SPEAKER 1: To celebrate the mathematical constant of pi,
we're going to attempt the most accurate calculation ever
of pi using pies.
Now, before we do our pie-based pi calculation,
we'll have a quick crash course in circles and why pi
so important.
Now to do that because we're in the UK, home of many famous
circles, we've come from the oldest and greatest circles,
which is, of course, this one.
It's the football circle here at Knott County Football Club.
Apparently, they are the world's oldest
Football League club.
SPEAKER 2: How do you know that?
SPEAKER 1: There's a giant sign that says that
right behind me.
Which does mean for a while there, I guess they had no one
else to play, but who knows.
So this circle here, as you can see, there's two things
going on with the circle.
First of all, there is the diameter.
So it's this nice, wonderful straight line here that goes
right through the middle of the circle.
And the great thing about diameter is it's a nice
straight line.
So if I wanted to, I could get a measuring tape, and I could
measure from the start all the way across here to the finish
and get a very precise measurement of the distance
across the circle.
Now around here, we have the circumference.
Now this is a lot harder to measure.
As you can see, it's a curved line.
So instead of having to measure it
directly, we can use pi.
Now pi is the ratio of the straight line diameter to the
total distance all the way around the outside.
And if we know that ratio, we can do one measurement for the
diameter, multiply it by pi, and get the exact distance all
the way around the outside.
All right, enough messing around on a football pitch--
let's go get our pies out.
All right, first thing we need is a circle.
SPEAKER 2: People find it notoriously
hard to draw circles.
How do you get around this problem?
SPEAKER 1: Actually, we were talking to the guy who does
the circle on the pitch for the football stadium here.
And he does it the same way, I think, most people do.
He gets a bit of string, makes the middle bit of the string
remain perfectly still in what will become the center of the
circle, and then use that to draw a nice, equal distance
line all the way around.
In fact, I guess that's the best way to define a circle--
it's the line of all the points the same distance away
from a center point.
The center point will be my pen, and the
outside will be the chalk.
All right.
Let's do this.
My goal is to not actually do any measurements other than
using pies.
So the entire thing is going to be pie-based.
We get the circumference and the exact number of pies, give
or take, we get the diameter and number of pies, divide one
by the other, we get pi.
Pi was historically really calculated this way because
it's notoriously inaccurate to try and calculate pi by
measuring a circle.
To get any kind of accuracy on our final answer, we have to
be as precise as we can be.
This is a mild problem because I want to go through from the
very edge of the circle, but, as you can see, I've
positioned all the pies exactly on the line as if
they're little mini tangents.
So I'm going to have to move these two out, and then I can
start doing the diameter exactly on the circumference
there like that.
So that's 84 and 1/3.
264 and 2/3 pies around, where the diameter is 84 and 1/3 pi.
To get pi, we just divide the circumference by the diameter.
OK, and if we actually work out what that is, it equals--
that's pretty good.
Pi from pies, we got 3.13834, which is approximately 3.14.
So using pies, we've got pi to be 3.14.
I am a very happy man right now.
Anything between 3.1 and 3.2, I would have been happy.
But to get 3.14, I'm downright ecstatic.
So there you are.
That is officially the world's most accurate calculation of
pi using pies.
SPEAKER 2: It wasn't really something we planned to make
part of the video, but as a lot of you have asked, the
pies we used were donated and were no longer fit for human
consumption.
So we couldn't give them to charity, like we did, for
example, with all the to baked beans that
Heinz donated us earlier.
However, in the spirit of pi day, we did attempt to make
some kind of gesture, and we donated 314 pounds, of course
314, to a local charity here in Nottingham that helps give
food to people in times of crisis.
Now, a lot of have expressed a lot of interest in charity,
and we'd really encourage you, if you're in a position to do
so, to also make a donation.
And we've put some links under the video.
And because we're all numberphiles here, why not
make your donation a multiple of pi in some way?
SPEAKER 1: 16, 17, 18, this is length L. And that means that
the distance here is 2L.
OK?