Activities of which Galileo Galilei and Sir Isaac Newton are most closely associated

Galileo Galilei and Sir Isaac Newton are known to be most closely associated with conducting investigative experiments. Sir Isaac Newton even though an egotistical person, he always recognized the work of those people earlier than him, most especially the works of Galileo Galilei. Both are also mathematicians, authors of books, a well-known scientist and a person who disagree with the church. Isaac Newton discovered the gravity force while he is sitting under the tree. Meanwhile, Galileo has an activity that is most closely associated with it. It is when he observed that the objects are going back to their natural position similar to an apple that falls and trying to go back to the ground.