Why does time only move forward and not backwards?

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  • #26
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1. It is not my job to come up with a counter-example to my own argument.
2. All you have succeeded in convincing me is that further discussion is a waste of time.
1. Nor you have proven or can prove your argument either! ...
2. It would also help if you were not kind of cantankerous, sometimes.

Have you read the whole thread? There was a dispute, not exactly what you're asking though, and was resolved back then (about whether, at least in everyday macroscopic life, we can tell apart the two possible directions of time):
As long as time moves in the same direction for everything, it does not matter whether that direction is labelled "forward" or "backward". Ripples from a rock dropped in a pond will appear to move outward either way.
(Proven wrong:)
The smaller the circles the lower the entropy ... thus more into the "future", thus inwards. q.e.d
No, only if you choose the false direction, as you suggested.
"Time reversal" is a tricky thing! ...
[In Particle Physics it may be a symmetry, but not in everyday life ...]
 
  • #27
jbriggs444
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As long as time moves in the same direction for everything, it does not matter whether that direction is labelled "forward" or "backward". Ripples from a rock dropped in a pond will appear to move outward either way.
(Proven wrong:)
Nope. The statement is correct. Though it seems that you had not actually agreed with it.

No matter which direction time "flows", a person inside the universe where it does so will experience a progression from low entropy past to high entropy future.

If someone outside the universe chooses to invoke time reversal symmetry and claim that the flow of time is actually reversed, that is of no consequence to the inhabitants of the universe in question.
 
  • #28
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Nope. The statement is correct. Though it seems that you had not actually agreed with it.
You have to review carefully the thread too. We had agreed on it:
The smaller the circles the lower the entropy ... thus more into the "future", thus inwards. q.e.d
(Thus it violates the entropy law in that case [of reversed time]. Thus we can use that argument to pin-point the increasing entropy direction as the correct direction of time ...)

You had agreed on it:
Edit: I see now the scare quotes around "future" and agree with what you wrote.
 
  • #29
jbriggs444
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You have to review carefully the thread too. We had agreed on it:

(Thus it violates the entropy law in that case [of reversed time]. Thus we can use that argument to pin-point the increasing entropy direction as the correct direction of time ...)

You had agreed on it:
Right. We had an agreement. But then you claimed disagreement. Please do not do that.
 
  • #30
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Right. We had an agreement. But then you claimed disagreement. Please do not do that.
You did that not me
 
  • #31
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  • #32
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I am not the one who wrote "proven wrong".
Yes, for your original statement, which later on I assume you realized its falsity: in reversed time, circles go inward (to a decreasing and not increasing entropy), while you said always outwards ... . Simple.
 
  • #33
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Yes, for your original statement, which later on I assume you realized its falsity: in reversed time, circles go inward (to a decreasing and not increasing entropy), while you said always outwards ... . Simple.
The original statement was and is correct.

Edit to add... Your objection appears to have been that there is only one correct labeling for past and future. My suggestion is that if we are to give meaning to the notion of "time flowing into the future", one approach is to note that the labeling is arbitrary.

However, as we both agree, operationally the result is the same. The observable progression for inhabitants of a time-reversed universe is indistinguishable from that for a time-normal universe. Time still "flows" from the direction of low entropy to high entropy.

We both agree that one might as well label the direction of low entropy as "past". It would appear that our disagreement is purely about words and not about physics. However, I dislike to see "proven false" applied to a disagreement about words.
 
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  • #34
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It's not just about words.
Time still "flows" from the direction of low entropy to high entropy.
Is incorrect, if you switch "past" and "future". Just make yourself a simple diagram and think carefully.
 

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