# Happy pi day 2025 **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [March 14, 2025, 2:07pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557 "2025-03-14T14:07:10Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [March 14, 2025, 2:07pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/1 "2025-03-14T14:07:10Z")
Pretty much going to be the same as all the other pi days i suppose but shouldn’t pass by without notice. ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [March 14, 2025, 2:11pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/2 "2025-03-14T14:11:33Z")
Wasn’t the only _true_ Pi day back in 1592? ---
**Author:** ![zimaane](https://avatars.discourse-cdn.com/v4/letter/z/a3d4f5/32.png) [@zimaane](https://boards.straightdope.com/u/zimaane)\ **Post date:** [March 14, 2025, 2:17pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/3 "2025-03-14T14:17:14Z")
In honor of Pi day, I give you the Wallis Product: pi/2 = (2/1)_(2/3)_(4/3)_(4/5)_(6/5)\*… Looks cool, but converges a bit too slow for my taste. At n = 100, it has pi = 3.1206079 ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [March 14, 2025, 2:22pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/4 "2025-03-14T14:22:54Z")
It depends. If we’re talking about truncating it at the sixth digit to the right of the decimal point, then 1592. But if were talking about rounding it at the sixth digit, then 1593. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [March 14, 2025, 2:31pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/5 "2025-03-14T14:31:18Z")
> [@running\_coach](#): > > Wasn’t the only _true_ Pi day back in 1592? Of course soon enough it’ll be the year 15926 and we can _really_ party down. Then, ref @Crafter_Man, do it all again in 15927! W00t!! I’ve made my reservations. How about y’all? 😉 ---
**Author:** ![peedin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peedin/32/14095_2.png) [@peedin](https://boards.straightdope.com/u/peedin)\ **Post date:** [March 14, 2025, 2:46pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/6 "2025-03-14T14:46:44Z")
I will have a slice of pecan, blueberry, and apple. My favorite pi(e)s. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [March 14, 2025, 2:54pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/7 "2025-03-14T14:54:03Z")
It’s probably a good thing the value of _pi_ is 3-something, not 7-something. Seven slices of any flavor(s) would be a lot. 😉 ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [March 14, 2025, 3:41pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/8 "2025-03-14T15:41:31Z")
In a now annual tradition, Matt Parker has posted a calculating π [video](https://youtu.be/vlUTlbZT4ig) to his Stand-up Maths channel. The TLDV version: You have a wall, mass2, mass1 on a 1-d frictionless surface. If you slide mass1 towards mass2 and bounce it (perfectly), mass2 bounces against the wall, comes back and hits mass1, etc. The total number of collisions gives you the first x digits of π if mass1 has a certain square power of 10 times more mass than mass2. E.g., if they are equal there are 3 bounces. If mass1 is 100 times more than you get 31 bounces, etc. Experiments on an air table and formulas on a white board ensue. :Large number of digits of π do not. Guest stars Steve Mould and 3Blue1Brown. The latter had done a video on this that inspired the test. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [March 14, 2025, 10:35pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/9 "2025-03-14T22:35:06Z")
It is also Einstein’s birthday–as well as my anniversary (61st). Wallis’s product is really quite amazing. Another formula is \pi^2/6=1+1/4+1/9+1/16+1/25+\cdots And \pi^4/90=1+1/16+1/81+1/256+1/1225+\cdots Similar formulas are known for the sums of reciprocal nth powers for all even n. For odd n, essentially nothing is known. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [March 14, 2025, 10:54pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/10 "2025-03-14T22:54:09Z")
> [@Hari\_Seldon](#): > > Another formula is > \pi^2/6=1+1/4+1/9+1/16+1/25+\cdots Thanks to Euler, who is credited for popularizing \pi as the symbol for the number we celebrate today. > **[Basel problem](https://en.wikipedia.org/wiki/Basel_problem)** > > The Basel problem is a problem in mathematical analysis with relevance to number theory, concerning an infinite sum of inverse squares. It was first posed by Pietro Mengoli in 1650 and solved by Leonhard Euler in 1734, and read on 5 December 1735 in The Saint Petersburg Academy of Sciences. Since the problem had withstood the attacks of the leading mathematicians of the day, Euler's solution brought him immediate fame when he was twenty-eight. Euler generalised the problem considerably, and The B... ---
**Author:** ![dougrb](https://avatars.discourse-cdn.com/v4/letter/d/76d3ee/32.png) [@dougrb](https://boards.straightdope.com/u/dougrb)\ **Post date:** [March 14, 2025, 11:18pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/11 "2025-03-14T23:18:45Z")
> [@ftg](#): > > Guest stars Steve Mould and 3Blue1Brown. For the math geeks out there, the 3Blue1Brown video is a must watch. They plot the conservation of momentum and conservation of energy on a circular plot, which is how PI comes out of it. Linking to that section here. [https://youtu.be/6dTyOl1fmDo?t=371](https://youtu.be/6dTyOl1fmDo?t=371) ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [March 14, 2025, 11:54pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/12 "2025-03-14T23:54:06Z")
