[Pseudoscience-is-malarkey (OP)]

If I traveled to Proxima Centari at a quantum or warp-like speed (however fast that is) then instantly traveled back to Earth at an even faster speed, could I find myself in the past?

[Halc]

If I traveled to Proxima Centari at a quantum or warp-like speed (however fast that is) then instantly traveled back to Earth at an even faster speed, could I find myself in the past?

This falls under the category of not-even-wrong. 'You' cannot travel faster than light, so any answer to the question is meaningless.

However, other things can do so. Let's say we lay a strip of material between the two locations, 4 light years long.  From a long distance away, we shine a laser pointer to make the red dot move from Earth to PS in say one minute and then return in 10 seconds (all measured in the frame of your choice).  The red dot would then take 1:10 minutes to get back to Earth, not traveling backwards in time at all.

[geordief]

If I traveled to Proxima Centari at a quantum or warp-like speed (however fast that is) then instantly traveled back to Earth at an even faster speed, could I find myself in the past?

This falls under the category of not-even-wrong. 'You' cannot travel faster than light, so any answer to the question is meaningless.

However, other things can do so. Let's say we lay a strip of material between the two locations, 4 light years long.  From a long distance away, we shine a laser pointer to make the red dot move from Earth to PS in say one minute and then return in 10 seconds (all measured in the frame of your choice).  The red dot would then take 1:10 minutes to get back to Earth, not traveling backwards in time at all.

So ,if we were to observe Elon Musk following the red dot  in real time and returning  to Camp Crazy he would not have travelled back in time either?

(as ludicrous  as that "concept of a plan" is)

[Pseudoscience-is-malarkey (OP)]

So ,if we were to observe Elon Musk following the red dot  in real time and returning  to Camp Crazy he would not have travelled back in time either?

(as ludicrous  as that "concept of a plan" is)

This is actually not a legitimate question, Halc is right. It's a ploy to get you to respond so I can bring up your abuse of the spacebar and provide an intervention.

[Eternal Student]

Hi.

    I think it's a fairly good answer from @Halc ,  sorry.

    It's difficult to speculate about what might happen if we don't know the mathematics that you (or "they") are assuming will hold.

    We can get one answer if we assume the mathematical formulae for special relativity would continue to apply much as it usually does - but we have just used a velocity term   v > c    in that formula.
    However, it's debateable whether the same formulae from special relativity would continue to apply when an objects velocity, v,  exceeds the speed of light, c.


    Consider this reference:       Einstein's special relativity beyond the speed of light,   Cox & Hill,  Proceedings of the Royal Society, 2012.       Available on-line here:     https://royalsocietypublishing.org/doi/full/10.1098/rspa.2012.0340
    The usual gamma factor associated with special relativity is as shown below:
  γ  =    1 / √(1  -    v²/c² )
   It can be seen that we would be taking the square root of a negative quantity  when  v > c  and hence producing an imaginary valued gamma factor.    In their  (Cox & Hill) paper, they present reasons to suggest that the appropriate gamma factor changes form to the following
    γ  =    1 / √(v²/c² - 1 )        when v > c.
  Specifically, it's a simple change of sign that occurs within the square root in the denominator.   This is sufficient to maintain a real valued gamma factor.   Their full reasoning is presented in that paper if you wish to study it   (you will notice this subtle difference appears in the transformation formulae they have labelled  2.1  and 3.18).
I will just summarise and present my opinions here:    There are some good reasons to support the validity of this new transformation   BUT  there has also been a lot of criticism from other scientists on this paper.   In particular their (Cox & Hill) reasoning doesn't hold up anything like as well when you consider a proper 3-dimensional space and 3-D velocities.    None the less, in a simplified 1-dimensional space, their reasoning is essentially flawless.   So there may be some value in it.

   Anyway, the key point I'm trying to make is that we (or certianly just I, myself) wouldn't even know what version of a Lorentz transformation we should be using when velocities exceed the speed the light.      So, exactly as stated by @Halc,  it's not as simple as just asking  "...but if we could travel faster than light then....." - we need to know which version of a Lorentz (or Lorentz style) transformation you believe will hold when velocities exceed c.
     I'm sorry if that's not the answer you were hoping for, @geordief and @Pseudoscience-is-malarkey  .    I'm sure there are going to be several different versions of an extension of special relativity for faster than light speed that probably will be peer-reviewed and published in some journal of some level of prestige and credibility.  Most of them, of course, are just going to be theories with some reasonably good reasoning but will be lacking any hard experimental evidence.    Put quite simply, there may not be anything faster than light that you could use to test the theory. 

Best Wishes.

[paul cotter]

Quite apart from attempts to prevent a complex Lorentz factor the question arises can we go back in time? I don't have a rigorous mathematical argument but it does seem to be impossible as it would create causal paradoxes.

[geordief]

Quite apart from attempts to prevent a complex Lorentz factor the question arises can we go back in time? I don't have a rigorous mathematical argument but it does seem to be impossible as it would create causal paradoxes.

Suppose you have a very small system  of objects (perhaps impossible as  no systems are closed as far as I know)

Then if that system evolves  so as to return to its exact  same configuration it eouod have "one back in time)
I don't think that is possible though  unless there exists  a truly isolated system
Even if we had a "rebounding" universe the initial /final conditions
might not be identical. (giving rise to different universes  that didn't just repeat  exactly)

@Eternal Student  of course I was not suggesting  faster than c being possible .(or "going back" in time.
That was being sarcastic which doesn't work without emoticons being used(I just assumed the answer to my question was obviously "no".

I also didn't quite follow Halc's scenario - no matter.

[Eternal Student]

Hi.

I also didn't quite follow Halc's scenario -

    It's based on the notion that a spot of light from a laser pointer can be made to move across a surface faster than light.

   See this video from Minute Physics (duration 1 minute 26 secs) for the general idea.

Best Wishes.

[geordief]

Hi.

I also didn't quite follow Halc's scenario -

    It's based on the notion that a spot of light from a laser pointer can be made to move across a surface faster than light.

   See this video from Minute Physics (duration 1 minute 26 secs) for the general idea.

Best Wishes.

Thanks.I was aware of that but I thought Halc's scenario was a little  variant on that and that was what I didn't quite  catch but I assumed it was basically what you are displaying.
My answer was my own vatiant where (impossibly) there actually was a physical body moving aling with  where an observer would see the moving dot to be.
And to point out that this  physical dot (Elon Musk) as an example because he needs the publicity  would ,even under  those far fetched(and impossible) circumstances  still not return to its starting point "before it left"

So "doubly impossible" if you get my drift.

It wasn't a logical argument so much as a farcical "argument".