What is Arrow of time: Definition and 54 Discussions

The arrow of time, also called time's arrow, is the concept positing the "one-way direction" or "asymmetry" of time. It was developed in 1927 by the British astrophysicist Arthur Eddington, and is an unsolved general physics question. This direction, according to Eddington, could be determined by studying the organization of atoms, molecules, and bodies, and might be drawn upon a four-dimensional relativistic map of the world ("a solid block of paper").Physical processes at the microscopic level are believed to be either entirely or mostly time-symmetric: if the direction of time were to reverse, the theoretical statements that describe them would remain true. Yet at the macroscopic level it often appears that this is not the case: there is an obvious direction (or flow) of time.

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  1. P

    The Arrow of Time: Entropy & System Evolution

    it is the change in entropy that ultimately provides us with the answer to why systems will naturally evolve in one direction with time and not the other: systems always evolve in time in such a way that the total entropy of system + environment increases. If you observe a system in which the...
  2. M

    Arrow of time, or arrow of memory?

    "Arrow" of time, or "arrow" of memory? I need help understanding this. To me, it seems, well not to be over the top about it, but, well, pretty much ridiculous that there wouldn't be *the appearance* of an "arrow" of time that points in one and only one direction. Take the classic question of...
  3. J

    Question about quantum statistical mechanics and thermodynamic arrow of time

    I got into a discussion about the "arrow of time" recently, and one point I brought up is that for a system governed by time-symmetric laws, if you place no special restrictions on the initial conditions but instead pick an initial state randomly from the system's entire phase space, you will be...
  4. wolram

    Arrow of time and why it flows in only one direction

    http://www.physorg.com/news1734.html An interesting article on the arrow of time and why it flows in only one direction.
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