What nationality was the man who determined that light has a finite speed?
Rømer's determination of the speed of light Rømer's determination of the speed of light was the demonstration in 1676 that light has a finite speed, and so does not travel instantaneously. The discovery is usually attributed to Danish astronomer Ole Rømer (1644–1710), who was working at the Royal Observatory in Paris at the time.
Abraham Zelmanov Abraham Zelmanov (May 15, 1913 – February 2, 1987), was a prominent scientist working in the General Theory of Relativity and cosmology. He first constructed, in 1944, the complete mathematical method to calculate physical observable quantities in the General Theory of Relativity (the theory of chronometric invariants). Applying the mathematical apparatus, in the 1940s, he established the basics of the theory of inhomogeneous anisotropic universe, where he determined specific kinds of all cosmological models — scenarios of evolution — which could be theoretically conceivable for a truly inhomogeneous and anisotropic Universe in the framework of Einstein's theory.