spacetime

Space-time is the unified four-dimensional mathematical concept combining three spatial dimensions (length, width, height) with time as a fourth dimension. Einstein's theory of relativity fundamentally reimagined space and time as inseparable rather than independent. Gravity doesn't pull objects—instead, massive objects curve the fabric of space-time, and objects follow curved paths through this warped geometry.

Einstein's theory meant time actually flows differently depending on gravity and velocity; this isn't metaphorical but measurably real. GPS satellites account for relativistic time differences or they'd become inaccurate within hours. Black holes represent extreme space-time warping where gravity becomes so intense that not even light escapes. Space-time is not intuitive; human brains evolved to navigate three spatial dimensions at low velocities where relativistic effects remain negligible.