Towards the absolute zero

In summary, the Third Law of thermodynamics states that absolute zero cannot be attained by any procedure in a finite number of steps. However, it can be approached arbitrarily closely but never reached. The question of how close it can be approached is dependent on the technology available, but there is a theoretical limit due to the quantization of energy. The smallest possible unit of energy is determined by the zero point energy of the medium, which varies depending on the nature of the medium. Therefore, the limit of how close we can get to absolute zero is ultimately dependent on the physical properties of the cooling instruments used. One estimate suggests a temperature of 7.06E-33 K, while another calculation using the mass of the universe and the formation
  • #1
ryokan
252
5
The Third Law of thermodynamics states that absolute zero cannot be attained by any procedure in a finite number of steps.
Absolute zero can be approached arbitrarily closely, but it can never be reached.
My question is: How much (in power of ten) could it be closely approached?
Is there any limit over the thermodynamic?
 
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  • #2
Lets think in a process which can lead us to make a system down its temperature. We can do it by adiabatic processes connected with isothermic ones, but we have a limit given by the mechanic of the process, we cannot link two different adiabatic processes without any other process, because two adiabatics can't have common points. But when we reach lower temperatures, we have a problem.

The lowest isotherm has exactly the same points than the lowest adiabatic because zeroth entropy is at zero kelvin. So, if an isothermic can not cut another isothermic and the same occurs with adiabatics, how can we reach the zeroth one?

I don't know if my post is well explained, due to the language :)
 
  • #3
MiGUi said:
Lets think in a process which can lead us to make a system down its temperature. We can do it by adiabatic processes connected with isothermic ones, but we have a limit given by the mechanic of the process, we cannot link two different adiabatic processes without any other process, because two adiabatics can't have common points. But when we reach lower temperatures, we have a problem.

The lowest isotherm has exactly the same points than the lowest adiabatic because zeroth entropy is at zero kelvin. So, if an isothermic can not cut another isothermic and the same occurs with adiabatics, how can we reach the zeroth one?

I don't know if my post is well explained, due to the language :)

Thanks MiGUi, but my question is simply quantitative: How closely could be the approach to zero? Indefinitely towards zero? Is there a practical limit due to physical nature of instruments both of cooling and measure?
 
  • #4
As we get closer, its more difficult keep cooling the system, because we need every time more number of processes to down the temperature. 0 K is the limit, and every approach we do to this limit depends on the technology we have at the moment.

Maybe we can reach [tex]10^{-50} K[/tex], but not nowadays.
 
  • #5
MiGUi said:
As we get closer, its more difficult keep cooling the system, because we need every time more number of processes to down the temperature. 0 K is the limit, and every approach we do to this limit depends on the technology we have at the moment.

Maybe we can reach [tex]10^{-50} K[/tex], but not nowadays.

Why? Why not [tex]10^{-55} K[/tex] or [tex]10^{-63} K[/tex]? :rolleyes:
 
  • #6
Well, I said maybe... but you must realize that the step between 0.001 K and 0.0009 K is not as difficult to do, as the step between 0.0009 K and 0.0008 K because as we get closer to 0 K, we need more processes to down the temperature.
 
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  • #7
Temperature is proportional to the average kinetic energy of the molecules. Due to the "Heisenberg uncertainty principle" the speed of the molecules and thus the kinetic energy cannot be zero. So there is a theoretical limit on how low a temperature can be obtained.
 
  • #8
This website:
http://www.ph.rhbnc.ac.uk/schools/ZeroT/Absolute.html [Broken]
cites experiments that have reached 30 nano-degrees above 0.
 
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  • #9
HallsofIvy said:
This website:
http://www.ph.rhbnc.ac.uk/schools/ZeroT/Absolute.html [Broken]
cites experiments that have reached 30 nano-degrees above 0.

Thank you, HallsofIvy. It is a very interesting website.
 
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  • #10
If energy is quatized, as it seems to be, then there should be a theoretical limit. No system can posses less than a single quanta of energy. If this is true, what is the smallest possible unit of energy? That should be the least amount of energy any system can possess, and therefore the closest we could ever get to 0ok.
 
  • #11
How about a wild guess of 7.06E-33 K? Anyone care to guess how I came up with that number? A more scientific approach, I think, be based on the zero point energy of the medium. The lowest allowed vibrational energy (zero point energy) of an atom at 0 degrees Kelvin is 1/2 hv, where h is Plancks constant and v is the vibrational frequence of the material. The value of v depends on the nature of the medium. The vibrational quantum [hv] for hydrogen is, for example, is 8.75E-20 J.
 
