One of the most basic assumptions of fundamental physics is that the different properties of mass—weight, inertia and gravitation—always remain the same in relation to each other. Without this ...

When an object moves extremely fast—close to the speed of light—certain basic assumptions that we take for granted no longer apply. This is the central consequence of Albert Einstein's special theory ...

In Newtonian physics, space and time had their independent identities, and nobody ever got them mixed up. It was with the theory of relativity, put together in the early 20th century, that talking ...