Giovanni
Cassini had a big impact on his field, Astronomy. Some of the things that we
owe to him is the estimate of the rotations periods of Jupiter and Venus. Back
in his times, this was an important discovery because it conflicted in the
theory of how the earth rotates.
He helped to discover
the speed of light (In an odd twisted sort of way), because when he was in
Bologa,, he saw the moons of Jupiter, and created an ephemeris, a table that
tracks moons when they’re orbiting. When Jupiter and the earth were far apart
from each other, the moons appeared to take longer to pass in front of Jupiter
than Cassini had said. From this theory,
Olaus Roemer used the ephemeris that Cassini made, Roemer estimated the speed
of light.
So, if it wasn’t for the ephemeris that Giovanni Cassini made, scientists today might not know the speed of light.