5. Short story
The history of the greek Pi has about 4000 years. It was the
Babylonians, mathematicians and architects, the first to use it,
interpreting it as 3.125
6. The Greeks used inscribed polygons (internally tangent) and limited (externally
tangent) in a circle.
The length of a circumference is necessarily comprised between an upper limit which
corresponds to the perimeter of the outer polygon, and a lower one, which
corresponds to the perimeter of the inner polygon.
The more sides a polygon has, the more accurate is its approximation to the circle, and
consequently the greater is the accuracy with which one can derive the number that
binds the circumference to its diameter.
Archimedes used polygons with 96 sides.
7. • In 434 b.C. Anassagora tried to square the circle. Then, in III b.C.
Century, Archimede approximated this number to 3,1419.
Afterwards, a lot of mathematicalists studied this number: Newton,
for example, calculated the first 16 decimal digits, while the
supercomputers calculated approximately 5 trillions of digits.
8. Even if all the trunks and all
the leaves of all the trees in
the world were filled with
thousands of digits, the
Earth’s forests would not be
sufficient to represent the pi's
digits.
9. But what really the Pi number is for?
We might think that it is rather a
mathematical phenomenon, a kind of
monster to show in exhibitions.
Yes, it’s true. It’s the relationship between
the circumference and the diamater of a
circle, but why should we care?
It could look like a marginal detail of our
existence, one thing to know once for all and
then forget.
10. π
In our daily life, we need to use it rarely.
So why couldn’t we just tell that π=3 -as apparently Chuck
Norris does- or accept the Indiana House of Bill n. 246 -dated
1897- that fixed π=3,2?
Wouldn’t our school life be greatly semplified?
11. π
π
π
The problem is much more complex.
Simply, it is not an irrelevant mathematic curiosity on
the edge of our daily lifes, but it is, on the contrary, an
integral part of it. A mistake in its calculation could
have disastrous consequences.
12. Every time a rope or a wave vibrate -an electromagnetic wave,
such as the sound of a musical instrument- or even when
something spreads –for example the temperature in a metal bar,
or a scent in the air, or the seasonal flu- π is there to govern
their oscillations, the timbre of that particular physical
phenomenon.
13. In fact, the natural frequencies of oscillation are always governed
by periodic functions (sines and cosines) that involve Pigreco.
A mistake in the calculation of a resonance frequency of a bridge
can also contribute to make it fall down.
15. You have to use π if you are interested in finance,
medicine, demography or industrial quality.
16. In fact, the Gaussianian, that has such
important role in statistics and
consequently in all natural and social
sciences, depends in a decisive way by π.
17. CURIOSITIES
• The height of an elephant from the ground to its
shoulder can be determined by multiplying by 2π
the diameter of one of its paws.
• The "PI DAY" is a celebration day in honor of this
constant. It takes place on March 14 with
celebrations around the world (festivals, sweets, t-
shirts, games and more in general a tono that has to
do in some way greek Pi). Last year it was March 14,
2015, and in Anglo-Saxon countries the date
indicates the month and then the day, therefore the
party was even more impressive, because 3 14 and
15 are exactly the first 5 digits of the constant. An
article about this event was voluntarily published by
9:26 and 53 seconds, by matching the first 10 digits
