Kernel
Einstein is the figure who showed that Newton's framework is the low-velocity, low-energy approximation of a deeper geometry. The 1905 papers (special relativity, the photoelectric effect, Brownian motion) and the 1915 general relativity together constitute the second opening of the science layer.
Contribution
Special and general relativity. Photoelectric quantization (which fed quantum theory and won him the 1921 Nobel). The Einstein–Podolsky–Rosen argument (1935) that posed quantum entanglement as a foundational problem rather than a technicality. The cosmological constant — which he called his "greatest blunder" and which turned out to be approximately correct.
Civilization-scale significance
The figure in whom "physics is geometry" becomes a civilizational hypothesis. The 2025 cosmology that uses dark energy, the GPS that uses general-relativistic corrections, and the modern conception of spacetime as something that can be experimentally probed are all his.