We Regard It As A

Yet The Widespread Planetary Theories, Advanced By Ptolemy And Most Other Astronomers, Although Consistent With The Numerical Data, Seemed Likewise To Present No Small Difficulty. For These Theories Were Not Adequate Unless They Also Conceived Certain Equalizing Circles, Which Made The Planet Appear To Move At All Times With Uniform Velocity Neither On Its Deferent Sphere Nor About Its Own Epicycle's Center.

For What Could Be More Beautiful Than The Heavens Which Contain All Beautiful Things.

For When A Ship Is Floating Calmly Along, The Sailors See Its Motion Mirrored In Everything Outside, While On The Other Hand They Suppose That They Are Stationary, Together With Everything On Board. In The Same Way, The Motion Of The Earth Can Unquestionably Produce The Impression That The Entire Universe Is Rotating.

The Earth Together With Its Surrounding Waters Must In Fact Have Such A Shape As Its Shadow Reveals, For It Eclipses The Moon With The Arc Of A Perfect Circle.

Therefore, In The Course Of The Work I Have Followed This Plan: I Describe In The First Book All The Positions Of The Orbits Together With The Movements Which I Ascribe To The Earth, In Order That This Book Might Contain, As It Were, The General Scheme Of The Universe.