On Tue, May 24, 2016 at 04:20:02PM +0000, Bruce  Johnson wrote:
>
> > On May 23, 2016, at 7:31 PM, Tim <xxxxxx@little-possums.net> wrote:
> >
> > Not at all.  Gravitational waves corresponding to highly nonlinear
> > changes in the structure of spacetime (e.g. opening a connection from
> > jumpspace) should be expected to be astronomically greater in
> > magnitude than everything else.
>

> Why? I may be visualizing this completely wrong, but the analogy I’m
> thinking is a rock placed (not thrown) halfway into a pond. That
> sets up a ripple as displaced water pushes out.

Spacetime behaves very differently from water.  For example, an object
moving at constant velocity does not radiate gravitational waves at
all.  An accelerating one does, but in most cases *extremely* weakly,
with radiated power something like G (m v a)^2 / c^5.  So for
Traveller vehicles, typically 10^-18 watts or less.

The scale of gravitational waves from jump emergence depends upon your
assumptions.

If you treat it like formation, transit, and collapse of a small
wormhole endpoint over time t, then the radiated energy from a
diameter d would be on the order of c^3 d^2 / (G t^2).  So if jump
emergence takes on the order of a few seconds, the gravitational
radiation during that time would be typically on the order of 10^36
watts.  Yes, this is a ridiculously large power, because folding,
spindling, and mutilating spacetime involves ridiculously large
energies.

If you merely treat it as the appearance of mass-energy into an
existing spacetime, then the changing monopole moment (which normally
isn't possible!) yields power about G m^2 c / d^2, where d is the
diameter of the body.  For Traveller starships, that's going to be on
the order of 10^10 watts.  LIGO might detect it if a ship emerged at
Earth's 100 D, but probably not at interplanetary ranges.  It would be
quite reasonable for more advanced detectors to do so, however.

Obviously the first assumption for jumpspace emergence yields very
much greater gravitational radiation than the second, but even the
second one is 10^28 times the power of ordinary waves from
acceleration.  The ratio is comparable to the that between a candle
and the Sun, and enormously greater than the ratio between a pin
dropping and a magnitude 9 earthquake.  To say "if you can detect one
then you can detect the other" is an error of scale far beyond the
normal range of such errors.

> Yeah, but if you have an interferometer with, say 100Km, or 10,000km
> arms? With TL12 or TL14 scale weapons-grade lasers?

Obviously I don't know what higher TLs will bring, but I'd be quite
surprised if a few extra TLs increased the sensitivity by a factor of
a quadrillion.

All I was saying is that the two cases of gravitational radiation that
you were calling similar are actually radically different, and
obviously the subsequent argument for universal tracking of non-jump
movement does not follow.

- Tim