We made it through the “Pi Day of the century” on Saturday. I took a spontaneous day trip to meet friends in Idaho, so I didn’t do any pi-related activities, but I saw plenty of pi coverage in the week leading up to the big day.

Like many mathematicians, I’m pretty lukewarm about Pi Day. I’m generally a scrooge about most holidays, but I do appreciate the fact that Pi Day has given me a chance to write about some cool math topics I probably wouldn’t have otherwise. Last year I wrote about π(x), the prime counting function, and this year, I wrote about continued fractions, which get cooler every time I learn more about them. (I can’t help but brag about the fact that Mike Lawler did some continued fractions with his kids after reading my post. I love seeing my work in action!)

Of course, there were quite a lot of nice Pi Day posts around the math blogsphere this year. Pat Ballew wrote about pi and the Kruskal count, a fun mathemagic trick. JoAnne Growney posted at at her math poetry blog about Pilish, the “language” whose word lengths follow the digits of pi. Alex Bellos wrote a short post in Pilish for the Aperiodical. Dick Lipton and Ken Regan took the opportunity to discuss another pi: products. Specifically, how much does integer multiplication cost? Rafael Irizarry wrote about empirical evidence that pi is a normal number for Simply Statistics

The Aperiodical pulled out all the stops for Pi Day. If I counted correctly, they posted 15 articles about pi this past week. I especially enjoyed their first one, a video of mathematicians using various methods, from measuring the period of a pendulum to filling water balloons, to estimate pi. I also appreciated Katie Steckles’ rumination on the appropriate time to celebrate pi in several different timekeeping systems. Aperiodical contributor Christian Perfect bought the domain three.onefouronefivenine.com, where you can scroll down and see lots and lots of digits of pi.

Education-focused blogs Math Munch, Let’s Play Math, and Moebius Noodles used the occasion to publish fun, accessible posts about pi. Stuart Price, inspired by Joshua Bowman, wrote about π-th roots of unity, which relate quite nicely to continued fractions. Mike Lawler also used that activity with his kids.

I understand why math bloggers write about Pi for Pi Day, and they write a lot of neat stuff. General interest news media, however, can get weird about it. On the one hand, it is nice for math to get a little bit more focus than it usually does. On the other hand, the stories often divide the world into “us” and “them”: regular folks and freaks who like reciting numbers. Is there really no such thing as bad publicity? As Dan Meyer said on Twitter,

@lodish Publicity that promotes an image of math as obsessed with cryptic numerology and obscure rituals is bad publicity. My opinion.

— Dan Meyer (@ddmeyer) March 13, 2015

Some big media outlets did pretty well on Pi Day. Phil Plait wrote a fun piece for Slate, Alex Bellos wrote a few nice posts for the Guardian, including one about the first person to use the letter π for circles, and Manil Suri wrote an op-ed in the New York Times. Gary Antonick wrote a very nice post for the New York Times Wordplay blog. He focused on Euler’s identity and included an excellent new-to-me video explaining how exponentiation works when you start messing around with complex exponents.

Daniel Ullman wrote a good article for the Conversation that includes the fantastic tongue-in-cheek suggestion to celebrate Earth Day by eating foods that start with the letter ‘e’. Or, of course, we could do that to celebrate *e* Day on February 7th (2/7 for the US and Belize), July 2nd (2/7 for most of the world), or September 28 (the 271st day of the year in non-leap years, 272nd in leap years—either would be appropriate as *e* starts 2.718). Steven Strogatz wrote a lovely article about the Pi Day dilemma for the New Yorker. Pi is an important number, and it really is stunning that is appears in so many places. It’s frustrating when our attempts to talk about it are reduced to lists of digits.

Some big news outlets…didn’t do so well. *Time* gave us Pi Day Deals, Freebies, and Events for Math Lovers and Haters Alike. Select quote: “There are plenty of deals meant to appeal to C students who hated math too.” Thanks for making sure we “normal people” know that it’s still OK to openly despise math! (Can you imagine St. Patricks Day deals explicitly marketed to people who hate the Irish? It’s not a good analogy because the Irish are people and math is an idea, but it’s pretty odd to focus holiday coverage on people who hate the idea behind the holiday.) *USA Today* asked us to watch these stunning videos of kids reciting 3.14. The headline is bizarre, but the kids are lovely, and if they enjoy memorizing the digits of pi, good for them. I just wish the coverage had less gawking at non-mathematical activities in it.

Next Pi Day, 3/14/16, is a better approximation of pi than 3/14/15. I guess we’ll be meeting back in a year for another “Pi Day of the century”!

You missed the video “How Many Digits of Pi are Useful?”

http://bit.ly/1xexrND

I enjoyed reading the The Pi Day Link Roundup of the Century. Thank you for posting.

In connection, I recently had a conversation with my middle-school son about Pi Day (this year, Super Pi Day, 3/14/15), and I commented that there are other mathematical constants that also merit their own day.

Until I searched, I did not know that Gary Meisner had set up www.phiday.org for Phi (φ) Day, which is terrific. Thank you, Gary. I would observe φ Day on 1/6. In 2018, there will be a Super φ Day, 1/6/18.

Another constant that deserves its own day is e (noted in the Blog). e Day would be 2/7, and also in 2018, there would be a Super e Day, 2/7/18. (I did not find a similar e Day website, but maybe I missed it.)

Thus, three months running at the beginning of each year, there could be φ Day in January, e Day in February, and π Day in March. Why not? 2018 will be a Super year for two of them, as 2015 was for one of them.

Lastly, there should also be an i (√-1) Day, but siting this one is a bit trickier. Perhaps, it should be celebrated on February 29 for the simple reason that it is “imaginary” for 3 out of 4 years (ignoring century-year issues). i is also related to π, which has its own day, and e, which should have its own day. By that relationship, e^(iπ) = -1, i^i = e^(-π/2) = 0.207879…. Dividing i^i by 3 (as in “imaginary” 3 out of 4 years) gives 0.06929… = 2.0095…/29 ≈ 2/29. This should verify February 29 as i Day, and, next year, 2016, is the next chance.

It would be great to observe all four days. I wonder if there is any interest.

Thank you very much for your consideration.