5 ms·

I was keen to explore (even if it's a bit dated) but unfortunately the combination of mobile-browser and dark mode makes a bit of a mess of things.. (making it

I was keen to explore (even if it's a bit dated) but unfortunately the combination of mobile-browser and dark mode makes a bit of a mess of things.. (making it quite a bumpy ride) I wonder if there are any 'translations' to other formats around? "Second Law of Thermodynamics: In any cyclic process the entropy will either increase or remain the same." I need some clarity about what is meant by 'cyclic' here. Is it perhaps to refer to feedback loops/self-sustaining phenomena?

filmor 5y ago
A cyclic process is a thermodynamic process that eventually arrives back in its initial state: https://en.wikipedia.org/wiki/Thermodynamic_cycle https://en.wikipedia.org/wiki/Thermodynamic_cycle
- danwills 5y ago
  Thanks, had a read and I think I understand approximately. I am still wondering whether biological systems should count as cyclic in this sense too? I think that they seem to, in the returning-to-the-same-state thing, at least across the generations, and even in regular metabolism in some sense - but the law doesn't (intuitively) seem to apply in the biology/evolution case.. it doesn't just diffuse, it can go on in pretty much precisely the same pattern for billions of years it seems? I guess I am probably ignoring something huge about this (like the Sun!?)
  - deleted 5y ago
    [deleted]
streamofdigits 5y ago
no, cyclic in this context means that all macroscopic system variables (temperature etc) return to their initial conditions
- eurasiantiger 5y ago
  Funny, I wasn’t aware we were aware of the initial conditions of the non-onservable universe.
  - google234123 5y ago
    Why wouldn’t they be different than the initial conditions of the observable universe?
    - eurasiantiger 5y ago
      I wasn’t aware we are aware of those, either. In any case, the non-observable universe is certainly a superset of the observable universe.
      - google234123 5y ago
        We have some ideas... anyway, what do the initial conditions of our universe have to do with this one definition of the 2nd law?
  - bocklund 5y ago
    It's not "initial conditions" as in time=0. Thermodynamic state variables are path independent, so "initial conditions" in this context means the conditions of the reference point in the process from the point you start measuring.
PennRobotics 5y ago
Good physical examples are refrigerators or gas engines.
- danwills 5y ago
  I see, thanks. I'm wondering if there might be any good examples of cyclic systems in the natural world too? Both of those devices are complicated, and you'd need to know the operation in detail to be able to connect it with the phases of a state-cycle-diagram.. but maybe something natural might make it easier to understand?

filmor 5y ago

A cyclic process is a thermodynamic process that eventually arrives back in its initial state: https://en.wikipedia.org/wiki/Thermodynamic_cycle https://en.wikipedia.org/wiki/Thermodynamic_cycle

danwills 5y ago
Thanks, had a read and I think I understand approximately. I am still wondering whether biological systems should count as cyclic in this sense too? I think that they seem to, in the returning-to-the-same-state thing, at least across the generations, and even in regular metabolism in some sense - but the law doesn't (intuitively) seem to apply in the biology/evolution case.. it doesn't just diffuse, it can go on in pretty much precisely the same pattern for billions of years it seems? I guess I am probably ignoring something huge about this (like the Sun!?)
- deleted 5y ago
  [deleted]

streamofdigits 5y ago

no, cyclic in this context means that all macroscopic system variables (temperature etc) return to their initial conditions

eurasiantiger 5y ago
Funny, I wasn’t aware we were aware of the initial conditions of the non-onservable universe.
- google234123 5y ago
  Why wouldn’t they be different than the initial conditions of the observable universe?
  - eurasiantiger 5y ago
    I wasn’t aware we are aware of those, either. In any case, the non-observable universe is certainly a superset of the observable universe.
    - google234123 5y ago
      We have some ideas... anyway, what do the initial conditions of our universe have to do with this one definition of the 2nd law?
- bocklund 5y ago
  It's not "initial conditions" as in time=0. Thermodynamic state variables are path independent, so "initial conditions" in this context means the conditions of the reference point in the process from the point you start measuring.

PennRobotics 5y ago

Good physical examples are refrigerators or gas engines.

danwills 5y ago
I see, thanks. I'm wondering if there might be any good examples of cyclic systems in the natural world too? Both of those devices are complicated, and you'd need to know the operation in detail to be able to connect it with the phases of a state-cycle-diagram.. but maybe something natural might make it easier to understand?