In the early age, many scientists agreed that the speed of light was infinite and could travel any distance. But evidence has found, many written records revealed that the Italian physicist Galileo Galilee was the first man to try to determine the speed of light. But he was unsuccessful in measuring the speed of light.
Briefly, in the mid-seventeen century, he conceived an experiment in which two people with covered lantern stood a known distance apart. One person uncovered his lantern and as soon as the other person saw the light, he uncovered his own lantern. Galileo attempted to record the time between lantern signals but it turned out to be unsuccessful as the distance involved was too small and light simply moved too fast to be measured this way.
In an around 1667, Danish astronomer Ole Roemer became the first person who successfully measured the speed of light, then he proved the light travels at a finite speed. His experiment was based on observations of the eclipse of the moons of Jupiter. In the ensuing centuries, a number of other scientists worked to determine the speed of light and, using improved techniques, came up with increasingly accurate calculations.
Roemer’s estimate for the speed of light was 140,000 miles/second, which is remarkably good considering the method employed.