Setting the Clock: the Planet way, the navy way, and the w..

I missed the Staff meeting, but the Memos showed that Offbreed
<offbreed_106.TakeThisOut@hotmail.com> wrote on Sat, 19 Apr 2008 08:27:08 -0800 in
alt.books.david-weber :
>mike weber wrote:
>> On Wed, 16 Apr 2008 19:01:41 -0800, Offbreed
>> <offbreed_106.TakeThisOut@hotmail.com> wrote:
>>
>>> Saying the equations prove FTL is time travel reminds me of the old bit
>>> about "mathematically proving" that bumble bees cannot fly.
>>
>> Actually, the math used in that case - according to John Campbell by
>> engineers at the "Skunk Works" - was both complete and totally
>> applicable to the Real World - it was just the wrong math; fixed-wing
>> when rotary wing should have been used.
>
>Uh-huh. Einstein is applicable sub light. How do we know the equations
>are applicable FTL?

The article I skimmed years ago, seemed to imply that anything
with mass cannot travel _at_ the speed of light (for certain values of
_at_), but that it was theoretically possible to travel faster than
the speed of light, the faster you go the less mass you're pushing.
(Reverse the curve as you approach the speed of light from the "slow"
side.)
It was that getting from one side to the other (and back) which is
the tricky bit.


tschus
pyotr


--
pyotr filipivich
The two oldest cliches in the book are "The Good Old Days were
better." and "After all, these are Modern TImes."
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

I missed the Staff meeting, but the Memos showed that mike weber
<fairportfan.RemoveThis@gmail.com> wrote on Sat, 19 Apr 2008 11:32:12 -0400 in
alt.books.david-weber :
>On Fri, 18 Apr 2008 04:42:27 -0800, pyotr filipivich
><phamp.RemoveThis@mindspring.com> wrote:
>
>>Actually, the saying was that, according to the then understood
>>principles of flight, there was no way to account for the flying
>>ability of bumblebees. Or to put it another way, bumblebees could fly
>>in the field, but not according to theory.
>
>So could helicopters; and the math applicable to helicopters that wa
>sknown at the time also accounted for the bees, according to JWCjr.

Ah, a tidbit I did not know. Learn something new every day.

pyotr

--
pyotr filipivich
The two oldest cliches in the book are "The Good Old Days were
better." and "After all, these are Modern TImes."
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

On Apr 13, 6:16 pm, Dahak <Dahak... RemoveThis @theXOUTfifthimperium.com.invalid>
wrote:

> But I've always wondered why so many people take it for granted
> that FTL travel is time travel.

There's a good discussion on this in a FAQ.

Basically, from Special Relativity, the simultaneity of events
separated by a distance is not something agreed upon by observers
moving at different rates. Only the speed of light is an invariant.

This means that _if_ the method by which an FTL spaceship works is
totally unchanged from one slower-than-light inertial reference frame
to another - as is true of all the known laws of physics - an FTL
spaceship can go back in time through a maneuver not all that
different from the way that a sailing ship can tack against the wind.

This also means that a hypothetical sci-fi FTL spaceship could depend
on a yet-undiscovered principle that *also* allows the invention of a
"space gyroscope", as it were, that distinguishes between different
inertial frames based on "quantum space" as a fixed reference. In that
case, FTL would not need to allow causality violations.

John Savard
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On Apr 13, 10:52 pm, Don Sample <dsam....DeleteThis@synapse.net> wrote:
> No, when you do the calculations, you end up taking the square root of a
> negative number when you try to go faster than light, so time doesn't go
> backwards, it becomes imaginary.

Wrong calculations. Elsewhere in Einstein.

John Savard
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On Sat, 19 Apr 2008 19:26:17 -0700 (PDT), an orbiting mind-control
laser made Quadibloc <jsavard.TakeThisOut@ecn.ab.ca> write:

>This means that _if_ the method by which an FTL spaceship works is
>totally unchanged from one slower-than-light inertial reference frame
>to another - as is true of all the known laws of physics - an FTL
>spaceship can go back in time through a maneuver not all that
>different from the way that a sailing ship can tack against the wind.

Like I've tried to clarify in another post, in SFnal terms, 'time
travel' has some very specific implications.

To me, "time travel" means not "arriving at a distance 'before you
appear to have left'" (i.e. outpacing your light-cone), but "arriving
/where you started/ before you left."

Arriving at some remote destination before your source light
indicates you have left is pretty useless if you still can't mail that
payment to the Gas Company before it became overdue last Wednesday.


-JPB
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

mike weber wrote:
> On Sat, 19 Apr 2008 08:27:08 -0800, Offbreed
>> Uh-huh. Einstein is applicable sub light. How do we know the equations
>> are applicable FTL?
>
> Irrelevant; the "action at a distance" effect is part of the sub-light
> universe.

I guess I don't understand the "action at a distance" part, then. All
you can do is "observe at a distance", and in the past.
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

On Sun, 20 Apr 2008 04:00:50 -0700 (PDT), an orbiting mind-control
laser made Quadibloc <jsavard DeleteThis @ecn.ab.ca> write:

>But if your FTL drive obeys the laws of Special Relativity, so that
>its behavior is *exactly the same in all inertial reference frames*,
>then by jumping off from suitably fast-moving but slower than light
>starting points in both directions, one can appear to be moving
>backwards in time from Earth's vantage point on both legs of the
>journey, and arrive back on Earth up to eight years before you left,
>*even* with an FTL drive only capable of 1.01c *as viewed from the
>perspective of the slower than light frame the ship was in when it
>transitioned*.

Color me dense, but I just don't see it.


'Appearing' to move back in time and 'actually' moving back
through time are, to me, two completely different kettles of fish.

