*Post by beda pietanza*a SR K frame measuring an object in K' frame gives a certain result

Remedial tutorial: There is no such thing as "a SR K frame". What you are presumably trying (and failing) to say is: Given two systems K and K' of inertial coordinates, moving relative to each other with mutual speed v, an object B at rest with spatial length L in terms of K' is moving with speed v and has spatial length L*sqrt(1-v^2/c^2) in terms of K. Likewise an object A at rest with spatial length L in terms of K is moving with speed v and has spatial length L*sqrt(1-v^2/c^2) in terms of K'.

Also, please note that in terms of any other system of inertial coordinates K", moving with speed u relative to K', the spatial length of B (at rest in K') is L*sqrt(1-u^2/c^2).

*Post by beda pietanza*Then if the K frame jumps to another speed...

No, K is a specified system of inertial coordinates, it does not "jump". What you are trying (and failing) to say is: Suppose object A is initially at rest in K and is then accelerated to a different state of motion so that it comes to rest in another system of inertial coordinates K" that is moving with speed u in terms of K'.

*Post by beda pietanza*while the frame K' and its object [B] stays still. The new measurement, of the same still

object in K', changes

What you are trying to say is: The spatial length of B in terms of K" is L*sqrt(1-u^2/c^2). This was always the length of B in terms of K". Of course, the length of B in terms of K is still L*sqrt(1-v^2/c^2), and the length of B in terms of K' is L. None of these has changed. All that has changed is that A was initially at rest in terms of K and now it has been accelerated so it is at rest in terms of K".

*Post by beda pietanza*What the frames K are measuring...

There are not multiple frames K, there are three inertial coordinate systems under discussion, K, K', and K". Also, please note that frames do not measure things; rather, things have spatial and temporal relations in terms of specified systems of coordinates.

*Post by beda pietanza*are the effects of the changes that took place only in the K frame due to the

changing of its absolute speed

The inertial coordinate system K does not change, nor do any of the others. These coordinate systems are related by certain linear transformations because they are in relative motion. An object has infinitely many speeds at any given instant, depending on the system of coordinates. The spatial extent of B does not change in terms of any inertial coordinate system when we accelerate A. This has been explained to you before. Have you forgotten?

*Post by beda pietanza*that has logically affected the rulers and the clocks of K frame itself,

No, K is an inertial coordinate system, and all the rulers and clocks at rest in K do not change merely because we have accelerated object A. The only thing that changes by accelerating object A is that object A's state of motion changes, and it reaches an equilibrium configuration when it comes to rest in K" that is congruent to its configuration in terms of K when it was at rest in K.

*Post by beda pietanza*so when SR claims to do a measurement...

Special relativity is a theory, it does not claim to do measurements. Special relativity asserts that inertial coordinate systems, such as K, K', and K", are related by Lorentz transformations.

*Post by beda pietanza*what is really measured is not a given object solely, but the measuring tool is

measured with the object measured in an inextricable mixture.

What you are trying (and failing) to say is that objects are described in terms of inertial coordinate systems, and those systems are related by Lorentz transformations. YTour phrase "measure solely" makes no sense, like one hand clapping. Understand?

beda

I don't give to SR frames any properties that you assign them, to me they just represent the positions

of objects in space and time nothing else associated to that.

to understand what is the working (math) mechanism of a SR frame I go like this:

in a moving SR frame the ruler is contracted to sqrt(1-v^2); v is the speed of the SR frame

the clocks ( having the time rate of sqrt(1-v^2), at two ends of the ruler, are offset so, that the the far end clock

(in the direction of the movement) is retarded of a value of v (in terms of local time of the SR frames) due to the Esynchro

with this setting any SR frame can see any other SR frame as having the ruler (whose real value is sqrt(1-v''^2)

as having the value of sqrt(1-vrel^2); where vrel is given by the formula

vrel= (v'+v'')/(1+(v'*v'')); v' and v'' are the absolute speeds of the two frames.

all the math story of SR is above, all the physical properties, associated to the SR math model, are illusory.

please don't loose time to repeat your mantras, beside the perfect math, for macroscopic objects, high speeds larger than a very

low fraction of c are forbitten, so your SR is only a math model, just that.

(physicists have to work somehow)

cheers

beda