On Sun, Mar 2, 2014 at 12:13 PM, Edgar L. Owen <edgaro...@att.net> wrote:

> Jesse,
>
> To answer your final question. If I understand your 3 points correctly
> then I agree with all 3. Though I suspect we understand them differently.
> When you spring your 'proof' we will find that out.
>

Thanks for addressing the question. As I mentioned in my previous comment
to you, the proof has already been sprung--it is the Alice/Bob/Arlene/Bart
example from Feb. 9 at
https://groups.google.com/d/msg/everything-list/jFX-wTm_E_Q/pxg0VAAHJRQJwhich
I have asked you to address in at least ten different posts since
then.




>
> And to your first points. I agree completely that there is no objective or
> actual truth about VIEWS of simultaneity from different frames. That is
> standard relativity which I accept completely. But you still find it
> impossible to understand we can DEDUCE or calculate an ACTUAL physical
> simultaneity irrespective of VIEWS of it.
>
> And just as proper time invariance is NOT ANY VIEW but a deduction or
> calculation, we CAN use deductions and calculations that DO NOT correspond
> to any particular view to determine relativistic truth.... That such a
> methodology is permissible?
>
>
> Do you agree that the symmetric relationship defined by the twins
> executing the exact same proper accelerations at their exact same proper
> times is a meaningful physical concept? That we can speak meaningfully
> about a symmetric relationship?
>

Only in terms of coordinate-invariant characterizations of their paths,
like the proper acceleration as a function of proper time, or the total
proper time elapsed between departing and reuniting. There is no logical
reason that this symmetry in coordinate-invariant aspects of their trips
somehow forces us to say that a coordinate system where
coordinate-dependent aspects of their trips are symmetrical too represents
"actual physical reality" where other coordinate systems do not.

Suppose we lay out two measuring tapes on different paths between two
intersection points A and B, and these paths are geometrically symmetrical
in the sense that each one looks like a mirror image of the other if your
mirror is laid out straight between points A and B. Both tapes have their 0
markings coincide with the first intersection point A, and obviously since
the two paths are symmetrical, both measuring tapes will have the same
marking coincide with the second intersection point B. Obviously we could
draw different spatial coordinate axes on the plane, and in some coordinate
systems their paths would be symmetrical in coordinate terms--for example,
a pair of identical markings on each tape would have the same
y-coordinates, and their slopes at these markings would have the same
absolute value--while in others they would not.

I can sketch out a diagram if you can't visualize what I'm talking about,
but assuming you can, do you think that coordinate-based statements based
on a symmetrical coordinate system, like "the 4-centimeter marks on each
measuring tape have the same y-coordinate" would represent "actual
reality", whereas coordinate-based statements in other coordinate systems
would not?





> You've been referring to it as if you do. Note that the twins certainly
> consider it a meaningful physical scenario because they can exchange and
> execute specific flight plans on that basis.
>
> If so you agree that some frames preserve that real physical relationship
> and some don't?
>

No, I don't agree. ALL frames preserve the only symmetries I would
recognize as "objective" ones--same proper acceleration as a function of
proper time, same proper time when the twins reunite--while other
coordinate-depedent statements are not ones I would call a "real physical
relationship". Note that they are perfectly free to agree to use a
coordinate system where the coordinate descriptions of their paths are not
symmetrical, and "exchange and execute specific flight plans on that basis".



>
> If so please tell me why if we want to analyze that ACTUAL real physical
> relationship we should not choose a frame that preserves it?
>
>
> And second, do you agree my method is consistently calculating something,
> and that something is transitive, even if you don't agree it's a physically
> meaningful concept?
>


If you consider more than one pair of twins whose paths cross one another,
as I do in my Alice/Bob/Arlene/Bart scenario, then either your method leads
to a contradiction where two different ages of the same observer are judged
simultaneous, or else you'd have to drop one of the assumptions in your
method (meaning it'd no longer be quite the same method). One of those
assumptions was transitivity, so in principle you could drop that if you
wanted to avoid the contradiction I describe, but as I said in my previous
comment, it seems like a much more reasonable assumption to drop is the one
that says inertial clocks at rest relative to one another that are
synchronized in their rest frame must also be synchronized in p-time.
Though as I explain below, if you dropped this assumption I think you'd
also have to drop the assumption that clocks that start synchronized and at
rest relative to each other, and later accelerate symmetrically, will
remain synchronized in p-time.



>
> If not then please try to prove it's not unambiguous and transitive, using
> MY definitions of MY theory rather than your 3 points. In other words
> assume it and then try to disprove it works.
>

But what if your definitions don't include all the premises you actually
believe in? Shouldn't I be able to assume any premise that you would agree
is a part of your theory, even if you didn't originally think to mention it
in your "concise" statement?

Also, it seems to me that the premise you agreed to earlier (that inertial
clocks at rest relative to one another and synchronized according to the
definition of simultaneity in their mutual rest frame are also synchronized
in p-time) is directly IMPLIED by the idea that clocks that start out
synchronized at the same location which then accelerate symmetrically
remain synchronized in p-time. After all, for any pair of inertial clocks
that are synchronized in their mutual rest frame, at rest at positions X1
and X2, we can imagine that in the past they started out at rest in the
same frame at a position exactly midway between X1 and X2, synchronized
locally, and then they subsequently accelerated symmetrically to move
apart, then decelerated symmetrically to come to rest at X1 and X2. In this
scenario, they would obviously remain synchronized throughout in the frame
they started out at rest in, so when they come to rest again in this frame
they will still be synchronized.

Jesse

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