  • #12
LURCH said:
If energy is quatized, as it seems to be, then there should be a theoretical limit. No system can posses less than a single quanta of energy. If this is true, what is the smallest possible unit of energy? That should be the least amount of energy any system can possess, and therefore the closest we could ever get to 0ok.

Energy is not quantized in 'packets' of the same energy. The quanta of the electromagnetic field, the photon, for example has en energy proportional to it's frequency ([itex]E=h \nu[/itex]). So there's no minimum amount of energy one quantum has to possess.
 
  • #13
Chronos said:
How about a wild guess of 7.06E-33 K? Anyone care to guess how I came up with that number? A more scientific approach, I think, be based on the zero point energy of the medium. The lowest allowed vibrational energy (zero point energy) of an atom at 0 degrees Kelvin is 1/2 hv, where h is Plancks constant and v is the vibrational frequence of the material. The value of v depends on the nature of the medium. The vibrational quantum [hv] for hydrogen is, for example, is 8.75E-20 J.

Thus, over the absolute zero, it would be the zero point energy. That is a fundamental limit, that you exemplify with hydrogen.
The question then would be: over this zero point energy (medium - dependent), would it be another fundamental zero point linked to physical properties of the cooling instruments ?
 
  • #14
new and improved

If all the mass in the universe collapsed, the resulting black hole would have a temperature of about 4E-31. [disclaimer:I calc'd that pretty quick]. So, plug in your own favorite value for the mass of the universe into this and see what you get.
[tex]T = \frac{\hbar c^3}{8\pi \kappa GM}[/tex]
 
  • #15
ryokan said:
The Third Law of thermodynamics states that absolute zero cannot be attained by any procedure in a finite number of steps.
Absolute zero can be approached arbitrarily closely, but it can never be reached.
My question is: How much (in power of ten) could it be closely approached?
Is there any limit over the thermodynamic?

For a gas, there will be a theoretical limit from quantum mechanics based on the minimum energy of a particle-in-a-box. This limit has been reached for the "Bose-Einstein condensates". The box size for today's BEC's is about a micron, I think (the atoms are confined by magnetic fields, not an actual box). With the atomic mass of the substance used, this gives temperatures in the 100 nanokelvin range (I'd have to look it up to be more specific, I'm probably close to the correct order of magnitude, though).

Larger boxes will lower the temperature, but they'll still be a limit based on the box size. The people making the BEC's wanted to see the BEC phenomenon, so they didn't try to make the "box" particularly big.

I'm not sure how to treat solids or liquids.
 
  • #17
Hello pervfect and Chronos.

Thank you for your interesting answers.
 
  • #18
The road towards tha absolute zero seems to be a progresssive transition from thermodynamics to quantum mechanics. Yes?
 
  • #19
Degrees Kelvin. The book

And about Lord Kelvin, has anyone read the recent David Lindley's book entitled Degrees Kelvin: A Tale of Genius, Invention and Tragedy? I only read the John S. Rigden's comment in Science 2004;305:1406.
 
  • #20
I am not certain that the zero point energy of quantum mechanics really adds a constant to the temperature scale. There must be some knowledge about that somewhere but I never saw it.
 
  • #21
How could we conceive time in a set of particles near 0ºK?
 

1. What is absolute zero and why is it important?

Absolute zero, also known as 0 Kelvin or -273.15 degrees Celsius, is the lowest possible temperature that can theoretically be reached. It is important because it is the point at which all thermal motion of particles ceases, making it a fundamental reference point for thermodynamics and other scientific fields.

2. How close have scientists come to reaching absolute zero?

Scientists have been able to reach temperatures within a few nanokelvins of absolute zero using advanced cooling techniques such as laser cooling and magnetic cooling. However, it is impossible to reach absolute zero as it would violate the third law of thermodynamics.

3. What happens to matter at absolute zero?

At absolute zero, matter would exist in a state of perfect order and all thermal motion would cease. This means that all atoms and molecules would stop moving and any liquids or gases would turn into solid forms. It is also theorized that quantum effects would dominate at this temperature.

4. What are the practical applications of studying absolute zero?

Studying absolute zero can help us understand the behavior of matter at extremely low temperatures and its effects on materials. This knowledge has practical applications in fields such as cryogenics, superconductors, and quantum computing.

5. Is it possible to create a substance that can withstand absolute zero?

Currently, there is no known substance that can withstand absolute zero temperature without experiencing changes in its physical or chemical properties. However, scientists are constantly researching and developing new materials that can withstand extreme temperatures, which could potentially lead to the creation of a substance that can withstand absolute zero in the future.

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