Olaf Roemer discovered in 1675 that Io’s moon makes one revolution around Jupiter in 42.5 hours. But this period does not remain constant. As the Earth moves away from Jupiter, each subsequent eclipse of Io occurs slightly later than the previous one. The lag is due to the fact that light travels the increasing distance between Jupiter and Earth in a longer time. Dividing the length of the diameter of the earth’s orbit by the time delay, he obtained the speed of light = 227,000 km / s.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.