spatial curvature

Spatial curvature describes how the shape of space itself is bent or curved, similar to how the surface of a sphere or a saddle is curved. In everyday experience, we see curvature in large structures like the Earth's surface, where straight lines eventually meet or diverge. On cosmic scales, space can be curved by mass and energy—positive curvature resembles a sphere, negative curvature a saddle, and zero curvature a flat plane. This curvature affects the paths of planets, light, and other objects, shaping the universe’s large-scale structure and evolution.