Speed of Light
discovered that what were previously thought to be stars were
actually moons of Jupiter -
proving that earth & it's moon were not the only "planetary
1676 - The eclipse of Jupiter and its moon Io gave
Danish astronomer Olaus Roemeran (Ole Rømer;
also Roemer) an opportunity to estimate the speed of
His observation was that the same eclipse was seen later or
sooner, depending on earth's proximity to Jupiter. This demonstrated
that light had a finite speed.
Rømer had measured celestial angles in order to use
triangulation to determine an estimate of the distance between
Earth and Jupiter.
Accounting for the time discrepancy in observation of the
same phenomenon, based on the distance between the two points,
he was able to provide the speed of 186,000 miles
an incredibly close calculation.
and The Moons of Jupiter at Rice University |
Moons of Jupiter at PHYS.org |
at Stanford University
Rømer at The Museum of Natural History
Determination of the Speed of Light at Wikipedia