Re: lawless physics (fwd)

[Igal Galili <igal@vms.huji.ac.il>]

Hi John,
Thanks for your answer.  Let me make another small try to explain my
confusion.

Regarding your:

"the important fact that there is *no* limit on "how fast" you can get from
one place to another (which is all that can possibly matter to a traveler)
and, therefore, precious little meaning to the notion that nature imposes
any kind of "speed limit."

and:
" You *do* understand, don't you, that a person can, in principle, travel
from one object to any other in an arbitrarily short time within the
framework of special relativity."

Here is a deffinetely a correct statement: "Two events separated by a
space-like type of interval cannot be causually related."  This is in my
view a direct consequence of the limited velocity of any *material*
travelling.  So, there is the low limit for the time travel for any
material signal.   Or, may be your  "a person can, in principle, travel
from one object to any other in an arbitrarily short time" presumes the
travel of observer's thought from one subject to another, not travel
literally?

Now you say:

"the fact that no observer can *measure* a material object to be traveling
faster than the speed of light is a statement about *measurements* of space
and time, not about "how fast something can move.""

For me it simply sounds as a new interpretation of the theory of
relativity, and this was mu confusion due to a misinterpretation(?)

> > Do you distinguish between "the true movement" and "the measured one"?
>
> Of course.  Measurements of motion have well defined operational meaning.
> What could it *possibly* mean to talk about "true movement" within the
> framework of special relativity?

	Yes, but we seemingly diverse in further interpretation of this.
In my view, the SR-theory does NOT claim that there could be, in principle,
v>c (for material objects) but we simply cannot measure it as we have only
light signals available.
	The (positivistic) stance of Einstein was different from this: if
there is no observed function for ether, there is no ethere [he said:  no
reason to keep ether in any use in physics].  In the same way: if there is
no way to measure v>c motion, there is no such motion.  Any problem here?

Igal.