407. Memorising Pi
March 14, is Pi day – a celebration of the famous mathematical constant Pi, 3.1415926535 …
Pi is the ratio of a circle’s circumference to its diameter. It has an infinite number of decimal places, and there is no pattern to them, and no point where it starts to repeat. This makes it a challenge to memorise, which is presumably why memorising Pi has been such a popular pastime amongst people of a certain type. It is the ultimate nerdy challenge to see how many decimal places one can remember.
There is a website that lists people who have memorised Pi from all around the world. It shows the record for each country and globally, and other creditable attempts. The official world record is an astounding 70,030 decimal places, which took Suresh Kumar Sharma of India over 17 hours to recite in 2015.
There is also an unofficial record of 111,700 decimal places, by Akira Haraguchi from Japan, in 2006. It’s amazing what the human mind can do.
I had long known about this quirky hobby of people memorising Pi but had never been tempted myself. But on a whim, about a decade ago, I decided to give it a quick go, just to see how easy or hard it was. In a few hours, I was able to memorise 100 decimal places. I had no intention of doing more than that, but I found it was easy to add on a few more digits each day, so over time my string of memorised decimal places slowly grew.
It required regular reminders to keep the numbers in my memory, but I found mentally reciting Pi to be quite enjoyable and relaxing – a good thing to do when there’s nothing much happening. It was also interesting to see what my brain could do. It seemed to get a bit easier as I memorised more and more.
Eventually I memorised over 1,600 decimal places. That’s a tiny number compared with the world record, but I felt quite chuffed to have done that much. To get onto the official website, I had a couple of colleagues witness me reciting it. Here’s a video of me doing that in August 2020, and getting up to 1,609 decimal places.
That is sufficient to position me at number 9 in Australia and number 137 globally in the all-time lists.
After that successful attempt I stopped doing regular practice, and over time I steadily lost my ability to remember so many digits. Now I can remember 250 digits, but I’d have to do a heap of practice to get back to where I was in 2020. I’m satisfied with having done it back then.
Seems a totally irrational thing to do Dave. What’s the point?
At the beginning you seemed to recall triplets, then later quintuplets. I didn’t stay with you beyond about 200 – I was sufficiently impressed. At one stage you hesitated and I thought ‘Oh no! He’ll lose his rhythm’ but no, you picked it up.
Yep, quite irrational from any practical perspective. If the earth’s equator was a perfect circle and you knew the diameter exactly, you’d only need 10 decimal places of Pi to work out the circumference accurate to within 1 mm.
But it was still fun to take it on as a challenge.
I do not find this surprising David. Between you and our mutual friend Don, I find a powerhouse of intellect. I am happy observing from the sidelines as I enjoy hearing of your feats. I liken it to watching any battle in sports. I’m have no doubt that you will continue to challenge your mind to see how far you can go. You always give me food for thought.
Did you know that Pi includes a sequence with six nines in a row? It occurs at 5:36 in the video.
Impressive and interesting Dave. Many people mnemonics, or ‘link and story’ methods to assist with these memory feats. Did you use them or just ‘brute force’ recollection?
Hi Ian. I think that the people who have memorised huge numbers of decimal places, or huge lists of other items, have generally used the ‘link and story’ method. The guy who memorised 100,000 places (which is not officially recognised) assigned several words to each digit, and then selected from those words to create a long, long story that was easier to memorise. I didn’t do that. I just used pure brute force. I looked for patterns within the random sequence of digits and used that to help me. For example, starting at digit 71, the numbers go 062862089986280. I broke that into these chunks: 0628 6208 998 6280. I noticed that in the 1st, 2nd and 4th chunks, the numbers are the same, and almost in the same order, except that the 0 moves later in the sequence each time. So that was easy to remember. Then I just had to memorise that 998 comes after the second chunk, using brute force. So that sort of thing helped a lot, when I could find patterns. My mind does tend to naturally pick out patterns in numbers, so there are hand-holds throughout the long list. But it still took a massive amount of effort to memorise it all.