[shthed]

https://en.wikipedia.org/wiki/R%C3%B8mer%27s_determination_o...

https://en.wikipedia.org/wiki/Speed_of_light#First_measureme...

Another interesting thing about using the timing of moon eclipses:

> Galileo proposed a method of establishing the time of day, and thus longitude, based on the times of the eclipses of the moons of Jupiter, in essence using the Jovian system as a cosmic clock. The times of the eclipses of the moons could be precisely calculated in advance and compared with local observations on land or on ship to determine the local time and hence longitude.

https://en.wikipedia.org/wiki/Galilean_moons#Determination_o...