Galileo Galilei

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.

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

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

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.

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.

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!

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.

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.

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.

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

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

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

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

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 judgment upon anything new.

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

Wine is sunlight, held together by water.

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.)

Mathematics is the key and door to the sciences.

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.

Measure what is measurable, and make measurable what is not so.

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