As a trained (though non-practicing) physicist, I would like to point out that your comment varies between wrong and meaningless. Conservation of energy is a consequence of the time symmetry, i.e. the time variable not being explicitly present in the Lagrangian or Hamiltonian description of the system under consideration (see Noether’s theorem). There are perfectly good relativistic Lagrangians where energy is not conserved (usually because the system is not closed).
Conservation of energy is a logical consequence of the fact that experiments performed in different places or at different speeds turn out the same way. In other words
That describes conservation of momentum, if anything.
Also note that “global” energy is most emphatically not conserved in our expanding universe, and not even well-defined. All that is defined and (locally) conserved is the stress-energy tensor field.
There is also no injunction against FTL in either special or general relativity, though for different reasons. In SR FTL leads to time travel, while in GR it leads to the initial value problem being not well-posed, a rather technical point.
As a trained (though non-practicing) physicist, I would like to point out that your comment varies between wrong and meaningless. Conservation of energy is a consequence of the time symmetry, i.e. the time variable not being explicitly present in the Lagrangian or Hamiltonian description of the system under consideration (see Noether’s theorem). There are perfectly good relativistic Lagrangians where energy is not conserved (usually because the system is not closed).
That describes conservation of momentum, if anything.
Also note that “global” energy is most emphatically not conserved in our expanding universe, and not even well-defined. All that is defined and (locally) conserved is the stress-energy tensor field.
There is also no injunction against FTL in either special or general relativity, though for different reasons. In SR FTL leads to time travel, while in GR it leads to the initial value problem being not well-posed, a rather technical point.