Galileo, Galileo, Figaro
Believe it or not, but the speed of light was calculated well before we discovered that the universe is far greater in size than our galaxy. In 1676, Danish astronomer Ole Roemer studied Jupiter’s moons and discovered that their eclipses occurred sooner when Earth was closer to Jupiter. Conversely, said eclipses also happened later than predicted when Earth was farther away.
Thus, good ol’ Roemer became the first person to measure the speed of light. According to this Reddit user, we didn’t fully comprehend the size of the universe until 250 years after Roemer’s big discovery. That boggles the mind when you think about it. We utilize light-years as a form of measurement for space. Roemer was just ahead of his time.