Galileo Galileo Quotes

Galileo Galileo or Galileo di Vincenzo Bonaulti de Galileo (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist, engineer, philosopher, and mathematician who played a major role in the scientific revolution during the Renaissance. Galileo has been called the “father of observational astronomy”, the “father of modern physics”, the “father of the scientific method”, and the “father of modern science”.

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Galileo Galileo Quotes

Alas! Your dear friend and servant Galileo has been for the last month hopelessly blind; so that this heaven, this earth, this universe, which I by my marvelous discoveries and clear demonstrations had enlarged a hundred thousand times beyond the belief of the wise men of bygone ages, henceforward for me is shrunk into such a small space as is filled by my own bodily sensations. – Galileo Galileo, The private life of Galileo

All truths are easy to understand once they are discovered; the point is to discover them. – Galileo Galileo

All truths are easy to understand once you find them, the point is to discover them. – Galileo Galileo

Among the great men who have philosophized about [the action of the tides], the one who surprised me most is Kepler. He was a person of independent genius, [but he] became interested in the action of the moon on the water, and in other occult phenomena, and similar childishness. – Galileo Galileo

And believe me, if I were again beginning my studies, I should follow the advice of Plato and start with the mathematical sciences, which proceed very cautiously and admit nothing as established until it has been rigorously demonstrated. – Galileo Galileo

And yet it moves. – Galileo Galileo

And yet it moves. About the earth, the comment he is rumored to have made after his recantation before the Inquisition. – Galileo Galileo

And yet Its still moves– Galileo Galileo

And, believe me, if I were again beginning my studies, I should follow the advice of Plato and start with mathematics. – Galileo Galileo

Being beautiful is not in the way you dress nor on the pigments you put in your face. Being beautiful is being simple.All girls are insecure, they may not show it, but they are, every girl believes that they have a ‘defect’ but honestly, you don’t! every girl is beautiful, no matter what she wears, what she looks like, or how her body is. don’t worry about that senseless stuff, beauty comes in all shapes and sizes.Facts which at first seem improbable will, even on scant explanation, drop the cloak which has hidden them and stand forth in naked and simple beauty. – Galileo Galileo

Being infinitely amazed, so do I give thanks to God, Who has been pleased to make me the first observer of marvelous things, unrevealed to bygone ages. – Galileo Galileo

But let us remember that we are dealing with infinities and indivisibles both of which transcend our finite understanding, the former on account of their magnitude, the latter because of their smallness. – Galileo Galileo

But of all other stupendous inventions, what sublimity of mind must have been his who conceived how to communicate his most secret thoughts to any other person, though very far distant, either in time or place? And with no greater difficulty than the various arrangement of two dozen little signs upon paper? Let this be the seal of all the admirable inventions of man. – Galileo Galileo

But some, besides allegiance to their original error, possess I know not what fanciful interest in remaining hostile not so much toward the things in question as toward their discoverer. – Galileo Galileo

But what exceeds all wonders, I have discovered four new planets and observed their proper and particular motions, different among themselves and from the motions of all the other stars; and these new planets move about another very large star [Jupiter] like Venus and Mercury, and perchance the other known planets, move about the Sun. As soon as this tract, which I shall send to all the philosophers and mathematicians as an announcement, is finished, I shall send a copy to the Most Serene Grand Duke, together with an excellent spyglass, so that he can verify all these truths. – Galileo Galileo

But, because my private lectures and domestic pupils are a great hinderance and intteruption of my studies, I wish to live entirely exempt from the former, and in great measure from the latter. … in short, I should wish to gain my bread from my writings. – Galileo Galileo

Detractors of corruptibility deserve being turned into statues. – Galileo Galileo

Doubt is the father of invention. – Galileo Galileo

E pur si muove
(Albeit It does move.)
[What Galileo purportedly muttered after torturers forced him to recant his theory that the earth orbits the sun.] – Galileo Galileo

E pur si muove. “Albeit It does move”. (That’s what Galileo purportedly muttered after torturers forced him to recant his theory that the earth orbits the sun.) – Galileo Galileo

E pur si muove. (Albeit It does move.) [What Galileo purportedly muttered after torturers forced him to recant his theory that the earth orbits the sun.] – Galileo Galileo

E pur si muove. (It still moves.) (What Galileo purportedly muttered after torturers forced him to recant his theory that the earth orbits the sun.)– Galileo Galileo

E pur si muove.
(And yet it moves.)
(What Galileo purportedly muttered after torturers forced him to recant his theory that the earth orbits the sun.) – Galileo Galileo

Eppur si muove. – Galileo Galileo

For in the sciences the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man. Besides, the modern observations deprive all former writers of any authority, since if they had seen what we see, they would have judged as we judge. – Galileo Galileo

For my part I consider the earth very noble and admirable precisely because of the diverse alterations, changes, generations, etc. that occur in it incessantly. – Galileo Galileo

Given (…) that two truths can never contradict each other, the task of wise interpreters is to strive to find the true meanings of scriptural passages agreeing with those physical conclusions of which we are already certain and sure from clear sensory experience or from necessary demonstrations. – Galileo Galileo

I am certainly interested in a tribunal in which, for having used my reason, I was deemed little less than a heretic. Who knows but men will reduce me from the profession of a philosopher to that of historian of the Inquisition! – Galileo Galileo

I cannot but be astonished that Sarsi should persist in trying to prove by means of witnesses something that I may see for myself at any time by means of experiment. Witnesses are examined in doutbful matters which are past and transient, not in those which are actual and present. A judge must seek by means of witnesses to determine whether Peter injured John last night, but not whether John was injured, since the judge can see that for himself. – Galileo Galileo

I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forego their use. – Galileo Galileo

I esteem myself happy to have as great an ally as you in my search for truth. I will read your work … all the more willingly because I have for many years been a partisan of the Copernican view because it reveals to me the causes of many natural phenomena that are entirely incomprehensible in the light of the generally accepted hypothesis. To refute the latter I have collected many proofs, but I do not publish them, because I am deterred by the fate of our teacher Copernicus who, although he had won immortal fame with a few, was ridiculed and condemned by countless people (for very great is the number of the stupid). – Galileo Galileo

I give infinite thanks to God, who has been pleased to make me the first observer of marvelous things. – Galileo Galileo

I have been in my bed for five weeks, oppressed with weakness and other infirmities from which my age, seventy four years, permits me not to hope release. Added to this ( proh dolor! ) the sight of my right eye – that eye whose labors (dare I say it) have had such glorious results – is for ever lost. That of the left, which was and is imperfect, is rendered null by continual weeping. – Galileo Galileo, July 4, 1637, The private life of Galileo

I have been judged vehemently suspect of heresy, that is, of having held and believed that the sun in the centre of the universe and immoveable, and that the earth is not at the center of same, and that it does move. Wishing however, to remove from the minds of your Eminences and all faithful Christians this vehement suspicion reasonably conceived against me, I abjure with a sincere heart and unfeigned faith, I curse and detest the said errors and heresies, and generally all and every error, heresy, and sect contrary to the Holy Catholic Church. – Galileo Galileo, (Quoted in Shea and Artigas 194)

I mentally conceive of some movable projected on a horizontal plane all impediments being put aside. Now it is evident … that the equable motion on this plane would be perpetual if the plane were of infinite extent; but if we assume it to be ended, – Galileo Galileo

I never met a man so unknowledgeable, I could not learn something from him. – Galileo Galileo

I notice that young men go to the universities in order to become doctors or philosophers or anything, so long as it is a title, and that many go in for those professions who are utterly unfit for them, while others who would be very competent are prevented by business or their daily cares, which keep them away from letters. – Galileo Galileo

I see that you have hitherto been one of that herd who, in order to learn how matters such as this take place, and in order to acquire a knowledge of natural effects, do not exhaust themselves in waking and studying, and mortify themselves with experiments and observations, but retire into their studies and glance through an index and a table of contents to see whether Aristotle has said any thing about them; and, being assured of the true sense of his text, consider that nothing else can be known. – Galileo Galileo

I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury about the Sun; which at length was established as clear as daylight by numerous other observations. Referring to his pioneering telescope observations. – Galileo Galileo

I would beg the wise and learned fathers (of the church) to consider with all diligence the difference which exists between matters of mere opinion and matters of demonstration. … [I]t is not in the power of professors of the demonstrative sciences to alter their opinions at will, so as to be now of one way of thinking and now of another. … [D]emonstrated conclusions about things in nature of the heavens, do not admit of being altered with the same ease as opinions to what is permissible or not, under a contract, mortgage, or bill of exchange. – Galileo Galileo

I would beg the wise and learned fathers [of the church] to consider with all diligence the difference which exists between matters of mere opinion and matters of demonstration. – Galileo Galileo

I, Galileo, son of the late Vicenzo Galileo, swear that I never said that the prime numbers are useless. What I said was that you cannot count lunar craters by counting 2, 3, 5, 7. – Galileo Galileo

I’ve loved the stars too fondly to be fearful of the night. – Galileo Galileo

If experiments are performed thousands of times at all seasons and in every place without once producing the effects mentioned by your philosophers, poets, and historians, this will mean nothing and we must believe their words rather than our own eyes? – Galileo Galileo

If I were again beginning my studies, I would follow the advice of Plato and start with mathematics. – Galileo Galileo

If the Earth were not subject to any change I would consider the Earth a big but useless body in universe, paralyzed…superfluous and unnatural.Those who so exalt incorruptibility, unchangeability and the like, are, I think, reduced to saying such things both because of inordinate desire they have to live for a long time and because of the terror they have of death…they do not realize that if men were immortal, they would have never come into the world. – Galileo Galileo

If there were as great a scarcity of soil as of jewels or precious metals, there would not be a prince who would not spend a bushel of diamonds and rubies and a cartload of gold just to have enough earth to plant a jasmine in a little pot, or to sow an orange seed and watch it sprout, grow, and produce its handsome leaves, its fragrant flowers, and fine fruit. – Galileo Galileo

If you could see the earth illuminated when you were in a place as dark as night, it would look to you more splendid than the moon. – Galileo Galileo

In my studies of astronomy and philosophy I hold this opinion about the universe, that the Sun remains fixed in the centre of the circle of heavenly bodies, without changing its place; and the Earth, turning upon itself, moves round the Sun. – Galileo Galileo

In regard to the philosophers, if they be true philosophers, i.e., lovers of truth, they should not be irritated that the earth moves. Rather, if they realize that they have held a false belief, they should thank those have shown them the truth; and if their opinion stands firm that the earth doesn’t move, they will have reason to boast than be angered. – Galileo Galileo

In the future, there will be opened a gateway and a road to a large and excellent science into which minds more piercing than mine shall penetrate to recesses still deeper. – Galileo Galileo

In the long run my observations have convinced me that some men, reasoning preposterously, first establish some conclusion in their minds which, either because of its being their own or because of their having received it from some person who has their entire confidence, impresses them so deeply that one finds it impossible ever to get it out of their heads. – Galileo Galileo

In the sciences, the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man. – Galileo Galileo

In time you may discover everything that can be discovered, and still your progress will only be progress away from humanity. The distance between you and them can one day become so great that your joyous cry over some new gain could be answered by an universal shriek of horror. – Galileo Galileo

Infinities and indivisibles transcend our finite understanding, the former on account of their magnitude, the latter because of their smallness; Imagine what they are when combined. – Galileo Galileo

It has always seemed to me extreme presumptuousness on the part of those who want to make human ability the measure of what nature can and knows how to do, since, when one comes down to it, there is not one effect in nature, no matter how small, that even the most speculative minds can fully understand. – Galileo Galileo

It is a beautiful and delightful sight to behold the body of the Moon. – Galileo Galileo

It is necessary for the Bible, in order to be accommodated to the understanding of every man, to speak many things which appear to differ from the absolute truth so far as the bare meaning of the words is concerned. – Galileo Galileo

It reveals to me the causes of many natural phenomena that are entirely incomprehensible in the light of the generally accepted hypotheses. To refute the latter I collected many proofs, but I do not publish them … I would dare to publish my speculations if there were people men like you. – Galileo Galileo

It was granted to me alone to discover all the new phenomena in the sky and nothing to anybody else. This is the truth which neither envy nor malice can supress. – Galileo Galileo

I’ve loved the stars too fondly to be fearful of the night – Galileo Galileo

Knowing thyself, that is the greatest wisdom. – Galileo Galileo

Long experience has taught me this about the status of mankind with regard to matters requiring thought: the less people know and understand about them, the more positively they attempt to argue concerning them, while on the other hand to know and understand a multitude of things renders men cautious in passing judgement upon anything new. – Galileo Galileo

Mathematics is the key and door to the sciences. – Galileo Galileo

Mathematics is the language in which God has written the universe – Galileo Galileo

Measure what can be measured, and make measurable what cannot be measured. – Galileo Galileo

My dear Kepler, what would you say of the learned here, who, replete with the pertinacity of the asp, have steadfastly refused to cast a glance through the telescope? What shall we make of this? Shall we laugh, or shall we cry? – Galileo Galileo

Names and attributes must be accommodated to the essence of things, and not the essence to the names, since things come first and names afterwards. – Galileo Galileo

Nature . . . is inexorable and immutable; she never transgresses the laws imposed upon her, nor cares a whit whether her abstruse reasons and methods of operations are understandable to men. – Galileo Galileo

Nature is relentless and unchangeable, and it is indifferent as to whether its hidden reasons and actions are understandable to man or not.Science

Nature is written in mathematical language. – Galileo Galileo

Nature…does not act by means of many things when it can do so by means of a few. – Galileo Galileo

Nature’s great book is written in mathematics. – Galileo Galileo

Nature…does not act by means of many things when it can do so by means of a few. – Galileo Galileo

Nature’s great book is written in mathematics. – Galileo Galileo

Nonetheless, it moves. – Galileo Galileo

Nor need you doubt that Pythagoras, a long time before he found the demonstration for the Hecatomb, had been certain that the square of the side subtending the right angle in a rectangular triangle was equal to the square of the other two sides; the certainty of the conclusion helped not a little in the search for a demonstration. But whatever was the method of Aristotle, and whether his arguing a priori preceded sense a posteriori, or the contrary, it is sufficient that the same Aristotle (as has often been said) put sensible experiences before all discourses. As to the arguments a priori, their force has already been examined. – Galileo Galileo, Dialogue on the Great World Systems (1632)

Nothing can be taught to a man, only it’s possibly to help him to discover it inside. – Galileo Galileo

Nothing occurs contrary to nature except the impossible, and that never occurs. – Galileo Galileo

Nothing physical which sense-experience sets before our eyes, or which necessary demonstrations prove to us, ought to be called into question (much less condemned) upon the testimony of biblical passages. – Galileo Galileo

One can understand nature only when one has learned the language and the signs in which it speaks to us; but this language is mathematics and these signs are mathematical figures. – Galileo Galileo

Science proceeds more by what it has learned to ignore than what it takes into account. – Galileo Galileo

See now the power of truth. – Galileo Galileo

See now the power of truth; the same experiment which at first glance seemed to show one thing, when more carefully examined, assures us of the contrary. – Galileo Galileo

Showing a greater fondness for their own opinions than for truth, they sought to deny and disprove the new things which, if they had cared to look for themselves, their own senses would have demonstrated to them. – Galileo Galileo

So far as I know, no one has yet pointed out that the distance travelled in equal intervals of time, by a body falling from rest, stand to one another in the same ratio as the odd number beginning with 1′. – Galileo Galileo

Some, merely to contradict what I had said, did not scruple to cast doubt upon things they had seen with their own eyes again and again. – Galileo Galileo

Spots are on the surface of the solar body where they are produced and also dissolved, some in shorter and others in longer periods. They are carried around the Sun; an important occurrence in itself. – Galileo Galileo

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 ten times exceeding the old and familiar stars. – Galileo Galileo

Take note, theologians, that in your desire to make matters of faith out of propositions relating to the fixity of sun and earth you run the risk of eventually having to condemn as heretics those who would declare the earth to stand still and the sun to change position—eventually, I say, at such a time as it might be physically or logically proved that the earth moves and the sun stands still. – Galileo Galileo

That sculpture is more admirable than painting for the reason that it contains relief and painting does not is completely false. … Rather, how much more admirable the painting must be considered, if having no relief at all, it appears to have as much as sculpture! – Galileo Galileo Letter to Ludovico Cigoli.

