All You Zombies. . .

Yesterday's post got me thinking about various forms of communication from science fiction.

The "paired devices", non-interceptable is not uncommon and usually tied to quantum entanglement or the like.

Another one I've seen plays games with "phase velocity". This is a concept from waveguides where the phase velocity (speed at which changes of phase move thru the guide) is higher than the "group velocity".

This results inn a system where you can't communicate across a link until a signal from you has reached them. Once that happens, you can (in fictional theory) send messages to them FTL. They have to send a signal back to be able to send the other way.

This has some fun limitations, such as it being essentially useless except between "fixed" stations. and it taking a long time to set up any sort of network.

If you have FTL *travel*, then you can cheat and place relay station at some convenient distance apart and send signals to start links between *them*. Speeds things up a lot but requires a lot more infrastructure.

There's also the question of *how* much faster than light your signals travel.

Next one is a weirdie. Dirac radio,

With normal EM communications, a signal travels thru space like a ripple across a pond. The ripples spread at the speed of light.

With Dirac radio, the signals act like raising or lowering the level of the pond uniformly. So they are instantaneous. Of course there are a *few* problems. Like where does the energy come from? And what happens if several transmitters are operating at the same time. These are pretty much handwaved away.

Obviously *everyone with a receiver gets the signal at the same time, and it's not directional.

James Blich who was the first aothor to use it, came up with some other interesting effects. :-)

And then there are the "simple" ideas where the signal (of whatever sort) just travels FTL (buut not at infinite speed) and drops off with distance. And can have direction finding.

Can't think of any others at the moment.