On November 21, 1676, the Danish astronomer Ole Rømer discovered the speed of light. Before Rømer figured it out, scientists thought that light travels instantaneously, or infinitely fast.

He calculated the speed of light to be around 225,300 km/s. Roemer did not know the precise distance to Jupiter, so his estimate was considerably different from modern figures of around 299,792 km ...

He concluded that light takes time to travel and we now know this is at a constant speed of 299,792,458 m/s. This clip is from the series Wonders of the Universe. This clip could be used as part ...