:It was already in 1671 that Ole Rømer determined that the speed of light was finite (and his estimate of the speed of light was not that bad). It is important to understand that the finite speed of light is not (in itself) a relativistic effect, rather it certainly is relevant to Newtonian physics. Also, it is not something that requires contemporary measuring equiment to realize although you do need the light to travel a significant distance in order to apprecaite the effect. A (possibly somewhat dated) everyday example, is that if one gets a phone line via satellite, then there is an audible delay due to the about 1/4 lightsecond up and down to the satellite. Although the prevalence of intercontinetal fiber connections such phone connections may be rare nowadays, the effect is real (and Newtonian).