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Discussion Overview

The discussion revolves around the concept of time travel, particularly in relation to Einstein's theories and the implications of relativistic physics. Participants explore theoretical frameworks, paradoxes, and the nature of spacetime, including time-like, light-like, and space-like separations of events. The conversation includes references to wormholes, the twin paradox, and the effects of traveling at or above the speed of light.

Discussion Character

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

Main Points Raised

  • Some participants note that Einstein rejected the idea of time machines but suggested that time travel could be possible if wormholes exist.
  • One participant claims that moving fast enough causes time to slow down for the traveler, allowing them to experience less time than others.
  • Another mentions solutions to Einstein's field equations that suggest time loops, but these require conditions not observed in nature, such as negative energy.
  • There is a discussion about the implications of faster-than-light travel, including potential paradoxes and the concept of causality.
  • Participants debate the definitions and implications of time-like, light-like, and space-like separations, with some seeking clarification on these concepts.
  • One participant questions the feasibility of mapping the universe's timeline onto a number line and discusses the relativity of simultaneity.
  • Clarifications are made regarding the nature of spacetime and the differences between Newtonian and relativistic views of time.

Areas of Agreement / Disagreement

Participants express a range of views on the nature of time travel and the implications of relativistic physics. There is no consensus on the feasibility of time travel or the interpretations of causality and spacetime separation.

Contextual Notes

Participants reference various theoretical constructs and paradoxes without reaching definitive conclusions. The discussion highlights the complexity of spacetime concepts and the limitations of current understanding in physics.

Who May Find This Useful

Individuals interested in theoretical physics, the nature of time, and the implications of Einstein's theories may find this discussion relevant.

  • #31
Ibix said:
Did your phone have to be there in 1970 for its clock to measure time since then?

But the hardware/software that calculates the time had to be there before that time.

Ibix said:
Regarding post 25 - as I said, no, this has nothing to do with finite or infinite. Look up Einstein's train.
Except my "finiteness" argument. Is it correct?
I am editing it. Maybe it should be on a separate thread.
 
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  • #32
e-pie said:
But the hardware/software that calculates the time had to be there before that time.
You are trying to say that because VAX/VMS happens to use November 17, 1858 (it is a 64 bit integer measured in 100 nanosecond ticks) as its base date that there must have been a VAX back then? Not so.

Edit: Before we dive further into the relevance of epoch times in operating system timekeeping, it is past time for you to Google Einstein's train though experiment and get a handle on the relativity of simultaneity.
 
  • #33
Okay got the point. @jbriggs444 and @Ibix. Thanks to both.

And the new post 25?
 
  • #34
e-pie said:
And the new post 25?
i.e.
e-pie said:
The way I look at time(meaning how I define/measure it) depends on my choice of how I try to define each. As each choice is unique, we won't get any particular choice to be the standard/base.
The time coordinate in a coordinate system depends on the choice of coordinate system, yes.
The laws of physics fail to pick out a preferred coordinate system, yes.
 
  • #35
jbriggs444 said:
it is past time for you to Google Einstein's train though experiment and get a handle on the relativity of simultaneity

Almost midnight here. I will do it later. Let is stop the discussion here. I will start another thread/continue after I read Einstein's train experiment and clear my head a bit.I mean I tried but I am feeling sleepy and Wikipedia is not helping.Thanks.A Request: I think that, if this discussion is restricted between us three, it will not create any confusion(to me/any future viewers). Multiple opinions on same topic do tend to get messy and different commentaries can be hard to read(for me).And I am getting positive feedback from both.
Thanks. Logging of for now.
 
  • #36
e-pie said:
Off topic

Why is each post duplicating?Happening to me also.
It was likely due to a forum speed issue that should be cleared up now. If you see any other double-posts, just click the Report link to bring it to the attention of the Mentors so we can fix it up. Thanks! :smile:
 
  • #37
Sorry to keep both waiting. I studied Einstein's Train Thought Experiment from Wikipedia.

In short what I understood:

Two lightnings struck on a train moving uniformly ie inertial. To the standing observer outside of train frame the events have two space coordinates but same time coordinates but as the train is moving uniformly, to the observer in train the events have two time coordinates.

That is, simultaneity depends on reference frame?

Please comment if anything is wrong
 
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  • #38
Questions coming to my mind are off-topic(this post).

I will try to start new threads regarding those questions.

For the time being, please comment to post 37.Correct me/add something extra.

After your comments, I will end this discussion here and start new threads about relevant questions.Thanks to both. And the mentors, for their technical help.
 
  • #39
e-pie said:
That is, simultaneity depends on reference frame?
Yes.

New threads should probably go in the relativity forum - it's not general discussion. This thread probably should be moved there, actually.
 
  • #40
Ibix said:
This thread probably should be moved there, actually.

Right I started this thread to get some definitive sources vide post 1. But the discussion culminated into a "scientific" one.
Thanks to both.

Any mentor want to do it?

Ibix said:
This thread probably should be moved there, actually.

Thanks for your reply. I will start new threads as promised and in time.

Am reporting my own post to get this into moderator's notice.
 
Last edited:

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