A clear, nontechnical account explains relativity by contrasting touch-based everyday intuitions with observations of light and motion, using thought experiments to show how measurements of length and time depend on an observer. It develops special relativity from the constancy of light speed to consequences such as time dilation, length contraction, spacetime intervals, and the unity of mass, momentum, and energy; then extends to gravitation as geometry and discusses evidence and proofs. Concluding chapters examine conventions in physics, the elimination of force concepts, questions about the finiteness of the universe, the nature of matter, and broader philosophical implications.