Thursday 14 February 2019

Phase Velocity

Poul Anderson rationalizes FTL space travel with "phase velocity," here and James Blish rationalizes FTL communication with this same kind of velocity in The Quincunx Of Time. See also here.

However, by Blish's account, phase velocity is like the waves of contraction moving along a caterpillar's body faster than his body is moving as a whole. Thus, the FTL ultraphone works only if there is already a light-speed transmission for the phase velocity to move along. How could FTL travel, or communication, to a new destination work on this basis?

Also, the phase velocity is four times faster than light in Quincunx but only 125% light speed in Mission To The Heart Stars.

But I'm not technical.

4 comments:

Sean M. Brooks said...

Kaor, Paul!

The problem, of course, is that the entire matter of FTL travel is so highly speculative that it's very difficult to talk about rationally or in ways that maeke even semi-plausible sense. Poul Anderson, esp. in his Technic stories, was able to use the FTL hypothesis in ways that came close to being reasonable. Another pretty good use of FTL in science fiction was Jerry Pournelle and Larry Niven's Alderson Drive in their Co-Domimium series.

Sean

Nicholas D. Rosen said...

Kaor, Paul, Sean, and other readers!

Phase velocity can indeed exceed the speed of light, but, as far as I learned when I was a physics major, it isn’t possible to send information using a superluminal phase velocity (the caterpillar analogy isn’t bad).

Best Regards,
Nicholas

Sean M. Brooks said...

Kaor, Nicholas!

I'm reminded of how Poul Anderson whimsically said in one of his essays that if you plied a physicist with a few drinks, that scientist will forget about caution and start muttering that some of the hairier and wilder speculations about FTL just might be true. Frankly, I hope so!

Regards! Sean

Nicholas D. Rosen said...

Kaor, Sean!

I hope so too, but don’t think it very likely. Meanwhile, a perfectly sober physicist will teach advanced undergraduates about phase velocity, but it probably won’t give us FTL.

Best Regards,
Nicholas D. Rosen