Entropy is the only quantity in the physical sciences that "picks" a particular direction for time, sometimes called an arrow of time. As one goes "forward" in time, the second law of thermodynamics says that, the entropy of an isolated system will increase when no extra energy is consumed. Hence, from one perspective, entropy measurement is thought of as a kind of clock though measuring entropy does not accurately measure time.

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  • Entropy is the only quantity in the physical sciences that "picks" a particular direction for time, sometimes called an arrow of time. As one goes "forward" in time, the second law of thermodynamics says that, the entropy of an isolated system will increase when no extra energy is consumed. Hence, from one perspective, entropy measurement is thought of as a kind of clock though measuring entropy does not accurately measure time. There is also the complication that, locally, entropy can decrease with time: living systems decrease their entropy by expenditure of energy at the expense of environmental entropy increase. By contrast, all physical processes occurring at the microscopic level, such as mechanics, do not pick out an arrow of time. Going forward in time, an atom might move to the left, whereas going backward in time, the same atom might move to the right; the behavior of the atom is not qualitatively different in either case. In contrast, it would be an astronomically improbable event if a macroscopic amount of gas that originally filled a container evenly, spontaneously shrunk to occupy only half the container. Certain subatomic interactions involving the weak nuclear force violate the conservation of parity, but only very rarely. According to the CPT theorem, this means they should also be time irreversible, and so establish an arrow of time. This however is not linked to the thermodynamic arrow of time, which is the main issue of this article, nor has it anything to do with our daily experience of time irreversibility .
  • Termodynamiczna strzałka czasu (inaczej entropowa strzałka czasu) – popularnonaukowe określenie na fakt, że zgodnie z drugą zasadą termodynamiki wzrost entropii w układach izolowanych może stanowić podstawę określenia kierunku strzałki czasu w skali całego Wszechświata przy założeniu, że Wszechświat jest układem izolowanym.
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  • Arrow of time: Why did the universe have such low entropy in the past, resulting in the distinction between past and future and the second law of thermodynamics?
  • physics
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  • Entropy is the only quantity in the physical sciences that "picks" a particular direction for time, sometimes called an arrow of time. As one goes "forward" in time, the second law of thermodynamics says that, the entropy of an isolated system will increase when no extra energy is consumed. Hence, from one perspective, entropy measurement is thought of as a kind of clock though measuring entropy does not accurately measure time.
  • Termodynamiczna strzałka czasu (inaczej entropowa strzałka czasu) – popularnonaukowe określenie na fakt, że zgodnie z drugą zasadą termodynamiki wzrost entropii w układach izolowanych może stanowić podstawę określenia kierunku strzałki czasu w skali całego Wszechświata przy założeniu, że Wszechświat jest układem izolowanym.
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  • Entropy (arrow of time)
  • Termodynamiczna strzałka czasu
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