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Mohamed Daw
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Is there any maximum temperature that could be reached ( since temp is directly prop. To average kinetic energy , knowing that no particle can exceed the speed of light .
Mohamed Daw said:Is there any maximum temperature that could be reached ( since temp is directly prop. To average kinetic energy , knowing that no particle can exceed the speed of light .
Mohamed Daw said:Is there any maximum temperature that could be reached ( since temp is directly prop. To average kinetic energy , knowing that no particle can exceed the speed of light .
Darwin123 said:The Planck temperature is the maximum temperature where current physical theories remain self consistent. For systems above that theoretical temperature, general relativity and quantum mechanics contradict each other.
What about the Third Law of Thermodynamics?QuasiParticle said:The Planck temperature (or any higher temperature) is no problem for systems with finite number of energy states. In these systems, any temperature can be attained according to the known laws of physics, including negative temperatures.
I don't see any problem with the third law in the case of finite number of energy states and negative temperatures. Entropy of the system is minimum at ±0 K and maximum at [itex]\pm \infty[/itex].Darwin123 said:What about the Third Law of Thermodynamics?
I'm not quite sure what you mean by thermal equilibrium. Surely the system will tend to lose energy and cool if the environment is colder. Remember, negative temperatures are "hotter" than any positive temperatures. But other than this, these systems are in thermal equilibrium.Darwin123 said:What you said is probably true for systems that are not in thermal equilibrium.
I don't quite see this.Darwin123 said:One way to formalize this is to define temperature as the derivative of internal energy with respect to entropy. Or rather,
T=dU/dS
where U is the internal energy, S is the entropy and T is the temperature. For a system that is in a stable equilbrium,, either T=0 or T>0. If T<0, then the system is not in stable equilibrium.
If T<0, then the dU/dS<0. The system can then be in an unstable energy state.
QuasiParticle said:I'm not quite sure what you mean by thermal equilibrium. Surely the system will tend to lose energy and cool if the environment is colder. Remember, negative temperatures are "hotter" than any positive temperatures. But other than this, these systems are in thermal equilibrium.
The example I have in mind is a nuclear spin system in a magnetic field.
I don't know about those laser systems, but nuclear spin systems of metals at low temperatures are very well decoupled from the environment. The spin system itself relaxes fast enough to reach thermal equilibrium for that degree of freedom. Negative temperatures have been detected experimentally in these systems.alemsalem said:Can these systems really be considered stable, since they can always emit photons or leak into kinetic degrees of freedom or something?
I understand that if they really are isolated degrees of freedom then you can consider them in thermal equilibrium at a negative temperature.
QuasiParticle said:I don't see any problem with the third law in the case of finite number of energy states and negative temperatures. Entropy of the system is minimum at ±0 K and maximum at [itex]\pm \infty[/itex].
I'm not quite sure what you mean by thermal equilibrium. Surely the system will tend to lose energy and cool if the environment is colder. Remember, negative temperatures are "hotter" than any positive temperatures. But other than this, these systems are in thermal equilibrium.
The example I have in mind is a nuclear spin system in a magnetic field.
I don't quite see this.
Your derivative is not well defined for these systems, since two values of U correspond to a given entropy. But even if you write 1/T=dS/dU, I don't see what the problem is.
Darwin123 said:You said,
“In these systems, any temperature can be attained according to the known laws of physics, including negative temperatures.”
The maximum temperature that can be reached is known as the absolute hot, which is approximately 1.416785(71) x 10^32 Kelvin. This temperature is theorized to be the limit of the universe and cannot be reached by any known means.
Yes, there is a limit to how hot things can get. As mentioned before, the absolute hot is theorized to be the limit of the universe. However, on a smaller scale, materials can only withstand a certain amount of heat before they start to break down or melt, so there is a practical limit to how hot things can get.
No, we cannot create temperatures hotter than the absolute hot. This temperature is a theoretical limit and cannot be reached through any known means.
Temperature affects matter by causing its particles to vibrate more and move faster, leading to changes in its physical state or chemical reactions. As the temperature increases, matter can change from a solid to a liquid to a gas, and eventually, the particles can break apart into plasma at extremely high temperatures.
Yes, there is a minimum temperature limit known as absolute zero, which is 0 Kelvin or -273.15 degrees Celsius. At this temperature, all molecular motion stops, and matter reaches its lowest possible energy state. It is considered the coldest temperature possible and cannot be reached in reality, as some residual energy will always remain in matter.