Galileo Galilei quotes

Galileo Galilei was an Italian astronomer, physicist, and engineer, often called the "father of modern science." His groundbreaking observations with the telescope transformed humanity’s view of the universe. He challenged conventional beliefs and laid the foundations for modern physics and astronomy. Here are 96 of his quotes:

You cannot teach a man anything, you can only help him to find it within himself.

Galileo Galilei

Mathematics is the key and door to the sciences.

Galileo Galilei

I have never met a man so ignorant that I could not learn something from him.

Galileo Galilei

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

Galileo Galilei

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.

Galileo Galilei

Measure what can be measured, and make measureable what cannot be measured.

Galileo Galilei

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 Galilei

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.

Galileo Galilei

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

Galileo Galilei

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

Galileo Galilei

By denying scientific principles, one may maintain any paradox.

Galileo Galilei

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 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

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

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 Galilei

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 Galilei

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 Galilei

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 Galilei

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."

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

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...

Galileo Galilei

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.

Galileo Galilei