At the age of nineteen - Discovered isochronism of the oscillating pendulum meaning duration of oscillations independent of the amplitude. In reality, the duration slightly increases in cases of great amplitudes, which Christiaan Huygens discovered.

Designed a pendulum clock with special escapement, a "duplex" type (independent under-dial work and impulse). He made progress with respect to the verge escapement of the first mechanical watches.

Galileo passed on his clock concept to his son, Vincenzio who started construction, in 1649, but his death, in the same year, meant the work was never completed.