Mixing Space and Time is Not Physics

According to Leibniz space is coexistence as something sharing the same time, while time is a measure of change of coexistence. The atoms making up the arm of a clock coexist and the change of the position of the arm expresses passage of time. The shadow of a sundial expresses coexistence, while the slow change of the shadow represents a measure of rate of time geared by the Sun.

The 2019 SI Standard defines rate of time in seconds by a standard caesium clock, while spatial distance in meters is defined in terms of travel time of light setting the speed of light to be exactly c=299792458 meter per second. Here time and space are clearly separated and cannot be mixed together into some form of space-time, which has come to serve as a mantra modern physics introduced by Einstein and followed up by the mathematician Minkowski.

To make it possible to speak of space-time Einstein introduced the new concept of event as physics which can be described by a single space coordinate $x$ at some specific time $t$ as a space-time coordinate $(x,t)$. This eliminates all physics of spatially extended bodies consisting of coexisting atoms, which cannot be described by a single spatial coordinate, that is essentially all of physics. What remains is an idealised flash taking place at $\bar x$ at time $t=0$ and then following the trajectory $x=\bar x+ct$. Einstein was then led to the Lorentz transformation supposedly connecting space-time coordinates of one and the same event in different coordinate systems, which led him to the Special Theory of Relativity SR.

An analysis of SR shows that it is based on the false premise that a flash of light sent out in one coordinate system can be identified with a flash sent out in a different coordinate system. 

The result is that SR does not describe the physics of extended bodies consisting of coexisting spatial parts but only space-time events and then in an incorrect way. The net result is that it is not mandatory to replace Newton with Einstein, as the main feature of modern physics, as discussed in recent posts.