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

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

Mathematics is the key and door to the sciences.

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.

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

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

The deeper I go in considering the vanities of popular reasoning, the lighter and more foolish I find them.

Passion is the genesis of genius.

Earth, turning upon itself, moves round the Sun.

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

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

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

Two truths cannot contradict one another.

I am certainly interested in a tribunal in which, for having used my reason, I was deemed little less than a heretic.

In time you may discover everything that can be discovered, and still your progress will only be progress away from humanity.

That sculpture is more admirable than painting for the reason that it contains relief and painting does not is completely false.

Nothing can be more destructive to ambition, and the passion for conquest, than the true system of astronomy. What a poor thing is even the whole globe in comparison of the infinite extent of nature!

As astronomy is the daughter of idleness, geometry is the daughter of property.

Philosophy begins where religion ends, just as by analogy chemistry begins where alchemy runs out, and astronomy takes the place of astrology.

Everybody knows what the moon is, everybody knows what this decade is, and everybody can tell a live astronaut who returned from the moon from one who didn’t.

I only hope that we shall not wait to adopt the program until after our astronomers have reported a new and unsuspected asteroid moving across their fields of vision with menacing speed. At that point it will be too late!

For it is the duty of an astronomer to compose the history of the celestial motions through careful and expert study.

Somewhere, something incredible is waiting to be known.