What Is Pi? A Short History of This Incredible Number
Pi: An Incredible Number
In this article, we’re going on an incredible journey through thousands of years of history to discover the story of a magical number called ‘pi.’ Let’s get started!
Imagine a circle, like a pizza or a bicycle wheel. No matter how big or small the circle is, there’s a special number we can get from it, which always stays the same. This number is called ‘pi’ and is usually represented by the lowercase Greek letter π. Its value is approximately 3.14, but the truth is, π never ends! It’s an irrational number, which means its decimal places go on forever!
Imagine a circle, like a pizza or a bicycle wheel. No matter how big or small the circle is, there’s a special number we can get from it, which always stays the same. This number is called ‘pi’ and is usually represented by the lowercase Greek letter π. Its value is approximately 3.14, but the truth is, π never ends! It’s an irrational number, which means its decimal places go on forever!
The Greek letter Pi
Pi and Ancient Civilisations
Now you might be wondering, how did we discover π? The story of π began thousands of years ago in ancient civilizations like Egypt and Babylon. People noticed that when they measured the distance around a circle (the circumference) and divided it by the distance across the middle of the circle (the diameter), they always got the same number, regardless of the size of the circle. What was that number? You guessed it, it was π!
The circumference and diameter of a circle
An early mention of the ratio between circumference and diameter features in the Rhind papyrus, an Ancient Egyptian document dating from approximately 1650 BC. In this papyrus, π was approximated to about 3.1605. Not bad for such a long time ago.
Fast forward to Ancient Greece in approximately 250 BC, where the famous mathematician Archimedes made an important discovery about π. He started by drawing a unit circle (a circle with radius 1). He then added a large square outside the circle with its edges touching the circle and a smaller square inside the circle with its corners touching the circle.
By simple geometry, he showed that the area of the small square is 2 and the area of the large square is 4. As the area of a circle is πr2, the unit circle has an area of π, which must lie between the areas of the two squares, hence 2<π<4. By applying this reasoning to polygons with more and more sides, he showed that π was somewhere between 3 10/71 and 3 1/7 (3.1408 … and 3.1428 … in decimal). Even though we now know π to trillions of digits, Archimedes’ work was a significant step forward.
Fast forward to Ancient Greece in approximately 250 BC, where the famous mathematician Archimedes made an important discovery about π. He started by drawing a unit circle (a circle with radius 1). He then added a large square outside the circle with its edges touching the circle and a smaller square inside the circle with its corners touching the circle.
By simple geometry, he showed that the area of the small square is 2 and the area of the large square is 4. As the area of a circle is πr2, the unit circle has an area of π, which must lie between the areas of the two squares, hence 2<π<4. By applying this reasoning to polygons with more and more sides, he showed that π was somewhere between 3 10/71 and 3 1/7 (3.1408 … and 3.1428 … in decimal). Even though we now know π to trillions of digits, Archimedes’ work was a significant step forward.
Using the Symbol for Pi
The symbol we use for π was introduced by the Welsh mathematician William Jones in 1706 in his work Synopsis Palmariorum Matheseos. His use of π to represent the ratio between circumference and diameter stems from abbreviating the Greek word ‘periphery,’ which had been used by earlier mathematicians to represent the circumference itself.
It was the prolific Swiss mathematician Leonhard Euler who popularised the symbol, beginning with its use in his 1736 work Mechanica. His correspondence with other mathematicians around Europe spread its use, and since then, π has been the symbol we all know and love.
It was the prolific Swiss mathematician Leonhard Euler who popularised the symbol, beginning with its use in his 1736 work Mechanica. His correspondence with other mathematicians around Europe spread its use, and since then, π has been the symbol we all know and love.
Leonhard Euler (1707 – 1783)
What do the prisoners do?
Did you know there’s a special day dedicated to celebrating π? That’s right! On March 14th, we celebrate Pi Day. Why on this day? Because the date 3/14 matches the first three digits of π: 3.14. On this day, people have fun with pi-related activities, like reciting as many digits of π as they can (with the unofficial world record supposedly being over 100,000 digits) or even eating delicious pies. Pi Day is also the birthday of arguably the most famous scientist of all, Albert Einstein.
How Do We Use Pi?
π isn’t just a cool number we learn about in maths class. It’s actually everywhere! π is used in various fields like engineering, physics, music theory, communications, and even in our everyday lives. For example, people may use π when designing buildings, calculating distances, or figuring out how much string we need to wrap around a gift.
Example: Using Pi In Calculations
A circular field has a diameter of 50 metres. The field’s owner wants to build a fence around the whole circumference of the field. How much fence does he need?
We know that circumference/diameter = π. Therefore,
circumference = π x diameter = 3.14 x 50 = 157 m.
So there you have it! The fantastic story of π. It’s a number that has fascinated mathematicians for thousands of years and is still incredibly important today. See if you can think of any more uses for this amazing number.
We know that circumference/diameter = π. Therefore,
circumference = π x diameter = 3.14 x 50 = 157 m.
So there you have it! The fantastic story of π. It’s a number that has fascinated mathematicians for thousands of years and is still incredibly important today. See if you can think of any more uses for this amazing number.
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