On March 14, we celebrated Pi Day — a global observance of the importance of math and the world’s most famous mathematical constant. We’ve rounded up just a few of the most interesting stories on topics that range from a group of detractors who mark “Tau Day” to examining Pi and mathematical notions of beauty, and from identifying hidden patterns to looking at how a farm boy from Wales gave the world Pi, as well as a discussion on how Pi seems to crop up in lots of unexpected places and an update on the ongoing search for the exact value of Pi.

**The Search for the Value of Pi **

The number represented by pi is used in calculations whenever something round (or nearly so) is involved, such as for circles, spheres, cylinders, cones and ellipses. Our world contains many round and near-round objects; finding the exact value of pi helps us build, manufacture and work with them more accurately. The search for the accurate value of pi led not only to more accuracy, but also to development of new concepts and techniques.

**Pi Pops Up Where You Don’t Expect It **

The exact value of π=3.14159… has fascinated people since ancient times, and mathematicians have computed *trillions* of digits. But why do we care? Would it actually matter if somebody got the 11,137,423,895,285th digit wrong? Probably not. The world would keep on turning (with a circumference of 2πr). What matters isn’t so much the actual value as the *idea*, and the fact that it seems to crop up in lots of unexpected places.

**How a Farm Boy from Wales Gave the World Pi **

One of the most important numbers in maths might today be named after the Greek letter π or “pi,” but the convention of representing it this way actually doesn’t come from Greece at all. It comes from the pen of an 18th century farmer’s son and largely self-taught mathematician from the small island of Anglesey in Wales. The Welsh Government has even renamed Pi Day as “Pi Day Cymru.”

**Pi Might Look Random, but It’s Full of Hidden Patterns **

After thousands of years of trying, mathematicians are still working out the number known as pi or “π.” We typically think of pi as approximately 3.14 but the most successful attempt to calculate it more precisely worked out its value to over 13 trillion digits after the decimal point. We have known since the 18th century that we will never be able to calculate all the digits of pi because it is an irrational number.

**Pi and Its Part of the Most Beautiful Formula in Mathematics **

Pi Day is upon us again, for those who note today’s date in the format 3/14 (March 14). But rather than talk about Pi Day itself, as I did last year, this year I want to talk about Pi and mathematical notions of beauty. How better to do so than to talk about the 18th century European scholar Leonard Euler’s famous formula…

**10 Ways to Celebrate Pi Day 2016**

After last year’s ultimate Pi Day when, on 3.14.15 at 9:26:53, the date and time corresponded to the first 10 digits of the mathematical constant pi (π = 3.141592653), I wondered what the annual celebration might look like this year — would it be possible to top an event that happens only once per century?

**New Derivation of Pi Links Quantum Physics and Pure Math**

In 1655, the English mathematician John Wallis published a book in which he derived a formula for pi as the product of an infinite series of ratios. In a surprise discovery, researchers have found the same formula in quantum mechanical calculations of the energy levels of a hydrogen atom. A purely mathematical formula from the 17th century characterizes a physical system discovered 300 years later.

**Are you a Tau-ist? Pi Day is Under Attack**

As June 28, 2015, approaches, the Internet is once again anticipating controversy as the mathematical constant pi comes under threat from a group of detractors who will be marking “Tau Day.” Tau Day’s revelers are campaigning for a constant twice as large as pi (about 6.28) to take its place, hence the June 28 celebration. Tau proponents say that, for many mathematical problems, tau makes more sense and makes calculations easier.

**Once-in-a-Century: Celebrating 10 Digits of Pi on 3.14.15 at 9:26:53**

An e-pi-c day is coming! On 3.14.15 at 9:26:53; the date/time will correspond to the first 10 digits of the mathematical constant pi (3.141592653). This happens only once per century — a truly once-in-a-lifetime event for most people.

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