What would happen if we encountered a place where time ran backwards?

[jvanname]

The universe is entirely reversible, so it is possible for time to run backwards. The idea that time would ever go backwards is not too far-fetched. For example, in the reversible cellular automata critters, for fairly simple configurations, there comes a time when the cellular automata reverses itself and time in a sense goes from the forward direction to the backwards direction. https://dmishin.github.io/js-revca/index.html

[1715614031]

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[SaltySpitoon]

A way to prove the direction of time, is by stating that time increases in the direction of increasing entropy. Every second that passes, global entropy increases. Weird things happen when you play with the limits of time or try to go beyond them. You start getting difficult to imagine descriptions of whats going on, such as size and mass of objects changing. If you take time as a negative value, you end up with nonreal answers. Mathematically at least.

[Foxpup]

A way to prove the direction of time, is by stating that time increases in the direction of increasing entropy.

Another, more intuitive reason to define time this way is that the direction of increasing entropy is the order in which you experience events. As your brain works to experience events and create memories of them, it consumes energy and produces heat, thus increasing entropy. If time were running backwards and entropy was reversed, your brain processes would be reversed as well, thus you would remember reversed future events (really the past) as though they had already happened, but the reversed past (really the future) would be unknown to you, so from your perspective, time isn't running backwards at all. (Okay, I lied when I said this was more intuitive.)

[paxmao]

The universe is entirely reversible, so it is possible for time to run backwards.

No, it is exactly the opposite, it always evolves in the direction of higher entropy as other user's have said before. Refer yourself to Hawking's "A Brief History of Time", Chapter 9, "The Time Arrow" for further clarification on three possible time arrow indications.

[jvanname]

A way to prove the direction of time, is by stating that time increases in the direction of increasing entropy. Every second that passes, global entropy increases. Weird things happen when you play with the limits of time or try to go beyond them. You start getting difficult to imagine descriptions of whats going on, such as size and mass of objects changing. If you take time as a negative value, you end up with nonreal answers. Mathematically at least.

I am well aware of entropy and the second law of thermodynamics. I however claim that the second law of thermodynamics does not completely rule out the possibility that time is running in reverse. There may be a mechanism that reverses the flow of time in the universe. The cellular automata Critters is a reversible cellular automaton so Critters exhibits the second law of thermodynamics. However, Critters also has a time reversal mechanism. In other words, time may be going backwards locally even though it is going forwards globally.

[SaltySpitoon]

I am well aware of entropy and the second law of thermodynamics. I however claim that the second law of thermodynamics does not completely rule out the possibility that time is running in reverse. There may be a mechanism that reverses the flow of time in the universe. The cellular automata Critters is a reversible cellular automaton so Critters exhibits the second law of thermodynamics. However, Critters also has a time reversal mechanism. In other words, time may be going backwards locally even though it is going forwards globally.

Its an interesting thought, but there are still the other issues that'd take place. For time to move from forward 1 second/s to -1 second/s, there would be a point where time is stopped. As an object approaches the speed of light, time in its reference frame comes to a stop, and its mass approaches infinity. If you could continue to supply energy a proportionally larger amount than infinity, perhaps you could reach a state of negative time? I haven't done the derivation in quite a while, so I don't recall what the physical implications of negative time would be.

I'd be interested in whether black holes have some sort of observable temporal distortion, they are the only infinite mass application that I can think of. Maybe thats a stepping stone in figuring out negative time?

[odolvlobo]

What exactly do you mean by "run backwards"? Are you asking a question like what would happen right and left were switched? Or are you asking specifically about reversing the 2nd law of thermodynamics and the T violation in B meson decay?

Actually, if you encountered a place where the laws of physics were different, then we would have to change the laws of physics since they are assumed to be universal.

I think one thing it would not allow us to do is to predict the future of the past.

[MULTIK888]

The universe is entirely reversible, so it is possible for time to run backwards. The idea that time would ever go backwards is not too far-fetched.

In fact, what you're saying is a very real theory. After your topic, I immediately remembered a very interesting and unusual film. "The curious case of Benjamin Button". I think the creators of this film also thought about the fact that time can be reversed, and that sometimes what happens is beyond description.
If you have not seen this film I advise you to watch it!!!

[Spendulus]

The universe is entirely reversible, so it is possible for time to run backwards. ...

So chicken become eggs!

But they still cross to the other side!