[jfengel]

As other replies have said, the math is kind of important. The idea of a tattoo harkens to the story of the discovery of quaternions: Rowan Hamilton was out for a walk in Dublin, trying to figure out how to generalize complex numbers. He was walking under a bridge when he came up with that equation, and carved the equation on the bridge.

His carving, if it ever existed, is gone. But there is a plaque on the bridge commemorating the event. It reads:

Here as he walked by on the 16th of October 1843 Sir William Rowan Hamilton in a flash of genius discovered the fundamental formula for quaternion multiplication i² = j² = k² = ijk = −1 & cut it on a stone of this bridge.

[GlenTheMachine]

My PhD advisor was a stickler for citing original sources. Really, really original sources. He made me cite some papers written by Lagrange in the 17th century in French, when neither he nor I nor nearly anyone else who would ever read my dissertation could speak French.

I got to the point where I needed to cite an original source for the quaternion equations, so I cited the bridge.

He got the message.

[kens]

For a summary of William Rowan Hamilton's life (including the bridge story), see this amazingly clever video based on the song from Hamilton: https://www.youtube.com/watch?v=SZXHoWwBcDc

[chadcmulligan]

There's also a great book "A History of Vector Analysis: The Evolution of the Idea of a Vectorial System" by Crowe which covers vectors from Complex numbers to Gibbs vectors and includes Hamilton and the competitor at the time Grassman Algebra, both the basis for geometric algebra.

Its one of the only maths history books I couldn't put down.

[pflats]

Thanks for writing this. It was indeed a large part of why I like it. I added more detail in a reply to the parent post.

https://news.ycombinator.com/item?id=22204995