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Physics, Astronomy & Cosmology / Re: How is absolute zero degrees determined?
« on: 04/04/2014 10:36:21 »
One of the first hints was obtained by graphing the relationship of temperature and volume of a gas, see Charles Law.
If you extrapolate this straight line to very low temperatures, you estimate that the volume of the gas will drop to zero at around -273C.
Now, most real gases turn into liquids long before they reach this temperature, and display other non-ideal behaviours (after all, their atoms have a finite volume, and can't disappear into nothing by just cooling them). But gases like Helium can come very close, allowing a good estimate of absolute zero.
If you extrapolate this straight line to very low temperatures, you estimate that the volume of the gas will drop to zero at around -273C.
Now, most real gases turn into liquids long before they reach this temperature, and display other non-ideal behaviours (after all, their atoms have a finite volume, and can't disappear into nothing by just cooling them). But gases like Helium can come very close, allowing a good estimate of absolute zero.