PI GRECO

WHAT IS "PI GRECO"?The greek Pi is a constant used in mathematics and physics, denoted by the Greek letter you just have seen above.

Numerically it is the value that is obtained by dividing the length of a circle to its diameter.

CIRCUMFERENCE

DIAMETER

Its value is: 3.14159 26535

SHORT STORYThe 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

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.

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: Netwon, for example, calculated the first 16 decimal digits, while the supercomputers calculated approximately 5 trillions of digits.

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 greco’s digits.

But what really the Pi greco 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.

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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?

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The problem is, unfortunately, 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.

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.

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.

And that’s not all…

You have to use π if you are interested in finance, medicine, demography or industrial quality.

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.

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 of Pi greek.