Randomness in time reversal case

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Discussion Overview

The discussion revolves around the concept of time reversal in relation to a dice drop experiment, specifically questioning whether reversing time would result in the dice returning to its original position and displaying the initial number. The scope includes theoretical implications, interpretations of time reversal, and considerations of thermodynamics.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions whether reversing time would lead the dice to return to its original position, suggesting that it is a reverse process where nothing new would occur.
  • Another participant emphasizes the ambiguity in the term "reverse time," indicating that different interpretations could lead to different answers.
  • Concerns are raised about the violation of the second law of thermodynamics in the context of time reversal, referencing a specific article that discusses fluctuations at the nanoscale.
  • A later reply critiques the article's summary, arguing that it misrepresents the scientific findings regarding time reversal and thermodynamics, suggesting that no actual reversal of time is occurring.
  • There is a reminder about the importance of providing sources in discussions, particularly when referencing scientific claims.

Areas of Agreement / Disagreement

Participants express differing views on the meaning of "reversing time" and its implications for the dice experiment. There is no consensus on how to interpret the question or the implications of thermodynamics in this context.

Contextual Notes

The discussion highlights the complexity of interpreting time reversal, with multiple plausible interpretations and the potential for misunderstanding scientific concepts related to thermodynamics and fluctuations.

elementHTTP
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I have dice whit starting temperature of 0 K in vacuum and its displaying number 1 ,after drop it displays number 6 (for example) .
Now if we reverse time, will dice sitting still on surface return to original position (displaying number one ) or it will display different random number ?
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Since we cannot reverse time, I don't see that this question has an answer. (We could of course film this and play the film backwards, but I don't think this is your question)
 
If time would be reversed in your example, why wouldn't the dice return to the previous position? After all this is effectively a reverse process nothing new would occur in it.
 
elementHTTP said:
I have dice whit starting temperature of 0 K in vacuum and its displaying number 1 ,after drop it displays number 6 (for example) .
Now if we reverse time, will dice sitting still on surface return to original position (displaying number one ) or it will display different random number ?

The way you stated your question makes it ambiguous. What does "reverse time" mean specifically in this case? Is it different than what we mean when we talk about time reversal symmetry?
 
TheNerdConstant said:
If time would be reversed in your example, why wouldn't the dice return to the previous position? After all this is effectively a reverse process nothing new would occur in it.

The problem with this answer is that, as Vanadium50 says above it and Drakkith says below it, no one has any idea what either you or the original poster mean when you talk about " reversing time". There are at least three plausible interpretations of what the original poster means, and the answer is different for each one of the three (which is a nice trick for what looks like a yes/no question with only two possible answers).

So let's hold off on trying to answer the question until we know what is, OK?
 
Violation of second law of thermodynamics .
I was reading this article http://medienportal.univie.ac.at/presse/aktuelle-pressemeldungen/detailansicht/artikel/never-say-never-in-the-nano-world/
 
elementHTTP said:
Violation of second law of thermodynamics .
I was reading this article http://medienportal.univie.ac.at/presse/aktuelle-pressemeldungen/detailansicht/artikel/never-say-never-in-the-nano-world/
It's seldom wise to trust summaries of new scientific work that have been written for the general public, and this article is no exception. You would think from reading it that the researchers have found interesting violations of the second law of thermodynamics that challenge our understanding of the forward-only motion of time at the nanoscale. But if you look at the abstract of the actual scientific paper (the paper itself is behind a paywall :headbang:) you will see that they've done something very interesting but not as much fun for the university PR department to write about (emphasis mine):
Fluctuation theorems are a generalization of thermodynamics on small scales and provide the tools to characterize the fluctuations of thermodynamic quantities in non-equilibrium nanoscale systems. They are particularly important for understanding irreversibility and the second law in fundamental chemical and biological processes that are actively driven, thus operating far from thermal equilibrium. Here, we apply the framework of fluctuation theorems to investigate the important case of a system relaxing from a non-equilibrium state towards equilibrium. Using a vacuum-trapped nanoparticle, we demonstrate experimentally the validity of a fluctuation theorem for the relative entropy change occurring during relaxation from a non-equilibrium steady state. The platform established here allows non-equilibrium fluctuation theorems to be studied experimentally for arbitrary steady states and can be extended to investigate quantum fluctuation theorems as well as systems that do not obey detailed balance.
So there's no "reversing time" going on, and no better answer to your question than the one that Vanadium-50 gave you above.
 
Closed, and I'm going to take advantage of this opportunity to remind everyone that PF rules require providing sources. Stuff like this is the reason why.
 

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