I always liked \frac{\pi}{4} = \frac{1}{1}-\frac{1}{3} + \frac{1}{5} - \frac{1}{7} + \ldots ---
**Author:** ![RTFirefly](https://avatars.discourse-cdn.com/v4/letter/r/c77e96/32.png) [@RTFirefly](https://boards.straightdope.com/u/RTFirefly)\ **Post date:** [March 15, 2025, 12:32am UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/13 "2025-03-15T00:32:59Z")
> [@Thudlow\_Boink](#): > > Thanks to Euler, who is credited for popularizing \pi as the symbol for the number we celebrate today. [Speaking of Euler…](https://xkcd.com/2694/) ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [March 15, 2025, 12:48am UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/14 "2025-03-15T00:48:49Z")
Pi Day is for hanger-ons, amateurs, and wannabes. Speaking for myself, I am giddy with excitement that [Tau Day](https://tauday.com/) - June 28 - is less than four month away. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [March 15, 2025, 1:07am UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/15 "2025-03-15T01:07:30Z")
> [@Crafter\_Man](#): > > [Tau Day](https://tauday.com/) - June 28 - is less than four month away Hear, hear ---
**Author:** ![ParallelLines](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/parallellines/32/3575_2.png) [@ParallelLines](https://boards.straightdope.com/u/ParallelLines)\ **Post date:** [March 15, 2025, 2:46am UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/16 "2025-03-15T02:46:29Z")
In honor of Pi day, I texted my lovely wife a heartfelt message: 3.14159 To which she squee’d with joy (yes, I could have had more digits, but this is more than enough for almost anything in the Newtonian world)! She brought home a $1.99 mini-blueberry pie that her office handed out to all the engineers. 'Tis a day of much love! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 15, 2025, 2:19pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/17 "2025-03-15T14:19:38Z")
> [@dougrb](#): > > For the math geeks out there, the 3Blue1Brown video is a must watch. They plot the conservation of momentum and conservation of energy on a circular plot, which is how PI comes out of it. Linking to that section here. The third video in the series is the really interesting one. They convert the problem into a problem with light bouncing off of mirrors at an angle to each other. > [@Crafter\_Man](#): > > Pi Day is for hanger-ons, amateurs, and wannabes. Speaking for myself, I am giddy with excitement that [Tau Day](https://tauday.com/) - June 28 - is less than four month away. Tau day has two critical problems, compared with pi day. First, it’s not during the school year, so you can’t celebrate it with your classes. Second, there’s no dessert named taue that you can justify binging on. For Math Club, Wal-Mart had a great price (something like 79 cents) on single-serving individual pies, and we calculated that we’d need about 40 of them. We ended up using 39, with the last one currently sitting in my fridge awaiting lunch. We also had some videos playing, and a contest for memorizing digits (the winner had 62 digits past the decimal point). ---
**Author:** ![ParallelLines](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/parallellines/32/3575_2.png) [@ParallelLines](https://boards.straightdope.com/u/ParallelLines)\ **Post date:** [March 15, 2025, 7:32pm UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/18 "2025-03-15T19:32:10Z")
> [@Chronos](#): > > Tau day has two critical problems, compared with pi day. First, it’s not during the school year, so you can’t celebrate it with your classes. Second, there’s no dessert named taue that you can justify binging on. Just take the day to play Warhammer 40k! > **[T'au Empire](https://warhammer40k.fandom.com/wiki/T%27au_Empire)** > > "We are five castes, one people. We stand united, dedicated wholly to the Greater Good. As we progress, we will encounter further barriers. We will overcome them. Our future is now, believe in our destiny." —Ethereal Supreme Aun'Va The T'au Empire... And sup upon silken tofu in ginger syrup! > **[Vietnamese Silken Tofu in Ginger Syrup Dessert (Tau Hu Nuoc Duong) - Vicky Pham](https://vickypham.com/blog/vietnamese-silken-tofu-ginger-syrup-tau-hu-nuoc-duong/)** > > A light and delicate Vietnamese/Chinese dessert. You may have seen this dessert as one of the many offerings at Dim Sum or as a popular street food in Vietnam. (I apologize to any who feels that I’m cheating by using the English transliteration to get “Tau” to work, it’s a fair cop!) ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [March 16, 2025, 12:40am UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/19 "2025-03-16T00:40:45Z")
Why not eat two pies on tau day? Too bad December does not have 56 days. ---
**Author:** ![dougrb](https://avatars.discourse-cdn.com/v4/letter/d/76d3ee/32.png) [@dougrb](https://boards.straightdope.com/u/dougrb)\ **Post date:** [March 15, 2026, 12:26am UTC](https://boards.straightdope.com/t/happy-pi-day-2025/1015557/20 "2026-03-15T00:26:43Z")
For pi day 2026… Yet another way to calculate pi. Matt Parker [https://www.youtube.com/watch?v=kahGSss6SsU](https://www.youtube.com/watch?v=kahGSss6SsU)