What Role Does Simultaneity Serve in Physics?

Einstein starts out his 1905 Special Theory of Relativity SR by an analysis of simultaneity similar to that presented in 1898 by the mathematician Poincaré, showing that different human observers may have different conceptions of simultaneity.

It is natural to ask what role simultaneity may serve in a World without human observers with possibly different conceptions. Let us then in the foot steps of Leibniz connect space to co-existence connecting to simultaneity, and then connect time to change. 

The basic case concerns two point-like particles A and B which meet/collide at a specific point in space and time and then part. At collision A and B share simultaneity and coexistence, since collision requires both A and B to be at the same place and time. 

Is it then necessary for A and B to keep track of position in space and time, in order to prepare for collision? Like when docking into the space station for a rocket? Of course not, the collision takes place at some position in space and time which A and B happen to share which automatically satisfies simultaneity. Collision involves both particles as a simultaneous event. If you come too late to the party, you will miss it.

More generally, simultaneity is not an issue in physics, since all interaction ultimately is established by contact/collision. For an extended body co-existence as extended simultaneity is established by contact. For a very large body delay effects may arise.

We conclude that simultaneity is only an issue for human observers seeking to synchronise clocks in order to set up a system of global time for communication, travel and business/stock exchange, and for GPS. The moon does not need a clock or GPS to find its path around the Earth. 

In Einstein's SR, simultaneity is essential, while in physics it is not essential. This means that SR is not a theory about physics, only about human observers in SR equipped with old meter sticks and mechanical clocks. Unfortunately, this is not understood by modern physicists trained to view SR as a theory about physics, which is behind the present crisis of modern physics.

Many-Minds Relativity offers an alternative to SR as a theory about conceptions of human observers.