On Thu, 6 Jul 2023 07:46:41 -0400, Jeffrey Schwartz wrote:

>On Wed, Jul 5, 2023 at 4:37?PM Jeff Zeitlin - editor at
>freelancetraveller.com (via tml list) <xxxxxx@simplelists.com> wrote:
>>
>> (Note: it's probably because I've never discussed relativity beyond the
>> layman's level, but I'm actually not entirely convinced that it necessarily
>> precludes FTL. That's not for this thread, however.)
>
>Freaking awesome video that shows the issue with relativity and FTL.
>Just amazing, straight forward and done at TL6 which makes it over the
>top when you consider that it was done with retrotech
>On the other hand, that it was done with really straightforward
>retrotech, it makes it really easy to understand the issue
>
>https://www.youtube.com/watch?v=tmdp3jd8rig

An interesting film, and done well - but it makes an assumption that
virtually every handwave of a FTL drive deliberately and specifically
breaks: That in order to achieve speeds of cee-plus from a standing start
(speed of zero), you must pass through every speed between (including cee
itself). Which in turn also assumes that your cee-plus is happening in the
space that we live in. But... FTL drives from SF don't do dat.

Traveller's Jump drive don't do dat. Jump drive puts you into a
not-our-space where we don't have referents to tell our "speed", we just
know that it seems to let us get from A to B at about 170 times as fast as
light does the trip staying in ourspace. For Jump 1. For higher jumps,
multiply 170 by the jump number.

John E. Stith's FTL from "Redshift Rendezvous" don't do dat, neither.
Stithian FTL also puts you into a not-our-space, but one in which
point-to-point congruency with ourspace reduces the distance between those
points - but by a greater factor than "cee" is reduced by, so that by going
at otherspace-relativistic speeds over shorter otherspace distances, you
come out in our space having gotten from A to B faster than light could
have done it staying in ourspace.

The Stutterwarp from 2300AD don't do dat, neither. Stutterwarp handwaves
Quantum Tunnelling into something controllable, so that a ship in
Stutterwarp, although it remains in ourspace, is not actually moving, but
is instead instantaneously bamfing* from A to A-prime, where the ourspace
distance between A and A-prime is small relative to the distance between A
and B (the ultimate destination) - but in any case, the distance in
question is not "travelled".

Star Trek's warp drive don't do dat, neither. The warp drive puts the ship
in "subspace" (another not-our-space) where time and velocity are both
sign-reversed relative to ourspace, and the absolute magnitude of the
effective velocity is (in pre-TNG) the cube of the warp factor multiplied
by the speed of light in ourspace.

Weber's "hyper" from the Honor Harrington universe don't do dat, neither.
The hyper drive puts the ship into a selected level of not-our-space where
local speed is such that when you travel from A-equivalent to B-equivalent
in not-our-space, you end up travelling from A to B at an effective speed
that is a fixed multiple of your measured speed in hyper, and such that it
is also in excess of the speed of light in ourspace.

Drake's FTL drive from the RCN series don't do dat, neither. You leave
ourspace, slide around on the "surface" of lots of different "universes" in
"sponge space", each of which has variant physical laws, and if you've
followed the 'sailing directions' carefully enough, you come back into
ourspace where you wanted to be, having managed to get there faster than
light would do it while staying in ourspace.

The Streuven hyper drive from the Liaden Universe® don't do dat, neither.
In fact, it's a pretty good mapping to Traveller's jump drive, except that
rather than being quantized, time-in-jump maps more closely to ourspace
distance, and you're never provided with enough information in the stories
to know what the cee-multiplier is. Or even if it's constant.

The FTL drive from Cherryh's Compact Space don't do dat, neither. It gets
described in a way that maps most closely to the Streuven hyper drive,
above, but with certain other limitations and effects.

Alderson tramlines from Nivenpournelle's "Moties" universe (_The Mote in
God's Eye_ et sequelae) don't do dat, neither. Tramlines cheat; they
essentially say that points A and B aren't really as far apart as they seem
to be - but only if you take the shortcut. By analogy, light travels only
on the streets and highways of ourspace; the tramline is a path overland.
Any "FTL drive" that uses "wormholes" is essentially identical to the
tramline model.

I could go on, but there really aren't that many different FTL drives; they
all exploit one of the ideas above with different coats of paint, or maybe
with glitter or sequins glued on.

The point is, relativity (and I think we're talking specifically about
_special_ relativity) makes some core assumptions that we haven't proven
are invalid yet - but where we may not have explored all the edge cases
yet. Quantum mechanics hasn't quite been reconciled with what we know of
SR, which suggests that QM is either itself an edge case, or is a pointer
to the edge cases (just like very high speeds turned out to be an 'edge
case' for Newtonian fizzix). Maybe G-d _does_ play dice with the universe,
and H- might even roll them where H- can't see them...

* "bamf" is a technical term. In layman's language, it roughly means "a
discontinuity occurs wherein that which was at point A is no longer at
point A, but is instead at point A-prime, without having occupied any other
point in ourspace during the zero-time period over which the discontinuity
occurs.

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