[ExI] Time Travel and FTL flight

[SR Ballard]

I think it’s totally possible to travel faster than light without traveling faster than time. 

Sure you could see light from the past, but we do that all the time. 

SR Ballard

> On Sep 2, 2021, at 5:44 PM, Adrian Tymes via extropy-chat <extropy-chat at lists.extropy.org> wrote:
> 
> 
>> On Thu, Sep 2, 2021 at 2:26 PM Ben Zaiboc via extropy-chat <extropy-chat at lists.extropy.org> wrote:
> 
>>> On Thu, 2 Sept 2021 at 18:02, Adrian Tymes via extropy-chat
>>> <extropy-chat at lists.extropy.org> wrote:
>>> >
>>> <snip>
>>> > But clearly it is not time travel
>> So Adrian, are you saying that FTL flight wouldn't involve time-travel?
>> 
> I am saying that it doesn't necessarily involve time travel.  There may be certain versions that might involve it, but there exists at least one version that does not. 
>> I thought that under certain circumstances it would (specifically FTL travel to a location that was accelerating away at a significant rate relative to the point of departure, then FTL return. I think). Or is there no problem, and it's just the simple fact that nothing with mass can travel at, or faster than, light-speed that stops us being able to do it? (and tricks like Acubierre Drive, if it could exist, would work without causing paradoxes)?
>> 
> The latter.  Normal acceleration beyond light speed might cause it, but is impossible, so it doesn't matter what the math says if it were - and even if it were possible, it would not be the only way.  As you note, there exist tricks to get around the limit, and said tricks also (so far as we currently know) cut off the potential for time travel.
> 
> Thus: not all forms of FTL that are possible, cause time travel.  It may be that no forms of FTL that are possible, cause time travel, but I have not yet done that analysis.
> 
> The matter at hand was the objection that FTL always causes time travel, which I believe is not a true claim.
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