What about gravity?

• equivalence principle, Galileo experiment
  rocket Gedankenexperiment
• strong lensing: 1919 eclipse; galaxies
• gravitational redshift: Pound & Rebka (1960)

Relativistic Cosmology

The Structure of Cosmological Spacetime

• cosmological principle: maximal symmetry
• spaces of constant curvature
  coordinates: 2-sphere
• geometry of the universe
• Friedmann-Lemaitre-Robertson-Walker cosmic line element