Why does time only move forward and not backwards?

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SUMMARY

The discussion centers on the nature of time and its unidirectional flow, primarily linked to the concept of entropy. Participants reference the "Arrow of Time" and the Second Law of Thermodynamics, asserting that time progresses from low to high entropy. Key texts mentioned include J.C.N. Smith's "Time — Illusion and Reality" and the Wikipedia article on entropy. The conversation highlights the philosophical implications of time perception versus its scientific understanding, emphasizing that while time appears to flow forward, its fundamental nature may be more complex.

PREREQUISITES
  • Understanding of the Second Law of Thermodynamics
  • Familiarity with the concept of entropy in physics
  • Knowledge of the philosophical implications of time
  • Basic grasp of quantum mechanics and time-reversal symmetry
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  • Read J.C.N. Smith's "Time — Illusion and Reality"
  • Study the Second Law of Thermodynamics and its implications on entropy
  • Explore the concept of time-reversal symmetry in quantum mechanics
  • Investigate the philosophical perspectives on time and its perception
USEFUL FOR

Physicists, philosophers, students of thermodynamics, and anyone interested in the fundamental nature of time and entropy.

  • #31
Stavros Kiri said:
You did that not me
I am not the one who wrote "proven wrong".
 
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  • #32
jbriggs444 said:
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
Stavros Kiri said:
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.
 
Last edited:
  • #34
It's not just about words.
jbriggs444 said:
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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