A. Discovered the movement of pendulum produces a regular times measurement
B. Developed the telescope
C. Discoverd four satellites of Jupiter
D. All of the above
Explanation
Galileo was a natural philosopher, astronomer, and mathematician. He also made revolutionary telescopic discoveries, including the four largest moons of Jupiter.
Galileo Galilei is credited with creating his own improved version of the telescope in 1609, based on the design of the "Dutch perspective glasses".
Although he did not invent the telescope, his improvements to the design and his astronomical discoveries using the telescope made him a key figure in its history.