Isaac Newton · every age

What was Isaac Newton doing at 55?

Invented calculus and gravity theory in a plague year at 23

1. Jun 1698

   Began interrogating counterfeiters for the Mint

   More than 100 cross-examinations by Christmas 1699.

   Source: en.wikipedia.org

Portrait: Portrait: Godfrey Kneller (1689), public domain, via Wikimedia Commons · source