# How is heat death a disorder?

As entropy increases, the universe will evolve toward a thermodynamic equilibrium, and I understand that in a macroscopic sense, that is order since the temperature is the same everywhere. However, in a microscopic sense, it is chaotic, because as you increase temperature the movement of the atoms get faster and faster, now what I am unable to understand is, why is the heat death scenario considered a disorder? If it means the universe will be getting really cold, doesn't the mean that in the microscopic level the atoms will be moving very slowly? Isn't that more of an order than a disorder?

• The comparison of entropy to disorder is generally a bad one. Everyone seems to do it though. – jjack Feb 23 '18 at 20:33
• Heat death means that temperature will become uniform, not that the universe will become colder. – valerio Feb 23 '18 at 20:48
• @valerio I have read in many resources that it meant the cooling of the universe, hence the confusion. – Dewton Feb 23 '18 at 21:05
• @Dewton, there is little scientific evidence that entropy of the entire universe is increasing or that a thermodynamic equilibrium is being reached. It is a 19th century axiomatic concept that finds no robust support in modern theory - nor in the first law of thermodynamics! – Steve Feb 23 '18 at 22:11
• @valerio I think that's just a semantic quibble. It's true that the "death" imagery comes from the full equilibration at a uniform temperature, but the currently accepted $\Lambda$-CDM cosmological model also implies that that temperature will get arbitrarily close to zero as the expansion of the universe dilutes the matter content ever lower. I think it's reasonable to incorporate that cooling into the "heat death" concept. – tparker Feb 23 '18 at 22:19