Happy Friday, math freaks.
March 14 is Pi Day – an international celebration of π – you know, that number that you learned in algebra class that is roughly equal to 3.14159.
An non-repeating, non-terminating number, Pi just goes on and on and on.
Fortunately over the centuries Pi has proved useful, so it’s made sense to calculate its value to over one trillion decimal places.
Pi in history
Since at least ancient Babylon, mathematicians have been working to calculate the true value of Pi.
Historians claim that by measuring extant structures from the ancient world, once ratios are studied, there’s no question that the architects and builders knew a fair bit about the proportions of circles.
Certainly the ancient Egyptians did, as the pyramids at Giza incorporate some of the proportions of circles.
When you think about, it makes perfect sense.
By using known proportions, you know how many enormous stone blocks to have your slaves quarry and move.
The Greek letter ‘π’ has been used to represent the value of Pi since 1706, when William Jones chose it to stand for ‘p,’ the perimeter of circles.
‘π’ came into popular use in 1737, when it was adopted by Leonhard Euler, a more prominent Swiss mathematician.
Why Pi are round
Pi, it turns out, is very handy for telling us important things about circles and circular objects, like area and volume.
Over the course of human history, having measured many, many circles, man has discovered that the circumference of a circle is a little bit more than three times its diameter, about 22/7 (3.14) circumference to diameter.
This has proven true of all circles, not just ones we’ve measured.
A source of constant amazement
Because the ratio of circumference to diameter is always 3.14, Pi is what’s known in science and mathematics as a ‘constant.’
So when you see ‘π’ in mathematical formulas, it always equals 3.14.
The volume of pies
As it turns out, we need only 39 of Pi’s post-decimal digits (of the over a trillion that we know about) to calculate the spherical volume of the universe.
When a measurement is accurate to that degree, you can find even more practical uses for it.
For instance, because it is true that the circumference of a circle is 2πr, where ‘r’ is the radius (half the diameter) of a circle, you know exactly how many bricks it will take to build a ring around your goldfish pond.
Need to know how many square feet your pond covers?
Use Pi to calculate the area of your brick circle: A(rea) = π r2 = square footage of the surface of my goldfish pond.
Okay, so how much water will it take to fill my fish pond?
Assuming that the pond is half a sphere, half of 4/3 π r3 (volume of a sphere) will tell you how many gallons of water you need to fill the pond.
Pi is handy like that, whether you’re calculating the surface area of a doughnut or trying to figure how much wood it takes to make a pencil [V(olume) = π r2 h].
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