The book of nature is written in the language of mathematics. – Galileo Galileo

The deeper I go in considering the vanities of popular reasoning, the lighter and more foolish I find them. What greater stupidity can be imagined than that of calling jewels, silver, and gold precious, and earth and soil base? – Galileo Galileo

The difficulties in the study of the infinite arise because we attempt, with our finite minds, to discuss the infinite, assigning to it those properties which we give to the finite and limited; but this… is wrong, for we cannot speak of infinite quantities as being the one greater or less than or equal to another. – Galileo Galileo

The Divine intellect indeed knows infinitely more propositions [than we can ever know]. But with regard to those few which the human intellect does understand, I believe that its knowledge equals the Divine in objective certainty. – Galileo Galileo

The doctrine that the earth is neither the center of the universe nor immovable, but moves even with a daily rotation, is absurd, and both philosophically and theologically false, and at the least an error of faith. – Galileo Galileo

The earth, in fair and grateful exchange, pays back to the moon an illumination similar to that which it receives from her throughout nearly all the darkest gloom of the night. – Galileo Galileo

The fear of infinity is a form of myopia that destroys the possibility of seeing the actual infinite, even though it in its highest form has created and sustains us. – Galileo Galileo

The Grand Duke [of Tuscany] …after observing the Medicaean plants several times with me … has now invited me to attach myself to him with the annual salary of one thousand florins, and with the title of Philosopher and Principal Mathematicial to His Highness; without the duties of office to perform, but with the most complete leisure; so that I can complete my Treatises… – Galileo Galileo

The great book of nature can be read only by those who know the language in which it was written. And that language is mathematics. – Galileo Galileo

The great book of nature is written in mathematical symbols. – Galileo Galileo

The greatest wisdom is to get to know oneself. – Galileo Galileo

The greatness and the glory of God shine forth marvelously in all His works, and is to be read above all in the open book of the heavens. – Galileo Galileo

The hypothesis is pretty; its only fault is that it is neither demonstrated nor demonstrable. Who does not see that this is purely arbitrary fiction that puts nothingness as existing and proposes nothing more than simple noncontradiciton? – Galileo Galileo

The increase of known truths stimulates the investigation, establishment, and growth of the arts. – Galileo Galileo

The laws of Nature are written in the language of mathematics…the symbols are triangles, circles and other geometrical figures, without whose help it is impossible to comprehend a single word. – Galileo Galileo

The nature of the human mind is such that unless it is stimulated by images of things acting upon it from without, all remembrance of them passes easily away. – Galileo Galileo

The number of fixed stars which observers have been able to see without artificial powers of sight up to this day can be counted. It is therefore decidedly a great feat to add to their number, and to set distinctly before the eyes other stars in myriads, which have never been seen before, and which surpass the old, previously known stars in number more than ten times. – Galileo Galileo

The number of people that can reason well is much smaller than those that can reason badly. If reasoning were like hauling rocks, then several reasoners might be better than one. But reasoning isn’t like hauling rocks, it’s like, it’s like racing, where a single, galloping Barbary steed easily outruns a hundred wagon-pulling horses. – Galileo Galileo

The number of the fixed stars which observers have been able to see without artificial powers of sight up to this day can be counted. It is therefore decidedly a great feat to add to their number, and to set distinctly before the eyes other stars in myriads, which have never been seen before, and which surpass the old, previously known stars in number more than ten times. – Galileo Galileo

The prohibition of science would be contrary to the Bible, which in hundreds of places teaches us how the greatness and the glory of God shine forth marvelously in all His works, and is to be read above all in the open book of the heavens. – Galileo Galileo

The surface of the Moon is not smooth, uniform, and precisely spherical as a great number of philosophers believe it to be, but is uneven, rough, and full of cavities and prominences, being not unlike the face of the Earth, relieved by chains of mountains and deep valleys. – Galileo Galileo

The theologians also should not be irritated. For if they find that this opinion is false, then they would be free to condemn it; and if they discover that it is true, they ought to thank those who have opened the way to finding the true sense of the Scriptures and who have prevented them from falling into the grave scandal of condemning a true proposition. – Galileo Galileo

The universe cannot be read until we have learnt the language and become familiar with the characters in which it is written. It is written in mathematical language, and the letters are triangles, circles and other geometrical figures, without which means it is humanly impossible to comprehend a single word. – Galileo Galileo

The Universe is a grand book which cannot be read until one first learns to comprehend the language and become familiar with the characters in which it is composed. It is written in the language of mathematics. – Galileo Galileo

The vain presumption of understanding everything can have no other basis than never having understood anything. For anyone who had ever experienced just once the perfect understanding of one single thing, and had truly tasted how knowledge is accomplished, would recognize that of the infinity of other truths he understands nothing. – Galileo Galileo

Their vain presumption of knowing all can take beginning solely from their never having known anything; for if one has but once experienced the perfect knowledge of one thing, and truly tasted what it is to know, he shall perceive that of infinite other conclusions he understands not so much as one. – Galileo Galileo

There is not a single effect in Nature, not even the least that exists, such that the most ingenious theorists can ever arrive at a complete understanding of it. This vain presumption of understanding everything can have no other basis than never understanding anything. For anyone who had experienced just once the perfect understanding of one single thing, and had truly tasted how knowledge is attained, would recognise that of the infinity of other truths he understands nothing. – Galileo Galileo

They know that it is human nature to take up causes whereby a man may oppress his neighbor, no matter how unjustly… Hence they have had no trouble in finding men who would preach the damnability and heresy of the new doctrine from the very pulpit.. – Galileo Galileo

They seemed to forget that the increase of known truths stimulates the investigation, establishment and growth of the arts; not their dimination or destruction. – Galileo Galileo

They who depend upon manifest observations will philosophize better than those who persist in opinions repugnant to the senses. – Galileo Galileo

To apply oneself to great inventions, starting from the smallest beginnings, is no task for ordinary minds; to divine that wonderful arts lie hid behind trivial and childish things is a conception for superhuman talents. – Galileo Galileo

To be humane, we must ever be ready to pronounce that wise, ingenious and modest statement ‘I do not know’. – Galileo Galileo

To command their professors of astronomy to refute their own observations is to command them not to see what they do see and not to understand what they do understand. – Galileo Galileo

To excite in us tastes, odors, and sounds I believe that nothing is required in external bodies except shapes, numbers, and slow or rapid movements. … if ears, tongues, and noses were removed, shapes and numbers and motions would remain, but not odors or tastes or sounds. – Galileo Galileo

To our natural and human reason, I say that these terms ‘large,’ ‘small,’ ‘immense,’ ‘minute,’ etc. are not absolute but relative; the same thing in comparison with various others may be called at one time ‘immense’ and at another ‘imperceptible. – Galileo Galileo

To understand the Universe, you must understand the language in which it’s written, the language of Mathematics. – Galileo Galileo

Two truths cannot contradict one another. – Galileo Galileo

Vision, I say, is related to light itself. But of this sensation and the things pertaining to it, I pretend to understand but little; and since even a long time would not suffice to explain that trifle, or even to hint at an explanation, I pass over this in silence. – Galileo Galileo

Want more insightful quotes by famous people? – Galileo Galileo

We must say that there are as many squares as there are numbers. – Galileo Galileo

We see only the simple motion of descent, since that other circular one common to the Earth, the tower, and ourselves remains imperceptible. There remains perceptible to us only that of the stone, which is not shared by us; and, because of this, sense shows it as by a straight line, always parallel to the tower, which is built upright and perpendicular upon the terrestrial surface. – Galileo Galileo

Well, since paradoxes are at hand, let us see how it might be demonstrated that in a finite continuous extension it is not impossible for infinitely many voids to be found. – Galileo Galileo

What has philosophy got to do with measuring anything? – Galileo Galileo

When the moon is ninety degrees away from the sun it sees but half the earth illuminated (the western half). For the other (the eastern half) is enveloped in night. Hence the moon itself is illuminated less brightly from the earth, and as a result its secondary light appears fainter to us. – Galileo Galileo

Who indeed will set bounds to human ingenuity? Who will assert that everything in the universe capable of being perceived is already discovered and known? – Galileo Galileo

Who would dare assert that we know all there is to be known? – Galileo Galileo

Who would set a limit to the mind of man? Who would dare assert that we know all there is to be known? – Galileo Galileo

Wine is light held together by moisture. – Galileo Galileo

Wine is sunlight, held together by water. – Galileo Galileo

With regard to matters requiring thought: the less people know and understand about them, the more positively they attempt to argue concerning them. – Galileo Galileo

You can’t teach anybody anything, only make them realize the answers are already inside them. – Galileo Galileo

You cannot teach a person something he does not already know, you can only bring what he does know to his awareness. – Galileo Galileo

You can’t teach anybody anything, only make them realize the answers are already inside them. – Galileo Galileo

You may force me to say what you wish; you may revile me for saying what I do. But it moves. – Galileo Galileo

Не се чувствам длъжен да вярвам, че Господ, който ни е надарил с чувства и разум, е възнамерявал да забравим за тях. – Galileo Galileo

On Astronomy

  • Galileo Galileo remained a profoundly religious man through his lifetime, he found no conflict with his spiritual beliefs and his studies of science. However, the church did find conflict and Galileo had to answer to charges of heresy in church court more than once. At the age of sixty-eight, Galileo Galileo was tried for heresy for supporting the science that the earth rotated around the sun, the Copernican model of the solar system. The Catholic church supported the geocentric model of the solar system, where the sun and the rest of the planets all rotate around a central non-moving earth. Fearing torture at the hands of the church inquisitors, Galileo made a public confession that he had been wrong to have said that the Earth moves around the Sun.

I wish, my dear Kepler, that we could have a good laugh together at the extraordinary stupidity of the mob. What do you think of the foremost philosophers of this University? In spite of my oft-repeated efforts and invitations, they have refused, with the obstinacy of a glutted adder, to look at the planets or the Moon or my glass [telescope]. – Galileo Galileo

My dear Kepler, I wish that we might laugh at the stupidity of the human herd. What do you have to say about the principal philosophers of this academy who are filled with the stubbornness of an asp and do not want to look at either the planets, the moon or the telescope, even though I have freely and deliberately offered them the opportunity a thousand times? Truly, just as the asp stops its ears, so do these philosophers shut their eyes to the light of truth. – Galileo Galileo

The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do. – Galileo Galileo

Exploration is in our nature. We began as wanderers, and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars.Exploration is in our nature. We began as wanderers, and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars. – Galileo Galileo

The Milky Way is nothing else but a mass of innumerable stars planted together in clusters. – Galileo Galileo

To command the professors of astronomy to confute their own observations is to enjoin an impossibility, for it is to command them not to see what they do see, and not to understand what they do understand, and to find what they do not discover. – Galileo Galileo

The sun with all the planets around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the Universe to do. – Galileo Galileo

Oh, my dear Kepler, how I wish that we could have one hearty laugh together. Here, at Padua, is the principal professor of philosophy, whom I have repeatedly and urgently requested to look at the moon and planets through my glass, [telescope] which he pertinaciously refuses to do. Why are you not here? what shouts of laughter we should have at this glorious folly! and to hear the professor of philosophy at Pisa laboring before the grand duke with logical arguments, as if with magical incantations, to charm the new planets out of the sky. – Galileo Galileo

Galileo Galileo Quotes

On God and Religion

  • With the battle between science and church that occurred during Galileo’s lifetime in mind, consider the following quotes from Galileo Galileo about God and the scriptures

I do not feel obliged to believe that the same God who has endowed us with senses, reason, and intellect has intended us to forgo their use and by some other means to give us knowledge which we can attain by them. – Galileo Galileo

I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.

I do not know what to say in a case so surprising, so unlooked for and so novel. – Galileo Galileo

I do not think it is necessary to believe that the same God who has given us our senses, reason, and intelligence wished us to abandon their use, giving us by some other means the information that we could gain through them. – Galileo Galileo

I entertain no doubts as to the truth of the transfinites, which I have recognized with God’s help. – Galileo Galileo

God is known by nature in his works, and by doctrine in his revealed word. – Galileo Galileo

By denying scientific principles, one may maintain any paradox. – Galileo Galileo

Mathematics is the language with which God has written the universe. – Galileo Galileo

It is surely harmful to souls to make it a heresy to believe what is proved. – Galileo Galileo

And who can doubt that it will lead to the worst disorders when minds created free by God are compelled to submit slavishly to an outside will? When we are told to deny our senses and subject them to the whim of others? When people devoid of whatsoever competence are made judges over experts and are granted authority to treat them as they please? These are the novelties which are apt to bring about the ruin of commonwealths and the subversion of the state. – Galileo Galileo

I would say here something that was heard from an ecclesiastic of the most eminent degree: The intention of the Holy Spirit is to teach us how one goes to heaven, not how the heavens go. – Galileo Galileo

After making his false confession, Galileo quietly mumbled the truth: And yet, it moves. – Galileo Galileo

Having been admonished by this Holy Office [the Inquisition] entirely to abandon the false opinion that the Sun was the center of the universe and immovable, and that the Earth was not the center of the same and that it moved… I abjure with a sincere heart and unfeigned faith, I curse and detest the said errors and heresies, and generally all and every error and sect contrary to the Holy Catholic Church. – Galileo Galileo

Holy Scripture could never lie or err…its decrees are of absolute and inviolable truth. – Galileo Galileo

Holy Writ was intended to teach men how to go to Heaven not how the heavens go. – Galileo Galileoo

I am inclined to think that the authority of Holy Scripture is intended to convince men of those truths which are necessary for their salvation, which, being far above man’s understanding, can not be made credible by any learning, or any other means than revelation by the Holy Spirit. – Galileo Galileo

I believe that the intention of Holy Writ was to persuade men of the truths necessary to salvation; such as neither science nor other means could render credible, but only the voice of the Holy Spirit. – Galileo Galileo

Copernicus did not ignore the Bible, but he knew very well that if his doctrine were proved, then it could not contradict the Scriptures when they were rightly understood. – Galileo Galileo

I think that in the discussion of natural problems we ought to begin not with the Scriptures, but with experiments, and demonstrations. – Galileo Galileo

Scripture is a book about going to Heaven. It’s not a book about how the heavens go. – Galileo Galileo

What ever the course of our lives, we should receive them as the highest gift from the hand of God, in which equally reposed the power to do nothing whatever for us. Indeed, we should accept misfortune not only in thanks but in infinite gratitude to Providence, which by such means detaches us from an excessive love for Earthly things and elevates our minds to the celestial and divine. – Galileo Galileo

Surely, God could have caused birds to fly with their bones made of solid gold, with their veins full of quicksilver, with their flesh heavier than lead, and with their wings exceedingly small. He did not, and that ought to show something. It is only in order to shield your ignorance that you put the Lord at every turn to the refuge of a miracle. – Galileo Galileo

It seems to me that it was well said by Madama Serenissima, and insisted on by your reverence, that the Holy Scripture cannot err, and that the decrees therein contained are absolutely true and inviolable. But I should have in your place added that, though Scripture cannot err, its expounders and interpreters are liable to err in many ways; and one error in particular would be most grave and most frequent, if we always stopped short at the literal signification of the words. – Galileo Galileo

It is very pious to say and prudent to affirm that the holy Bible can never speak untruth — whenever its true meaning is understood. But I believe nobody will deny that it is often very abstruse, and may say things which are quite different from what. – Galileo Galileo

It vexes me when they would constrain science by the authority of the Scriptures, and yet do not consider themselves bound to answer reason and experiment. – Galileo Galileo

The Bible shows the way to go to heaven, not the way the heavens go. – Galileo Galileo

The intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes. – Galileo Galileo

The laws of nature are written by the hand of God in the language of mathematics. – Galileo Galileo

To me, a great ineptitude exists on the part of those who would have it that God made the universe more in proportion to the small capacity of their reason than to His immense, His infinite, power. – Galileo Galileo

Religion and science were both intertwined and at odds during Galileo’s lifetime, the late 16th century and early 17th century. For example, a serious discussion among academics at that time, was about the size and shape of hell as depicted in the poem Dante’s Inferno. Galileo gave a well-received lecture on the topic, including his scientific opinion about how tall Lucifer was. As a result, Galileo was given a position at the University of Pisa based on favorable reviews of his talk. – Galileo Galileo

To understand the quotes of Galileo Galileo concerning God and religion we have to understand the times Galileo lived in, an age of transition between religious belief and scientific reason. Galileo received his higher education at a Jesuit monastery beginning at the age of eleven, religious orders provided one of the few sources of advanced education at that time. The Jesuits priests made a great impression on the young Galileo, so much so that at the age of seventeen he announced to his father that he wanted to become a Jesuit. His father immediately removed Galileo from the monastery, not wanting his son to pursue the unprofitable career of becoming a monk. – Galileo Galileo

On Philosophy

Passion is the genesis of genius. – Galileo Galileo

Who am I? – Galileo Galileo

What has philosophy got to do with measuring anything? It’s the mathematicians you have to trust, and they measure the skies like we measure a field. – Galileo Galileo

Philosophy [nature] is written in that great book which ever is before our eyes — I mean the universe — but we cannot understand it if we do not first learn the language and grasp the symbols in which it is written. The book is written in mathematical language, and the symbols are triangles, circles and other geometrical figures, without whose help it is impossible to comprehend a single word of it; without which one wanders in vain through a dark labyrinth. – Galileo Galileo

Philosophy is written in that great book which ever lies before our eyes – I mean the universe – but we cannot understand it if we do not first learn the language and grasp the symbols, in which it is written. – Galileo Galileo

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 read the letters in which it is composed. – Galileo Galileo

Philosophy itself cannot but benefit from our disputes, for if our conceptions prove true, new achievements will be made; if false, their refutation will further confirm the original doctrines. – Galileo Galileo

He who looks the higher is the more highly distinguished, and turning over the great book of nature (which is the proper object of philosophy) is the way to elevate one’s gaze. – Galileo Galileo

I have never met a man so ignorant that I couldn’t learn something from him. – Galileo Galileo

I truly believe the book of philosophy to be that which stands perpetually open before our eyes, though since it is written in characters different from those of our alphabet it cannot be read by everyone. – Galileo Galileo

There are those who reason well, but they are greatly outnumbered by those who reason badly. – Galileo Galileo

We cannot teach people anything; we can only help them discover it within themselves. – Galileo Galileo

Galileo Galileo Quotes

On Science

  • Where the senses fail us, reason must step in. – Galileo Galileo

  • In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. – Galileo Galileo

  • Facts which at first seem improbable will, even on scant explanation, drop the cloak which has hidden them and stand forth in naked and simple beauty. – Galileo Galileo

  • Galileo’s scientific achievements include inventing: an improved telescope, a horse-powered pump to raise water, and a water thermometer. – Galileo Galileo

  • … I should think that anyone who considered it more reasonable for the whole universe to move in order to let the Earth remain fixed would be more irrational than one who should climb to the top of your cupola just to get a view of the city and its environs, and then demand that the whole countryside should revolve around him so that he would not have to take the trouble to turn his head. – Galileo Galileo

  • …what would be observed (if not with one’s actual eyes at least with those of the mind) if an eagle, carried by the force of the wind, were to drop a rock from its talons? – Galileo Galileo

  • Eppur si muove.
    And yet it does move.
    Referring to the Earth. Apocryphal saying (of doubtful authenticity). By legend, Galileo whispered this to himself as he rose from kneeling after making his abjuration of heliocentricity. – Galileo Galileo
    (No clear evidence exists that Galileo actually said these words, which may have been invented as stories about Galileo were circulated after his death.)

