Happy Pi Day to you, belatedly. I write these words in the last hour of 14 March here in the UK, or 3/14 in US notation. Out there in California, Oregon and everywhere else in the Pacific time zone, you still have many hours to celebrate.

For the first time ever, my children and I spent some time discussing and playing with Pi, the mathematical constant, 3.14 to 2 decimal places, on 3/14 itself. A few weeks ago, when one of us looked up Einstein, and discovered that he was born on this date in 1879, I observed that he was born on “Pi Day”. A few years back I would have had to explain what this meant but my daughter, who is now 14, worked it out for herself, and liked the idea.

Today, after lunch, she showed me a webpage that she had brought up on her phone, listing Pi to 1 million decimal places. I told her about people who memorize large chunks of it and recite it , specifically Daniel Tammet, My wife and I read and enjoyed his memoir “Born on a Blue Day” 10 years ago, when the children were too young to be interested in his feats of memory. My daughter started doing her own research, discovering that people have gone way beyond Tammet’s recital of Pi to 22,000 places. The world record, according to this page on pi-world-ranking-list.com, was set in 2015: 70,030 digits recited in 17 hours 14 minutes.

I have known Pi to 8 decimal places (3.14159265) since I was 15, and have never gone much beyond that. My school year was the first to be allowed calculators in Additional Maths O-Level exams. Our predecessors had used slide rules. The model that we were advised to buy included a Pi button, because we would be calculating areas and circumferences of circles. Within a few months, the Pi button on my calculator had become unreliable, rather like the fast-forward options on the remote control for our multi-channel box (which I wrote about here in May 2018). Sometimes it would work first time, sometimes you could persuade it to work by pressing it in different ways (with varying degrees of pressure, or at different angles), sometimes it didn’t work at all. I was concerned that I might be unable to bring up Pi on the device in an exam, when it was most needed, so I scratched “3.14159265” with a pin onto its surface. That way I could enter the figures manually if needed, and they have been lodged in my brain ever since.

Today is also Laetare Sunday, the 4th Sunday of Lent. I wrote about it on these pages a few years back, noting that it’s “meant as a small, brief respite from the sacrifices of Lent. If you’re off booze, chocolate or crisps, you could take the day off, indulge yourself a little”. I have been off the booze and the crisps since Ash Wednesday, and the children have successfully kept away from chocolate. We discussed the idea of breaking our Lenten fast. I said, “How I want a drink, alcoholic of course”, but I didn’t mean it literally. It was all I could remember of the mnemonic for the digits of Pi: each word in the sentence has the same number of letters as the corresponding digit (“3-1-4-1-5-9-2-6”). This page, titled “Pi Worplay”, takes you further: “How I want a drink, alcoholic of course, after the heavy lectures involving quantum mechanics”. That gives you 3.14159265358979, which is as far as I’m ever likely to get.

As things turned out, the children stayed off the chocolate and, although the first 8 words of the Pi mnemonic might have described my feelings in previous years, I have stayed off the booze. Roll on Easter Sunday.