One of you asked what it really means when physicists say “spacetime is geometry,” so here we go. In physics, geometry is not about shapes on paper. It is the rulebook that tells you how to measure distance and time between events. On a flat surface, straight lines are shortest. On a curved surface, the “straightest” path can look bent from the outside. Einstein’s move was to apply that idea to the entire universe. Mass and energy do not pull on objects directly. They change the geometry of spac