Leonhard Euler was an 18th-century Swiss-born mathematician who developed many concepts that are integral to modern mathematics. He spent most of his career in St. Petersburg, Russia.

But Euler's constant shows up pretty much everywhere. It's in all sorts of mathematical equations, like integrals and transforms. It even shows up in a few quantum mechanics equations.

Just as he was unfazed by blindness, Euler did not let these troubles hinder his mathematical creativity. In his treatment of infinitesimals — used in differential and integral calculus and in ...