Physics as Agreement is Not Real Physics

This is a further clarification of recent posts on units of time and length. 

The International System of Units SI defines 7 base units starting with time (seconds) and length (meter) as a universal system to be used in science and technology. 

The second (s) is defined by taking the fixed numerical value of the cesium frequency, the unperturbed ground-state hyperfine transition frequency of the cesium-133 atom, to be exactly 9192631770.

The meter (m) is defined by taking the fixed numerical value of the speed of light in vacuum to be exactly 299792458 meter per second.

This system can be used at any place of the Universe, as long as there is light in vacuum and caesium-133 atoms to set the units. Very handy and completely universal! 

But there is a caveat: How can we know that the speed of light or frequency of caesium-133 is the same everywhere? Maybe there is light but no vacuum, and maybe the frequency of the caesium-133 atom varies with temperature, pressure and gravitation? 

We must thus be prepared that different observers setting up their equipment under different conditions to set their specific time and length scales, will not agree to the last decimal on measuring something of common interest. This is the same as expecting that different traditional craftsmen may have had a bit different ideas of thumb, feet and yard.

The key question with physics as agreement according to SI, is to what extent different observers using this standard will agree outside the SI standard. In particular, we may ask to what extent different observers moving with different velocities will agree on distances? A partial answer is given in Many-Minds Relativity. As long as velocity differences are small compared to the speed of light, there will be little disagreement on distance, but not so in general.

Summary: It is possible to make an agreement to define length by travel time of light agreeing on a specific speed of light. If you think that this agreement is more than an agreement, that it is in fact real physics established by agreement, then you are fooling yourself. This is what Einstein did with his Special Theory of Relativity. You may test if you have understood by answering the following question: Is it possible that the speed of light in fact is 299792457.99?

With all observers using the same type of caesium clock for which a dependence of inertial motion is unthinkable, there can be no time dilation between inertial observers, which shows that the Lorentz transformation is not physics,  as very well understood by Lorentz, but misunderstood by Einstein. SR is clearly non-physics since 2019, which should have been understood by everybody from the beginning. But Einstein was very smart and fooled a whole world.