What do you think about time travelling.

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Discussion Overview

The discussion revolves around the concept of time travel, exploring its feasibility, theoretical underpinnings, and various interpretations. Participants examine both the scientific theories related to time travel, such as the twin paradox and time dilation, as well as the implications of these theories on our understanding of time. The conversation includes speculative ideas and personal reflections on the nature of time travel.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question the possibility of time travel, suggesting it is impossible or not worth considering.
  • Others argue that the twin paradox provides a valid framework for understanding time travel, asserting that it demonstrates time travel is possible in principle.
  • There are discussions about the mechanics of achieving time travel, particularly through time dilation at relativistic speeds.
  • Concerns are raised about the engineering challenges and physical forces involved in accelerating objects to near-light speeds.
  • Some participants propose that time travel could be viewed as an engineering problem rather than a purely physical one.
  • There is a debate about the definition of "state" in the context of traveling backward in time, with questions about how time travel interacts with the concept of a complete description of conditions at a given time.
  • References to tachyons and their theoretical implications for time travel are mentioned, though their validity remains uncertain.
  • Personal reflections on the subjective experience of time passing quickly or slowly are shared, indicating a philosophical angle to the discussion.

Areas of Agreement / Disagreement

Participants express a range of views on the possibility of time travel, with some asserting it is feasible while others maintain it is impossible. The discussion remains unresolved, with multiple competing perspectives on the nature and mechanics of time travel.

Contextual Notes

Limitations include unresolved questions about the practical implementation of time travel, the definitions of key terms like "state," and the implications of physical laws on the feasibility of time travel scenarios.

parshyaa
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is it possible to travel in time, what are some concepts, theories which are yet to be explore to know more about time travelling.
 
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Why is this in General Discussion forum? And have you done a search on this very topic for the numerous threads already posted in this forum?

Zz.
 
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Since it is impossible, I don't think of it at all.
 
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Kevin McHugh said:
Since it is impossible, I don't think of it at all.

It is possible! The twin paradox is a perfectly valid way to travel time. Just because we understand it, doesn't mean that it's not time travel. And traveling backwards in time is not contradicting any physics either.
 
micromass said:
It is possible! The twin paradox is a perfectly valid way to travel time. Just because we understand it, doesn't mean that it's not time travel. And traveling backwards in time is not contradicting any physics either.

In the twin paradox, the twin leaves in the present and returns to the present. Only the passage of time was different for the twins.

I forget where I read it, but it was explicitly stated that time travel is impossible, perhaps due to entropy. In Feynman diagrams, antiparticles travel backward in time, but I expect this mere convention.
 
Kevin McHugh said:
In the twin paradox, the twin leaves in the present and returns to the present. Only the passage of time was different for the twins.

It is possible in principle to leave, to travel for 1 second, come back and be 5000 years in the future. That's time travel no?
 
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micromass said:
It is possible in principle to leave, to travel for 1 second, come back and be 5000 years in the future. That's time travel no?

I'm curious, how can this be done?
 
Kevin McHugh said:
I'm curious, how can this be done?

Time dilation. Just travel for one second for a speed sufficiently close to light. On earth, 5000 years will pass, while for you it looks like 1 second.
 
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  • #10
micromass said:
Time dilation. Just travel for one second for a speed sufficiently close to light. On earth, 5000 years will pass, while for you it looks like 1 second.

How would you accelerate an object to a fraction of the speed of light, slow it down, turn it around and accelerate it back to earth, and slow it down once again, all in one second?
 
  • #11
Kevin McHugh said:
How would you accelerate an object to a fraction of the speed of light, slow it down, turn it around and accelerate it back to earth, and slow it down once again, all in one second?

That's an engineering problem. Physics says it's possible.
 
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  • #12
micromass said:
That's an engineering problem. Physics says it's possible.

What about the forces on the body? That's a physics problem.
 
  • #13
I consider it an engineering problem. Of course we can't time travel right now. But saying that the physics laws forbid it, that's false. It's very likely we'll never be able to do it though.
 
  • #14
And sure, you're probably right that the forces on the human body forbid this kind of thing. But where do you draw the line: traveling 5000 years in 1 second is not possible. But traveling 2 seconds in 1 second might be more feasible. Travelling 1.001 seconds in 1 second maybe even more. Where do you draw the line as to what is time travel and what is not? I consider them all to be time travel.
 
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  • #15
Kevin McHugh said:
How would you accelerate an object to a fraction of the speed of light, slow it down, turn it around and accelerate it back to earth, and slow it down once again, all in one second?
"Solar" (i. e. stellar) sails. Although it'd take considerably longer than a second. The current engineering problem isn't achieving a significant fraction of light speed, it is escaping or resisting micro collisions with cosmic dust or anything larger.
 
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  • #16
We are all time traveling with respect to another (e. g. the aliens) all the time.
 
  • #18
micromass said:
It is possible! The twin paradox is a perfectly valid way to travel time. Just because we understand it, doesn't mean that it's not time travel. And traveling backwards in time is not contradicting any physics either.

As a question of terminology, what is the definition of "state" when we refer to "travelling backward in time" ? - which presumably means traveling to some previous "state" of a system in time.

The various popular depictions of traveling backward in time have the time traveller arrive at some state in the past where he is a novelty, or can see his younger self or a deceased relative etc. But if a "state" is a complete description of conditions at a given time, it should include the information that the time traveller is present. So if the traveller travels backward to some state in time where "state" refers to a complete description of things, it is a state where he was present at that time. Of course, we can imagine that in the state of the world at the present moment there are time travellers from the future among us, but this seems outside the scope of the twin paradox.

So, paying attention to the definition of "state", isn't there a distinction between the twin paradox and a scenario where a person would travel backward in time ? Or is the notion of "twin" supposed to invite some limiting argument where person T only differs from his twin by epsilon and we can let epsilon go to zero and argue that T can meet up with himself ?
 
  • #20
parshyaa said:
what do you think about time traveling.
I enjoy it, but I wish I could do it a little slower.
 
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  • #21
russ_watters said:
I enjoy it, but I wish I could do it a little slower.
uh huh, I am convinced that the years seem to go by faster than they used to :-p
 
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  • #22
davenn said:
uh huh, I am convinced that the years seem to go by faster than they used to :-p
No they are not, you are going slower than you used to.
 
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  • #23
rootone said:
No they are not, you are going slower than you used to.

naaa, life is just passing quicker, everything is at a more hectic rate than 30 - 40 yrs ago. :frown:
 

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