What practical application did Galileo immediately recognize for the predictable eclipses of Jupiter's moons?

Answer

Determining longitude at sea.

Galileo recognized that the precisely timed and recurring eclipses of the Jovian moons could serve as a universal clock for synchronizing time across vast distances, which was crucial for calculating longitude.

What practical application did Galileo immediately recognize for the predictable eclipses of Jupiter's moons?
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