During this period he designed a new form of hydrostatic balance for weighing small quantities and wrote a short treatise, The Little Balance. Because of the Little Balance he began studies in motion which he studied for the many years. He applied for the chair of mathematics at the university of bologna but he didn’t get it. However his reputation was growing. He founded some ingenious theorems on centers of gravity. A year later he received the chair of mathematics. Galileo dropped bodies of different weights from the top of the famous Leaning Tower, to prove the speed of fall of a heavy object is not proportional to its weight, as Aristotle had claimed. He was abandoning Aristotelian instead taking an Archimedean approach to the problem. That decision made him unpopular. Galileo’s salary was higher there, he had responsibilities as the head of the family because his father had died in 1591 meant that he was pressed for money. His university salary could not cover all his expenses, and he tutored students privately. He also sold a proportional compass, or sector, of his own type, made by an artisan which he employed in his house. It might be financial problems that caused him not to marry, but he did have an arrangement with a woman, Marina Gamba, who bore him two daughters and a son. Galileo found out that the Netherlands had an invention that magnifies things from a far and makes it up close. Galileo quickly figured out how to improve it and practiced the art of lens grinding and made some of the most powerful telescopes of his time. In the fall of 1609 he began to study the moon and it phases. He found out that it is not like they thought it is rough and rigid. In January 1610 he found out that Jupiter has three moons and can see more star with the telescope than the naked eye.