Mathematics Is Written For Mathematicians.

Pouring Forth Its Seas Everywhere, Then, The Ocean Envelops The Earth And Fills Its Deeper Chasms.

So If The Worth Of The Arts Were Measured By The Matter With Which They Deal, This Art-which Some Call Astronomy, Others Astrology, And Many Of The Ancients The Consummation Of Mathematics-would Be By Far The Most Outstanding. This Art Which Is As It Were The Head Of All The Liberal Arts And The One Most Worthy Of A Free Man Leans Upon Nearly All The Other Branches Of Mathe Matics. Arithmetic, Geometry, Optics, Geodesy, Mechanics, And Whatever Others, All Offer Themselves In Its Service.

The Scorn Which I Had Reason To Fear On Account Of The Novelty And Unconventionality Of My Opinion Almost Induced Me To Abandon Completely The Work Which I Had Undertaken. . . . Astronomy Is Written For Astronomers. To Them My Work Too Will Seem, Unless I Am Mistaken, To Make Some Contribution.

Since, Then, There Is No Objection To The Mobility Of The Earth, I Think It Must Now Be Considered Whether Several Motions Are Appropriate For It, So That It Can Be Regarded As One Of The Wandering Stars. For The Fact That It Is Not The Centre Of All Revolutions Is Made Clear By The Apparent Irregular Motion Of The Wandering Stars, And Their Variable Distances From The Earth, Which Cannot Be Understood In A Circle Having The Same Centre As The Earth.

In First Place We Must Observe That The Universe Is Spherical. This Is Either Because That Figure Is The Most Perfect, As Not Being Articulated, But Whole And Complete In Itself; Or Because It Is The Most Capacious And Therefore Best Suited For That Which Is To Contain And Preserve All Things.