- 1879-1955. German-born theoretical physicist.
- Developed special and general relativity, redefining spacetime, gravity, and the relationship between mass and energy (E=mc²).
- Explained the photoelectric effect, confirming the quantum nature of light and contributing to the birth of quantum mechanics.
- Predicted gravitational waves, gravitational lensing, and the equivalence principle.
- His field equations describe the geometry of spacetime as shaped by mass-energy, the foundation of modern cosmology.
- Demonstrated that observation and measurement are frame-dependent, a principle echoed in decentralized consensus and cyber protocol design.