What was the significance of Galileo observation of the four Medicean star near Jupiter

He later observed a fourth star near the planet with the same unusual behavior. By Jan. 15, Galileo correctly concluded that they were not stars at all but moons orbiting around Jupiter, providing strong evidence for the Copernican theory that most celestial objects did not revolve around the Earth.

meteorologists would compare a new weather map with one 24 h old to see how fast a front is moving.

idk what the options are but

these is a strong electrostatic attraction between the ions hence a lot of energy is needed to overcome this attraction

this is why the boiling points are so high