In the book Why Does E=mc²?, authors Brian Cox and Jeff Forshaw provide a comprehensive guide to understanding Einstein’s most famous equation and its profound impact on our world. They explain how space and time are inextricably linked into a four-dimensional fabric called spacetime, where the speed of light serves as a universal constant. The text breaks down the Standard Model of particle physics, illustrating how mass and energy are interchangeable and how symmetry dictates the laws of nature. Through various examples like star evolution and nuclear fusion, the authors demonstrate that energy is essentially locked-up mass. Ultimately, the work explores general relativity, showing how gravity is not a traditional force but a result of spacetime warping around massive objects.