Re: How was the speed of light first determined?

Ole Roemer, a Danish astronomer, discovered that there was an apparent
advance and retardation of the eclipses of the moons of Jupiter depending
on the distance from the Earth to Jupiter, and correctly realized that
this time change was due to the finite speed of light.  This was in
the late 17th century.  I don't think his value was terribly accurate,
but at least it was in the right ballpark.