Is it possible to obtain a temperature reading below absolute zero?

Question

Thanks! =D

I mean the temperature itself, not the reading. =D

Answer 1

Absolute zero is the theoretical temperature at which all molecular and atomic motion stops. And since you can't be more stopped than totally stopped, there are no temperatures colder than this.

Answer 2

Theoretically, absolute zero is the point at which there is no molecular motion or emitting/absorbing of energy.

Theoretically, this temperature can not be attained.

Therefore, it should not be possible to obtain a temperature below zero degrees Kelvin.

Answer 3

If the question is, "Can a system have a negative temperature on the absolute scale?", the answer is "Yes."

If the question is, "Can you stick a properly-functioning thermometer into a bunch of matter and get a negative reading on the absolute scale?", the answer is "No." (By "properly-functioning" I mean a thermometer whose reading corresponds to the actual absolute temperature of the system.)

If the question is, "Can a system be colder than absolute zero?", the answer is "No." (Here I am considering the definition of "cold" to be in terms of the direction of heat flow; i.e., heat flows from a hotter object to a colder object.)

In formal thermodynamics, temperature is defined as the reciprocal of the rate of change of the entropy of a system with respect to the total internal energy of the system: T = 1/[dS/dU], where T is the temperature, S is the entropy, and U is the internal energy (the derivative is a partial derivative where other thermodynamic variables are held constant).

In certain systems, T as defined above can be negative. Consider a collection of quantum-mechanical spins -- which act roughly like little bar magnets -- in a magnetic field. Since magnets tend to align with a magnetic field, if all of the spins are aligned in the direction of the magnetic field, the energy of the spin system is small (the spin system is in its "ground state") and the entropy is also small, because the system is highly ordered (there is only one possible microstate of the system in which all the spins are aligned parallel to the field). At the other extreme, if all the spins are aligned anti-parallel to the magnetic field, the energy is large (since the spins want to align parallel to the field), but the entropy is again small because a system with all its spins aligned is highly ordered. In the intermediate case, in which half the spins are aligned with the field and half are aligned against, the energy has an intermediate value but the entropy is high (since there are many different possible microscopic configurations of the spins that lead to half of them pointing one way and half of them pointing the other way).

For this spin system, if you draw the curve for S (the entropy) as a function of U (the internal energy), you'll find that it looks like an inverted bowl: S is small when U is small (near the case where all the spins point along the field), S gets larger as U gets larger (nearing the case when all the spins are randomly oriented), and then S gets small again as U gets even larger (nearing the case where all the spins point against the field). In the perfect intermediate case (randomly aligned spins) there is an inflection point in the S as a function of U curve as the curve turns over. Here the slope dS/dU is zero, so T is infinite. On either side of that point, the slope of the curve is either positive or negative -- corresponding to either positive or negative "spin temperature." So, you can say that when the spins are all nearly aligned with the magnetic field, T is a small positive number, which approaches +Infinity as the spins randomize; once the spins are randomly aligned, if they start to align again antiparallel to the magnetic field, T goes from -Infinity to a small negative number. Note that T --> -Infinity and T --> +Infinity approach the same macroscopic state. So, in this system it's not the case that as you cool the system toward its ground state you go from positive temperatures through zero to negative temperatures. In this interpretation, negative temperatures are actually hotter than large, nearly infinite positive temperatures. So, the "hottest" state of the system is when the spins are aligned anti-parallel to the field, then you cool the system and get a completely disordered system with half of the spins aligned each way, then you cool it further and get all the spins aligned with the field.

Note that these results are a peculiarity of the formal thermodynamic definition of temperature. Obtaining a negative absolute temperature does not mean that the system is "colder" than absolute zero. No system can be colder than absolute zero. Also, these negative spin temperatures were not measured with a thermometer; they were inferred indirectly from the behavior of the system's entropy as a function of energy. Negative spin temperature was discussed by Ramsey in a 1956 article in the Physical Review (vol. 103, pp. 20-28). He discussed a 1950 magnetic resonance experiment conducted by Purcell and Pound on a system of nuclear spins in a strong magnetic field. There is also a good article on negative spin temperature in the Physical Review (vol. 108, pp. 1441-1458, 1958) by Abragam and Proctor, which emphasizes the quantum-mechanical treatment of the spin system. The phenomenon of negative spin temperature is also discussed in certain textbooks on thermodynamics (such as the one by Kittel and Kroemer), as well as some monographs on the fundamentals of magnetic resonance (such as Slichter's book).

Answer 4

No, in the kelvin system, at absolute zero the particles of matter stop moving and things can't get any colder.

The farenheit and celsius units have no absolute zero, but the temperature readings can get well below zero degrees using their systems.

Answer 5

It is possible to obtain a temperature READING below absolute zero, because an instrument can malfunction and read negative one million degrees.

However, it is not possible to obtain an actual temperature below, or even at, absolute zero. It impossible from a thermodynamical standpoint to cool something to absolute zero, and impossible for a temperature below absolute zero to exist at all.

Answer 6

Actually absolute zero is the the lowest feasible temperature.....for REAL GASES(eg...OXYGEN ,HYDROGEN,etc..)...But yes u can surely attain temperatures below this temperature in Case of solids and liquids ...that is a negative temperature reading...many solids liquify at temperatures much below -273 degee Celsius..

Answer 7

yeah its called negative