Spacetime and the Theory of Relativity

These chapters explain Einstein's theory of relativity accurately but without mathematics, using a simple geometric operation: drawing the reflection of a line. This approach is accessible to readers with no prior background, and illuminates the conceptual foundations well. Chapter 14 first shows how Einstein used the extraordinary physical fact that light has the same speed relative to any standard of rest, to conclude that whether two things happen simultaneously is relative: there is no answer to the question whether they are separated in time or only space, they are just in ‘spacetime’. Relativity of simultaneity is represented geometrically, and it is simply shown that moving objects shrink and moving clocks slow down. Chapter 15 addresses the twins ‘paradox’, and the implications of relativity for time, especially whether it abolishes the ‘present’; Gödel's spacetime, in which there are paths leading back in time is explained.