Answer:
observing sunspots on the Sun and mountains on the Moon
Step-by-step explanation:
Galileo was an Italian Physicist and Astronomer and is regarded as the father of modern Physics.
It was previously believed that the objects in the heavens such as the sun, moon and stars were perfect and rough till he observed sunspots on the sun and mountains on the moon which indicates the surface of the moon is rough with mountains and craters.
Step-by-step explanation: