Entropy: Increasing or Decreasing?

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Discussion Overview

The discussion revolves around the concept of entropy, particularly whether it is increasing or decreasing in the universe. Participants explore the implications of entropy in relation to the formation of structures and life after the Big Bang, as well as the definitions and interpretations of entropy in various contexts, including thermodynamics and information theory.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants assert that the formation of matter, stars, galaxies, and life on Earth represents an increase in order, questioning the conventional view that entropy is always increasing.
  • Others challenge this perspective by asking whether the processes involved are irreversible, suggesting that the increase in order may not contradict the second law of thermodynamics.
  • One participant emphasizes that entropy is a measure of the number of internal states a system can have, arguing that not all increases in entropy correspond to "increasing disorder."
  • Another participant supports this view by explaining that entropy is characterized by multiplicity, which relates to the number of microstates associated with a macrostate, and that the entropy of Earth does not necessarily need to increase.
  • A participant introduces an engineering perspective on entropy generation, indicating that it can be used to quantify irreversibilities in processes, with specific conditions for irreversible and reversible processes.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of entropy and its implications for order and disorder in the universe. There is no consensus on whether the processes described lead to an increase or decrease in entropy, and the discussion remains unresolved.

Contextual Notes

The discussion highlights limitations in the understanding of entropy, including the dependence on definitions and the context of processes being considered. The relationship between energy input and output in Earth's steady state is also noted as a factor that complicates the discussion of entropy changes.

Naveen3456
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Everybody says entropy of the universe is increasing.

But after the big bang, matter formed, it came together, stars and galaxies were formed, on a small planet called Earth atoms/molecules came together to form unicellular organisms and then higher life. Our brains are organizing even more and more as our intelligence level is increasing.

Isn't this order?
 
Science news on Phys.org
:/
Get yourself together man.
Are all these irreversible processes?
 
Naveen3456 said:
Everybody says entropy of the universe is increasing.

But after the big bang, matter formed, it came together, stars and galaxies were formed, on a small planet called Earth atoms/molecules came together to form unicellular organisms and then higher life. Our brains are organizing even more and more as our intelligence level is increasing.

Isn't this order?

You're letting yourself be misled by the pop-sci description of entropy as "disorder".

Entropy is a measure of the number of internal states that a system can have. Not all increases in entropy correspond to our intuitive notion of "increasing disorder".
 
What Nugatory said. One can associate some kind of "disorder" to entropy, but this view is very weak in describing the state of the system. Entropy is characterized by the multiplicity, i.e. the number of microstates associated with a macrostate.

As for life forming on earth, the entropy of Earth does not need to increase. A simple argument is as follows:
most of the radiation Earth receives from the sun is in the green and the Earth emits in the infrared. Since the Earth is in steady state, energy in = energy out. Thus for every photon Earth receives, it emits two photons (the energy of an infrared photon is about half of the energy of a green photon). Two photons have a higher multiplicity than a single photon. Thus the change in entropy does not need to be greater than zero.
 
From the engineering point of view (see the book Thermodynamics; An engineering approach by Cengel and Boles) "entropy generation can be used as a quantitative measure of irreversibilities associated with a process".
Sgen > 0 --> irreversible process
Sgen = 0 --> reversible process
Sgen < 0 --> impossible process
 

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