Re: starship-design: Re: FTL travel

[Steve VanDevender <stevev@efn.org>]

Curtis Manges writes:
 > > I think _Spacetime Physics_ expresses the formulation of relativity that
 > > is in mainstream physical thinking, and its explanations are much
 > > clearer for beginning students than those in other texts I've seen.
 > > It's no more dogmatic than any other physics text I've read;
 > 
 > that's scary . . .

I suspect that if physics texts contained the amount of philosophical
hand-wringing needed to satisfy you, they'd be twice as big and even
harder to read.

 > Sure, polar vs. cartesian, and the day- and nighttimers _will_ agree
 > on the _distance_ to the point in question, but they will _still_
 > argue about its _location_, because they still have differing compass
 > references, one magnetic and one celestial. Sorry I had to throw that
 > in, but the authors should have caught it.

I don't see anything in Taylor and Wheeler's discussion that says that
the point is to find a way to agree about the location of something; the
point is to find relationships between the possible locations that
different observers measure.  Of course the daytimers and nighttimers
measure different locations, and they're not trying to convince you they
shouldn't; however, there is a simple way to relate the different
locations measured by the daytimers and nighttimers.  Similarly, one
measures different spacetime coordinates for events in different
relativistic reference frames, yet there are predictable relationships
between the coordinates in different frames based on the relationships
between the frames.

 > > Similarly, in different relativistic frames, one measures different
 > > coordinates for the same events, but the spacetime intervals between
 > > events that one obtains from those different coordinates is the same in
 > > all frames.
 > 
 > I understand this concept as presented, but I have a problem with it -- see below

You know, it doesn't matter whether you have a problem with it or not.
Lots of people have problems, conceptual or philosophical, with physical
theories; theories aren't out there because a mythical conspiracy of
powerful scientists are pushing those over ones that you might feel
better about.  Theories survive because they appear to model the
universe better than the known alternatives.  Progress in physics has
allowed us to explore phenomena well outside what humans can directly
experience, and it turns out that the universe doesn't work the way
your "common sense" makes you think it should in a lot of ways.

 > I'll buy that, but I seem to recall them presenting some paradoxes
 > which they admitted to being insolvable. I could be wrong on this,
 > though.

Cite one.

 > > I don't promote
 > > relativistic physics because I think it's the be-all and end-all of
 > > physical theories; I promote relativistic physics because it's clearly
 > > the best experimentally-verified theory we have now.  I'm willing to
 > > change my mind when something better comes along, but I haven't seen
 > > the better thing yet.
 > 
 > Could you comment, please, on Gaasenbeek's work?  (
 > www.rideau.net/~gaasbeek/index.html#contents ) Like I say, I'm not a scientist, but
 > I like this better than Autodynamics.

Again, it doesn't matter whether you like it or not; what matters is
whether Gaasenbeek's theories make measurably different predictions from
conventional theories, and whether those predictions can be confirmed by
experiment.

>From what I can tell Gaasenbeek believes there are some kind of "helical
particle wave" phemonena that he thinks explains various physical
phenomena better than relativity.  However, even he seems to admit that
there's no experimental proof for his idea, and from what I can tell he
isn't even making substantially different predictions than conventional
theories, just trying to explain them in a different way.

Two theories that make the same predictions in different ways aren't
really different theories.  However, scientists have tended to prefer
the theory that uses the least extra stuff to explain what's going on.

As for your rather lengthy discussion of the nature of time, I can say a
few things:

You apparently don't understand the idea of spacetime interval well
enough to properly criticize it.  Saying that it doesn't make sense to
you (and using a lot of sloppy analogies to show that you don't get the
idea) isn't a criticism of the idea.  Misstating what Taylor and Wheeler
say about spacetime interval isn't a criticism of the idea.  Claiming
that the relativistic characterization of time is "linguistic garbage"
despite it being mathematically simple and consistent isn't a criticism
of the idea.