I don't see how the 'appearance in one frame of reference can make
it a real effect in another.


Maybe I wasn't a bad idea to turn down that invitation by the
Physics Department inviting me to change majors over to Physics after
freshman year in college.

-JPB
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

On Sun, 20 Apr 2008 04:00:50 -0700 (PDT), Quadibloc
<jsavard.DeleteThis@ecn.ab.ca> wrote:

>But if your FTL drive obeys the laws of Special Relativity, so that
>its behavior is *exactly the same in all inertial reference frames*,
>then by jumping off from suitably fast-moving but slower than light
>starting points in both directions, one can appear to be moving
>backwards in time from Earth's vantage point on both legs of the
>journey, and arrive back on Earth up to eight years before you left,
>*even* with an FTL drive only capable of 1.01c *as viewed from the
>perspective of the slower than light frame the ship was in when it
>transitioned*.

In this regard deChancie's "Starigger" books (Starrigger, Red Limit
Freeway and Paradox Alley) make excellent use of the concept, in which
the protagonist and his friends basically drive a super-semi-trailer
rig ("crewed" by an AI with his dead father's personality) and the
baddest '57 Chevie ever seen in a complete circle of Space and Time on
an interstellar freeway... (It all makes sense in the end - well,
okay, maybe the aliens who say "Blue!" don't, but otherwise...)

Long OP, but worth it if you can find them. But i *don't* recommend
reading just one in hopes of finding the others, because it's really
one long story in three parts.
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

On Sun, 20 Apr 2008 08:46:23 -0400, Dahak
<Dahak_II DeleteThis @theXOUTfifthimperium.com.invalid> wrote:

>'Appearing' to move back in time and 'actually' moving back
>through time are, to me, two completely different kettles of fish.
>
> I don't see how the 'appearance in one frame of reference can make
>it a real effect in another.

It's all relative, man.
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

On Sun, 20 Apr 2008 09:50:59 -0400, an orbiting mind-control laser
made mike weber <fairportfan.DeleteThis@gmail.com> write:

>On Sun, 20 Apr 2008 08:46:23 -0400, Dahak
><Dahak_II.DeleteThis@theXOUTfifthimperium.com.invalid> wrote:
>
>>'Appearing' to move back in time and 'actually' moving back
>>through time are, to me, two completely different kettles of fish.
>>
>> I don't see how the 'appearance in one frame of reference can make
>>it a real effect in another.
>
>It's all relative, man.

Ouch...
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

On Sun, 20 Apr 2008 04:00:50 -0700 (PDT), Quadibloc
<jsavard RemoveThis @ecn.ab.ca> wrote:

>But if your FTL drive obeys the laws of Special Relativity, so that
>its behavior is *exactly the same in all inertial reference frames*,
>then by jumping off from suitably fast-moving but slower than light
>starting points in both directions, one can appear to be moving
>backwards in time from Earth's vantage point on both legs of the
>journey, and arrive back on Earth up to eight years before you left,
>*even* with an FTL drive only capable of 1.01c *as viewed from the
>perspective of the slower than light frame the ship was in when it
>transitioned*.

Which is why I say that a drive that leaves the universe, such as the
hyperdrive of the Honorverse, is not subject to this restriction.
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

On Apr 20, 6:15 pm, Loren Pechtel <lorenpech....TakeThisOut@hotmail.invalid.com>
wrote:
> On Sun, 20 Apr 2008 04:00:50 -0700 (PDT), Quadibloc
>
> <jsav....TakeThisOut@ecn.ab.ca> wrote:
> >But if your FTL drive obeys the laws of Special Relativity, so that
> >its behavior is *exactly the same in all inertial reference frames*,
> >then by jumping off from suitably fast-moving but slower than light
> >starting points in both directions, one can appear to be moving
> >backwards in time from Earth's vantage point on both legs of the
> >journey, and arrive back on Earth up to eight years before you left,
> >*even* with an FTL drive only capable of 1.01c *as viewed from the
> >perspective of the slower than light frame the ship was in when it
> >transitioned*.
>
> Which is why I say that a drive that leaves the universe, such as the
> hyperdrive of the Honorverse, is not subject to this restriction.

FTL drives are, indeed, not necessarily subject to that restriction.
In the Honorverse, particularly, we have currents and rapids in the
space in which FTL vehicles travel. So that space can be said to
define a frame of reference.

John Savard
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w.. 

On Apr 20, 6:15 pm, Loren Pechtel <lorenpech....DeleteThis@hotmail.invalid.com>
wrote:
> On Sun, 20 Apr 2008 04:00:50 -0700 (PDT), Quadibloc
>
> <jsav....DeleteThis@ecn.ab.ca> wrote:
> >But if your FTL drive obeys the laws of Special Relativity, so that
> >its behavior is *exactly the same in all inertial reference frames*,
> >then by jumping off from suitably fast-moving but slower than light
> >starting points in both directions, one can appear to be moving
> >backwards in time from Earth's vantage point on both legs of the
> >journey, and arrive back on Earth up to eight years before you left,
> >*even* with an FTL drive only capable of 1.01c *as viewed from the
> >perspective of the slower than light frame the ship was in when it
> >transitioned*.
>
> Which is why I say that a drive that leaves the universe, such as the
> hyperdrive of the Honorverse, is not subject to this restriction.


It isn't a "restriction". The effects that we are trying to describe
are independent of how FTL travel is achieved. The only difference
using a "exit the universe, travel a shorter distance, re-enter the
universe, but still get to your destination before a light beam" drive
makes is that your progress between departure and arrival are hidden
from view. You still get there before you left.
 >> Stay informed about: Setting the Clock: the Planet way, the navy way, and the w..