Visualize worldlines, light cones, and causality in spacetime
Timelike: ds² > 0 (causally connected, can influence each other)
Lightlike: ds² = 0 (light rays, photons)
Spacelike: ds² < 0 (causally disconnected, cannot influence)
In 3D time theory, this extends to: ds² = dt₁² + dt₂² + dt₃² - dx² - dy² - dz²