Department of Energy

# Celebrating Pi Day

March 14, 2013

## You are here

A mathematical formula discovered a decade ago in part by David H. Bailey (above), the Chief Technologist of the Computational Research Department at the Lawrence Berkeley National Laboratory, was the basis for researchers to find the sixty-trillionth binary digit of Pi-squared. | Photo Courtesy of Lawrence Berkely National Lab

You might recognize the date March 14 (in the format 3/14) as a number from classes long forgotten. But even for the not-so-math-conscious, 3.14(...) is a number universally recognized – and celebrated on this day of Pi (and pie).

As a quick refresher, you would multiply Pi by the diameter of any circle to get the circumference. Though as vital as Pi might be to architecture and engineering, it’s really one of the mysterious numbers in mathematics.

Let’s take a look at Pi as a number:  It’s irrational, which means it can’t be expressed as a simple fraction. It’s transcendental, which means it is not a root of a non-zero polynomial equation with rational coefficients.

Pi is also uncountably infinite, meaning it goes on forever, which, along with its homonym to the delicious baked good, may lend itself to its popularity. As of 2011, supercomputers cracked the sixty-trillionth binary digit of pi-squared. To put this into perspective, a value of Pi to 40 digits would be more than enough to compute the circumference of the Milky Way galaxy to an error less than the size of a proton.

The importance of Pi has long been known. Ancient Egyptians used this number in their design of the pyramids. Ancient scholars in Jerusalem, India, Babylon, Greece and China used this proportions in their studies of architecture and symbols.

More recently, Pi has been used in machining parts, broadcasting radio signals, simulating load conditions, and even testing supercomputers. The digits of Pi are used to test the integrity of computer hardware and software. Researchers check the computations of Pi by a new computer against the known digits to ensure new machinery is working appropriately.

Still it seems humanity may never have anything but approximations of Pi. In the meantime, let us celebrate Pi Day with talk of the irrational number and its baked homophone.