Is there a good Modern English translation of Newton's "Philosophiæ Naturalis Principia Mathematica" available for free viewing or download? I have found several nice versions available for purchase, but all of the free ones are either Latin, old English, or pixellated. I searched google and was only able to locate the free ones linked to from the Wikipedia page on Philosophiæ Naturalis Principia Mathematica. 
 A: You overestimate the amount of evolution that the English language has undergone in the last 300 years. I recommend you the perfectly readable English translation by my great great grand uncle Motte, as revised by Cajori:

http://books.google.com/books?id=ySYULc7VEwsC&printsec=frontcover&hl=en&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

Let me just be a linguist for a while. ;-) Modern English has existed since 1550

http://en.wikipedia.org/wiki/Modern_english

when the Great Vowel Shift took place, so not only Motte's 1729 translation linked above is written in Modern English but Isaac Newton was speaking Modern English throughout his life, too. Of course, Newton would write in Latin.
A: The first American edition (New York, Daniel Adee, call number QA803.A4 1846), translated by Andrew Motte, is available at the Internet Archive at

https://archive.org/details/100878576.

It is available in ePub, Kindle, Daisy and DjVu (30.5 MB) formats, as well as for online viewing in a dedicated viewer.
