Exactly how did Newton deal with his planets? (Q1361140)

This article describes exactly how Newton dealt with the problem of planetary orbits in his Principia. Presenting Newton's methodology, as based exclusively on geometry and limits, in a way easy for a 20th-century reader to follow, the author reaches the following significant conclusion: `There is absolutely no evidence that Newton first used his calculus, developed some 20 years before he wrote the Principia, to treat these problems and then recast his work in the geometric terms'.