Happy pi day! Today we think of pi as the ratio of a circle's circumference to its diameter (3.14...). But in the olden days (and even today) some people thought pi should be the ratio of a circle's radius to its diameter (6.28...), Today, that symbol is called tau, and in some cases, it makes for cleaner looking equations. 3Blue1Brown made a fun video about the "seminal moments when pi became the standard."
Another reason to celebrate pi day - the Raspberry Pi Foundation announced the release of the Raspberry Pi 3 Model B+, a significant update to the amazing little $35 Linux computer: https://www.youtube.com/watch?v=zQZxdiz2UAs
