# The Last Question: GPT-4 Edition

## This one goes out to the Asimov fans

Me: How can entropy be reversed?

ChatGPT (on GPT-4): In thermodynamics, entropy is a measure of the randomness or disorder in a system. The Second Law of Thermodynamics states that in a closed system, entropy tends to increase over time, meaning that the system becomes more disordered. This principle is often referred to as the โarrow of time,โ as it provides a direction for the progression of natural processes.

Reversing entropy, or reducing the disorder of a system, is theoretically possible but practically challenging. Here are a few ways in which entropy can be reduced or seemingly reversed:

Decrease the systemโs temperature: When a systemโs temperature is lowered, the particles within it have less kinetic energy, which reduces the randomness of their motion. This can lead to a decrease in entropy, as observed in the process of freezing water into ice.

External work: Entropy can be reduced in a subsystem if work is done on it by an external source. For example, a refrigerator reduces the entropy of its interior by removing heat and transferring it to the external environment. However, the entropy of the entire system (refrigerator + surroundings) still increases.

Maxwellโs Demon: This is a thought experiment proposed by James Clerk Maxwell to illustrate the possibility of reversing entropy. The โdemonโ is a hypothetical being that can separate fast-moving particles from slow-moving ones in a gas, creating a temperature difference and seemingly reducing entropy. However, modern interpretations of this thought experiment show that the demon would need to perform computations and expend energy, which would increase the overall entropy of the system.

Quantum effects: There are some theoretical proposals suggesting that quantum effects could allow for a decrease in entropy, but these ideas remain highly speculative and are not yet supported by experimental evidence.

Itโs important to note that while entropy can be reduced locally in certain systems or subsystems, the overall entropy of the universe will continue to increase according to the Second Law of Thermodynamics. Reversing entropy on a universal scale is currently beyond our understanding and the scope of known physical laws.

So essentially, โthere is as yet insufficient data for a meaningful answerโ. No surprise there.

## Confused?

Isaac Asimov wrote a particularly compelling short story called The Last Question back in 1956. The question I ask above is the recurring central theme, asked of technological entities in various eras throughout a cosmic timescale. A prophetic and deeply philosophical piece, Asimov considered The Last Question his best short story. Itโs publically available here, and thereโs an audible narration from Asimov himself here.

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