Coldest temperature recorded on Earth
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[edit] Cold in nature
Antarctica is the coldest place on Earth, with the lowest natural temperature ever recorded on Earth of −89 °C (−129°F) having been recorded there in 1983 at the Russian Vostok Station.
[edit] Artificial cooling
The Third Law of Thermodynamics states that a temperature of absolute zero cannot be obtained in a finite number of steps, however as cryogenic research continues temperatures of the order of picokelvins have been obtained.
[edit] Early cooling
In 1904 Dutch scientist Kamerlingh Onnes created a special lab in Leiden with the aim of producing liquid helium. In 1908 he managed to lower the temperature to less than one degree above absolute zero, to less than −272.15 °C. Only in this exceptional cold will helium liquefy, the boiling point of helium being at −268.94 °C . Onnes received a Nobel Prize for his achievement.
Onnes method relied upon depressurising the subject gases, causing them to cool. This follows from the first law of thermodynamics;
where U = internal energy, Q = heat added to the system, W = work done by the system.
Consider a gas in a box of set volume. If the pressure in the box is greater than atmospheric pressure, then upon opening the box our gas will do work on the surrounding atmosphere to expand. As this expansion is adiabatic and the gas has done work
Now as the internal energy has decreased so has the temperature.
[edit] Modern cooling
- In September 2003, MIT announced a record cold temperature of 450 pK, or 4.5 × 10-10 K in a Bose-Einstein condensate of sodium atoms. This was performed by Wolfgang Ketterle and colleagues at MIT.[1]
- As of November 2000, nuclear spin temperatures below 100 pK were reported for an experiment at the Helsinki University of Technology's Low Temperature Lab. However, this was the temperature of one particular type of motion—a quantum property called nuclear spin—not the overall average thermodynamic temperature for all possible degrees of freedom.[2]
The current apparatus for achieving low temperatures has two stages. The first utilizes a helium dilution refrigerator to get to temperatures of millikelvins, then the next stage uses adiabatic nuclear demagnetisation to reach picokelvins.
[edit] Notes
- ^ Leanhardt, A. et al. (2003) Science 301 1513. Physicsweb news report
- ^ The experimental methods and results are presented in detail in T.A. Knuuttila’s Ph.D. thesis which can be accessed from this site. Also the university’s press release on its achievement is here
