Re: GR ?

Significant Zero wrote: 
"Tom Roberts" <tjroberts@xxxxxxxxxx> wrote in message
news:SpBEe.3241$fx4.3153@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
| A rotation is a rotation -- in Euclidean space or in
| spacetime. Rotations affect projections of objects onto axes,
| but THEY DO NOT AFFECT THE OBJECTS THEMSELVES. A relative
| velocity is merely a rotation in the x-t plane. <shrug>

That seems fairly clear to mean that in your view time dilation and length
contraction are products of remote observation, measurement and perspective
and have no basis in physical reality in the same way that Picassos pictures
have no basis in physical reality other than from an interpretation of a
reality in his head. 

Where do you get such outlandish notions? Certainly not from what I wrote.

Yes, time dilation and length contraction are observational effects of rotations in spacetime, just as whether or not a ladder is wider than a doorway is an observational effect of rotations in space. But these have real, physical effects: pion beams in accelerators are many times longer than c*\tau (the distance pions could travel at speed c if there were no time dilation), and ladders do or don't fit through doorways.


This doesn't seem good grounds for presenting something
as a useful scientific interpretation.

SR itself, and what I wrote most definitely ARE "good grounds". But your fantasies (above, comparing to Picasso) are not. <shrug>


The ladder and doorway are fine by me untill a better example is presented
as presumably as the are physical reality, or examples of you should be able
to deal with them present in a SR\GR context and be able to state a result
so I have put your example in a SR\GR context to just confirme my
understanding of your position.
Ladder L to L 10ft long moving down page ar near c.
Doorway D to D 3ft moving across page at near c

             L



             L
             \/

   D
     >
   D

Will length contraction allow the ladder to pass through the door way
without them contacting each other if the relative intersecting positions of
the ladder and door were appropriate?

This situation is not amenable to analysis using just length contraction. You need to use the entire Lorentz transform. This is essentially the same as the "pole and barn paradox"; both are resolved by realizing that simultaneity is DIFFERENT in the two relevant inertial frames. Look in any elementary textbook on SR for "pole and barn".


A rough drawing of  physical facts

  D
       L                  L
  D

Time 5pm my garage {:-)
Ladder fits.

         L
 D

 D
        L

Time 5:10pm my garage {:-)
Ladder dont fit

Now do me as clear a one for time dilation and length contraction please.


The problem is that this page is Euclidean and those effects are Minkowskian.


| You keep insisting that this is a "difference" in the clock's tick
| rates. But in fact you have no basis for that particular prejudice --
| all the actual MEASUREMENTS show is a difference in MEASUREMENTS. And
| that could be due to EITHER a change in clocks' tick rates or in the
| signals used for the measurements.

!00% agree but which view are *you* taking and believe to be the facts ?
My view is still relatively immature and needs to be banged against others
views to knock the wood worm out so please state *your* view.{:-)

My interpretation is that NEITHER of those is an effective description. Instead, this is a manifestation of spacetime curvature. As I said: 
| In GR this is modeled NOT as a "change in tick rates", and not in a
| change of the local speed of the light signals used in the measurement,
| but rather as a curvature of spacetime.

You now seem to be claiming that "curvature of space-time" is a real
physical reality that produces an effect on real physical reality or even is
the real physical reality.

What is "physical reality"??? Certainly I don't know, and unless you have a direct channel to God, you don't either. What we humans can know is the results of experiments, and we can make models to explain many such results. GR is the most successful model known to date for an enormous number of such measurements in this domain.


I understand "curvature of space-time" as a real
physical reality to mean a relative change in space and time from one place
to another which you have denied, if this is not accurate please correct it.

See above -- you DON'T know what "physical reality" actually is. And never will....


I far as I am aware I don't have a personal prejudice, 

Right. That's your problem, or at least a major part of it....


the muon and clock
data seemed to support the actual physical reality of time and length
variance

See above. In seeking "physical reality" you are setting yourself up to fail....


so I was just working from the data as presented.

No! That's your problem -- you imposed your personal prejudice about what the data "mean" and how they relate to "physical reality", rather than merely accepting the measurements and asking: how can we MODEL these measurements?


If you are
categorically stating that time and distance are invariant except
*apparently* when measurements are not corrected for  observational
distortions then I need to look and rethink my position.

I'm saying nothing of the sort. But you do have a lot of rethinking to do....


| In fact, the MEASUREMENTS are exceedingly accurately predicted by GR,
| and in GR the intrinsic rate of clocks does NOT depend on either gravity
| or any velocity. All your statements clearly show that in order to
| understand this you need to STUDY.

This seems a clear statement that the twins scenario is a none factual red
herring.

I don't know what you mean here. Certainly real experiments implementing the twin scenario have been performed, and the predictions of SR/GR have been confirmed: the traveling (non-inertial) twin is QUITE CLEARLY younger when the twins reunite.

	See the FAQ for a reference to Bailey et al, who performed
	a twin scenario using muons traveling ~0.9995 c, using a
	storage ring.

Note please that I have repeatedly stated that length contraction and time dilation are the results of perspective (geometrical projection), and they are frame dependent. But the twin scenario involves elapsed proper time over different paths, and that is NOT perspective and is NOT frame dependent.


Your definition of moving is CLEARLY different to mine and the dictionary
<shrug> {:-)
Try reading it

My dictionary says "move" means "to change place or position...". That is consistent with what I said, and is obviously inapplicable to time itself.


T = kinetic energy of system. Whats the kinetic energy of a field and how do
I calculate it ?

That depends on the type of field. But you want the LAGRANGIAN, not the energy (fields do not have "kinetic energy"). For the E&M 4-potential A_u and charged 4-current J^u the Lagrangian is:
k1 F^uv F_uv + k1 J^u A_u
F_uv = (d/dx^u A_v) - (d/dx^v A_u)
Where k1 and k2 are constants I forget, and I may have an overall sign error (I forget).


| > | Why do you think that it is impossible to cover the surface
| > | of a sphere with a single coordinate system? That is
| > | directly related to the impossibility I discuss here.
| > Latitude and longitude seem a fairly good system.
| But not good enough -- they do not COVER the sphere S^2. Specifically:
| there are coordinate singularities at the north and south poles. I
| repeat: you need to STUDY.

I see that as a bit of a red herring as my ref. on spherical geometry seems
happy to use latitude and longitude or simlair systems for dealing with
spheres <shrug> {:-)

Your ref. is not good enough. Those coordinates do not work at the poles. <shrug>

	This is an immediate corollary of a famous theorem known
	as the "hairy ball" theorem -- it is not possible to cover
	a sphere with hair without at least two cowlicks (the
	actual theorem is expressed in terms of vector fields, not
	hair). The poles are the "cowlicks" of latitude and
	longitude.


Tom Roberts	tjroberts@xxxxxxxxxx
.

Relevant Pages

  • Re: GR ?
    ... |> and have no basis in physical reality in the same way that Picassos ... So to get the ladder through the doorway you have to go and turn the ... |> | all the actual MEASUREMENTS show is a difference in MEASUREMENTS. ...
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  • Re: GR ?
    ... >> | spacetime. ... >> and have no basis in physical reality in the same way that Picassos pictures ... >> The ladder and doorway are fine by me untill a better example is presented ... >> | all the actual MEASUREMENTS show is a difference in MEASUREMENTS. ...
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