Galileo Galilei Quotes & Sayings

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

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 Galilei

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

Nothing can be taught to a man, only it's possibly to help him to discover it inside. — Galileo Galilei

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 Galilei

Scripture is a book about going to Heaven. It's not a book about how the heavens go. — Galileo Galilei

I have never met a man so ignorant that I couldn't learn something from him. — Galileo Galilei

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

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

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

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

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 Galilei

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 Galilei

Nature's great book is written in mathematics. — Galileo Galilei

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 Galilei

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 Galilei

And yet it moves. — Galileo Galilei

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 Galilei

What ever the course of our lives, we should recieve 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 Galilei

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 Galilei

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 Galilei

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 Galilei

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 Galilei

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 Galilei

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 Galilei

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 Galilei

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 Galilei

To be humane, we must ever be ready to pronounce that wise, ingenious and modest statement 'I do not know'. — Galileo Galilei

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 Galilei

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 Galilei

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 Galilei

To understand the Universe, you must understand the language in which it's written, the language of Mathematics. — Galileo Galilei

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

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

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 Galilei

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 Galilei

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 Galilei

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 Galilei

[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 Galilei

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 Galilei

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 Galilei

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 Galilei

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

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

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 Galilei

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

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 Galilei

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 Galilei

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 Galilei

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 Galilei

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

Wine is sunlight, held together by water. — Galileo Galilei

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 Galilei

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

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

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

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

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 fellow revolutionary astronomer Johannes Kepelr} — Galileo Galilei

Nature is written in mathematical language. — Galileo Galilei

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

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

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 Galilei

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

You can't teach anybody anything, only make them realize the answers are already inside them. — Galileo Galilei

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 Galilei

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

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 Galilei

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 Galilei

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 Galilei

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

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 Galilei

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 Galilei

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. — Galileo Galilei

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 Galilei

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 Galilei

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

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 Galilei

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

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 Galilei

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 Galilei

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 methematical figures. — Galileo Galilei

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 Galilei

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 Galilei

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 Galilei

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

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 Galilei

The greatest wisdom is to get to know oneself. — Galileo Galilei

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 Galilei

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 Galilei

(T)he increase of known truths stimulates the investigation, establishment, and growth of the arts. — Galileo Galilei

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 Galilei

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 Galilei

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 Galilei

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 Galilei

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

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 Galilei

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 Galilei

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

Measure what is measurable, and make measurable what is not so. — Galileo Galilei

Passion is the genesis of genius. — Galileo Galilei