Quote from Jim Steinhardt's <jsteinha at cisco.com> personal message: >>a) light is slower in dense media > The index of refraction of glass is 1.5 vs 1.0 for > a vacuum. Hence, the speed of light in glass is 2 * 10 **8 m/s. That gives 60 ms RTT on 4000 mile line. Case closed. Thanks, Jim! --vadim