Who was the first to discover the speed of light?

The first person to discover the speed of light was Ole Rømer, which corresponds to option [C]. In 1676, Rømer, a Danish astronomer, made a significant breakthrough in understanding the speed of light through his observations of the eclipses of Jupiter’s moons, particularly Io. He noticed that the timing of Io’s eclipses varied depending on the Earth’s position relative to Jupiter. When Earth was moving away from Jupiter, the eclipses appeared to occur later than expected, and when Earth was moving towards Jupiter, they appeared earlier. Rømer concluded that these discrepancies were due to the finite speed of light, taking time to travel the varying distances between Earth and Jupiter. By estimating these delays, Rømer calculated that light takes about 22 minutes to travel a distance equal to the diameter of Earth’s orbit around the Sun. Although his calculations were not precise by modern standards, Rømer’s work was groundbreaking and provided the first quantitative estimate of the speed of light, fundamentally advancing our understanding of light and its properties.