Photo source: Wikimedia Commons, Justus Sustermans
Galileo Galilei (1564-1642) was an Italian astronomer best known for his revolutionary telescopes and analysis of physics. Philosopher Immanuel Kant said,
"A light was kindled amongst the investigators of nature when Galilei let balls of a definite weight roll down the inclined plane. For they saw that they only understand what is produced according to a predetermined plan or hypothesis... for otherwise planless observations made according to no ideas could never be brought into the form of a law which reason demands and seeks." (Critique of Pure Reason, 1787)Science historian I. Bernard Cohen said,
"Galileo had the experience of beholding the heavens as they actually are for perhaps the first time, and wherever he looked he found evidence to support the Copernican system again the Ptolemaic, or at least weaken the authority of the ancients." (The Birth of a New Physics, 1959)
The rest of this post is some quotes from Galileo.
Astronomy
"Finally, sparing neither labor nor expense, I succeeded in constructing for myself so excellent an instrument that objects seen by means of it appeared nearly 1,000 times larger and over 30 times closer than when regarded with our natural vision." (Quoted in Discoveries and Opinions of Galileo by Stillman Drake)
"Surely it is a great thing to increase the numerous host of fixed stars previously visible to the unaided vision, adding countless more which have never before been seen, exposing these plainly to the eye in numbers 10 times exceeding the old familiar stars." (Quoted in Discoveries and Opinions of Galileo by Stillman Drake)
"They know that as to the arrangement of the parts of the universe, I hold the sun to be situated motionless int he center of the revolution of the celestial orbs while the earth revolves around the sun." (Letter to the Grand Duchess Christina, 1615)
Physics
"It has been observed that missiles and projectiles described a curve path of some sort; however no one has pointed out the fact that this path is a parabola." (Dialogues and Mathematical Demonstrations Concerning Two New Sciences, 1638)
"Some superficial observations have been made, as for instance, that the free motion of a heavy falling object is continuously accelerated; but to just what extent this acceleration occurs has not yet been announced." (Dialogues and Mathematical Demonstrations Concerning Two New Sciences, 1638)
Philosophy of mathematics
"Philosophy is written in this grant book, which stands continually open before our eyes (I say the 'universe') but can not be understood without first learning to comprehend the language and know the characters it is written. It is written in mathematical language and its characters are triangles, circles and other geometric figures, without which it is impossible to humanly understand a word; without these one is wandering in a dark labyrinth." (The Assayer, 1623)