  • Salviati: …Now you see how easy it is to understand.
    Sagredo: So are all truths, once they are discovered; the point is in being able to discover them.
    [Commonly seen merged in a paraphrase as: All truths are easy to understand once they are discovered; the point is to discover them.] – Galileo Galileo

  • About ten months ago [1609] a report reached my ears that a certain Fleming [Hans Lippershey] had constructed a spyglass, by means of which visible objects, though very distant from the eye of the observer, were distinctly seen as if nearby… Of this truly remarkable effect several experiences were related, to which some persons gave credence while others denied them. A few days later the report was confirmed to me in a letter from a noble Frenchman at Paris, Jacques Badovere, which caused me to apply myself wholeheartedly to enquire into the means by which I might arrive at the invention of a similar instrument. This I did shortly afterwards, my basis being the theory of refraction. First I prepared a tube of lead, at the ends of which I fitted two glass lenses, both plane on one side while on the other side one was spherically convex and the other concave. – Galileo Galileo

  • Alas, your dear friend and servant is totally blind. Henceforth this heaven, this universe, which by wonderful observations I had enlarged by a hundred and a thousand times beyond the conception of former ages, is shrunk for me into the narrow space which I myself fill in it. So it pleases God; it shall therefore please me also. – Galileo Galileo,In Letter, as quoted in Sir Oliver Lodge, Pioneers of Science (1905), 133.

  • As to what Simplicius said last, that to contend whether the parts of the Sun, Moon, or other celestial body, separated from their whole, should naturally return to it, is a vanity, for that the case is impossible, it being clear by the demonstrations of Aristotle that the celestial bodies are impassible, impenetrable, unpartable, etc., I answer that none of the conditions whereby Aristotle distinguishes the celestial bodies from the elementary has any foundation other than what he deduces from the diversity of their natural motions; so that, if it is denied that the circular motion is peculiar to celestial bodies, and affirmed instead that it is agreeable to all naturally moveable bodies, one is led by necessary confidence to say either that the attributes of generated or ungenerated, alterable or unalterable, partable or unpartable, etc., equally and commonly apply to all bodies, as well to the celestial as to the elementary, or that Aristotle has badly and erroneously deduced those from the circular motion which he has assigned to celestial bodies. – Galileo Galileo, Dialogue on the Great World Systems (1632). Revised and Annotated by Giorgio De Santillana (1953), 45.

  • But I do not feel obliged to believe that that same God who has endowed us with senses, reason, and intellect has intended to forgo their use and by some other means to give us knowledge which we can attain by them. – Galileo Galileo, Letter to Madame Christina of Lorraine, Grand Duchess of Tuscany: (1615).

  • But that which will excite the greatest astonishment by far, and which indeed especially moved me to call the attention of all astronomers and philosophers, is this: namely, that I have observed four planets, neither known nor observed by any one of the astronomers before my time, which have their orbits round a certain bright star [Jupiter], one of those previously known, like Venus or Mercury round the sun, and are sometimes in front of it, sometimes behind it, though they never depart from it beyond certain limits. All of which facts were discovered and observed a few days ago by the help of a telescope devised by me, through God’s grace first enlightening my mind. – Galileo Galileo, In pamphlet, The Sidereal Messenger (1610)

  • But what exceeds all wonders, I have discovered four new planets and observed their proper and particular motions, different among themselves and from the motions of all the other stars; and these new planets move about another very large star [Jupiter] like Venus and Mercury, and perchance the other known planets, move about the Sun. As soon as this tract, which I shall send to all the philosophers and mathematicians as an announcement, is finished, I shall send a copy to the Most Serene Grand Duke, together with an excellent spyglass, so that he can verify all these truths. – Galileo Galileo, Letter to the Tuscan Court, 30 Jan 1610.

  • But, because my private lectures and domestic pupils are a great hinderance and interruption of my studies, I wish to live entirely exempt from the former, and in great measure from the latter. … in short, I should wish to gain my bread from my writings. – Galileo Galileo, Reply upon being offered a professorship.

  • By denying scientific principles, one may maintain any paradox. – Galileo Galileo

  • For it is too bad that there are so few who seek the truth and so few who do not follow a mistaken method in philosophy. This is not, however, the place to lament the misery of our century, but to rejoice with you over such beautiful ideas for proving the truth. So I add only, and I promise, that I shall read your book at leisure; for I am certain that I shall find the noblest things in it. And this I shall do the more gladly, because I accepted the view of Copernicus many years ago, and from this standpoint I have discovered from their origins many natural phenomena, which doubtless cannot be explained on the basis of the more commonly accepted hypothesis. – Galileo Galileo, Letter (4 Aug 1597) to Kepler,

  • For the holy Bible and the phenomena of nature proceed alike from the divine Word, the former as the dictate of the Holy Ghost and the latter as the observant executrix of God’s commands. It is necessary for the Bible, in order to be accommodated to the understanding of every man, to speak many things which appear to differ from the absolute truth so far as the bare meaning of the words is concerned. But Nature, on the other hand, is inexorable and immutable; she never transgresses the laws imposed upon her, or cares a whit whether her abstruse reasons and methods of operation are understandable to men. For that reason it appears that nothing physical which sense-experience sets before our eyes, or which necessary demonstrations prove to us, ought to be called in question (much less condemned) upon the testimony of biblical passages which may have some different meaning beneath their words. – Galileo Galileo, Letter to Madame Christina of Lorraine, Grand Duchess of Tuscany

  • I accepted the Copernican position several years ago and discovered from thence the causes of many natural effects which are doubtless inexplicable by the current theories. I have written up many reasons and refutations on the subject, but I have not dared until now to bring them into the open, being warned by the fortunes of Copernicus himself, our master, who procured for himself immortal fame among a few but stepped down among the great crowd (for this is how foolish people are to be numbered), only to be derided and dishonoured. I would dare publish my thoughts if there were many like you; but since there are not, I shall forbear. – Galileo Galileo, Letter to Johannes Kepler, 4 Aug 1597.

  • I cannot but be astonished that Sarsi should persist in trying to prove by means of witnesses something that I may see for myself at any time by means of experiment. Witnesses are examined in doutbful matters which are past and transient, not in those which are actual and present. A judge must seek by means of witnesses to determine whether Peter injured John last night, but not whether John was injured, since the judge can see that for himself. – Galileo Galileo, ‘The Assayer’ (1623), trans. Stillman Drake

  • I do not hope for any relief, and that is because I have committed no crime. I might hope for and obtain pardon, if I had erred, for it is to faults that the prince can bring indulgence, whereas against one wrongfully sentenced while he was innocent, it is expedient, in order to put up a show of strict lawfulness, to uphold rigor… . But my most holy intention, how clearly would it appear if some power would bring to light the slanders, frauds, and stratagems, and trickeries that were used eighteen years ago in Rome in order to deceive the authorities! – Galileo Galileo, In Letter to Nicolas-Claude Fabri de Peiresc (22 Feb 1635).

  • I have written many direct and indirect arguments for the Copernican view, but until now I have not dared to publish them, alarmed by the fate of Copernicus himself, our master. He has won for himself undying fame in the eyes of a few, but he has been mocked and hooted at by an infinite multitude (for so large is the number of fools). I would dare to come forward publicly with my ideas if there were more people of your [Johannes Kepler’s] way of thinking. As this is not the case, I shall refrain. – Galileo Galileo, Letter to Kepler (4 Aug 1597).

  • I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury about the Sun; which at length was established as clear as daylight by numerous other observations.

    Referring to his pioneering telescope observations. – Galileo Galileo, The Starry Messenger (Mar 1610).

  • I wish, my dear Kepler, that we could have a good laugh together at the extraordinary stupidity of the mob. What do you think of the foremost philosophers of this University? In spite of my oft-repeated efforts and invitations, they have refused, with the obstinacy of a glutted adder, to look at the planets or the Moon or my glass [telescope]. – Galileo Galileo, Opere ed Nas. X, 423.

  • I would beg the wise and learned fathers (of the church) to consider with all diligence the difference which exists between matters of mere opinion and matters of demonstration. … [I]t is not in the power of professors of the demonstrative sciences to alter their opinions at will, so as to be now of one way of thinking and now of another. … [D]emonstrated conclusions about things in nature of the heavens, do not admit of being altered with the same ease as opinions to what is permissible or not, under a contract, mortgage, or bill of exchange. – Galileo Galileo, Letter to Cristina di Lorena, Grand Duchess of Tuscany

  • I would say here something that was heard from an ecclesiastic of the most eminent degree [Cardinal Baronius (1538-1607)]: “That the intention of the holy ghost is to teach us how one goes to heaven, not how heaven goes.”— Galileo Galileo, Letter to Madame Christina of Lorraine, Grand Duchess of Tuscany

  • I would say here something that was heard from an ecclesiastic of the most eminent degree: ‘That the intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes. – Galileo Galileo, Letter to Cristina di Lorena, Grand Duchess of Tuscany

  • I, Galileo Galileo, son of the late Vincenzo Galileo, of Florence, aged seventy years, being brought personally to judgment, and kneeling before your Most Eminent and Most Reverend Lords Cardinals, General Inquisitors of the universal Christian republic against heretical depravity, having before my eyes the Holy Gospels, which I touch with my own hands, swear that I have always believed, and now believe, and with the help of God will in future believe, every article which the Holy Catholic and Apostolic Church of Rome holds, teaches, and preaches. But because I have been enjoined by this Holy Office altogether to abandon the false opinion which maintains that the sun is the centre and immovable, and forbidden to hold, defend, or teach the said false doctrine in any manner, and after it hath been signified to me that the said doctrine is repugnant with the Holy Scripture, I have written and printed a book, in which I treat of the same doctrine now condemned, and adduce reasons with great force in support of the same, without giving any solution, and therefore have been judged grievously suspected of heresy; that is to say, that I held and believed that the sun is the centre of the universe and is immovable, and that the earth is not the centre and is movable; willing, therefore, to remove from the minds of your Eminences, and of every Catholic Christian, this vehement suspicion rightfully entertained toward me, with a sincere heart and unfeigned faith, I abjure, curse, and detest the said errors and heresies, and generally every other error and sect contrary to Holy Church; and I swear that I will never more in future say or assert anything verbally, or in writing, which may give rise to a similar suspicion of me; but if I shall know any heretic, or anyone suspected of heresy, that I will denounce him to this Holy Office, or to the Inquisitor or Ordinary of the place where I may be; I swear, moreover, and promise, that I will fulfil and observe fully, all the penances which have been or shall be laid on me by this Holy Office. But if it shall happen that I violate any of my said promises, oaths, and protestations (which God avert!), I subject myself to all the pains and punishments which have been decreed and promulgated by the sacred canons, and other general and particular constitutions, against delinquents of this description. So may God help me, and his Holy Gospels which I touch with my own hands. I, the above-named Galileo Galileo, have abjured, sworn, promised, and bound myself as above, and in witness thereof with my own hand have subscribed this present writing of my abjuration, which I have recited word for word. At Rome, in the Convent of Minerva, June 22, 1633. I, Galileo Galileo, have abjured as above with my own hand. – Galileo Galileo, Abjuration, 22 Jun 1633.

  • If experiments are performed thousands of times at all seasons and in every place without once producing the effects mentioned by your philosophers, poets, and historians, this will mean nothing and we must believe their words rather our own eyes? But what if I find for you a state of the air that has all the conditions you say are required, and still the egg is not cooked nor the lead ball destroyed? Alas! I should be wasting my efforts… for all too prudently you have secured your position by saying that ‘there is needed for this effect violent motion, a great quantity of exhalations, a highly attenuated material and whatever else conduces to it.’ This ‘whatever else’ is what beats me, and gives you a blessed harbor, a sanctuary completely secure. – Galileo Galileo, ‘The Assayer’ (1623), trans. Stillman Drake, Discoveries and Opinions of Galileo (1957), 273.

  • In my studies of astronomy and philosophy I hold this opinion about the universe, that the Sun remains fixed in the centre of the circle of heavenly bodies, without changing its place; and the Earth, turning upon itself, moves round the Sun. – Galileo Galileo, Letter to Cristina di Lorena, Grand Duchess of Tuscany

  • In questions of science the authority of a thousand is not worth the humble reasoning of a single individual. – Galileo Galileo, (1632). Attributed by F. Arago.

  • Infinities and indivisibles transcend our finite understanding, the former on account of their magnitude, the latter because of their smallness; Imagine what they are when combined. – Galileo Galileo

  • It has always seemed to me extreme presumptuousness on the part of those who want to make human ability the measure of what nature can and knows how to do, since, when one comes down to it, there is not one effect in nature, no matter how small, that even the most speculative minds can fully understand. – Galileo Galileo

  • It is a most beautiful and delightful sight to behold the body of the moon. – Galileo Galileo, In pamphlet, The Sidereal Messenger (1610)

  • It reveals to me the causes of many natural phenomena that are entirely incomprehensible in the light of the generally accepted hypotheses. To refute the latter I collected many proofs, but I do not publish them … I would dare to publish my speculations if there were people men like you.

    [Declaring his belief in the heliocentric theory of Copernicus.]— Galileo Galileo, Letter to Kepler (1596)

  • Many of the nobles and senators, although of great age, mounted more than once to the top of the highest church in Venice, in order to see sails and shipping … so far off that it was two hours before they were seen without my spy-glass …, for the effect of my instrument is such that it makes an object fifty miles off appear as large as if it were only five miles away. … The Senate, knowing the way in which I had served it for seventeen years at Padua, … ordered my election to the professorship for life. – Galileo Galileo, Quoted in Will Durant, Ariel Duran, The Age of Reason Begins (1961)

  • Mathematics is the key and door to the sciences. – Galileo Galileo

  • Mathematics is the language in which God wrote the universe. – Galileo Galileo, Quoted in Kim Lim (ed.), 1,001 Pearls of Spiritual Wisdom: Words to Enrich, Inspire, and Guide Your Life (2014), 33

  • Nor need you doubt that Pythagoras, a long time before he found the demonstration for the Hecatomb, had been certain that the square of the side subtending the right angle in a rectangular triangle was equal to the square of the other two sides; the certainty of the conclusion helped not a little in the search for a demonstration. But whatever was the method of Aristotle, and whether his arguing a priori preceded sense a posteriori, or the contrary, it is sufficient that the same Aristotle (as has often been said) put sensible experiences before all discourses. As to the arguments a priori, their force has already been examined.b Dialogue on the Great World Systems (1632).

  • Oh, my dear Kepler, how I wish that we could have one hearty laugh together. Here, at Padua, is the principal professor of philosophy, whom I have repeatedly and urgently requested to look at the moon and planets through my glass, [telescope] which he pertinaciously refuses to do. Why are you not here? what shouts of laughter we should have at this glorious folly! and to hear the professor of philosophy at Pisa laboring before the grand duke with logical arguments, as if with magical incantations, to charm the new planets out of the sky. – Galileo Galileo, From Letter to Johannes Kepler.

  • Philosophy is written in that great book that lies before our gaze—I mean the universe—but we cannot understand it if we do not first learn the language and grasp the symbols in which it is written. – Galileo Galileo, In Francis Crick, The Astonishing Hypothesis: the Scientific Search for the Soul (1995), 203.

  • 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 read the letters in which it is composed. It is written in the 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 wanders about in a dark labyrinth. – Galileo Galileo, In ‘The Assayer’ (1623), trans. Stillman Drake, Discoveries and Opinions of Galileo (1957), 237-8.

  • Philosophy [the universe] is written in that great book which ever lies before our eyes … We cannot understand it if we do not first learn the language and grasp the symbols in which it is written. The book is written in the mathematical language … without whose help it is humanly impossible to comprehend a single word of it, and without which one wanders in vain through a dark labyrinth. – Galileo Galileo

  • Science proceeds more by what it has learned to ignore than what it takes into account. – Galileo Galileo, Found in David Hatcher Childress and Bill Clendenon, Atlantis & the Power System of the Gods (2002), 191.

  • Take note, theologians, that in your desire to make matters of faith out of propositions relating to the fixity of sun and earth you run the risk of eventually having to condemn as heretics those who would declare the earth to stand still and the sun to change position—eventually, I say, at such a time as it might be physically or logically proved that the earth moves and the sun stands still. – Galileo Galileo

  • Note added by Galileo in the preliminary leaves of his copy of Dialogue on the Great World Systems (1632)

  • That sculpture is more admirable than painting for the reason that it contains relief and painting does not is completely false. … Rather, how much more admirable the painting must be considered, if having no relief at all, it appears to have as much as sculpture! – Galileo Galileo Letter to Ludovico Cigoli.

  • The Grand Duke [of Tuscany] …after observing the Medicaean plants several times with me … has now invited me to attach myself to him with the annual salary of one thousand florins, and with the title of Philosopher and Principal Mathematicial to His Highness; without the duties of office to perform, but with the most complete leisure; so that I can complete my Treatises… – Galileo Galileo, From a letter to Kepler.

