Getting in Touch with Reality

In the first section of this book we’ve seen that the principle and theories of relativity say very profound things about the nature of reality. In some cases at least the implications of that principle and those theories are very counter-intuitive. From special relativity theory (SRT) we find that the inertia of things do not simply depend on their “rest masses.” Rather, their inertias depend on their energies, to which rest mass contributes but is not the only contributor. The locally measured invariant nature of the vacuum speed of light, required by the principle of relativity to preclude the identification of any preferred inertial frame of reference, forces us to treat space and time on the same footing, and leads to their conceptualization as spacetime.