# Randomness in time reversal case

## Main Question or Discussion Point

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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Staff Emeritus
2019 Award
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.

Drakkith
Staff Emeritus
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?

Nugatory
Mentor
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?

Nugatory
Mentor
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 ) 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.

Nugatory
Mentor
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.