PX155 - I6 - mass, energy, and momentum

\vec{p} = γ m_{0} \vec{v}

E = γ m_{0} c^{2}

consider: $$E^{2}-p^{2}c^{2} = \gamma ^{2}m_{0}^{2}c^{4}\left(1- \frac{v^{2}}{c^{2}}\right)= \frac{\gamma^{2}m_{0}^{2}c^{4}}{\gamma^{2}}$$

∴ E^{2} - p^{2} c^{2} = m_{0}^{2} c^{4}

- $R H S$ is frame invariant - lorentz invariant