However, this belief of his was not to appear until many years later. .

             In 1609, Galileo heard about a spyglass that a Dutchman had shown in Venice. From these reports, and using his own technical skills as a mathematician and as a workman, Galileo made a number of telescopes with optical performances much better than that of the Dutchman"s instrument. "Many stars completely invisible to the naked eye are made easily visible by the telescope; hence their magnification should be called infinite rather then nonexistent." (Galileo 241) The astronomical discoveries he made with his telescopes were astonishing. Galileo discovered that there were mountains and craters on the surface of the moon, he observed the sun and discovered that it had black spots, which are now called sunspots, and as well he saw the four largest moons of Jupiter. Soon afterwards, Galileo became "mathematician and Natural philosopher," to the Grand Duke of Tuscany. He then continued his work on motion and on mechanics in Florence, and began to get in many disputes about Copernicanism. .

             In 1613 he discovered that when seen in a telescope that Venus showed phases like those of the moon, and therefore must orbit the Sun and not the Earth. "That is, Venus rivals the appearances of the moon; for Venus being now arrived at that part of her orbit in which she is between the earth and the sun, and with only a part of her enlightened surface towards us, the telescope shows her in a crescent form, like the moon in a similar position." (Fahie 123) Most astronomers of the time in fact favored the Tychonic System, which states that everything except the earth and the moon revolve around the sun; the idea that the earth was in motion was unheard of. However Galileo, with great verbal as well as mathematical skill, tended to use all of his discoveries as evidence for Copernicanism. Jesuit Cardinal Robert Bellarmine had instructed Galileo that he must not defend the concept that the earth is in motion.