The meaning of pi

My brother is a math teacher (retired), who loves numbers and always has. He and I and others in the family have an ongoing, never-ending, heavily-CC'd email conversation about everything in the universe, and an old friend of both me and my brother is always included in the emails, since he's been part of the living room for fifty years and he's basically family.

Yesterday my brother, Mr Math, emails, "This Sunday celebrate Pi-day."

Because it's 3.14. It's a very stale joke he's been telling every March since he was 8 years old.

I reply, "I don't even know what pi is. I know the number to a few digits, and it's math and geometry and all the smart people and science fiction agree that it's important, but I never saw the point and it never sunk into my head."

Now, this is actually a calculated reply, and not quite true. I do know what pi is, vaguely, but mostly I know that my brother will explain pi to me again, and he loves doing that. And also, our friend who's included in the CC's flunked high school algebra long long ago, so my comment will make him feel good.

And it works. Our friend says, "The same with me Doug, the same here. I like a good apple🍎or cherry🍒Pi 🍽 myself!!" And my brother explains pi, so he feels like a math teacher again. Everybody's happy.

For anyone who needs it or wants it, here's my brother the math teacher, explaining pi:

Pi is really very simple in a complex way. Everyone knows that all circles have one thing in common. Their symmetry. The (string) distance around can be likened to the (transverse) distance through a circle. The complex relationship is that there’s some (fixed) relationship for 3 in, 6 in, 12 in, etc. circles. The around distance (circumference) something of the same in ALL circles as relates to the across distance (diameter).

Well, the beauty of a circle is that around is like across in some way. The Greeks thoughts were that circles represented perfection. The Egyptians and Mayans knew this too.

The truth of the matter is that C = π X D.

Yes, π is roughly 3.14159265373 and so forth, but it’s really the simple aesthetic beauty. Maybe the number isn’t simple. The truth is.

Thanks, bro. Sometimes I don't quite understand you, but I love you. I still don't give a hoot about pi and barely understand it, but two people I care about got a smile, and so did I.



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  1. Doug, that your word processing software turned circumference into circumstance might reveal more about the n-dimensional nature of the universe than any explanation I've heard. I don't know much, but whenever somebody asks me to explain something slightly complicated I ask them whether they want the trivial, short, medium or long explanation. *Nobody* asks me to explain math stuff; it's not exactly my strongest suit (and I've shitcanned all but one of my suits (when they incinerate you do they dress you up? I need to look into that.)

    And anybody who knows me runs like a maiden from a plague (well, here we are again 400 years later) if I even hint that I'm favoring the long answer.

    Since mathematics is the language of physics, and physics is the branch of science we use to describe the characteristics of the universe we live in, we can sometimes back into inferences about that universe via mathematics. Pythagoras thought so, and so did Einstein. (Einstein famously described himself as an average mathematician; he wasn't being modest, just grading on a different curve).

    Pi is an irrational number. Why the fuck should a ratio as important and basic as pi be a non-repeating decimal? Pythagoras thought that said something important about the universe. Einstein didn't start with pi, but he did start with mathematical (apparent) anomalies and plunged into the depths of complexity that constitute the architecture of everything we can experience (and more), discovered the universe's speed limit, then got his hands dirty explaining why the universe behaves as it does.

    Could the universe have evolved differently? Is there a universe where pi is a rational number? Maybe. In its first few microseconds the universe developed in random ways, likely quantumly random, that yielded, after a second or so, the universe we know today.

    Astrophysicists think it could have happened differently. I'm one of the geeks who thinks that circumstance is just as important as circumference.

    Just musing on a day some people celebrate the slaughter of the American Indians.


    1. Probably my fault, more than a spellchecker's. 'Circumference' is a word I type and use so rarely, my fingers went for 'circumstance' instead.

      And I still don't understand the importance of pi. Reads like you understand it enough for all three of us, though.

  2. Just to be clear, nope, my math sucks. I do read popular books on astrophysics, but they are books that anybody who is sufficiently broken to enjoy this site could understand. Just at random, I'd recommend The Particle at the End of the Universe by Sean M. Carroll. It's well-written and doesn't require a vast knowledge of physics. My half-vast knowledge sufficed. Glad I stuck around and got that high school diploma.


    1. I don't usually do manual labor, it's against my lack-of-religion, but sometimes I got dragged into it because I worked in the mailroom, which was also the loading dock. One sweaty afternoon me and a pretty coworker were stacking incoming boxes on a cart, to be pushed down the hall and unloaded and put away, and we stacked the pushcart a wee bit too high. When I started pushing, the boxes started wobbling, and with a great crash as we leapt out of the way, the tower came tumbling down.

      "Physics is a bitch!" I shouted, and the pretty girl laughed. That, sir, is all I know about physics, and I'm not absolutely positive that gravity *is* part of physics or either is part of math.

      She laughed, though. That's what's important.


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