Starry Messenger(1610) - Galileo Galilei

Galileo menemukan tiga satelit alami Jupiter -Io, Europa, dan Callisto- pada 7 Januari 1610. Empat malam kemudian, ia menemukan Ganymede.penemuan penting tersebut di publikasikan pada buku ini.

Sidereus Nuncius (usually translated into English as Sidereal Messenger, although Starry Messenger and Sidereal Message are also seen) is a short treatise published in New Latin by Galileo Galilei in March 1610. It was the first scientific treatise based on observations made through atelescope. It contains the results of Galileo's early observations of the Moon, the stars, and the moons of Jupiter.

Galileo improved the construction of a telescope, which he used to observe the night sky and the moon. In his observations of the Moon, Galileo observed that the line separating lunar day from night (the terminator) was smooth where it crossed the darker regions of the moon, but quite irregular where it crossed the brighter areas. From this observation, he deduced that the darker regions are flat, low-lying areas, while the brighter regions are rough and covered with mountains. Based on the distance of sunlit mountaintops from the terminator, he estimated that the lunar mountains were at least 4 miles in height. This contradicted Aristotelean cosmology, which held that since the heavens were more perfect than the earth, the heavenly bodies must be perfectly smooth spheres.

In observing the stars, Galileo reported that he saw at least ten times as many stars through the telescope as with the naked eye, and he published star charts of the belt of Orion and the Pleiades showing some of the newly observed stars. Also, when he observed some of the "nebulous" stars in the Ptolemaic star catalogue, he saw that rather than being cloudy, they were made of many small stars. From this, he deduced that the nebulae, and the Milky Way itself, were collections of stars too small and far away to be resolved into individual stars by the naked eye.

In the last portion of Sidereus Nuncius, Galileo reported his discovery of four objects that appeared to form a straight line of stars near Jupiter. He gave illustrations of the relative positions of Jupiter and its moons as they appeared nightly from late January through early March 1610. From the fact that they changed their relative positions from night to night, but always appeared in the same straight line near Jupiter, he deduced that they were four bodies in orbit around Jupiter.

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Sidereus Nuncius

The Assayer(1623) - Galileo Galilei

The Assayer (Il Saggiatore in Italian) was a book published in Rome by Galileo Galilei in October 1623.

The book was a polemic against the treatise on the comets of 1618 by Orazio Grassi, a Jesuit mathematician at the Collegio Romano. In this matter Grassi, for all his Aristotelianism, was right and Galileo was wrong. Galileo incorrectly treated the comets as a play of light rather than as real objects.

In 1616 Galileo may have been silenced on Copernicanism. In 1623 his supporter and friend, Cardinal Maffeo Barberini, a former patron of the Lynxand uncle of Cardinal Francesco Barberini, became Pope Urban VIII. The election of Barberini seemed to assure Galileo of support at the highest level in the Church. A visit to Rome confirmed this.

The title page of The Assayer shows the crest of the Barberini family, featuring three busy bees. In The Assayer, Galileo weighs the astronomical views of a Jesuit, Orazio Grassi, and finds them wanting. The book was dedicated to the new pope. The title page also shows that Urban VIII employed a member of the Lynx, Cesarini, at a high level in the papal service. This book was edited and published by members of the Lynx.

Again Galileo insisted that physics should be mathematical. According to the title page, he was the philosopher or physicist of the Grand Duke of Tuscany, not merely the mathematician. Physics or natural philosophy spans the gamut from processes of generation and growth (represented by a plant) to the physical structure of the universe, represented by the cosmic cross-section. Mathematics, on the other hand, is symbolized by telescopes, and an astrolabe. This is the book containing Galileo’s famous statement that mathematics is the language of God. Only through mathematics can one achieve lasting truth in physics. Those who neglect mathematics wander endlessly in a dark labyrinth. From the book:

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The Assayer

Dialogue Concerning the Two Chief World Systems(1632) - Galileo Galilei

The Dialogue Concerning the Two Chief World Systems (Dialogo sopra i due massimi sistemi del mondo) was a 1632 Italian language book by Galileo Galilei comparing the Copernican system with the traditional Ptolemaic system. It was translated to Latin as Systema cosmicum in 1635 by Matthias Bernegger.The book, which was dedicated to Galileo's patron, Ferdinando II de' Medici, Grand Duke of Tuscany and delivered to him on February 22, 1632,was a bestseller.

In the Copernican system the Earth and other planets orbit the Sun, while in the Ptolemaic system everything in the Universe circles around the Earth. The Dialogue was published in Florence under a formal license from the Inquisition. In 1633, Galileo was convicted of "grave suspicion ofheresy" based on the book, which was then placed on the Index of Forbidden Books, from which it was not removed until 1835 (after the theories it discussed had been permitted in print in 1822.) In an action that was not announced at the time, the publication of anything else he had written or ever might write was also banned.

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Dialogue Concerning the Two Chief World Systems