Early Laboratory Cooling
In 1904 Dutch scientist Heike 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 four degrees above absolute zero, to less than −269 °C (4 Kelvin). Only in this exceptionally cold state will helium liquefy, the boiling point of helium being at −268.94 °C. Kamerlingh 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 higher 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.
Read more about this topic: Lowest Temperature Recorded On Earth
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