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The Stellar Splendours of Galileo

Obaidur Rahman

Photo: courtesy

A legend, even though not in his lifetime, the marvels of Galileo Galilei are sincerely recognised today which many believe have single-handedly given birth to what we refer presently as modern science. February 15, marks the 447th birth anniversary of this great Italian astronomer, mathematician, physicist and philosopher who forever changed the way we used to perceive science, the Earth and the Universe.

Born in Pisa, Italy in 1564, Galileo was the first of six children of a famous music theorist and wool trader named Vincenzo Galilei who always cherished the idea that his eldest would pursue a career in medicine. A devout catholic, Galileo, however, seriously considered priesthood up until the age of 17 when he was withdrawn from the monastery and finally enrolled in the University of Pisa (UP) in 1581 to study medicine at his father's urging. But very soon he realised his passion for mathematics and convinced his father to allow him to study science and math. And thus began a distinguished career in academics for Galileo. Even though he left the UP without a degree in 1585, however he was appointed as a lecturer of mathematics at the same university in 1589 and later joined the University of Padua in 1592 where he continued to serve as a chair of mathematics until 1610. Since then and especially the later years up until his death at the age of 77, Galileo was riddled with controversy for his open support of Copernican theory which stated that Earth revolved around the Sun.

Often referred as the “Father of modern observational astronomy”, in 1608 Galileo heard that telescope has been invented in the Netherlands and in the following year without actually seeing the apparatus he ingeniously perfected it based on rough ideas to such an extent that his refined version of the device revolutionised they way mankind studied the heavens. In December, 1609, Galileo looked at the moon through his telescope and believed to be the very first person to report the lunar mountains and craters which firmly established for the very first time that the moon was in fact “rough and uneven, and just like the surface of the Earth itself”, very contrary to the traditionally accepted Aristotelian concept which stated that moon is a perfect sphere. On January 7th, 1610, Galileo aimed his telescope towards the planet Jupiter and noticed three small “stars” near the planet, one of which was off to the west and the other two were to the east, all lying in a straight line. The observation from the subsequent nights revealed that all three “stars” were now positioned on the west of Jupiter however still in a straight line. On January 10th, he noticed that one of them had disappeared and Galileo suspected that the missing “star” was perhaps located behind Jupiter. These “stars” were in fact three of the Jupiter's four largest satellites, i.e. moons, Io, Europa and Callisto and on 13th January Galileo discovered the fourth one, Ganymede. Today we know these four satellites of Jupiter as the Galilean moons. Vigilant observations of these supposed stars lead Galileo to this revolutionary conclusion that these were in fact small satellites orbiting around the planet Jupiter. And this finding was very contradictory to the traditionally held geocentric view of the Aristotelian cosmology which stated that Earth was at the centre of the universe and all heavenly bodies circle the Earth. But the course of the four moons of the Jupiter firmly convinced Galileo that Earth, in fact, was not at the centre of the Universe and he resolutely echoed the Copernican heliocentric view that Earth is just a planet orbiting around the Sun, which is at the centre of the solar system. Galileo's stance on Copernican view further strengthened when he observed the full set of orbital phase of Venus which he found to be similar to that of the moon. Before that it was traditionally believed based on Ptolemy's geocentric model that the orbit of the Venus was specifically placed entirely on the near side of the Sun. But Galileo's telescopic observation of Venus's orbit around the Sun made this Ptolemaic astronomical model invalid and it is believed that this single finding made a significant contribution for the transition of mankind's astronomical approach from geocentric to heliocentric point of view. Furthermore Galileo's observations of the dark patches on the Sun, known today as Sunspots, challenged the then traditionally accepted supposed perfection of the heavens which was hypothesised by the orthodox Aristotelian celestial physics. Besides Galileo's observational findings of the motions of these Sunspots indicated two things, one, the Sun is rotating on an axis and secondly, this indicates on the possibility that the earth is doing so as well. And both of these concepts were absent in Aristotelian and Ptolemaic knowledge of the heavens. Over the course of next few days Galileo went on discovering several astronomical facts that sincerely challenged the Aristotelian and Ptolemaic authority of the nature of the Universe and some of these includes, showing that planets were disks, not points of light, Milky Way, which was thought to be the “great” cloud, is in fact our very own galaxy composed of multitude of stars and the rings around the Saturn.

Galileo Galilei Photo: courtesy

In order to fully comprehend Galileo's conflict with the Church, first it has to be understood that the scientific and philosophical ideas of that time, which was practiced by the theologians, was mostly based on the works of Aristotle and Ptolemy whose teachings were very much associated with the Catholic Church of that time. In 1610, Galileo published his telescopic discoveries in a book titled The Starry Messenger where he argued in favour of Copernican's Sun-centred theory against the traditionally practised Ptolemaic and Aristotelian Earth-centred theories. In 1612, opposition to that Sun-centred theory surfaced and during 1614 a Dominican Friar named Father Tommaso Caccini denounced Galileo's opinions and accused him of heresy. In order to defend himself from such accusations Galileo went to Rome in 1616 and there Cardinal Roberto Bellarmino as per directive of the Inquisition delivered him an order not to “hold or defend” the Sun-centered theory. Galileo managed to stay away from controversy until 1622 when he published The Assayer and the Dialogue Concerning the Two Chief World Systems in 1632, both of which echoed out his views on Sun-centric astronomical systems. In October of the later year he was ordered to appear before the Holy Office in Rome and in 1633, following a Papal trial he was found “vehemently suspect of heresy” for his views and ordered imprisonment, a sentence which was later commuted to house arrest. He spent remainder of his life at his country house in Arcetri, outside of Florence and went completely blind in 1638 while suffering from painful hernia and insomnia until his death in 1642 from fever and heart palpitations.

Before that and in between his years of struggle with the Church, Galileo made significant discoveries in fields of both pure and applied science which continued to influence the contemporary scientific thinking. Newton's first law of motion owes its inspiration to the Galileo's Principle of Inertia and the Italian's scientist's stance on the basic principle of relativity was central to Einstein's special theory of relativity. But perhaps with his life, Galileo decisively established this crucial notion that science needed to be separated from the aspects of traditional philosophy and religion and very much deserved her very own distinct lifeline. In the words of our generation's very own Stephen Hawking, “Galileo probably bears more of the responsibility for the birth of modern science than anybody else”.



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