It reveals to me the causes of many natural phenomena that are entirely incomprehensible in the light of the generally accepted hypotheses. To refute the latter I collected many proofs, but I do not publish them ... I would dare to publish my speculations if there were people men like you.

I do not know what to say in a case so surprising, so unlooked for and so novel.

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

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

Philosophy itself cannot but benefit from our disputes, for if our conceptions prove true, new achievements will be made; if false, their refutation will further confirm the original doctrines.

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?

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