  • The next object which I have observed is the essence or substance of the Milky Way. By the aid of a telescope anyone may behold this in a manner which so distinctly appeals to the senses that all the disputes which have tormented philosophers through so many ages are exploded at once by the irrefragable evidence of our eyes, and we are freed from wordy disputes upon this subject, for the Galaxy is nothing else but a mass of innumerable stars planted together in clusters. – Galileo Galileo, In pamphlet, The Sidereal Messenger (1610),

  • The number of fixed stars which observers have been able to see without artificial powers of sight up to this day can be counted. It is therefore decidedly a great feat to add to their number, and to set distinctly before the eyes other stars in myriads, which have never been seen before, and which surpass the old, previously known stars in number more than ten times. – Galileo Galileo, In pamphlet, The Sidereal Messenger (1610)

  • The prohibition of science would be contrary to the Bible, which in hundreds of places teaches us how the greatness and the glory of God shine forth marvelously in all His works, and is to be read above all in the open book of the heavens. And let no one believe that the reading of the most exalted thoughts which are inscribed upon these pages is to be accomplished through merely staring up at the radiance of the stars. There are such profound secrets and such lofty conceptions that the night labors and the researches of hundreds and yet hundreds of the keenest minds, in investigations extending over thousands of years would not penetrate them, and the delight of the searching and finding endures forever. – Galileo Galileo, As stated by William H. Hobbs, ‘The Making of Scientific Theories,’

  • The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the Universe to do. – Galileo Galileo

  • Their vain presumption of knowing all can take beginning solely from their never having known anything; for if one has but once experienced the perfect knowledge of one thing, and truly tasted what it is to know, he shall perceive that of infinite other conclusions he understands not so much as one. – Galileo Galileo, Dialogue on the Great World Systems (1632).

  • Two truths cannot contradict one another. – Galileo Galileo, Letter to Madame Christina of Lorraine, Grand Duchess of Tuscany

  • We see only the simple motion of descent, since that other circular one common to the Earth, the tower, and ourselves remains imperceptible. There remains perceptible to us only that of the stone, which is not shared by us; and, because of this, sense shows it as by a straight line, always parallel to the tower, which is built upright and perpendicular upon the terrestrial surface. – Galileo Galileo, Dialogue on the Great World Systems (1632).

  • When the moon is ninety degrees away from the sun it sees but half the earth illuminated (the western half). For the other (the eastern half) is enveloped in night. Hence the moon itself is illuminated less brightly from the earth, and as a result its secondary light appears fainter to us. – Galileo Galileo, The Starry Messenger (1610)

  • You have read my writings, and from them you have certainly understood which was the true and real motive that caused, under the lying mask of religion, this war against me that continually restrains and undercuts me in all directions, so that neither can help come to me from outside nor can I go forth to defend myself, there having been issued an express order to all Inquisitors that they should not allow any of my works to be reprinted which had been printed many years ago or grant permission to any new work that I would print. … a most rigorous and general order, I say, against all my works, omnia et edenda; so that it is left to me only to succumb in silence under the flood of attacks, exposures, derision, and insult coming from all sides. – Galileo Galileo, In Letter to Nicolas-Claude Fabri de Peiresc (16 Mar 1635).

  • [Simplicio] is much puzzled and perplexed. I think I hear him say, ‘To whom then should we repair for the decision of our controversies if Aristotle were removed from the choir? What other author should we follow in the schools, academies, and studies? What philosopher has written all the divisions of Natural Philosophy, and so methodically, without omitting as much as a single conclusion? Shall we then overthrow the building under which so many voyagers find shelter? Shall we destroy that sanctuary, that Prytaneum, where so many students find commodious harbour; where without exposing himself to the injuries of the air, with only the turning over of a few leaves, one may learn all the secrets of Nature.’ – Galileo Galileo, Dialogue on the Great World Systems (1632).

  • …I distinguish two parts of it, which I call respectively the brighter and the darker. The brighter seems to surround and pervade the whole hemisphere; but the darker part, like a sort of cloud, discolours the Moon’s surface and makes it appear covered with spots. Now these spots, as they are somewhat dark and of considerable size, are plain to everyone and every age has seen them, wherefore I will call them great or ancient spots, to distinguish them from other spots, smaller in size, but so thickly scattered that they sprinkle the whole surface of the Moon, but especially the brighter portion of it. These spots have never been observed by anyone before me; and from my observations of them, often repeated, I have been led to the opinion which I have expressed, namely, that I feel sure that the surface of the Moon is not perfectly smooth, free from inequalities and exactly spherical… but that, on the contrary, it is full of inequalities, uneven, full of hollows and protuberances, just like the surface of the Earth itself, which is varied everywhere by lofty mountains and deep valleys. – Galileo Galileo, Describing his pioneering telescope observations of the Moon made from Jan 1610.

Galileo Galileo Quotes

From Wikiquotes

Sidereus Nuncius

  • Quòd tertio loco à nobis fuit obſeruatum, eſt ipſiuſmet LACTEI Circuli eſſentia, ſeu materies, quam Perſpicilli beneficio adeò ad ſenſum licet intueri, vt & altercationes omnes, quæ per tot ſæcula Philoſophos excrucia runt ab oculata certitudine dirimantur, nosque à verboſis dſputationibus liberemur.
    • What was observed by us in the third place is the nature or matter of the Milky Way itself, which, with the aid of the spyglass, may be observed so well that all the disputes that for so many generations have vexed philosophers are destroyed by visible certainty, and we are liberated from wordy arguments.
      • Original text as reproduced in Edward Tufte, Beautiful Evidence (Cheshire, Connecticut: Graphics Press LLC, 2006), 101 (p. 3 of 4, insert between pp. 16V & 17R. Original manuscript renders the “q” in “nosque” with acute accent.)
      • Translation by Albert Van Helden in Sidereus Nuncius (Chicago, 1989), 62
  • Revealing great, unusual, and remarkable spectacles, opening these to the consideration of every man, and especially of philosophers and astronomers; as observed by Galileo Galileo, Gentleman of Florence, Professor of Mathematics in the University of Padua, with the aid of a spyglass lately invented by him, in the surface of the Moon, in innumerable fixed stars, in nebulae, and above all in four planets swiftly revolving about Jupiter at differing distances and periods, and known to no one before the author recently perceived them and decided they should be named the Medicean Stars
    • Translation by Stillman Drake in Discoveries and Opinions of Galileo (1957)
  • About ten months ago a report reached my ears that a certain Fleming had constructed a spyglass by means of which visible objects, though very distant from the eye of the observer, were distinctly seen as if nearby. Of the truly remarkable effect several experiences were related, to which some persons gave credence while others denied them. A few days later a report was confirmed to me in a letter from a noble Frenchman in Paris, Jacques Badovere, which caused me to apply myself wholeheartedly to inquire into means by which I might arrive at the invention of a similar instrument. This I did shortly afterwards, my basis being the theory of refraction. First I prepared a tube of lead, at the ends I fitted two glass lenses, both plane on one side while on the other side one was spherically convex and the other concave. Then placing my eye near the concave lens I perceived objects satisfactorily large and near, for they appeared three times closer and nine times larger than when seen with the naked eye alone. Next I constructed another one, more accurate, which represented objects as enlarged more than sixty times. 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 one thousand times larger and over thirty times closer than when regarded with our natural vision.
    • Translation by Stillman Drake in Discoveries and Opinions of Galileo (1957)
  • 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 ten times exceeding the old and familiar stars.
    • Translation by Stillman Drake in Discoveries and Opinions of Galileo (1957)

Letter to Benedetto Castelli

  • “It seems to me that it was well said by Madama Serenissima, and insisted on by your reverence, that the Holy Scripture cannot err, and that the decrees therein contained are absolutely true and inviolable. But I should have in your place added that, though Scripture cannot err, its expounders and interpreters are liable to err in many ways; and one error in particular would be most grave and most frequent, if we always stopped short at the literal signification of the words.”

Letter to the Grand Duchess Christina

Essay published in 1615, in response to enquiries of Christina of Tuscany, as quoted in Aspects of Western Civilization : Problems and Sources in History (1988) by Perry McAdow Rogers, p. 53
  • Some years ago, as Your Serene Highness well knows, I discovered in the heavens many things that had not been seen before our own age. The novelty of these things, as well as some consequences which followed from them in contradiction to the physical notions commonly held among academic philosophers, stirred up against me no small number of professors — as if I had placed these things in the sky with my own hands in order to upset nature and overturn the sciences. They seemed to forget that the increase of known truths stimulates the investigation, establishment, and growth of the arts; not their diminution or destruction.
  • The passage of time has revealed to everyone the truths that I previously set forth; and, together with the truth of the facts, there has come to light the great difference in attitude between those who simply and dispassionately refused to admit the discoveries to be true, and those who combined with their incredulity some reckless passion of their own. Men who were well grounded in astronomical and physical science were persuaded as soon as they received my first message. There were others who denied them or remained in doubt only because of their novel and unexpected character, and because they had not yet had the opportunity to see for themselves. These men have by degrees come to be satisfied. But some, besides allegiance to their original error, possess I know not what fanciful interest in remaining hostile not so much toward the things in question as toward their discoverer. No longer being able to deny them, these men now take refuge in obstinate silence, but being more than ever exasperated by that which has pacified and quieted other men, they divert their thoughts to other fancies and seek new ways to damage me.
  • Persisting in their original resolve to destroy me and everything mine by any means they can think of, these men are aware of my views in astronomy and philosophy. They know that as to the arrangement of the parts of the universe, I hold the sun to be situated motionless in the center of the revolution of the celestial orbs while the earth revolves about the sun. They know also that I support this position not only by refuting the arguments of Ptolemy and Aristotle, but by producing many counter-arguments; in particular, some which relate to physical effects whose causes can perhaps be assigned in no other way. In addition there are astronomical arguments derived from many things in my new celestial discoveries that plainly confute the Ptolemaic system while admirably agreeing with and confirming the contrary hypothesis.
    • Variant translation: I hold that the Sun is located at the centre of the revolutions of the heavenly orbs and does not change place, and that the Earth rotates on itself and moves around it. Moreover … I confirm this view not only by refuting Ptolemy’s and Aristotle’s arguments, but also by producing many for the other side, especially some pertaining to physical effects whose causes perhaps cannot be determined in any other way, and other astronomical discoveries; these discoveries clearly confute the Ptolemaic system, and they agree admirably with this other position and confirm it.
  • To this end they make a shield of their hypocritical zeal for religion. They go about invoking the Bible, which they would have minister to their deceitful purposes. Contrary to the sense of the Bible and the intention of the holy Fathers, if I am not mistaken, they would extend such authorities until even in purely physical matters — where faith is not involved — they would have us altogether abandon reason and the evidence of our senses in favor of some biblical passage, though under the surface meaning of its words this passage may contain a different sense.
  • Copernicus never discusses matters of religion or faith, nor does he use argument that depend in any way upon the authority of sacred writings which he might have interpreted erroneously. … He did not ignore the Bible, but he knew very well that if his doctrine were proved, then it could not contradict the Scriptures when they were rightly understood.
  • Nature … is inexorable and immutable; she never transgresses the laws imposed upon her, or cares a whit whether her abstruse reasons and methods of operation are understandable to men. For that reason it appears that nothing physical which sense-experience sets before our eyes, or which necessary demonstrations prove to us, ought to be called in question (much less condemned) upon the testimony of biblical passages which may have some different meaning beneath their words. For the Bible is not chained in every expression to conditions as strict as those which govern all physical effects; nor is God any less excellently revealed in Nature’s actions than in the sacred statements of the Bible.
  • I do not feel obliged to believe that the same God who has endowed us with senses, reason, and intellect has intended us to forgo their use and by some other means to give us knowledge which we can attain by them.
  • I would say here something that was heard from an ecclesiastic of the most eminent degree [probably Caesar Baronius]: “The intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes.”
    • Variant translation: I would say here something that was heard from an ecclesiastic of the most eminent degree: “That the intention of the Holy Spirit is to teach us how one goes to heaven, not how the heavens go.”

Il Saggiatore

  • Philosophy is written in this grand 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 as 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.
    • From Italian: La filosofia è scritta in questo grandissimo libro, che continuamente ci sta aperto innanzi agli occhi (io dico l’Universo), ma non si può intendere, se prima non il sapere a intender la lingua, e conoscer i caratteri ne quali è scritto. Egli è scritto in lingua matematica, e i caratteri son triangoli, cerchi ed altre figure geometriche, senza i quali mezzi è impossibile intenderne umanamente parola; senza questi è un aggirarsi vanamente per un oscuro labirinto.[1]
    • Other translations:
      • Philosophy is written in that great book which ever lies before our eyes — I mean the universe — but we cannot understand it if we do not first learn the language and grasp the symbols, in which it is written. This book is written in the mathematical language, and the symbols are triangles, circles and other geometrical figures, without whose help it is impossible to comprehend a single word of it; without which one wanders in vain through a dark labyrinth.
        • The Assayer (1623), as translated by Thomas Salusbury (1661), p. 178, as quoted in The Metaphysical Foundations of Modern Science (2003) by Edwin Arthur Burtt, p. 75.
      • Philosophy is written in this grand book — I mean the universe — which stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language in which it is written. It is written in the 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 is wandering about in a dark labyrinth.
        • As translated in The Philosophy of the Sixteenth and Seventeenth Centuries (1966) by Richard Henry Popkin, p. 65

Letter to Francesco Ingoli

Letter to Francesco Ingoli (1578-1649), as translated in Galileo at Work: His Scientific Biography (1978) by Stillman Drake, p. 294
  • Whence do you have it that the terrestrial globe is so heavy? For my part, either I do not know what heaviness is, or the terrestrial globe is neither heavy nor light, as likewise all other globes of the universe. Heaviness to me (and I believe to Nature) is that innate tendency by which a body resists being moved from its natural place and by which, when forcibly removed therefrom, it spontaneously returns there. Thus a bucketful of water raised on high and set free, returns to the sea; but who will say that the same water remains heavy in the sea, when being set free there, does not move?
  • I tell you that if natural bodies have it from Nature to be moved by any movement, this can only be circular motion, nor is it possible that Nature has given to any of its integral bodies a propensity to be moved by straight motion. I have many confirmations of this proposition, but for the present one alone suffices, which is this. I suppose the parts of the universe to be in the best arrangement, so that none is out of its place, which is to say that Nature and God have perfectly arranged their structure. This being so, it is impossible for those parts to have it from Nature to be moved in straight, or in other than circular motion, because what moves straight changes place, and if it changes place naturally, then it was at first in a place preternatural to it, which goes against the supposition. Therefore, if the parts of the world are well ordered, straight motion is superfluous and not natural, and they can only have it when some body is forcibly removed from its natural place, to which it would then return by a straight line, for thus it appears that a part of the earth does [move] when separated from its whole. I said “it appears to us,” because I am not against thinking that not even for such an effect does Nature make use of straight line motion.
    • A note on this statement is included by Stillman Drake in his Galileo at Work, His Scientific Biography (1981): Galileo adhered to this position in his Dialogue at least as to the “integral bodies of the universe.” by which he meant stars and planets, here called “parts of the universe.” But he did not attempt to explain the planetary motions on any mechanical basis, nor does this argument from “best arrangement” have any bearing on inertial motion, which to Galileo was indifference to motion and rest and not a tendency to move, either circularly or straight.

Dialogue Concerning the Two Chief World Systems

  • It always seems to me extreme rashness on the part of some when they want to make human abilities the measure of what nature can do. On the contrary, there is not a single effect in nature, even the least that exists, such that the most ingenious theorists can arrive at a complete understanding of it. This vain presumption of understanding everything can have no other basis than never understanding anything. For anyone who had experienced just once the perfect understanding of one single thing, and had truly tasted how knowledge is accomplished, would recognize that of the infinity of other truths he understands nothing.
    • Day One
  • To apply oneself to great inventions, starting from the smallest beginnings, is no task for ordinary minds; to divine that wonderful arts lie hid behind trivial and childish things is a conception for superhuman talents.
  • I cannot without great astonishment — I might say without great insult to my intelligence — hear it attributed as a prime perfection and nobility of the natural and integral bodies of the universe that they are invariant, immutable, inalterable, etc., while on the other hand it is called a great imperfection to be alterable, generable, mutable, etc. For my part I consider the earth very noble and admirable precisely because of the diverse alterations, changes, generations, etc. that occur in it incessantly. If, not being subject to any changes, it were a vast desert of sand or a mountain of jasper, or if at the time of the flood the waters which covered it had frozen, and it had remained an enormous globe of ice where nothing was ever born or ever altered or changed, I should deem it a useless lump in the universe, devoid of activity and, in a word, superfluous and essentially non-existent. This is exactly the difference between a living animal and a dead one; and I say the same of the moon, of Jupiter, and of all other world globes.
    The deeper I go in considering the vanities of popular reasoning, the lighter and more foolish I find them. What greater stupidity can be imagined than that of calling jewels, silver, and gold “precious,” and earth and soil “base”? People who do this ought to remember that if there were as great a scarcity of soil as of jewels or precious metals, there would not be a prince who would not spend a bushel of diamonds and rubies and a cartload of gold just to have enough earth to plant a jasmine in a little pot, or to sow an orange seed and watch it sprout, grow, and produce its handsome leaves, its fragrant flowers, and fine fruit. It is scarcity and plenty that make the vulgar take things to be precious or worthless; they call a diamond very beautiful because it is like pure water, and then would not exchange one for ten barrels of water. Those who so greatly exalt incorruptibility, inalterability, etc. are reduced to talking this way, I believe, by their great desire to go on living, and by the terror they have of death. They do not reflect that if men were immortal, they themselves would never have come into the world. Such men really deserve to encounter a Medusa’s head which would transmute them into statues of jasper or of diamond, and thus make them more perfect than they are.

