Cooling Methods to Reach Absolute Zero
I understand that absolute zero temperature cannot be reached
because it cannot be measured. However in regard to experimenting with
something like this, how would it be possible to cool something to such low
temperatures in an attempt to get as close as possible to -273 K (or
absolute zero temperature?
There are several laws in Thermodynamics that relate absolute
temperature (K) to other physical properties that can be measured or
controlled. These laws are a good approximation to the behavior of
many gases. Some laws apply to ideal gases and other versions apply
to non-ideal gases. For the most part, the relationship between
Pressure, Volume and Temperature are all the same for the properties
of gases, and that is: The pressure of a gas of a known mass, at a
fixed volume, is directly proportional to the gas's absolute
The ideal gas law, for example: PV = nR T, where P is the absolute
Pressure, V is the volume, T is the absolute temperature, and n is the
known quantity or mass, and R is the universal gas constant.
What is important here is to see the relationship between, Pressure and
Temperature. If we are to conduct an experiment in absolute
temperatures near absolute zero, we may do so in a closed environment,
with a gas at a fixed volume. By lowering the absolute pressure to
near zero Pascals, we may achieve an environment with absolute
temperatures near absolute zero.
Hope that helps.
Laser cooling is a class of methods used to reach temperatures very
close to absolute zero. Here's a good intro to how laser cooling
Also, I might modify your opening statement slightly -- In the case of
absolute zero, thermodynamic theory states that absolute zero cannot
be reached through thermodynamic methods -- that's different than
saying absolute zero cannot be reached because we cannot measure it.
(also, I think you mean -273C... 0K is absolute zero, not -273K)
Hope this helps,
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Update: June 2012