## Fr. Grienberger the Astronomer, and his Homemade Pi

Today is “Pi Day”! This post is part of a series of posts on Pi, infinity, and other things mathematical. Click here for the series. What is Pi (π)? We celebrate “Pi Day” on March 14 (3/14). That is because Pi is (roughly) 3.14. Indeed, I scheduled this post to appear at 1:59 AM, because Pi is (a little less roughly) 3.14159! How nerdy can a guy get? So Pi is a mathematical idea that has its own day. That is good, because astronomy involves a lot of mathematical ideas. But still, what is Pi, and how do we know what it is? This question started bugging me after I bought my previous laptop. For some reason the calculator “app” on this laptop was striking in a way that older calculator apps were not. Perhaps this is because the new app was large and bold. But at any rate, note how the button for π (that is, Pi) on the … Continue reading →