    • Sagredo
    • Variant translation: I cannot without great wonder, nay more, disbelief, hear it being attributed to natural bodies as a great honor and perfection that they are impassable, immutable, inalterable, etc.: as conversely, I hear it esteemed a great imperfection to be alterable, generable, and mutable. It is my opinion that the earth is very noble and admirable by reason of the many and different alterations, mutations, and generations which incessantly occur in it. And if, without being subject to any alteration, it had been one great heap of sand, or a mass of jade, or if, since the time of the deluge, the waters freezing which covered it, it had continued an immense globe of crystal, wherein nothing had ever grown, altered, or changed, I should have esteemed it a wretched lump of no benefit to the Universe, a mass of idleness, and in a word superfluous, exactly as if it had never been in Nature. The difference for me would be the same as between a living and a dead creature. I say the same concerning the Moon, Jupiter, and all the other globes of the Universe.
      The more I delve into the consideration of the vanity of popular discourses, the more empty and simple I find them. What greater folly can be imagined than to call gems, silver, and gold noble, and earth and dirt base? For do not these persons consider that if there were as great a scarcity of earth as there is of jewels and precious metals, there would be no king who would not gladly give a heap of diamonds and rubies and many ingots of gold to purchase only so much earth as would suffice to plant a jessamine in a little pot or to set a tangerine in it, that he might see it sprout, grow up, and bring forth such goodly leaves, fragrant flowers, and delicate fruit? It is scarcity and plenty that makes things esteemed and despised by the vulgar, who will say that there is a most beautiful diamond, for it resembles a clear water, and yet would not part from it for ten tons of water. ‘These men who so extol incorruptibility, inalterability, and so on, speak thus, I believe, out of the great desire they have to live long and for fear of death, not considering that, if men had been immortal, they would not have come into the world. These people deserve to meet with a Medusa’s head that would transform them into statues of diamond and jade, that so they might become more perfect than they are.

      • Part of this passage, in Italian, I detrattori della corruptibilitá meriterebber d’esser cangiati in statue., has also ben translated into English as “Detractors of corruptibility deserve being turned into statues.”
        • Dialogo sopra i due massimi sistemi del mondo. (PDF), Le Opere di Galileo Galileo vol. VII, pg. 58.
        • Compare Maimonides “If man were never subject to change there could be no generation; there would be one single being…” Guide for the Perplexed (c. 1190)
  • If what we are discussing were a point of law or of the humanities, in which neither true nor false exists, one might trust in subtlety of mind and readiness of tongue and in the greater experience of the writers, and expect him who excelled in those things to make his reasoning most plausible, and one might judge it to be the best. But in the natural sciences, whose conclusions are true and necessary and have nothing to do with human will, one must take care not to place oneself in the defense of error; for here a thousand Demostheneses and a thousand Aristotles would be left in the lurch by every mediocre wit who happened to hit upon the truth for himself. Therefore, Simplicio, give up this idea and this hope of yours that there may be men so much more learned, erudite, and well-read than the rest of us as to be able to make that which is false become true in defiance of nature.
    • Salviati, p. 61
  • If you could see the earth illuminated when you were in a place as dark as night, it would look to you more splendid than the moon.
    • Salviati, p. 88
  • In the long run my observations have convinced me that some men, reasoning preposterously, first establish some conclusion in their minds which, either because of its being their own or because of their having received it from some person who has their entire confidence, impresses them so deeply that one finds it impossible ever to get it out of their heads. Such arguments in support of their fixed idea as they hit upon themselves or hear set forth by others, no matter how simple and stupid these may be, gain their instant acceptance and applause. On the other hand whatever is brought forward against it, however ingenious and conclusive, they receive with disdain or with hot rage — if indeed it does not make them ill. Beside themselves with passion, some of them would not be backward even about scheming to suppress and silence their adversaries.
    • p. 322
  • Among all the great men who have philosophized about this remarkable effect, I am more astonished at Kepler than at any other. Despite his open and acute mind, and though he has at his fingertips the motions attributed to the earth, he nevertheless lent his ear and his assent to the moon’s dominion over the waters, to occult properties, and to such puerilities.
    • In regard to Kepler’s belief of the moon affecting the tides of the Earth, p. 328
  • The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do.
    • Loose paraphrase of Salviati on Day 3: “For when the sun draws up some vapors here, or warms a plant there, it draws these and warms this as if it had nothing else to do. Even in ripening a bunch of grapes, or perhaps just a single grape, it applies itself so effectively that it could not do more even if the goal of all its affairs were just the ripening of this one grape.”
  • Of such are the mathematical sciences alone; that is, geometry and arithmetic, in which the Divine intellect indeed knows infinitely more propositions, since it knows all. But with regard to those few which the human intellect does understand, I believe its knowledge equals the Divine in objective certainty, for here it succeeds in understanding necessity, beyond which there can be no greater sureness.
    • In the 1661 translation by Thomas Salusbury: … such are the pure Mathematical sciences, to wit, Geometry and Arithmetick: in which Divine Wisdom knows infinite more propositions, because it knows them all; but I believe that the knowledge of those few comprehended by humane understanding, equalleth the divine, as to the certainty objectivè, for that it arriveth to comprehend the neces­sity thereof, than which there can be no greater certainty.” p. 92 (from the Archimedes Project)
    • In the original Italian: … tali sono le scienze matematiche pure, cioè la geometria e l’aritmetica, delle quali l’intelletto divino ne sa bene infinite proposizioni di piú, perché le sa tutte, ma di quelle poche intese dall’intelletto umano credo che la cognizione agguagli la divina nella certezza obiettiva, poiché arriva a comprenderne la necessità, sopra la quale non par che possa esser sicurezza maggiore.” (from the copy at the Italian Wikisource).
  • I cannot sufficiently admire the eminence of those men’s wits, that have received and held it to be true, and with the sprightliness of their judgments offered such violence to their own senses, as that they have been able to prefer that which their reason dictated to them, to that which sensible experiments represented most manifestly to the contrary. …I cannot find any bounds for my admiration, how that reason was able in Aristarchus and Copernicus, to commit such a rape on their senses, as in despite thereof to make herself mistress of their credulity.
    • Thomas Salusbury translation (1661) p. 301 as quoted by Edwin Arthur Burtt, The Metaphysical Foundations of Modern Physical Science (1925)

Letter to Fr. Vincenzo Renieri

Letter to Galileo’s “intimate friend and disciple, the Father Vincenzo Renieri” (1606-1647), who was chair of the mathematics department at the University of Pisa from 1640 to 1647, as quoted in A Selection from Italian Prose Writers : with a double translation: for the use of students of the Italian language on the Hamiltonian system (1828)
  • After the publication of my dialogues, I was summoned to Rome by the Congregation of the holy Office, where, being arrived on the 10th of February 1633, I was subjected to the infinite clemency of that tribunal, and of the Sovereign Pontiff, Urban the Eighth; who, notwithstanding, thought me deserving of his esteem.
    • pp. 145–146
  • I am certainly interested in a tribunal in which, for having used my reason, I was deemed little less than a heretic. Who knows but men will reduce me from the profession of a philosopher to that of historian of the Inquisition! But they behave to me in order that I may become the ignoramus and the fool of Italy
    • p. 244
  • I was obliged to retract, like a good Catholic, this opinion of mine; and as a punishment my dialogue was prohibited; and after five months being dismissed from Rome (at the time that the city of Florence was infected with plague), the habitation which with generous pity was assigned to me, was that of the dearest friend I had in Siena, Monsignor the Archbishop Piccolomini, whose most agreeable conversation I enjoyed with such quite and satisfaction of mind, that having there resumed my studies, I discovered and demonstrated a great number on the mechanical conclusions on the resistance of solids … after about five months, the pestilence having ceased, the confinement of that house was changed by His Holiness for the freedom of the country so agreeable to me, whence I returned to the villa of Bellosguardo, and afterwards to Arcetri, where I still breathe salubrious air near my dear native-country Florence. Stay sane.
    • p. 251-253

Dialogues and Mathematical Demonstrations Concerning Two New Sciences

Henry Crew & Alfonso de Salvio translation (1914) unless otherwise noted
Interlocutors: Salviati, Sagredo and Simplicio
  • Well, since paradoxes are at hand, let us see how it might be demonstrated that in a finite continuous extension it is not impossible for infinitely many voids to be found.
    • Salviati, First Day, Stillman Drake translation (1974)
  • My purpose is to set forth a very new science dealing with a very ancient subject. There is, in nature, perhaps nothing older than motion, concerning which the books written by philosophers are neither few nor small; nevertheless I have discovered by experiment some properties of it which are worth knowing and which have not hitherto been either observed or demonstrated. Some superficial observations have been made, as, for instance, that the free motion [naturalem motum] of a heavy falling body is continuously accelerated; but to just what extent this acceleration occurs has not yet been announced; for so far as I know, no one has yet pointed out that the distances traversed, during equal intervals of time, by a body falling from rest, stand to one another in the same ratio as the odd numbers beginning with unity.
    • Author, Third Day. Change of Position
  • It has been observed that missiles and projectiles describe a curved path of some sort; however no one has pointed out the fact that this path is a parabola. But this and other facts, not few in number or less worth knowing, I have succeeded in proving; and what I consider more important, there have been opened up to this vast and most excellent science, of which my work is merely the beginning, ways and means by which other minds more acute than mine will explore its remote corners.
    • Author, Third Day. Change of Position
  • This [experimentation] is the custom—and properly so—in those sciences where mathematical demonstrations are applied to natural phenomena, as is seen in the case of perspective, astronomy, mechanics, music, and others where the principles, once established by well-chosen experiments, become the foundations of the entire superstructure.
    • Salviati, Third Day. Change of Position
  • Salvio. A book which, indeed, is not to be placed second to any produced by the most eminent geometers either of the present or of the past; a book which, as soon as it fell into the hands of our Academician, led him to abandon his own researches along these lines; for he saw how happily everything had been treated and demonstrated by Valerio.
    • P. 148
  • Sagredo: Indeed, I think we may concede to our Academician, without flattery, his claim that in the principle [principio, i. e., accelerated motion] laid down in this treatise he has established a new science dealing with a very old subject. Observing with what ease and clearness he deduces from a single principle the proofs of so many theorems, I wonder not a little how such a question escaped the attention of Archimedes, Apollonius, Euclid and so many other mathematicians and illustrious philosophers, especially since so many ponderous tomes have been devoted to the subject of motion. (Galileo referred to himself as the/our Academician in his dialogue)
    • Third Day P. 242
  • I mentally conceive of some moveable [sphere] projected on a horizontal plane, all impediments being put aside. Now it is evident… that equable motion on this plane would be perpetual if the plane were of infinite extent, but if we assume it to be ended, and [situated] on high, the movable, driven to the end of this plane and going on further, adds on to its previous equable and indelible motion, that downward tendency which it has from its heaviness. Thus, there emerges a certain motion, compounded…
    • Author, Day Four, On the Motion of Projectiles, Stillman Drake translation (1974) p. 268
  • Proposition I. Theorem I: When a projectile is carried in motion compounded from equable horizontal and from naturally accelerated downward [motions], it describes a semiparabolic line in its movement.
    • Author, Day Four, Stillman Drake translation (1974) p. 269
  • The speed of the ball—thanks to opposition from the air—will not go on increasing forever. Rather, what will happen is seen in bodies of very little weight falling through no great distance; I mean, a reduction to equable motion, which will occur also in a lead or iron ball after the descent of some thousands of braccia. This bounded terminal speed will be called the maximum that such a heavy body can naturally attain through the air
    • Salviati, Day Four, 278-279 Stillman Drake translation (1974)
  • It seems to me proper to adorn the Author’s thought here with its conformity to a conception of Plato’s regarding the determination of the various speeds of equable motion in the celestial motions of revolution. …he said that God, after having created the movable celestial bodies, in order to assign to them those speeds with which they must be moved perpetually in equable circular motion, made them depart from rest and move through determinate spaces in that natural straight motion in which we sensibly see our moveables to be moved from the state of rest, successively accelerating. And he added that these having been made to gain that degree [of speed] which it pleased God that they should maintain forever, He turned their straight motion into circulation, the only kind [of motion] that is suitable to be conserved equably, turning always without retreat from or approach toward any pre-established goal desired by them. The conception is truly worthy of Plato, and it is to be more esteemed to the extent that its foundations, of which Plato remained silent, but which were discovered by our Author in removing their poetical mask or semblance, show it the guise of a true story.
    • I. Bernard Cohen’s thesis: Galileo believed only circular (not straight line) motion may be conserved (perpetual), see The New Birth of Physics (1960).
    • Sagredo, Day Four, Stillman Drake translation (1974) pp.283-284

Letter to Giovanni Battista Baliani

Letter to Giovanni Battista Baliani (1 August 1639), as translated in Galileo at Work : His Scientific Biography (1978) by Stillman Drake, p. 399 – 401
  • It now remains that we find the amount of time of descent through the channel. This we shall obtain from the marvelous property of the pendulum, which is that it makes all its vibrations, large or small, in equal times. This requires, once and for all, that two or three or four patient and curious friends, having noted a fixed star that stands against some fixed marker, taking a pendulum of any length, shall go counting its vibrations during the whole time of return of the fixed star to its original point, and this will be the number of vibrations in 24 hours. From the number of these we can find the number of vibrations of any other pendulums, longer or shorter, at will, so that if for example those counted by us in 24 hours were 234,567, then taking another shorter pendulum with which one counts 800 vibrations while another counts 150 of the longer pendulum, we already have, by the golden rule, the number of vibrations for the whole time of 24 hours; and if we want to know the time of descent through the channel, we can easily find not only the minutes, seconds, and sixtieths of seconds, but beyond that as we please. It is true that we can pass a more exact measure by having observed the flow of water through a thin passage, for by collecting this and having weighed what passes in one minute, for example, then by weighing what passes in the time of descent through the channel we can find the most exact measure and quantity of this time, especially by making use of a balance so precise as to weigh one sixtieth of a grain.
  • If I shall have sufficient strength to improve and amplify what was written and published by me up to now about motion by adding some little speculations, and in particular those relating to the force of percussion, in the investigation of which I have consumed hundreds and thousands of hours, and finally reduced this to very easy explanation, so that people can understand it in less than half an hour of time.

Other quotes

  • I esteem myself happy to have as great an ally as you in my search for truth. I will read your work … all the more willingly because I have for many years been a partisan of the Copernican view because it reveals to me the causes of many natural phenomena that are entirely incomprehensible in the light of the generally accepted hypothesis. To refute the latter I have collected many proofs, but I do not publish them, because I am deterred by the fate of our teacher Copernicus who, although he had won immortal fame with a few, was ridiculed and condemned by countless people (for very great is the number of the stupid).
    • Letter to Johannes Kepler (1596), as quoted in The Story of Civilization : The Age of Reason Begins, 1558-1648 (1935) by Will Durant, p. 603
  • What has philosophy got to do with measuring anything? It’s the mathematicians you have to trust, and they measure the skies like we measure a field.
    • “Matteo” in Concerning the New Star (1606)
  • My dear Kepler, what would you say of the learned here, who, replete with the pertinacity of the asp, have steadfastly refused to cast a glance through the telescope? What shall we make of this? Shall we laugh, or shall we cry?
    • Letter to Johannes Kepler (1610), as quoted in The Crime of Galileo (1955) by Giorgio De Santillana
  • sì perché l’autorità dell’opinione di mille nelle scienze non val per una scintilla di ragione di un solo, sì perché le presenti osservazioni spogliano d’autorità i decreti de’ passati scrittori, i quali se vedute l’avessero, avrebbono diversamente determinato.
    • for in the sciences the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man. Besides, the modern observations deprive all former writers of any authority, since if they had seen what we see, they would have judged as we judge.
      • Third letter on sunspots (December 1612) to Mark Wesler (1558 – 1614), as quoted in Discoveries and Opinions of Galileo (1957) by Stillman Drake, p. 134 – 135; Italian text online at Liber Liber, also from IntraText.
    • Variant translation: In questions of science the authority of a thousand is not worth the humble reasoning of a single individual.
      • As quoted in Biographies of Distinguished Scientific Men (1859) by François Arago, as translated by Baden Powell, Robert Grant, and William Fairbairn, p. 365
  • Surely, God could have caused birds to fly with their bones made of solid gold, with their veins full of quicksilver, with their flesh heavier than lead, and with their wings exceedingly small. He did not, and that ought to show something. It is only in order to shield your ignorance that you put the Lord at every turn to the refuge of a miracle.
    • Notes in a copy of Jean-Baptiste Morin’s “Famous and ancient problems of the earth’s motion or rest, yet to be solved” (published 1631), as quoted in The Crime of Galileo (1976) by Giorgio De Santillana, p. 167
  • After an injunction had been judicially intimated to me by this Holy Office, to the effect that I must altogether abandon the false opinion that the sun is the center of the world and immovable, and that the earth is not the center of the world, and moves, and that I must not hold, defend, or teach in any way whatsoever, verbally or in writing, the said false doctrine, and after it had been notified to me that the said doctrine was contrary to Holy Scripture — I wrote and printed a book in which I discuss this new doctrine already condemned, and adduce arguments of great cogency in its favor, without presenting any solution of these, and for this reason I have been pronounced by the Holy Office to be vehemently suspected of heresy, that is to say, of having held and believed that the Sun is the center of the world and immovable, and that the earth is not the center and moves:
    Therefore, desiring to remove from the minds of your Eminences, and of all faithful Christians, this vehement suspicion, justly conceived against me, with sincere heart and unfeigned faith I abjure, curse, and detest the aforesaid errors and heresies, and generally every other error, heresy, and sect whatsoever contrary to the said Holy Church
    , and I swear that in the future I will never again say or assert, verbally or in writing, anything that might furnish occasion for a similar suspicion regarding me; but that should I know any heretic, or person suspected of heresy, I will denounce him to this Holy Office, or to the Inquisitor or Ordinary of the place where I may be. Further, I swear and promise to fulfill and observe in their integrity all penances that have been, or that shall be, imposed upon me by this Holy Office. And, in the event of my contravening, (which God forbid) any of these my promises and oaths, I submit myself to all the pains and penalties imposed and promulgated in the sacred canons and other constitutions, general and particular, against such delinquents. So help me God, and these His Holy Gospels, which I touch with my hands.
    I, the said Galileo Galileo, have abjured, sworn, promised, and bound myself as above; and in witness of the truth thereof I have with my own hand subscribed the present document of my abjuration, and recited it word for word at Rome, in the Convent of Minerva, this twenty-second day of June, 1633.

