Physically and geometrically, a human is a four-dimensional entity: a continuous worldline spanning space and time, living within a higher-dimensional macro-manifold.
In relativity, time is not a separate force acting on a three-dimensional object. It is a physical axis woven together with the three spatial axes into a single four-dimensional continuum, spacetime. Your entire physical existence, from first cell division to final dissolution, is a continuous trajectory through that continuum. The trajectory is static: it does not move through time; it is extended in time, the way a road is extended in space.
The consequence is easy to state and hard to hold. You do not exist in three dimensions and travel through a fourth. Your organism is a solid four-dimensional structure permanently embedded in the block universe. The "you" that seems to be a three-dimensional person at a single instant is one cross-section of that structure.
- Worldline
- The continuous, static, four-dimensional trajectory of an organism through spacetime, from origin to dissolution. The physical body is the worldline, not a three-dimensional object sliding along it.
- Block universe
- The spacetime continuum considered as a single, fully extended structure in which all worldlines are embedded.