(a) By conservation of four-momentum: ( (m,0,0,0) = (E_\gamma, E_\gamma,0,0) + (E_\gamma, -E_\gamma,0,0) ) in natural units ( c=1 ). This gives ( 2E_\gamma = m ), so ( E_\gamma = m/2 ). Restoring ( c ): ( E_\gamma = \frac{m c^2}{2} ).
Special relativity (150 problems) builds fluency with Lorentz transformations, four-vectors, and relativistic dynamics. General relativity (150 problems) starts from the equivalence principle and walks through curved spacetime, geodesics, Einstein’s equations, and key applications. (a) By conservation of four-momentum: ( (m,0,0,0) =
(The complete solution spans half a page with all intermediate algebra and a spacetime diagram.) “Relativity is often taught as a collection of astonishing results — time slows down, space contracts, black holes trap light. Yet without solving problems, these insights remain abstract. This book bridges the gap between conceptual understanding and technical mastery. Yet without solving problems, these insights remain abstract