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Saturday, January 9, 2010

3.14...) Pi in the Sky

Did you see that Fabrice Bellard has computed pi to nearly 2,700 billion decimal places?There is an article here. Why do I mention this? Because this post comes just after my third post, and pi comes between 3 and 4. Pi is interesting. Ian Stewart said, in that article, that all numbers are interesting, but pi is more interesting than others.

We readily accept people saying "Oh, I am hopeless with numbers", but there would be frowns if we said the same about language. Not that this is wrong, just interesting, don't you think?

Pi goes back a long way. Longer than me. Longer than Don, who goes back longer than me. Don is much better at maths than me, so I enjoy exchanging emails with him every day...

Nearly every day. Mathematics people like to be precise. Precise in their maths, but sometimes more flexible outside of maths. Don is a mathematician. He got paid for playing with numbers. He does research, finding new things. I teach maths, but I found out a lot about mathematics from Don. Thanks, Don.

Birds can count up to about four. When you remove one egg from a nest of three eggs, they get upset. Remove from ten, and they won't. Birds probably don't know about pi. We don't teach this in schools. You can't get a job from knowing such a thing.

You can get a good job without knowing much about pi. Matthew, do you know much about pi? Dad may. He was good at maths when he was a nipper. His nickname was Tiger. As well as being good at maths, he was good at sport. Dad, can you remember much about pi?

Terence is the man behind the glasses in the photo. Terence is a wonderful artist. He must draw the odd circle. Probably a very good circle. I never asked him if he knew about pi. It could just be a dim memory from his school days. You can draw bloody good circles without knowing pi. I can draw terrible circles and I know a bit about pi.

Are you still there? I must stop rambling. No, we forget that the path is our goal. Life would be easier if I could stick to the path though.

When I was at high school, I met pi. A funny symbol. The Greek "p". We used it to find the circumference of a circle, the area of a circle. We ate it for lunch. When we had to do a calculation, we said it was 22/7. Questions had other numbers like 14cm, so that things all cancelled down, and we got a nice number as an answer.

Pi is nice, but not a nice number to write (unless you know the Greek "p").

My calculator had a pi button, and I could get it to 8 decimal places. I used pi to help me pass maths, and that let me get a job.

Here, in Bhutan, calculators have only just arrived in the maths classroom. They are still shunned my some teachers. "Use those, and the brain will rot." I use a calculator. My brain is still pretty good. I do the thinking, and let my dear calculator do the work. No, I don't know how it does it. Could be little people inside. So, 22/7 is still used. Not that this is bad. Just a wee bit wrong. You see, pi is irrational. If you click the link, you will see. If you don't, I can make it easy. When you write it as a decimal, the decimal part goes forever with no pattern. That means it cannot be written exactly as a fraction. Nor as a decimal.

At school we only met a couple of irrational numbers, so they seemed rather rare. When I went to university, I found out otherwise. There are more of these irrational numbers than the rational ones. Rational numbers can be written as fractions.

The thing is, the students (and some teachers) think that pi is 22/7. This bugs me just a little. Pi is far more beautiful than that.

On a more mundane level, how big is 2,700 billion? How many zeroes after the 27? How long would it take to write that many zeroes? Are there more stars in the sky?

Now if my salary was that many ngultrum a year, I would be quite well off.

There is a lovely site about pi here. Make sure you turn up your sound.


  1. I didn't get where I am today by knowing about pi.

    Dad may have been good at maths, but he never learned to play chess. He said you tried to teach him once.

  2. And what did not knowing pi bring you? A lovely wife; able to travel around the world; being your own boss; multi-linguality (is that a word?), a large rambling (very rambling) garden; all the money you can eat. You call that happy?

    It would be nice if you could show Dad this blog.

    If you want a game of chess, you could start off by playing my good friend David. After you have mastered him (it won't take long), you could move up to your cats, then eventually me.