Do Time Paradoxes Prove the Impossibility of Time Travel?

Click For Summary

Discussion Overview

The discussion revolves around the question of whether time paradoxes can serve as proof against the possibility of time travel. Participants explore theoretical frameworks, mathematical implications, and thought experiments related to time travel, particularly focusing on both backward and forward time travel within the context of general relativity (GR).

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that proving the impossibility of time travel is inherently difficult, especially on a macroscopic level, as it involves proving a negative.
  • There are claims that certain solutions in general relativity allow for backward time travel, such as the Gödel universe and Van Stockum cylinders, although no realistic physical implementation has been found.
  • One participant mentions that orbits around infinitely long rotating cylinders can lead to closed timelike curves (CTCs) in GR, contingent on specific conditions like mass and rotation speed.
  • Another participant argues that forward time travel is evidenced by relativistic effects observed in atomic clocks, suggesting that backward time travel may also be possible, at least for small intervals, as indicated by Feynman's quantum electrodynamics (QED) theory.
  • There is a discussion about the implications of Feynman's arguments regarding positrons as electrons moving backward in time, raising questions about the nature of particles and time travel at the subatomic level.

Areas of Agreement / Disagreement

Participants express a range of views, with some arguing for the possibility of time travel under certain conditions while others maintain skepticism about proving its impossibility. The discussion remains unresolved, with multiple competing perspectives on the nature of time travel and the validity of paradoxes.

Contextual Notes

Limitations include the dependence on specific theoretical frameworks and assumptions about the nature of time and free will. The discussion does not resolve the mathematical or physical complexities involved in the claims made.

MathematicalPhysicist
Science Advisor
Gold Member
Messages
4,662
Reaction score
372
what proof will do in order to wrap it up?
do we need a mathematical proof or experimental proof (although i don't know how could do it, perhaps with a thought experiment which the results are known)?

for the question of thought experiment could the time paradoxes do it for a proof that time travel is impossible?
 
Physics news on Phys.org
i don't think its possible to disprove timetravel (yet), even on a macroscopic level.

you are trying to prove a negative which is hard to do.

i don't think it can be disproved with mathematics due to Godel's incompleteness theorem.

the various time travel paradoxes are only paradoxes if you believe things will have a 'free will' when they go back in time.
 
There's not solid proof that (bacwrads) time-travel is impossible, infact in GR there are certain situations where it does occur, though no-one has yet found a physically realistic way.
 
There's not solid proof that (bacwrads) time-travel is impossible, infact in GR there are certain situations where it does occur, though no-one has yet found a physically realistic way.

There are? What are they?
 
Well one involves a rotating universe (a Godel universe) and the other infinitely long cylinders (Van Stokum cylinders)
 
would you care to explain about the latter?
 
Orbits around infinitely long cyclinders can lead to temporally closed loops in GR.
 
The cylinders have to be rotating and massive. IIRC the circumference had to be moving at above 1/3 the speed of light. James Tipler had a piece of this solution too. If I am not mistaken there are CTCs (closed timelike curves) in the neighborhood of a Kerr (spinning) black hole also.

All of these solutions depend on a massive spinning object. The idea is that the combination of high curvature due to strong gravity and weird coordinates due to spin will cause the light cones to tip over so that the past cone of one point overlaps the future cone of a nearby one, enabling a timelike path that goes into the past and returns.
 
Proof against time travel? Forward time travel happens whenever two bodies have differing velocities relative to each other, and has been measured and recorded with atomic clocks on airplanes. The only limiting factor to how far forwards in time you can travel is how fast you can go..

Secondly, isn't backwards time travel (FOR SMALL INTERVALS OF TIME) not only possible, but an essential part of Feynmans QED theory?

So NO, their will never be proof against it, only proof for it!
 
  • #11
The proof should right first

If the question is wrong or no value, no mean to proof by some times.
specialy in a future study direction, I think it is no mean.
 
  • #12
Adrian,

feynmann did argue the possibility of time travel (for the subatomic world anyway). In a simplified sense, He argued the existence of positrons as electrons floating backwards in time with the photons given off in e+ e- interactions as the U-turn in time triggers. The one really interesting extrapelation from this idea is that there could be only one electron in the universe.
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 21 ·
Replies
21
Views
3K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 65 ·
3
Replies
65
Views
14K
  • · Replies 36 ·
2
Replies
36
Views
10K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 21 ·
Replies
21
Views
3K
  • · Replies 41 ·
2
Replies
41
Views
5K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 125 ·
5
Replies
125
Views
9K