    • Recantation (22 June 1633) as quoted in The Crime of Galileo (1955) by Giorgio de Santillana, p. 312.
  • I have been in my bed for five weeks, oppressed with weakness and other infirmities from which my age, seventy four years, permits me not to hope release. Added to this (proh dolor! [O misery!]) the sight of my right eye — that eye whose labors (dare I say it) have had such glorious results — is for ever lost. That of the left, which was and is imperfect, is rendered null by continual weeping.
    • Letter to Élie Diodati (4 July 1637), as translated in The Private Life of Galileo : Compiled primarily from his correspondence and that of his eldest daughter, Sister Maria Celeste (1870) by Mary Allan-Olney, p. 278
  • Alas! Your dear friend and servant Galileo has been for the last month hopelessly blind; so that this heaven, this earth, this universe, which I by my marvelous discoveries and clear demonstrations had enlarged a hundred thousand times beyond the belief of the wise men of bygone ages, henceforward for me is shrunk into such a small space as is filled by my own bodily sensations.
    • Letter to Élie Diodati (2 January 1638), as translated in The Private Life of Galileo : Compiled primarily from his correspondence and that of his eldest daughter, Sister Maria Celeste (1870) by Mary Allan-Olney, p. 279
  • See now the power of truth; the same experiment which at first glance seemed to show one thing, when more carefully examined, assures us of the contrary.
    • Discourses and Mathematical Demonstrations Relating to Two New Sciences (1638); Discorsi e dimostrazioni matematiche, intorno à due nuove scienze, as translated by Henry Crew and Alfonso de Salvio (1914)
  • Light held together by moisture.
    • His description of wine, as quoted in Discoveries and Opinions of Galileo (1957) by Stillman Drake, p. 5
  • Names and attributes must be accommodated to the essence of things, and not the essence to the names, since things come first and names afterwards.
    • As quoted in Discoveries and Opinions of Galileo (1957) by Stillman Drake, p. 92
    • Variant translation: Names and attributes must be accommodated to the essence of things, and not the essence to the names, because things came first, and their names subsequently.

Attributed

  • You cannot teach a man anything, you can only help him to find it within himself.
    • As quoted in How to Win Friends and Influence People (1935) by Dale Carnegie, p. 117; also paraphrased as “You cannot teach a man anything, you can only help him to find it for himself.” Attributions are found as early as 1882.[2]
  • All truths are easy to understand once they are discovered; the point is to discover them.
    • As quoted in Angels in the workplace: stories and inspirations for creating a new world of work (1999) by Melissa Giovagnoli
  • Mathematics is the key and door to the sciences.
    • As quoted in Building Fluency Through Practice and Performance (2008) by Timothy Rasinski and Lorraine Griffith, p. 64, but in fact a quotation by Roger Bacon: Et harum scientiarum porta et clavis est Mathematica, “And of these sciences the door and key is mathematics”, from Bacon’s Opus Majus (1267) [1].
  • Measure what is measurable, and make measurable what is not so.
    • The quote is widely misattributed to Galileo, but is actually from two French scholars, Antoine-Augustin Cournot and Thomas-Henri Martin. See “Der messende Luchs: Zwei verbreitete Fehler in der Galileo-Literatur” by Andreas Kleinert in “NTM Zeitschrift für Geschichte der Wissenschaften, Technik und Medizin” May 2009, Volume 17, Issue 2, pp 199–206.
  • I have never met a man so ignorant that I could not learn something from him.
    • As quoted in The Story of Civilization : The Age of Reason Begins, 1558-1648 (1935) by Will Durant, p. 605

Disputed

  • Eppur si muove.
    • “And yet it moves” or “still it moves” is a comment he is alleged to have made in regard to the Earth after his recantation before the Inquisition. Giuseppe Baretti was apparently the first person to record the story. Noted as a misattribution in Paul F. Boller, John George, They Never Said It: A Book of Fake Quotes, Misquotes, and Misleading Attributions (1990), p. 30.

Quotes about Galileo

  • [I]t was upon… inequality of motions in point of velocity that Galileo built his theory of flux and reflux of the sea; supposing that the earth revolved faster than the water could follow; and that the water was therefore first gathered in a heap and then fell down, as we see in a basin of water moved quickly. But this he devised upon an assumption which cannot be allowed, viz. that the earth moves; and also without being well informed as to the sexhorary motion of the tide.
    • Francis Bacon, Novum Organum (1620) as quoted in The Works of Francis Bacon: Translations of the Philosophical Works (1875) p. 212, Vol. IV of Translations of the Philosophical Works ed. James Spedding, Robert Leslie Ellis, Douglas Denon Heath.
  • Galileo observed as early as 1638 that there are precisely as many squares 1, 4, 9, 16, 25,… as are positive integers all together. This is evident from the sequences
    1, 2, 3, 4, 5, 6, … , n, …
    12, 22, 32, 42, 52, 62, …, n, …
    He thus recognized the fundamental distinction between finite and infinite classes that became current in the late nineteenth century. An infinite class is one in which there is a one-to-one correspondence between the whole class and a subclass of the whole. Or, what is equivalent, there are as many things in one part of an infinite class as there are in the whole class.
    …A class whose elements can be put in a one-to-one correspondence with the integers 1, 2, 3, … is said to be denumerable. All the points in any line segment, finite or infinite in length, form a non-denumerable set. A basic course in calculus starts from the theory of point sets. The distinction between denumerable and non-denumerable classes was not started by Galileo; it was observed about 1840 by Bolzano and in 1878 by Cantor. But Galileo’s recognition of the cardinal property of all infinite classes makes him one of the genuine anticipators in the history of calculus. The other was Archimedes.

    • Eric Temple Bell, The Development of Mathematics (1940)
  • The credit of first using the telescope for astronomical purposes is almost invariably attributed to Galileo, though his first observations were in all probability slightly later in date than those of Harriot and Marius, is to a great extent justified by the persistent way in which he examined object after object, whenever there seemed any reasonable prospect of results following, by the energy and acuteness with which he followed up each clue, by the independence of mind with which he interpreted his observations, and above all by the insight with which he realised their astronomical importance.
    • Arthur Berry, A Short History of Astronomy (1899)
  • His brilliant discoveries the man of science regards as his peculiar property; the means by which they were made, and the development of his intellectual character, belong to the logician and to the philosopher; but the triumphs and the reverses of his eventful life must be claimed for our common nature, as a source of more than ordinary instruction.
    • David Brewster, The Martyrs of Science: Or, The Lives of Galileo, Tycho Brahe, and Kepler (1841) p. 13, (1860 edition).
  • [I]f Bacon had never lived, the student of nature would have found in the writings and labours of Galileo, not only the boasted principles of the inductive philosophy, but also their practical application to the highest efforts of invention and discovery.
    • David Brewster, The Martyrs of Science: Or, The Lives of Galileo, Tycho Brahe, and Kepler (1841) p. 114, (1860 edition).
  • Others before him had asked why heavy bodies fall; now, the homogeneity of the earth with the heavenly bodies having suggested that terrestrial motion is a proper subject for exact mathematical study, we have the further question raised: how do they fall? with the expectation that the answer will be given in mathematical terms.
    • Edwin Arthur Burtt, The Metaphysical Foundations of Modern Physical Science (1925)
  • Copernicus had taken one course in treating the earth as virtually a celestial body in the Aristotelian sense—a perfect sphere governed by the laws which operated in the higher reaches of the skies. Galileo complemented this by taking now the opposite course—rather treating the heavenly bodies as terrestrial ones, regarding the planets as subject to the very laws which applied to balls sliding down inclined planes. There was something in all this which tended to the reduction of the whole universe to uniform physical laws, and it is clear that the world was coming to be more ready to admit such a view.
    • Herbert Butterfield, The Origins of Modern Science (1949)
  • In Santa Croce’s holy precincts lie
    Ashes which make it holier, dust which is
    Even in itself an immortality,
    Though there were nothing save the past, and this,
    The particle of those sublimities
    Which have relapsed to chaos: here repose
    Angelo’s, Alfieri’s bones, and his,
    The starry Galileo, with his woes;
    Here Machiavelli’s earth returned to whence it rose.

    These are four minds, which, like the elements,
    Might furnish forth creation:—Italy!
    Time, which hath wronged thee with ten thousand rents
    Of thine imperial garment, shall deny,
    And hath denied, to every other sky,
    Spirits which soar from ruin: thy decay
    Is still impregnate with divinity,
    Which gilds it with revivifying ray;
    Such as the great of yore Canova is to-day.

    • Lord Byron, Childe Harold’s Pilgrimage, Canto IV (1818) Stanzas 54-55.
  • While Stevin investigated statics, Galileo pursued principally dynamics. Galileo was the first to abandon the Aristotelian idea that bodies descend more quickly in proportion as they are heavier; he established the first law of motion; determined the laws of falling bodies; and, having obtained a clear notion of acceleration and of the independence of different motions, was able to prove that projectiles move in parabolic curves. Up to his time it was believed that a cannon-ball moved forward at first in a straight line and then suddenly fell vertically to the ground. Galileo had an understanding of centrifugal forces, and gave a correct definition of momentum. Though he formulated the fundamental principles of statics, known as the parallelogram of forces, yet he did not fully recognise its scope. The principle of virtual velocities was partly conceived by Guido Ubaldo (died 1607), and afterwards more fully by Galileo.
    • Florian Cajori, A History of Elementary Mathematics (1898)
  • Galileo is the founder of the science of dynamics. Among his contemporaries it was chiefly the novelties he detected in the sky that made him celebrated, but Lagrange claims that his astronomical discoveries required only a telescope and perseverance, while it took an extraordinary genius to discover laws from phenomena, which we see constantly and of which the true explanation escaped all earlier philosophers. The first contributor to the science of mechanics after Galileo was Descartes.
    • Florian Cajori, A History of Elementary Mathematics (1898)
  • It is impossible to exaggerate the effects of his telescopic discoveries on Galileo’s life, so profound were they. Not only is it true of Galileo’s personal life and thought, but it equally true of their influence on the history of scientific thought. 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 against the Ptolemaic, or at least weaken the authority of the ancients. This shattering experience—of observing the depths of the universe, of being the first mortal to know what the heavens are actually like—made so deep a an impression… that it is only by considering the events of 1609… that one can understand the subsequent direction of his life.
    • I. Bernard Cohen, The Birth of a New Physics (1959)
  • It is characteristic of Galileo as a scientist of the modern school that as soon as he found any kind of phenomenon, he wanted to measure it. It is all very well to be told that the telescope discloses that there are mountains on the moon, just as there are mountains on earth. But how much more extraordinary it is, and how much more convincing, to be told that there are mountains on the moon and that they are exactly four miles high! Galileo’s determination of the height of the mountains on the moon has withstood the test of time…
    • I. Bernard Cohen, The Birth of a New Physics (1959)
  • His conflict with the Catholic Church arose because deep in his heart Galileo was a believer. There was for him no path of compromise, no way to have separate secular and theological cosmologies. If the Copernican system was true as he believed, what else could Galileo do but fight with every weapon he had in his arsenal… to make his Church accept a new system of the universe. …In the contrast between Galileo’s heroic stand when he tried to reform the cosmological basis of orthodox theology and his humbled, kneeling surrender when he disavowed his Copernicanism, we may sense the tremendous forces attendant on the birth of modern science. – I. Bernard Cohen, The Birth of a New Physics (1959)
  • The pre-Galilean thinkers were… concerned with motion in the sense used by Aristotle. For them, “motion” was any process in which there was transmission from any state or condition to another state. Thus the process of aging, the change in a person’s degree of wisdom, or the growth in the weight of a boy could all be considered examples of motion. By contrast Galileo was concerned with physical motion, motion involving a change of place… One of the major kinds of motion that Galileo studied was the motion of free fall.
    • I. Bernard Cohen, The Triumph of Numbers: How Counting Shaped Modern Life (2005)
  • In his founding treatise, the Dialogues Concerning Two New Sciences, Galileo boasted that he was setting forth “a very new science dealing with a very ancient subject.” …No one before him, he declared, had discovered that “the distance traversed, during [successive] equal intervals of time, by a body falling from rest, stand to one another in the same ratio as the odd numbers beginning with unity.”
    …Galileo’s rule can be expressed differently, that the total distance fallen is proportional to the square of the total elapsed time.
    …he devised an experiment in which he “diluted” gravity, slowing down the motion of falling. For this purpose he used an inclined plane… He allowed a small metal ball to roll down the board at different inclinations, and recorded the distances and times.
    …Galileo presented the numerical values that he found in his experiments as proof… Thus he could proudly boast of an agreement to within “one-tenth of a pulse beat.”

