I much prefer the sharpest criticism of a single intelligent man to the thoughtless approval of the masses.

There will certainly be no lack of human pioneers when we have mastered the art of flight....Let us create vessels and sails justed to the heavenly ether, and there will be plenty of people unafraid of the empty wastes. In the meantime we shall prepare, for the brave sky-travelers, maps of the celestial bodies.

I am a Lutheran astrologer, I throw away the nonsense and keep the hard kernel.

The moon... is a mass, akin to the mass of the earth, attracts the waters by a magnetic force, not because they are liquid, but because they possess earthy substance, and so share in the movements of a heavy body.

Truth is the daughter of time, and I feel no shame in being her midwife.

We do not ask for what useful purpose the birds do sing, for song is their pleasure since they were created for singing. Similarly, we ought not to ask why the human mind troubles to fathom the secrets of the heavens.

I also ask you my friends not to condemn me entirely to the mill of mathematical calculations, and allow me time for philosophical speculations, my only pleasures.