I noticed some idiot claiming that, in 1700, China and India were ” more sophisticated scientifically than europe”. Nonsense, of course. Hellenistic science was more advanced than that of India and China in 1700 ! Although it makes me wonder the extent to which they’re teaching false history of science and technology in schools today- there’s apparently demand to blot out white guys from the story, which wouldn’t leave much.
Europe, back then, could be ridiculously sophisticated, at the highest levels. There had been no simple, accurate way of determining longitude – important in navigation, but also in mapmaking. For ships the best solution was Harrison’s marine chronometer (insensitive to temperature variations), but before that, astronomers used the Galilean moons of Jupiter as a natural clock in the sky – observing when the moons entered or exited the shadow of Jupiter. Comparing this with predicted times in astronomical tables, you could determine the local time, and from that your longitude. Not the most practical method on shipboard, but quite useful on land.
Before this technique, estimates of longitude were crappy, and maps showed it. Afterwards, maps stop looking like something drawn by a sozzled ten-year-old :
In the course of playing with this technique, the Danish astronomer Ole Rømer noted some discrepancies in the timing of those eclipses – they were farther apart when Earth and Jupiter were moving away from each other, closer together when the two planets were approaching each other. From which he deduced that light had a finite speed, and calculated the approximate value.