Epur si mouve. -- And yet it does move.¹
[Apocryphal words himself after making his abjuration of heliocentricity]

This quotation from Galileo, which he proclaimed incessantly on his deathbed, is one of the most famous quotations of all time. Galileo Galilei was a pioneer of modern physics and telescopic astronomy. Throughout his life he wrote various books on these subjects. When a supernova appeared in late 1604, it interested Galileo so much that it led him to the field of astronomy. At first, Galileo vigorously opposed the Copernican heliocentric world system because the Bible supported the stationary Earth theory. However, after careful observations and examinations of planets, he became a firm believer in the Copernican theory. In 1632, he published a book called "Dialogue on the Two Chief World Systems," which discusses the validity of Copernicanism. The publication of that book eventually led to his imprisonment on "vehement suspicions of heresy."² But a belief in the heliocentric systemæ the main thesis of the book existed even in Ancient Greece. And as a matter of fact, Galileo himself was never able to find a decisive scientific proof of Copernicanism. Outside of Italy, Galileošs influence was not great, except in making scientists conscious of the need for freedom of inquiry.³ Rather than with Galileošs beliefs themselves, the Church was more concerned with possible effects of the book on people. For example, Johannes Kepler (1571-1630), another astronomical scientist in the Renaissance era, also accepted the validity of the heliocentric model, but he was not penalized because of his belief. Then, why was Galileošs argument so controversial? It was controversial because the information that he provided was rather vivid and more understandable to all who read it than information that was given by other scientists. What made his work so understandable to his audiences was his unique use of images to illustrate his arguments. In this paper, I will be discussing some important methods he used to develop the images and the factors that made his images controversial, using one of the images from his book, "The Planets Revolving around the Sun," as an example.

Galileo once said, "Measure what is measurable, and make measurable what is not so."⁴ To measure, observe, and report distant stars, he indeed needed an instrument in order to measure what was not measurable. Most of Galileošs information was from his direct observations, rather than from old books, which other scientists, including Galileošs teachers, used to use.⁵ In 1609, Galileo invented a 30-power telescope.⁶ The invention of the telescope was truly an important one, because it enabled him to back up his theory. Without the telescope, the image "The Planets Revolving around the Sun" never would have been achieved because it allowed him to observe many things about the planets, including their satellites, their craters, and most important of all, their sizes, and their distances from the earth. The use of the telescope gave him great confidence about the information that he had observed. The image was drawn from Galileošs careful observations. For instance, in the picture, the size of the Sun is drawn the largest of all the other planets, at the same time, the sizes of Jupiteršs satellites are drawn the smallest. Galileo discovered even the satellites of Jupiter, with the help of his telescope. The image "Planets Revolving around the Sun," was the first image to illustrate Jupiteršs satellites. The usage of the telescope enabled Galileo to bring a vivid representation of the solar system. Ultimately, the telescope became the proof in backing up the descriptions of his representation of planets. By using his telescope to observe planets, Galileo determined that the Sun is actually at the center of the solar system and not the Earth.

With the development of the telescope came the need for a clear and precise writing and drawing technique in astronomy. The image "Planets Revolving around the Sun" is a simple diagram, which consists of various sizes of circles. The image was much simpler than a verbal description and it was better at conveying information. At the same time, through looking at the image, the readers were able to put less focus on languages. The visualization of the solar system helped the readers to memorize its information faster than reading descriptions, like the difference between watching a movie and reading a book about the same movie. Thus, the image helped readers to understand the text in more precise and quick manner. Galileo purposely drew the image to be simple, and yet as accurate as possible, so that people would be able to understand his argument without difficulty.

Galileo used a clear writing technique to support his image to boost its effect. In the book, "Dialogue on the Two Chief World Systems," Galileo used very terse yet sophisticated writing techniques to represent the solar system as clearly as possible. Hevelius, an astronomical scientist who lived in the eighteenth century, mentioned that Galileošs descriptions of the planets, "were curiously and surprisingly accurate."⁷ Galileošs effective writing antagonized the Church authorities so much that he was brought to a trial in 1633.⁸ In addition, unlike other scientific books at that time, like most of Galileošs works, the "Dialogue" is in Italian, rather than in Latin. Galileo wanted his works to be read by any person. He believed that using a more common language would have a greater potential of penetrating peoplešs minds.⁹ The use of precise and accurate images, clear and terse descriptions, and a wise choice of language all augmented the influence of the image.

Another factor that affected the image was the printing technology. The massive production of the book and its images increased their availability and accessibility. After the book was published, it was banned; printers were forbidden to publish anything further by Galileo or even to reprint his previous works. But people were able to acquire his book through the black market. According to de Santillana, it is apparent that the book was prevalent and had high accessibility--"Priests, monks, prelates even, vie with each other in buying up copies of the Dialogue on the black marketŠ. the black market price of the book rises from the original half-scudo to four and six scudi (about a hundred dollars in present time ) all over Italy."¹⁰ Outside Italy, the "Dialogue" was translated into Latin and was read by scholars throughout Europe. ¹¹ Thus, the image "Planets Revolving around the Sun" was seen by numberless readers.

The "Dialogue on the Two Chief World Systems" never would have been controversial without the imagery. The three factors that were used by Galileo: the telescope, the writing techniques used by Galileo, and the printing method created the images. Although his writing technique was not explicitly related to the image, by explaining the image, it helped to convey its meaning to readers. Galileo was able to represent his main idea using images, without using complex descriptions. The invention of the telescope enabled Galileo to obtain concrete information; thus it helped the credibility of the image. His precise and clear writing techniques helped readers to understand the image better and faster. The massive production of the image accelerated the spread of his claim to the world much faster. His argument was disputed among scientists for more than 350 years. If he had not used these methods, his influence would not have lasted long, and the image "The Planets Revolving around the Sun" wouldnšt mean anything. If he had not been imprisoned, rather was supported by Church about his observation, his influence would have been more influential. Or, if he had invented a more powerful telescope, more clear writing technique and better-printed method, he would have been burned at a stake for the "vehement suspicion of heresy." No one knows.