    • I. Bernard Cohen, The Triumph of Numbers: How Counting Shaped Modern Life (2005)
  • Koyré’s exaltation of the “Platonic and Pythagorean” elements of the Scientific Revolution… was based on a demonstrably false understanding of how Galileo reached his conclusions. Koyré asserted that Galileo merely used experiments as a check on the theories he devised by mathematical reasoning. But later research has definitively established that Galileo’s experiments preceded his attempts to give a mathematical account of their results.
    • Clifford D. Conner, A People’s History of Science (2005)
  • For measurements of time he collected and weighed water flowing from a container at a constant rate of about three fluid ounces per second, He recorded weights of water in grains and, and defined his time unit, called a tempo, to be the time for 16 grains of water to flow, which was equivalent to 1/92 second. These units were small enough so Galileo’s measurements of distance and time always resulted in large numbers. That was a necessity because decimal numbers were not part of his mathematical equipment; the only way he could add significant digits in his calculations was to make the numbers larger.
    • William H. Cropper, Great Physicists (2004)
  • Galileo was the first scientist to recognise clearly that the only way to further our understanding of the physical world was to resort to experiment. …the Greeks, in spite of their proficiency in geometry, never seem to have realised the importance of experiment (Democritus and Archimedes excepted). …an excuse …can scarcely be put forward when the elementary nature of Galileo’s experiments and observations is recalled. Watching a lamp oscillate in the cathedral of Pisa, dropping bodies from the leaning tower of Pisa, rolling balls down inclined planes, noticing the magnifying effect of water in a spherical glass vase… might just as well have been performed by the Greeks.
    • A. D’Abro, The Evolution of Scientific Thought from Newton to Einstein (1927) Forward
  • It is to the Italian astronomer, forced in old age by the Inquisition to turn aside from the more dangerous study of the machinery of the heavens, that we owe the first exposition of many of the problems of mechanics and statics, published… in 1638. Not only did Galileo put together whatever the sixteenth century had learned in the sciences affecting building construction, but from his study of the bending strength of a beam there dates a new branch of science—the theory of the strength of materials.
    • T. K. Derry & Trevor I. Williams, A Short History of Technology: From the Earliest Times to A.D. 1900 (1960) Ch.5, Building Construction, “Building from the Renaissance to the Eighteenth Century”
  • Conclusions obtained by purely rational processes are, so far as Reality is concerned, entirely empty. It was because he recognized this, and especially because he impressed it upon the scientific world that Galileo became the father of modern physics and in fact of the whole of modern natural science.
    • Albert Einstein, “On the Method of Theoretical Physics” (Apr., 1934) in Philosophy of Science, Vol. 1, No. 2, pp. 163-169.
  • It has always hurt me to think that Galileo did not acknowledge the work of Kepler … That, alas, is vanity … You find it in so many scientists.
    • Albert Einstein, in an interview with I. Bernard Cohen, as quoted in Coming of Age in the Milky Way (1988) by Timothy Ferris
  • Galileo was no idiot. Only an idiot could believe that science requires martyrdom — that may be necessary in religion, but in time a scientific result will establish itself.
    • David Hilbert, in defense of Galileo’s recantation of his discoveries before a tribunal of the Inquisition, as quoted in Mathematical Circles Squared : A Third Collection of Mathematical Stories and Anecdotes (1972) by Howard Whitley Eves, p. 125
  • The beginning of astronomy, except observations, I think is not to be derived from farther time than from Nicolaus Copernicus; who in the age next preceding the present revived the opinion of Pythagoras, Aristarchus, and Philolaus. After him, the doctrine of the motion of the earth being now received, and a difficult question thereupon arising concerning the descent of heavy bodies, Galileus in our time, striving with that difficulty, was the first that opened to us the gate of natural philosophy universal, which is the knowledge of the nature of motion. So that neither can the age of natural philosophy be reckoned higher than to him.
    • Thomas Hobbes, The English Works of Thomas Hobbes of Malmesbury (1839) ed. Sir William Molesworth, Vol. 1, p. vii
  • A light was kindled amongst the investigators of nature when Galileo 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. …Thus physics was brought into the position of a certain science after groping about blindly for so many hundred years.
    • Immanuel Kant, Preface, Critique of Pure Reason (1787) 2nd edition, as quoted by J. W. A. Hickson, “Francis Bacon and Galileo Galileo” (A Comparison of Methods) in The McGill University Magazine (Dec. 1905) Vol. 5, No. 1, p. 260, footnote 2.
  • Galileo’s program offers us a dead world: Out go sight, sound, taste, touch, and smell, and along with them have since gone esthetic and ethical sensibility, values, quality, soul, consciousness, spirit. Experience as such is cast out of the realm of scientific discourse. Hardly anything has changed our world more during the past four hundred years than Galileo’s audacious program. We had to destroy the world in theory before we could destroy it in practice.
    • R. D. Laing, as quoted by Fritjof Capra, Uncommon Wisdom (1988)
  • Galileo deduced the laws of freely falling bodies and the parabolic paths of projectiles, initiating an era of applications of mathematics to physics. In his book Two New Sciences, he used indivisible methods to study the motion of a falling body, and he planned, but never wrote, an entire book on indivisibles.
    • Reinhard Labenbacher, David Pengelley, Mathematical Expeditions: Chronicles by the Explorers (1999)
  • The first mathematician to consider the nature of the resistance of solids to rupture was Galileo. Although he treated solids as inelastic, not being in possession of any law connecting the displacements produced with the forces producing them, or of any physical hypothesis capable of yielding such a law, yet his enquiries gave the direction which was subsequently followed by many investigators.
    • Augustus Edward Hough Love, A Treatise on the Mathematical Theory of Elasticity (1906) p. 2.
  • He endeavoured to determine the resistance of a beam, one end of which is built into a wall, when the tendency to break it arises from its own or an applied weight; and he concluded that the beam tends to turn about an axis perpendicular to its length, and in the plane of the wall. This problem, and, in particular, the determination of this axis is known as Galileo’s problem.
    • Augustus Edward Hough Love, A Treatise on the Mathematical Theory of Elasticity (1906) p. 2.
  • Galileo’s comprehension of the concept of acceleration, which he defined as a change of velocity either in magnitude or direction… was an abstract idea that no one seems to have thought much about before. And in using it to test the still accepted Aristotelian precept that a moving object requires a force to maintain it, Galileo easily demonstrated that it is not motion but rather acceleration which cannot occur without an external force. Deliberately rejecting common sense as a prejudiced witness, he let nature herself speak in the form of a “hard, smooth and very round ball” rolling down a “very straight” ideal groove lined with polished parchment, and then rolling up another groove, clocking each roll “hundreds or times”… he showed that, while downward motion (helped by gravity force) makes speed increase and upward motion (hindered by gravity force) makes speed decrease, there is always a “boundary case” in between… where speed remains constant (without any appreciable force)—and that, by reducing friction, this boundary case can be made to approach a horizontal level where gravity has no effect. Similarly testing… he also drafted a law of falling bodies: “that the distances traversed, during equal intervals of time… stand to one another in the same ratio as the odd numbers beginning with unity.” And his beautiful analysis of a cannonball’s trajectory into horizontal and vertical components… was one day to be of enormous help to Isaac Newton in solving the riddle of gravity.
    • Guy Murchie, Music of the Spheres (1961)
  • It was in Galileo’s time that firearms were invented… What is the path of a cannonball? …Characteristically, Galileo was engrossed with then problem; characteristically, he solved it. The outcome of his ingenuity we know today as the method of superposition.
    • George Pólya, Mathematical Methods in Science (1977)
  • How do heavy bodies fall? …Galileo’s investigation of dynamics was physical; Aristotle’s was metaphysical. But unlike Galileo, we have the additional convenience of algebraic notation. Had it been invented in his day he would certainly have known it; almost certainly he would have been able to push his development of dynamics much farther.
    • George Pólya, Mathematical Methods in Science (1977)
  • If Galileo had been willing to face the idea of a plurality of worlds, instead of resting on that of the Sun as the natural “centre of things,” he might have been impelled to develop his system in the Newtonian sense. …The position of the satellites in the Copernican scheme proved the existence of a multiplicity of centers. But the way that led from there was fraught with danger.
    • Giorgio de Santillana, commentary in Galileo’s Dialogue of the Great World Systems (1953)
  • The allusion to the “puzzling” problem of [the orbit of] Mars shows that Galileo ought not to have been unaware of the great work of Kepler published in 1609: Astronomia nova… in which the first two of Kepler’s laws were formulated. Yet he does not mention here at all Kepler’s success in solving the problem, nor his laws, nor his name even, which is brought up… only to criticize his belief in the Moon’s attraction [effect upon tides], which is quite reasonably presented in the Astronomia nova and founded on astronomical reasons and not on mystical speculations.
    • Giorgio de Santillana, commentary in Galileo’s Dialogue of the Great World Systems (1953)
  • To give us the science of motion God and Nature have joined hands and created the intellect of Galileo.
    • Paolo Sarpi, Editor’s Preface to Dialogues and Mathematical Demonstrations Concerning Two New Sciences by Galileo (1638) Crew and De Salvio translation (1914)
  • The old Greek philosophy, which in Europe in the later middle ages was synonymous with the works of Aristotle, considered motion as a thing for which a cause must be found: a velocity required a force to produce and to maintain it. The great discovery of Galileo was that not velocity, but acceleration requires a force. This is the law of inertia of which the real content is: the natural phenomena are described by differential equations of the second order.
    • Willem de Sitter, The Astronomical Aspect of the Theory of Relativity (1933)
  • [T]he mathematical habit of mind and the mathematical procedure… had to be generated; otherwise Newton could never have thought of a formula representing the force between any two masses at any distance. …Throughout the middle ages, under the influence of Aristotle, the science was entirely misconceived. Newton had the advantage of coming after a series of great men, notably Galileo… who in the previous two centuries had reconstructed the science and had invented the right way of thinking about it. He completed their work.
    • Alfred North Whitehead, An Introduction to Mathematics (1911) pp. 29-30.
  • The way in which the persecution of Galileo has been remembered is a tribute to the quiet commencement of the most intimate change in outlook which the human race had yet encountered. Since a babe was born in a manger, it may be doubted whether so great a thing has happened with so little stir.
    • Alfred North Whitehead, Science and the Modern World (1925)
  • The worst that happened to men of science was that Galileo suffered an honorable detention and a mild reproof, before dying peacefully in his bed.
    • Alfred North Whitehead, in The Mathematics Teacher, Vol. 45 (1952), p. 182
  • In Galileo’s time, professors of philosophy and theology—the subjects were inseparable—produced grand discourses on the nature of reality… all based on sophisticated metaphysical arguments. Meanwhile, Galileo measured how fast balls roll down inclined planes. How mundane! But the learned discourses, while grand, were vague. Galileo’s investigations were clear and precise. The old metaphysics never progressed, while Galileo’s work bore abundant, and at length spectacular, fruit. Galileo too cared about the big questions, but he realized that getting the genuine answers requires patience and humility before the facts.
    • Frank Wilczek, The Lightness of Being (2008)
  • Science would not be what it is if there had not been a Galileo, a Newton or a Lavoisier, any more than music would be what it is if Bach, Beethoven and Wagner had never lived. The world as we know it is the product of its geniuses—and there may be evil as well as beneficent genius—and to deny that fact, is to stultify all history, whether it be that of the intellectual or the economic world. – Norman Robert Campbell, What is Science? (1921), 73.

  • It took Galileo 16 years to master the universe. You have one night. It seems unfair. The genius had all that time. While you have a few short hours to learn sun spots from your satellites before the dreaded astronomy exam. On the other hand, Vivarin [caffeine tablets] help you keep awake and mentally alert… So even when the subject matter’s dull, your mind will remain razor sharp. If Galileo had used Vivarin, maybe he could have mastered the solar system faster, too. – Advertisement, Advertisement by Beecham for Vivarin, student newspaper, Columbia Daily Spectator (1 Dec 1988), Vol. 112, No. 186, 5.

  • It seems to me that your Reverence and Signor Galileo act prudently when you content yourselves with speaking hypothetically and not absolutely, as I have always understood that Copernicus spoke. To say that on the supposition of the Earth’s movement and the Sun’s quiescence all the celestial appearances are explained better than by the theory of eccentrics and epicycles is to speak with excellent good sense and to run no risk whatsoever. Such a manner of speaking is enough for a mathematician. But to want to affirm that the Sun, in very truth, is at the center of the universe and only rotates on its axis without going from east to west, is a very dangerous attitude and one calculated not only to arouse all Scholastic philosophers and theologians but also to injure our holy faith by contradicting the Scriptures. – Roberto Bellarmino, Letter to Paolo Antonio Foscarini, 12 April 1615.

  • It is a vulgar belief that our astronomical knowledge dates only from the recent century when it was rescued from the monks who imprisoned Galileo; but Hipparchus … who among other achievements discovered the precession of the eqinoxes, ranks with the Newtons and the Keplers; and Copernicus, the modern father of our celestial science, avows himself, in his famous work, as only the champion of Pythagoras, whose system he enforces and illustrates. Even the most modish schemes of the day on the origin of things, which captivate as much by their novelty as their truth, may find their precursors in ancient sages, and after a careful analysis of the blended elements of imagination and induction which charaterise the new theories, they will be found mainly to rest on the atom of Epicurus and the monad of Thales. Scientific, like spiritual truth, has ever from the beginning been descending from heaven to man. – Benjamin Disraeli, Lothair (1879), preface, xvii.

  • The strangest thing of all is that our ulama these days have divided science into two parts. One they call Muslim science, and one European science. Because of this they forbid others to teach some of the useful sciences. They have not understood that science is that noble thing that has no connection with any nation, and is not distinguished by anything but itself. Rather, everything that is known is known by science, and every nation that becomes renowned becomes renowned through science. Men must be related to science, not science to men. How very strange it is that the Muslims study those sciences that are ascribed to Aristotle with the greatest delight, as if Aristotle were one of the pillars of the Muslims. However, if the discussion relates to Galileo, Newton, and Kepler, they consider them infidels. The father and mother of science is proof, and proof is neither Aristotle nor Galileo. The truth is where there is proof, and those who forbid science and knowledge in the belief that they are safeguarding the Islamic religion are really the enemies of that religion. Lecture on Teaching and Learning (1882). – Sayyid Jamal ad- Din, In Nikki R. Keddie, An Islamic Response to Imperialism (1983), 107.

  • When Galileo caused balls, the weights of which he had himself previously determined, to roll down an inclined plane; when Torricelli made the air carry a weight which he had calculated beforehand to be equal to that of a definite volume of water; or in more recent times, when Stahl changed metal into lime, and lime back into metal, by withdrawing something and then restoring it, a light broke upon all students of nature. They learned that reason has insight only into that which it produces after a plan of its own, and that it must not allow itself to be kept, as it were, in nature’s leading-strings, but must itself show the way with principles of judgement based upon fixed laws, constraining nature to give answer to questions of reason’s own determining. Accidental observations, made in obedience to no previously thought-out plan, can never be made to yield a necessary law, which alone reason is concerned to discover. – Immanuel Kant, Critique of Pure Reason (1781), trans. Norman Kemp Smith (1929), 20.

  • Repudiating the sensible world, which he neither sees himself nor believes from those who have, the Peripatetic joins combat by childish quibbling in a world on paper, and denies the Sun shines because he himself is blind. – Johannes Kepler, Letter to Galileo Galileo (28 Mar 1611). Johannes Kepler Gesammelte Werke (1937- )

  • The stone that Dr. Johnson once kicked to demonstrate the reality of matter has become dissipated in a diffuse distribution of mathematical probabilities. The ladder that Descartes, Galileo, Newton, and Leibniz erected in order to scale the heavens rests upon a continually shifting, unstable foundation. – Morris Kline, Mathematics in Western Culture (1953), 382.

  • What the founders of modern science, among them Galileo, had to do, was not to criticize and to combat certain faulty theories, and to correct or to replace them by better ones. They had to do something quite different. They had to destroy one world and to replace it by another. They had to reshape the framework of our intellect itself, to restate and to reform its concepts, to evolve a new approach to Being, a new concept of knowledge, a new concept of science—and even to replace a pretty natural approach, that of common sense, by another which is not natural at all. – Alexandre Koyré, In ‘Galileo and Plato’, Journal of the History of Ideas (1943), 405.

  • The faith of scientists in the power and truth of mathematics is so implicit that their work has gradually become less and less observation, and more and more calculation. The promiscuous collection and tabulation of data have given way to a process of assigning possible meanings, merely supposed real entities, to mathematical terms, working out the logical results, and then staging certain crucial experiments to check the hypothesis against the actual empirical results. But the facts which are accepted by virtue of these tests are not actually observed at all. With the advance of mathematical technique in physics, the tangible results of experiment have become less and less spectacular; on the other hand, their significance has grown in inverse proportion. The men in the laboratory have departed so far from the old forms of experimentation—typified by Galileo’s weights and Franklin’s kite—that they cannot be said to observe the actual objects of their curiosity at all; instead, they are watching index needles, revolving drums, and sensitive plates. No psychology of ‘association’ of sense-experiences can relate these data to the objects they signify, for in most cases the objects have never been experienced. Observation has become almost entirely indirect; and readings take the place of genuine witness. – Susanne K. Langer, Philosophy in a New Key; A Study in Inverse the Symbolism of Reason, Rite, and Art (1942), 19-20.

  • [W]hen Galileo discovered he could use the tools of mathematics and mechanics to understand the motion of celestial bodies, he felt, in the words of one imminent researcher, that he had learned the language in which God recreated the universe. Today we are learning the language in which God created life. We are gaining ever more awe for the complexity, the beauty, the wonder of God’s most devine and sacred gift. – President Bill Clinton, From White House Announcement of the Completion of the First Survey of the Entire Human Genome Project,

  • [Newton wrote to Halley … that he would not give Hooke any credit] That, alas, is vanity. You find it in so many scientists. You know, it has always hurt me to think that Galileo did not acknowledge the work of Kepler. – Albert Einstein, In I. Bernard Cohen, ‘An Interview with Einstein’, in Anthony Philip French (ed.), Einstein: A Centenary Volume (1979), 41.

  • What Galileo and Newton were to the seventeenth century, Darwin was to the nineteenth. – Bertrand Russell, A History of Western Philosophy (1945), 725.

  • Anthropology found its Galileo in Rivers, its Newton in Mauss. – Claude Lévi-Strauss, Referring to anthropologists W.H.R. Rivers and Marcel Mauss for revolutionizing theories of anthropology.

  • It is impossible not to feel stirred at the thought of the emotions of man at certain historic moments of adventure and discovery—Columbus when he first saw the Western shore, Pizarro when he stared at the Pacific Ocean, Franklin when the electric spark came from the string of his kite, Galileo when he first turned his telescope to the heavens. Such moments are also granted to students in the abstract regions of thought, and high among them must be placed the morning when Descartes lay in bed and invented the method of co-ordinate geometry. – Alfred North Whitehead

  • By night the Glass
    Of Galileo
    observes
    Imagin’d Land and Regions in the Moon. — John Milton

  • There it was that I found and visited the famous Galileo, grown old, a prisner to the inquisition, for thinking in astronomy otherwise than the Franciscan and Dominican licencers thought.

    Recounting the tyranny of the inquisition that Milton had seen for himself in Italy. When he visited in 1640, he was age 30, and Galileo was age 77 and nearly blind. – John Milton

  • When young Galileo, then a student at Pisa, noticed one day during divine service a chandelier swinging backwards and forwards, and convinced himself, by counting his pulse, that the duration of the oscillations was independent of the arc through which it moved, who could know that this discovery would eventually put it in our power, by means of the pendulum, to attain an accuracy in the measurement of time till then deemed impossible, and would enable the storm-tossed seaman in the most distant oceans to determine in what degree of longitude he was sailing?— Hermann von Helmholtz, Hermann von Helmholtz, Edmund Atkinson (trans.)

  • History of science is a relay race, my painter friend. Copernicus took over his flag from Aristarchus, from Cicero, from Plutarch; and Galileo took that flag over from Copernicus. – Mehmet Murat ildan, From the play Galileo Galileo (2001) .

  • It is better to go near the truth and be imprisoned than to stay with the wrong and roam about freely, master Galileo. In fact, getting attached to falsity is terrible slavery, and real freedom is only next to the right. – Mehmet Murat ildan, From the play Galileo Galileo (2001)

  • The way in which the persecution of Galileo has been remembered is a tribute to the quiet commencement of the most intimate change in outlook which the human race had yet encountered. Since a babe was born in a manger, it may be doubted whether so great a thing has happened with so little stir. — Alfred North Whitehead, In Science and the Modern World (1925), 2.

  • After a duration of a thousand years, the power of astrology broke down when, with Copernicus, Kepler, and Galileo, the progress of astronomy overthrew the false hypothesis upon which the entire structure rested, namely the geocentric system of the universe. The fact that the earth revolves in space intervened to upset the complicated play of planetary influences, and the silent stars, related to the unfathomable depths of the sky, no longer made their prophetic voices audible to mankind. Celestial mechanics and spectrum analysis finally robbed them of their mysterious prestige. – Franz Cumont

  • He scarce had ceased when the superior fiend
    Was moving toward the shore; his ponderous shield
    Ethereal temper, massy, large and round,
    Behind him cast; the broad circumference
    Hung on his shoulders like the moon, whose orb
    Through optic glass the Tuscan artist views
    At evening from the top of Fésolè,
    Or in Valdarno, to descry new lands,
    Rivers or mountains in her spotty globe. – John Milton, Paradise Lost, Books I and II (1667),

  • One can truly say that the irresistible progress of natural science since the time of Galileo has made its first halt before the study of the higher parts of the brain, the organ of the most complicated relations of the animal to the external world. And it seems, and not without reason, that now is the really critical moment for natural science; for the brain, in its highest complexity—the human brain—which created and creates natural science, itself becomes the object of this science. – Ivan Petrovich Pavlov, Natural Science and Brain (1909), 120.

  • The pre-Darwinian age had come to be regarded as a Dark Age in which men still believed that the book of Genesis was a standard scientific treatise, and that the only additions to it were Galileo’s demonstration of Leonardo da Vinci’s simple remark that the earth is a moon of the sun, Newton’s theory of gravitation, Sir Humphry Davy’s invention of the safety-lamp, the discovery of electricity, the application of steam to industrial purposes, and the penny post. – George Bernard Shaw, Back to Methuselah: a Metabiological Pentateuch (1921), viii.

