The Earth is round, and is inhabited on all sides, is insignificantly small, and is borne through the stars.

I used to measure the Heavens, now I measure the shadows of Earth. The mind belonged to Heaven, the body's shadow lies here.

O telescope, instrument of much knowledge, more precious than any sceptre!

Since we astronomers are priests of the highest God in regard to the book of nature, it befits us to be thoughtful, not of the glory of our minds, but rather, above all else, of the glory of God.

As soon as somebody demonstrates the art of flying, settlers from our species of man will not be lacking on the Moon and Jupiter. Who would have believed that a huge ocean could be crossed more peacefully and safely than the the narrow expanse of the Adriatic, the Baltic Sea or the English Channel? Given ships or sails adapted to the breezes of heaven, there will be those who will not shrink from even that vast expanse.

I measured the skies, now the shadows I measure, Sky-bound was the mind, earth-bound the body rests. [Kepler's epitaph]

In theology we must consider the predominance of authority; in philosophy the predominance of reason.