No meaning to go backwards in time

  • Context: High School 
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Discussion Overview

The discussion revolves around the concept of time travel and the implications of moving backwards in time. Participants explore the nature of time as a dimension, the semantics of movement in time versus space, and the theoretical frameworks that allow for or deny the possibility of time travel, particularly in the context of general relativity and quantum mechanics.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • Some participants argue that if time is treated as a dimension similar to space, then moving backwards in time lacks meaning, as all motion is inherently forward.
  • Others challenge this view by stating that arriving at a starting point in space does not equate to moving backwards, suggesting that the semantics of "forward" and "backward" are being conflated.
  • One participant proposes that going backwards in time could be interpreted as moving into the past while still traveling forwards in time, referencing closed timelike curves (CTCs) from general relativity.
  • Another participant expresses skepticism about the possibility of time travel, suggesting that even in scenarios involving closed loops, interpretations could lean towards non-locality rather than actual time travel.
  • There is mention of various theoretical approaches to time travel, including the need for consistency constraints and the potential role of quantum physics in preventing time travel.
  • Some participants reference the Chronology Protection Conjecture, which posits that mechanisms may exist to prevent time travel and maintain causality.
  • Mathematical frameworks are suggested as necessary tools for clarifying discussions about time and its directionality.

Areas of Agreement / Disagreement

Participants generally disagree on the semantics and implications of moving backwards in time, with multiple competing views on the feasibility and interpretation of time travel. The discussion remains unresolved regarding the actual possibility of time travel and the interpretations of related concepts.

Contextual Notes

Limitations include varying interpretations of time and motion, dependence on definitions of terms like "forward" and "backward," and unresolved mathematical implications of time travel theories.

  • #31
nealh149 said:
Flatland, you are treating this problem like the universe has 6 spatial dimensions. This isn't the case there are only three. You can move positive and negative in each of these directions. YOu're acting like moving negative along the horizontal is like moving positive in a totally separate dimension.
I don't understand what you mean. I am not treating the universe as having six dimension. A dimension by definition is a plane that is completely perpendicular to all the other planes. Ok, not exactly the greatest definition but you get the point.
 
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  • #32
If you move a clock's hand forward half a turn, do you not go back in time by moving the clock hand back half a turn.

ie. you have returned the system to it's original position.

I guess this is more a case of what frame you measure time from.

In a lot of dynamical systems you can usually reverse time by setting t=-t. This means that you can go backwards in examine how the system was in the past - even though you only know the present.

In some systems, eg. those which depend on the past - modeled by delay differential equations - you can only do this time reversal when the system is locked to some predictive path, eg. a periodic oscillation.

To this effect, I would say that, in real life, if the future is somehow determined by what happened in the past - in a nontrivial way, you won't be able to go back in time.

Or am I ranting into a Friday philosophical discussion here...
 
  • #33
Well, I for one believe there are many reasons why you can't go back in time. This is just one of them.
 

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