david_thornley]

"Where there is no space" doesn't sound meaningful to me.

Isn't there a simple proof?

[u19925]

I am not a physicist, so I may be wrong, but I always thought that absolute zero is theoretically impossible. The temperature is a measure of random energy per degree of freedom. By Heisenberg principle delta_x * delta_p = h/2pi. So you have to get delta_p = 0 for absolute zero or delta_x = infinity.

The best you can get in lab by cooling atoms is to create a Bose Einstein condensate in which all the atoms acts as a single coherent wave. This can reduce random KE significantly. For particle of size of hydrogen atom and container of size of 1 ft, this value is of order 10^-9 K.

not quite true

[eyenot]

a physical system, perhaps, cannot reach complete entropy. but a purely mathematical system can.

They're all wrong

[AndyKron]

They're all wrong. I was cooled to absolute zero at work today!

I know

[Daetrin]

*sigh* Plancks length. Measuring things to the precision of a planks length was obviously mastered quite some time ago. That's what i get for trying to make a quick post just before running out of the office for the day =P

Solution

[Chewbacon]

Just calculate 0Â kelvin to a temperature we can actually achieve. Nevermind the physics that comes with it. Bah, details!