History doesn't repeat; it rhymes.

Galileo was born in 1564, the same year as Shakespeare. Like Descartres, Voltaire, and Diderot, Galileo received a Jesuit education.

Until Galileo, astrology was linked inseparably from astronomy which was widely believed (by Copernicu and Kepler, among others).

In 1609, Galileo discovered the telescope. This simple tool allowed him to observe things that were contrary to the entrenched belief system of his time and would lead him to a meeting with the Inquisition.

By discovering and observing the moons of Jupiters, he was able to prove that the Earth revolved around the sun and not vice versa.

Much more radically and fundamentally, however, Galileo made the leap from scanning sacred texts for truth to scanning the world around us as it is, not as we wish it to be, measuring, forming a tentative explanatory model, then continuing to test and modify. In other words, he invented the scientific model. He believed that Truth was measurable and objective, that God wasn't tricking us when he gave us senses and the ability to infer governing laws from our observations. "The Book of Nature is written in mathematical characters," he once famously said.

In 1616, the Catholic Church declared Copernican theory, the radical notion of a heliocentric universe, "false and erroneous", losing serious credibility thereafter.

What is not as well known about Galileo is that he reinvented himself in old age. When the Church forbade him from teaching Copernican theory and placed him under house arrest, he obeyed. Although losing his vision and suffering from arthritis, he launched into an exploration of the basic laws of motion. It was Galileo, not Isaac Newton, who articulated the concept of inertia, that a body at rest tends to stay at rest and one in motion tends to stay in motion. Force is necessary only for a change in velocity.

Copernicus, by the way, was not a radical, as he is remembered, but in the employee of the Catholic church when he advanced his heliocentric theory as a hypothesis in 1512. He induced this from the Pythagorean conviction that nature was ultimately comprehensible in simple mathematical terms. The geocentric model didn't explain or predict the movement of planets with any simple models.

Dava Sobel

"Witnesses are examined in doubtful matters which are past and transient, not in those which are actual and present. A judge must seek by means of witness whether Pietro injured Giovanni last night, but not whether Giovanni was injured, since the judge can see that for himself. But even in conclusions which can be known only by reasoning, I say that the testimony of many has little more value than that of few, since the number of people who reason well in complicated matters is much smaller than those who reason badly. If reasoning were like hauling, I should agree that several reasoners would be worth more than one, just as several horses can haul more sacks of grain than one can. But reasoning is like racing and not like hauling, and a single Barbary steed can outrun a 100 dray horses."

- page 93

"The novelty of these things, as well as some consequences which followed from them in contradiction to the physical notions commonly held to academic philosophers, stirred up against me no small number of professors -- as if I placed these things in the sky with my own hands in order to upset nature and overturn the sciences. They seem to forget that the increase in the known truths stimulates the investigation, establishment, and growth of the arts;not their diminution or destruction.

- page 67

"Showing a greater fondness for their own opinions than for truth, they... hurled various charges and published numerous writings filled with vain arguments, and they made the grave mistake of sprinkling these with passages taken from places in the Bible which they failed to understand properly, and which were ill-suited to their purposes."

"Let us grant then that theology is conversant with the loftiest divine contemplation, and occupies the Regal throne among sciences by dignity. But acquiring the highest authority in this way, and she does not extend to the lower and humbler speculations of the subordinate sciences and has no regard for them because they're not concerned with pleasantness, then her decision should not arrogate to themselves the authority to decide on controversies in professions in which they had neither studied nor practiced. Why then, this would be as if an absolute despot, being neither a physician nor an architect, should undertake to administer medicines and direct buildings according to his whims – at grave peril to the poor patients' lives, and the speedy collapse of these edifices.

• page 68

To prohibit the whole science would be but to censure a 100 pages of holy scripture which teach us that the glory and greatness of almighty God are marvelously discerned in all his works and widely read in the open book of heaven. For let no one believe that reading the lofty concepts written in that book leads to nothing further than the mere seeing of splendor of the sun and stars and of their rising and setting, which is as far as the eyes of brutes and of the vulgar can penetrate. Within its pages are couched mysteries so profound and concepts so sublime that the vigils, labors, and studies of hundreds upon hundreds of the most acute minds have still not pierced them, even after continual investigations for thousands of years.

- page 69

The cause of the acceleration of the motion of falling bodies is not a necessary part of the investigation.

• page 337

It appears to me that they who in proof of any assertion rely simply on the weight of authority, without inducing any argument in support of it, act very absurdly. I, on the contrary, wish to be allowed freely to question and freely to answer you without any sort of adulation, as well becomes those who are in search of truth.

• Vincenzio, page 17

"Philosophy is written in this grand book, the universe, which stands continually open to our gaze but the book cannot be understood unless one first learns to comprehend the language and to read the alphabet in which it is composed. It is written language of mathematics, and its characters are triangles, circles, and other geometric figures, without which it is humanly impossible to understand a single word of it; without these, one wonders about in a dark labyrinth."

Page 63: Those scriptures cannot err, its expounders and interpreters are liable to err in many ways... when they would base themselves always on the literal meaning of the words. For in this wise not only many contradictions would be apparent, but even grave heresies and blasphemies, since then it would be necessary to give God hands and feet and eyes, and human and bodily emotions such as anger, regret, hatred, and sometimes forgetfulness of things past, and ignorance of the future. Holy scripture and nature are both emanations from the divine word: the former dictated by the holy spirit, the latter by the observant executrix of God's commands. But I do not think it necessary to believe that the same God who gave us our senses, our speech, our intellect, would have put aside the use of these, to teach us instead such things as with our help we could find out for ourselves, particularly in the case of these sciences of which there is not the smallest mention in the Scriptures; and, above all, in astronomy, of which so little notice is taken that the names of none of the planets are mentioned. Surely if the intention of the sacred scribes had been to teach the people astronomy, they would not have passed over the subject so completely.

• page 65