Gravitational Lensing, Redshift & Time Dilation: Observation, Measurement & Evidence

Strong lensing can create multiple images, arcs, and Einstein rings; weak lensing produces subtle statistical distortions; microlensing changes brightness without resolved image separation. Time and frequency effects depend on spacetime geometry rather than a material medium.

Solar-eclipse and radio observations confirm light deflection, galaxy clusters produce dramatic gravitational arcs, atomic clocks show gravitational time shifts over small height differences, and compact-star spectra can exhibit gravitational redshift.

Photons follow null geodesics through curved spacetime. Different trajectories and potentials create path delays and magnification. Clocks at different gravitational potentials trace worldlines with different proper times, and photon frequencies measured by those clocks differ accordingly.

Einstein rings, cluster arcs, weak-lensing surveys, atomic-clock height experiments, solar gravitational redshift, and compact-star spectra provide measurements. Time-delay lenses combine path length and gravitational delay.