  • A man does not attain the status of Galileo merely because he is persecuted; he must also be right. – Stephen Jay Gould, In essay ‘Velikovsky in Collision’, Natural History (Mar 1975),

  • I sometimes think about the tower at Pisa as the first particle accelerator, a (nearly) vertical linear accelerator that Galileo used in his studies. – Leon M. Lederman, In Leon Lederman and Dick Teresi

  • It is in the name of Moses that Bellarmin thunderstrikes Galileo; and this great vulgarizer of the great seeker Copernicus, Galileo, the old man of truth, the magian of the heavens, was reduced to repeating on his knees word for word after the inquisitor this formula of shame: “Corde sincera et fide non ficta abjuro maledico et detestor supradictos errores et hereses.” Falsehood put an ass’s hood on science.
    [With a sincere heart, and of faith unfeigned, I deny by oath, condemn and detest the aforesaid errors and heresies.]— Victor Hugo

  • Science would have us believe that such accuracy, leading to certainty, is the only criterion of knowledge, would make the trial of Galileo the paradigm of the two points of view which aspire to truth, would suggest, that is, that the cardinals represent only superstition and repression, while Galileo represents freedom. But there is another criterion which is systematically neglected in this elevation of science. Man does not now—and will not ever—live by the bread of scientific method alone. He must deal with life and death, with love and cruelty and despair, and so must make conjectures of great importance which may or may not be true and which do not lend themselves to experimentation: It is better to give than to receive; Love thy neighbor as thyself; Better to risk slavery through non-violence than to defend freedom with murder. We must deal with such propositions, must decide whether they are true, whether to believe them, whether to act on them—and scientific method is no help for by their nature these matters lie forever beyond the realm of science. – Allen Wheelis, In The End of the Modern Age (1973), 89.

  • How fortunate for civilization, that Beethoven, Michelangelo, Galileo and Faraday were not required by law to attend schools where their total personalities would have been operated upon to make them learn acceptable ways of participating as members of “the group.”— Joel H. Hildebrand, In speech, ‘Education for Creativity in the Sciences’, Conference at New York University, Washington Square.

  • It is no way derogatory to Newton, or Kepler, or Galileo, that Science in these days should have advanced far beyond them. Rather is this itself their crown of glory. Their works are still bearing fruit, and will continue to do so. The truths which they discovered are still living in our knowledge, pregnant with infinite consequences. – Julius Hare, Co-author with his brother Augustus William Hare Guesses At Truth, By Two Brothers: 

  • I do not personally want to believe that we already know the equations that determine the evolution and fate of the universe; it would make life too dull for me as a scientist. … I hope, and believe, that the Space Telescope might make the Big Bang cosmology appear incorrect to future generations, perhaps somewhat analogous to the way that Galileo’s telescope showed that the earth-centered, Ptolemaic system was inadequate. – John N. Bahcall, From ‘The Space Telescope (the Hubble Space Telescope): 

  • He that knows the secrets of nature with Albertus Magnus, or the motions of the heavens with Galileo, or the cosmography of the moon with Hevelius, or the body of man with Galen, or the nature of diseases with Hippocrates, or the harmonies in melody with Orpheus, or of poesy with Homer, or of grammar with Lilly, or of whatever else with the greatest artist; he is nothing if he knows them merely for talk or idle speculation, or transient and external use. But he that knows them for value, and knows them his own, shall profit infinitely. – Thomas Traherne, In Bertram Doben (ed.), Centuries of Meditations (1908)

  • Galileo was no idiot. Only an idiot could believe that science requires martyrdom—that may be necessary in religion, but in time a scientific result will establish itself. – David Hilbert, As quoted, without citation, in Harold Eves, Mathematical Circles Squared (1971).

  • Simple as the law of gravity now appears, and beautifully in accordance with all the observations of past and of present times, consider what it has cost of intellectual study. Copernicus, Galileo, Kepler, Euler, Lagrange, Laplace, all the great names which have exalted the character of man, by carrying out trains of reasoning unparalleled in every other science; these, and a host of others, each of whom might have been the Newton of another field, have all labored to work out, the consequences which resulted from that single law which he discovered. All that the human mind has produced—the brightest in genius, the most persevering in application, has been lavished on the details of the law of gravity. – Charles Babbage, in The Ninth Bridgewater Treatise: A Fragment (1838), 57.

  • The starry Galileo, with his woes. – Lord George Gordon Byron

  • [In his generation] the worst that happened to men of science was that Galileo suffered an honorable detention and a mild reproof, before dying peacefully in his bed. – Alfred North Whitehead, In ‘The Origins of Modern Science’, Science and the Modern World (1926, 2011), 2.

  • I hardly know of a great physical truth whose universal reception has not been preceded by an epoch in which the most estimable persons have maintained that the phenomena investigated were directly dependent on the Divine Will, and that the attempt to investigate them was not only futile but blasphemous. And there is a wonderful tenacity of life about this sort of opposition to physical science. Crushed and maimed in every battle, it yet seems never to be slain; and after a hundred defeats it is at this day as rampant, though happily not so mischievous, as in the time of Galileo. – Thomas Henry Huxley, In Address (10 Feb 1860) to weekly evening meeting, ‘On Species and Races, and their Origin’

  • That only Galileo’s physical finger is preserved but the descendants of his techniques thrive is also symbolic of the transitoriness of personal existence in contrast to the immortality of knowledge. – Peter William Atkins, In Galileo’s Finger: The Ten Great Ideas of Science (2003), 1.

  • It is, as Schrödinger has remarked, a miracle that in spite of the baffling complexity of the world, certain regularities in the events could be discovered. One such regularity, discovered by Galileo, is that two rocks, dropped at the same time from the same height, reach the ground at the same time. The laws of nature are concerned with such regularities. – Eugene Paul Wigner, In ‘The Unreasonable Effectiveness of Mathematics in the Natural Sciences,’

  • The mechanical speculations of the ancients, particularly of the Greeks, related wholly to statics. Dynamics was founded by Galileo. – Ernst Mach, In The Science of Mechanics (1893), 128.

  • Napoleon and other great men were makers of empires, but these eight men whom I am about to mention were makers of universes and their hands were not stained with the blood of their fellow men. I go back 2,500 years and how many can I count in that period? I can count them on the fingers of my two hands. Pythagoras, Ptolemy, Kepler, Copernicus, Aristotle, Galileo, Newton and Einstein—and I still have two fingers left vacant. – George Bernard Shaw, Speech (28 Oct 1930) at the Savoy Hotel, London

  • Astronomy was not studied by Kepler, Galileo, or Newton for the practical applications which might result from it, but to enlarge the bounds of knowledge, to furnish new objects of thought and contemplation in regard to the universe of which we form a part; yet how remarkable the influence which this science, apparently so far removed from the sphere of our material interests, has exerted on the destinies of the world!— Joseph Henry, In ‘Report of the Secretary’, Annual Report of the Board of Regents of the Smithsonian Institution for 1859 (1860), 15.

  • Marx founded a new science: the science of history. … The sciences we are familiar with have been installed in a number of great “continents”. Before Marx, two such continents had been opened up to scientific knowledge: the continent of Mathematics and the continent of Physics. The first by the Greeks (Thales), the second by Galileo. Marx opened up a third continent to scientific knowledge: the continent of History. – Louis Althusser, In Lenin and Philosophy, and Other Writings (1971), 4.

  • My interest in Science had many roots. Some came from my mother … while I was in my early teens. She fell in love with science,… [from] classes on the Foundations of Physical Science. … I was infected by [her] professor second hand, through hundreds of hours of conversations at my mother’s knees. It was from my mother that I first learned of Archimedes, Leonardo da Vinci, Galileo, Kepler, Newton, and Darwin. We spent hours together collecting single-celled organisms from a local pond and watching them with a microscope. – Richard E. Smalley, From ‘Richard E. Smalley: Biographical’, collected in Tore Frängsmyr (ed.), Les Prix Nobel: The Nobel Prizes 1996 (1997).

  • In the field of thinking, the whole history of science from geocentrism to the Copernican revolution, from the false absolutes of Aristotle’s physics to the relativity of Galileo’s principle of inertia and to Einstein’s theory of relativity, shows that it has taken centuries to liberate us from the systematic errors, from the illusions caused by the immediate point of view as opposed to “decentered” systematic thinking. – Jean Piaget, As quoted in D. E. Berlyne, Structure and Direction in Thinking (1965), 232.

  • A conflict arises when a religious community insists on the absolute truthfulness of all statements recorded in the Bible. This means an intervention on the part of religion into the sphere of science; this is where the struggle of the Church against the doctrines of Galileo and Darwin belongs. On the other hand, representatives of science have often made an attempt to arrive at fundamental judgments with respect to values and ends on the basis of scientific method, and in this way have set themselves in opposition to religion. These conflicts have all sprung from fatal errors. – Albert Einstein

  • We debase the richness of both nature and our own minds if we view the great pageant of our intellectual history as a compendium of new in formation leading from primal superstition to final exactitude. We know that the sun is hub of our little corner of the universe, and that ties of genealogy connect all living things on our planet, because these theories assemble and explain so much otherwise disparate and unrelated information–not because Galileo trained his telescope on the moons of Jupiter or because Darwin took a ride on a Galápagos tortoise. – Stephen Jay Gould

  • It is a good principle in science not to believe any “fact”—however well attested—until it fits into some accepted frame of reference. Occasionally, of course, an observation can shatter the frame and force the construction of a new one, but that is extremely rare. Galileos and Einsteins seldom appear more than once per century, which is just as well for the equanimity of mankind. – Arthur C. Clarke

  • Today, everybody remembers Galileo. How many can name the bishops and professors who refused to look through his telescope?— James P. Hogan

  • “Wu Li” was more than poetic. It was the best definition of physics that the conference would produce. It caught that certain something, that living quality that we were seeking to express in a book, that thing without which physics becomes sterile. “Wu” can mean either “matter” or “energy.” “Li” is a richly poetic word. It means “universal order” or “universal law.” It also means “organic patterns.” The grain in a panel of wood is Li. The organic pattern on the surface of a leaf is also Li, and so is the texture of a rose petal. In short, Wu Li, the Chinese word for physics, means “patterns of organic energy” (“matter/ energy” [Wu] + “universal order/organic patterns” [Li]). This is remarkable since it reflects a world view which the founders of western science (Galileo and Newton) simply did not comprehend, but toward which virtually every physical theory of import in the twentieth century is pointing!— Gary Zukav, In The Dancing Wu Li Masters: An Overview of the New Physics (1979), 5.

  • Galileo … asserts that in all these phenomena we must measure all that is measurable, and try to make measurable all that is not directly measurable. – Thomas-Henri Martin

  • True physics was founded the day when Galileo, rejecting fruitless speculations, conceived the idea … of defining the general form to give to experiments, by assigning for their immediate purpose the measure of all that can be measurable in natural phenomena. – Antoine-Augustin Cournot

  • At the bidding of a Peter the Hermit many millions of men swarmed to the East; the words of an hallucinated person … have created the force necessary to triumph over the Graeco-Roman world; an obscure monk like Luther set Europe ablaze and bathed in blood. The voice of a Galileo or a Newton will never have the least echo among the masses. The inventors of genius transform a civilization. The fanatics and the hallucinated create history. – Gustave Le Bon, From Les Premières Civilisations (1889), 171. English in The Psychology of Peoples (1898)

  • Having probes in space was like having a cataract removed. We could see things never seen before, just as Galileo could with his telescope. – Hannes Alfvén, Quoted, without citation, in Eric Lerner, The Big Bang Never Happened:

  • In the index to the six hundred odd pages of Arnold Toynbee’s A Study of History, abridged version, the names of Copernicus, Galileo, Descartes and Newton do not occur yet their cosmic quest destroyed the medieval vision of an immutable social order in a walled-in universe and transformed the European landscape, society, culture, habits and general outlook, as thoroughly as if a new species had arisen on this planet. – Arthur Koestler, In The Sleepwalkers: A History of Man’s Changing Vision of the Universe (1959), Preface, 13.

  • The tool which serves as intermediary between theory and practice, between thought and observation, is mathematics; it is mathematics which builds the linking bridges and gives the ever more reliable forms. From this it has come about that our entire contemporary culture, inasmuch as it is based on the intellectual penetration and the exploitation of nature, has its foundations in mathematics. Already Galileo said: one can understand nature only when one has learned the language and the signs in which it speaks to us; but this language is mathematics and these signs are mathematical figures. – David Hilbert, Radio broadcast (8 Sep 1930).

  • Children are told that an apple fell on Isaac Newton’s head and he was led to state the law of gravity. This, of course, is pure foolishness. What Newton discovered was that any two particles in the universe attract each other with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them. This is not learned from a falling apple, but by observing quantities of data and developing a mathematical theory that can be verified by additional data. Data gathered by Galileo on falling bodies and by Johannes Kepler on motions of the planets were invaluable aids to Newton. Unfortunately, such false impressions about science are not universally outgrown like the Santa Claus myth, and some people who don’t study much science go to their graves thinking that the human race took until the mid-seventeenth century to notice that objects fall. – Robert (Bob) Hooke, In How to Tell the Liars from the Statisticians (1983), 127.

  • Our federal income tax law defines the tax y to be paid in terms of the income x; it does so in a clumsy enough way by pasting several linear functions together, each valid in another interval or bracket of income. An archaeologist who, five thousand years from now, shall unearth some of our income tax returns together with relics of engineering works and mathematical books, will probably date them a couple of centuries earlier, certainly before Galileo and Vieta. – Hermann Weyl, From Address (1940), given at the Bicentennial Conference at the University of Pennsylvania,

  • There is something sublime in the secrecy in which the really great deeds of the mathematician are done. No popular applause follows the act; neither contemporary nor succeeding generations of the people understand it. The geometer must be tried by his peers, and those who truly deserve the title of geometer or analyst have usually been unable to find so many as twelve living peers to form a jury. Archimedes so far outstripped his competitors in the race, that more than a thousand years elapsed before any man appeared, able to sit in judgment on his work, and to say how far he had really gone. And in judging of those men whose names are worthy of being mentioned in connection with his,—Galileo, Descartes, Leibnitz, Newton, and the mathematicians created by Leibnitz and Newton’s calculus,—we are forced to depend upon their testimony of one another. They are too far above our reach for us to judge of them. – Thomas Hill, In ‘Imagination in Mathematics’, North American Review, 86, 223.

  • We pass with admiration along the great series of mathematicians, by whom the science of theoretical mechanics has been cultivated, from the time of Newton to our own. There is no group of men of science whose fame is higher or brighter. The great discoveries of Copernicus, Galileo, Newton, had fixed all eyes on those portions of human knowledge on which their successors employed their labors. The certainty belonging to this line of speculation seemed to elevate mathematicians above the students of other subjects; and the beauty of mathematical relations and the subtlety of intellect which may be shown in dealing with them, were fitted to win unbounded applause. The successors of Newton and the Bernoullis, as Euler, Clairaut, D’Alembert, Lagrange, Laplace, not to introduce living names, have been some of the most remarkable men of talent which the world has seen. – William Whewell, In History of the Inductive Sciences, Vol. 1, Bk. 4, chap. 6, sect. 6.

  • He [Lord Bacon] appears to have been utterly ignorant of the discoveries which had just been made by Kepler’s calculations … he does not say a word about Napier’s Logarithms, which had been published only nine years before and reprinted more than once in the interval. He complained that no considerable advance had been made in Geometry beyond Euclid, without taking any notice of what had been done by Archimedes and Apollonius. He saw the importance of determining accurately the specific gravities of different substances, and himself attempted to form a table of them by a rude process of his own, without knowing of the more scientific though still imperfect methods previously employed by Archimedes, Ghetaldus and Porta. He speaks of the εὕρηκα of Archimedes in a manner which implies that he did not clearly appreciate either the problem to be solved or the principles upon which the solution depended. In reviewing the progress of Mechanics, he makes no mention either of Archimedes, or Stevinus, Galileo, Guldinus, or Ghetaldus. He makes no allusion to the theory of Equilibrium. He observes that a ball of one pound weight will fall nearly as fast through the air as a ball of two, without alluding to the theory of acceleration of falling bodies, which had been made known by Galileo more than thirty years before. He proposed an inquiry with regard to the lever,—namely, whether in a balance with arms of different length but equal weight the distance from the fulcrum has any effect upon the inclination—though the theory of the lever was as well understood in his own time as it is now. … He speaks of the poles of the earth as fixed, in a manner which seems to imply that he was not acquainted with the precession of the equinoxes; and in another place, of the north pole being above and the south pole below, as a reason why in our hemisphere the north winds predominate over the south. – Frank Harold Spedding, From Spedding’s ‘Preface’ to De Interpretations Naturae Proœmium, in The Works of Francis Bacon (1857), Vol. 3, 511-512. [Note: the Greek word “εὕρηκα” is “Eureka” —Webmaster.]

  • The pioneering practitioners of the new science [of the seventeenth century] knew that they were producing a new kind of knowledge and so they declared this newness in the titles of their books and articles. Thus we have Galileo’s Two New Sciences, Boyle’s New Experiments, Kepler’s New Astronomy, and Tartaglia’s New Science. – I. Bernard Cohen, From The Triumph of Numbers: How Counting Shaped Modern Life (2005), 36.

  • When Ben Jonson presented a masque entitled “News from the New World,” his new world was not the newly found continent of North America, but the new world of science, the world revealed by the telescope of Galileo. – I. Bernard Cohen, From The Triumph of Numbers: How Counting Shaped Modern Life (2005), 36.

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