Problem 1.383

Demonstrate that the quantity $E^{2}-p^{2} c^{2}$ for a particle is an invariant, i.e. it has the same magnitude in all inertial reference frames. What is the magnitude of this invariant?

E^{2}-p^{2} c^{2}=m_{0}^{2} c^{4}, \text { where } m_{0} \text { is the rest mass of the particle}

Relativistic Mechanics