## onsdag 17 juli 2024

### Galilean Relativity returns with 2019 Meter Standard

 Galileo is back 2019 and Einstein leaves the scene.

The 2019 SI Standard specifies spatial length scale (meter) in terms of travel time of light as measured by a caesium atomic clock under the common agreement that the speed of light (in vacuum) is exactly 299792458 meter per second.

This means that since 2019 the main postulate of Einstein's Special Theory of Relativity SR of the constancy of the speed of light in all inertial Euclidean coordinate systems moving with constant velocity with respect to each other, no longer is a postulate about physics, but simply an agreement of how to specify the length scale in any given inertial system. This means that SR is void of real physics, since the other postulate of SR is also void of real physics.

This means that modern physics after 2019 is not the same as before, since modern physic is based on SR which after 2019 is void of physics.

SR is thus after 2019 no longer a relativity theory about real physics, and it is natural to ask what kind of relativity theory we are facing after 2019?

We then consider two coordinate systems $X$ and $X^\prime$ moving with constant velocity $v$ with respect to each other, sharing a common time $t$ set by identical caesium clocks in the two systems. Let us consider $X$ to be at rest and the origin of $X^\prime$ following the trajectory $x=v*t$ in the space-time coordinates $(x,t)$ of $X$, with the connection $x^\prime = x-v*t$ to coordinates $(x^\prime ,t)$ in $X^\prime$.

Let us now consider an object $O$ at rest somewhere in $X$ and determine its $x$ coordinate in $X$ by according to the SI Standard sending a light signal from the origin of $X$ and measure its travel time to reach $O$ and then translate that into distance with 1 second corresponding to $299792458$ meter. If the travel time is 1 second, then  $x=299792458$ for all $t$. This will then be the length of a straight bar reaching from $x=0$ to $O$.

Let us now seek to determine the distance from $O$ to the origin of $X^\prime$ at some given time $\bar t$. With the SI Standard in mind we do this by sending a light signal from $x^\prime =0$ and record travel time to reach $O$. The situation is now different since $O$ is not stationary in $X^\prime$ but moves with velocity $v$ with respect to $x^\prime =0$. This influences the travel time making it longer if $O$ is moving away from $x^\prime =0$ and shorter if $O$ is moving towards $x^\prime =0$.

The effective speed of light in $X^\prime$ vs the moving object $O$ thus changes from $299792458$ to $299792458+v$ meter per second, if we for simplicity assume that $v$ is parallel to the direction from $x=0$ to $O$.  If the travel time is 1 second, then the distance to $O$ in the $X^\prime$ system is $299792458+v$ meter, to be compared with $299792458$ in $X$.

If $X$ and $X^\prime$ refer to human observers, then typically $\vert v\vert <1000$ and so distance in $X$ and $X^\prime$ will agree to 6 decimals.

We thus find that with the new SI Standard distance is relative as being different in $X$ and $X^\prime$ with a very simple conversion depending on the mutual velocity $v$.

We are then led to define the "rest distance/length" as the distance measured in a system where the $O$ is at rest.

The SI Standard thus brings physics back to Galilean relativity dismissing Einstein's SR with all its heavy baggage of Lorentz transformation, time dilation, space contraction, rest mass and myriad of paradoxes which nobody can really understand, only pretend to understand.

This amounts to a form of self correction formed by the International Committee for Weights and Measurements (CIPM) seeking to form a useful working Standard and then (without direct intent) happening to eliminate SR from physics since it is not useful.

We should thank CIPM for making life so much easier for both professionals, students and laymen. After an impasse of SR over 114 years, rationality is back to physics!

But this message has not yet reached the theoretical physics community still struggling to make sense of Einstein's theories. In particular, in one quick step it eliminates the main road block to advancement of modern physics as the incompatibility of relativity theory and quantum mechanics.

For more details of Galilean relativity in our time, see Many-Minds Relativity.