The whole Universe was in some sense caused by a fluctuation against entropy, and it is this fluctuation that may give the “direction of time” to our Universe. That doesn’t mean they’re not important though. So, fluctuations against entropy are possible, but improbable and we can do nothing to increase their likelihood. But they excrete heat and waste products to such an extent that they increase the entropy around them. This is what makes life possibly: biological cells create highly ordered states in which low entropy activities can happen. But in so doing, they increase the entropy around them. Some machines like fridges and biological cells work by decreasing entropy in a local environment. But Maxwell’s Demon can only do this by gaining information about the system: and in so doing, Maxwell’s Demon increases information entropy.
You might have read about Maxwell’s Demon, a thought experiment in which a Demon is able to decrease entropy by sorting fast and slow molecules ( ). For example, we could try to pump all the molecules into one compartment, but that would involve doing mechanical work, and mechanical work increases entropy by creating heat. It’s not possible for humans to do anything in particular to increase entropy though. If there are a lot of air molecules, the probability would become increasingly small. A lot of devices, not least the airlocks on spaceships, and a lot of chemistry experiments, rely on this not happening. This would be a lower entropy state than the air even distributed.
For example, if we have a container with two compartments, it is possible that all the air molecules will fly into one compartment. Its perfectly possible (but statistically unlikely) for systems to tend towards lower entropy. High entropy states are more probable than low entropy states, so any change to a system will in general lead to higher entropy. The second law of thermodynamics is often phrased to say that the entropy always increases, but what is really says is this: Entropy is just a statistical effect (but a statistical effect of enormous significance for literally every process in the Universe).
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