Transmitting information using gravitational waves

[Paul Colby]

Essentially no average motion of the object as a whole. But individual atoms in the object are certainly moving: that is what "strain" means.

Yes, and your statement very helpful and reminds me why I work in the TT gauge. How is the word "moving" defined in your statement? In the TT gauge with the interatomic forces set to zero (for argument sake) the atoms remain stationary with respect to the chosen coordinates while the interatomic distances change by virtue of the metric strain. This geometrically strained configuration of atoms will have a displacement current and associated electric fields. All this happens with the atoms stationary wrt the chosen coordinates.

Clearly the interatomic forces are at play so even in TT coordinates the atoms will accelerate with the acceleration govern by the equations of motion given in post #29. One must solve this dynamical problem in order to have a complete picture.

 

[PeterDonis]

How is the word "moving" defined in your statement?

The proper distances between at least some pairs of individual atoms are changing with time (if you like, proper time of either atom of a given pair).

 

[Paul Colby]

The proper distances between at least some pairs of individual atoms are changing with time (if you like, proper time of either atom of a given pair).

Hum, motion was always defined relative to a frame. Sounds like a really confusing definition.

 

[PeterDonis]

motion was always defined relative to a frame

If you insist on doing this, you can always define a proper reference frame for one atom (basically Fermi normal coordinates centered on its worldline), and then look at whether adjacent atoms have coordinate motion in this frame.

 

[Shane Kennedy]

Is there anything in current theory which could allow faster-than-light signals of any sort ?

 

[PeterDonis]

Is there anything in current theory which could allow faster-than-light signals of any sort ?

No.

 

[mrad]

To look at gravity wave communication from a radio engineering perspective, a good place to start is John D Kraus' (inventor of the helical antenna in the 1940s and professor at Ohio State for many years) 1991 article, "Will Gravity Wave Communication be Possible?" The difficulty in producing and detecting GW is analogous to poor impedance matching in an antenna connection.
http://ieeexplore.ieee.org/document/84527/